Science.gov

Sample records for infrasound source observed

  1. Infrasound Observations from Lightning

    NASA Astrophysics Data System (ADS)

    Arechiga, R. O.; Johnson, J. B.; Edens, H. E.; Thomas, R. J.; Jones, K. R.

    2008-12-01

    To provide additional insight into the nature of lightning, we have investigated its infrasound manifestations. An array of three stations in a triangular configuration, with three sensors each, was deployed during the Summer of 2008 (July 24 to July 28) in the Magdalena mountains of New Mexico, to monitor infrasound (below 20 Hz) sources due to lightning. Hyperbolic formulations of time of arrival (TOA) measurements and interferometric techniques were used to locate lightning sources occurring over and outside the network. A comparative analysis of simultaneous Lightning Mapping Array (LMA) data and infrasound measurements operating in the same area was made. The LMA locates the sources of impulsive RF radiation produced by lightning flashes in three spatial dimensions and time, operating in the 60 - 66 MHz television band. The comparison showed strong evidence that lightning does produce infrasound. This work is a continuation of the study of the frequency spectrum of thunder conducted by Holmes et al., who reported measurements of infrasound frequencies. The integration of infrasound measurements with RF source localization by the LMA shows great potential for improved understanding of lightning processes.

  2. Analysis of Signals from an Unique Ground-Truth Infrasound Source Observed at IMS Station IS26 in Southern Germany

    NASA Astrophysics Data System (ADS)

    Koch, Karl

    2010-05-01

    Quantitative modeling of infrasound signals and development and verification of the corresponding atmospheric propagation models requires the use of well-calibrated sources. Numerous sources have been detected by the currently installed network of about 40 of the final 60 IMS infrasound stations. Besides non-nuclear explosions such as mining and quarry blasts and atmospheric phenomena like auroras, these sources include meteorites, volcanic eruptions and supersonic aircraft including re-entering spacecraft and rocket launches. All these sources of infrasound have one feature in common, in that their source parameters are not precisely known and the quantitative interpretation of the corresponding signals is therefore somewhat ambiguous. A source considered well-calibrated has been identified producing repeated infrasound signals at the IMS infrasound station IS26 in the Bavarian forest. The source results from propulsion tests of the ARIANE-5 rocket's main engine at a testing facility near Heilbronn, southern Germany. The test facility is at a range of 320 km and a backazimuth of ~280° from IS26. Ground-truth information was obtained for nearly 100 tests conducted in a 5-year period. Review of the available data for IS26 revealed that at least 28 of these tests show signals above the background noise level. These signals are verified based on the consistency of various signal parameters, e.g., arrival times, durations, and estimates of propagation characteristics (backazimuth, apparent velocity). Signal levels observed are a factor of 2-8 above the noise and reach values of up to 250 mPa for peak amplitudes, and a factor of 2-3 less for RMS measurements. Furthermore, only tests conducted during the months from October to April produce observable signals, indicating a significant change in infrasound propagation conditions between summer and winter months.

  3. Infrasound Observations from the Source Physics Experiment (Tests 1 and 2) at the Nevada National Security Site

    DTIC Science & Technology

    2012-09-01

    INFRASOUND OBSERVATIONS FROM THE SOURCE PHYSICS EXPERIMENT ( TESTS 1 AND 2) AT THE NEVADA NATIONAL SECURITY SITE Kyle R. Jones1, Rod W. Whitaker2...series of explosions, we have the unique and rare opportunity to study infrasound generated by a well-characterized source from the same borehole ...two explosive tests (SPE-N-1 and SPE-N-2) were successfully conducted on May 3 and October 25, 2011, respectively. SPE-N-1 had a yield of 0.1 tons at

  4. Ten Years of Infrasound Observation in Korea

    NASA Astrophysics Data System (ADS)

    Lee, Hee-Il; Che, Il-Young; Kim, Tae Sung

    2010-05-01

    Over the ten years after the installation of our first seismo-acoustic array station (CHNAR) in September 1999, Korea Institute of Geoscience and Mineral Resources (KIGAM) has been continuously observing infrasound with an infrasound array network, named KIN (Korean Infrasound Network) in Korea. This network consists of seven seismo-acoustic arrays (BRDAR, KMPAR, CHNAR, YAGAR, KSGAR, ULDAR and TJIAR). The aperture size of the smallest array (KMPAR and TJIAR) is about 300m and the largest is about 1.4km. The number of acoustic gauges are between 4 (TJIAR) and 18 (YAGAR), and 1 or 5 seismometers are collocated at the center of the acoustic array. All seismic and infrasonic signals of the arrays are digitized at 40 samples/sec and transmitted to KIGAM in real time. Many interesting infrasound signals associated with different kind of anthropogenic source as well as natural one are detected by KIN. Ten years of seismo-acoustic data are analyzed by using PMCC program, and identified more than five thousand of infrasonic events and catalogued in our infrasound database. This database is used to study characteristics of seasonally dependent propagation of the infrasound wave in local scale, as well as to better understand how atmospheric condition affects the detection ratio at a specific station throughout the year. It also played a valuable role in discriminating the anthropogenic events such as the second nuclear test on 25 May 2009 in North Korea, from natural earthquakes, which is important in estimating the seismicity in Korea.

  5. GT0 Explosion Sources for IMS Infrasound Calibration: Charge Design and Yield Estimation from Near-source Observations

    NASA Astrophysics Data System (ADS)

    Gitterman, Y.; Hofstetter, R.

    2014-03-01

    Three large-scale on-surface explosions were conducted by the Geophysical Institute of Israel (GII) at the Sayarim Military Range, Negev desert, Israel: about 82 tons of strong high explosives in August 2009, and two explosions of about 10 and 100 tons of ANFO explosives in January 2011. It was a collaborative effort between Israel, CTBTO, USA and several European countries, with the main goal to provide fully controlled ground truth (GT0) infrasound sources, monitored by extensive observations, for calibration of International Monitoring System (IMS) infrasound stations in Europe, Middle East and Asia. In all shots, the explosives were assembled like a pyramid/hemisphere on dry desert alluvium, with a complicated explosion design, different from the ideal homogenous hemisphere used in similar experiments in the past. Strong boosters and an upward charge detonation scheme were applied to provide more energy radiated to the atmosphere. Under these conditions the evaluation of the actual explosion yield, an important source parameter, is crucial for the GT0 calibration experiment. Audio-visual, air-shock and acoustic records were utilized for interpretation of observed unique blast effects, and for determination of blast wave parameters suited for yield estimation and the associated relationships. High-pressure gauges were deployed at 100-600 m to record air-blast properties, evaluate the efficiency of the charge design and energy generation, and provide a reliable estimation of the charge yield. The yield estimators, based on empirical scaled relations for well-known basic air-blast parameters—the peak pressure, impulse and positive phase duration, as well as on the crater dimensions and seismic magnitudes, were analyzed. A novel empirical scaled relationship for the little-known secondary shock delay was developed, consistent for broad ranges of ANFO charges and distances, which facilitates using this stable and reliable air-blast parameter as a new potential

  6. Infrasound Generation from the Source Physics Experiments

    NASA Astrophysics Data System (ADS)

    Preston, L. A.; Schramm, K. A.; Jones, K. R.

    2015-12-01

    Understanding the acoustic and infrasound source generation mechanisms from underground explosions is of great importance for usage of this unique data type in non-proliferation activities. One of the purposes of the Source Physics Experiments (SPE), a series of underground explosive shots at the Nevada National Security Site (NNSS), is to gain an improved understanding of the generation and propagation of physical signals, such as seismic and infrasound, from the near to far field. Two of the SPE shots (SPE-1 and SPE-4') were designed to be small "Green's Function" sources with minimal spall or permanent surface deformation. We analyze infrasound data collected from these two shots at distances from ~300 m to ~1 km and frequencies up to 20 Hz. Using weather models based upon actual observations at the times of these sources, including 3-D variations in topography, temperatures, pressures, and winds, we synthesized full waveforms using Sandia's moving media acoustic propagation simulation suite. Several source mechanisms were simulated and compared and contrasted with observed waveforms using full waveform source inversion. We will discuss results of these source inversions including the relative roll of spall from these small explosions. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  7. Integrated video and infrasound observations at Mount Erebus, Antarctica

    NASA Astrophysics Data System (ADS)

    Krzesni, D.; Johnson, J.; Kyle, P. R.

    2012-12-01

    Erebus volcano is ideally suited for infrasound studies because it produces frequent, discrete, short-duration Strombolian eruptions that generate simple, high-amplitude (10^3 - 10^4 Pa-m), high signal-to-noise, acoustic pulses. Some explosions have been recorded by a video camera situated 300 m from the lava lake. Here we analyze the infrasound signal recordings from 256 eruptions, 10 were accompanied by high-quality video. We have developed image processing scripts in MATLAB to measure the explosive expansion of eject in consecutive 30 fps video. An ellipse was fitted to the expanding surface, which begins as an intact bubble and then fragments into radially-projected ballistics. The volume of the magma bubble was estimated in each frame of the video and used to produce a synthetic infrasound wave. We assumed an acoustic monopole point source model where the volumetric acceleration was proportional to the radiated pressure waveform. In a comparison of synthetic and recorded infrasound we find a consistent match in both frequency and amplitude. The synthetic infrasound amplitude is generally greater than the amplitude of the observed infrasound. This suggests some non-linear decay in acoustic energy between the fluid ejection source and the infrasound recording sites. The infrasound signals were also analyzed to determine if a precursory pulse (or shoulder) in the waveforms, was related to distension of an unbroken magma bubble membrane prior to rupture. We examined the pressure slope (at the onset of an eruption) and the scaled asymmetry (of the bimodal pulses), and relate them to the initial magma overburden and source overpressure respectively. For significantly asymmetric infrasound pulses, with large rarefactions compared to initial compression, we speculate that rupture occurs for bubble slugs with very low overpressures.

  8. Observed and predicted performance of the global IMS infrasound network

    NASA Astrophysics Data System (ADS)

    Le Pichon, A.; Ceranna, L.; Landes, M.

    2012-04-01

    The International Monitoring System (IMS) infrasound network is being deployed to monitor compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Global-scale analyses of data recorded by this network indicate that the detection capability exhibits strong spatio-temporal variations. Previous studies estimated radiated acoustic source energy from remote infrasound observations using empirical yield-scaling relations, which account for the along-path stratospheric winds. Although the empirical wind correction reduces the variance in the explosive energy versus pressure relationship, large error remains in the yield estimates. Numerical modeling techniques are now widely employed to investigate the role of different factors describing atmospheric infrasound sources and propagation. Here we develop a theoretical attenuation relation from a large set of numerical simulations using the Parabolic Equation method. This relation accounts for the effects of the source frequency; geometrical spreading and dissipation; and realistic atmospheric specifications on the pressure wave attenuation. Compared with previous studies, the derived attenuation relation incorporates a more realistic physical description of infrasound propagation. By incorporating real ambient noise information at the receivers, we obtain the minimum detectable source amplitude in the frequency band of interest for detecting explosions. Empirical relations between the source spectrum and explosion yield are used to infer detection thresholds in tons of TNT equivalent. In the context of future verification of the CTBT, the obtained attenuation relation provides a more realistic picture of the spatio-temporal variability of the IMS network performance. The attenuation relation could also be used in the design and maintenance of an arbitrary infrasound monitoring network.

  9. Source Inversions of Volcano Infrasound: Mass Outflux and Force System for Transient Explosive Eruptions

    NASA Astrophysics Data System (ADS)

    Kim, K.; Fee, D.; Lees, J. M.; Yokoo, A.; Ruiz, M. C.

    2014-12-01

    Sources of volcano infrasound associated with explosive eruptions are typically modeled assuming an acoustic monopole and/or dipole. While the monopole represents the mass outflux of erupted materials, the dipole represents a force system acting in the source region during eruptions. Therefore, appropriate acoustic source inversions of volcano infrasound data can provide estimates of eruption parameters which are critical to understanding eruption dynamics. Reliability of the source parameters is dominantly controlled by the accuracy of the acoustic Green's functions between the source and receiver positions. Conventional source inversions of volcano infrasound, however, were typically performed using a simplified Green's function obtained in a free space or half space. This may result in intolerable errors in the source parameters, especially when the infrasound waveforms are significantly distorted by volcano topography and/or local atmospheric variability (i.e., layered velocity structure or wind). In this study we present a full waveform inversion technique for volcano infrasound using numerical Green's functions. A full 3-D Finite-Difference Time-Domain (FDTD) method accelerated with GPU is used to compute accurate Green's functions taking into account volcano topography and local atmospheric conditions. The presented method is applied to data recorded at Sakurajima volcano (Japan) and Tungurahua volcano (Ecuador), which provide a large volume of high-quality data recorded by azimuthally well-distributed stations within 2 -- 6 km distance of the volcanoes. We analyze infrasound signals associated with explosive eruptions exhibiting 1) distinct explosion waveforms followed by gas discharges and 2) strong anisotropic radiation patterns, which can be caused by either source directivity or topographic barriers/reflections. Here the role of topography in controlling the infrasound radiation is investigated through numerical modeling, and then the observed

  10. Infrasound Observations of the Massive Landslide at Bingham Canyon Copper Mine

    NASA Astrophysics Data System (ADS)

    Hale, J. M.; Arrowsmith, S.; Burlacu, R.; Hayward, C.; Pankow, K. L.

    2013-12-01

    On 10 April 2013 approximately 55 million m3 of rock collapsed from the northeastern wall of the approximately one-kilometer deep open-pit Bingham Canyon copper mine near Salt Lake City, Utah, generating clear seismic and infrasound signals. The material released in two sudden rock avalanches separated in time by about 1.5 hours. The magnitudes for the two slides were determined to be ML 2.5 and 2.4 and MSW 5.0 and 4.9, respectively. Seismic signals with durations approaching two minutes from both rock avalanches were recorded on stations of the University of Utah (UU) regional seismic network and other networks at distances of ~6 to greater than 400 km. In addition, the first event was recorded on seven UU infrasound arrays at distances of ~13 - 400 km and the second at five infrasound arrays between ~57 and 400 km distance. Comparison of the seismograms from the two slides show differences in the long-period energy. There are also clear differences in the infrasound observations. For example, at the closest array recording both slides, the duration of the infrasound signal for the first slide is much longer than for the second slide. In addition, infrasound attributed to the first rock avalanche resulted in multiple arrival observations at the three most distant arrays, while only one array had multiple arrivals for the latter event. For the five infrasound arrays, with detections for both rock avalanches, we look for signal differences by cataloging duration, amplitude, azimuth, dominant period, correlation coefficients, group and trace velocity. In addition, propagation modeling through ground-to-space (G2S) profiles will be performed to determine if atmospheric differences can account for the varying infrasound observations, and the source of the infrasound signal will be located using the Bayesian Infrasonic Source Location procedure. With a wealth of geophysical data we aim to determine if the seismic and infrasound signals have a common source and if the

  11. Source location of the 19 February 2008 Oregon bolide using seismic networks and infrasound arrays

    NASA Astrophysics Data System (ADS)

    Walker, Kristoffer T.; Hedlin, Michael A. H.; de Groot-Hedlin, Catherine; Vergoz, Julien; Le Pichon, Alexis; Drob, Douglas P.

    2010-12-01

    On 19 February 2008 a bolide traveled across the sky along a southern trajectory ending in a terminal burst above Oregon. The event was well recorded by the USArray, other seismic networks, four infrasound arrays, and several video cameras. We compare the results of locating the burst using these different sensor networks. Specifically, we reverse time migrate acoustic-to-seismic coupled signals recorded by the USArray out to 800 km range to image the source in 2-D space and time. We also apply a grid search over source altitude and time, minimizing the misfit between observed and predicted arrival times using 3-D ray tracing with a high-resolution atmospheric velocity model. Our seismic and video results suggest a point source rather than a line source associated with a hypersonic trajectory. We compare the seismic source locations to those obtained by using different combinations of observed infrasound array signal back azimuths and arrival times. We find that all locations are consistent. However, the seismic location is more accurate than the infrasound locations due to the larger number of seismic sensors, a more favorable seismic source-receiver geometry, and shorter ranges to the seismometers. For the infrasound array locations, correcting for the wind improved the accuracy, but implementing arrival times while increasing the precision reduced the accuracy presumably due to limitations of the source location method and/or atmospheric velocity model. We show that despite known complexities associated with acoustic-to-seismic coupling, aboveground infrasound sources can be located with dense seismic networks with remarkably high accuracy and precision.

  12. Volcano Infrasound

    NASA Astrophysics Data System (ADS)

    Johnson, J. B.; Fee, D.; Matoza, R. S.

    2013-12-01

    Open-vent volcanoes generate prodigious low frequency sound waves that tend to peak in the infrasound (<20 Hz) band. These long wavelength (> ~20 m) atmospheric pressure waves often propagate long distances with low intrinsic attenuation and can be well recorded with a variety of low frequency sensitive microphones. Infrasound records may be used to remotely monitor eruptions, identify active vents or track gravity-driven flows, and/or characterize source processes. Such studies provide information vital for both scientific study and volcano monitoring efforts. This presentation proposes to summarize and standardize some of the terminology used in the still young, yet rapidly growing field of volcano infrasound. Herein we suggest classification of typical infrasound waveform types, which include bimodal pulses, blast (or N-) waves, and a variety of infrasonic tremors (including broadband, harmonic, and monotonic signals). We summarize various metrics, including reduced pressure, intensity, power, and energy, in which infrasound excess pressures are often quantified. We also describe the spectrum of source types and radiation patterns, which are typically responsible for recorded infrasound. Finally we summarize the variety of propagation paths that are common for volcano infrasound radiating to local (<10 km), regional (out to several hundred kilometers), and global distances. The effort to establish common terminology requires community feedback, but is now timely as volcano infrasound studies proliferate and infrasound becomes a standard component of volcano monitoring.

  13. A repeating source of infrasound from the Wells, Nevada earthquake sequence

    SciTech Connect

    Arrowsmith, Stephen J.; Whitaker, Rod; Randall, George; Burlacu, Relu

    2009-01-01

    The Wells, Nevada earthquake of February 21, 2008, generated a complex seismoacoustic wakefield. In addition to epicentral infrasound, the earthquake triggered a secondary source of infrasound, which was also initiated by subsequent aftershocks. By applying simple constraints on the propagation of seismic and infrasound waves, we show that the secondary source is an isolated peak that appears to efficiently generate infrasound through the interaction with seismic surface waves. By measuring peak-to-peak amplitudes of epicentral and secondary arrivals and correcting them for the effects of distance and winds, we find that epicentral arrivals lit with empirical relationships of Mutschlecner and Whitaker (2005) and Le Pichon et al. (2006), which form the basis for a proposed infrasound discriminant (Anderson et al., Pers. Comm.). In contrast, the secondary arrivals are much higher in amplitude, highlighting the importance of being able to separate epicentral and secondary arrivals for infrasonic event discrimination.

  14. Infrasound, Its Sources and Its Effects on Man

    DTIC Science & Technology

    1976-05-01

    that are harmful or even audible to man. Thus infrasound exposure is not one of mankinds more press- ling environmental problems. g SECURITY...unwarranted conclusions infrasound is not one of mankiuds more pressing about the effects of infrasound on man. The environmental problems. upper frequency... health and welfare is via all those many factors above 20 Hz could be eliminated, 1 baiieve there that make up the annoyance response. Now it is would be

  15. Remote infrasound monitoring of Mount Etna: Observed and predicted network detection capability

    NASA Astrophysics Data System (ADS)

    Tailpied, Dorianne; Le Pichon, Alexis; Marchetti, Emanuele; Ripepe, Maurizio; Kallel, Mohamed; Ceranna, Lars

    2013-04-01

    Volcanic eruptions are unique and valuable calibrating sources of infrasonic waves worldwide detected by the International Monitoring System (IMS) of the Comprehensive nuclear Test Ban Treaty Organization (CTBTO) and other experimental stations. Building a comprehensive database of volcanic signals is likely to help the scientific community to better characterize eruptive sequences and may help to prevent eruption disasters while on a longer term mitigate the impact of ash clouds on aviation. In this study, we assess the detection capability of the existing infrasound network to remotely detect the eruptive activity of Mount Etna with a high level of confidence, and predict the performance of the future ARISE infrastructure network (Atmospheric dynamics InfraStructure in Europe). This well-instrumented volcano offers a unique opportunity to validate attenuation models using multiyear near-and-far field recordings. The seasonal trend in the number of detections of Etna at the IS48 IMS station (Tunisia) is correlated to fine temporal fluctuations of the stratospheric waveguide structure. The modeling results are consistent with the observed detection capability of the existing network. In summer, during the downwind season, a minimum detectable amplitude of ~10 Pa at a reference distance of 1 km from the source is predicted. In winter, when upwind propagation occurs, detection thresholds increase up to ~100 Pa. When adding four experimental arrays to the existing IMS network, thresholds decrease down to ~20 Pa in winter. The simulation results provide here a realistic description of long-range infrasound propagation and allow predicting fine temporal fluctuations in the European infrasound network performance with potential application for civil aviation safety.

  16. Infrasound and SO2 Observations of the 2011 Explosive Eruption of Nabro Volcano, Eritrea

    NASA Astrophysics Data System (ADS)

    Fee, D.; Carn, S. A.; Prata, F.

    2011-12-01

    Nabro volcano, Eritrea erupted explosively on 12 June 2011 and produced near continuous emissions and infrasound until mid-July. The eruption disrupted air traffic and severely affected communities in the region. Although the eruption was relatively ash-poor, it produced significant SO2 emissions, including: 1) the highest SO2 column ever retrieved from space (3700 DU), 2) >1.3 Tg SO2 mass on 13 June, and 3) >2 Tg of SO2 for the entire eruption, one of the largest eruptive SO2 masses produced since the 1991 eruption of Mt. Pinatubo. Peak emissions reached well into the stratosphere (~19 km). Although the 12 June eruption was preceded by significant seismicity and clearly detected by satellite sensors, Nabro volcano is an understudied volcano that lies in a remote region with little ground-based monitoring. The Nabro eruption also produced significant infrasound signals that were recorded by two infrasound arrays: I19DJ (Djibouti, 264 km) and I32KE (Kenya, 1708 km). The I19DJ infrasound array detected the eruption with high signal-noise and provides the most detailed eruption chronology available, including eruption onset, duration, changes in intensity, etc. As seen in numerous other studies, sustained low frequency infrasound from Nabro is coincident with high-altitude emissions. Unexpectedly, the eruption also produced hundreds of short-duration, impulsive explosion signals, in addition to the sustained infrasonic jetting signals more typical of subplinian-plinian eruptions. These explosions are variable in amplitude, duration, and often cluster in groups. Here we present: 1) additional analyses, classification, and source estimation of the explosions, 2) infrasound propagation modeling to determine acoustic travel times and propagation paths, 3) detection and characterization of the SO2 emissions using the Ozone Monitoring Instrument (OMI) and Spin Enhanced Visible and Infra-Red Instrument (SEVIRI), and 4) a comparison between the relative infrasound energy and

  17. Local and remote infrasound from explosive volcanism

    NASA Astrophysics Data System (ADS)

    Matoza, R. S.; Fee, D.; LE Pichon, A.

    2014-12-01

    Explosive volcanic eruptions can inject large volumes of ash into heavily travelled air corridors and thus pose a significant societal and economic hazard. In remote volcanic regions, satellite data are sometimes the only technology available to observe volcanic eruptions and constrain ash-release parameters for aviation safety. Infrasound (acoustic waves ~0.01-20 Hz) data fill this critical observational gap, providing ground-based data for remote volcanic eruptions. Explosive volcanic eruptions are among the most powerful sources of infrasound observed on earth, with recordings routinely made at ranges of hundreds to thousands of kilometers. Advances in infrasound technology and the efficient propagation of infrasound in the atmosphere therefore greatly enhance our ability to monitor volcanoes in remote regions such as the North Pacific Ocean. Infrasound data can be exploited to detect, locate, and provide detailed chronologies of the timing of explosive volcanic eruptions for use in ash transport and dispersal models. We highlight results from case studies of multiple eruptions recorded by the International Monitoring System and dedicated regional infrasound networks (2008 Kasatochi, Alaska, USA; 2008 Okmok, Alaska, USA; 2009 Sarychev Peak, Kuriles, Russian Federation; 2010 Eyjafjallajökull, Icleand) and show how infrasound is currently used in volcano monitoring. We also present progress towards characterizing and modeling the variability in source mechanisms of infrasound from explosive eruptions using dedicated local infrasound field deployments at volcanoes Karymsky, Russian Federation and Sakurajima, Japan.

  18. First observations of sprites in the eastern Mediterranean using the Israeli infrasound network

    NASA Astrophysics Data System (ADS)

    Applbaum, David; Price, Colin; Ben Horin, Yochai; Yair, Yoav

    2014-05-01

    As outlined by Farges et al (2005) as part of the Sprite2003 campaign in Europe, sprites at close range (less than a few hundred km) exhibit a unique signal in infrasound. This signal consists of an 'inverted chirp,' lasting up to several minutes and in which the higher frequencies arrive prior to the lower frequencies. The ILAN (Imaging of Lightning and Nocturnal Flashes) science team at Tel Aviv University maintains a database of optically observed sprites occurring within a few hundred kilometers of the Mediterranean coast of Israel. Using the observed azimuths of these sprites' locations with respect to the detectors, combined with an acoustic propagation model and the observed delays associated with propagation of the signals between the sprites and the infrasound arrays, we present here observations of several sprites that are consistent with the observations made by Farges et al. These constitute the first observations of sprites made using the Israeli infrasound network.

  19. Modeling propagation of infrasound signals observed by a dense seismic network.

    PubMed

    Chunchuzov, I; Kulichkov, S; Popov, O; Hedlin, M

    2014-01-01

    The long-range propagation of infrasound from a surface explosion with an explosive yield of about 17.6 t TNT that occurred on June 16, 2008 at the Utah Test and Training Range (UTTR) in the western United States is simulated using an atmospheric model that includes fine-scale layered structure of the wind velocity and temperature fields. Synthetic signal parameters (waveforms, amplitudes, and travel times) are calculated using parabolic equation and ray-tracing methods for a number of ranges between 100 and 800 km from the source. The simulation shows the evolution of several branches of stratospheric and thermospheric signals with increasing range from the source. Infrasound signals calculated using a G2S (ground-to-space) atmospheric model perturbed by small-scale layered wind velocity and temperature fluctuations are shown to agree well with recordings made by the dense High Lava Plains seismic network located at an azimuth of 300° from UTTR. The waveforms of calculated infrasound arrivals are compared with those of seismic recordings. This study illustrates the utility of dense seismic networks for mapping an infrasound field with high spatial resolution. The parabolic equation calculations capture both the effect of scattering of infrasound into geometric acoustic shadow zones and significant temporal broadening of the arrivals.

  20. West Texas array experiment: Noise and source characterization of short-range infrasound and acoustic signals, along with lab and field evaluation of Intermountain Laboratories infrasound microphones

    NASA Astrophysics Data System (ADS)

    Fisher, Aileen

    The term infrasound describes atmospheric sound waves with frequencies below 20 Hz, while acoustics are classified within the audible range of 20 Hz to 20 kHz. Infrasound and acoustic monitoring in the scientific community is hampered by low signal-to-noise ratios and a limited number of studies on regional and short-range noise and source characterization. The JASON Report (2005) suggests the infrasound community focus on more broad-frequency, observational studies within a tactical distance of 10 km. In keeping with that recommendation, this paper presents a study of regional and short-range atmospheric acoustic and infrasonic noise characterization, at a desert site in West Texas, covering a broad frequency range of 0.2 to 100 Hz. To spatially sample the band, a large number of infrasound gauges was needed. A laboratory instrument analysis is presented of the set of low-cost infrasound sensors used in this study, manufactured by Inter-Mountain Laboratories (IML). Analysis includes spectra, transfer functions and coherences to assess the stability and range of the gauges, and complements additional instrument testing by Sandia National Laboratories. The IMLs documented here have been found reliably coherent from 0.1 to 7 Hz without instrument correction. Corrections were built using corresponding time series from the commercially available and more expensive Chaparral infrasound gauge, so that the corrected IML outputs were able to closely mimic the Chaparral output. Arrays of gauges are needed for atmospheric sound signal processing. Our West Texas experiment consisted of a 1.5 km aperture, 23-gauge infrasound/acoustic array of IMLs, with a compact, 12 m diameter grid-array of rented IMLs at the center. To optimize signal recording, signal-to-noise ratio needs to be quantified with respect to both frequency band and coherence length. The higher-frequency grid array consisted of 25 microphones arranged in a five by five pattern with 3 meter spacing, without

  1. Infrasound Monitoring of the Volcanic Activities of Japanese Volcanoes in Korea

    NASA Astrophysics Data System (ADS)

    Lee, H. I.; Che, I. Y.; Shin, J. S.

    2015-12-01

    Since 1999 when our first infrasound array station(CHNAR) has been installed at Cheolwon, Korea Institute of Geoscience and Mineral Resources(KIGAM) is continuously observing infrasound signals with an infrasound array network, named KIN(Korean Infrasound Network). This network is comprised of eight seismo-acoustic array stations(BRDAR, YPDAR, KMPAR, CHNAR, YAGAR, KSGAR, ULDAR, TJIAR). The aperture size of the smallest array is 300m and the largest is about 1.4km. The number of infrasound sensors are between 4(TJIAR) and 18(YAGAR), and 1~5 seismometers are collocated with infrasound sensors. Many interesting infrasound signals associated with different type of sources, such as blasting, large earthquake, bolide, volcanic explosion are detected by KIN in the past 15 years. We have analyzed the infrasound signals possibly associated with the japanese volcanic explosions with reference to volcanic activity report published by Japanese Meteorological Agency. Analysis results of many events, for example, Asama volcano explosion in 2004 and Shinmoe volcano in 2011, are well matched with the official report. In some cases, however, corresponding infrasound signals are not identified. By comparison of the infrasound signals from different volcanoes, we also found that the characteristics of signals are distinguishing. It may imply that the specific volcano has its own unique fingerprint in terms of infrasound signal. It might be investigated by long-term infrasound monitoring for a specific volcano as a ground truth generating repetitive infrasound signal.

  2. Modelling infrasound signal generation from two underground explosions at the Source Physics Experiment using the Rayleigh integral

    NASA Astrophysics Data System (ADS)

    Jones, Kyle R.; Whitaker, Rodney W.; Arrowsmith, Stephen J.

    2015-02-01

    We use the Rayleigh integral (RI) as an approximation to the Helmholtz-Kirchoff integral to model infrasound generation and propagation from underground chemical explosions at distances of 250 m out to 5 km as part of the Source Physics Experiment (SPE). Using a sparse network of surface accelerometers installed above ground zero, we are able to accurately create synthetic acoustic waveforms and compare them to the observed data. Although the underground explosive sources were designed to be symmetric, the resulting seismic wave at the surface shows an asymmetric propagation pattern that is stronger to the northeast of the borehole. This asymmetric bias may be attributed to the subsurface geology and faulting of the area and is observed in the acoustic waveforms. We compare observed and modelled results from two of the underground SPE tests with a sensitivity study to evaluate the asymmetry observed in the data. This work shows that it is possible to model infrasound signals from underground explosive sources using the RI and that asymmetries observed in the data can be modelled with this technique.

  3. Magnetic infrasound sensor

    DOEpatents

    Mueller, Fred M.; Bronisz, Lawrence; Grube, Holger; Nelson, David C.; Mace, Jonathan L.

    2006-11-14

    A magnetic infrasound sensor is produced by constraining a permanent magnet inside a magnetic potential well above the surface of superconducting material. The magnetic infrasound sensor measures the position or movement of the permanent magnet within the magnetic potential well, and interprets the measurements. Infrasound sources can be located and characterized by combining the measurements from one or more infrasound sensors. The magnetic infrasound sensor can be tuned to match infrasound source types, resulting in better signal-to-noise ratio. The present invention can operate in frequency modulation mode to improve sensitivity and signal-to-noise ratio. In an alternate construction, the superconductor can be levitated over a magnet or magnets. The system can also be driven, so that time resolved perturbations are sensed, resulting in a frequency modulation version with improved sensitivity and signal-to-noise ratio.

  4. Infrasound research of volcanic eruptions

    NASA Astrophysics Data System (ADS)

    Marchetti, Emanuele; Ripepe, Maurizio

    2016-04-01

    Volcanic eruptions are efficient sources of infrasound produced by the rapid perturbation of the atmosphere by the explosive source. Being able to propagate up to large distances from the source, infrasonic waves from major (VEI 4 or larger) volcanic eruptions have been recorded for many decades with analogue micro-barometers at large regional distances. In late 1980s, near-field observations became progressively more common and started to have direct impact on the understanding and modeling of explosive source dynamics, to eventually play a primary role in volcano research. Nowadays, infrasound observation from a large variety of volcanic eruptions, spanning from VEI 0 to VEI 5 events, has shown a dramatic variability in terms of signature, excess pressure and frequency content of radiated infrasound and has been used to infer complex eruptive source mechanisms for the different kinds of events. Improved processing capability and sensors has allowed unprecedented precise locations of the explosive source and is progressively increasing the possibility to monitor volcanoes from distant records. Very broadband infrasound observations is also showing the relation between volcanic eruptions and the atmosphere, with the eruptive mass injection in the atmosphere triggering acoustic-gravity waves which eventually might control the ash dispersal and fallout.

  5. Infrasound from volcanic rockfalls

    NASA Astrophysics Data System (ADS)

    Johnson, Jeffrey B.; Ronan, Timothy J.

    2015-12-01

    Proximal infrasound arrays can robustly track rapidly moving gravity-driven mass wasting, which occurs commonly at erupting volcanoes. This study reports on detection, localization, and quantification of frequent small rockfalls and infrequent pyroclastic density currents descending the southeast flanks of Santiaguito's active Caliente Dome in January of 2014. Such activities are identified as moving sources, which descend several hundred meters at bulk flow speeds of up to ~10 m/s, which is considerably slower than the descent velocity of individual blocks. Infrasound rockfall signal character is readily distinguishable from explosion infrasound, which is manifested by a relatively fixed location source with lower frequency content. In contrast, the rockfalls of Santiaguito possess higher frequencies dominated by 7.5 to 20 Hz energy. During our observation periods typical rockfall signals occurred ~10 times per hour and lasted tens of seconds or more. Array beamforming permitted detection of rockfall transients with amplitudes of only a few tens of millipascals that would be impossible to distinguish from noise using a single sensor. Conjoint time-synchronized video is used to corroborate location and to characterize various gravity-driven events.

  6. Station characteristics of the Singapore Infrasound Array

    NASA Astrophysics Data System (ADS)

    Perttu, Anna; Taisne, Benoit; Caudron, Corentin; Garces, Milton; Avila Encillo, Jeffrey; Ildefonso, Sorvigenaleon

    2016-04-01

    Singapore, located in Southeast Asia, presents an ideal location for an additional regional infrasound array, with diverse persistent natural and anthropogenic regional infrasound sources, including ~750 active or potentially active volcanoes within 4,000 kilometers. Previous studies have focused on theoretical and calculated regional signal detection capability improvement with the addition of a Singapore array. The Earth Observatory of Singapore installed a five element infrasound array in northcentral Singapore in late 2014, and this station began consistent real-time data transmission mid-2015. The Singapore array uses MB2005s microbarometers and Nanometrics Taurus digitizers. Automated array processing is carried out with the INFrasonic EneRgy Nth Octave (INFERNO) energy estimation suite, and PMCC (Progressive MultiChannel Correlation). The addition of the Singapore infrasound array to the existing International Monitoring System (IMS) infrasound stations in the region has increased regional infrasound detection capability, which is illustrated with the preliminary work on three observed meteor events of various sizes in late 2015. A meteor observed in Bangkok, Thailand in early September, 2015 was picked up by the CTBTO, however, another meteor observed in Bangkok in November was only recorded on the Singapore array. Additionally, another meteor observed over Sumatra was only recorded by one IMS station and the Singapore array. This study uses array processing and Power Spectral Density results for both the Singapore and publicly available regional IMS stations to examine station characteristics and detection capability of the Singapore array in the context of the regional IMS network.

  7. IDC Infrasound technology development

    NASA Astrophysics Data System (ADS)

    Mialle, P.; Brown, D. J.; Le Bras, R.; Charbit, M. J. C.; Given, J. W.

    2014-12-01

    The first atmospheric event built only from infrasound arrivals was reported in the Reviewed Event Bulletin (REB) of the International Data Centre (IDC) of the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO) in 2003. In the last decade, 48 infrasound stations from the International Monitoring System (IMS) have been installed and are transmitting data to the IDC. The infrasound component of the IMS daily registers infragenic signals originating from various sources such as volcanic eruptions, earthquakes, microbaroms, meteorites entering the atmosphere and accidental explosions. The IDC routinely and automatically processes infrasound data reviewed by interactive analysis; the detected and located events are then included in the IDC products. The IDC advances its methods and continuously improves its automatic system for the infrasound technology. The IDC focuses on enhancing the automatic system for the identification of valid signals and the optimization of the network detection threshold by identifying ways to refine signal characterization methodology and association criteria. An objective of this study is to reduce the number of associated infrasound arrivals that are rejected from the automatic bulletins when generating the reviewed event bulletins. A number of ongoing projects at the IDC will be presented, such as: - improving the detection accuracy at the station processing stage by enhancing the infrasound signal detector DFX-PMCC (Detection and Feature eXtraction - Progressive Multi-Channel Correlation) and by evaluating the performances of detection software. - separating infrasound data from other waveform technologies at the automatic network processing stage for technology development and for preparing the implementation of next generation of waveform association algorithm. Infrasound rules in Global Association (GA) are revisited to pursue a lower ratio of false alarms. - determining station noise for IMS infrasound, seismic and

  8. Improved Bayesian Infrasonic Source Localization for regional infrasound

    DOE PAGES

    Blom, Philip S.; Marcillo, Omar; Arrowsmith, Stephen J.

    2015-10-20

    The Bayesian Infrasonic Source Localization (BISL) methodology is examined and simplified providing a generalized method of estimating the source location and time for an infrasonic event and the mathematical framework is used therein. The likelihood function describing an infrasonic detection used in BISL has been redefined to include the von Mises distribution developed in directional statistics and propagation-based, physically derived celerity-range and azimuth deviation models. Frameworks for constructing propagation-based celerity-range and azimuth deviation statistics are presented to demonstrate how stochastic propagation modelling methods can be used to improve the precision and accuracy of the posterior probability density function describing themore » source localization. Infrasonic signals recorded at a number of arrays in the western United States produced by rocket motor detonations at the Utah Test and Training Range are used to demonstrate the application of the new mathematical framework and to quantify the improvement obtained by using the stochastic propagation modelling methods. Moreover, using propagation-based priors, the spatial and temporal confidence bounds of the source decreased by more than 40 per cent in all cases and by as much as 80 per cent in one case. Further, the accuracy of the estimates remained high, keeping the ground truth within the 99 per cent confidence bounds for all cases.« less

  9. Improved Bayesian Infrasonic Source Localization for regional infrasound

    SciTech Connect

    Blom, Philip S.; Marcillo, Omar; Arrowsmith, Stephen J.

    2015-10-20

    The Bayesian Infrasonic Source Localization (BISL) methodology is examined and simplified providing a generalized method of estimating the source location and time for an infrasonic event and the mathematical framework is used therein. The likelihood function describing an infrasonic detection used in BISL has been redefined to include the von Mises distribution developed in directional statistics and propagation-based, physically derived celerity-range and azimuth deviation models. Frameworks for constructing propagation-based celerity-range and azimuth deviation statistics are presented to demonstrate how stochastic propagation modelling methods can be used to improve the precision and accuracy of the posterior probability density function describing the source localization. Infrasonic signals recorded at a number of arrays in the western United States produced by rocket motor detonations at the Utah Test and Training Range are used to demonstrate the application of the new mathematical framework and to quantify the improvement obtained by using the stochastic propagation modelling methods. Moreover, using propagation-based priors, the spatial and temporal confidence bounds of the source decreased by more than 40 per cent in all cases and by as much as 80 per cent in one case. Further, the accuracy of the estimates remained high, keeping the ground truth within the 99 per cent confidence bounds for all cases.

  10. Using physics-based priors in a Bayesian algorithm to enhance infrasound source location

    NASA Astrophysics Data System (ADS)

    Marcillo, Omar; Arrowsmith, Stephen; Whitaker, Rod; Anderson, Dale; Nippress, Alexandra; Green, David N.; Drob, Douglas

    2014-01-01

    We show improvements in the precision of the Bayesian infrasound source localization (BISL) method by incorporating semi-empirical model-based prior information. Given a set of backazimuths and delay times at ≥2 arrays, BISL scans a parameter space (that comprises the horizontal coordinates, celerity and origin time) for the most likely solution. A key element of BISL is its flexibility; the method allows the incorporation of prior information to constrain the parameters. Our research focuses on generating model-based propagation catalogues using a comprehensive set of atmospheric scenarios, extracting celerity distributions based on range and azimuth from the catalogues and using these distributions as prior probability density functions to enhance the location solution from BISL. To illustrate the improvements in source location precision, we compare the BISL results computed using uniform celerity distribution priors with those using enhanced priors; as applied to: (1) a set of events recorded across a regional network and (2) a large accidental chemical explosion recorded by six infrasound arrays in Eurasia. Finally, we discuss efforts to improve the numerical implementation of BISL by expanding the parameter space to cover a richer set of parameters that can include station-specific celerity distributions.

  11. Implications from Meteoric and Volcanic Infrasound Measured in the Netherlands

    NASA Astrophysics Data System (ADS)

    Evers, L.

    2003-12-01

    Infrasound observations started in the Netherlands in 1986. Since then, several array configurations and instruments have been developed, tested and made operational. Currently, three infrasound arrays are continuously measuring infrasound with in-house developed microbarometers. The array apertures vary from 30 to 1500 meters and the number of instruments from 6 to 16 microbarometers. The inter-array distance ranges from 50 up to 150 km. This dense network of infrasound arrays is used to distinguish between earthquakes and sources in the atmosphere. Sonic booms, for example, can be experienced in the same manner as small (gas induced) earthquakes. Furthermore, Comprehensive Nuclear-Test-Ban Treaty (CTBT) related research is done. Meteors are one of the few natural impulsive sources generating energy in kT TNT equivalent range. Therefore, the study of meteors is essential to the CTBT where infrasound is applied as monitoring technique. Studies of meteors in the Netherlands have shown the capability of infrasound to trace a meteor through the stratosphere. The propagation of infrasound is in first order dependent on the wind and temperature structure of the atmosphere. The meteor's path could be reconstructed by using ECMWF atmospheric models for wind and temperature. The results were compared to visual observations, confirming the location, direction and reported origin time. The accuracy of the localization mainly depends on the applied atmospheric model and array resolution. Successfully applying infrasound depends on the array configuration that should be based on the -frequency depend- spatial coherence of the signals of interest. The array aperture and inter-element distance will play a decisive role in detecting low signal-to-noise ratios. This is shown by results from studies on volcanic infrasound from Mt. Etna (Italy) detected in the Netherlands. Sub-array processing on the 16 element array revealed an increased detectability of infrasound for small

  12. Infrasound Monitoring of Natural Hazards

    NASA Astrophysics Data System (ADS)

    Arrowsmith, S.

    2015-12-01

    Infrasound is generated by a wide variety of energetic natural and anthropogenic phenomena that originate in the solid earth, ocean, and atmosphere. Because the absorption of infrasound is low, it can propagate long distances through atmospheric waveguides, making it a valuable tool for remote monitoring of hazards. Advances in using infrasound for monitoring energetic events in the solid earth, oceans, and atmosphere are being driven by the wealth of new datasets in addition to advances in modeling source and propagation physics. This presentation provides an overview of recent advances in infrasound monitoring of natural hazards, focusing on selected hazards in the earth (earthquakes and volcanoes), ocean (tsunamis), and atmosphere (meteoroids).

  13. Infrasound signals from the underground nuclear explosions of North Korea

    NASA Astrophysics Data System (ADS)

    Che, Il-Young; Park, Junghyun; Kim, Inho; Kim, Tae Sung; Lee, Hee-Il

    2014-07-01

    We investigated the infrasound signals from seismic ground motions induced by North Korea's underground nuclear explosions, including the recent third explosion on 2013 February 12. For the third explosion, the epicentral infrasound signals were detected not only by three infrasound network stations (KSGAR, ULDAR and YAGAR) in South Korea but also by two nearby International Monitoring System infrasound stations, IS45 and IS30. The detectability of the signals was limited at stations located on the relatively east side of the epicentre, with large azimuth deviations due to very favourable atmospheric conditions for eastward propagation at stratospheric height in 2013. The stratospheric wind direction was the reverse of that when the second explosion was conducted in 2009 May. The source location of the epicentral infrasound with wave parameters determined at the multiple stations has an offset by about 16.6 km from the reference seismic location. It was possible to determine the infrasonic location with moderate accuracy by the correction of the azimuth deviation due to the eastward winds in the stratosphere. In addition to the epicentral infrasonic signals, diffracted infrasound signals were observed from the second underground nuclear explosion in 2009. The exceptional detectability of the diffracted infrasound was a consequence of the temporal formation of a thin atmospheric inversion layer over the ocean surface when the event occurred.

  14. Infrasound tremor from bubble burst eruptions in the viscous shallow crater lake of White Island, New Zealand, and its implications for interpreting volcanic source processes

    NASA Astrophysics Data System (ADS)

    Jolly, Arthur; Kennedy, Ben; Edwards, Matt; Jousset, Philippe; Scheu, Bettina

    2016-11-01

    White Island volcano, New Zealand, produced two periods (January-February and July 2013) of episodic and persistent eruptions through a viscous shallow mud/sulphur pool. The eruptions included an initial hemispherical bubble burst, which was intermittently followed by an up-channel gas jet, and finally a late stage heaving of a mud/sulphur/water suspension. The late stage heave was systematically directed south-eastward as far as 30-40 m from the vent. The associated infrasound time-series included harmonic tremor on permanent stations WIZ and WSRZ. Detailed inspection showed that the tremor was composed of numerous discrete double pulse events without a strong periodic event repetition. The first pulse had highly similar waveforms event-to-event and a notable distortion of the waveform period between the two infrasound stations located on opposites sides from the directed eruption source. The second pulse occurred about 1.5-2.5 s later and was weakly observed on station WSRZ. Where the video can be rigorously linked to the double pulse infrasound signals we interpret aspects of the distinctive eruptive regimes. For this case, the regime dynamics are driven by the propagation of numerous discrete gas slugs though the shallow viscous muddy crater lake, each generating a distinct bubble burst with subsequent eruption heave and associated double pulse infrasound events. The double pulse events are the source of the persistent harmonic tremor having fundamental and overtone spectral frequencies but are not interpreted as related to cavity resonance or a repetitious comb function. Instead the activity is produced by a single event producing a specific two pulse source time function. The observed distortion in the first pulse wave period at WIZ and WSRZ may be ascribed to a Doppler shift associated with the directivity observed in the initial jet/heave eruption process. We surmise that double pulse source dynamics and directivity effects may be generically extended to

  15. Infrasound Studies at the USArray (Invited)

    NASA Astrophysics Data System (ADS)

    de Groot-Hedlin, C. D.

    2013-12-01

    Many surface and atmospheric sources, both natural and anthropogenic, have generated infrasound signals that have been recorded on USArray transportable array (TA) seismometers at ranges up to thousands of kilometers. Such sources, including surface explosions, large bolides, mining events, and a space shuttle, have contributed to an understanding of infrasound propagation. We show examples of several atmospheric sources recorded at the TA. We first used USArray data to investigate infrasound signals from the space shuttle 'Atlantis'. Inclement weather in Florida forced the shuttle to land at Edwards Air Force Base in southern California on June 22, 2007, passing near three infrasound stations and several hundred seismic stations in northern Mexico, southern California, and Nevada. The high signal-to-noise ratio, broad receiver coverage, and Atlantis' positional information allowed us to test infrasound propagation modeling capabilities through the atmosphere to hundreds of kilometers range from the shuttle's path. Shadow zones and arrival times were predicted by tracing rays launched at right angles to the conical shock front surrounding the shuttle through a standard climatological model as well as a global ground to space model. Both models predict alternating regions of high and low ensonification to the NW, in line with observations. However, infrasound energy was detected tens of kilometers beyond the predicted zones of ensonification, possibly due to uncertainties in stratospheric wind speeds. The models also predict increasing waveform complexity with increasing distance, in line with observations. Several hundreds of broadband seismic stations in the U.S. Pacific Northwest recorded acoustic to seismic coupled signals from a large meteor that entered the atmosphere above northeastern Oregon on 19 February 2008. The travel times of the first arriving energy are consistent with a terminal explosion source model, suggesting that the large size of the explosion

  16. An operational approach for infrasound multi-array processing

    NASA Astrophysics Data System (ADS)

    Vergoz, J.; Le Pichon, A.; Herry, P.; Blanc, E.

    2009-04-01

    The infrasound network of the International Monitoring Network (IMS) of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) is currently not fully established. However, it has demonstrated its capability for detecting and locating infrasonic sources like meteorites as well as volcanic eruptions on a global scale. Unfortunately, such ground truth events are rare. Therefore, regions with dense infrasound networks have to be considered in order to test and calibrate detection and location procedures (Le Pichon. et al. 2008, J. Geophys. Res., 113, D12115, doi:10.1029/2007JD009509). In Central Europe, several years of continuous infrasound recordings are available for many infrasound arrays, where not all of them are part of the IMS. Infrasound waveforms are routinely processed in the 0.1 to 4 Hz frequency band using PMCC as a real-time detector. After applying a categorization procedure to remove detections associated with environmental noise, a blind fusion provides a list of events to be reviewed by the analyst. In order to check the geophysical consistency of the located events, an interactive tool has been developed. All results of the automatic processing are presented along with a realistic estimate of the network detection capability which incorporates near-real time atmospheric updates. Among the dominant acoustic sources of human origin, peaks in the geographical distribution of infrasound events correspond well with seismically active regions where operational mines have been identified. With the increasing number of IMS and regional cluster infrasound arrays deployed around the globe, conducting consistent analyses on a routine-basis provides an extensive database for discriminating between natural and artificial acoustic sources. Continuing such studies may also help quantifying relationships between infrasonic observables and atmospheric specification problems, thus opening new fields for investigations into inverse problems.

  17. Tactical Infrasound

    DTIC Science & Technology

    2005-05-01

    ambient pressure field, including sensor- induced turbulence, "* Detector artifacts, such as thermal and seismic feedthrough, "* Sound noise, including wind...suggestions that might provide a near-term enhancement of the effectiveness of a tactical infrasound system into Recommendation #1. The other sug- gestions

  18. Study of IDC infrasound REB solutions using Egyptian National Seismic Network data

    NASA Astrophysics Data System (ADS)

    Ali, Sherif M.; Polich, Paul

    2015-04-01

    Infrasound is one of three waveform technologies which are part of the Comprehensive Nuclear Test Ban Treaty (CTBT) verification regime. The International Monitoring System (IMS) of the CTBT consists of 337 monitoring stations and laboratories world-wide. These facilities include 45 infrasound stations, installed world-wide and transmitting data to the International Data Centre (IDC). Since early 2010, the IDC began routine automatic and interactive processing of infrasound data; the detected and located events are systematically included in the Reviewed Event Bulletin (REB). Infrasound events are frequently characterized by a small number of infrasound phase associations. This poses a challenge to obtaining high-confidence event solutions during routine processing of infrasound data. This study focuses on six infragenic events from the REB, occurring between January 2011 and December 2014, which were thoroughly analyzed at the IDC. The selected events were characteristically seismo-acoustic, and corroborated by seismic recordings of the Egyptian National Seismic Network (ENSN) operated by the National Research Institute of Astronomy and Geophysics (NRIAG). Utilizing this additional local network data of ENSN enables sharper assessment of the IDC published event solutions. Notably, the events were recorded within Egypt and regional surroundings where infrasound waves were generated. The events were detected by IMS infrasound stations located up to 7000 kilometers away. Additional analyses, beyond the six infragenic events from the REB, will also consider some valid infragenic events that fall short of stringent REB Event Definition Criteria. The events will primarily consist of two defining stations with lower-confidence event solutions. The selected events, when confirmed by the seismic observations at ENSN, provide a unique dataset for evaluating IDC infrasound event solutions. Further objectives of the study seek to measure the performance of the IMS network for

  19. Long-range infrasound monitoring of eruptive volcanoes.

    NASA Astrophysics Data System (ADS)

    Marchetti, Emanuele; Innocenti, Lorenzo; Ulivieri, Giacomo; Lacanna, Giorgio; Ripepe, Maurizio

    2016-04-01

    The efficient long-range propagation in the atmosphere makes infrasound of active volcanoes extremely promising and opens new perspectives for volcano monitoring at large scale. In favourable propagation conditions, long-range infrasound observations can be used to track the occurrence and the duration of volcanic eruptions also at remote non-monitored volcanoes, but its potential to infer volcanic eruptive source term is still debated. We present results of comparing five years of infrasound of eruptive activity at Mt.Etna volcano (Italy) recorded both at local (~5 km) and at regional distances (~600 km) from the source. Infrasound of lava fountains at Etna volcano, occurring in between 2010 and 2015, are analysed in terms of the local and regional wavefield record, and by comparing to all available volcanic source terms (i.e. plume height and mass eruption rates). Besides, the potential of near real-time notification of ongoing volcanic activity at Etna volcano at a regional scale is investigated. In particular we show how long range infrasound, in the case of Etna volcano, can be used to promptly deliver eruption notification and reliability is constrained by the results of the local array. This work is performed in the framework of the H2020 ARISE2 project funded by the EU in the period 2015-2018.

  20. Characterization of volcanic activity using observations of infrasound, volcanic emissions, and thermal imagery at Karymsky Volcano, Kamchatka, Russia

    NASA Astrophysics Data System (ADS)

    Lopez, T.; Fee, D.; Prata, F.

    2012-04-01

    Karymsky Volcano is one of the most active and dynamic volcanoes in Kamchatka, with activity ranging from vigorous degassing, frequent ash emissions, and apparent vent sealing, all punctuated by daily to weekly explosive magmatic eruptions. Recent studies have highlighted the strengths in using complementary infrasound measurements and remote volcanic emission measurements to characterize volcanic activity, with the potential to discriminate emission-type, approximate ash-cloud height, and estimate SO2 emission mass. Here we use coincident measurements of infrasound, SO2, ash, and thermal radiation collected over a ten day period at Karymsky Volcano in August 2011 to characterize the observed activity and elucidate vent processes. The ultimate goal of this project is to enable different types of volcanic activity to be identified using only infrasound data, which would significantly improve our ability to continuously monitor remote volcanoes. Four types of activity were observed. Type 1 activity is characterized by discrete ash emissions occurring every 1 - 5 minutes that either jet or roil out of the vent, by plumes from 500 - 1500 m (above vent) altitudes, and by impulsive infrasonic onsets. Type 2 activity is characterized by periodic pulses of gas emission, little or no ash, low altitude (100 - 200 m) plumes, and strong audible jetting or roaring. Type 3 activity is characterized by sustained emissions of ash and gas, with multiple pulses lasting from ~1 - 3 minutes, and by plumes from 300 - 1500 m. Type 4 activity is characterized by periods of relatively long duration (~30 minutes to >1 hour) quiescence, no visible plume and weak SO2 emissions at or near the detection limit, followed by an explosive, magmatic eruption, producing ash-rich plumes to >2000 m, and centimeter to meter (or greater) sized pyroclastic bombs that roll down the flanks of the edifice. Eruption onset is accompanied by high-amplitude infrasound and occasionally visible shock

  1. Use of the IMS infrasound network for global atmospheric studies

    NASA Astrophysics Data System (ADS)

    Blanc, Elisabeth; Le Pichon, Alexis; Ceranna, Lars; Farges, Thomas

    2010-05-01

    The development of the Infrasound International Monitoring System (IMS), used for the verification of the Comprehensive Test Ban Treaty, represents a powerful tool to measure permanently, at a global scale and over large periods of time, the disturbances of the atmosphere. The network is mostly sensitive to infrasound in the range 0.02 to 5 Hz, but it also measures gravity waves at lower frequencies and tidal waves. Measurements with the IMS infrasound network provide both the state of the atmospheric wave guide and of the atmospheric waves which can be used to study the dynamics of the atmosphere. The first way is to study the variability of infrasound from quasi continuous sources such as ocean swells or volcanoes in relation with changes in large scale atmospheric structures. Since infrasound propagate in the stratosphere and mesosphere, atmospheric parameters which affect the infrasound propagation can be investigated from ground measurements of infrasound. Azimuth changes of infrasound from volcanis eruption were used to retrieve mesospheric zonal winds. The amplitude fluctuations of infrasound from ocean swells represent planetary waves which modulate the atmospheric wave guide. Fluctuations are much larger in Northern hemispheres than in Southern hemisphere, because the amplitude of planetary waves is larger in Northern hemisphere where continental areas are more important. Infrasound monitoring also revealed anomalies at a seasonal scale in Antarctica or at the scale of several days in Arctic regionsin relation with Sudden Stratospheric Warming. The second way is the direct observation of large scale gravity waves. These waves, mainly produced in the troposphere, propagate upwards and break in the stratosphere producing a chaotic forcing of the stratosphere. This is at the origin of a slow and large scale motion in which air masses are driven upward and poleward from the tropical lower stratosphere. In polar regions, they are pushed downward producing

  2. Infrasound signals coupled from an underwater explosion

    NASA Astrophysics Data System (ADS)

    Che, I.-Y.; Kim, T. S.; Lee, H.-I.

    2012-04-01

    On 26 March 2010, a South Korean warship, Cheoanham, was sunken down offshore of an island, Bakryeong, in the Yellow Sea, South Korea. In the island that is near to the incident site, were a seismo-acoustic array and a broadband seismic station in operation. These stations recorded clear seismic and infrasonic signals associated with the warship-sinking. In addition, five infrasound arrays being operated in the inland of South Korea also detected the infrasound signals propagated up to 348 km from the source. We studied the seismic and infrasonic signatures from the event for the determination of exact source location and explanation of coupling phenomena among three different media; sea, solid earth and atmosphere. For the accurate source localization we fused all the available seismo-acoustic information of arrival time and azimuth estimates of coupled seismic and infrasonic signals. The calculated location is nearly coincident with the event location reported by the Civilian Military Joint Investigation Group, which shows seismo-acoustic location is much better than those calculated with just seismic or infrasonic dataset. The relationship between explosion depth and charge was constrained with the period of the observed infrasonic signals. The attenuated amplitude of infrasound signal was corrected to estimate the perturbed air pressure at source location.

  3. Assessing and optimizing infrasound network performance: application to remote volcano monitoring

    NASA Astrophysics Data System (ADS)

    Tailpied, D.; LE Pichon, A.; Marchetti, E.; Kallel, M.; Ceranna, L.

    2014-12-01

    Infrasound is an efficient monitoring technique to remotely detect and characterize explosive sources such as volcanoes. Simulation methods incorporating realistic source and propagation effects have been developed to quantify the detection capability of any network. These methods can also be used to optimize the network configuration (number of stations, geographical location) in order to reduce the detection thresholds taking into account seasonal effects in infrasound propagation. Recent studies have shown that remote infrasound observations can provide useful information about the eruption chronology and the released acoustic energy. Comparisons with near-field recordings allow evaluating the potential of these observations to better constrain source parameters when other monitoring techniques (satellite, seismic, gas) are not available or cannot be made. Because of its regular activity, the well-instrumented Mount Etna is in Europe a unique natural repetitive source to test and optimize detection and simulation methods. The closest infrasound station part of the International Monitoring System is located in Tunisia (IS48). In summer, during the downwind season, it allows an unambiguous identification of signals associated with Etna eruptions. Under the European ARISE project (Atmospheric dynamics InfraStructure in Europe, FP7/2007-2013), experimental arrays have been installed in order to characterize infrasound propagation in different ranges of distance and direction. In addition, a small-aperture array, set up on the flank by the University of Firenze, has been operating since 2007. Such an experimental setting offers an opportunity to address the societal benefits that can be achieved through routine infrasound monitoring.

  4. Strombolian surface activity regimes at Yasur volcano, Vanuatu, as observed by Doppler radar, infrared camera and infrasound

    NASA Astrophysics Data System (ADS)

    Meier, K.; Hort, M.; Wassermann, J.; Garaebiti, E.

    2016-08-01

    In late 2008 we recorded a continuous multi-parameter data set including Doppler radar, infrared and infrasound data at Yasur volcano, Vanuatu. Our recordings cover a transition in explosive style from ash-rich to ash-free explosions followed again by a phase of high ash discharge. To assess the present paradigm of Strombolian behavior in this study we investigate the geophysical signature of these different explosive episodes and compare our results to observations at Stromboli volcano, Italy. To this end we characterize Yasur's surface activity in terms of material movement, temperature and excess pressure. The joint temporal trend in these data reveals smooth variations of surface activity and regime-like persistence of individual explosion forms over days. Analysis of all data types shows ash-free and ash-rich explosive styles similar to those found at Stromboli volcano. During ash-free activity low echo powers, high explosion velocities and high temperatures result from the movement of isolated hot ballistic clasts. In contrast, ash-rich episodes exhibit high echo powers, low explosion velocities and low temperatures linked to the presence of colder ash-rich plumes. Furthermore ash-free explosions cause high excess pressure signals exhibiting high frequencies opposed to low-amplitude, low-frequency signals accompanying ash-rich activity. To corroborate these findings we compare fifteen representative explosions of each explosive episode. Explosion onset velocities derived from Doppler radar and infrared camera data are in excellent agreement and consistent with overall observations in each regime. Examination of infrasound recordings likewise confirms our observations, although a weak coupling between explosion velocity and excess pressure indicates changes in wave propagation. The overall trend in explosion velocity and excess pressure however demonstrates a general correlation between explosive style and explosion intensity, and points to stability of the

  5. Infra-sound Signature of Lightning

    NASA Astrophysics Data System (ADS)

    Arechiga, R. O.; Badillo, E.; Johnson, J.; Edens, H. E.; Rison, W.; Thomas, R. J.

    2012-12-01

    We have analyzed thunder from over 200 lightning flashes to determine which part of thunder comes from the gas dynamic expansion of portions of the rapidly heated lightning channel and which from electrostatic field changes. Thunder signals were recorded by a ~1500 m network of 3 to 4 4-element microphone deployed in the Magdalena mountains of New Mexico in the summers of 2011 and 2012. The higher frequency infra-sound and audio-range portion of thunder is thought to come from the gas dynamic expansion, and the electrostatic mechanism gives rise to a signature infra-sound pulse peaked at a few Hz. More than 50 signature infra-sound pulses were observed in different portions of the thunder signal, with no preference towards the beginning or the end of the signal. Detection of the signature pulse occurs sometimes only for one array and sometimes for several arrays, which agrees with the theory that the pulse is highly directional (i.e., the recordings have to be in a specific position with respect to the cloud generating the pulse to be able to detect it). The detection of these pulses under quiet wind conditions by different acoustic arrays corroborates the electrostatic mechanism originally proposed by Wilson [1920], further studied by Dessler [1973] and Few [1985], observed by Bohannon [1983] and Balachandran [1979, 1983], and recently analyzed by Pasko [2009]. Pasko employed a model to explain the electrostatic-to-acoustic energy conversion and the initial compression waves in observed infrasonic pulses, which agrees with the observations we have made. We present thunder samples that exhibit signature infra-sound pulses at different times and acoustic source reconstruction to demonstrate the beaming effect.

  6. Frequency and Size of Strombolian Eruptions from the Phonolitic Lava Lake at Erebus Volcano, Antarctica: Insights from Infrasound and Seismic Observations on Bubble Formation and Ascent

    NASA Astrophysics Data System (ADS)

    Rotman, H. M. M.; Kyle, P. R.; Fee, D.; Curtis, A.

    2015-12-01

    Erebus, an active intraplate volcano on Ross Island, commonly produces bubble burst Strombolian explosions from a long-lived, convecting phonolitic lava lake. Persistent lava lakes are rare, and provide direct insights into their underlying magmatic system. Erebus phonolite is H2O-poor and contains ~30% anorthoclase megacrysts. At shallow depths lab measurements suggest the magma has viscosities of ~107 Pa s. This has implications for magma and bubble ascent rates through the conduit and into the lava lake. The bulk composition and matrix glass of Erebus ejecta has remained uniform for many thousands of years, but eruptive activity varies on decadal and shorter time scales. Over the last 15 years, increased activity took place in 2005-2007, and more recently in the 2013 austral summer. In the 2014 austral summer, new infrasound sensors were installed ~700 m from the summit crater hosting the lava lake. These sensors, supplemented by the Erebus network seismic stations, recorded >1000 eruptions between 1 January and 7 April 2015, with an average infrasound daily uptime of 9.6 hours. Over the same time period, the CTBT infrasound station IS55, ~25 km from Erebus, detected ~115 of the >1000 locally observed eruptions with amplitude decreases of >100x. An additional ~200 eruptions were recorded during local infrasound downtime. This represents an unusually high level of activity from the Erebus lava lake, and while instrument noise influences the minimum observable amplitude each day, the eruption infrasound amplitudes may vary by ~3 orders of magnitude over the scale of minutes to hours. We use this heightened period of variable activity and associated seismic and acoustic waveforms to examine mechanisms for bubble formation and ascent, such as rise speed dependence and collapsing foam; repose times for the larger eruptions; and possible eruption connections to lava lake cyclicity.

  7. Infrasound associated with the deep M 7.3 northeastern China earthquake of June 28, 2002

    NASA Astrophysics Data System (ADS)

    Che, Il-Young; Kim, Geunyoung; Pichon, Alexis Le

    2013-02-01

    On 28 June, 2002, a deep-focus (566 km) earthquake with a moment magnitude of 7.3 occurred in the China-Russia-North Korea border region. Despite its deep focus, the earthquake produced an infrasound signal that was observed by the remote infrasound array (CHNAR), 682 km from the epicenter, in South Korea. Coherent infrasound signals were detected sequentially at the receiver, with different arrival times and azimuths indicating that the signals were generated both near the epicenter and elsewhere. On the basis of the azimuth, arrival time measurements, and atmospheric ray simulation results, the source area of the infrasonic signals that arrived earlier were located along the eastern coastal areas of North Korea and Russia, whereas later signals were sourced throughout Japan. The geographically-constrained, and discrete, distribution of the sources identified is explained by infrasound propagation effects caused by a westward zonal wind that was active when the event occurred. The amplitude of the deep quake's signal was equivalent to that of a shallow earthquake with a magnitude of approximately 5. This study expands the breadth of seismically-associated infrasound to include deep earthquakes, and also supports the possibility that infrasound measurements could help determine the depth of earthquakes.

  8. Characterization and diagnostic methods for geomagnetic auroral infrasound waves

    NASA Astrophysics Data System (ADS)

    Oldham, Justin J.

    Infrasonic perturbations resulting from auroral activity have been observed since the 1950's. In the last decade advances in infrasonic microphone sensitivity, high latitude sensor coverage, time series analysis methods and computational efficiency have elucidated new types of auroral infrasound. Persistent periods of infrasonic activity associated with geomagnetic sub-storms have been termed geomagnetic auroral infrasound waves [GAIW]. We consider 63 GAIW events recorded by the Fairbanks, AK infrasonic array I53US ranging from 2003 to 2014 and encompassing a complete solar cycle. We make observations of the acoustic features of these events alongside magnetometer, riometer, and all-sky camera data in an effort to quantify the ionospheric conditions suitable for infrasound generation. We find that, on average, the generation mechanism for GAIW is confined to a region centered about ~60 0 longitude east of the anti-Sun-Earth line and at ~770 North latitude. We note furthermore that in all cases considered wherein imaging riometer data are available, that dynamic regions of heightened ionospheric conductivity periodically cross the overhead zenith. Consistent features in concurrent magnetometer conditions are also noted, with irregular oscillations in the horizontal component of the field ubiquitous in all cases. In an effort to produce ionosphere based infrasound free from the clutter and unknowns typical of geophysical observations, an experiment was undertaken at the High Frequency Active Auroral Research Program [HAARP] facility in 2012. Infrasonic signals appearing to originate from a source region overhead were observed briefly on 9 August 2012. The signals were observed during a period when an electrojet current was presumed to have passed overhead and while the facilities radio transmitter was periodically heating the lower ionosphere. Our results suggest dynamic auroral electrojet currents as primary sources of much of the observed infrasound, with

  9. The source of infrasound associated with long-period events at Mount St. Helens

    NASA Astrophysics Data System (ADS)

    Matoza, Robin S.; GarcéS, Milton A.; Chouet, Bernard A.; D'Auria, Luca; Hedlin, Michael A. H.; de Groot-Hedlin, Catherine; Waite, Gregory P.

    2009-04-01

    During the early stages of the 2004-2008 Mount St. Helens eruption, the source process that produced a sustained sequence of repetitive long-period (LP) seismic events also produced impulsive broadband infrasonic signals in the atmosphere. To assess whether the signals could be generated simply by seismic-acoustic coupling from the shallow LP events, we perform finite difference simulation of the seismo-acoustic wavefield using a single numerical scheme for the elastic ground and atmosphere. The effects of topography, velocity structure, wind, and source configuration are considered. The simulations show that a shallow source buried in a homogeneous elastic solid produces a complex wave train in the atmosphere consisting of P/SV and Rayleigh wave energy converted locally along the propagation path, and acoustic energy originating from the source epicenter. Although the horizontal acoustic velocity of the latter is consistent with our data, the modeled amplitude ratios of pressure to vertical seismic velocity are too low in comparison with observations, and the characteristic differences in seismic and acoustic waveforms and spectra cannot be reproduced from a common point source. The observations therefore require a more complex source process in which the infrasonic signals are a record of only the broadband pressure excitation mechanism of the seismic LP events. The observations and numerical results can be explained by a model involving the repeated rapid pressure loss from a hydrothermal crack by venting into a shallow layer of loosely consolidated, highly permeable material. Heating by magmatic activity causes pressure to rise, periodically reaching the pressure threshold for rupture of the "valve" sealing the crack. Sudden opening of the valve generates the broadband infrasonic signal and simultaneously triggers the collapse of the crack, initiating resonance of the remaining fluid. Subtle waveform and amplitude variability of the infrasonic signals as

  10. Modeling the Infrasound Acoustic Signal Generation of Underground Explosions at the Source Physics Experiment

    NASA Astrophysics Data System (ADS)

    Whitaker, R. W.; Jones, K. R.; Arrowsmith, S.

    2013-12-01

    One of the primary goals of the Source Physics Experiment is to improve upon and develop new physics based models for underground nuclear explosions using scaled, underground chemical explosions as proxies. Jones et. al, (AGU 2012) previously presented results describing the use of the Rayleigh integral (RI) to model the source region of the SPE explosions. While these results showed that the source region could be modeled using the RI, there were some complexities in the produced, synthetic waveforms that were unaccounted for when compared to the observed data. To gain insight into these complexities and to verify the results of the RI method, we used CAVEAT, a two-dimensional computational fluid dynamics, time-domain finite-difference code developed at Los Alamos National Labs (LANL). CAVEAT has been used in the solution of high speed and low speed fluid problems. While the RI uses the observed acceleration records from the 12 vertical surface accelerometers installed above ground zero, CAVEAT employs a synthetic source-time function, based on the acceleration records, that varies with range and time. This model provides a velocity boundary condition at the bottom boundary of the CAVEAT computation mesh that drives the atmospheric pressure wave into the atmosphere.

  11. The source of infrasound associated with long-period events at mount St. Helens

    USGS Publications Warehouse

    Matoza, R.S.; Garces, M.A.; Chouet, B.A.; D'Auria, L.; Hedlin, M.A.H.; De Groot-Hedlin, C.; Waite, G.P.

    2009-01-01

    During the early stages of the 2004-2008 Mount St. Helens eruption, the source process that produced a sustained sequence of repetitive long-period (LP) seismic events also produced impulsive broadband infrasonic signals in the atmosphere. To assess whether the signals could be generated simply by seismic-acoustic coupling from the shallow LP events, we perform finite difference simulation of the seismo-acoustic wavefield using a single numerical scheme for the elastic ground and atmosphere. The effects of topography, velocity structure, wind, and source configuration are considered. The simulations show that a shallow source buried in a homogeneous elastic solid produces a complex wave train in the atmosphere consisting of P/SV and Rayleigh wave energy converted locally along the propagation path, and acoustic energy originating from , the source epicenter. Although the horizontal acoustic velocity of the latter is consistent with our data, the modeled amplitude ratios of pressure to vertical seismic velocity are too low in comparison with observations, and the characteristic differences in seismic and acoustic waveforms and spectra cannot be reproduced from a common point source. The observations therefore require a more complex source process in which the infrasonic signals are a record of only the broadband pressure excitation mechanism of the seismic LP events. The observations and numerical results can be explained by a model involving the repeated rapid pressure loss from a hydrothermal crack by venting into a shallow layer of loosely consolidated, highly permeable material. Heating by magmatic activity causes pressure to rise, periodically reaching the pressure threshold for rupture of the "valve" sealing the crack. Sudden opening of the valve generates the broadband infrasonic signal and simultaneously triggers the collapse of the crack, initiating resonance of the remaining fluid. Subtle waveform and amplitude variability of the infrasonic signals as

  12. Assessing and optimizing infrasound network performance: application to remote volcano monitoring

    NASA Astrophysics Data System (ADS)

    Tailpied, Dorianne; Le Pichon, Alexis; Marchetti, Emanuele; Ceranna, Lars; Pilger, Christopher

    2015-04-01

    Interest in infrasound propagation studies has been revived since the Comprehensive nuclear Test Ban Treaty (CTBT) was adopted in 1996. The International Monitoring System (IMS) is designed to ensure compliance with the CTBT by detecting and locating explosions in the world using at least 2 stations. Even not yet fully established, the infrasound network already allows studies on a global scale as it has demonstrated to be a major asset to remotely identify and analyze geophysical events such as volcanoes. Simulation methods incorporating realistic source and propagation effects have been developed to quantify the detection capability of this network. These methods can also be used to optimize the network configuration (number of stations, geographical location) in order to reduce the detection thresholds taking into account seasonal effects in infrasound propagation. Recent studies have shown that remote infrasound observations can provide useful information about eruption chronology and the released acoustic energy. Comparisons with near-field recordings allow evaluating the potential of these observations to better constrain source parameters when other monitoring techniques (satellite, seismic, gas) are not available or cannot be made. Because of its regular activity, the well-instrumented Mount Etna is in Europe a unique natural repetitive source to test and optimize detection and simulation methods. In summer, during the downwind season, its eruptions are quasi-permanently detected by IS48 in Tunisia, the closest infrasound station part of the IMS. Under the European ARISE project (Atmospheric dynamics InfraStructure in Europe, FP7/2007-2013), experimental arrays have been installed in order to characterize infrasound propagation in different ranges of distance and direction. Such an experimental setting offers an opportunity to address the societal benefits that can be achieved through routine infrasound monitoring.

  13. Listening to Earthquakes with Infrasound

    NASA Astrophysics Data System (ADS)

    Mucek, A. E.; Langston, C. A.

    2011-12-01

    A tripartite infrasound array was installed to listen to earthquakes occurring along the Guy-Greenbrier fault in Arkansas. The active earthquake swarm is believed to be caused by deep waste water injections and will allow us to explain the mechanisms causing earthquake "booms" that have been heard during an earthquake. The array has an aperture of 50 meters and is installed next to the X301 seismograph station run by the Center for Earthquake Research and Information (CERI). This arrangement allows simultaneous recording of seismic and acoustic changes from the arrival of an earthquake. Other acoustic and seismic sources that have been found include thunder from thunderstorms, gunshots, quarry explosions and hydraulic fracturing activity from the local gas wells. The duration of the experiment is from the last week of June to the last week of September 2011. During the first month and a half, seven local earthquakes were recorded, along with numerous occurrences of the other infrasound sources. Phase arrival times of the recorded waves allow us to estimate wave slowness and azimuth of infrasound events. Using these two properties, we can determine whether earthquake "booms" occur at a site from the arrival of the P-wave or whether the earthquake "booms" occur elsewhere and travel through the atmosphere. Preliminary results show that the infrasound correlates well to the ground motion during an earthquake for frequencies below 15 Hertz.

  14. Eruptions of Mount Erebus Volcano Constrained with Infrasound, Video, and Doppler Radar

    NASA Astrophysics Data System (ADS)

    Johnson, J. B.; Jones, K. R.; Aster, R.; Kyle, P.; McIntosh, W.; Gerst, A.

    2008-12-01

    Co-eruptive infrasound recorded within several km of volcanoes can provide effective constraints on atmospheric accelerations or momentum exchange in the vicinity of active volcanic vents. These atmospheric perturbations can be induced by impulsive gas injection into the atmosphere (i.e., eruptive explosions), by deflection of a solid or fluid lava surface, or through a superposition of these effects. The "simple" lava lake bubble-bursting eruptions of Mount Erebus Volcano (Antarctica) provide an ideal test bed for multi- disciplinary observations of volcanic infrasound because of proximal (within few hundred meters) deployment of microphones and line-of-sight viewing geometry of cameras and radar to the vent. Erebus video observations provide timing constraints on the infrasound generation mechanisms, which include both pre- eruptive distension of the lava lake surface and gas expansion and jetting following large explosive bubble bursts. Network infrasound recordings are used to quantify the time history of explosive gas flux and cumulative yield (>103 kg of gas in ~0.5 s), which is corroborated by the video and Doppler radar observations. Infrasound records from a three-station network also show azimuthal variations, which can be attributed to non-isotropic components of the acoustic wavefield radiated during eruption. We model Erebus gas bubble bursts as a combination of symmetric gas expansion (monopole source) and gas jetting (dipole source) and corroborate this explosive asymmetry with video and Doppler radar observations.

  15. Simulation and Analysis of Infrasound Generated by Convective Storms and Tornadoes

    NASA Astrophysics Data System (ADS)

    Schecter, D.; Nicholls, M.

    2011-12-01

    Observational studies have shown that severe storms can emit abnormally strong, sustained infrasound in the 0.5-5 Hz frequency range. There is reason to believe that the infrasonic emissions come from developing and mature tornadoes, but some ambiguity remains in the interpretation of the data. It is fair to say that we do not yet fully understand the conditions for which a vortex signal is discernible from the infrasound of non-tornadic sources within a storm. There is a pressing need to advance our fundamental understanding of the different mechanisms that generate infrasound in atmospheric convection. To this end, numerical modeling may be the best method of investigation. We are exploring this avenue of research with a customized version of the Regional Atmospheric Modeling System (c-RAMS). Previous studies have established the basic credibility of c-RAMS for simulating acoustic phenomena. More recently, we have developed a convenient method for diagnosing the primary sources of infrasound in complex storm simulations. The method is based on a generalization of Lighthill's acoustic analogy, and is aptly illustrated in the context of a simulated cumulonimbus. Applying the diagnostic method to this system, we find that the 0.1-1 Hz infrasound of diabatic processes in the hail-to-rain transition layer dominates that of turbulent wind fluctuations covering the entire storm. We have also used c-RAMS to investigate the infrasound of tornadoes created by artificial buoyancy forcing in a dry, rotational environment. The simulated tornadoes have realistic structure, but their cores are typically quiet in the frequency range of interest. In other words, we find that dry fluctuations of the vortex core may not provide a robust source of discernible infrasound. Apparent deficiencies of earlier theories that predicted otherwise will be addressed. This work was supported by NSF grant AGS-0832320.

  16. Characterization of the 2008 Kasatochi and Okmok eruptions using remote infrasound arrays

    NASA Astrophysics Data System (ADS)

    Fee, David; Steffke, Andrea; Garces, Milton

    2010-01-01

    The 2008 Plinian eruptions of Kasatochi and Okmok volcanoes were recorded by six remote International Monitoring System infrasound arrays. High-amplitude infrasound at these stations, combined with remote sensing, permits insight into important volcanic source parameters, such as origin times, durations, and source characteristics. Infrasound from the 7-8 August Kasatochi eruption consists of three well-defined eruption pulses, with the first two steam-rich and the last ash-rich. Pulse 2 is the most energetic and impulsive. Okmok produced over 9 h of continuous infrasound on 12-13 July. Acoustic propagation modeling for the Okmok eruption and first Kasatochi pulse predict thermospheric ducting and origin times consistent with seismic and satellite observations. However, theoretical acoustic origin times of pulses 2-3 are predicted to occur ˜15 min earlier than the seismic. Stratospheric ducting for these later pulses provides more consistent origin times. Although both volcanoes ejected ash into the stratosphere (>15 km), Kasatochi produced higher amplitude infrasound than Okmok. Previous studies have shown sustained infrasound with frequencies <0.5 Hz is indicative of high-altitude ash emissions. Kasatochi and Okmok recordings are consistent with this, as stratospheric emissions evident in satellite imagery are correlated with sustained 0.01-0.5 Hz infrasound. Further, the acoustic spectrum shape resembles the spectrum from man-made jets, suggesting a self-similar noise generation mechanism proposed in earlier work. Although uncertainties exist, observations and propagation modeling from Kasatochi suggest self-similarity is apparent at long distances (>2000 km) and does not seem to be appreciably affected by changes in ash content between the eruption pulses.

  17. Volcano infrasound: A review

    NASA Astrophysics Data System (ADS)

    Johnson, Jeffrey Bruce; Ripepe, Maurizio

    2011-09-01

    Exploding volcanoes, which produce intense infrasound, are reminiscent of the veritable explosion of volcano infrasound papers published during the last decade. Volcano infrasound is effective for tracking and quantifying eruptive phenomena because it corresponds to activity occurring near and around the volcanic vent, as opposed to seismic signals, which are generated by both surface and internal volcanic processes. As with seismology, infrasound can be recorded remotely, during inclement weather, or in the dark to provide a continuous record of a volcano's unrest. Moreover, it can also be exploited at regional or global distances, where seismic monitoring has limited efficacy. This paper provides a literature overview of the current state of the field and summarizes applications of infrasound as a tool for better understanding volcanic activity. Many infrasound studies have focused on integration with other geophysical data, including seismic, thermal, electromagnetic radiation, and gas spectroscopy and they have generally improved our understanding of eruption dynamics. Other work has incorporated infrasound into volcano surveillance to enhance capabilities for monitoring hazardous volcanoes and reducing risk. This paper aims to provide an overview of volcano airwave studies (from analog microbarometer to modern pressure transducer) and summarizes how infrasound is currently used to infer eruption dynamics. It also outlines the relative merits of local and regional infrasound surveillance, highlights differences between array and network sensor topologies, and concludes with mention of sensor technologies appropriate for volcano infrasound study.

  18. Recent Advances in Infrasound Science for National Security Applications

    NASA Astrophysics Data System (ADS)

    Arrowsmith, S.; Blom, P. S.; Marcillo, O. E.; Whitaker, R. W.

    2014-12-01

    Infrasound is sound below the frequency-threshold of human hearing, covering the frequency range from 0.01 - 20 Hz. Infrasound science studies the generation, propagation, measurement, and analysis of infrasound. Sources of infrasound include a wide variety of energetic natural and manmade phenomena that include chemical and nuclear explosions, rockets and missiles, and aircraft. The dominant factors influencing the propagation of infrasound are the spatial and temporal variations in temperature, wind speed, and wind direction. In recent years, Infrasound Science has experienced a renaissance due to the installation of an international monitoring system of 60 infrasound arrays for monitoring the Comprehensive Nuclear Test Ban Treaty, and to the demonstrated value of regional infrasound networks for both scientific and applied purposes. Furthermore, in the past decade, significant advances have been made on using measurements of infrasound to invert for these properties of the atmosphere at altitudes where alternative measurement techniques are extremely costly. This presentation provides a review of recent advances in infrasound science as relevant to National Security applications.

  19. Detecting geyser activity with infrasound

    NASA Astrophysics Data System (ADS)

    Johnson, J. B.; Anderson, J. F.; Anthony, R. E.; Sciotto, M.

    2013-04-01

    We monitored geyser activity in the Lower Geyser Basin (LGB) of Yellowstone National Park with dual four-element microphone arrays separated by ~ 600 m. The arrays were independently used to identify incident coherent plane wave energy, then conjoint cross beam back-azimuths from the two arrays were used to precisely locate signal sources. During a week in August 2011 we located repeating infrasound events, peaked in energy between 1 and 10 Hz, originating from at least five independent geothermal features, including the episodically erupting Great Fountain, Fountain and Kaleidoscope Geysers, as well as periodic infrasound from nearby Botryoidal and persistent sound from Firehole Spring. Although activity from nearby cone-type geysers was not detected in the infrasound band up through 50 Hz, the major fountain-type geysers (i.e., with columns greater than 10 m) could be detected at several kilometers, and two minor geysers (i.e., a few meters in eruption height) could be tracked at distances up to a few hundred meters. Detection of geyser activity was especially comprehensive at night when ambient noise was low. We conclude that infrasound monitoring of fountain-type geysers permits convenient tracking of geyser activity, episodicity, signal duration, energy content, and spectral content. These parameters enable objective statistical quantification of geyser behavior and changes over time that may be due to external forcing. Infrasonic study of geyser activity in an individual basin has great monitoring utility and can be reasonably accomplished with two or more distributed sensor arrays.

  20. IPLOR performance in detecting infrasound from volcanic eruptions

    NASA Astrophysics Data System (ADS)

    Ghica, Daniela; Popa, Mihaela

    2016-04-01

    Plostina infrasound array (IPLOR) is located in the central part of Romania, in Vrancea region, its current configuration consisting of 6 elements equipped with Chaparral Physics sensors deployed over a 2.5 km aperture. The array detectability observed after processing of more than 6 years of data has shown that IPLOR is more effective in measuring mainly infrasound signals produced by natural and anthropogenic impulsive sources. This can be explained by the sensors' characteristics (frequency response, dynamic range) and the large aperture of array. Among the types of events observed with IPLOR, an emphasis can be given to the Mt. Etna volcanic eruptions as one of the powerful infrasound source recorded by the array. Located at about 1320 km distance from volcano, the array has proved efficient in observing both large and small eruptions. In case of the most large eruptive episodes occurred lately (April and October 2013, December 2015), long duration infrasonic signals were detected, the initial impulsive signature of the volcanic explosion being followed by a long train of irregular waves with smaller amplitudes and higher frequency, extended over periods ranging from 6 hours to more than three days (in December 2015). For the purpose of assessing the IPLOR performance in detecting Etna eruptions, the signal interactive analysis was performed using WinPMCC, CEA/DASE version of PMCC software. The infrasound detections obtained were plotted in function of back-azimuth, velocity and frequency, showing that the detectability is dependent both on the diurnal variations of the noise around the array (during the night the human activity diminishes) and on the seasonally dependent stratospheric winds (westward propagation during summer and eastward propagation during winter). In case of the Etna eruptive episodes detected by IPLOR, the back azimuth observed is in good agreement with the expected value (230o), i.e. an average value of 232±2o could be resolved. The

  1. Infrasound observation of the apparent North Korean nuclear test of 25 May 2009

    NASA Astrophysics Data System (ADS)

    Che, Il-Young; Kim, Tae Sung; Jeon, Jeong-Soo; Lee, Hee-Il

    2009-11-01

    On 25 May 2009, a seismic event (mb 4.6) was recorded from a source in northeastern North Korea, close to the location of a previous seismic event on 9 October 2006. Both events have been declared to be nuclear tests by North Korea. For the more recent test, five seismo-acoustic arrays in South Korea recorded epicentral infrasonic signals. The signals are characterized by amplitudes from 0.16 to 0.35 microbar and dominant frequencies between 0.8 and 4.3 Hz. Celerities determined for the arrivals suggest that most of the infrasonic energy travelled as a stratospheric phase. Based on observed stratospheric amplitudes, the epicentral infrasonic energy was estimated to be equivalent to that expected from 3.0 tons of high explosives detonated on the surface. We conclude that this small energy estimate is due to the atmospheric coupling from the strong surface ground motion rather than the direct transfer of explosion energy to the air. This relatively small infrasonic to seismic energy ratio could be used to distinguish the event from a common surface explosion.

  2. Infrasound research at Kola Regional Seismological Centre, Russia

    NASA Astrophysics Data System (ADS)

    Asming, Vladimir; Kremenetskaya, Elena

    2013-04-01

    A small-aperture infrasound array has been installed in Kola Peninsula, Russia 17 km far from the town of Apatity in the year 2000. It comprises 3 Chaparral V microbarographs placed closely to the APA seismic array sensors and equipped with pipe wind reducing filters. The data are digitized at the array site and transmitted in real time to a processing center in Apatity. To search for infrasound events (arrivals of coherent signals) a beamforming-style detector has been developed. Now it works in near real time. We analyzed the detecting statistics for different frequency bands. Most man-made events are detected in 1-5 Hz band, microbaromes are typically detected in 0.2-1 Hz band. In lower frequencies we record mostly a wind noise. A data base of samples of infrasound signals of different natures has been collected. It contains recordings of microbaromes, industrial and military explosions, airplane shock waves, infrasound of airplanes, thunders, rocket launches and reentries, bolides etc. The most distant signals we have detected are associated with Kursk Magnetic Anomaly explosions (1700 km far from Apatity). We implemented an algorithm for association of infrasound signals and preliminary location of infrasound events by several arrays. It was tested with Apatity data together with data of Sweden - Finnish infrasound network operated by the Institute of Space Physics in Umea (Sweden). By agreement with NORSAR we have a real-time access to the data of Norwegian experimental infrasound installation situated in Karasjok (North Norway). Currently our detection and location programs work both with Apatity and Norwegian data. The results are available in Internet. Finnish militaries routinely destroy out-of-date weapon in autumns at the same compact site in North Finland. This is a great source of repeating infrasound signals of the same magnitude and origin. We recorded several hundreds of such explosions. The signals have been used for testing our location routines

  3. Infrasound Calibration Experiment at Sayarim, Israel: preliminary tests

    NASA Astrophysics Data System (ADS)

    Gitterman, Y.; Hofstetter, A.; Garces, M.; Bowman, J. R.; Fee, D.; Israelsson, H.

    2009-12-01

    We are establishing a Ground Truth (GT0) infrasound dataset for Middle East/Mediterranean region, through conducting a series of surface explosions at Sayarim Military Range (SMR), Negev desert, which culminated with an 82-ton explosion in August 2009. The dataset will be used to characterize the infrasonic propagation in the region, depending on source features and atmosphere conditions, and thus to improve monitoring capabilities of International Monitoring System (IMS). Test explosions of broad yield range and various designs were conducted on the first stage, in different days and seasons, thus providing a wide range of atmospheric conditions. The goals were to: 1) test charge design and assembling, and train procedures of logistics and coordination, for preparation and conducting of the main explosion; 2) analyze atmospheric effects on infrasound propagation in different azimuths based on collected meteo-data. In June-July 2008, we conducted a series of 13 detonations of outdated ammunition (in the range 0.2-10 ton) and two experimental shots of 1 ton of different explosives (TNT and Composition B). The two shots were placed close to an ammunition explosion and 10 min afterwards to help estimate ammunition actual yield (TNT). Some of these explosions were observed at IMS station I48TN (Tunisia) at ~2500 km, using array processing and analysis. Two test explosions of 1 ton and 5 tons of different recuperated HE explosives were conducted at SMR in December 2008. High-pressures in air-shock waves at close distances (150-250 m) were measured and speed video recording was done. The data obtained from the test series provided estimation of the explosion yield, that showed approximate TNT equivalency. We analyzed signals from the tests, recorded on seismic and acoustic channels at near-source and local distances. We compared energy generation for different explosives, including cratering conditions, and investigated the influence of wind direction on infrasound

  4. Recent Infrasound Calibration Activity at Los Alamos

    NASA Astrophysics Data System (ADS)

    Whitaker, R. W.; Marcillo, O. E.

    2014-12-01

    Absolute infrasound sensor calibration is necessary for estimating source sizes from measured waveforms. This can be an important function in treaty monitoring. The Los Alamos infrasound calibration chamber is capable of absolute calibration. Early in 2014 the Los Alamos infrasound calibration chamber resumed operations in its new location after an unplanned move two years earlier. The chamber has two sources of calibration signals. The first is the original mechanical piston, and the second is a CLD Dynamics Model 316 electro-mechanical unit that can be digitally controlled and provide a richer set of calibration options. During 2008-2010 a number of upgrades were incorporated for improved operation and recording. In this poster we give an overview of recent chamber work on sensor calibrations, calibration with the CLD unit, some measurements with different porous hoses and work with impulse sources.

  5. Interactions between intermittent gravity waves and infrasounds

    NASA Astrophysics Data System (ADS)

    Ribstein, Bruno; Millet, Christophe; Lott, Francois; de La Camara, Alvaro

    2016-11-01

    Even though the accuracy of atmospheric specifications is constantly improving, it is well known that the main part of gravity waves is still yet not resolved in the available data. In most infrasound modeling studies, the unresolved gravity wave field is often represented as a deterministic field that is superimposed on a given average background state. Direct observations in the lower stratosphere show, however, that the gravity wave field is very intermittent, and is often dominated by rather well defined wave packets. In this study we sample the gravity wave spectrum by launching few monochromatic waves and choose their properties stochastically to mimic the intermittency. The statistics of acoustic signals are computed by decomposing the original signal into a sum of modal pulses. Owing to the disparity of the gravity and acoustic lengthscales, the interaction can be described using a multiplescale analysis and the appropriate amplitude evolution equation involves certain random terms that are related to the gravity wave sources. More specifically, it is shown how the unpredictable low level small-scale dynamics triggers multiple random stratospheric waveguides in which high frequency infrasound components can propagate efficiently.

  6. Overview of IMS infrasound station and engineering projects

    NASA Astrophysics Data System (ADS)

    Marty, J.; Doury, B.; Kramer, A.; Martysevich, P.

    2015-12-01

    The Provisional Technical Secretariat (PTS) of the Comprehensive Nuclear-Test-Ban Treaty (CTBTO) has a continuous interest in enhancing its capability in acoustic source detection, localization and characterization. The infrasound component of the International Monitoring System (IMS) constitutes the only worldwide ground-based infrasound network. It consists of sixty stations, among which forty-eight are already certified and continuously transmit data to the International Data Centre (IDC) in Vienna, Austria. Each infrasound station is composed of an array of infrasound sensors capable of measuring micro-pressure changes produced at ground level by infrasonic waves. The characteristics of infrasonic waves are computed in near real-time by IDC automatic detection software and are used as an input to IDC source categorization and localization algorithms. The PTS is continuously working towards the completion and sustainment of the IMS infrasound network. The objective of this presentation is to review the main activities performed in the IMS infrasound network over the last five years. This includes construction, installation, certification, major upgrade and revalidation activities. Major technology development projects to improve the reliability and robustness of IMS infrasound stations as well as their compliance with IMS Operational Manual requirements will also be presented. This includes advances in array geometry, wind noise reduction, system calibration, meteorological data as well as power and communication infrastructures. Finally the impact of all these changes on the overall detection capability of the IMS infrasound network will be highlighted.

  7. Infrasound emission generated by wind turbines

    NASA Astrophysics Data System (ADS)

    Ceranna, Lars; Pilger, Christoph

    2014-05-01

    Aerodynamic noise emissions from the continuously growing number of wind turbines in Germany are creating increasing problems for infrasound recording systems. Such systems are equipped with highly sensitive micro pressure sensors, which are accurately measuring acoustic signals in a frequency range inaudible to humans. At infrasound station IGADE, north of Bremen, a constantly increasing background noise has been observed throughout the years since its installation in 2005. The spectral peaks are reflecting well the blade passing harmonics, which vary with prevailing wind speeds. Overall, a decrease is noted for the infrasound array's detection capability. This aspect is particularly important for the other two sites of the German infrasound stations I26DE in the Bavarian Forest and I27DE in Antarctica, because plans for installing wind turbines near these locations are being under discussion. These stations are part of the International Monitoring System (IMS) verifying compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT), and have to meet stringent specifications with respect to infrasonic background noise. Therefore data obtained during a field experiment with mobile micro-barometer stations for measuring the infrasonic pressure level of a single horizontal-axis wind turbine have been revisited. The results of this experiment successfully validate a theoretical model which estimates the generated sound pressure level of wind turbines and makes it possible to specify the minimum allowable distance between wind turbines and infrasound stations for undisturbed recording. Since the theoretical model also takes wind turbine design parameters into account, suitable locations for planned infrasound stations outside the determined disturbance range can be found, which will be presented; and vice versa, the model calculations' results for fixing the minimum distance for wind turbines planned for installation in the vicinity of an existing infrasound array.

  8. Empirical Relationships from Regional Infrasound Signals

    NASA Astrophysics Data System (ADS)

    Negraru, P. T.; Golden, P.

    2011-12-01

    Two yearlong infrasound observations were collected at two arrays located within the so called "Zone of Silence" or "Shadow Zone" from well controlled explosive sources to investigate the long term atmospheric effects on signal propagation. The first array (FNIAR) is located north of Fallon NV, at 154 km from the munitions disposal facility outside of Hawthorne NV, while the second array (DNIAR) is located near Mercury NV, approximately 293 km south east of the detonation site. Based on celerity values, approximately 80% of the observed arrivals at FNIAR are considered stratospheric (celerities below 300 m/s), while 20% of them propagated as tropospheric waveguides with celerities of 330-345 m/s. Although there is considerable scatter in the celerity values, two seasonal effects were observed for both years; 1) a gradual decrease in celerity from summer to winter (July/January period) and 2) an increase in celerity values that starts in April. In the winter months celerity values can be extremely variable, and we have observed signals with celerities as low as 240 m/s. In contrast, at DNIAR we observe much stronger seasonal variations. In winter months we have observed tropospheric, stratospheric and thermospheric arrivals while in the summer mostly tropospheric and slower thermospheric arrivals dominate. This interpretation is consistent with the current seasonal variation of the stratospheric winds and was confirmed by ray tracing with G2S models. In addition we also discuss how the observed infrasound arrivals can be used to improve ground truth estimation methods (location, origin times and yield). For instance an empirical wind parameter derived from G2S models suggests that the differences in celerity values observed for both arrays can be explained by changes in the wind conditions. Currently we have started working on improving location algorithms that take into account empirical celerity models derived from celerity/wind plots.

  9. Assessing the detection capability of the global IMS infrasound network

    NASA Astrophysics Data System (ADS)

    Le Pichon, A.; Vergoz, J.; Brachet, N.; Ceranna, L.; Green, D.; Evers, L.

    2008-12-01

    A global scale analysis based on available detection lists for all operating IMS infrasound stations confirms that the primary factor controlling signal detectability is the seasonal variability of the stratospheric wind circulation. At most arrays, near %80 of the detections in the 0.2 to 2 Hz bandpass are associated with propagation downwind of the dominant wind direction. The seasonal transition in the bearings and number of detections between easterly and westerly directions is presented. The observed detection capability of the IMS network is compared to the predicted one using near-real time atmospheric updates and station- dependent wind noise models. The influence of individual model parameters on the network performance is systematically assessed. At frequencies of interest for detecting atmospheric explosions (0.2 to 2 Hz), the simulations predict that explosions equivalent to ~500 t of TNT would be detected by at least two stations of the full IMS network at any time of the year. Comprehensive ground-truth databases provide a statistical approach for evaluating the potential of infrasound monitoring. Accidental explosions are analysed and used here as benchmark for validating the calculated threshold maps. Such studies would help to optimize the siting of infrasound arrays with respect to both the number and configuration in order to monitor infrasonic sources of interest. They are an important step to enable a successful monitoring regime for atmospheric or surface events to act as an effective verification tool in any future enforcement of the CTBT.

  10. Infrasound Studies of Alaskan Volcanoes

    NASA Astrophysics Data System (ADS)

    McNutt, S. R.; Arnoult, K.; Szuberla, C.; Olson, J. V.; Wilson, C. R.

    2010-12-01

    Infrasound has been used to study a number of Alaskan volcanic eruptions over the last 15 years. Arrays include the I53US array of 8 sensors in Fairbanks installed in 2002 under the CTBT umbrella; an array of 4 sensors installed at Okmok Volcano in summer 2010 by the Alaska Volcano Observatory (AVO); and a 6-sensor array installed in Dillingham in September 2010 by the UAF Infrasound Group. Individual sensors have been installed by AVO at Pavlof (1996), Shishaldin (1997), Augustine (2006), Fourpeaked (2006), and Redoubt (2009) volcanoes. These have been especially valuable because they provide precise source timing and signal strength that allow the correct identification of atmospheric paths. Small volcanic explosions have been recorded at local stations only for Pavlof, Shishaldin and Fourpeaked volcanoes. The more interesting large explosive eruptions have been recorded on both local stations and arrays from eruptions at Augustine in 2006 (13 events), Fourpeaked in 2006 (2 events), Cleveland in 2007 (1 event), Okmok in 2008 (1 sustained event), Kasatochi in 2008 (5 events), and Redoubt in 2009 (over 30 events). Pressures up to 6 Pa have been recorded for the largest Redoubt event at a distance of 547 km from the array, and 1.2 Pa for the largest Kasatochi event at a distance of 2104 km. We determined reduced pressures (equivalent pressure at 1 km assuming 1/r decay) and find that Kasatochi exceeds 2500 Pa and Redoubt 1600 Pa. The smaller explosive eruptions at Augustine yield reduced pressures of 40 to 300 Pa. There is reasonable correlation between measured pressures and signal durations and the ash cloud heights and tephra volumes, hence the infrasound data are useful for hazard assessment. However, the long travel times (3 sec per km) suggest that infrasound array data arrive too late for primary detection but are good for estimating other attributes such as size. Infrasound data may also be combined with seismic data to determine the partitioning of energy

  11. Spall Effects on Infrasound Generation

    NASA Astrophysics Data System (ADS)

    Jones, K. R.; Rodgers, A. J.; Whitaker, R. W.; Ezzedine, S. M.; Vorobiev, O.

    2014-12-01

    Spall effects from buried explosions are seen in near-source surface accelerations and depend on explosion yield, emplacement depth-of-burial and material strength. Investigations of infrasound from buried explosions have shown how atmospheric overpressure can be derived from surface acceleration through application of the Rayleigh Integral (Bannister, 1980). Recently, underground chemical explosions as part of the Source Physics Experiment (SPE) at the Nevada National Security Site (NNSS) have been shown to generate spall signatures in local-distance infrasound (Jones et al. 2014). We are investigating the effects of spall on infrasound generation using two approaches. The first approach uses the Rayleigh integral to compute overpressures for buried explosions from synthetic vertical acceleration data at surface ground zero. To obtain the synthetic surface accelerations we use reported models from nuclear explosion studies and systematically vary parameters such as the spall duration, depth of burial and magnitude. The effect on the resulting acoustic waveform shape will be investigated. The second method uses a hydrodynamic approach to more fully characterize the varied parameters to produce the acoustic waveforms. As the spall decreases we find that the acoustic waveform shape changes dramatically. This waveform signature may provide diagnostics on the explosive source and may be a useful metric for underground explosion monitoring. This work was done under award number DE-AC52-06NA25946. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  12. Automated infrasound signal detection algorithms implemented in MatSeis - Infra Tool.

    SciTech Connect

    Hart, Darren

    2004-07-01

    MatSeis's infrasound analysis tool, Infra Tool, uses frequency slowness processing to deconstruct the array data into three outputs per processing step: correlation, azimuth and slowness. Until now, an experienced analyst trained to recognize a pattern observed in outputs from signal processing manually accomplished infrasound signal detection. Our goal was to automate the process of infrasound signal detection. The critical aspect of infrasound signal detection is to identify consecutive processing steps where the azimuth is constant (flat) while the time-lag correlation of the windowed waveform is above background value. These two statements describe the arrival of a correlated set of wavefronts at an array. The Hough Transform and Inverse Slope methods are used to determine the representative slope for a specified number of azimuth data points. The representative slope is then used in conjunction with associated correlation value and azimuth data variance to determine if and when an infrasound signal was detected. A format for an infrasound signal detection output file is also proposed. The detection output file will list the processed array element names, followed by detection characteristics for each method. Each detection is supplied with a listing of frequency slowness processing characteristics: human time (YYYY/MM/DD HH:MM:SS.SSS), epochal time, correlation, fstat, azimuth (deg) and trace velocity (km/s). As an example, a ground truth event was processed using the four-element DLIAR infrasound array located in New Mexico. The event is known as the Watusi chemical explosion, which occurred on 2002/09/28 at 21:25:17 with an explosive yield of 38,000 lb TNT equivalent. Knowing the source and array location, the array-to-event distance was computed to be approximately 890 km. This test determined the station-to-event azimuth (281.8 and 282.1 degrees) to within 1.6 and 1.4 degrees for the Inverse Slope and Hough Transform detection algorithms, respectively, and

  13. Global Infrasound Monitoring of the Atmosphere

    NASA Astrophysics Data System (ADS)

    Bass, Henry

    2003-03-01

    As a signatory to the Comprehensive Nuclear Test Ban Treaty (CTBT), the United States has responsiblity for establishing and operating eight infrasound arrays from Alaska to the Antarctic through the Pacific Basin, and along the U. S. west coast. (In this context, infrasound is defined as acoustic waves in the frequency range 0.02 Hz to 4Hz.) In addition, the U. S. has non-CTBTO infrasound arrays in New Mexico, Utah, Nevada, Wyoming, Texas, and Maryland. The CTBT Office will install and operate an additional 52 states to provide worldwide coverage. This immense array of sensors provides a rare opportunity to study low frequency sound on a global scale. An international community of interested scieintists is beginning to emerge with different interests in the use of data from this global network. Much of the research interest lies in the ability to remotely monitor events of interest. These include volcanoes, severe storms, and bolides. The signals received at the individual stations are strongly dependent on the state of the intervening atmosphere therefore there is an opportunity to use tomography to gain more detailed knowledge of changes in the upper atmosphere. There are still great opportunities to improve the quality of the infrasound stations. Wind noise continues to limit the signal to noise level. Modern signal processing techniques might be used to lower wind noise levels and allow the detection of even weaker signals. Current generation infrasound stations are large and expensive. Reduction in complexity would allow a finer grid of stations and the study of higher frequency signals. There are numerous opportunities for collaborations in the use of this unique data source at the national and international levels. The US Infrasound Team and international collaborators are open to new ideas and colleagues.

  14. The Temporal Morphology of Infrasound Propagation

    NASA Astrophysics Data System (ADS)

    Drob, Douglas P.; Garcés, Milton; Hedlin, Michael; Brachet, Nicolas

    2010-05-01

    Expert knowledge suggests that the performance of automated infrasound event association and source location algorithms could be greatly improved by the ability to continually update station travel-time curves to properly account for the hourly, daily, and seasonal changes of the atmospheric state. With the goal of reducing false alarm rates and improving network detection capability we endeavor to develop, validate, and integrate this capability into infrasound processing operations at the International Data Centre of the Comprehensive Nuclear Test-Ban Treaty Organization. Numerous studies have demonstrated that incorporation of hybrid ground-to-space (G2S) enviromental specifications in numerical calculations of infrasound signal travel time and azimuth deviation yields significantly improved results over that of climatological atmospheric specifications, specifically for tropospheric and stratospheric modes. A robust infrastructure currently exists to generate hybrid G2S vector spherical harmonic coefficients, based on existing operational and emperical models on a real-time basis (every 3- to 6-hours) (D rob et al., 2003). Thus the next requirement in this endeavor is to refine numerical procedures to calculate infrasound propagation characteristics for robust automatic infrasound arrival identification and network detection, location, and characterization algorithms. We present results from a new code that integrates the local (range-independent) τp ray equations to provide travel time, range, turning point, and azimuth deviation for any location on the globe given a G2S vector spherical harmonic coefficient set. The code employs an accurate numerical technique capable of handling square-root singularities. We investigate the seasonal variability of propagation characteristics over a five-year time series for two different stations within the International Monitoring System with the aim of understanding the capabilities of current working knowledge of the

  15. Using large meteoroids as global infrasound reference events

    NASA Astrophysics Data System (ADS)

    Pilger, C.; Ceranna, L.; LE Pichon, A.; Brown, P.

    2015-12-01

    The explosive fragmentation of large meteoroids entering the Earth's atmosphere is one of the strongest sources of infrasonic waves and can be detected by infrasound arrays all over the world. Pressure perturbations of the strongest bolide events were detected at distances of thousands of kilometers, while for the 2013 Chelyabinsk superbolide, arrivals at long orthodrome distances (above 20000 km) and after complete circumnavigations of the globe (up to 87000 km) were recorded. Influence parameters on the detection capability of a single infrasound station on the one hand and of the complete global infrasound network of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) are investigated within this study and applied to a number of strong bolide events of the past 15 years. Potential influences on infrasound detection capability are due to the directivity of the acoustic source energy emission, the long-range ducting via stratosphere and thermosphere and the diurnal change of meteorological parameters and noise conditions at the stations during the signal arrivals. Since infrasound of large bolides has probably the most similar characteristics to an atmospheric nuclear explosion, it can be utilized as reference event for studies on the global performance of the International Monitoring System (IMS) of the CTBTO. Detections and non-detections of bolide infrasound at the more than 40 operational IMS infrasound stations are studied for the estimation of station and network performance and thus verification of nuclear test ban.

  16. The Eyjafjallajökull 2010 eruptions: Correlation study of volcanic tremor and infrasound

    NASA Astrophysics Data System (ADS)

    Jonsdottir, K.; Bean, C.; Vogfjord, K.; Ripepe, M.

    2012-04-01

    Volcanic far-field seismic tremor recorded at 7-20 km from the Eyjafjallajökull 2010 eruptions is investigated. Over a two months period, two very different eruptions occurred separated by 9 km and two days; an effusive flank eruption and later a highly explosive summit eruption. We observed high amplitude seismic tremor during the explosive eruption while the flank eruption produced very low amplitude tremor. Infrasound data collected for a few days during the summit eruption, as well as other data including plume height is also compared to the seismic tremor amplitude. We find that tremor amplitude does not scale with the plume height. However, in line with similar studies, the infrasound data, characterized by pressure pulses from the volcanic explosions, is seen to correlate temporally (0.55-0.6) with the seismic tremor data, characterized by repeating low frequency events. A high correlation in amplitude (0.8) is also found between these datasets. The analysis reveals a time lag of 15-20 seconds, where seismic low frequency events are seen prior to the infrasound events. This is consistent with co-located seismic tremor and infrasound sources at the eruptive crater, and a surface wave velocity of 1350-1500 m/s. Singlestation three component analyses (undertaken for several stations) of the seismic low frequency events further confirms that they contain Rayleigh wave energy.

  17. Contribution of the infrasound technology to characterize large scale atmospheric disturbances and impact on infrasound monitoring

    NASA Astrophysics Data System (ADS)

    Blanc, Elisabeth; Le Pichon, Alexis; Ceranna, Lars; Pilger, Christoph; Charlton Perez, Andrew; Smets, Pieter

    2016-04-01

    The International Monitoring System (IMS) developed for the verification of the Comprehensive nuclear-Test-Ban Treaty (CTBT) provides a unique global description of atmospheric disturbances generating infrasound such as extreme events (e.g. meteors, volcanoes, earthquakes, and severe weather) or human activity (e.g. explosions and supersonic airplanes). The analysis of the detected signals, recorded at global scales and over near 15 years at some stations, demonstrates that large-scale atmospheric disturbances strongly affect infrasound propagation. Their time scales vary from several tens of minutes to hours and days. Their effects are in average well resolved by the current model predictions; however, accurate spatial and temporal description is lacking in both weather and climate models. This study reviews recent results using the infrasound technology to characterize these large scale disturbances, including (i) wind fluctuations induced by gravity waves generating infrasound partial reflections and modifications of the infrasound waveguide, (ii) convection from thunderstorms and mountain waves generating gravity waves, (iii) stratospheric warming events which yield wind inversions in the stratosphere, (iv)planetary waves which control the global atmospheric circulation. Improved knowledge of these disturbances and assimilation in future models is an important objective of the ARISE (Atmospheric dynamics Research InfraStructure in Europe) project. This is essential in the context of the future verification of the CTBT as enhanced atmospheric models are necessary to assess the IMS network performance in higher resolution, reduce source location errors, and improve characterization methods.

  18. Contribution of Infrasound to IDC Reviewed Event Bulletin

    NASA Astrophysics Data System (ADS)

    Bittner, Paulina; Polich, Paul; Gore, Jane; Ali, Sherif Mohamed; Medinskaya, Tatiana; Mialle, Pierrick

    2016-04-01

    Until 2003 two waveform technologies, i.e. seismic and hydroacoustic were used to detect and locate events included in the International Data Centre (IDC) Reviewed Event Bulletin (REB). The first atmospheric event was published in the REB in 2003 but infrasound detections could not be used by the Global Association (GA) Software due to the unmanageable high number of spurious associations. Offline improvements of the automatic processing took place to reduce the number of false detections to a reasonable level. In February 2010 the infrasound technology was reintroduced to the IDC operations and has contributed to both automatic and reviewed IDC bulletins. The primary contribution of infrasound technology is to detect atmospheric events. These events may also be observed at seismic stations, which will significantly improve event location. Examples of REB events, which were detected by the International Monitoring System (IMS) infrasound network were fireballs (e.g. Bangkok fireball, 2015), volcanic eruptions (e.g. Calbuco, Chile 2015) and large surface explosions (e.g. Tjanjin, China 2015). Query blasts and large earthquakes belong to events primarily recorded at seismic stations of the IMS network but often detected at the infrasound stations. Presence of infrasound detection associated to an event from a mining area indicates a surface explosion. Satellite imaging and a database of active mines can be used to confirm the origin of such events. This presentation will summarize the contribution of 6 years of infrasound data to IDC bulletins and provide examples of events recorded at the IMS infrasound network. Results of this study may help to improve location of small events with observations on infrasound stations.

  19. Antarctic Atmospheric Infrasound.

    DTIC Science & Technology

    1981-11-30

    A summary is given of the project chronology and the reports describing our research in Antarctic Atmospheric infrasound. Analysis of selected infrasonic signals is discussed and a list is given of all infrasonic waves received on the digital system with correlation coefficient greater than 0.6. (Author)

  20. Detection and interpretation of seismoacoustic events at German infrasound stations

    NASA Astrophysics Data System (ADS)

    Pilger, Christoph; Koch, Karl; Ceranna, Lars

    2016-04-01

    Three infrasound arrays with collocated or nearby installed seismometers are operated by the Federal Institute for Geosciences and Natural Resources (BGR) as the German National Data Center (NDC) for the verification of the Comprehensive Nuclear-Test-Ban Treaty (CTBT). Infrasound generated by seismoacoustic events is routinely detected at these infrasound arrays, but air-to-ground coupled acoustic waves occasionally show up in seismometer recordings as well. Different natural and artificial sources like meteoroids as well as industrial and mining activity generate infrasonic signatures that are simultaneously detected at microbarometers and seismometers. Furthermore, many near-surface sources like earthquakes and explosions generate both seismic and infrasonic waves that can be detected successively with both technologies. The combined interpretation of seismic and acoustic signatures provides additional information about the origin time and location of remote infrasound events or about the characterization of seismic events distinguishing man-made and natural origins. Furthermore, seismoacoustic studies help to improve the modelling of infrasound propagation and ducting in the atmosphere and allow quantifying the portion of energy coupled into ground and into air by seismoacoustic sources. An overview of different seismoacoustic sources and their detection by German infrasound stations as well as some conclusions on the benefit of a combined seismoacoustic analysis are presented within this study.

  1. Monitoring the Earth's Atmosphere with the Global IMS Infrasound Network

    NASA Astrophysics Data System (ADS)

    Brachet, Nicolas; Brown, David; Mialle, Pierrick; Le Bras, Ronan; Coyne, John; Given, Jeffrey

    2010-05-01

    , they represent valuable data for other civil applications like monitoring of natural hazards (volcanic activity, storm tracking) and climate change. Non-noise detections are used in network processing at the IDC along with seismic and hydroacoustic technologies. The arrival phases detected on the three waveform technologies may be combined and used for locating events in an automatically generated bulletin of events. This automatic event bulletin is routinely reviewed by analysts during the interactive review process. However, the fusion of infrasound data with the other waveform technologies has only recently (in early 2010) become part of the IDC operational system, after a software development and testing period that began in 2004. The build-up of the IMS infrasound network, the recent developments of the IDC infrasound software, and the progress accomplished during the last decade in the domain of real-time atmospheric modelling have allowed better understanding of infrasound signals and identification of a growing data set of ground-truth sources. These infragenic sources originate from natural or man-made sources. Some of the detected signals are emitted by local or regional phenomena recorded by a single IMS infrasound station: man-made cultural activity, wind farms, aircraft, artillery exercises, ocean surf, thunderstorms, rumbling volcanoes, iceberg calving, aurora, avalanches. Other signals may be recorded by several IMS infrasound stations at larger distances: ocean swell, sonic booms, and mountain associated waves. Only a small fraction of events meet the event definition criteria considering the Treaty verification mission of the Organization. Candidate event types for the IDC Reviewed Event Bulletin include atmospheric or surface explosions, meteor explosions, rocket launches, signals from large earthquakes and explosive volcanic eruptions.

  2. Infrasound absorption by atmospheric clouds

    NASA Astrophysics Data System (ADS)

    Baudoin, Michael; Coulouvrat, Francois; Thomas, Jean-Louis

    2010-05-01

    A model is developed for the absorption of infrasound by atmospheric clouds made of a suspension of liquid water droplets within a gaseous mixture of water vapor and air. The model is based on the work of D.A. Gubaidullin and R.I. Nigmatulin [Int. J. Multiphase Flow, 26, 207-228, 2000], which is applied to atmospheric clouds. Three physical mechanisms are included : unsteady viscous drag associated with momentum transfers due to the translation of water droplets, unsteady thermal transfers between the liquid and gaseous phases, and mass transfers due to the evaporation or condensation of the water phase. For clouds, in the infrasonic frequency range, phase changes are the dominant mechanisms (around 1 Hz), while viscous and heat transfers become significant only around 100 Hz. Mass transfers involve two physical effects : evaporation and condensation of the water phase at the droplet surface, and diffusion of the water vapor within the gaseous phase. The first one is described through the Hertz-Knudsen-Langmuir theory based on kinetic theory. It involves a little known coefficient known as coefficient of accommodation. The second one is the classical Fick diffusion. For clouds, and unless the coefficient of accommodation is very small (far from the generally recommended value is close to one), diffusion is the main limiting effects for mass transfers. In a second stage, the sound and infrasound absorption is evaluated for various typical clouds up to about 4 km altitude. Above this altitude, the ice content of clouds is dominant compared to their water content, and the present model is not applicable. Cloud thickness, water content, and droplets size distribution are shown to be the major factors influencing the infrasound absorption. A variety of clouds have been analyzed. In most cases, it is shown that infrasound absorption within clouds is several orders larger than classical absorption (due to molecular relaxation of nitrogen and oxygen molecules in presence

  3. Infrasound ray tracing models for real events

    NASA Astrophysics Data System (ADS)

    Averbuch, Gil; Applbaum, David; Price, Colin; Ben Horin, Yochai

    2015-04-01

    's height or the sprite's most energetic part. Even though atmospheric wind has a strong influence on infrasound wave propagation, our estimation is that for high altitude sources, extreme weather in the troposphere below has low impact on the trajectories of the waves.

  4. Study of the wind velocity-layered structure in the stratosphere, mesosphere, and lower thermosphere by using infrasound probing of the atmosphere

    NASA Astrophysics Data System (ADS)

    Chunchuzov, I.; Kulichkov, S.; Perepelkin, V.; Popov, O.; Firstov, P.; Assink, J. D.; Marchetti, E.

    2015-09-01

    The wind velocity structure in the upper stratosphere, mesosphere, and lower thermosphere (MLT) is studied with the recently developed method of infrasound probing of the atmosphere. The method is based on the effect of infrasound scattering from highly anisotropic wind velocity and temperature inhomogeneities in the middle and upper atmosphere. The scattered infrasound field propagates in the acoustic shadow zones, where it is detected by microbarometers. The vertical profiles of the wind velocity fluctuations in the upper stratosphere (30-52 km) and MLT (90-140 km) are retrieved from the waveforms and travel times of the infrasound signals generated by explosive sources such as volcanoes and surface explosions. The fine-scale wind-layered structure in these layers was poorly observed until present time by other remote sensing methods, including radars and satellites. It is found that the MLT atmospheric layer (90-102 km) can contain extremely high vertical gradients of the wind velocity, up to 10 m/s per 100 m. The effect of a fine-scale wind velocity structure on the waveforms of infrasound signals is studied. The vertical wave number spectra of the retrieved wind velocity fluctuations are obtained for the upper stratosphere. Despite the difference in the locations of the explosive sources all the obtained spectra show the existence of high vertical wave number spectral tail with a -3 power law decay. The obtained spectral characteristics of the wind fluctuations are necessary for improvement of gravity wave drag parameterizations for numerical weather forecast.

  5. Incorporating numerical modelling into estimates of the detection capability of the IMS infrasound network

    NASA Astrophysics Data System (ADS)

    Le Pichon, A.; Ceranna, L.

    2011-12-01

    To monitor compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT), a dedicated International Monitoring System (IMS) is being deployed. Recent global scale observations recorded by this network confirm that its detection capability is highly variable in space and time. Previous studies estimated the radiated source energy from remote observations using empirical yield-scaling relations which account for the along-path stratospheric winds. Although the empirical wind correction reduces the variance in the explosive energy versus pressure relationship, strong variability remains in the yield estimate. Today, numerical modelling techniques provide a basis to better understand the role of different factors describing the source and the atmosphere that influence propagation predictions. In this study, the effects of the source frequency and the stratospheric wind speed are simulated. In order to characterize fine-scale atmospheric structures which are excluded from the current atmospheric specifications, model predictions are further enhanced by the addition of perturbation terms. Thus, a theoretical attenuation relation is developed from massive numerical simulations using the Parabolic Equation method. Compared with previous studies, our approach provides a more realistic physical description of infrasound propagation. We obtain a new relation combining a near-field and far-field term which account for the effects of both geometrical spreading and dissipation on the pressure wave attenuation. By incorporating real ambient infrasound noise at the receivers which significantly limits the ability to detect and identify signals of interest, the minimum detectable source amplitude can be derived in a broad frequency range. Empirical relations between the source spectrum and the yield of explosions are used to infer detection thresholds in tons of TNT equivalent. In the context of the future verification of the CTBT, the obtained attenuation relation quantifies

  6. Infrasound monitoring, acoustic-gravity waves and global atmospheric dynamics

    NASA Astrophysics Data System (ADS)

    Blanc, E.; Le Pichon, A.; Ceranna, L.; Farges, T.

    2008-12-01

    For the verification of the Comprehensive nuclear Test Ban Treaty, the International Monitoring System has been developed. As part of this system, the infrasound network provides an unique opportunity to monitor continuously pressure waves in the atmosphere. Such infrasonic waves propagate in the channel formed by the temperature and wind gradients of the atmosphere. Long term observations provide information about the evolution of the propagation conditions and then of atmospheric parameters. The monitoring of continuous sources, as ocean swell, gives the characteristics of the stratospheric wave channel submitted to stratospheric warming effects. Large scale gravity waves, which are also observed by the network, produce a forcing of the stratosphere at low and middle latitudes and long-lived changes in the stratospheric circulation towards high latitudes, leading to fluctuations in the strength of the polar vortex. These fluctuations move down to the lower stratosphere with possible effects on the tropospheric temperature. Gravity wave monitoring in Antarctica reveals a gravity wave system probably related to the wind effect over mountains. At mid latitudes an additional main sources of disturbances is the thunderstorm activity. The infrasound monitoring system allows a better knowledge of the atmospheric wave systems and of the dynamics of the atmosphere. In return this better knowledge of the wave systems allow a better identification of the possible explosion signals in the background of the atmospheric waves and then to improve the discrimination methods

  7. Antarctic Atmospheric Infrasound.

    DTIC Science & Technology

    1986-11-01

    system. These are microbaroms, aurural infrasonic waves, mountain associated infrasound, Mount Erebus eruptive events, and signals related to large...array. Mount Erebus is an active volcano located only fifteen miles from the Windless Bight array. Frequent mini-eruptions from the lava lake at the...MAX, Velocity MIN & MAX, and Start & Stop. To produce a listing of all events that were caused by Mount Erebus on the tape: Choose the T array, and

  8. Sayarim Infrasound Calibration Explosion provides first GT0 dataset for CTBTO

    NASA Astrophysics Data System (ADS)

    Gitterman, Yefim

    2010-05-01

    The large-scale calibration explosion of about 82 tons of HE explosives, assembled as a pyramid on the soft sediment surface, was successfully conducted by the Geophysical Institute of Israel at Sayarim Military Range on 26 August 2009. High-pressure values, measured in the range 200-600 m, were higher than predicted, whereas the created crater and seismic magnitude were smaller than expected for this on-surface charge. These results confirm that the used explosives, charge design and upward detonation provided the necessary explosion energy generation and partition: maximum of energy to the atmosphere and minimum to the ground. The high-pressure observations were utilized for estimation of the important Ground Truth parameter - TNT equivalent yield of about 0.1 kT (based on positive impulse in air-shock wave). Thus the Sayarim Explosion provided the first full GT0 source dataset for on-surface large-scale explosions, recorded by infrasound stations of International Monitoring System (IMS). Infrasound signals were well observed at distances up to 3,500 km, at numerous portable and permanent stations in Israel, Mediterranean countries and north-central Europe, including two IMS stations I26DE and I48TN and two portable arrays in Austria and Northern Italy deployed by the CTBTO team. Obtained records were used for analysis of infrasound signal propagation, source location and yield estimation, and comparison with GT0 source parameters.

  9. Capability of the CTBT infrasound stations detecting the 2013 Russian fireball

    NASA Astrophysics Data System (ADS)

    Pilger, Christoph; Ceranna, Lars; Ross, J. Ole; Le Pichon, Alexis; Mialle, Pierrick; Garces, Milton

    2015-04-01

    The explosive fragmentation of the 2013 Chelyabinsk meteorite generated a large airburst with an equivalent yield of 500 kT TNT. It is the most energetic event recorded by the infrasound component of the CTBT-IMS, globally detected by 20 out of 42 operational stations. This study performs a station-by-station estimation of the IMS detection capability to explain infrasound detections and non-detections from short to long distances, using the Chelyabinsk meteorite as global reference event. Investigated parameters influencing the detection capability are the directivity of the line source signal, the ducting of acoustic energy and the individual noise conditions at each station. Findings include a clear detection preference for stations perpendicular to the meteorite trajectory, even over large distances. Only a weak influence of stratospheric ducting is observed for this low-frequency case. Furthermore, a strong dependence on the diurnal variability of background noise levels at each station is observed, favoring nocturnal detections.

  10. IDC infrasound analysis of the 15 February 2013 Chelyabinsk fireball

    NASA Astrophysics Data System (ADS)

    Mialle, P.; Bittner, P.; Brown, D.; Polich, P.; Gore, J.

    2013-12-01

    The first atmospheric event built only from infrasound arrivals was reported in the Reviewed Event Bulletin (REB) of the International Data Centre (IDC) of the Comprehensive Nuclear Test Ban Treaty Organization (CTBTO) in 2003. In the last decade, 45 infrasound stations from the International Monitoring System (IMS) have been installed and are transmitting data to the IDC. In early 2010 the IDC began routine automatic processing of infrasound data reviewed by interactive analysis; the detected and located events are now systematically included in the REB. This study focuses on a major infragenic event that occurred in February 2013 and was thoroughly analyzed at the IDC. On February 15 a fireball in the Chelyabinsk region (Russia) was observed generating infrasound waves that were recorded by 20 infrasound IMS stations globally spread from Greenland to Antarctica. Chronology of the analysis and specificities of this event will be introduced. This event is the largest ever recorded by the infrasound component of the IMS network. Related seismic observations were also found.

  11. Inferring atmospheric weather conditions in volcanic environments using infrasound

    NASA Astrophysics Data System (ADS)

    Ortiz, H. D.; Johnson, J. B.; Ruiz, M. C.

    2015-12-01

    We use infrasound produced by Tungurahua Volcano (Ecuador) to infer local time-varying atmospheric conditions, which can be used to improve gas flux measurements and tephra dispersal modeling. Physical properties of the atmosphere, including wind and temperature (which controls adiabatic sound speed), can be quantified by studying the travel times of acoustic waves produced during volcanic activity. The travel times between Tungurahua's vent and five infrasound stations located in a network configuration over an area of 90 km2 were used in this study. We are able to quantify the arrival time differences of acoustic waves for ten unique station pairs and use this information to model the average speed of sound between source and receiver. To identify what parameters best fit the observed arrival times, we perform a grid search for a homogeneous two-dimensional wind velocity as well as for air temperature. Due to travel time dependence on the specific path taken by waves, we account for topography using a 5 meter resolution digital elevation model of Tungurahua. To investigate the time-varying atmospheric structure we use data recorded at Tungurahua volcano, during a strombolian eruptive phase in August 2012, however the methodology can be applied to continuous network infrasound data collected since July 2006 as part of the Japanese-Ecuadorian Cooperation Project: "Enhancement of the Volcano Monitoring Capacity in Ecuador". We propose that the computation of wind velocities will help to improve gas flux measurements that are based on remote sensing techniques like Differential Optical Absorption Spectroscopy (DOAS), resulting in better estimates of sulfur fluxes that can then be related to magma fluxing into the volcanic system. Further, wind field quantification close to the volcano can improve numerical models that are used to forecast tephra deposits, thereby helping to mitigate their effect on inhabitants, infrastructure, livestock, and crops.

  12. Experimental Infrasound Studies in Nevada

    NASA Astrophysics Data System (ADS)

    Herrin, E. T.; Negraru, P. T.; Golden, P.; Williams, A.

    2009-12-01

    An experimental propagation study was carried out in Nevada in June 2009 on Julian days 173-177. During this field experiment we deployed 16 single channel digital infrasound recorders to monitor the munitions disposal activities near Hawthorne, NV. The sensors were deployed in a single line and placed approximately 12 km apart at distances ranging from 2 to 177 km. A four element semi-permanent infrasound array named FNIAR was installed approximately 154 km north of the detonation site in line with the individual temporary recorders. Tropospheric arrivals were observed during all days of the experiment, but during day 176 the observed arrivals had very large amplitudes. A large signal was observed at 58 km from the detonation site with amplitude as large as 4 Pascals, while at 94 km no signal was observed. At FNIAR the amplitude of the tropospheric arrival was 1 Pascal. During this day meteorological data acquired in the propagation path showed a strong jet stream to the north. On day 177 we were not able to identify tropospheric arrivals beyond 34 km, but at stations beyond 152 km we observed stratospheric arrivals. Continuous monitoring of these signals at FNIAR shows that stratospheric arrivals are the most numerous. In a two month period, from 06/15/2009 to 08/15/2009 there were 35 operational days at the Hawthorne disposal facility resulting in 212 explosions with known origin times. Based on the celerity values there were 115 explosions that have only stratospheric arrivals (celerities of 300-275 m/s), 72 explosions with both tropospheric (celerities above 330 m/s) and stratospheric arrivals, 20 explosions that were not detected and five explosions that have only tropospheric arrivals.

  13. USGS VDP Infrasound Sensor Evaluation

    SciTech Connect

    Slad, George William; Merchant, Bion J.

    2016-10-01

    Sandia National Laboratories has tested and evaluated two infrasound sensors, the model VDP100 and VDP250, built in-house at the USGS Cascades Volcano Observatory. The purpose of the infrasound sensor evaluation was to determine a measured sensitivity, self-noise, dynamic range and nominal transfer function. Notable features of the VDP sensors include novel and durable construction and compact size.

  14. Evaluation of Infrasound and Strobe Lights to Elicit Avoidance Behavior in Juvenile Salmon and Char.

    SciTech Connect

    Mueller, Robert, P.; Neitzel, Duane A.; Amidan, Brett G.

    1999-02-01

    Experimental tests were conducted using hatchery reared and wild juvenile chinook salmon Oncorhynchus tshawytscha, eastern brook trout Salvelinus fontinalis, and rainbow trout O. mykiss to determine specific behavior responses to infrasound (<20 Hz) and flashing strobe lights. Caged fish were acclimated in a static test tank and their behavior was recorded using low light cameras. Species specific behavior was characterized by measuring movements of the fish within the cage as well as observing startle and habituation responses. Wild chinook salmon (40-45 mm) and hatchery reared chinook salmon (45-50mm) exhibited avoidance responses when initially exposed to a 10 Hz volume displacement source. Rainbow and eastern brook trout (25-100 mm) did not respond with avoidance or other behaviors to infrasound. Habituation to the infrasound source was evident for chinook salmon during repeated exposures. Wild and hatchery chinook displayed a higher proportion of movement during the initial exposures to infrasound when the acclimation period in the test tank was 2-3 h as compared to a 12-15 h acclimation period. A flashing strobe light produced higher and more consistent movement rates in wild chinook (60% of the tests); hatchery reared chinook salmon (50%) and rainbow trout (80%). No measurable movement or other responses was observed for eastern brook trout. Little if any habituation was observed during repeated exposures to strobe lights. Results from this study indicate that consistent repeatable responses can be elicited from some fish using high intensity strobe lights under a controlled laboratory testing. The specific behaviors observed in these experiments might be used to predict how fish might react to low frequency sound and strobe lights in a screening facility. Because sub-yearling salmonids and resident species are susceptible from becoming entrained at water diversion structures we conducted tests in conjunction with our evaluation of juvenile fish screening

  15. Sayarim Infrasound Calibration Explosion: Near-Source and Local Observations and Yield Estimation

    DTIC Science & Technology

    2010-09-01

    of large-scale explosions on soft soil (Adushkin and Khristoforov , 2004): R = 3.36W0.336; H = 1.78W0.316 , (1) where W is TNT equivalent... Khristoforov (2004). Craters of large-scale surface explosions, Combust, Explo. Shock Waves 40: 674–678. Bowman, J. R., H. Israelsson, G. Shields, M

  16. The case for infrasound as the long-range map cue in avian navigation

    USGS Publications Warehouse

    Hagstrum, J.T.

    2007-01-01

    Of the various 'map' and 'compass' components of Kramer's avian navigational model, the long-range map component is the least well understood. In this paper atmospheric infrasounds are proposed as the elusive longrange cues constituting the avian navigational map. Although infrasounds were considered a viable candidate for the avian map in the 1970s, and pigeons in the laboratory were found to detect sounds at surprisingly low frequencies (0.05 Hz), other tests appeared to support either of the currently favored olfactory or magnetic maps. Neither of these hypotheses, however, is able to explain the full set of observations, and the field has been at an impasse for several decades. To begin, brief descriptions of infrasonic waves and their passage through the atmosphere are given, followed by accounts of previously unexplained release results. These examples include 'release-site biases' which are deviations of departing pigeons from the homeward bearing, an annual variation in homing performance observed only in Europe, difficulties orienting over lakes and above temperature inversions, and the mysterious disruption of several pigeon races. All of these irregularities can be consistently explained by the deflection or masking of infrasonic cues by atmospheric conditions or by other infrasonic sources (microbaroms, sonic booms), respectively. A source of continuous geographic infrasound generated by atmosphere-coupled microseisms is also proposed. In conclusion, several suggestions are made toward resolving some of the conflicting experimental data with the pigeons' possible use of infrasonic cues.

  17. Overview of the 2009 and 2011 Sayarim Infrasound Calibration Experiments

    NASA Astrophysics Data System (ADS)

    Fee, David; Waxler, Roger; Assink, Jelle; Gitterman, Yefim; Given, Jeffrey; Coyne, John; Mialle, Pierrick; Garces, Milton; Drob, Douglas; Kleinert, Dan; Hofstetter, Rami; Grenard, Patrick

    2013-06-01

    Three large-scale infrasound calibration experiments were conducted in 2009 and 2011 to test the International Monitoring System (IMS) infrasound network and provide ground truth data for infrasound propagation studies. Here we provide an overview of the deployment, detonation, atmospheric specifications, infrasound array observations, and propagation modeling for the experiments. The experiments at the Sayarim Military Range, Israel, had equivalent TNT yields of 96.0, 7.4, and 76.8 t of explosives on 26 August 2009, 24 January 2011, and 26 January 2011, respectively. Successful international collaboration resulted in the deployment of numerous portable infrasound arrays in the region to supplement the IMS network and increase station density. Infrasound from the detonations is detected out to ~3500 km to the northwest in 2009 and ~6300 km to the northeast in 2011, reflecting the highly anisotropic nature of long-range infrasound propagation. For 2009, the moderately strong stratospheric wind jet results in a well-predicted set of arrivals at numerous arrays to the west-northwest. A second set of arrivals is also apparent, with low celerities and high frequencies. These arrivals are not predicted by the propagation modeling and result from unresolved atmospheric features. Strong eastward tropospheric winds (up to ~70 m/s) in 2011 produce high-amplitude tropospheric arrivals recorded out to >1000 km to the east. Significant eastward stratospheric winds (up to ~80 m/s) in 2011 generate numerous stratospheric arrivals and permit the long-range detection (i.e., >1000 km). No detections are made in directions opposite the tropospheric and stratospheric wind jets for any of the explosions. Comparison of predicted transmission loss and observed infrasound arrivals gives qualitative agreement. Propagation modeling for the 2011 experiments predicts lower transmission loss in the direction of the downwind propagation compared to the 2009 experiment, consistent with the

  18. Comparison of seismic and infrasound wave fields generated by snow avalanches

    NASA Astrophysics Data System (ADS)

    Suriñach, Emma; Tapia, Mar; Pérez-Guillén, Cristina; Khazaradze, Giorgi; Roig, Pere

    2016-04-01

    Snow avalanches are a source of waves that are transmitted through the ground and the air. These wave fields are detected by seismic and infrasound sensors. During the winter seasons 2008 -2016, a good quality database of avalanches was obtained at the VdlS test site with an accurate instrumentation. These avalanches were both natural and artificially triggered and were of varying types and sizes. Distances involved were 0.5 -3 km. Seismic signals were acquired using three seismometers (3-components, 1Hz) spaced 600 m apart along the avalanche track. One infrasound sensor (0.1Hz) and one seismometer (3-components, 1Hz) were placed one next to the other with a common base of time on the slope opposite the path. The database obtained enables us to compare the different signals generated. Differences in the frequency content and shape of the signals depending on the type and size of the avalanche are detected. A clear evolution of the recorded seismic signals along the path is observed. The cross correlation of the infrasound and seismic signals generated by the avalanches allows us to determine different characteristics for powder, transitional and wet avalanches concerning their wave fields. The joint analysis of infrasound and seismic waves enables us to obtain valuable information about the internal parts of the avalanche as a source of each wave field. This study has repercussions on avalanche dynamics and on the selection of the appropriate avalanche detection system. This study is supported by the Spanish Ministry of Science and Innovation project CHARMA: CHAracterization and ContRol of MAss Movements. A Challenge for Geohazard Mitigation (CGL2013-40828-R), and RISKNAT group (2014GR/1243).

  19. Infrasound from the 2007 fissure eruptions of Kīlauea Volcano, Hawai'i

    USGS Publications Warehouse

    Fee, D.; Garces, M.; Orr, T.; Poland, M.

    2011-01-01

    Varied acoustic signals were recorded at Kīlauea Volcano in mid-2007, coincident with dramatic changes in the volcano's activity. Prior to this time period, Pu'u 'Ō'ō crater produced near-continuous infrasonic tremor and was the primary source of degassing and lava effusion at Kīlauea. Collapse and draining of Pu'u 'Ō'ō crater in mid-June produced impulsive infrasonic signals and fluctuations in infrasonic tremor. Fissure eruptions on 19 June and 21 July were clearly located spatially and temporally using infrasound arrays. The 19 June eruption from a fissure approximately mid-way between Kīlauea's summit and Pu'u 'O'o produced infrasound for ~30 minutes-the only observed geophysical signal associated with the fissure opening. The infrasound signal from the 21 July eruption just east of Pu'u 'Ō'ō shows a clear azimuthal progression over time, indicative of fissure propagation over 12.9 hours. The total fissure propagation rate is relatively slow at 164 m/hr, although the fissure system ruptured discontinuously. Individual fissure rupture times are estimated using the acoustic data combined with visual observations.

  20. Infrasound Sensor Calibration and Response

    DTIC Science & Technology

    2012-09-01

    functions with faster rise times. SUMMARY We have documented past work on the determination of the calibration constant of the LANL infrasound sensor...Monitoring Technologies 735 Report Documentation Page Form ApprovedOMB No. 0704-0188 Public reporting burden for the collection of information is estimated...National Laboratory ( LANL ) has operated an infrasound sensor calibration chamber that operates over a frequency range of 0.02 to 4 Hz. This chamber has

  1. Mobile Source Observation Database (MSOD)

    EPA Pesticide Factsheets

    The Mobile Source Observation Database (MSOD) is a relational database developed by the Assessment and Standards Division (ASD) of the U.S. EPA Office of Transportation and Air Quality (formerly the Office of Mobile Sources).

  2. On the fingerprint of ssw events in infrasound recordings at IMS stations

    NASA Astrophysics Data System (ADS)

    Ceranna, L.; Le Pichon, A.; Pilger, C.; Ross, O.

    2013-12-01

    It has been recently shown that sudden stratospheric warming (ssw) events have an impact on the detection of coherent infrasonic waves at dedicated arrays (e.g., Evers & Siegmund, 2009). During ssw events the polar vortex of prevailing stratospheric westerly winds in a winter hemisphere abruptly slows down or even reverses its direction along with an increase of stratospheric temperatures up to several tens of °C. Since infrasound arrays are mostly recording signals ducted in stratospheric wave-guides, such antennas are sensitive to changes in effective sound speed profiles - temperature plus wind speed in direction of propagation. Considering continuous infrasonic waves emitted by ocean swell (microbaroms), volcanoes or even anthropogenic sources as flares, a gap or a change in the back-azimuth of these detected signals can be observed at arrays. For the compliances with the verification of the Comprehensive Nuclear-Test-Ban Treaty a global network of 60 infrasound stations is under construction as a part of the International Monitoring System (IMS); whereas 45 have already been installed. Analysis of waveform data recorded at these stations has demonstrated the capability of infrasound as a supplementary tool for remote sensing of the atmosphere. In our study we compare the re-analysis, using PMCC, of more than five years of continuous data at all available sites (see Matoza et al., 2013) with atmospheric descriptions provided by the EMCWF. We present a synoptic view of the fingerprint of ssw events in detection of coherent signals at IMS infrasound stations both on northern and southern hemisphere, covering the full latitude range from Antarctica to Greenland.

  3. On the fingerprint of ssw events in infrasound recordings at IMS stations

    NASA Astrophysics Data System (ADS)

    Ceranna, Lars; Pilger, Christoph; Ross, Ole; Le Pichon, Alexis

    2013-04-01

    It has been recently shown that sudden stratospheric warming (ssw) events have an impact on the detection of coherent infrasonic waves at dedicated arrays (e.g., Evers & Siegmund, 2009). During ssw events the polar vortex of prevailing stratospheric westerly winds in a winter hemisphere abruptly slows down or even reverses its direction along with an increase of stratospheric temperatures up to several tens of °C. Since infrasound arrays are mostly recording signals ducted in stratospheric wave-guides, such antennas are sensitive to changes in effective sound speed profiles - temperature plus wind speed in direction of propagation. Considering continuous infrasonic waves emitted by ocean swell (microbaroms), volcanoes or even anthropogenic sources as flares, a gap or a change in the back-azimuth of these detected signals can be observed at arrays. For the compliances with the verification of the Comprehensive Nuclear-Test-Ban Treaty a global network of 60 infrasound stations is under construction as a part of the International Monitoring System (IMS); whereas 45 have already been installed. Analysis of waveform data recorded at these stations has demonstrated the capability of infrasound as a supplementary tool for remote sensing of the atmosphere. In our study we compare the re-analysis, using PMCC, of more than five years of continuous data at all available sites (see Matoza et al., 2013) with atmospheric descriptions provided by the EMCWF. We present a synoptic view of the fingerprint of ssw events in detection of coherent signals at IMS infrasound stations both on northern and southern hemisphere, covering the full latitude range from Antarctica to Greenland.

  4. Characteristics and Applications of a High Performance, Miniaturized, Infrasound Sensor

    NASA Astrophysics Data System (ADS)

    Rothman, J. L.; Marriott, D. A.

    2015-12-01

    Infrasound Sensors have been used for many years to monitor a large number of geophysical phenomena and manmade sources. Due to their large size and power consumption these sensors have typically been deployed in fixed arrays, portable arrays have required trucks to transport the sensors and support equipment. A high performance, miniaturized, infrasound microphone has been developed to enable mobile infrasound measurements that would otherwise be impractical. The new device is slightly larger than a hockey puck, weighs 200g, and consumes less than 150mW. The sensitivity is 0.4V/Pa and self noise at 1Hz is less than 0.63μPa²/Hz. The characteristics were verified using a calibrator tracable to the Los Alamos calibration chamber. Field tests have demonstrated the performance is comparable to a Chaparral model 25. Applications include man portable arrays, mobile installations, and UAV based measurements.

  5. Detection of atmospheric infrasound with a ring laser interferometer

    NASA Astrophysics Data System (ADS)

    Dunn, Robert W.; Meredith, John A.; Lamb, Angela B.; Kessler, Elijah G.

    2016-09-01

    In this paper, the results from using a large active ring laser interferometer as an infrasound detector are presented. On April 27, 2014, an EF4 tornado struck Central Arkansas and passed within 21 km of the ring laser interferometer. The tornado resulted in 16 fatalities and millions of dollars in damage. Using the ring laser to study the tornado infrasound produced results that qualitatively agree with several findings from a long-term study of weather generated infrasound by the National Oceanic and Atmospheric Administration. A Fast Fourier Transform of the ring laser output revealed a coherent frequency of approximately 0.94 Hz that lasted during the life of the storm. The 0.94 Hz frequency was initially observed 30 min before the funnel was reported on the ground. Infrasound signatures from four separate tornadoes are presented. In each case, coherent infrasound was detected at least 30 min before the tornado was reported on the ground. Examples of the detection of distant coherent acoustic-gravity waves from volcanoes and typhoons are also presented. In addition, buoyancy waves were recorded.

  6. Infrasound from ground to space

    NASA Astrophysics Data System (ADS)

    Bowman, Daniel Charles

    Acoustic detector networks are usually located on the Earth's surface. However, these networks suffer from shortcomings such as poor detection range and pervasive wind noise. An alternative is to deploy acoustic sensors on high altitude balloons. In theory, such platforms can resolve signals arriving from great distances, acquire others that never reach the surface at all, and avoid wind noise entirely. This dissertation focuses on scientific advances, instrumentation, and analytical techniques resulting from the development of such sensor arrays. Results from infrasound microphones deployed on balloon flights in the middle stratosphere are described, and acoustic sources such as the ocean microbarom and building ventilation systems are discussed. Electromagnetic noise originating from the balloon, flight system, and other payloads is shown to be a pervasive issue. An experiment investigating acoustic sensor calibration at low pressures is presented, and implications for high altitude recording are considered. Outstanding challenges and opportunities in sound measurement using sensors embedded in the free atmosphere are outlined. Acoustic signals from field scale explosions designed to emulate volcanic eruptions are described, and their generation mechanisms modeled. Wave forms recorded on sensors suspended from tethered helium balloons are compared with those detected on ground stations during the experiment. Finally, the Hilbert-Huang transform, a high time resolution spectral analysis method for nonstationary and nonlinear time series, is presented.

  7. Detecting blast-induced infrasound in wind noise.

    PubMed

    Howard, Wheeler B; Dillion, Kevin L; Shields, F Douglas

    2010-03-01

    Current efforts seek to monitor and investigate such naturally occurring events as volcanic eruptions, hurricanes, bolides entering the atmosphere, earthquakes, and tsunamis by the infrasound they generate. Often, detection of the infrasound signal is limited by the masking effect of wind noise. This paper describes the use of a distributed array to detect infrasound signals from four atmospheric detonations at White Sands Missile Range in New Mexico, USA in 2006. Three of the blasts occurred during times of low wind noise and were easily observed with array processing techniques. One blast was obscured by high wind conditions. The results of signal processing are presented that allowed localization of the blast-induced signals in the presence of wind noise in the array response.

  8. Hyperion 5113/A Infrasound Sensor Evaluation

    SciTech Connect

    Merchant, Bion John

    2015-09-01

    Sandia National Laboratories has tested and evaluated an infrasound sensor, the 5113/A manufactured by Hyperion. These infrasound sensors measure pressure output by a methodology developed by the University of Mississippi. The purpose of the infrasound sensor evaluation was to determine a measured sensitivity, transfer function, power, self-noise, and dynamic range. The 5113/A infrasound sensor is a new revision of the 5000 series intended to meet the infrasound application requirements for use in the International Monitoring System (IMS) of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO).

  9. Global Infrasound Association Based on Probabilistic Clutter Categorization

    NASA Astrophysics Data System (ADS)

    Arora, N. S.; Mialle, P.

    2015-12-01

    The IDC collects waveforms from a global network of infrasound sensors maintained by the IMS, and automatically detects signal onsets and associates them to form event hypotheses. However, a large number of signal onsets are due to local clutter sources such as microbaroms (from standing waves in the oceans), waterfalls, dams, gas flares, surf (ocean breaking waves) etc. These sources are either too diffuse or too local to form events. Worse still, the repetitive nature of this clutter leads to a large number of false event hypotheses due to the random matching of clutter at multiple stations. Previous studies, for example [1], have worked on categorization of clutter using long term trends on detection azimuth, frequency, and amplitude at each station. In this work we continue the same line of reasoning to build a probabilistic model of clutter that is used as part of NET-VISA [2], a Bayesian approach to network processing. The resulting model is a fusion of seismic, hydro-acoustic and infrasound processing built on a unified probabilistic framework. Notes: The attached figure shows all the unassociated arrivals detected at IMS station I09BR for 2012 distributed by azimuth and center frequency. (The title displays the bandwidth of the kernel density estimate along the azimuth and frequency dimensions).This plot shows multiple micro-barom sources as well as other sources of infrasound clutter. A diverse clutter-field such as this one is quite common for most IMS infrasound stations, and it highlights the dangers of forming events without due consideration of this source of noise. References: [1] Infrasound categorization Towards a statistics-based approach. J. Vergoz, P. Gaillard, A. Le Pichon, N. Brachet, and L. Ceranna. ITW 2011 [2] NET-VISA: Network Processing Vertically Integrated Seismic Analysis. N. S. Arora, S. Russell, and E. Sudderth. BSSA 2013.

  10. Neural network approach to classification of infrasound signals

    NASA Astrophysics Data System (ADS)

    Lee, Dong-Chang

    As part of the International Monitoring Systems of the Preparatory Commissions for the Comprehensive Nuclear Test-Ban Treaty Organization, the Infrasound Group at the University of Alaska Fairbanks maintains and operates two infrasound stations to monitor global nuclear activity. In addition, the group specializes in detecting and classifying the man-made and naturally produced signals recorded at both stations by computing various characterization parameters (e.g. mean of the cross correlation maxima, trace velocity, direction of arrival, and planarity values) using the in-house developed weighted least-squares algorithm. Classifying commonly observed low-frequency (0.015--0.1 Hz) signals at out stations, namely mountain associated waves and high trace-velocity signals, using traditional approach (e.g. analysis of power spectral density) presents a problem. Such signals can be separated statistically by setting a window to the trace-velocity estimate for each signal types, and the feasibility of such technique is demonstrated by displaying and comparing various summary plots (e.g. universal, seasonal and azimuthal variations) produced by analyzing infrasound data (2004--2007) from the Fairbanks and Antarctic arrays. Such plots with the availability of magnetic activity information (from the College International Geophysical Observatory located at Fairbanks, Alaska) leads to possible physical sources of the two signal types. Throughout this thesis a newly developed robust algorithm (sum of squares of variance ratios) with improved detection quality (under low signal to noise ratios) over two well-known detection algorithms (mean of the cross correlation maxima and Fisher Statistics) are investigated for its efficacy as a new detector. A neural network is examined for its ability to automatically classify the two signals described above against clutter (spurious signals with common characteristics). Four identical perceptron networks are trained and validated (with

  11. Global Infrasound Association Based on Probabilistic Clutter Categorization

    NASA Astrophysics Data System (ADS)

    Arora, Nimar; Mialle, Pierrick

    2016-04-01

    The IDC advances its methods and continuously improves its automatic system for the infrasound technology. The IDC focuses on enhancing the automatic system for the identification of valid signals and the optimization of the network detection threshold by identifying ways to refine signal characterization methodology and association criteria. An objective of this study is to reduce the number of associated infrasound arrivals that are rejected from the automatic bulletins when generating the reviewed event bulletins. Indeed, a considerable number of signal detections are due to local clutter sources such as microbaroms, waterfalls, dams, gas flares, surf (ocean breaking waves) etc. These sources are either too diffuse or too local to form events. Worse still, the repetitive nature of this clutter leads to a large number of false event hypotheses due to the random matching of clutter at multiple stations. Previous studies, for example [1], have worked on categorization of clutter using long term trends on detection azimuth, frequency, and amplitude at each station. In this work we continue the same line of reasoning to build a probabilistic model of clutter that is used as part of NETVISA [2], a Bayesian approach to network processing. The resulting model is a fusion of seismic, hydroacoustic and infrasound processing built on a unified probabilistic framework. References: [1] Infrasound categorization Towards a statistics based approach. J. Vergoz, P. Gaillard, A. Le Pichon, N. Brachet, and L. Ceranna. ITW 2011 [2] NETVISA: Network Processing Vertically Integrated Seismic Analysis. N. S. Arora, S. Russell, and E. Sudderth. BSSA 2013

  12. Incorporating numerical modeling into estimates of the detection capability of the IMS infrasound network

    NASA Astrophysics Data System (ADS)

    Le Pichon, A.; Ceranna, L.; Vergoz, J.

    2012-03-01

    To monitor compliance with the Comprehensive Nuclear-Test ban Treaty (CTBT), a dedicated International Monitoring System (IMS) is being deployed. Recent global scale observations recorded by this network confirm that its detection capability is highly variable in space and time. Previous studies estimated the radiated source energy from remote observations using empirical yield-scaling relations which account for the along-path stratospheric winds. Although the empirical wind correction reduces the variance in the explosive energy versus pressure relationship, strong variability remains in the yield estimate. Today, numerical modeling techniques provide a basis to better understand the role of different factors describing the source and the atmosphere that influence propagation predictions. In this study, the effects of the source frequency and the stratospheric wind speed are simulated. In order to characterize fine-scale atmospheric structures which are excluded from the current atmospheric specifications, model predictions are further enhanced by the addition of perturbation terms. A theoretical attenuation relation is thus developed from massive numerical simulations using the Parabolic Equation method. Compared with previous studies, our approach provides a more realistic physical description of long-range infrasound propagation. We obtain a new relation combining a near-field and a far-field term, which account for the effects of both geometrical spreading and absorption. In the context of the future verification of the CTBT, the derived attenuation relation quantifies the spatial and temporal variability of the IMS infrasound network performance in higher resolution, and will be helpful for the design and prioritizing maintenance of any arbitrary infrasound monitoring network.

  13. Stacee Observations of Extragalactic Sources

    NASA Astrophysics Data System (ADS)

    Mukherjee, R.; Boone, L. M.; Bramel, D.; Covault, C. E.; Fortin, P.; Gingrich, D.; Hanna, D.; Hinton, J. A.; Mueller, C.; Ong, R. A.; Ragan, K.; Scalzo, R. A.; Schuette, D. R.; Williams, D. A.

    2002-04-01

    The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) is a ground-based gamma-ray telescope employing the atmospheric Cherenkov technique. STACEE uses 64 large heliostats at a solar research facility near Albuquerque NM, USA, to achieve a gamma-ray energy threshold below traditional imaging telescopes. The full STACEE experiment started regular observations in October, 2001. An earlier version of the experiment using 48 heliostats took data between January and June of 2001. Here we report the results from STACEE observations of extragalactic sources in 2001 and 2002. The sources observed include the active galaxies Markarian 421, Markarian 501, 3C 66A, and W Comae. We also summarize our future observing plan in the context of measuring the absorbtion of high energy emission due to radiation fields at the source, or in intergalactic space.

  14. Infrasound analysis of I18DK, northwest Greenland

    NASA Astrophysics Data System (ADS)

    Evers, L. G.; Weemstra, C.

    2010-12-01

    Within the scope of the Comprehensive Nuclear-Test-Ban Treaty (CTBT), four methods are used to verify the treaty. One of these methods is based on the detection of infrasound waves generated by a nuclear explosion. Seismological, hydroacoustical and radionuclide measurements are also applied. The International Monitoring System (IMS) will consist of 60 infrasound stations of which 35 stations are currently operational. Data obtained from an infrasound station situated on the northwestern shoreline of Greenland is analyzed. This station is operated by Denmark and labeled as I18DK. I18DK is situated in an area which receives an ever increasing attention from a geophysical perspective. I18DK has continuously been operational from April 2003 and onwards. The IMS station is an infrasound array with an aperture of about 1200 meters, where air-pressure fluctuations are recorded by eight microbarometers at a sample-rate of 20 Hz. The infrasonic recordings are filtered between 0.1 & 1.0 and 1.0 & 6.0 Hz. The slowness grid is searched for two different configurations in the higher frequency band. Once using all 8 stations and once only taking into account the 5 center stations. Several different source types are known to generate infrasound, for example, calving of icebergs and glaciers, explosions, earthquakes, oceanic wave-wave interaction, volcanic eruptions and aurora. The challenge is to distinguish between these different source types and use the outcome of the array analysis to better understand these phenomena. The rate of occurrence of icequakes, the calving of glaciers and the variation in extent of the sea ice in this area is of interest in relation to global warming. The processing results of the 1 to 6 Hz band seem to show dominating back-azimuths related to these sources. The glaciers south of I18DK produce significant infrasound during summer time. As well, a direct link can be found between the number of warm days in a year and the number of infrasound

  15. Using Hilbert-Huang Transform (HHT) to Extract Infrasound Generated by the 2013 Lushan Earthquake in China

    NASA Astrophysics Data System (ADS)

    Zhu, X.; Xu, Q.; Liu, H. X.

    2017-03-01

    We applied the Hilbert-Huang transform (HHT) method to extract the infrasound generated by the 2013 Lushan earthquake and its following aftershocks in China from a nearly continuous infrasound recode made 130 km from the earthquake epicenter. An improved STA/LTA algorithm was adopted for detecting the ambient infrasonic events from the data record. A powerful processing technique for non-stationary signal, the HHT, was applied to extract the significant intrinsic mode functions (IMFs) of the infrasonic signal associated with the earthquakes. The features of the extracted IMFs, such as the dominant frequency, the maximum amplitude and the spectral entropy, were investigated using Hilbert spectral analysis. Regression analysis between the maximum amplitude in the infrasound spectra and the magnitudes of the earthquakes was carried out to verify the source of the infrasound events detected. The results demonstrated that the HHT method could successfully identify the infrasound related to the earthquakes.

  16. Volcanic eruption volume flux estimations from very long period infrasound signals

    NASA Astrophysics Data System (ADS)

    Yamada, Taishi; Aoyama, Hiroshi; Nishimura, Takeshi; Iguchi, Masato; Hendrasto, Muhamad

    2017-01-01

    We examine very long period infrasonic signals accompanying volcanic eruptions near active vents at Lokon-Empung volcano in Indonesia, Aso, Kuchinoerabujima, and Kirishima volcanoes in Japan. The excitation of the very long period pulse is associated with an explosion, the emerging of an eruption column, and a pyroclastic density current. We model the excitation of the infrasound pulse, assuming a monopole source, to quantify the volume flux and cumulative volume of erupting material. The infrasound-derived volume flux and cumulative volume can be less than half of the video-derived results. A largely positive correlation can be seen between the infrasound-derived volume flux and the maximum eruption column height. Therefore, our result suggests that the analysis of very long period volcanic infrasound pulses can be helpful in estimating the maximum eruption column height.

  17. Hyperion 5113/GP Infrasound Sensor Evaluation.

    SciTech Connect

    Merchant, Bion J.

    2015-08-01

    Sandia National Laboratories has tested and evaluated an infrasound sensor, the 5113/GP manufactured by Hyperion. These infrasound sensors measure pressure output by a methodology developed by the University of Mississippi. The purpose of the infrasound sensor evaluation was to determine a measured sensitivity, transfer function, power, self-noise, dynamic range, and seismic sensitivity. These sensors are being evaluated prior to deployment by the U.S. Air Force.

  18. MB3a Infrasound Sensor Evaluation.

    SciTech Connect

    Merchant, Bion J.; McDowell, Kyle D.

    2014-11-01

    Sandia National Laboratories has tested and evaluated a new infrasound sensor, the MB3a, manufactured by Seismo Wave. These infrasound sensors measure pressure output by a methodology developed by researchers at the French Alternative Energies and Atomic Energy Commission (CEA) and the technology was recently licensed to Seismo Wave for production and sales. The purpose of the infrasound sensor evaluation was to determine a measured sensitivity, transfer function, power, self-noise, dynamic range, seismic sensitivity, and self- calibration ability. The MB3a infrasound sensors are being evaluated for potential use in the International Monitoring System (IMS) of the Comprehensive Nuclear Test-Ban-Treaty Organization (CTBTO).

  19. Dynamic Modeling of Infrasound Generation from Vulcanian Explosions

    NASA Astrophysics Data System (ADS)

    Watson, L. M.; Dunham, E. M.

    2015-12-01

    Volcano infrasound provides a complementary view of volcanic processes to seismic waves, as the atmosphere exhibits contrasting wave propagation characteristics to the crust. Potential benefits include a more uniform velocity structure, shorter wavelengths enabling better spatial resolution, and lower attenuation improving remote monitoring capabilities. Recent work on volcano infrasound has employed kinematic source descriptions, in terms of such quantities as mass flux for a monopole point source. Such descriptions are quite useful for the inverse problem of inferring mass flux from infrasound data. In this study, we introduce a dynamic source model incorporating the physical processes that determine how the cloud of eruptive gas and ash expands outward to generate the infrasound signal. Our dynamic source model could ultimately be coupled to an unsteady conduit flow model, providing a means to infer more details of the eruption process from recorded infrasound signals. Our model describes a vulcanian eruption where mass is ejected into the atmosphere forming a cloud of gas and ash. Infrasonic acoustic waves are generated by the expansion of the cloud. The model goes beyond linear acoustics by accounting for nonlinear terms in the compressible Euler equations for the surrounding atmosphere. The model presently consists of a system of nonlinear ordinary differential equations, expressing the balance of mass, momentum, and energy, that can be solved for the evolution of the radius of the cloud and pressure and temperature within it. Entrainment and heat exchange with the surrounding atmospheric air can be accounted for. Our analysis is inspired by similar models of underwater explosions (Gilmore, 1952) and seismic air-guns (Ziolkowski, 1970). We aim to use the model to investigate how acoustic signals change when volcano properties, such as vent geometry, are varied. Our longer-term goal is to couple the atmospheric infrasound model presented here to an unsteady

  20. Generating regional infrasound celerity-range models using ground-truth information and the implications for event location

    NASA Astrophysics Data System (ADS)

    Nippress, Alexandra; Green, David N.; Marcillo, Omar E.; Arrowsmith, Stephen J.

    2014-05-01

    Celerity-range models, where celerity is defined as the epicentral distance divided by the total traveltime (similar to the definition of group velocity for dispersed seismic surface waves), can be used for the association of infrasound automatic detections, for event location and for the validation of acoustic propagation simulations. Signals recorded from ground truth events are used to establish celerity-range models, but data coverage is uneven in both space and time. To achieve a high density of regional recordings we use data from USArray seismic stations recording air-to-ground coupled waves from explosions during the summers of 2004-2008 at the Utah Training and Test Range, in the western United States, together with data from five microbarograph arrays at regional distances (<1000 km). We have developed a consistent methodology for analysing the infrasound and seismic data, including choosing filter characteristics from a limited group of two-octave wide filter bands and picking the maximum peak-to-peak arrival. We clearly observe tropospheric, thermospheric and stratospheric arrivals, in agreement with regional ray tracing models. Due to data availability and the dependence of infrasound propagation on the season, we develop three regional celerity-range models for the U.S. summer, with a total of 2211 data picks. The new models suggest event locations using the Geiger method could be improved in terms of both accuracy (up to 80 per cent closer to ground truth) and precision (error ellipse area reduced by >90 per cent) when compared to those estimated using the global International Data Center model, particularly for events where stations detect arrivals at ranges <350 km. Whilst adding data-based prior information into the Bayesian Infrasound Source Localization (BISL) method is also shown to increase precision, to increase accuracy, the parameter space must be expanded to include station-specific celerity distributions.

  1. High Altitude Infrasound Measurements using Balloon-Borne Arrays

    NASA Astrophysics Data System (ADS)

    Bowman, D. C.; Johnson, C. S.; Gupta, R. A.; Anderson, J.; Lees, J. M.; Drob, D. P.; Phillips, D.

    2015-12-01

    For the last fifty years, almost all infrasound sensors have been located on the Earth's surface. A few experiments consisting of microphones on poles and tethered aerostats comprise the remainder. Such surface and near-surface arrays likely do not capture the full diversity of acoustic signals in the atmosphere. Here, we describe results from a balloon mounted infrasound array that reached altitudes of up to 38 km (the middle stratosphere). The balloon drifted at the ambient wind speed, resulting in a near total reduction in wind noise. Signals consistent with tropospheric turbulence were detected. A spectral peak in the ocean microbarom range (0.12 - 0.35 Hz) was present on balloon-mounted sensors but not on static infrasound stations near the flight path. A strong 18 Hz signal, possibly related to building ventilation systems, was observed in the stratosphere. A wide variety of other narrow band acoustic signals of uncertain provenance were present throughout the flight, but were absent in simultaneous recordings from nearby ground stations. Similar phenomena were present in spectrograms from the last balloon infrasound campaign in the 1960s. Our results suggest that the infrasonic wave field in the stratosphere is very different from that which is readily detectable on surface stations. This has implications for modeling acoustic energy transfer between the lower and upper atmosphere as well as the detection of novel acoustic signals that never reach the ground. Our work provides valuable constraints on a proposed mission to detect earthquakes on Venus using balloon-borne infrasound sensors.

  2. An analysis of three new infrasound arrays around Kīlauea Volcano

    USGS Publications Warehouse

    Thelen, Weston A.; Cooper, Jennifer

    2015-01-01

    A network of three new infrasound station arrays was installed around Kīlauea Volcano between July 2012 and September 2012, and a preliminary analysis of open-vent monitoring has been completed by Hawaiian Volcano Observatory (HVO). Infrasound is an emerging monitoring method in volcanology that detects perturbations in atmospheric pressure at frequencies below 20 Hz, which can result from volcanic events that are not always observed optically or thermally. Each array has the capability to detect various infrasound events as small as 0.05 Pa as measured at the array site. The infrasound monitoring network capabilities are demonstrated through case studies of rockfalls, pit collapses, and rise-fall cycles at Halema'uma'u Crater and Pu'u 'Ōʻō.

  3. Infrasound Detection of Rocket Launches

    DTIC Science & Technology

    2000-09-01

    were examined for 14 VAFB launches in 1999 at SGAR (680 km) and DLIAR (1300 km). Detections were seen for a Titan IVB launched 5/22/99 and a Delta II...size. Upper atmospheric wind conditions should have been favorable for several of the detections, however noise levels were often high at SGAR and...phase velocities are consistent with stratospheric propagation and nominal infrasound travel times to SGAR (2340 s) and DLIAR (4440 s). The signals were

  4. Application of a New Infrasound Sensor Technology in a Long Range Infrasound Propagation Experiment

    NASA Astrophysics Data System (ADS)

    Talmadge, C. L.; Waxler, R.; Hetzer, C. H.; Kleniert, D. E., Jr.; Dillion, K.; Assink, J.; Aydin, A.

    2009-12-01

    A low-cost ruggedized infrasound sensor has been developed at the NCPA laboratory of the University of Mississippi for outdoor infrasound measurements. This sensor has similar performance characteristics to other "standard" infrasound sensors, such as the Chaparral 50. A total of 50 sensors were constructed for this experiment, of which 42 were deployed on the Nevada and Utah desert for a period of four months. A long-range infrasound propagation experiment using these sensors was performed during the summer and fall of 2009. Source sizes varied in size from 4, 20 and 80 equivalent tons of TNT. The blasts were carried out typically on the Monday of each week in the afternoon, and were part of a scheduled demolition of first, second and third stages of trident missiles. In addition to a source capture location 23-km south of the site of the blasts, a series of 8 5-element arrays are located to the west of the blast location, at approximate ranges of 180 through 250 km in 10-km steps. Each array consisted of elements at -150-m, -50-m, 0-m, 50-m and 150-m relative to the center of the array along an east-west direction, and all microphones were equipped with 4 50-ft porous hoses connected to the microphone manifold for wind noise suppression. The signals from the microphones were digitized using GPS-synchronized, 24-bit DAQ systems. A Westerly direction for the deployment of the microphones was motivated by the presence of a strong stratospheric duct that persists through the summer months in the northern hemisphere at these latitudes. In this paper, we will discuss feasibility issues related the design of the NCPA microphone that makes possible deployments on these on large scales. Signal to noise issues related to temperature and wind fluctuations will also be discussed. Future plans include a larger scale deployment of several hundred microphones during 2010. We will discuss how the lessons learned from this series of measurements impacts that future deployment.

  5. Infrasound Sensor Models and Evaluations

    SciTech Connect

    KROMER,RICHARD P.; MCDONALD,TIMOTHY S.

    2000-07-31

    Sandia National Laboratories has continued to evaluate the performance of infrasound sensors that are candidates for use by the International Monitoring System (IMS) for the Comprehensive Nuclear-Test-Ban Treaty Organization. The performance criteria against which these sensors are assessed are specified in ``Operational Manual for Infra-sound Monitoring and the International Exchange of Infrasound Data''. This presentation includes the results of efforts concerning two of these sensors: (1) Chaparral Physics Model 5; and (2) CEA MB2000. Sandia is working with Chaparral Physics in order to improve the capability of the Model 5 (a prototype sensor) to be calibrated and evaluated. With the assistance of the Scripps Institution of Oceanography, Sandia is also conducting tests to evaluate the performance of the CEA MB2000. Sensor models based on theoretical transfer functions and manufacturer specifications for these two devices have been developed. This presentation will feature the results of coherence-based data analysis of signals from a huddle test, utilizing several sensors of both types, in order to verify the sensor performance.

  6. Could the IMS Infrasound Stations Support a Global Network of Small Aperture Seismic Arrays?

    NASA Astrophysics Data System (ADS)

    J, Gibbons, Steven; Kværna, Tormod; Mykkeltveit, Svein

    2015-04-01

    find such added capabilities valuable from a national perspective. In addition, the seismic recordings may also help to identify the sources of infrasound signals with consequences for improved event screening and evaluating models of infrasound propagation and atmospheric properties.

  7. Infrasound and the avian navigational map

    USGS Publications Warehouse

    Hagstrum, J.T.

    2001-01-01

    Birds can accurately navigate over hundreds to thousands of kilometres, and use celestial and magnetic compass senses to orient their flight. How birds determine their location in order to select the correct homeward bearing (map sense) remains controversial, and has been attributed to their olfactory or magnetic senses. Pigeons can hear infrasound down to 0??05 Hz, and an acoustic avian map is proposed consisting of infrasonic cues radiated from steep-sided topographic features. The source of these infrasonic signals is microseisms continuously generated by interfering oceanic waves. Atmospheric processes affecting the infrasonic map cues can explain perplexing experimental results from pigeon releases. Moreover, four recent disrupted pigeon races in Europe and the north-eastern USA intersected infrasonic shock waves from the Concorde supersonic transport. Having an acoustic map might also allow clock-shifted birds to test their homeward progress and select between their magnetic and solar compasses.

  8. Assessing and optimizing the performance of infrasound networks to monitor volcanic eruptions

    NASA Astrophysics Data System (ADS)

    Tailpied, Dorianne; Pichon, Alexis Le; Marchetti, Emanuele; Assink, Jelle; Vergniolle, Sylvie

    2016-10-01

    We propose a numerical modeling technique based on a frequency-dependent attenuation relation to assess, quantify and optimize the performance of any arbitrary infrasound network to monitor explosive sources such as volcanic eruptions. Simulations are further enhanced by including realistic sources and propagation effects. We apply our approach to both hemispheres by considering the Euro-Mediterranean and the Eastern Australian regions. In these regions, we use quasi-permanent infrasound signals from Mt. Etna recorded in Tunisia and from Mt. Yasur recorded in New Caledonia. These well-instrumented volcanoes offer a unique opportunity to validate our attenuation model. In particular, accurate comparisons between near and far-field recordings demonstrate the potential of the proposed methodology to remotely monitor volcanoes. A good agreement is found between modeled and observed results, especially when incorporating representative 10 m/s wind perturbations in the atmospheric specifications according to previous campaign measurements. To optimize the network layout in order to ensure the best monitoring of the volcanoes, we proceed through a grid search to find optimum locations of an additional array. We show that adding one array at an appropriate location in both regions under study could significantly improve detections half of the year. The application of the proposed methodology can provide in near real-time a realistic confidence level of volcanic eruption detections, useful to mitigate the risk of aircrafts encountering volcanic ash.

  9. Assessing and optimizing the performance of infrasound networks to monitor volcanic eruptions

    NASA Astrophysics Data System (ADS)

    Tailpied, Dorianne; Le Pichon, Alexis; Marchetti, Emanuele; Assink, Jelle; Vergniolle, Sylvie

    2017-01-01

    We propose a numerical modeling technique based on a frequency-dependent attenuation relation to assess, quantify and optimize the performance of any arbitrary infrasound network to monitor explosive sources such as volcanic eruptions. Simulations are further enhanced by including realistic sources and propagation effects. We apply our approach to both hemispheres by considering the Euro-Mediterranean and the Eastern Australian regions. In these regions, we use quasi-permanent infrasound signals from Mt. Etna recorded in Tunisia and from Mt. Yasur recorded in New Caledonia. These well-instrumented volcanoes offer a unique opportunity to validate our attenuation model. In particular, accurate comparisons between near- and far-field recordings demonstrate the potential of the proposed methodology to remotely monitor volcanoes. A good agreement is found between modeled and observed results, especially when incorporating representative 10 m s-1 wind perturbations in the atmospheric specifications according to previous campaign measurements. To optimize the network layout in order to ensure the best monitoring of the volcanoes, we proceed through a grid search to find optimum locations of an additional array. We show that adding one array at an appropriate location in both regions under study could significantly improve detections half of the year. The application of the proposed methodology can provide in near real-time a realistic confidence level of volcanic eruption detections, useful to mitigate the risk of aircrafts encountering volcanic ash.

  10. Detecting hidden volcanic explosions from Mt. Cleveland Volcano, Alaska with infrasound and ground-couples airwaves

    USGS Publications Warehouse

    De Angelis, Slivio; Fee, David; Haney, Matthew; Schneider, David

    2012-01-01

    In Alaska, where many active volcanoes exist without ground-based instrumentation, the use of techniques suitable for distant monitoring is pivotal. In this study we report regional-scale seismic and infrasound observations of volcanic activity at Mt. Cleveland between December 2011 and August 2012. During this period, twenty explosions were detected by infrasound sensors as far away as 1827 km from the active vent, and ground-coupled acoustic waves were recorded at seismic stations across the Aleutian Arc. Several events resulting from the explosive disruption of small lava domes within the summit crater were confirmed by analysis of satellite remote sensing data. However, many explosions eluded initial, automated, analyses of satellite data due to poor weather conditions. Infrasound and seismic monitoring provided effective means for detecting these hidden events. We present results from the implementation of automatic infrasound and seismo-acoustic eruption detection algorithms, and review the challenges of real-time volcano monitoring operations in remote regions. We also model acoustic propagation in the Northern Pacific, showing how tropospheric ducting effects allow infrasound to travel long distances across the Aleutian Arc. The successful results of our investigation provide motivation for expanded efforts in infrasound monitoring across the Aleutians and contributes to our knowledge of the number and style of vulcanian eruptions at Mt. Cleveland.

  11. Analysis of infrasound waves generated by the May 2012 earthquake sequence in Northen Italy

    NASA Astrophysics Data System (ADS)

    Marchetti, E.; Ripepe, M.; Le Pichon, A.; Lacanna, G.; Piccinini, D.

    2013-12-01

    In May 2012 a 5.9 ML earthquake occurred in Northern Italy with the sequence of major quakes (Ml>5.4) clearly felt in Northern and Central Italy. Almost 2000 earthquakes, with local magnitude ranging between 1 and 5.9, were recorded in one month, and were typically associated with shallow (<10 km) inverse faults. We present analysis of pressure waves generated by these earthquakes and recorded at epicentral distances of ~200 km southward, at the large (1.4 km) aperture AMT array in Central Italy, and of ~300 km westward, at the small (130 m) aperture CHA array, operating in the northwestern Italian Alps mostly for snow avalanche monitoring. Infrasound is recorded for events with varying magnitude (Ml >4) and depth (5-15 km), and appears to be composed both of epicentral infrasound, produced at the source, and secondary infrasound, produced by the shaking of topography around the source. The robust infrasound dataset and the optimal recording condition, with downwind propagation to the CHA array, allow to carefully investigate the origin of the infrasonic radiation. Back-propagation of infrasonic detections points to a maximum infrasound radiation along an extended area in the PO valley. The relationship between infrasonic emission and earthquake source parameters such as magnitude, depth, focal mechanism and directivity, are analyzed for small-to-moderate magnitude earthquakes. Given the large distance among IMS infrasonic arrays, the relationship between infrasound and earthquakes is not well documented yet and mainly restricted to ML>7 earthquake, and thus still debated. Accordingly, the present study, that integrates within the FP7 ARISE design study project (Atmospheric dynamics Research InfraStructure in Europe), represents a good opportunity to investigate such a topic given the robust seismological constraints and optimal infrasound records.

  12. CTBT infrasound network performance to detect the 2013 Russian fireball event

    NASA Astrophysics Data System (ADS)

    Pilger, Christoph; Ceranna, Lars; Ross, J. Ole; Le Pichon, Alexis; Mialle, Pierrick; Garcés, Milton A.

    2015-04-01

    The explosive fragmentation of the 2013 Chelyabinsk meteorite generated a large airburst with an equivalent yield of 500 kT TNT. It is the most energetic event recorded by the infrasound component of the Comprehensive Nuclear-Test-Ban Treaty-International Monitoring System (CTBT-IMS), globally detected by 20 out of 42 operational stations. This study performs a station-by-station estimation of the IMS detection capability to explain infrasound detections and nondetections from short to long distances, using the Chelyabinsk meteorite as global reference event. Investigated parameters influencing the detection capability are the directivity of the line source signal, the ducting of acoustic energy, and the individual noise conditions at each station. Findings include a clear detection preference for stations perpendicular to the meteorite trajectory, even over large distances. Only a weak influence of stratospheric ducting is observed for this low-frequency case. Furthermore, a strong dependence on the diurnal variability of background noise levels at each station is observed, favoring nocturnal detections.

  13. The stratospheric arrival pair in infrasound propagation.

    PubMed

    Waxler, Roger; Evers, Läslo G; Assink, Jelle; Blom, Phillip

    2015-04-01

    The ideal case of a deep and well-formed stratospheric duct for long range infrasound propagation in the absence of tropospheric ducting is considered. A canonical form, that of a pair of arrivals, for ground returns of impulsive signals in a stratospheric duct is determined. The canonical form is derived from the geometrical acoustics approximation, and is validated and extended through full wave modeling. The full caustic structure of the field of ray paths is found and used to determine phase relations between the contributions to the wavetrain from different propagation paths. Finally, comparison with data collected from the 2005 fuel gas depot explosion in Buncefield, England is made. The correspondence between the theoretical results and the observations is shown to be quite good.

  14. Uncertainties associated with parameter estimation in atmospheric infrasound arrays

    NASA Astrophysics Data System (ADS)

    Szuberla, Curt A. L.; Olson, John V.

    2004-01-01

    This study describes a method for determining the statistical confidence in estimates of direction-of-arrival and trace velocity stemming from signals present in atmospheric infrasound data. It is assumed that the signal source is far enough removed from the infrasound sensor array that a plane-wave approximation holds, and that multipath and multiple source effects are not present. Propagation path and medium inhomogeneities are assumed not to be known at the time of signal detection, but the ensemble of time delays of signal arrivals between array sensor pairs is estimable and corrupted by uncorrelated Gaussian noise. The method results in a set of practical uncertainties that lend themselves to a geometric interpretation. Although quite general, this method is intended for use by analysts interpreting data from atmospheric acoustic arrays, or those interested in designing and deploying them. The method is applied to infrasound arrays typical of those deployed as a part of the International Monitoring System of the Comprehensive Nuclear-Test-Ban Treaty Organization.

  15. Characterization of Atmospheric Infrasound for Improved Weather Monitoring

    NASA Astrophysics Data System (ADS)

    Threatt, Arnesha; Elbing, Brian

    2016-11-01

    Collaboration Leading Operational UAS Development for Meteorology and Atmospheric Physics (CLOUD MAP) is a multi-university collaboration focused on development and implementation of unmanned aircraft systems (UAS) and integration with sensors for atmospheric measurements. A primary objective for this project is to create and demonstrate UAS capabilities needed to support UAS operating in extreme conditions, such as a tornado producing storm system. These storm systems emit infrasound (acoustic signals below human hearing, <20 Hz) up to 2 hours before tornadogenesis. Due to an acoustic ceiling and weak atmospheric absorption, infrasound can be detected from distances in excess of 300 miles. Thus infrasound could be used for long-range, passive monitoring and detection of tornadogenesis as well as directing UAS resources to high-decision-value-information. To achieve this the infrasonic signals with and without severe storms must be understood. This presentation will report findings from the first CLOUD MAP field demonstration, which acquired infrasonic signals while simultaneously sampling the atmosphere with UAS. Infrasonic spectra will be shown from a typical calm day, a continuous source (pulsed gas-combustion torch), singular events, and UAS flights as well as localization results from a controlled source and multiple microphones. This work was supported by NSF Grant 1539070: CLOUD MAP - Collaboration Leading Operational UAS Development for Meteorology and Atmospheric Physics.

  16. Infrasound workshop for CTBT monitoring: Proceedings

    SciTech Connect

    Christie, D.; Whitaker, R.

    1998-11-01

    It is expected that the establishment of new infrasound stations in the global IMS network by the Provisional Technical Secretariat of the CTBTO in Vienna will commence in the middle of 1998. Thus, decisions on the final operational design for IMS infrasound stations will have to be made within the next 12 months. Though many of the basic design problems have been resolved, it is clear that further work needs to be carried out during the coming year to ensure that IMS infrasound stations will operate with maximum capability in accord with the specifications determined during the May 1997 PrepCom Meeting. Some of the papers presented at the Workshop suggest that it may be difficult to design a four-element infrasound array station that will reliably detect and locate infrasound signals at all frequencies in the specified range from 0.02 to 4.0 Hz in all noise environments. Hence, if the basic design of an infrasound array is restricted to four array elements, the final optimized design may be suited only to the detection and location of signals in a more limited pass-band. Several participants have also noted that the reliable discrimination of infrasound signals could be quite difficult if the detection system leads to signal distortion. Thus, it has been emphasized that the detection system should not, if possible, compromise signal fidelity. This report contains the workshop agenda, a list of participants, and abstracts and viewgraphs from each presentation.

  17. Infrasonic source location imaging with the USArray: Application to one year of seismic data

    NASA Astrophysics Data System (ADS)

    Walker, K. T.; Shelby, R.; Hedlin, M. A.; Degroot-Hedlin, C. D.

    2010-12-01

    The USArray directly measures ground motion, which can mostly be attributed to ocean waves, earthquakes, volcanoes, and weather systems that load the Earth’s surface. Another source of ground motion is the transfer of atmospheric acoustic energy into seismic energy at the Earth’s surface. Infrasound (low frequency sound below ~20 Hz) can travel great distances unattenuated in atmospheric ducts. The infrasonic wave field is rich due to a variety of anthropogenic and geophysical phenomena including earthquakes, volcanoes, landslides, meteors, lightning and sprites, auroras, and oceanic and atmospheric processes. Globally spaced microbarometer arrays with apertures of 100 m to 2 km are typically used to study these sources. However, these arrays are separated by thousands of kilometers, which places considerable limits on what they can teach us about infrasound source physics. The USArray is in a position to study infrasound sources in unprecedented detail. Here we apply reverse-time migration to acoustic-to-seismic coupled signals recorded by the USArray to detect and locate in two-dimensional space and time several hundred infrasound sources in the western U.S. that occurred during 2008. Each event is visually inspected and assigned a quality rating. Confidence regions are determined using a bootstrap technique. The highest quality signals can be observed out to at least 1500 km range. We report the source location parameters for these events and investigate detection and location patterns. These results suggest that seismic networks near nuclear test monitoring infrasound arrays could be used to reduce the false alarm rate by identifying nearby, repeating sources of infrasound that create signals that are detected by the infrasound arrays. More fundamentally, these detected events comprise a ground truth database that can be used to validate or improve atmospheric velocity models.

  18. Seismo-Acoustic Observations of Explosive Sources

    NASA Astrophysics Data System (ADS)

    Chael, E. P.; Hart, D. M.; Jones, K. R.

    2011-12-01

    Since January 2011, the Sandia National Laboratories Facility for Acceptance, Calibration and Testing (FACT) has operated a seismo-acoustic station with the purpose of recording local explosions on Kirtland Air Force Base (KAFB). Our immediate goals are to develop a catalog of events and a database of seismo-acoustic waveforms from ordnance disposal and Defense Threat Reduction Agency (DTRA) events. The catalog of events will include metadata such as shot time, size, type and location. The waveform archive includes a three-channel GS-13 seismometer and a single infrasound sensor (Chaparral 25 with 50' porous hose wind reduction system). In June of 2011 a weather station was added to complement the monitoring system by providing accurate wind conditions at the times of the explosive events. Monthly internal reports compiled by KAFB provided us with the metadata for the ordnance disposal explosions, and an agreement with DTRA has enabled us to obtain metadata on their events. To date 157 explosions have been identified, including 153 ordnance disposal events and 4 DTRA tests. Along with the catalog of events we have developed automated processing routines to extract both seismic and infrasound arrivals and measure basic waveform characteristics. These include amplitudes of pre-event noise, the direct seismic arrival, air-coupled seismic arrival, infrasound arrival, and wind speed/direction. Using the waveform measurements from the pre-event noise and air-coupled seismic arrival we calculate the SNR for the seismic component of the event. We also calculate the SNR for the infrasonic component of the event using pre-event noise and the direct infrasound arrival. Using the metadata and seismic and infrasonic SNR values we are able to calculate an air-to-ground coupling ratio for each event. For local (<10 km) explosion monitoring, the wind speed and direction can influence all of the analysis parameters. It will affect the pre-event noise level as well as the infrasound

  19. The Effects of High Level Infrasound

    DTIC Science & Technology

    1980-02-01

    Ohreshold of such effects may be as low as 150 dl] for the chinchillas . .’The chinchilla is prob.ably more sensitive to infrasound than humans. There...several minutes (7 Hz). For these short times, no damage to the tympanic membrane or middle ear system occurred. However, the chinchilla results do...Johnson, D. L., "Exposure of Four Chinchillas to Infrasound," Research Memo dated Mar 1976, AMRL, WPAFB OH. 8. Tonndorf, J., "The Influence of Service on

  20. Finite-difference time-domain modeling of infrasound from pulsating auroras and comparison with recent experiments

    NASA Astrophysics Data System (ADS)

    de Larquier, S.; Pasko, V. P.; Stenbaek-Nielsen, H. C.; Wilson, C. R.; Olson, J. V.

    2009-12-01

    Atmospheric infrasonic waves are acoustic waves with frequencies ranging from 0.02 to 10 Hz, slightly higher than the acoustic cut-off frequency (approximately 0.032 Hz), but lower than the audible frequencies (typically 20 Hz-15 kHz) [e.g., Blanc, Ann. Geophys., 3, 673, 1985]. A number of natural events have been identified as generating atmospheric infrasound, such as volcanoes, tornadoes, avalanches, earthquakes [e.g., Bedard and Georges, Physics Today, S3, 32, 2000], ocean surfaces [e.g., Gossard and Hooke, Waves in the Atmosphere, Elsevier, 1975, Ch. 9], lightning [e.g., Assink et al., GRL, 35, L15802, 2008; Pasko, JGR, 114, D08205, 2009], or transient luminous events in the middle atmosphere termed sprites [e.g., Farges, Lightning: Principles, Instruments and Applications, H.D. Betz et al. (eds), Springer, 2009, Ch. 18]. The importance of infrasound studies has been emphasized in the past ten years from the Comprehensive Nuclear-Test-Ban Treaty verification perspective [e.g., Le Pichon et al., JGR, 114, D08112, 2009]. A proper understanding of infrasound propagation in the atmosphere is required for identification and classification of different infrasonic waves and their sources [Drob et al., JGR, 108, D21, 4680, 2003]. The goal of the present work is to provide a quantitative interpretation and explanation of infrasonic signatures from pulsating auroras reported recently by Wilson et al. [GRL, 32, L14810, 2005]. The infrasound signals observed with an infrasonic array at Fairbanks, Alaska had a mean amplitude of 0.05 Pa, a delay of about 5 minutes from the pulsating aurora, and an almost normal incidence on the ground plane [Wilson et al., 2005]. We employ a finite-difference time-domain (FDTD) model of infrasound propagation in a realistic atmosphere. We use the absorption model of infrasound introduced by Sutherland and Bass [J. Acoust. Soc. Am., 115, 1012, 2004]. Classical absorption mechanisms as well as molecular relaxation mechanisms are taken into

  1. Regional measurements of infrasound signals from ARIANE-5 engine tests in Southern Germany

    NASA Astrophysics Data System (ADS)

    Koch, K.

    2012-04-01

    A well-controlled source of repetitive infrasound emissions was previously identified and has been related to development and acceptance tests of the European Space Agencies ARIANE-5 main engine. The propulsion testing facility of the German Aerospace Agency (DLR) near Heilbronn, Southern Germany, is a distance of about 320 km away from the International Monitoring System (IMS) station IS26 in east-southeasterly direction. In the past, signals associated with these propulsion tests could normally be detected at IS26 during winter months, but not during summer months, reflecting the changes in atmospheric conditions between winter and summer. Over the last year, DLR has prepared to conduct a series of seven propulsion tests which started in November 2011; with interim times between tests of 3-4 weeks it will last until late March or early April 2012. With mobile infrasound recording equipment available at BGR we planned to record the infrasonic wavefield along the path to IS26 at regular distances starting as close as 20 km from the source. Our aim is to study sound propagation from direct paths mainly involving the tropospheric layer through the "zone of silence" to distances close to IS26, where paths through stratospheric layers are followed. Preliminary results show that during the relevant winter season direct path propagation can be observed to some 40 km from the propulsion test source, even at seismographic stations where the acoustic wave couples into the ground. The tests are also observed at IS26, and waveform duration and f-k-analysis confirm the signals to be associated with the GT-type propulsion tests.

  2. Large meteoroid detection using the global IMS infrasound system

    SciTech Connect

    ReVelle, D. O.

    2002-01-01

    Numerous signals will be routinely detected using the 60 array, global IMS (International Monitoring System) infrasound network. Infrasonic signals are sub-audible quasi longitudinal, atmospheric waves in the frequency band from about 10 Hz to -5 minutes in period (limited by human acoustic audibility in the high frequency limit and by the wave-guide acoustic cut-off frequency and the Brunt Vaisalla frequency in the low frequency limit) These small amplitude waves are a natural subset of the well-known atmospheric acoustic-gravity wave regime which has been identified from the linearized equations of geophysical fluid mechanics in the flat earth approximation, neglecting the earth's rotation, etc. For the IMS network the instrumental pressure sensor response was chosen to range from -4 to 0.02 Hz. These are ground-based arrays of typically 4 to 9 sensors with separations of about 1-2 km between the array elements. Examples of naturally occurring impulsive sources of infrasound include volcanic eruptions, earthquakes, bolides (large meteor-fireballs entering the atmospheric at very high speeds up to -300 times faster than ground-level sound waves), microbaroms (the 'voice of the sea' due to the interaction of atmospheric storms and surface ocean waves) and the supersonic motion of the auroral electrojet at about 100 km altitude (auroral infrasonic waves), etc. In this paper we will briefly summarize our current state of knowledge of infrasound signals from bolides. This summary will include the generation of the signals at the complex, quasi-cylindrical line source, to the refraction and diffraction of the propagating waves by the middle atmospheric and tropospheric temperature and wind systems and finally, the detection of the signals and their interpretation by inferring the source properties, Le., source altitude, blast radius (see below) and the source energy, etc. In addition, we will use infrasound from energetic bolides to estimate the expected steady state

  3. Upper atmospheric processes as measured by collocated Lidar, infrasound, radiometer and airglow measurements

    NASA Astrophysics Data System (ADS)

    Le Pichon, A.; Blanc, E.; Assink, J. D.; Ceranna, L.; Pilger, C.; Ross, O.; Keckhut, P.; Hauchecorne, A.; Schmidt, C.; Bittner, M.; Wuest, S.; Rüfenacht, R.; Kaempfer, N.; Smets, P.

    2013-12-01

    To better initialize weather forecasting systems, a key challenge is to understand stratosphere-resolving climate models. The ARISE project (http://arise-project.eu/) aims to design a novel infrastructure integrating different atmospheric observation networks to accurately recover the vertical structure of the wind and temperature from the ground to the mesosphere. This network includes Lidar and mesospheric airglow observations, complemented by continuous infrasound measurements. Together with additional ground-based wind radar system, such complementary techniques help to better describe the interaction between atmospheric layers from the ground to the mesosphere and the influence of large scale waves on the atmospheric dynamics. Systematic comparisons between these observations and the ECMWF upper wind and temperature models (http://www.ecmwf.int/) have been performed at the OHP site (Haute-Provence Observatory, France). The main results are outlined below. - Systematic comparisons between Lidar soundings (NDACC, http://ndacc-lidar.org/) and ECMWF highlight differences increasing with altitude. Below 50 km altitude, differences are as large as 20°K. In average, the temperature appears to be overestimated by ~5 m/s in the stratosphere and underestimated by ~10 m/s in the mesopause. - Comparisons with collocated infrasound measurements provide additional useful integrated information about the structure of the stratospheric waveguide. Below 0.5 Hz, most infrasound signals originate from ocean swells in the North Atlantic region. As expected, since most long-range propagating signals travel in the stratospheric waveguide, improved detection capability occurs downwind. Deviations from this trend are either related to short time-scale variability of the atmosphere (e.g., large-scale planetary waves, stratospheric warming effects), or can be explained by changes in the nature of the source. We investigate possible correlation between unexpected propagation paths and

  4. Infrasound induced instability by modulation of condensation process in the atmosphere.

    PubMed

    Naugolnykh, Konstantin; Rybak, Samuil

    2008-12-01

    A sound wave in supersaturated water vapor can modulate both the process of heat release caused by condensation, and subsequently, as a result, the resonance interaction of sound with the modulated heat release provides sound amplification. High-intensity atmospheric perturbations such as cyclones and thunderstorms generate infrasound, which is detectable at large distances from the source. The wave-condensation instability can lead to variation in the level of infrasound radiation by a developing cyclone, and this can be as a precursor of these intense atmospheric events.

  5. Characterization of absorption and non-linear effects in infrasound propagation using an augmented Burgers' equation

    NASA Astrophysics Data System (ADS)

    Sabatini, R.; Bailly, C.; Marsden, O.; Gainville, O.

    2016-12-01

    The long-range atmospheric propagation of explosion-like waves of frequency in the infrasound range is investigated using non-linear ray theory. Simulations are performed for sources of increasing amplitude on rays up to the lower thermosphere and for distances of hundreds of kilometres. A study of the attenuation of the waveforms observed at ground level induced by both the classical mechanisms and the vibrational relaxation of the molecules comprising the atmospheric gas is carried out. The relative importance of classical absorption and vibrational relaxation along the typical atmospheric propagation trajectories is assessed. Non-linear effects are highlighted as well and particular emphasis is placed on their strong interaction with absorption phenomena. A detailed description of the propagation model and of the numerical algorithm used in this work is first reported. Results are then discussed and the importance of the different mechanisms is clarified.

  6. Reduction of infrasounds in machines with hydrostatic drive.

    PubMed

    Kudźma, Zygmunt; Stosiak, Michał

    2013-01-01

    Some hazards posed by the operation of hydraulic systems, connected with low-frequency vibrations and noise are presented. Special attention is focused on infrasounds. The sources of low-frequency vibrations and noise and ways of reducing them are indicated. An original solution ensuring the effective reduction of vibrations and noise in a wide frequency range, i.e., a wide-band damper of pressure fluctuations, also performing the function of an acoustic filter, is proposed. The effectiveness of the damper was confirmed by the results of laboratory tests and tests carried out on engineering machines working in real conditions.

  7. Responses of the ear to low frequency sounds, infrasound and wind turbines.

    PubMed

    Salt, Alec N; Hullar, Timothy E

    2010-09-01

    Infrasonic sounds are generated internally in the body (by respiration, heartbeat, coughing, etc) and by external sources, such as air conditioning systems, inside vehicles, some industrial processes and, now becoming increasingly prevalent, wind turbines. It is widely assumed that infrasound presented at an amplitude below what is audible has no influence on the ear. In this review, we consider possible ways that low frequency sounds, at levels that may or may not be heard, could influence the function of the ear. The inner ear has elaborate mechanisms to attenuate low frequency sound components before they are transmitted to the brain. The auditory portion of the ear, the cochlea, has two types of sensory cells, inner hair cells (IHC) and outer hair cells (OHC), of which the IHC are coupled to the afferent fibers that transmit "hearing" to the brain. The sensory stereocilia ("hairs") on the IHC are "fluid coupled" to mechanical stimuli, so their responses depend on stimulus velocity and their sensitivity decreases as sound frequency is lowered. In contrast, the OHC are directly coupled to mechanical stimuli, so their input remains greater than for IHC at low frequencies. At very low frequencies the OHC are stimulated by sounds at levels below those that are heard. Although the hair cells in other sensory structures such as the saccule may be tuned to infrasonic frequencies, auditory stimulus coupling to these structures is inefficient so that they are unlikely to be influenced by airborne infrasound. Structures that are involved in endolymph volume regulation are also known to be influenced by infrasound, but their sensitivity is also thought to be low. There are, however, abnormal states in which the ear becomes hypersensitive to infrasound. In most cases, the inner ear's responses to infrasound can be considered normal, but they could be associated with unfamiliar sensations or subtle changes in physiology. This raises the possibility that exposure to the

  8. Numerical modeling of infrasound propagation at very long distance

    NASA Astrophysics Data System (ADS)

    Piserchia, Pierre-Franck; Roche, Roger

    2004-05-01

    Compliance with the CTBT in the atmosphere will be monitored by a world-wide network of infrasound stations consisting of 60 stations equipped with microbarographs in order to measure small changes in the air pressure in the frequency range 0.02 to 4 Hz. They are characterized by a good sensitivity, and by a large dynamic. By the application of array techniques, it is possible to determine the direction of pressure pulses caused by small explosions in the atmosphere, as well as shock waves caused by supersonic aircraft or meteorites. To take into account the nonlinear phenomena at the source and during the propagation, we are developing a numerical approach to solve the Euler nonlinear equation. In a first step, in the linear domain, this method is compared with two other numerical modeling approaches based on the ray tracing technique and the parabolic approach. In our test case, the source is on the ground and generates a 1-Pa pressure pulse centered at the frequency of 0.1 Hz. We considered an infrasound propagation over a distance of 500 km and an atmosphere height of 200 km. In a further step, the source level will be increased to study nonlinear phenomena.

  9. Infrasound from the September 24 2002 Vitim (Siberian) fireball

    NASA Astrophysics Data System (ADS)

    Shumilov, O. I.; Kasatkina, E. A.; Tereshchenko, E. D.; Kulichkov, S. N.; Raspopov, O. M.; Vasiljev, A. N.; Struev, A. G.

    2003-04-01

    On 24 September 2002, sensors aboard US Department Of Defence satellites detected the impact of a fireball at 16.49 UT near Bodaibo in Siberia (58.21 N, 113.46 E). Eyewitnesses described the fireball as a large bright star streaking across the sky, ending in bright flash and loud explosive noise. Ground shaking detonations were felt at a large distance (tens of kilometers). An array of microbarographs operated at Polar Geophysical Institute (PGI), Apatity (67.3 N, 33.3 E) recorded a pressure impulse with an amplitude of 45 dyn/cm^2 on September 24, 2002 at 22.20 UT, at a distance about of 4000 km from a fireball detection. The PGI microbarograph array consists of three spatially placed infrasound detectors for measurements of atmospheric waves in the frequency band of 0.0001 - 1 Hz. The computer-aided system permits to get information with a frequency of five times per second. The time interval between the bolide observation and the detection of pressure impulse is consistent with an acoustic travel time from the location of fireball impact. Estimates were made of both the local infrasound velocity and the direction of arrival of the signal. These values are in agreement with the travel velocity and the south azimuth. Estimates of the fireball mass from the radiated energy value agree with mass estimates calculated from the blast wave theory. These results seem to suppose the propagation of the infrasound signal from the Vitim fireball through atmospheric acoustic wave guide. According to Brown et al. (Nature, V420, 294, 2002) estimations the Earth is hit on average annually by the Vitim-like meteorite. Collisions of large asteroids with our planet result in dramatic impacts that can lead to the Earth magnetic field reversals. This work was supported by EC (grant INTAS 97-31008) and RFBR (grant 01-05-64850).

  10. Evolution of the CTBTO Infrasound Technology Roadmap

    NASA Astrophysics Data System (ADS)

    Garces, Milton; Haralabus, Georgios; Noack, Patrick; Grenard, Patrick

    2013-04-01

    The CTBTO's nuclear explosion monitoring program needs to maintain its effectiveness and ensure its long-term relevance to the verification regime. The aims of its Infrasound Technology Roadmap (ITR) are to (1) establish a clear way forwards in accordance with the overall CTBTO nuclear monitoring vision, (2) couple scientific work with technology management, and (3) build upon existing technological accomplishments and project them into near-future technical targets. This ITR has a time horizon of seven years, and its activities are closely aligned to the Provisional Technical Secretariat's Technology Foresight Program, which extends its perspective to 20+ years. Phase 1 of the Roadmap effort requested input from the international infrasound community through the Request for Contributions released on 15 November 2012 (RFC R1). A set of metrics were selected to lend fairness, accountability, and scientific integrity to the evaluation of technical topics. The RFC was an inclusive, participatory effort inviting individual scientists to identify and assess technologies and procedures that can be infused into the IMS to meet its monitoring requirements and help evolve technology to achieve a reliable, sustainable and trustworthy monitoring system. We received over 680 individual topic evaluations from 52 members of the international infrasound community, with a 93% response rate. We present the statistical results from our survey as well as the highlights of the draft Infrasound Technology Roadmap Document.

  11. Infrasound Signal Characteristics from Small Earthquakes

    DTIC Science & Technology

    2010-09-01

    by many groups, e.g., McKenna et al. (2007), Che et al. (2002), and Sorrells et al. (1997). These studies show that infrasound detections can be...L. Zoback, and D. D. Blackwell, Eds. Boulder, CO: Geol. Soc. Am. Sorrells , G. G., E. Herrin, and J. L. Bonner (1997). Construction of regional

  12. Infrasound Signal Characteristics from Small Earthquakes

    DTIC Science & Technology

    2011-09-01

    infrasound from surface explosions ( Sorrells et al., 1997; Che et al., 2002; and McKenna et al., 2007) with the work identifying the importance of path...M. L., Blackwell, and D. D., Eds., Geological Society of America, Boulder, CO, pp. 185–228. Sorrells , G. G., E. Herrin, and J. L. Bonner (1997

  13. Unraveling Structural Infrasound: understanding the science for persistent remote monitoring of critical infrastructure (Invited)

    NASA Astrophysics Data System (ADS)

    McKenna, S. M.; Diaz-Alvarez, H.; McComas, S.; Costley, D.; Whitlow, R. D.; Jordan, A. M.; Taylor, O.

    2013-12-01

    In 2006, the Engineer Research and Development Center (ERDC) began a program designed to meet the capability gap associated with remote assessment of critical infrastructure. This program addresses issues arising from the use of geophysical techniques to solve engineering problems through persistent monitoring of critical infrastructure using infrasound. In the original 2006-2009 study of a railroad bridge in Ft. Leonard Wood, MO, the fundamental modes of motion of the structure were detected at up to 30 km away, with atmospheric excitation deemed to be the source driver. Follow-on research focused on the mechanically driven modes excited by traffic, with directional acoustic emanations. The success of the Ft. Wood ambient excitation study resulted in several subsequent programs to push the boundaries of this new technique for standoff assessment, discussed herein. Detection of scour and river system health monitoring are serious problems for monitoring civil infrastructure, from both civilian and military perspectives. Knowledge of overall system behavior over time is crucial for assessment of bridge foundations and barge navigation. This research focuses on the same steel-truss bridge from the Ft. Wood study, and analyzes 3D and 2D substructure models coupled with the superstructure reaction loads to assess the modal deformations within the infrasound bandwidth and the correlation to scour of embedment material. The Urban infrasound program is infrasound modeling, data analysis, and sensor research leading to the detection, classification and localization of threat activities in complex propagation environments. Three seismo-acoustic arrays were deployed on rooftops across the Southern Methodist University campus in Dallas, Texas, to characterize the urban infrasound environment. Structural sources within 15 km of the arrays have been identified through signal processing and confirmed through acoustical models. Infrasound is also being studied as a means of

  14. Infrasound Signals from Ground-Motion Sources

    DTIC Science & Technology

    2008-09-01

    reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions...information if it does not display a currently valid OMB control number. 1 . REPORT DATE SEP 2008 2. REPORT TYPE 3. DATES COVERED 00-00-2008 to 00-00...zone calculation (Figure 1 ), where the input velocity data were from the modeled accelerations for the Tortugas event in hole U3gg. In the CAVEAT

  15. Infrasound as a Detector of Local and Remote Turbulence

    NASA Astrophysics Data System (ADS)

    Cuxart, J.; Tatrai, D.; Weidinger, T.; Kircsi, A.; Józsa, J.; Kiss, M.

    2016-05-01

    Infrasound measurements are used to detect seismic waves and a large effort is devoted to eliminating the turbulence-related infrasound signal, usually considered as noise. Here we take a complementary approach, investigating whether infrasound can provide information on atmospheric turbulence. Microphone measurements of infrasound from an experimental campaign in Hungary in 2013 are used, together with data from a nearby sonic anemometer and a sodar. The comparison of infrasound integrated spectral energy to turbulent kinetic energy from the sonic provides a good match when turbulence is present near the ground. Moreover, on stable nights when the surface layer is strongly stratified and with turbulence absent, microphones sometimes recorded infrasound when the sodar showed a low-level jet above the surface inversion, indicating that microphones may be used as detectors of elevated turbulence.

  16. Evaluation of infrasound signals from the shuttle Atlantis using a large seismic network.

    PubMed

    de Groot-Hedlin, Catherine D; Hedlin, Michael A H; Walker, Kristoffer T; Drob, Douglas P; Zumberge, Mark A

    2008-09-01

    Inclement weather in Florida forced the space shuttle "Atlantis" to land at Edwards Air Force Base in southern California on June 22, 2007, passing near three infrasound stations and several hundred seismic stations in northern Mexico, southern California, and Nevada. The high signal-to-noise ratio, broad receiver coverage, and Atlantis' positional information allow for the testing of infrasound propagation modeling capabilities through the atmosphere to regional distances. Shadow zones and arrival times are predicted by tracing rays that are launched at right angles to the conical shock front surrounding the shuttle through a standard climatological model as well as a global ground to space model. The predictions and observations compare favorably over much of the study area for both atmospheric specifications. To the east of the shuttle trajectory, there were no detections beyond the primary acoustic carpet. Infrasound energy was detected hundreds of kilometers to the west and northwest (NW) of the shuttle trajectory, consistent with the predictions of ducting due to the westward summer-time stratospheric jet. Both atmospheric models predict alternating regions of high and low ensonifications to the NW. However, infrasound energy was detected tens of kilometers beyond the predicted zones of ensonification, possibly due to uncertainties in stratospheric wind speeds.

  17. Infrared Astronomy. [observations of extragalactic sources

    NASA Technical Reports Server (NTRS)

    Neugebauer, G.; Soifer, B. T.; Matthews, K.

    1981-01-01

    Several observational programs in infrared astronomy are described and significant findings are briefly discussed. The near infrared work concentrates largely on the use of the 5 m Hale telescope in spectroscopic and photometric studies of extragalactic sources. Observations of the P alpha line profile in a low redshift quasar, X-ray bursters, reflection nebula, and cataclysmic variables are included. Millimeter continuum observations of dust emission from quasars and galactic molecular clouds are also discussed. Finally, improvements to instrumentation are reported.

  18. Infrasound from the El Paso super-bolide of October 9, 1997

    SciTech Connect

    ReVelle, D.O.; Whitaker, R.W.; Armstrong, W.T.

    1998-12-31

    During the noon hour on October 9, 1997 an extremely bright fireball ({approx}-21.5 in stellar magnitude putting it into the class of a super-bolide) was observed over western Texas with visual sightings from as far away as Arizona to northern Mexico and even in northern New Mexico over 300 miles away. This event produced tremendously loud sonic boom reports in the El Paso area. It was also detected locally by 4 seismometers which are part of a network of 5 seismic stations operated by the University of Texas at El Paso (UTEP). Subsequent investigations of the data from the six infrasound arrays used by LANL (Los Alamos National Laboratory) and operated for the DOE (Department of Energy) as a part of the CTB (Comprehensive Test Ban) Research and Development program for the IMS (International Monitoring System) showed the presence of an infrasonic signal from the proper direction at the correct time for this super-bolide from two of the six arrays. Both the seismic and infrasound recordings indicated that an explosion occurred in the atmosphere at source heights from 28--30 km, having its epicenter slightly to the northeast of Horizon City, Texas. The signal characteristics, analyzed from {approx}0.1 to 5.0 Hz, include a total duration of {approx}4 min (at Los Alamos, LA) to >{approx}5 min at Lajitas, Texas, TXAR, another CTB IMS array operated by E. Herrin at Southern Methodist University (SMU) for a source directed from LA toward {approx}171--180 deg and from TXAR of {approx}321-4 deg respectively from true north. The observed signal trace velocities (for the part of the recording with the highest cross-correlation) at LA ranged from 300--360 m/sec with a signal velocity of 0.30 {+-} 0.03 km/sec, implying a Stratospheric (S Type) ducted path. The dominant signal frequency at LA was from 0.20 to 0.80 Hz, with a peak near 0.3 Hz. These highly correlated signals at LA had a very large, peak to peak, maximum amplitude of 21.0 microbars (2.1 Pa). The analysis, using

  19. Long period seismicity and very long period infrasound driven by shallow magmatic degassing at Mount Pagan, Mariana Islands

    USGS Publications Warehouse

    Lyons, John; Haney, Matt; Werner, Cynthia A.; Kelly, Peter; Patrick, Matthew R.; Kern, Christoph; Trusdell, Frank A.

    2016-01-01

    Long period (LP) seismicity and very long period infrasound (iVLP) were recorded during continuous degassing from Mount Pagan, Mariana Islands, in July 2013 to January 2014. The frequency content of the LP and iVLP events and delay times between the two arrivals were remarkably stable and indicate nearly co-located sources. Using phase-weighted stacking over similar events to dampen noise, we find that the LP source centroid is located 60 m below and 180 m west of the summit vent. The moment tensor reveals a volumetric source modeled as resonance of a subhorizontal sill intersecting a dike. We model the seismoacoustic wavefields with a coupled earth-air 3-D finite difference code. The ratios of pressure to velocity measured at the infrasound arrays are an order of magnitude larger than the synthetic ratios, so the iVLP is not the result of LP energy transmitting into the atmosphere at its epicenter. Based on crater shape and dimensions determined by structure from motion, we model the iVLP as acoustic resonance of an exponential horn. The source of the continuous plume from gas analysis is shallow magmatic degassing, which repeatedly pressurized the dike-sill portion of the conduit over the 7 months of observation. Periodic gas release caused the geologically controlled sill to partially collapse and resonate, while venting of gas at the surface triggered resonance in the crater. LP degassing only accounts for ~12% of total degassing, indicating that most degassing is relatively aseismic and that multiple active pathways exist beneath the vent.

  20. Seismic generated infrasounds on Telluric Planets: Modeling and comparisons between Earth, Venus and Mars

    NASA Astrophysics Data System (ADS)

    Lognonne, P. H.; Rolland, L.; Karakostas, F. G.; Garcia, R.; Mimoun, D.; Banerdt, W. B.; Smrekar, S. E.

    2015-12-01

    Earth, Venus and Mars are all planets in which infrasounds can propagate and interact with the solid surface. This leads to infrasound generation for internal sources (e.g. quakes) and to seismic waves generations for atmospheric sources (e.g. meteor, impactor explosions, boundary layer turbulences). Both the atmospheric profile, surface density, atmospheric wind and viscous/attenuation processes are however greatly different, including major differences between Mars/Venus and Earth due to the CO2 molecular relaxation. We present modeling results and compare the seismic/acoustic coupling strength for Earth, Mars and Venus. This modeling is made through normal modes modelling for models integrating the interior, atmosphere, both with realistic attenuation (intrinsic Q for solid part, viscosity and molecular relaxation for the atmosphere). We complete these modeling, made for spherical structure, by integration of wind, assuming the later to be homogeneous at the scale of the infrasound wavelength. This allows us to compute either the Seismic normal modes (e.g. Rayleigh surface waves), or the acoustic or the atmospheric gravity modes. Comparisons are done, for either a seismic source or an atmospheric source, on the amplitude of expected signals as a function of distance and frequency. Effects of local time are integrated in the modeling. We illustrate the Rayleigh waves modelling by Earth data (for large quakes and volcanoes eruptions). For Venus, very large coupling can occur at resonance frequencies between the solid part and atmospheric part of the planet through infrasounds/Rayleigh waves coupling. If the atmosphere reduced the Q (quality coefficient) of Rayleigh waves in general, the atmosphere at these resonance soffers better propagation than Venus crust and increases their Q. For Mars, Rayleigh waves excitations by atmospheric burst is shown and discussed for the typical yield of impacts. The new data of the Nasa INSIGHT mission which carry both seismic and

  1. Infrasound and Seismic Recordings of a US Airstrike on an ISIS Car Bomb Factory on June 3, 2015

    NASA Astrophysics Data System (ADS)

    Aleqabi, G. I.; Ghalib, H. A. A.; Wysession, M. E.

    2015-12-01

    Concurrent infrasound and seismic records of a jet airstrike in Iraq are presented. Media reports stated that US jets carried out a large airstrike on June 3, 2015, just after midnight local time, that targeted and destroyed an ISIS car bomb factory in Hawija, Iraq, just south of the city of Kirkuk, Iraq. The resulting explosion was felt within Kirkuk and at other locations as far as 34 km away from the Hawija factory. Seismic broadband stations located in northern Iraq, at a distance of about 160 km, show clear simultaneous signals of infrasound waves on the seismometers as well as on collocated infrasound equipment. From an analysis of the body waves, the Pg to Lg time difference is nearly ~20 sec, with a back azimuth of 250o to 260o, which is consistent with explosion location. The time difference between the Pg and infrasound signals is just over 7 minutes, consistent with sound speed in the atmosphere. No clear Rg wave was observed. As was demonstrated by Aleqabi, Wysession, and Ghalib [2015, BSSA, in press], broadband seismic recordings are able to identify and distinguish between several different kinds of MOUT (military operations in urban terrain) and even determine the magnitudes of ordinance used in certain blasts. The addition of collocated infrasound equipment provides additional constraints that can be used in the analysis of the size and form of the MOUT.

  2. Spectrophotometric observations of Molonglo radio source identifications

    NASA Technical Reports Server (NTRS)

    Smith, H. E.; Burbidge, E. M.; Baldwin, J. A.; Tohline, J. E.; Wampler, E. J.; Hazard, C.; Murdoch, H. S.

    1977-01-01

    The paper presents spectrophotometric observations of 76 optical objects identified with radio sources from the MC2 and MC3 catalogs. Line intensities, equivalent widths, line widths, and optical spectral indices are presented for 44 objects confirmed as quasi-stellar objects. The statistical and physical properties of the Molonglo sample are briefly discussed.

  3. Acoustic buffeting by infrasound in a low vibration facility.

    PubMed

    MacLeod, B P; Hoffman, J E; Burke, S A; Bonn, D A

    2016-09-01

    Measurement instruments and fabrication tools with spatial resolution on the atomic scale require facilities that mitigate the impact of vibration sources in the environment. One approach to protection from vibration in a building's foundation is to place the instrument on a massive inertia block, supported on pneumatic isolators. This opens the questions of whether or not a massive floating block is susceptible to acoustic forces, and how to mitigate the effects of any such acoustic buffeting. Here this is investigated with quantitative measurements of vibrations and sound pressure, together with finite element modeling. It is shown that a particular concern, even in a facility with multiple acoustic enclosures, is the excitation of the lowest fundamental acoustic modes of the room by infrasound in the low tens of Hz range, and the efficient coupling of the fundamental room modes to a large inertia block centered in the room.

  4. Acoustic buffeting by infrasound in a low vibration facility

    NASA Astrophysics Data System (ADS)

    MacLeod, B. P.; Hoffman, J. E.; Burke, S. A.; Bonn, D. A.

    2016-09-01

    Measurement instruments and fabrication tools with spatial resolution on the atomic scale require facilities that mitigate the impact of vibration sources in the environment. One approach to protection from vibration in a building's foundation is to place the instrument on a massive inertia block, supported on pneumatic isolators. This opens the questions of whether or not a massive floating block is susceptible to acoustic forces, and how to mitigate the effects of any such acoustic buffeting. Here this is investigated with quantitative measurements of vibrations and sound pressure, together with finite element modeling. It is shown that a particular concern, even in a facility with multiple acoustic enclosures, is the excitation of the lowest fundamental acoustic modes of the room by infrasound in the low tens of Hz range, and the efficient coupling of the fundamental room modes to a large inertia block centered in the room.

  5. Infrasound records from U.S. atmospheric tests

    SciTech Connect

    Chael, E.P.; Lohr, R.D.

    1998-07-01

    The United States conducted over 100 atmospheric nuclear tests at the Nevada Test Site from 1951 through 1962. Some of the earliest tests caused unexpected damage, primarily broken glass and cracked plaster, in Las Vegas and other surrounding communities. To address this problem, Sandia initiated a program to monitor and predict the pressure waves around NTS. Infrasound recording systems were developed, then field for all tests beginning with Operation Buster in October 1951. Investigators soon discovered that near-surface temperature inversions and wind profiles caused the damaging pressures in Las Vegas. A typical test was recorded at about a dozen stations from the Control Point on NTS to as far away as Pasadena, CA. In addition, some tests in the South Pacific were monitored, as well as numerous chemical explosions. Strip charts recorded signals in the frequency band from 0.05 to 30 Hz, and the paper tapes were achieved at Sandia in the early 1970s. The NTS events ranged in yield from below 1 ton to 74 kilotons; source altitudes varied from near ground level (including some cratering experiments) to as high as 11 km. The resulting data contain a wealth of information on the source function, yield scaling and regional propagation of infrasound signals from atmospheric explosions. The renewed interest in infrasonic monitoring for CTBT verification has prompted the authors to exhume some of the archived records. The authors plan to digitize the signals from several tests and evaluate their applicability to CTBT issues. In addition, they will collect any existing parametric measurements for these records (arrival times, amplitudes, etc.). All data will be converted to CSS database format and made available to the research community. If appropriate, the resulting information could also be included in the Knowledge Base under development for CTBT monitoring.

  6. Infrasound production by bolides: A global statistical study

    NASA Astrophysics Data System (ADS)

    Ens, T. A.; Brown, P. G.; Edwards, W. N.; Silber, E. A.

    2012-05-01

    We have examined a dataset consisting of 71 bolides detected by satellite sensors, which provide energy and location estimates, with simultaneous measurements of the same events on 143 distinct waveforms. These bolides have total source energies ranging from 0.02 kt TNT equivalent yield to ≈20 kt and probable diameters of order a few meters on average. We find that it is possible to detect large events with energies of ≈20 kt or more globally. Infrasonic detections of these events for stratospheric arrivals have ranges between 350-17,000 km and show clear wind-related amplitude modifications. We find that our period-yield relations are virtually identical to that found from AFTAC nuclear test data with the most robust period-yield correlation found for those events having multiple station averaged periods. We have also found empirical expressions relating maximum expected detection range for infrasound as a function of energy and low and high frequency cut-off as a function of energy. Our multi-variate fits suggest that 1/2 > yield-scaling is most appropriate for long range bolide infrasound measurements with a distance scaling exponent of ≈1.1 best representing the data. Our best-fit wind correction exponent is a factor of ≈3 smaller than found by previous studies which we suggest may indicate a decrease in the value of k with range. We find that the integral acoustic efficiency for bolides is ≥0.01% with a best lower limit estimate nearer 0.1%. Finally, we conclude that a range independent atmosphere implementation of the normal-mode approach to simulate bolide amplitudes is ineffective at large ranges due to the large change in atmospheric conditions along source-receiver paths.

  7. Effects of topography and atmospheric structure on volcano infrasound

    NASA Astrophysics Data System (ADS)

    Marcillo, O. E.; Johnson, J. B.

    2009-12-01

    Proper interpretation of infrasonic waves produced by volcanic explosions requires understanding of weather and topographic effects. We have studied infrasound produced by two different volcanoes (Kilauea and Tungurahua) to determine the influence of topographic and atmospheric conditions on the infrasonic records corresponding to several weeks of eruptive activity. This analysis is necessary to understand and correct for phase and amplitude responses in order to properly perform waveform modeling. For instance, these corrections are necessary to obtain a better estimate of volume flux from the volcanic vent. The first case study is a dataset acquired during June of 2008 at Kilauea volcano in Hawaii, focused on the active Halemaumau Vent. Several days of infrasonic tremor were recorded by a 3-station infrasound network. These records show a strong influence of wind and topography in one of the three stations of the network. This station was located 2370 m from the vent, at a comparable distance to the other stations, but line of sight to the vent was obstructed by a 50-meter high crater edge, which introduced diffraction effects. Periods when wind blew in the vent-station direction are correlated with increase in infrasonic energy in the 0.5 - 1 Hz bandwidth. The second case focuses on a campaign conducted in June 2009 at Tungurahua Volcano, Ecuador. This study implemented two infrasonic arrays located on the flanks of the volcano 6000m north of the vent and on the flanks of an adjacent hill, 11,500m northeast. Compared to the proximal array a distinctive attenuation is evident at certain frequencies (0.5-1.5 Hz) at the distal array. This degree of attenuation is time-variant and is mostly likely related to changing atmospheric structure. An alternative explanation for the apparent spectral differences between near and far stations (and their evolution over time) is a complex (and changing) source geometry due to non-compact sources.

  8. Design of monitoring and early warning system for geo-hazards in Three Gorges reservoir area using infrasound

    NASA Astrophysics Data System (ADS)

    Qiu, N.; Zeng, Z. X.; Yang, Y. C.

    2009-04-01

    With the progress of the Three Gorges Dam Project, geological disasters have become increasingly prominent. The reservoir area prone to landslides, collapses, cracks, and earthquake disaster because the complex terrain and geological conditions. It is of significance to monitor and foresee geo-hazards in the reservoir area. Here we introduce our design of monitoring and early warning system for geo-hazards in Three Gorges reservoir area using infrasound. Infrasound may be abnormal during geological disasters, such as debris and earthquake occurred. The formation a d movement of debris flow in its basin will generate infrasound, and spread to the surrounding air medium. Velocity of infrasound is much larger than that of debris flow, so we can monitor and forecast debris flow using infrasound. The sudden vertical displacement brought about by earthquake will generate acoustic-gravity wave which can be observed in distance to monitor earthquake, especially to monitor earthquake precursors. So we try to monitor the geological disasters for the Three Gorges reservoir area in China by design a infrasound array monitor system. This work is supported by Chinese "985 Project". The infrasound monitor system is comprised of two observation stations arranged in Badong county inside the reservoir area and in Wuhan city, respectively. Each station has respectively arranged a kind of augmentable linear array in the form of quasi-uniform linear array and additional amending direction sensors. The linear array comprises eight sensors arranged in several different uniform intervals along a line. The amending direction sensor is situated at certain point in mid-perpendicular of linear array in order to reduce multiplicity in determine the direction of arrival. The sensors used in the system are CDC-2B capacitances infrasonic receiver which can observe frequency ranging 0~20Hz. The, measurement resolution is 750mV/LPa. Infrasonic wave signal collected by sensor is transferred from

  9. Infrasonic observations of the Northridge, California, earthquake

    SciTech Connect

    Mutschlecner, J.P.; Whitaker, R.W.

    1994-09-01

    Infrasonic waves from the Northridge, California, earthquake of 17 January 1994 were observed at the St. George, Utah, infrasound array of the Los Alamos National Laboratory. The distance to the epicenter was 543 kilometers. The signal shows a complex character with many peaks and a long duration. An interpretation is given in terms of several modes of signal propagation and generation including a seismic-acoustic secondary source mechanism. A number of signals from aftershocks are also observed.

  10. Detection of volcanic infrasound with a ring laser interferometer

    NASA Astrophysics Data System (ADS)

    Dunn, Robert W.; Hosman, Ashley R.

    2014-11-01

    Over the last 15 years, large horizontally mounted ring lasers have been used to study numerous geophysical phenomena. This paper provides examples of the sensitivity of large active ring laser interferometers to far field infrasound emissions from explosive volcanic eruptions. Volcanic infrasound is reported from representative eruptions of volcanoes Kelut (Kelud), Klyuchevskaya (Kliuchevskoi), Puyehua, Santa Maria, Sakurajima, and Tungurahua. The detected infrasound frequencies are in basic agreement with the far field air wave frequencies from the 1980 eruption of Mount St. Helens and the 1991 eruption of Mount Pinatubo. Cavities of large horizontally mounted active ring lasers contain two counter-propagating waves that in the presence Earth's rotation become traveling waves of slightly different frequencies. The Sagnac or beat frequency due to the difference in the traveling wave frequencies is modulated by geophysical phenomena, in this case volcanic infrasound. Signatures of the infrasound are found in the frequency modulated side bands.

  11. Observations and Modeling for Source Characterization

    DTIC Science & Technology

    2011-02-25

    and in and around the Tijuana River plume before, during and after storm events. Data were collected in February and March of 2008 and 2009 for a...sensors. These sources include riverine inputs from the Tijuana River and two outfall plumes in the region. The UUVs were also deployed to observe...California NCOM) was used to provide boundary information to the plume resolving higher resolution mesh. For example, the Tijuana River mouth, two outfall

  12. Infrasonic observations of the June 2009 Sarychev Peak eruption, Kuril Islands: Implications for infrasonic monitoring of remote explosive volcanism

    NASA Astrophysics Data System (ADS)

    Matoza, Robin S.; Le Pichon, Alexis; Vergoz, Julien; Herry, Pascal; Lalande, Jean-Marie; Lee, Hee-il; Che, Il-Young; Rybin, Alexander

    2011-02-01

    Sarychev Peak (SP), located on Ostrov Matua, Kurils, erupted explosively during 11-16 June 2009. Whereas remote seismic stations did not record the eruption, we report atmospheric infrasound (acoustic wave ~ 0.01-20 Hz) observations of the eruption at seven infrasound arrays located at ranges of ~ 640-6400 km from SP. The infrasound arrays consist of stations of the International Monitoring System global infrasound network and additional stations operated by the Korea Institute of Geoscience and Mineral Resources. Signals at the three closest recording stations IS44 (643 km, Petropavlovsk-Kamchatskiy, Kamchatka Krai, Russia), IS45 (1690 km, Ussuriysk, Russia), and IS30 (1774 km, Isumi, Japan) represent a detailed record of the explosion chronology that correlates well with an eruption chronology based on satellite data (TERRA, NOAA, MTSAT). The eruption chronology inferred from infrasound data has a higher temporal resolution than that obtained with satellite data. Atmosphere-corrected infrasonic source locations determined from backazimuth cross-bearings of first-arrivals have a mean centroid ~ 15 km from the true location of SP. Scatter in source locations of up to ~ 100 km result from currently unresolved details of atmospheric propagation and source complexity. We observe systematic time-variations in trace-velocity, backazimuth deviation, and signal frequency content at IS44. Preliminary investigation of atmospheric propagation from SP to IS44 indicates that these variations can be attributed to solar tide variability in the thermosphere. It is well known that additional information about active volcanic processes can be learned by deploying infrasonic sensors with seismometers at erupting volcanoes. This study further highlights the significant potential of infrasound arrays for monitoring volcanic regions such as the Kurils that have only sparse seismic network coverage.

  13. Responses of the ear to low frequency sounds, infrasound and wind turbines

    PubMed Central

    Salt, Alec N.; Hullar, Timothy E.

    2010-01-01

    Infrasonic sounds are generated internally in the body (by respiration, heartbeat, coughing, etc) and by external sources, such as air conditioning systems, inside vehicles, some industrial processes and, now becoming increasingly prevalent, wind turbines. It is widely assumed that infrasound presented at an amplitude below what is audible has no influence on the ear. In this review, we consider possible ways that low frequency sounds, at levels that may or may not be heard, could influence the function of the ear. The inner ear has elaborate mechanisms to attenuate low frequency sound components before they are transmitted to the brain. The auditory portion of the ear, the cochlea, has two types of sensory cells, inner hair cells (IHC) and outer hair cells (OHC), of which the IHC are coupled to the afferent fibers that transmit “hearing” to the brain. The sensory stereocilia (“hairs”) on the IHC are “fluid coupled” to mechanical stimuli, so their responses depend on stimulus velocity and their sensitivity decreases as sound frequency is lowered. In contrast, the OHC are directly coupled to mechanical stimuli, so their input remains greater than for IHC at low frequencies. At very low frequencies the OHC are stimulated by sounds at levels below those that are heard. Although the hair cells in other sensory structures such as the saccule may be tuned to infrasonic frequencies, auditory stimulus coupling to these structures is inefficient so that they are unlikely to be influenced by airborne infrasound. Structures that are involved in endolymph volume regulation are also known to be influenced by infrasound, but their sensitivity is also thought to be low. There are, however, abnormal states in which the ear becomes hypersensitive to infrasound. In most cases, the inner ear’s responses to infrasound can be considered normal, but they could be associated with unfamiliar sensations or subtle changes in physiology. This raises the possibility that

  14. Locating industrial VOC sources with aircraft observations.

    PubMed

    Toscano, P; Gioli, B; Dugheri, S; Salvini, A; Matese, A; Bonacchi, A; Zaldei, A; Cupelli, V; Miglietta, F

    2011-05-01

    Observation and characterization of environmental pollution, focussing on Volatile Organic Compounds (VOCs), in a high-risk industrial area, are particularly important in order to provide indications on a safe level of exposure, indicate eventual priorities and advise on policy interventions. The aim of this study is to use the Solid Phase Micro Extraction (SPME) method to measure VOCs, directly coupled with atmospheric measurements taken on a small aircraft environmental platform, to evaluate and locate the presence of VOC emission sources in the Marghera industrial area. Lab analysis of collected SPME fibres and subsequent analysis of mass spectrum and chromatograms in Scan Mode allowed the detection of a wide range of VOCs. The combination of this information during the monitoring campaign allowed a model (Gaussian Plume) to be implemented that estimates the localization of emission sources on the ground.

  15. Dust devil signatures in infrasound records of the International Monitoring System

    NASA Astrophysics Data System (ADS)

    Lorenz, Ralph D.; Christie, Douglas

    2015-03-01

    We explore whether dust devils have a recognizable signature in infrasound array records, since several Comprehensive Nuclear-Test-Ban Treaty verification stations conducting continuous measurements with microbarometers are in desert areas which see dust devils. The passage of dust devils (and other boundary layer vortices, whether dust laden or not) causes a local temporary drop in pressure: the high-pass time domain filtering in microbarometers results in a "heartbeat" signature, which we observe at the Warramunga station in Australia. We also observe a ~50 min pseudoperiodicity in the occurrence of these signatures and some higher-frequency infrasound. Dust devils do not significantly degrade the treaty verification capability. The pipe arrays for spatial averaging used in infrasound monitoring degrade the detection efficiency of small devils, but the long observation time may allow a useful census of large vortices, and thus, the high-sensitivity infrasonic array data from the monitoring network can be useful in studying columnar vortices in the lower atmosphere.

  16. Infrasound and seismic detections associated with the 7 September 2015 Bangkok fireball

    NASA Astrophysics Data System (ADS)

    Caudron, Corentin; Taisne, Benoit; Perttu, Anna; Garcés, Milton; Silber, Elizabeth A.; Mialle, Pierrick

    2016-12-01

    A bright fireball was reported at 01:43:35 UTC on September 7, 2015 at a height of ˜30 km above 14.5°N, 98.9°E near Bangkok, Thailand. It had a TNT yield equivalent of 3.9 kilotons (kt), making it the largest fireball detected in South-East Asia since the ˜50 kt 2009 Sumatra bolide. Infrasonic signals were observed at four infrasound arrays that are part of the International Monitoring System (IMS) and one infrasound array located in Singapore. Acoustic bearings and event origin times inferred from array processing are consistent with the eyewitness accounts. A seismic signal associated with this event was also likely recorded at station SRDT, in Thailand. An acoustic energy equivalent of 1.15 ± 0.24 kt is derived from the Singaporean acoustic data using the period of the peak energy.

  17. Frequency-wavenumber processing for infrasound distributed arrays.

    PubMed

    Costley, R Daniel; Frazier, W Garth; Dillion, Kevin; Picucci, Jennifer R; Williams, Jay E; McKenna, Mihan H

    2013-10-01

    The work described herein discusses the application of a frequency-wavenumber signal processing technique to signals from rectangular infrasound arrays for detection and estimation of the direction of travel of infrasound. Arrays of 100 sensors were arranged in square configurations with sensor spacing of 2 m. Wind noise data were collected at one site. Synthetic infrasound signals were superposed on top of the wind noise to determine the accuracy and sensitivity of the technique with respect to signal-to-noise ratio. The technique was then applied to an impulsive event recorded at a different site. Preliminary results demonstrated the feasibility of this approach.

  18. Atmospheric infrasound propagation modelling using the reflectivity method with a direct formulation of the wind effect

    NASA Astrophysics Data System (ADS)

    Maupin, Valerie; Näsholm, Sven Peter; Schweitzer, Johannes; Gibbons, Steven J.

    2016-04-01

    We recently advocated using the reflectivity method, also known as the wavenumber integration method or fast-field program, to model atmospheric infrasound propagation at regional distances. The advantage of the reflectivity method is its ability to model the full wavefield, including diffractive effects with head waves and shadow zone arrivals, in a broad frequency range but still at a relatively low computational cost. Attenuation can easily be included, giving the possibility to analyse relative amplitudes and frequency content of the different arrivals. It has clear advantages compared with ray theory in terms of predicting phases considering the particular frequent occurrence of shadow zone arrivals in infrasound observations. Its main limitation, at least in the traditional form of the method, lies in the fact that it can only handle range-independent models. We presented earlier some reflectivity method simulations of an observed accidental explosion in Norway. Wind intensity and direction are non-negligible parameters for infrasound propagation and these are appropriately taken into account in most infrasound ray-tracing codes. On the other hand, in the previous reflectivity simulations wind was taken into account only through the effective sound speed approximation where the horizontal projection of the wind field is added to the adiabatic sound speed profiles. This approximation is appropriate for dominantly horizontal propagation but can give incorrect arrival times and shadow zone locations for waves which have a significant portion of their propagation path at more vertical incidence, like thermospheric arrivals. We present here how we have modified the original reflectivity algorithm in order to take the wind into account in a more correct fashion, and how this improvement influences the synthetics.

  19. Regional Localization with the Hawaii Island Infrasound Network

    NASA Astrophysics Data System (ADS)

    Perttu, A. B.; Garces, M. A.; Thelen, W. A.

    2013-12-01

    The Big Island of Hawaii is home to an extensive network of infrasound arrays, with additional arrays in Maui and Kauai. Four of the six Hawaii arrays are focused on Kilauea volcano. This project examines several methods for estimating source location, onset time, duration, and source energetics from regional infrasonic signals, with an emphasis on improving signal characterization. Diverse persistent natural and anthropogenic regional sources provide a data set for addressing localization with the Hawaii network. Explosions at the Pohakuloa Training Area, rock falls within the Halema'uma'u vent, and a repetitive unknown signal off the coast of Maui supply transient signals with known and unknown locations. In addition, Halema'uma'u and Pu'u O'o vents both produce infrasonic tremor with known locations. Well-constrained signal discrimination and characterization is essential for good location results. This paper presents progress in signal processing, feature extraction, and event association with standardized, self-similar, logarithmic time-frequency multiresolution algorithms. The Infrasonic Energy, Nth Octave (INFERNO) energy estimation suite of Garces (2013) is used in conjunction with the PMCC4 array processing algorithm to extract standardized signal features and parameters for improved regional association, localization, and source characterization.

  20. ASTERIA: A Balloon-Borne Experiment for Infrasound Detection

    NASA Astrophysics Data System (ADS)

    Young, Eliot; Wahl, Kerry; Ballard, Courtney; Daugherty, Emily; Dullea, Connor; Garner, Kyle; Heaney, Martin; Thom, Ian; Von Hendy, Michael; Young, Emma; Diller, Jed; Dischner, Zach; Drob, Douglas; Boslough, Mark; Brown, Peter

    2015-04-01

    ASTERIA (Aloft Stratospheric Testbed for Experimental Research on Infrasonic Activity) is a small (<20 kg) payload designed to measure infrasound disturbances from a balloon-borne platform at altitudes near 60,000 ft (~20 km). A balloon platform is expected to have two advantages over ground-based infrasound stations: a relatively benign wind environment and exposure to higher signal strengths within a stratospheric duct. ASTERIA's nominal sensitivity requirements are to measure waves between 0.1 to 20 Hz at the 0.1 Pa level with signal-to-noise ratios of 5 or better. At the time of this writing, we have tested wave sensors based on the differential pressure transducers recently flown by Bowman et al. (2014) on a NASA/HASP (High Altitude Student Payload); our modified pressure sensor was tested in a NOAA piston-bellows facility in Boulder, CO. Our goal of characterizing 0.1 Pa amplitude waves requires that combined noise sources are below the the 0.02 Pa rms level. ASTERIA carries five differential transducers with port inlets arranged a diamond-like pattern (one zenith- and one nadir-facing port, plus three horizontal ports equally spaced in azimuth). Baffling for these sensors is a hybrid of perforated tubing and porous barriers, as described in Hedlin (2014). Other noise sources of concern include the electronic amplification of the transducer voltages and low-frequency pressure waves caused by pendulum or twisting modes of the payload. We will report on our plans to characterize and reduce these noise sources. The ASTERIA payload is intended to fly on long-duration super-pressure balloons for intervals of ~100 days. We plan to conduct an experiment in the summer or fall of 2015 in which a calibrated disturbance is set off and detected simultaneously from stratospheric ASTERIA payloads and ground-based stations. References: 1) Bowman et al. 2014, "Balloons over Volcanoes Scientific Report," HASP 2014 final report. 2) Hedlin 2003, "Infrasonic Wind-noise Reduction

  1. Balloon-Borne Infrasound Detection of Energetic Bolide Events

    NASA Astrophysics Data System (ADS)

    Young, Eliot F.; Ballard, Courtney; Klein, Viliam; Bowman, Daniel; Boslough, Mark

    2016-10-01

    Infrasound is usually defined as sound waves below 20 Hz, the nominal limit of human hearing. Infrasound waves propagate over vast distances through the Earth's atmosphere: the CTBTO (Comprehensive Nuclear-Test-Ban Treaty Organization) has 48 installed infrasound-sensing stations around the world to detect nuclear detonations and other disturbances. In February 2013, several CTBTO infrasound stations detected infrasound signals from a large bolide that exploded over Chelyabinsk, Russia. Some stations recorded signals that had circumnavigated the Earth, over a day after the original event. The goal of this project is to improve upon the sensitivity of the CTBTO network by putting microphones on small, long-duration super-pressure balloons, with the overarching goal of studying the small end of the NEO population by using the Earth's atmosphere as a witness plate.A balloon-borne infrasound sensor is expected to have two advantages over ground-based stations: a lack of wind noise and a concentration of infrasound energy in the "stratospheric duct" between roughly 5 - 50 km altitude. To test these advantages, we have built a small balloon payload with five calibrated microphones. We plan to fly this payload on a NASA high-altitude balloon from Ft Sumner, NM in August 2016. We have arranged for three large explosions to take place in Socorro, NM while the balloon is aloft to assess the sensitivity of balloon-borne vs. ground-based infrasound sensors. We will report on the results from this test flight and the prospects for detecting/characterizing small bolides in the stratosphere.

  2. Can Gamma Ray Bursts be Detected Using Infrasound

    NASA Astrophysics Data System (ADS)

    Palmer, Jahi; McGruder, C.; Hetzer, C.

    2010-01-01

    CAN GAMMA RAY BURST BE DETECTED USING INFRASOUND Infrasound has been used to detect sonic disturbances in earth's atmosphere caused by terrestrial events such as earthquakes and lightning. It may be possible to detect celestial events such as Gamma Ray Bursts (GRB's) through this method. We have searched for GRB's which are known to have caused ionospheric disturbances in infrasonic data. None of the selected GRB's were found to be associated with infrasonic disturbances.

  3. Large Bubble Growth Quantified By Video and Infrasound at Mount Erebus, Antarctica

    NASA Astrophysics Data System (ADS)

    Miller, A. J. C.; Johnson, J. B.

    2014-12-01

    Mount Erebus lava lake eruptions exhibit many characteristic strombolian attributes including the ascent of a large gas slug(s) through the magma column followed by its expansion and bursting at the surface. Strombolian explosions correspond to pressurized large (>10 m radius) bubbles, which distend the lava lake surface before bursting within a few tenths of a second thus generating infrasonic impulses followed by decaying oscillations. We quantify the dynamics of bubble evolution using infrasound and time synchronized video data recording at ~30 FPS. Video footage is used to synthesize pressure time series during eruptions assuming a simple acoustic source. These synthetic pressure records are directly compared to infrasound pressure records collected at two sites located ~300 m from the lava lake source. A scaled relationship exists between infrasound and video derived pressures where video generally overestimates the volumetrically expanding source. This scaling is due to the image processing routine, which tracks and models the ejection of ballistics during eruption as an expanding hemisphere and not necessarily the expansion of a translucent gas source that is not directly visible with optical imagery. Using both data sets, we describe Erebus lava lake eruptions in three phases with smooth distension of spherical cap (P1), followed by membrane fragmentation and violent gas expulsion (P2) and finally a contraction of the volumetric gas source due to an initial over-expansion followed by re-equilibration. (P3). Specifically, P3 is identified by decaying oscillations of the pressure record which has been well modeled in laboratory experiments but never described at Erebus.

  4. Comparing near-regional and local measurements of infrasound from Mount Erebus, Antarctica: Implications for monitoring

    NASA Astrophysics Data System (ADS)

    Dabrowa, A. L.; Green, D. N.; Johnson, J. B.; Phillips, J. C.; Rust, A. C.

    2014-11-01

    amplitude and lower atmosphere effective sound speed structure. At times of increased sound speed gradient, higher amplitude decay rates are observed, consistent with increased upward refraction of acoustic energy along the propagation path. This study indicates that whilst monitoring activity levels at near-regional ranges can be successful, variable amplitude decay rate means quantitative analysis of infrasound data for eruption intensity and magnitude is not advisable without the consideration of local atmospheric sound speed structure.

  5. Southwest U.S. Seismo-Acoustic Network: An Autonomous Data Aggregation, Detection, Localization and Ground-Truth Bulletin for the Infrasound Community

    NASA Astrophysics Data System (ADS)

    Jones, K. R.; Arrowsmith, S.

    2013-12-01

    The Southwest U.S. Seismo-Acoustic Network (SUSSAN) is a collaborative project designed to produce infrasound event detection bulletins for the infrasound community for research purposes. We are aggregating a large, unique, near real-time data set with available ground truth information from seismo-acoustic arrays across New Mexico, Utah, Nevada, California, Texas and Hawaii. The data are processed in near real-time (~ every 20 minutes) with detections being made on individual arrays and locations determined for networks of arrays. The detection and location data are then combined with any available ground truth information and compiled into a bulletin that will be released to the general public directly and eventually through the IRIS infrasound event bulletin. We use the open source Earthworm seismic data aggregation software to acquire waveform data either directly from the station operator or via the Incorporated Research Institutions for Seismology Data Management Center (IRIS DMC), if available. The data are processed using InfraMonitor, a powerful infrasound event detection and localization software program developed by Stephen Arrowsmith at Los Alamos National Laboratory (LANL). Our goal with this program is to provide the infrasound community with an event database that can be used collaboratively to study various natural and man-made sources. We encourage participation in this program directly or by making infrasound array data available through the IRIS DMC or other means. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. R&A 5317326

  6. Analysis and modeling of infrasound from a four-stage rocket launch.

    PubMed

    Blom, Philip; Marcillo, Omar; Arrowsmith, Stephen

    2016-06-01

    Infrasound from a four-stage sounding rocket was recorded by several arrays within 100 km of the launch pad. Propagation modeling methods have been applied to the known trajectory to predict infrasonic signals at the ground in order to identify what information might be obtained from such observations. There is good agreement between modeled and observed back azimuths, and predicted arrival times for motor ignition signals match those observed. The signal due to the high-altitude stage ignition is found to be low amplitude, despite predictions of weak attenuation. This lack of signal is possibly due to inefficient aeroacoustic coupling in the rarefied upper atmosphere.

  7. Sub-Surface Windscreen for the Measurement of Outdoor Infrasound

    NASA Technical Reports Server (NTRS)

    Shams, Qamar A.; Burkett, Cecil G., Jr.; Comeaux, Toby; Zuckerwar, Allan J.; Weistroffer, George R.

    2008-01-01

    A windscreen has been developed that features two advantages favorable for the measurement of outdoor infrasound. First, the sub-surface location, with the top of the windscreen flush with the ground surface, minimizes the mean velocity of the impinging wind. Secondly, the windscreen material (closed cell polyurethane foam) has a sufficiently low acoustic impedance (222 times that of air) and wall thickness (0.0127 m) to provide a transmission coefficient of nearly unity over the infrasonic frequency range (0-20 Hz). The windscreen, a tightly-sealed box having internal dimensions of 0.3048 x 0.3048 x 0.3556 m, contains a microphone, preamplifier, and a cable feed thru to an external power supply. Provisions are made for rain drainage and seismic isolation. A three-element array, configured as an equilateral triangle with 30.48 m spacing and operating continuously in the field, periodically receives highly coherent signals attributed to emissions from atmospheric turbulence. The time delays between infrasonic signals received at the microphones permit determination of the bearing and elevation of the sources, which correlate well with locations of pilot reports (PIREPS) within a 320 km radius about the array. The test results are interpreted to yield spectral information on infrasonic emissions from clear air turbulence.

  8. IGRINS observations toward Class I disk sources

    NASA Astrophysics Data System (ADS)

    Lee, Seokho; Lee, Jeong-Eun; Park, Sunkyung; Jaffe, Daniel T.; Lee, Jae-Joon

    2015-08-01

    We present the high-resolution Immersion GRating INfrared spectrograph (IGRINS) spectra of Class I sources, including IRAS03445+3242 and IRAS04239+2436. These sources show the evidence of Keplerian disks; the broadened CO overtone (Δ v=2) transitions in emission and neutral metal lines (Mg I, Fe I, and Al I) in absorption. The thin Keplerian disk with a rotational velocity of ~100 km s-1 and a gas temperature of 5000 K at the innermost annulus can reproduce the CO overtone transitions including the bandhead emission. The temperature is assumed to have a power-law distribution with p=0.5. The outer colder disk or the envelope needs to fit the narrow absorption features overlaid on the broad emission lines in the CO overtone transitions. Other atomic and molecular emission lines likely radiated from the disk and/or wind are also detected.

  9. Characterizing Explosive Eruptions at Sakurajima Volcano, Japan, Using Seismic, Infrasound, Lightning and Video Data

    NASA Astrophysics Data System (ADS)

    Smith, C. M.; Behnke, S. A.; Thomas, R. J.; Edens, H. E.; Cimarelli, C.; Cigala, V.; Van Eaton, A. R.; Iguchi, M.; Miki, D.; McNutt, S. R.

    2015-12-01

    The ability to determine volcanic ash plume characteristics from seismic and/or infrasonic records would enable increased accuracy in volcanic monitoring during times of low visibility. During May-June 2015 a field deployment of 6 infrasound sensors, 2 seismometers, multiple cameras, and 10 Lightning Mapping Array (LMA) stations were deployed around Sakurajima Volcano in Japan. During one month of observations (13 May to 10 June) hundreds of explosive eruptions were observed with plume heights reaching 4.3 km above the vent. The plumes varied in duration, ash content, and physical form. The resulting explosions exhibited a variety of infrasound waveforms including the classic long-period N shape as well as events with a mixture of high and low frequencies. For a subset of larger events, peak pressures ranged from 16 to 741 Pa at a distance of 3.6 km from the vent. The seismic signals are long period and emergent with no clear P or S-waves, although high frequency ground-coupled airwaves are visible in conjunction with the infrasonic record of some of the explosive eruptions. Peak ground displacements on the vertical component ranged from 2.1 to 183 um for the same subset of events. Volcanic lightning was both visually observed and recorded on the LMA stations. One of the goals of this project to determine if there are intrinsic relationships between ash plume characteristics, such as initial velocity or acceleration, ash grain size, texture, and composition, seismic and infrasound waveforms, and the presence and type of volcanic lightning. The rich variety of observations provides a good opportunity to determine such relationships.

  10. The role of infrasounds in maintaining whale herds

    NASA Astrophysics Data System (ADS)

    Payne, Roger S.

    2004-05-01

    For whales and dolphins a basic social unit is the herd. In several species, herds have been observed to maintain the same speed, direction, and membership overnight, and while swimming in waters of near-zero visibility-evidence that individuals can stay together using nonvisual cues. The most likely such cue is sound. If whale herds are held together with sound, yet we define herds as groups of whales seen moving together, then we are using visual criteria to judge what is an acoustic phenomenon, and our conclusions about a most basic unit of cetacean social structure, the herd, are at least incomplete, and, quite possibly, worthless. By calling herds, heards, we remind ourselves that sound controls herd size. We then consider that some whale infrasound can propagate across deep water at useful intensities (even in today's ship-noise-polluted ocean) for thousands of kilometers. The distance to which blue and fin whale sounds propagate before falling below background noise is given, and the possible advantages these whales obtain from such sounds is explored. The conclusion is that by sharing information on food finds infrasonically, fin and blue whales may have developed a way to divide up the food resources of an entire ocean.

  11. The role of infrasounds in maintaining whale herds

    NASA Astrophysics Data System (ADS)

    Payne, Roger S.

    2001-05-01

    For whales and dolphins a basic social unit is the herd. In several species, herds have been observed to maintain the same speed, direction, and membership overnight, and while swimming in waters of near-zero visibility-evidence that individuals can stay together using nonvisual cues. The most likely such cue is sound. If whale herds are held together with sound, yet we define herds as groups of whales seen moving together, then we are using visual criteria to judge what is an acoustic phenomenon, and our conclusions about a most basic unit of cetacean social structure, the herd, are at least incomplete, and, quite possibly, worthless. By calling herds, heards, we remind ourselves that sound controls herd size. We then consider that some whale infrasound can propagate across deep water at useful intensities (even in today's ship-noise-polluted ocean) for thousands of kilometers. The distance to which blue and fin whale sounds propagate before falling below background noise is given, and the possible advantages these whales obtain from such sounds is explored. The conclusion is that by sharing information on food finds infrasonically, fin and blue whales may have developed a way to divide up the food resources of an entire ocean.

  12. Evaluation of Inter-Mountain Labs infrasound sensors : July 2007.

    SciTech Connect

    Hart, Darren M.

    2007-10-01

    Sandia National Laboratories has tested and evaluated three Inter Mountain Labs infrasound sensors. The test results included in this report were in response to static and tonal-dynamic input signals. Most test methodologies used were based on IEEE Standards 1057 for Digitizing Waveform Recorders and 1241 for Analog to Digital Converters; others were designed by Sandia specifically for infrasound application evaluation and for supplementary criteria not addressed in the IEEE standards. The objective of this work was to evaluate the overall technical performance of the Inter Mountain Labs (IML) infrasound sensor model SS. The results of this evaluation were only compared to relevant noise models; due to a lack of manufactures documentation notes on the sensors under test prior to testing. The tests selected for this system were chosen to demonstrate different performance aspects of the components under test.

  13. Electromagnetic geophysical observation with controlled source

    NASA Astrophysics Data System (ADS)

    Hachay, Olga; Khachay, Oleg

    2016-04-01

    In the paper the new theoretical and methodical approaches are examined for detailed investigations of the structure and state of the geological medium, and its behavior as a dynamic system in reaction to external man-made influences. To solve this problem it is necessary to use geophysical methods that have sufficient resolution and that are built on more complicated models than layered or layered-block models. One of these methods is the electromagnetic induction frequency-geometrical method with controlled sources. Here we consider new approaches using this method for monitoring rock shock media by means of natural experiments and interpretation of the practical results. That method can be used by oil production in mines, where the same events of non stability can occur. The key ideas of twenty first century geophysics from the point of view of geologist academician A.N. Dmitrievskiy [Dmitrievskiy, 2009] are as follows. "The geophysics of the twenty first century is an understanding that the Earth is a self-developing, self-supporting geo-cybernetic system, in which the role of the driving mechanism is played by the field gradients; the evolution of geological processes is a continuous chain of transformations and the interaction of geophysical fields in the litho- hydro- and atmosphere. The use of geophysical principles of a hierarchical quantum of geophysical space, non-linear effects, and the effects of reradiating geophysical fields will allow the creation of a new geophysics. The research, in which earlier only pure geophysical processes and technologies were considered, nowadays tends to include into consideration geophysical-chemical processes and technologies. This transformation will allow us to solve the problems of forecasting geo-objects and geo-processes in previously unavailable geological-technological conditions." The results obtained allow us to make the following conclusions, according to the key ideas of academician A.N. Dmitrievskiy: the rock

  14. Tracking near-surface atmospheric conditions using an infrasound network.

    PubMed

    Marcillo, O; Johnson, J B

    2010-07-01

    Continuous volcanic infrasound signal was recorded on a three-microphone network at Kilauea in July 2008 and inverted for near-surface horizontal winds. Inter-station phase delays, determined by signal cross-correlation, vary by up to 4% and are attributable to variable atmospheric conditions. The results suggest two predominant weather regimes during the study period: (1) 6-9 m/s easterly trade winds and (2) lower-intensity 2-5 m/s mountain breezes from Mauna Loa. The results demonstrate the potential of using infrasound for tracking local averaged meteorological conditions, which has implications for modeling plume dispersal and quantifying gas flux.

  15. Seismo-acoustic Signals Recorded at KSIAR, the Infrasound Array Installed at PS31

    NASA Astrophysics Data System (ADS)

    Kim, T. S.; Che, I. Y.; Jeon, J. S.; Chi, H. C.; Kang, I. B.

    2014-12-01

    One of International Monitoring System (IMS)'s primary seismic stations, PS31, called Korea Seismic Research Station (KSRS), was installed around Wonju, Korea in 1970s. It has been operated by US Air Force Technical Applications Center (AFTAC) for more than 40 years. KSRS is composed of 26 seismic sensors including 19 short period, 6 long period and 1 broad band seismometers. The 19 short period sensors were used to build an array with a 10-km aperture while the 6 long period sensors were used for a relatively long period array with a 40-km aperture. After KSRS was certified as an IMS station in 2006 by Comprehensive Nuclear Test Ban Treaty Organization (CTBTO), Korea Institute of Geoscience and Mineral Resources (KIGAM) which is the Korea National Data Center started to take over responsibilities on the operation and maintenance of KSRS from AFTAC. In April of 2014, KIGAM installed an infrasound array, KSIAR, on the existing four short period seismic stations of KSRS, the sites KS05, KS06, KS07 and KS16. The collocated KSIAR changed KSRS from a seismic array into a seismo-acoustic array. The aperture of KSIAR is 3.3 km. KSIAR also has a 100-m small aperture infrasound array at KS07. The infrasound data from KSIAR except that from the site KS06 is being transmitted in real time to KIGAM with VPN and internet line. An initial analysis on seismo-acoustic signals originated from local and regional distance ranges has been performed since May 2014. The analysis with the utilization of an array process called Progressive Multi-Channel Correlation (PMCC) detected seismo-acoustic signals caused by various sources including small explosions in relation to constructing local tunnels and roads. Some of them were not found in the list of automatic bulletin of KIGAM. The seismo-acoustic signals recorded by KSIAR are supplying a useful information for discriminating local and regional man-made events from natural events.

  16. 2013 Russian Fireball Largest Ever Detected by CTBTO Infrasound Sensors (Invited)

    NASA Astrophysics Data System (ADS)

    Pilger, C.; Ceranna, L.; Le Pichon, A.; Herry, P.; Brachet, N.; Mialle, P.; Brown, D.

    2013-12-01

    On 15 February 2013 at 03h20 UT, a large Earth impacting fireball disintegrated over the Ural Mountains near the city of Chelyabinsk. The bolide produced shock waves that blew out windows, injured hundreds of people and damaged buildings in many surrounding cities. Infrasonic waves generated by the explosion propagated over very long distances. The event was globally detected by 20 arrays part of the 44 operating infrasound IMS (International Monitoring System) stations of the CTBTO (Comprehensive Nuclear-Test-Ban Treaty Organization). This fireball event provides a prominent milestone for studying, in detail, infrasound propagation traveling twice around the globe for almost two days at distances larger than 80000 km. Therefore, its analysis offers a unique opportunity to calibrate detection and location methods and evaluate the global performance of the IMS network. The presentation will provide an overview on the global recordings and analyses. Moreover, in order to explain the detection capability of the overall operating IMS network, range-dependent propagation modeling considering both a point-like explosive source and a line source is performed.

  17. Determination of uncertainty in the estimation of velocity and direction-of-arrival for atmospheric infrasound signals

    NASA Astrophysics Data System (ADS)

    Szuberla, Curt A. L.; Olson, John V.

    2002-11-01

    Upon the detection of an atmospheric infrasound signal, the problem of precisely estimating the signal's velocity (v) and direction-of-arrival (theta) arises. Multiple sources, multipath, medium anisotropies, and other propagation effects can all degrade precision; however, uncertainty in the estimates of v and theta is fundamentally governed by array geometry and the estimation of time delays across the array. Typically, as in the Comprehensive Test Ban Treaty Organzation Provisional Technical Secretariat (CTBTO/PTS) specification for data from infrasound stations, the Cramer-Rao lower bound is invoked to ascertain the uncertainties associated with v and theta. As this theoretical lower limit is often overly conservative, a more general, and useful, approach to calculate these uncertainties is developed. Examples of this uncertainty determination are presented for typical impulsive and continuous atmospheric infrasound signals received at arrays in Windless Bight, Antarctica and Fairbanks, Alaska. Since the determination of v and theta serves as primary input to any propogation model, it is critical that uncertainties in these estimates be addressed. As an extension of this work, an interactive graphical tool is constructed to assist in the analysis of performance bounds for arbitrary array geometries and signal characteristics.

  18. Using Infrasound and Machine Learning for Monitoring Plinian Volcanic Eruptions

    NASA Astrophysics Data System (ADS)

    Ham, F. M.; Iyengar, I.; Hambebo, B. M.; Garces, M. A.; Deaton, J.; Perttu, A.; Williams, B.

    2012-12-01

    Large plinian volcanic eruptions can inject a substantial amount of volcanic gas and ash into the stratosphere. This can present a severe hazard to commercial air traffic. A hazardous Icelandic volcanic ash-eruption was reported on April 14, 2010. This resulted in London's aviation authority to issue an alert that an ash plume was moving from an eruption in Iceland towards northwestern Europe. This eruption resulted in the closure of large areas of European airspace. Large plinian volcanic eruptions radiate infrasonic signals that can be detected by a global infrasound array network. To reduce potential hazards for commercial aviation from volcanic ash, these infrasound sensor arrays have been used to detect infrasonic signals released by sustained volcanic eruptions that can inject ash into the stratosphere at aircraft's cruising altitudes, typically in the order of 10km. A system that is capable of near, real-time eruption detection and discrimination of plinian eruptions from other natural phenomena that can produce infrasound with overlapping spectral content (0.01 to 0.1 Hz) is highly desirable to provide ash-monitoring for commercial aviation. In the initial study, cepstral features were extracted from plinian volcanic eruptions and mountain associated wave infrasound signals. These feature vectors were then used to train and test a two-module neural network classifier (radial basis function neural networks were used for each module). One module is dedicated to classifying plinian volcanic eruptions, the other mountain associated waves. Using an independent validation dataset, the classifier's correct classification rate was 91.5%. Then a different two-module neural network classifier was designed to discriminate between plinian volcanic eruptions and a collection of infrasound signals that are not-of-interest but have spectral content that overlaps with the volcano signals. One module is again dedicated to classifying plinian volcanic eruptions, however, in

  19. Investigating the tremor source process at Fuego volcano, Guatemala through bench-scale analogue modeling

    NASA Astrophysics Data System (ADS)

    Lyons, J. J.; Ichihara, M.; Lees, J. M.; Waite, G. P.

    2011-12-01

    the seismic and infrasound tremor by constructing an analogue model that can reproduce some of the same tremor characteristics observed in the natural samples. The model consists of a simple conduit connected to a tank containing a viscoelastic fluid. A flapping membrane is placed in the conduit and is oscillated by the flow of compressed gas. The signal is then pumped through the viscoelastic fluid. Broadband pressure transducers record pressure changes in the conduit up-and downstream of the signal generator, and three broadband microphones positioned around the tank record the signal transmitted in the atmosphere. In addition, high-speed and standard video cameras record the experiment, in particular the details of the injection of the gas into the fluid. By varying the gas pressure, we produce bubble bursting or harmonic tremor, and by controlling the elasticity in the conduit and depth of the fluid we reproduce some of the signal characteristics observed in the Fuego tremor, thus providing further constraint on the source mechanics of seismic and infrasound tremor.

  20. Kernel-based machine learning techniques for infrasound signal classification

    NASA Astrophysics Data System (ADS)

    Tuma, Matthias; Igel, Christian; Mialle, Pierrick

    2014-05-01

    Infrasound monitoring is one of four remote sensing technologies continuously employed by the CTBTO Preparatory Commission. The CTBTO's infrasound network is designed to monitor the Earth for potential evidence of atmospheric or shallow underground nuclear explosions. Upon completion, it will comprise 60 infrasound array stations distributed around the globe, of which 47 were certified in January 2014. Three stages can be identified in CTBTO infrasound data processing: automated processing at the level of single array stations, automated processing at the level of the overall global network, and interactive review by human analysts. At station level, the cross correlation-based PMCC algorithm is used for initial detection of coherent wavefronts. It produces estimates for trace velocity and azimuth of incoming wavefronts, as well as other descriptive features characterizing a signal. Detected arrivals are then categorized into potentially treaty-relevant versus noise-type signals by a rule-based expert system. This corresponds to a binary classification task at the level of station processing. In addition, incoming signals may be grouped according to their travel path in the atmosphere. The present work investigates automatic classification of infrasound arrivals by kernel-based pattern recognition methods. It aims to explore the potential of state-of-the-art machine learning methods vis-a-vis the current rule-based and task-tailored expert system. To this purpose, we first address the compilation of a representative, labeled reference benchmark dataset as a prerequisite for both classifier training and evaluation. Data representation is based on features extracted by the CTBTO's PMCC algorithm. As classifiers, we employ support vector machines (SVMs) in a supervised learning setting. Different SVM kernel functions are used and adapted through different hyperparameter optimization routines. The resulting performance is compared to several baseline classifiers. All

  1. A dedicated pistonphone for absolute calibration of infrasound sensors at very low frequencies

    NASA Astrophysics Data System (ADS)

    He, Wen; He, Longbiao; Zhang, Fan; Rong, Zuochao; Jia, Shushi

    2016-02-01

    Aimed at the absolute calibration of infrasound sensors at very low frequencies, an upgraded and improved infrasonic pistonphone has been developed. The pistonphone was designed such that a very narrow clearance between the piston and its guide was realized based on an automatically-centered clearance-sealing structure, and a large volume rigid-walled chamber was also adopted, which improved the leakage time-constant of the chamber. A composite feedback control system was applied to the electromagnetic vibrator to control the precise motion of the piston. Performance tests and uncertainty analysis show that the leakage time-constant is so large, and the distortion of the sound pressure is so small, that the pistonphone can be used as a standard infrasound source in the frequency range from 0.001 Hz to 20 Hz. The low frequency property of the pistonphone has been verified through calibrating low frequency microphones. Comparison tests with the reciprocity method have shown that the pressure sensitivities from the pistonphone are not only reliable at common frequencies but also have smaller uncertainties at low frequencies.

  2. The use of an infrasound microphone array to study wind noise spectra and correlation

    NASA Astrophysics Data System (ADS)

    Shields, F. Douglas; Talmadge, Carrick

    2003-04-01

    A three dimensional array of infrasound sensors of original design has been constructed and used to study wind generated pressure signals in the frequency range from 0.1 to 100 Hz. The ten sensors in each arm of the array are 2 feet apart. An ultrasonic anemometer ten feet off the ground was used to make simultaneous measurements of the three components of the wind velocity. Several sets of data have been taken in open fields with different ground cover. The data have been spectrally analyzed and, over a limited frequency range, the velocity and pressure variations found to obey the 5/3 and 7/3 power law that is expected for the inertial range. A study has also been made of the dependence of the correlation between the pressure signals and the sensor separation. The coherence of the pressure signals indicates that the convection velocity is nearly independent of frequency, and the correlation has an exponentially decaying sinusoidal dependence on the sensor separation. The array has also been used successfully to localize infrasound sources. [Work supported by the U.S. Army Armament Research Development and Engineering Center.

  3. XMM-Newton and Chandra observations of SHEEP sources

    NASA Astrophysics Data System (ADS)

    Georgantopoulos, I.; Nandra, K.; Brotherton, M.; Georgakakis, A.; Papadakis, I. E.; O'Neill, P.

    2006-04-01

    We present Chandra and XMM-Newton observations of 12 bright [f(2-10keV) > 10-13ergcm-2s-1] sources from the ASCA search for the High Energy Extragalactic Population (SHEEP) survey. Most of these have been either not observed or not detected previously with the ROSAT mission, and therefore they constitute a sample biased towards hard sources. The Chandra observations are important in locating the optical counterpart of the X-ray sources with accuracy. Optical spectroscopic observations show that our sample is associated with both narrow-line (NL) (six objects) and broad-line (BL) active galactic nuclei (AGN) (five objects), with one source remaining unidentified. Our sources cover the redshift range 0.04-1.29, spanning luminosities from 1042 to 1045ergs-1 (2-10 keV). The NL sources have preferentially lower redshift (and luminosity) compared to the BL ones. This can be most easily explained in a model where the NL AGN are intrinsically less luminous than the BL ones in line with the results of Steffen et al. The X-ray spectral fittings show a roughly equal number of obscured (NH > 1022cm-2) and unobscured (NH < 1022cm-2) sources. There is a clear tendency for obscured sources to be associated with NL AGN and unobscured sources with BL ones. However, there is a marked exception with the highest obscuring column observed at a BL AGN at a redshift of z= 0.5.

  4. Evaluation of wind and temperature profiles from ECMWF analysis on two hemispheres using volcanic infrasound

    NASA Astrophysics Data System (ADS)

    Assink, J. D.; Pichon, A. Le; Blanc, E.; Kallel, M.; Khemiri, L.

    2014-07-01

    In this paper, we evaluate vertical wind and temperature profiles that are produced by the European Centre for Medium-Range Weather Forecasts (ECMWF) atmospheric analysis. The evaluation is carried out on both hemispheres: we make use of stratospheric infrasound arrivals from Mount Etna (37°N) and Mount Yasur (22°S). The near-continuous, high activity of both volcanoes permits the study of stratospheric propagation along well-defined paths with a time resolution ranging from hours to multiple years. Infrasound observables are compared to theoretical estimates obtained from acoustic propagation modeling using the ECMWF analysis. While a first-order agreement is found for both hemispheres, we report on significant discrepancies around some of the equinox periods and other intervals during which the atmosphere is in a state of transition and dynamical oscillations of the atmosphere dominate over the general circulation. We present an inversion study in which we make use of measured trace velocity estimates to estimate first-order effective sound speed model updates in a Bayesian framework. Deviations from the a priori models around the stratopause up to 10% (≈ 30 m s-1) are estimated. Such updates are in line with the results from comparisons between ECMWF analysis and observations from lidar and microwave Doppler spectroradiometer facilities that were colocated during the course of the 2012-2013 Atmospheric dynamics Research and InfraStructure in Europe (ARISE) measurement campaign.

  5. IVS Observation of ICRF2-Gaia Transfer Sources

    NASA Astrophysics Data System (ADS)

    Le Bail, K.; Gipson, J. M.; Gordon, D.; MacMillan, D. S.; Behrend, D.; Thomas, C. C.; Bolotin, S.; Himwich, W. E.; Baver, K. D.; Corey, B. E.; Titus, M.; Bourda, G.; Charlot, P.; Collioud, A.

    2016-03-01

    The second realization of the International Celestial Reference Frame (ICRF2), which is the current fundamental celestial reference frame adopted by the International Astronomical Union, is based on Very Long Baseline Interferometry (VLBI) data at radio frequencies in X band and S band. The European Space Agency’s Gaia mission, launched on 2013 December 19, started routine scientific operations in 2014 July. By scanning the whole sky, it is expected to observe ∼500,000 Quasi Stellar Objects in the optical domain an average of 70 times each during the five years of the mission. This means that, in the future, two extragalactic celestial reference frames, at two different frequency domains, will coexist. It will thus be important to align them very accurately. In 2012, the Laboratoire d’Astrophysique de Bordeaux (LAB) selected 195 sources from ICRF2 that will be observed by Gaia and should be suitable for aligning the radio and optical frames: they are called ICRF2-Gaia transfer sources. The LAB submitted a proposal to the International VLBI Service (IVS) to regularly observe these ICRF2-Gaia transfer sources at the same rate as Gaia observes them in the optical realm, e.g., roughly once a month. We describe our successful effort to implement such a program and report on the results. Most observations of the ICRF2-Gaia transfer sources now occur automatically as part of the IVS source monitoring program, while a subset of 37 sources requires special attention. Beginning in 2013, we scheduled 25 VLBI sessions devoted in whole or in part to measuring these 37 sources. Of the 195 sources, all but one have been successfully observed in the 12 months prior to 2015 September 01. Of the sources, 87 met their observing target of 12 successful sessions per year. The position uncertainties of all of the ICRF2-Gaia transfer sources have improved since the start of this observing program. For a subset of 24 sources whose positions were very poorly known, the uncertainty

  6. Detailed observations of the source of terrestrial narrowband electromagnetic radiation

    NASA Technical Reports Server (NTRS)

    Kurth, W. S.

    1982-01-01

    Detailed observations are presented of a region near the terrestrial plasmapause where narrowband electromagnetic radiation (previously called escaping nonthermal continuum radiation) is being generated. These observations show a direct correspondence between the narrowband radio emissions and electron cyclotron harmonic waves near the upper hybrid resonance frequency. In addition, electromagnetic radiation propagating in the Z-mode is observed in the source region which provides an extremely accurate determination of the electron plasma frequency and, hence, density profile of the source region. The data strongly suggest that electrostatic waves and not Cerenkov radiation are the source of the banded radio emissions and define the coupling which must be described by any viable theory.

  7. Infrasound as a Geophysical Probe Using Earth as a Venus Analog

    NASA Astrophysics Data System (ADS)

    Komjathy, Attila; Cutts, James; Pauken, Michael; Kedar, Sharon; Smrekar, Suzanne

    2016-10-01

    JPL is in a process of developing an instrument to measure seismic activity on Venus by detecting infrasonic waves in the atmosphere. The overall objective of this research is to demonstrate the feasibility of using sensitive barometers to detect infrasonic signals from seismic and explosive activity on Venus from a balloon platform. Because of Venus' dense atmosphere, seismic signatures from even small quakes (magnitude ~3) are effectively coupled into the atmosphere. The seismic signals are known to couple about 60 times more efficiently into the atmosphere on Venus than on Earth. It was found that almost no attenuation below 80 km on Venus for frequency less than 1Hz. Whereas wind noise is a major source of background noise for terrestrial infrasonic arrays, it is expected that a balloon platform, which drifts with winds will be capable of very sensitive measurements with low noise.In our research we will demonstrate and apply techniques for discriminating upward propagating waves from a seismic event by making measurements with two or more infrasonic sensors using very sensitive barometers on a tether deployed from the balloon in a series of earth-based tests. We will first demonstrate and validate the technique using an artificial infrasound source in a deployment from a hot air balloon on Earth and then extend it with longer duration flights in the troposphere and stratosphere.We will report results on the first flight experiment that will focus on using the barometer instruments on a tethered helium-filled balloon. The balloon flight will be conducted in the vicinity of a known seismic source generated by a seismic hammer. Earlier tests conducted by Sandia National Laboratory demonstrated that this is a highly reproducible source of seismic and acoustic energy using infrasound sensors. The results of the experiments are intended to validate the two-barometer signal processing approach using a well-characterized point signal source.

  8. Identification of blasting sources in the Dobrogea seismogenic region, Romania using seismo-acoustic signals

    NASA Astrophysics Data System (ADS)

    Ghica, Daniela Veronica; Grecu, Bogdan; Popa, Mihaela; Radulian, Mircea

    2016-10-01

    In order to discriminate between quarry blasts and earthquakes observed in the Dobrogea seismogenic region, a seismo-acoustic analysis was performed on 520 events listed in the updated Romanian seismic catalogue from January 2011 to December 2012. During this time interval, 104 seismo-acoustic events observed from a distance between 110 and 230 km and backazimuth interval of 110-160° from the IPLOR infrasound array were identified as explosions by associating with infrasonic signals. WinPMCC software for interactive analysis was applied to detect and characterize infrasonic signals in terms of backazimuth, speed and frequency content. The measured and expected values of both backazimuths and arrival times for the study events were compared in order to identify the sources of infrasound. Two predominant directions for seismo-acoustic sources' aligning were observed, corresponding to the northern and central parts of Dobrogea, and these directions are further considered as references in the process of discriminating explosions from earthquakes. A predominance of high-frequency detections (above 1 Hz) is also observed in the infrasound data. The strong influence of seasonally dependent stratospheric winds on the IPLOR detection capability limits the efficiency of the discrimination procedure, as proposed by this study.

  9. Can earthquake source inversion benefit from rotational ground motion observations?

    NASA Astrophysics Data System (ADS)

    Igel, H.; Donner, S.; Reinwald, M.; Bernauer, M.; Wassermann, J. M.; Fichtner, A.

    2015-12-01

    With the prospects of instruments to observe rotational ground motions in a wide frequency and amplitude range in the near future we engage in the question how this type of ground motion observation can be used to solve seismic inverse problems. Here, we focus on the question, whether point or finite source inversions can benefit from additional observations of rotational motions. In an attempt to be fair we compare observations from a surface seismic network with N 3-component translational sensors (classic seismometers) with those obtained with N/2 6-component sensors (with additional colocated 3-component rotational motions). Thus we keep the overall number of traces constant. Synthetic seismograms are calculated for known point- or finite-source properties. The corresponding inverse problem is posed in a probabilistic way using the Shannon information content as a measure how the observations constrain the seismic source properties. The results show that with the 6-C subnetworks the source properties are not only equally well recovered (even that would be benefitial because of the substantially reduced logistics installing N/2 sensors) but statistically significant some source properties are almost always better resolved. We assume that this can be attributed to the fact the (in particular vertical) gradient information is contained in the additional rotational motion components. We compare these effects for strike-slip and normal-faulting type sources. Thus the answer to the question raised is a definite "yes". The challenge now is to demonstrate these effects on real data.

  10. Looking for a correlation between infrasound and volcanic gas in strombolian explosions by using high resolution UV spectroscopy and thermal imagery

    NASA Astrophysics Data System (ADS)

    Delle Donne, Dario; Tamburello, Giancarlo; Ripepe, Maurizio; Aiuppa, Alessandro

    2014-05-01

    According to the linear theory of sound, acoustic pressure propagating in a homogeneous atmosphere can be modelled in terms of the rate of change of a volumetric source. At open-vent volcanoes, this acoustic source process is commonly related to the explosive dynamics triggered by the rise, expansion and bursting of a gas slug at the magma free surface with the conduit. Just before an explosion, the magma surface will undergo deformation by the expanding gas slug. The deformation of the magma surface will then produce an equivalent displacement of the atmosphere, inducing a volumetric compression and generating an excess pressure that scales to the rate of volumetric change of the atmosphere displaced. Linear theory of sound thus predicts that pressure amplitude of infrasonic waves associated to volcanic explosions should be generated by the first time-derivative of the gas mass flux during the burst. In some cases a correlation between the first time-derivative and the SO2 mass flux has been found. However no clear correlation has yet been established between infrasonic amplitude and total ejected gas mass; therefore, the origin of infrasound in volcanic systems remains matter of debate. In the framework of the FP7-ERC BRIDGE Project, we tested different possible hypotheses on the acoustic source model, by correlating infrasound with the total gas mass retrieved from high-resolution UV spectroscopy techniques (UV camera). Experiments were conducted at Stromboli volcano (Italy), where we also employed a thermal camera to measure the total fragments/gas mass. Both techniques allowed independent estimation of total mass flux of gas and fragments within the volcanic plume. During the experiments, explosions detected by the UV camera emitted between 2 and 55 kg SO2, corresponding to SO2 peak fluxes of 0.1-0.8 kg/s. SO2 mass was converted into a total (maximum) erupted gas of 1310 kg, which is generating a peak pressure of ~8 Pa recorded at ~450 m from the source vent

  11. Test definitions for the evaluation of infrasound sensors.

    SciTech Connect

    Kromer, Richard Paul; Hart, Darren M.; Harris, James Mark

    2007-07-01

    Most test methodologies referenced in this Test Definition and Test Procedures were designed by Sandia specifically for geophysical instrumentation evaluation. When appropriate, test instrumentation calibration is traceable to the National Institute for Standards Technology (NIST). The objectives are to evaluate the overall technical performance of the infrasound sensor. The results of these evaluations can be compared to the manufacturer's specifications and any relevant application requirements or specifications.

  12. Infrasound Monitoring of Local, Regional and Global Events

    DTIC Science & Technology

    2007-09-01

    INFRASOUND MONITORING OF LOCAL, REGIONAL AND GLOBAL EVENTS Stephen J. Arrowsmith and Douglas O. ReVelle Los Alamos National Laboratory Sponsored...State seismo-acoustic network and identify 206 local and regional infrasonic events in a dataset comprising 28 days of data. We detect multiple signals...from mining explosions at two sites in Washington State, including 5 events that were recorded in a regional seismic bulletin. We also automatically

  13. Observations of galactic X-ray sources by OSO-7

    NASA Technical Reports Server (NTRS)

    Markert, T. H.; Canizares, C. R.; Clark, G. W.; Hearn, D. R.; Li, F. K.; Sprott, G. F.; Winkler, P. F.

    1977-01-01

    We present the MIT data from the OSO-7 satellite for observations of the galactic plane between 1971 and 1974. A number of sources discovered in the MIT all-sky survey are described in detail: MX 0049 + 59, MX 0836 - 42, MX 1353 - 64, MX 1406 - 61, MX 1418 - 61, MX 1709 - 40, and MX 1608 - 52 (the persistent source suggested to be associated with the X-ray burst source XB 1608 - 52). Upper limits to the X-ray emission from a number of interesting objects are also derived. General results describing all of our observations of galactic sources are presented. Specifically, we display the number-intensity diagrams, luminosity functions, and color-color diagrams for all of the sources we detected. The data are divided between disk and bulge populations, and the characteristics of the two groups are contrasted. Finally, the concept of X-ray source populations and the relationship of globular cluster sources and burst sources to the disk and bulge populations are discussed.

  14. Siberian Arctic black carbon sources constrained by model and observation

    NASA Astrophysics Data System (ADS)

    Winiger, Patrik; Andersson, August; Eckhardt, Sabine; Stohl, Andreas; Semiletov, Igor P.; Dudarev, Oleg V.; Charkin, Alexander; Shakhova, Natalia; Klimont, Zbigniew; Heyes, Chris; Gustafsson, Örjan

    2017-02-01

    Black carbon (BC) in haze and deposited on snow and ice can have strong effects on the radiative balance of the Arctic. There is a geographic bias in Arctic BC studies toward the Atlantic sector, with lack of observational constraints for the extensive Russian Siberian Arctic, spanning nearly half of the circum-Arctic. Here, 2 y of observations at Tiksi (East Siberian Arctic) establish a strong seasonality in both BC concentrations (8 ngṡm‑3 to 302 ngṡm‑3) and dual-isotope–constrained sources (19 to 73% contribution from biomass burning). Comparisons between observations and a dispersion model, coupled to an anthropogenic emissions inventory and a fire emissions inventory, give mixed results. In the European Arctic, this model has proven to simulate BC concentrations and source contributions well. However, the model is less successful in reproducing BC concentrations and sources for the Russian Arctic. Using a Bayesian approach, we show that, in contrast to earlier studies, contributions from gas flaring (6%), power plants (9%), and open fires (12%) are relatively small, with the major sources instead being domestic (35%) and transport (38%). The observation-based evaluation of reported emissions identifies errors in spatial allocation of BC sources in the inventory and highlights the importance of improving emission distribution and source attribution, to develop reliable mitigation strategies for efficient reduction of BC impact on the Russian Arctic, one of the fastest-warming regions on Earth.

  15. Siberian Arctic black carbon sources constrained by model and observation.

    PubMed

    Winiger, Patrik; Andersson, August; Eckhardt, Sabine; Stohl, Andreas; Semiletov, Igor P; Dudarev, Oleg V; Charkin, Alexander; Shakhova, Natalia; Klimont, Zbigniew; Heyes, Chris; Gustafsson, Örjan

    2017-02-14

    Black carbon (BC) in haze and deposited on snow and ice can have strong effects on the radiative balance of the Arctic. There is a geographic bias in Arctic BC studies toward the Atlantic sector, with lack of observational constraints for the extensive Russian Siberian Arctic, spanning nearly half of the circum-Arctic. Here, 2 y of observations at Tiksi (East Siberian Arctic) establish a strong seasonality in both BC concentrations (8 ng⋅m(-3) to 302 ng⋅m(-3)) and dual-isotope-constrained sources (19 to 73% contribution from biomass burning). Comparisons between observations and a dispersion model, coupled to an anthropogenic emissions inventory and a fire emissions inventory, give mixed results. In the European Arctic, this model has proven to simulate BC concentrations and source contributions well. However, the model is less successful in reproducing BC concentrations and sources for the Russian Arctic. Using a Bayesian approach, we show that, in contrast to earlier studies, contributions from gas flaring (6%), power plants (9%), and open fires (12%) are relatively small, with the major sources instead being domestic (35%) and transport (38%). The observation-based evaluation of reported emissions identifies errors in spatial allocation of BC sources in the inventory and highlights the importance of improving emission distribution and source attribution, to develop reliable mitigation strategies for efficient reduction of BC impact on the Russian Arctic, one of the fastest-warming regions on Earth.

  16. In-situ comparison calibration of infrasound array elements

    NASA Astrophysics Data System (ADS)

    Gabrielson, T. B.

    2009-12-01

    A typical infrasound array element consists of an infrasonic sensor connected to a multiple-pipe or porous-hose system for reduction of wind noise. While the frequency response of the sensor itself may be known, the wind-noise reduction system can modify that response. One approach to measuring the actual frequency response in situ is to perform a comparison calibration using ambient noise. The reference sensor must have a sufficiently low self noise and have a well characterized frequency response over the band of interest. In the cases presented here, three reference sensors are placed and summed to form a virtual reference at the geometric center of the pipe system. Under low-wind conditions, coherence between the virtual reference and the infrasound element is typically greater than 0.8 from 0.01 to 8 Hz. Proper combination of auto- and cross-spectral averages over a several-hour period produces an estimate of the response of the infrasound system relative to that of the virtual reference. Measured coherence and the consistency between the magnitude and the phase provide quality checks on the process. [Funded by the US Army Space and Missile Defense Command

  17. Impact of mountain gravity waves on infrasound propagation

    NASA Astrophysics Data System (ADS)

    Damiens, Florentin; Lott, François; Millet, Christophe

    2016-04-01

    Linear theory of acoustic propagation is used to analyze how mountain waves can change the characteristics of infrasound signals. The mountain wave model is based on the integration of the linear inviscid Taylor-Goldstein equation forced by a nonlinear surface boundary condition. For the acoustic propagation we solve the wave equation using the normal mode method together with the effective sound speed approximation. For large-amplitude mountain waves we use direct numerical simulations to compute the interactions between the mountain waves and the infrasound component. It is shown that the mountain waves perturb the low level waveguide, which leads to significant acoustic dispersion. The mountain waves also impact the arrival time and spread of the signals substantially and can produce a strong absorption of the wave signal. To interpret our results we follow each acoustic mode separately and show which mode is impacted and how. We also show that the phase shift between the acoustic modes over the horizontal length of the mountain wave field may yield to destructive interferences in the lee side of the mountain, resulting in a new form of infrasound absorption. The statistical relevance of those results is tested using a stochastic version of the mountain wave model and large enough sample sizes.

  18. VLBI observations of Infrared-Faint Radio Sources

    NASA Astrophysics Data System (ADS)

    Middelberg, Enno; Phillips, Chris; Norris, Ray; Tingay, Steven

    2006-10-01

    We propose to observe a small sample of radio sources from the ATLAS project (ATLAS = Australia Telescope Large Area Survey) with the LBA, to determine their compactness and map their structures. The sample consists of three radio sources with no counterpart in the co-located SWIRE survey (3.6 um to 160 um), carried out with the Spitzer Space Telescope. This rare class of sources, dubbed Infrared-Faint Radio Sources, or IFRS, is inconsistent with current galaxy evolution models. VLBI observations are an essential way to obtain further clues on what these objects are and why they are hidden from infrared observations: we will map their structure to test whether they resemble core-jet or double-lobed morphologies, and we will measure the flux densities on long baselines, to determine their compactness. Previous snapshot-style LBA observations of two other IFRS yielded no detections, hence we propose to use disk-based recording with 512 Mbps where possible, for highest sensitivity. With the observations proposed here, we will increase the number of VLBI-observed IFRS from two to five, soon allowing us to draw general conclusions about this intriguing new class of objects.

  19. Infrasound Sensor and Porous-Hose Filter Characterization Results

    NASA Astrophysics Data System (ADS)

    Hart, D. M.; Harris, J. M.

    2008-12-01

    The Ground-Based Nuclear Explosion Monitoring Research and Development (GNEM R&D) program at Sandia National Laboratories (SNL) is regarded as the primary center for unbiased expertise in testing and evaluation of geophysical sensors and instrumentation for nuclear explosion monitoring. Over the past year much of our work has focused in the area of infrasound sensor characterization through the continuing development of an infrasound sensor characterization test-bed. Our main areas of focus have been in new sensor characterization and understanding the effects of porous-hose filters for reducing acoustic background signals. Three infrasound sensors were evaluated for characteristics of instrument response, linearity and self-noise. The sensors tested were Chaparral Physics model 2.5 low-gain, New Mexico Tech All-Sensor and the Inter-Mountain Labs model SS avalanche sensor. For the infrasound sensors tested, the test results allow us to conclude that two of the three sensors had sufficiently quiet noise floor to be at or below the Acoustic low-noise model from 0.1 to 7 Hz, which make those sensors suitable to explosion monitoring. The other area of focus has been to understand the characteristics of porous-hose filters used at some monitoring sites. For this, an experiment was designed in which two infrasound sensors were co- located. One sensor was connected to a typical porous-hose spatial filter consisting of eight individual hoses covering a 30m aperture and the second sensor was left open to unimpeded acoustic input. Data were collected for several days, power spectrum computed for two-hour windows and the relative gain of the porous-hose filters were estimated by dividing the power spectrum. The porous-hose filter appears to attenuate less than 3 dB (rel 1 Pa**2/Hz) below 0.1 Hz and as much as 25 dB at 1 Hz and between 20 to 10 dB above 10 Hz. Several more experiments will be designed to address the effects of different characteristics of the individual porous

  20. Further observations of the burst source MXB 1728-34

    NASA Technical Reports Server (NTRS)

    Hoffman, J. A.; Lewin, W. H. G.; Doty, J.

    1977-01-01

    MXB 1728-34 has been observed by the SAS 3 observatory on eight occasions. It was bursting 95-100 per cent of the time, with burst intervals from 4 to 8 hr. The burst intervals were not correlated with the burst intensities. Seven relatively hard bursts occurring in July 1976 were all observed at energies up to about 30 keV. Following each of these bursts, enhanced X-ray emission was observed for several minutes, with a much softer spectrum than that of the bursts themselves. No periodic pulsations were observed from the associated steady source.

  1. Radio observations in the fields of COS-B gamma ray sources. IV - First quadrant sources

    NASA Technical Reports Server (NTRS)

    Ozel, M. E.; Schlickeiser, R.; Sieber, W.; Younis, S.

    1988-01-01

    The field of five COS-B gamma-ray sources in the first galactic quadrant have been mapped using the Effelsberg radio telescope at several frequencies. Candidate objects as potential radio counterparts of gamma-ray sources are discussed in the light of current observations; however, mostly being due to the crowded nature of the radio fields, no clear identification has been possible.

  2. Infrasound Generation from the HH Seismic Hammer.

    SciTech Connect

    Jones, Kyle Richard

    2014-10-01

    The HH Seismic hammer is a large, "weight-drop" source for active source seismic experiments. This system provides a repetitive source that can be stacked for subsurface imaging and exploration studies. Although the seismic hammer was designed for seismological studies it was surmised that it might produce energy in the infrasonic frequency range due to the ground motion generated by the 13 metric ton drop mass. This study demonstrates that the seismic hammer generates a consistent acoustic source that could be used for in-situ sensor characterization, array evaluation and surface-air coupling studies for source characterization.

  3. Multiwavelength observations of unidentified high energy gamma-ray sources

    NASA Technical Reports Server (NTRS)

    Halpern, Jules P.

    1995-01-01

    As was the case for COS B, the majority of high-energy (greater than 100 MeV) gamma-ray sources detected by the EGRET instrument on GRO are not immediately identifiable with catalogued objects at other wavelengths. These persistent gamma-ray sources are, next to the gamma-ray bursts, the least understood objects in the universe. This two year investigation is intended to support the analysis, correlation, and theoretical interpretation of data that we are obtaining at x-ray, optical, and radio wavelengths in order to render the gamma-ray data interpretable. This second year was devoted to studies of unidentified gamma-ray sources from the first EGRET catalog, similar to previous observations. Efforts have concentrated on the sources at low and intermediate Galactic latitudes, which are the most plausible pulsar candidates.

  4. Classification, Characterization, and Automatic Detection of Volcanic Explosion Complexity using Infrasound

    NASA Astrophysics Data System (ADS)

    Fee, D.; Matoza, R. S.; Lopez, T. M.; Ruiz, M. C.; Gee, K.; Neilsen, T.

    2014-12-01

    Infrasound signals from volcanoes represent the acceleration of the atmosphere during an eruption and have traditionally been classified into two end members: 1) "explosions" consisting primarily of a high amplitude bi-polar pressure pulse that lasts a few to tens of seconds, and 2) "tremor" or "jetting" consisting of sustained, broadband infrasound lasting for minutes to hours. However, as our knowledge and recordings of volcanic eruptions have increased, significant infrasound signal diversity has been found. Here we focus on identifying and characterizing trends in volcano infrasound data to help better understand eruption processes. We explore infrasound signal metrics that may be used to quantitatively compare, classify, and identify explosive eruptive styles by systematic analysis of the data. We analyze infrasound data from short-to-medium duration explosive events recorded during recent infrasound deployments at Sakurajima Volcano, Japan; Karymsky Volcano, Kamchatka; and Tungurahua Volcano, Ecuador. Preliminary results demonstrate that a great variety of explosion styles and flow behaviors from these volcanoes can produce relatively similar bulk acoustic waveform properties, such as peak pressure and event duration, indicating that accurate classification of physical eruptive styles requires more advanced field studies, waveform analyses, and modeling. Next we evaluate the spectral and temporal properties of longer-duration tremor and jetting signals from large eruptions at Tungurahua Volcano; Redoubt Volcano, Alaska; Augustine Volcano, Alaska; and Nabro Volcano, Eritrea, in an effort to identify distinguishing infrasound features relatable to eruption features. We find that unique transient signals (such as repeated shocks) within sustained infrasound signals can provide critical information on the volcanic jet flow and exhibit a distinct acoustic signature to facilitate automatic detection. Automated detection and characterization of infrasound associated

  5. Modeling of Jovian Hectometric Radiation Source Locations: Ulysses Observations

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.; Reiner, M. J.

    1996-01-01

    The Unified Radio and Plasma Wave (URAP) experiment on Ulysses has provided unique high latitude measurements of Jovian hectometric radiation (HOM) during its encounter with Jupiter in February 1992. URAP was the first radio instrument in the Jovian environment with radio direction-finding capability, which was previously used to determine the HOM source locations in the Jovian magnetosphere. These initial source location determinations were based on several assumptions, including the neglect of refractive effects, which may be tested. We have, for the first time, combined the measured incident ray-direction at the spacecraft with a model magnetosphere to directly trace the rays back to the HOM source. We concentrate on the observations of HOM from high northern latitudes when Ulysses was at distances less than 15 R(sub j). The three- dimensional ray-tracing calculations presented here indicate that the HOM sources probably lie on L shells in the range 3 less than or approximately equal to L less than 7 (tilted dipole magnetic field model) consistent with previous determinations that ignored the effects of refraction. The ray-tracing results, however, indicate that wave refraction due to the Io torus and the magnetic field can significantly influence the precise source location. We show that constraints on the locations imposed by the gyroemission mechanism suggest that the lo torus density may have experienced temporal and/or spatial fluctuations during the Ulysses observations of HOM. Finally, in the cold plasma approximation we demonstrate that even if the emission were nearly linearly polarized near the source region, almost circular polarization will be observed at Ulysses, in agreement with observations.

  6. Commercial observation satellites: broadening the sources of geospatial data

    NASA Astrophysics Data System (ADS)

    Baker, John C.; O'Connell, Kevin M.; Venzor, Jose A.

    2002-09-01

    Commercial observation satellites promise to broaden substantially the sources of imagery data available to potential users of geospatial data and related information products. We examine the new trend toward private firms acquiring and operating high-resolution imagery satellites. These commercial observation satellites build on the substantial experience in Earth observation operations provided by government-owned imaging satellites for civilian and military purposes. However, commercial satellites will require governments and companies to reconcile public and private interests in allowing broad public access to high-resolution satellite imagery data without creating national security risks or placing the private firms at a disadvantage compared with other providers of geospatial data.

  7. Isis 1 observations at the source of auroral kilometric radiation

    NASA Technical Reports Server (NTRS)

    Benson, R. F.; Calvert, W.

    1979-01-01

    Observations of auroral kilometric radiation (AKR) were made by Isis 1 in the source region. The radiation is found to be generated in the extraordinary mode just above the local cut-off frequency and to emanate nearly perpendicular to the magnetic field. It occurs within local depletions of electron density, where the ratio of plasma frequency to cyclotron frequency is less than 0.2. The density depletion is restricted to altitudes above about 2000 km, and the upper AKR frequency limit corresponds to the extraordinary cut-off frequency at this altitude. AKR is observed from Isis 1 above the nighttime auroral zone over a wider extent in longitude than in latitude with an intense source region observed most often near 2200 LMT and 70 deg invariant latitude. It is directly related to inverted V electron precipitation events with an electron-to-wave energy conversion efficiency of the order of 0.1 to 1%.

  8. Stellar Source Selections for Image Validation of Earth Observation Satellite

    NASA Astrophysics Data System (ADS)

    Yu, Jiwoong; Park, Sang-Young; Lim, Dongwook; Lee, Dong-Han; Sohn, Young-Jong

    2011-12-01

    A method of stellar source selection for validating the quality of image is investigated for a low Earth orbit optical remote sensing satellite. Image performance of the optical payload needs to be validated after its launch into orbit. The stellar sources are ideal source points that can be used to validate the quality of optical images. For the image validation, stellar sources should be the brightest as possible in the charge-coupled device dynamic range. The time delayed and integration technique, which is used to observe the ground, is also performed to observe the selected stars. The relations between the incident radiance at aperture and V magnitude of a star are established using Gunn & Stryker's star catalogue of spectrum. Applying this result, an appropriate image performance index is determined, and suitable stars and areas of the sky scene are selected for the optical payload on a remote sensing satellite to observe. The result of this research can be utilized to validate the quality of optical payload of a satellite in orbit.

  9. Center determination for trailed sources in astronomical observation images

    NASA Astrophysics Data System (ADS)

    Du, Jun Ju; Hu, Shao Ming; Chen, Xu; Guo, Di Fu

    2014-11-01

    Images with trailed sources can be obtained when observing near-Earth objects, such as small astroids, space debris, major planets and their satellites, no matter the telescopes track on sidereal speed or the speed of target. The low centering accuracy of these trailed sources is one of the most important sources of the astrometric uncertainty, but how to determine the central positions of the trailed sources accurately remains a significant challenge to image processing techniques, especially in the study of faint or fast moving objects. According to the conditions of one-meter telescope at Weihai Observatory of Shandong University, moment and point-spread-function (PSF) fitting were chosen to develop the image processing pipeline for space debris. The principles and the implementations of both two methods are introduced in this paper. And some simulated images containing trailed sources are analyzed with each technique. The results show that two methods are comparable to obtain the accurate central positions of trailed sources when the signal to noise (SNR) is high. But moment tends to fail for the objects with low SNR. Compared with moment, PSF fitting seems to be more robust and versatile. However, PSF fitting is quite time-consuming. Therefore, if there are enough bright stars in the field, or the high astronometric accuracy is not necessary, moment is competent. Otherwise, the combination of moment and PSF fitting is recommended.

  10. Ionosonde tracking of infrasound wavefronts in the thermosphere launched by seismic waves after the 2010 M8.8 Chile earthquake

    NASA Astrophysics Data System (ADS)

    Maruyama, Takashi; Yusupov, Kamil; Akchurin, Adel

    2015-04-01

    It is well known that atmospheric waves excited by intense earthquakes induce ionospheric disturbances. At remote distances greater than ~500 km, Rayleigh waves are the major source of infrasounds that propagate upward in the atmosphere. Acoustic waves interact with the ionospheric plasma through collision between neutral particles and ions. Ionospheric disturbances caused by Rayleigh waves near the low frequency part of the Airy phase (a period of several minutes) are detected as a change in the total electron content since the wavelength of induced acoustic waves in the thermosphere is comparable to the ionospheric slab thickness. On the other hand, Rayleigh waves near the high frequency part of the Airy phase (a period of several tens of seconds) cause distortion of ionogram traces characterized by a multiple cusp signature (MCS). The vertical separation of the ledge corresponding to each cusp is the wavelength of the infrasound in the thermosphere. Thus, the MCS ionogram is considered to be a snapshot of the wave that propagates upward. We conducted rapid run operation of ionosonde with a frame rate of 1 min at Kazan, Russia. After the 2010 M8.8 Chile earthquake (epicentral distance was 15,162 km), ionospheric disturbances showing MCSs on ionograms were observed for several tens of minutes. The sound speed calculated by a model was 500~700 m/s at the height of the bottomside ionosphere and wavefronts should propagate 30~42 km upward during the intervals of ionograms, which is smaller than the bottomside depth of the ionosphere. The seismogram obtained at Obninsk near Moscow, Russia (epicentral distance was 14,369 km) recorded Rayleigh waves with a period of ~17 s responsible for the ionospheric disturbances showing MCS, when the plot was shifted by the time corresponding to the difference of epicentral distances between the two locations by assuming a Rayleigh wave speed of 3 km/s. The vertical wavelength of the acoustic waves launched by the Rayleigh waves was

  11. Chandra Observations of Dying Radio Sources in Galaxy Clusters

    NASA Technical Reports Server (NTRS)

    Murgia, M.; Markevitch, M.; Govoni, F.; Parma, P.; Fanti, R.; de Ruiter, H. R.; Mack, K.-H.

    2012-01-01

    Context. The dying radio sources represent a very interesting and largely unexplored stage of the active galactic nucleus (AGN) evolution. They are considered to be very rare, and almost all of the few known ones were found in galaxy clusters. However, considering the small number detected so far, it has not been possible to draw any firm conclusions about their X-ray environment. Aims. We present X-ray observations performed with the Chandra satellite of the three galaxy clusters Abell 2276, ZwCl 1829.3+6912, and RX J1852.1+5711, which harbor at their center a dying radio source with an ultra-steep spectrum that we recently discovered. Methods. We analyzed the physical properties of the X-ray emitting gas surrounding these elusive radio sources. We determined the global X-ray properties of the clusters, derived the azimuthally averaged profiles of metal abundance, gas temperature, density, and pressure. Furthermore, we estimated the total mass profiles. Results. The large-scale X-ray emission is regular and spherical, suggesting a relaxed state for these systems. Indeed, we found that the three clusters are also characterized by significant enhancements in the metal abundance and declining temperature profiles toward the central region. For all these reasons, we classified RX J1852.1+5711, Abell 2276, and ZwCl 1829.3+6912 as cool-core galaxy clusters. Conclusions. We calculated the non-thermal pressure of the radio lobes assuming that the radio sources are in the minimum energy condition. For all dying sources we found that this is on average about one to two orders of magnitude lower than that of the external gas, as found for many other radio sources at the center of galaxy groups and clusters. We found marginal evidence for the presence of X-ray surface brightness depressions coincident with the fossil radio lobes of the dying sources in A2276 and ZwCl 1829.3+691. We estimated the outburst age and energy output for these two dying sources. The energy power from

  12. Chandra observations of dying radio sources in galaxy clusters

    NASA Astrophysics Data System (ADS)

    Murgia, M.; Markevitch, M.; Govoni, F.; Parma, P.; Fanti, R.; de Ruiter, H. R.; Mack, K.-H.

    2012-12-01

    Context. The dying radio sources represent a very interesting and largely unexplored stage of the active galactic nucleus (AGN) evolution. They are considered to be very rare, and almost all of the few known ones were found in galaxy clusters. However, considering the small number detected so far, it has not been possible to draw any firm conclusions about their X-ray environment. Aims: We present X-ray observations performed with the Chandra satellite of the three galaxy clusters Abell 2276, ZwCl 1829.3+6912, and RX J1852.1+5711, which harbor at their center a dying radio source with an ultra-steep spectrum that we recently discovered. Methods: We analyzed the physical properties of the X-ray emitting gas surrounding these elusive radio sources. We determined the global X-ray properties of the clusters, derived the azimuthally averaged profiles of metal abundance, gas temperature, density, and pressure. Furthermore, we estimated the total mass profiles. Results: The large-scale X-ray emission is regular and spherical, suggesting a relaxed state for these systems. Indeed, we found that the three clusters are also characterized by significant enhancements in the metal abundance and declining temperature profiles toward the central region. For all these reasons, we classified RX J1852.1+5711, Abell 2276, and ZwCl 1829.3+6912 as cool-core galaxy clusters. Conclusions: We calculated the non-thermal pressure of the radio lobes assuming that the radio sources are in the minimum energy condition. For all dying sources we found that this is on average about one to two orders of magnitude lower than that of the external gas, as found for many other radio sources at the center of galaxy groups and clusters. We found marginal evidence for the presence of X-ray surface brightness depressions coincident with the fossil radio lobes of the dying sources in A2276 and ZwCl 1829.3+691. We estimated the outburst age and energy output for these two dying sources. The energy power from

  13. Infrasound analysis using Fisher detector and Hough transform

    NASA Astrophysics Data System (ADS)

    Averbuch, Gil; Assink, Jelle D.; Smets, Pieter S. M.; Evers, Läslo G.

    2016-04-01

    Automatic detection of infrasound signals from the International Monitoring System (IMS) from the Comprehensive Nuclear-Test-Ban Treaty requires low rates of both false alarms and missed events. The Fisher detector is a statistical method used for detecting such infrasonic events. The detector aims to detect coherent signals after Beamforming is applied on the recordings. A detection is defined to be above a threshold value of Fisher ratio. The Fisher distribution for such a detection is affected by the SNR. While events with high Fisher ratio and SNR can easily be detected automatically, events with lower Fisher ratios and SNRs might be missed. The Hough transform is a post processing step. It is based on a slope-intercept transform applied to a discretely sampled data, with the goal of finding straight lines (in apparent velocity and back azimuth). Applying it on the results from the Fisher detector is advantageous in case of noisy data, which corresponds to low Fisher ratios and SNRs. Results of the Hough transform on synthetic data with SNR down to 0.7 provided a lower number of missed events. In this work, we will present the results of an automatic detector, based on both methods. Synthetic data with different lengths and SNRs are evaluated. Furthermore, continuous data from the IMS infrasound station I18DK will be analyzed. We will compare the performances of both methods and investigate their ability in reducing the number of missed events.

  14. Sound, infrasound, and sonic boom absorption by atmospheric clouds.

    PubMed

    Baudoin, Michaël; Coulouvrat, François; Thomas, Jean-Louis

    2011-09-01

    This study quantifies the influence of atmospheric clouds on propagation of sound and infrasound, based on an existing model [Gubaidulin and Nigmatulin, Int. J. Multiphase Flow 26, 207-228 (2000)]. Clouds are considered as a dilute and polydisperse suspension of liquid water droplets within a mixture of dry air and water vapor, both considered as perfect gases. The model is limited to low and medium altitude clouds, with a small ice content. Four physical mechanisms are taken into account: viscoinertial effects, heat transfer, water phase changes (evaporation and condensation), and vapor diffusion. Physical properties of atmospheric clouds (altitude, thickness, water content and droplet size distribution) are collected, along with values of the thermodynamical coefficients. Different types of clouds have been selected. Quantitative evaluation shows that, for low audible and infrasound frequencies, absorption within clouds is several orders of magnitude larger than classical absorption. The importance of phase changes and vapor diffusion is outlined. Finally, numerical simulations for nonlinear propagation of sonic booms indicate that, for thick clouds, attenuation can lead to a very large decay of the boom at the ground level.

  15. A study of infrasound propagation based on high-order finite difference solutions of the Navier-Stokes equations.

    PubMed

    Marsden, O; Bogey, C; Bailly, C

    2014-03-01

    The feasibility of using numerical simulation of fluid dynamics equations for the detailed description of long-range infrasound propagation in the atmosphere is investigated. The two dimensional (2D) Navier Stokes equations are solved via high fidelity spatial finite differences and Runge-Kutta time integration, coupled with a shock-capturing filter procedure allowing large amplitudes to be studied. The accuracy of acoustic prediction over long distances with this approach is first assessed in the linear regime thanks to two test cases featuring an acoustic source placed above a reflective ground in a homogeneous and weakly inhomogeneous medium, solved for a range of grid resolutions. An atmospheric model which can account for realistic features affecting acoustic propagation is then described. A 2D study of the effect of source amplitude on signals recorded at ground level at varying distances from the source is carried out. Modifications both in terms of waveforms and arrival times are described.

  16. Sources of Mass and Energy Observed in Saturn's Rings

    NASA Astrophysics Data System (ADS)

    Riofrio, L. M.

    2005-12-01

    EVIDENCE from the laboratory of Saturn's Rings solves riddles of planet formation. Observations by Cassini and other spacecraft show conditions similiar to the birth of our Solar System. These observations lead to new theories of small-body accretion. Applications have benefits for physics and energy on Earth. There have been several open questions regarding the planets. Most puzzling is the formation of mountain-sized planetesimals from protostellar dust, for these objects could not form naturally. Power source of the "dynamo" generating planetary magnetic fields was also unknown. Internal heat generated by planets and even small moons is an additional mystery. These riddles may be explained by presence of primordial singularities in the Solar System's formation. Saturn's Rings are a field of ice in which the tracks of these objects may be seen. The Cassini spacecraft has returned many fascinating images of the Rings. We now know them to be home to massive unseen objects. Satellite objects glimpsed in the Encke and Keeler gaps show behaviour unlike moons of rock or ice. Discrete trails of dirt and molecular oxygen indicate radiation discharge emanating from these objects. Similiar trails photographed in Cassini's Division indicate massive objects where no large object has been sighted visually. We must consider whether the Rings could be a home to singularities. It is generally agreed the primordial singularities were created shortly after the Big Bang, and exist in unknown numbers today. Presence of these objects in the Solar System's formation would have seeded formation of planetesimals and larger bodies. Their hidden presence would explain both planetary magnetic fields and internal heat sources. They would also explain the Ring's presence and longetivity. The most convincing evidence for singularities would be radiation discharge. Observation of a polar "hot spot" on Enceladus can not be explained by old theories of radioactive decay. The only feasible source

  17. H2CO Observations Towards CH3OH Maser Sources

    NASA Astrophysics Data System (ADS)

    Okoh, Daniel; Esimbek, Jarken; Zhou, JianJun; Tang, Xindi; Chukwude, Augustine; Urama, Johnson; Okeke, Pius

    2013-03-01

    Formaldehyde (H2CO) is an accurate probe of physical conditions in dense and low-temperature molecular clouds towards massive star formation regions, while 6.7 GHz methanol (CH3OH) masers provide ideal sites to probe the earliest stages of massive stellar formation. We present preliminary results of our investigation into the possible relationship between formaldehyde and methanol astrophysical masers with the view to expanding knowledge on massive star formation processes. Observations are done using the Nanshan 25m radio telescope of the Xinjiang Astronomical Observatories, Urumqi, China. 127 Methanol sources (from the work of Green et al. 2010, Xu et al. 2003, Pestalozzi et al. 2005, and Xu et al. 2009) have been observed so far for 4.8 GHz formaldehyde absorption lines, and H2CO signals have been detected in 86 of them, 31 of which are newly discovered. We obtained good correlation (0.85 correlation coefficient) between the velocities of the sources, and a poor correlation (-0.03 correlation coefficient) between their intensities, an indication that signals from the two lines originate from about the same region, but that the excitation mechanisms that drive them are likely different.

  18. Assessment of Operational Progress of NASA Langley Developed Windshield and Microphone for Infrasound

    DTIC Science & Technology

    2013-04-01

    Assessment of Operational Progress of NASA Langley Developed Windshield and Microphone for Infrasound by W.C. Kirkpatrick Alberts, II... Windshield and Microphone for Infrasound W.C. Kirkpatrick Alberts, II, Stephen M. Tenney, and John M. Noble Sensors and Electron Devices Directorate...NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. 1. REPORT DATE (DD-MM-YYYY) April 2013 2. REPORT TYPE Final 3. DATES COVERED (From - To) Nov 2011–Jan

  19. Studies of Accreting Neutron Stars with RXTE Cycle 4 Observations: III: TOO Observations of Atoll Sources

    NASA Technical Reports Server (NTRS)

    Paciesas, William S.

    2002-01-01

    NASA Grant NAG 5-9244 provided funds for the research projects 'ASM-Triggered TOO Observations of Kilohertz Oscillations in Five Atoll Sources' and 'Further Measurements of the Kilohertz Oscillations in 4U 1705-44' approved under the Rossi X-ray Timing Explorer (RXTE) Guest Observer Program Cycle 4 and funded under the 1999 NASA Astrophysics Data Program. The principal investigator of the observing time proposals was Dr. E. C. Ford (U. of Amsterdam). The grant was funded for one year beginning 3/15/2000. The original ADP proposal was submitted by Prof. Jan van Paradijs, who passed away in 1999 before the funds were distributed. Prof. Wilham S. Padesas administered the grant during the period of performance. In spite of a wealth of observational data on the kHz QPO in low-mass X-ray binaries (LMXBs), the interpretation of this phenomenon is currently uncertain because the pairs of kHz QPO peaks and the oscillations seen in some Type I X-ray bursts are almost, but not quite, connected by a simple beat frequency relation. Further systematic studies of systems with known QPOs are required in order to better understand the phenomenon. The proposals were intended to contribute to a solution to this confusion by observing the sources as they vary over a wide range of X-ray flux. RXTE target-of-opportunity observations of six transient atoll sources, 4U 0614+09, KS 1732-260, Ser X-1, 4U 1702-42, 4U 1820-30 and 4U 1705-44 were to be performed at various flux levels based on ASM measurements.

  20. Long-Period Seismicity and Very-Long-Period Infrasound Driven by Shallow Magmatic Degassing at Mount Pagan, Mariana Islands

    NASA Astrophysics Data System (ADS)

    Lyons, J. J.; Haney, M. M.; Werner, C. A.; Kelly, P. J.; Patrick, M. R.; Kern, C.; Trusdell, F.

    2015-12-01

    Mount Pagan is the currently active vent on the north end of Pagan Volcano, Mariana Islands. A persistent degassing plume, LP seismicity, and VLP infrasound (iVLP) have dominated activity since at least 2013, when ground-based geophysical sensors were first installed. Direct gas sampling with a Multi-GAS sensor indicates a plume generated by a shallow magmatic system. Here we present an analysis of coupled LP and iVLP events in order to reveal the details of their source processes and how the signals are related to shallow magmatic degassing. The LP and iVLP waveform characteristics were highly stable from July 2013 - January 2014. Both events have durations of 5-20 s, occur every 1-2 minutes, and have emergent onsets. The LP events have a dominant frequency of 0.54 Hz, while the dominant frequency of the iVLP is 0.32 Hz. The delay times between the LP and iVLP arrivals show little variation during the 7-month study, indicating a stable, shallow, and nearly co-located source. Full waveform inversion of a master LP event reveals a volumetric source 60 m below and 180 m west of the summit vent. Inverting Green's functions of different geometric combinations results in a 2-crack model dominated by a subhorizontal crack intersecting a NW-SE trending dike. The extension of the modeled crack intersects the surface near the vent location. The nearly horizontal orientation of the dominant crack is likely controlled by the orientation of lava flows and pyroclastic deposits that are observed in the western wall of the cone at the LP depth. We propose that the LP seismicity is crack resonance triggered by collapse of the gas-charged upper conduit system following periodic venting. Measured and modeled pressure-velocity (P/Vz) ratios for the seismoacoustic events indicate that elastodynamic processes associated with the seismic LP cannot generate the iVLP. Thus, we model the iVLP as volume resonance of an exponential horn, based on the shape of the crater and the wavelength of

  1. Mapping thunder sources by inverting acoustic and electromagnetic observations

    NASA Astrophysics Data System (ADS)

    Anderson, J. F.; Johnson, J. B.; Arechiga, R. O.; Thomas, R. J.

    2014-12-01

    We present a new method of locating current flow in lightning strikes by inversion of thunder recordings constrained by Lightning Mapping Array observations. First, radio frequency (RF) pulses are connected to reconstruct conductive channels created by leaders. Then, acoustic signals that would be produced by current flow through each channel are forward modeled. The recorded thunder is considered to consist of a weighted superposition of these acoustic signals. We calculate the posterior distribution of acoustic source energy for each channel with a Markov Chain Monte Carlo inversion that fits power envelopes of modeled and recorded thunder; these results show which parts of the flash carry current and produce thunder. We examine the effects of RF pulse location imprecision and atmospheric winds on quality of results and apply this method to several lightning flashes over the Magdalena Mountains in New Mexico, USA. This method will enable more detailed study of lightning phenomena by allowing researchers to map current flow in addition to leader propagation.

  2. Tropical cyclone waves detected with infrasound sensor array

    NASA Astrophysics Data System (ADS)

    Schultz, Colin

    2013-02-01

    The strong winds of a tropical cyclone whip up the sea surface, driving ocean waves a dozen meters high. When one such ocean wave runs into another wave that has an equal period but is traveling in the opposite direction, the interaction produces low-frequency sound waves that can be detected thousands of kilometers away. The infrasound signals produced by interacting ocean surface waves—known as microbarom—have typical frequencies around 0.2 hertz. Researchers previously determined that as a hurricane travels along its track, early waves generated by the storm will interact with those generated later on, producing a strong microbarom signal in the storm's wake. Researchers also found, however, that microbarom signals are produced by regular surface ocean behavior, including swell, surface waves, and nontropical cyclone storms.

  3. Source properties of microearthquakes revealed by near-source observation at SAFOD (Invited)

    NASA Astrophysics Data System (ADS)

    Imanishi, K.; Ellsworth, W. L.

    2010-12-01

    Near-source observation of earthquakes in deep boreholes and mines provides significant opportunities to enhance our understanding of the source properties of earthquakes. Short hypocentral distances and a high-Q environment make it possible to observe earthquake processes that cannot be seen in shallow boreholes or at the surface. The SAFOD Main Hole is a 3.2 km-deep inclined borehole that crosses the active traces of the San Andreas Fault. A 3-component 15 Hz GS-20DM geophone was deployed within the fault zone at depths between 2350 and 2750 m. Because of the close proximity to earthquake sources, we routinely observed earthquakes with Mw < 0 with high signal-to-noise ratio. Events were recorded at three different sampling rates (1000, 2000, and 4000 sps) depending on observation period (2005 - 2010). This study focuses on earthquakes with S-P time differences shorter than 0.5s, corresponding to hypocentral distance less than 3 km. Among more than 400 earthquakes, we selected 117 events classified into 35 clusters on the basis of waveform similarity at low frequencies. Selected events range in size from approximately Mw -3 to Mw 2. The dataset includes many events in three clusters that formed the SAFOD drilling target; San Francisco, Los Angeles and Hawaii named as their relative positions with respect to those cities. We determined source parameters by the Multi-Window Spectral Ratio (MWSR) method (Imanishi and Ellsworth, 2006). The key step in the method is to stack the ratios calculated from moving windows taken along the record starting with the direct waves. We confirmed that stacking better suppresses the random noise due to differences in path than single-window methods, producing a better estimate of the source spectral ratio. For Mw>-1, the calculated stress drops range between 0.1 and 100 MPa. These observations indicate that there is no breakdown in stress drop scaling for Mw>-1. The stacked spectral ratios show that corner frequencies of events for

  4. A study of volcanic eruption characteristics using infrasound data recorded on the global IMS network

    NASA Astrophysics Data System (ADS)

    Dabrowa, Amy; Green, David; Phillips, Jeremy; Rust, Alison

    2010-05-01

    Explosive volcanic eruptions have the capability to generate sound waves with infrasonic frequencies (<20Hz). As such waves can propagate over distances of thousands of kilometres within the atmosphere, they present an opportunity to remotely monitor volcanic eruptions and potentially constrain eruptive characteristics. Though most volcanoes in sensitive areas of the world are monitored individually, many volcanoes in remote locations are not monitored directly but can still pose a threat, especially to aviation. The growing International Monitoring System (IMS) network of infrasound stations provides an opportunity to monitor these remote volcanoes. Currently comprising of 43 arrays, the network is designed to achieve global coverage for surface explosions equivalent to a few hundred tonnes of chemical explosive. In recent years work has been published on the detection of specific volcanic eruptions at IMS stations, primarily at regional ranges (< 1000 km from volcano to receiver). In contrast, work presented here looks to create a catalogue of volcanic eruptions that have been detected at IMS stations, with the aim of assessing the capability of the IMS network for use in global volcano monitoring. At this time 40 eruptive events at 19 volcanoes have been investigated from the period 2004 - 2009; however the work is on-going and it is planned to extend this catalogue. In total we document 61 individual detections that have been made on the IMS network. These range from Strombolian activity at Mount Erebus (Antarctica) recorded at a range of 25 km distance, to the Plinian eruption of Manam Volcano (Papua New Guinea) recorded at ranges of over 10,000 km distance. The observed signal frequencies for different eruptions range from less than 0.01 Hz to greater than 5 Hz, and in general, lower frequencies are generated by the larger eruptions. We provide examples of analyses for eruptions recorded at multiple stations (e.g., Manam, October 2004; Kasatochi, August 2008

  5. Chandra Observations of Point Sources in Abell 2255

    NASA Technical Reports Server (NTRS)

    Davis, David S.; Miller, Neal A.; Mushotzky, Richard F.

    2003-01-01

    In our search for "hidden" AGN we present results from a Chandra observation of the nearby cluster Abell 2255. Eight cluster galaxies are associated with point-like X-ray emission, and we classify these galaxies based on their X-ray, radio, and optical properties. At least three are associated with active galactic nuclei (AGN) with no optical signatures of nuclear activity, with a further two being potential AGN. Of the potential AGN, one corresponds to a galaxy with a post-starburst optical spectrum. The remaining three X-ray detected cluster galaxies consist of two starbursts and an elliptical with luminous hot gas. Of the eight cluster galaxies five are associated with luminous (massive) galaxies and the remaining three lie in much lower luminosity systems. We note that the use of X-ray to optical flux ratios for classification of X-ray sources is often misleading, and strengthen the claim that the fraction of cluster galaxies hosting an AGN based on optical data is significantly lower than the fraction based on X-ray and radio data.

  6. The 2013 Chelyabinsk meteorite: global detection performance of the CTBTO infrasound network

    NASA Astrophysics Data System (ADS)

    Pilger, Christoph; Ceranna, Lars; Le Pichon, Alexis; Mialle, Pierrick; Garces, Milton

    2014-05-01

    The explosive fragmentation of the Chelyabinsk meteorite of 15 February 2013 over the Ural Mountains, Russia, generated a large airburst with an equivalent explosive yield of half a megaton of TNT. It is the most energetic event recorded by the infrasound component of the International Monitoring System (IMS) network operated by the Comprehensive Nuclear-Test-Ban Treaty Organization. The event was detected by 20 out of 45 stations of the operational IMS network and propagation paths from the event to the stations ranged between 500 km and 87000 km, traveling more than twice around the globe. The current study in the framework of the ARISE project (http://arise-project.eu/) performs a detailed station-by-station estimation to address why infrasonic signals were clearly detected at some of the stations over very large distances whereas they were not detected at other stations at shorter distances. One potential explanation investigated within this study is the directivity of the signal energy radiated from the meteorite's line source, where azimuth directions at stations perpendicular to the trajectory are favored compared to parallel directions. Another explanation might be different noise and data quality levels at each station, which not only depend on frequency and sensor response, but also on diurnal, seasonal and weather variability. The presentation will provide a station-dependent overview on these parameters compared to the detections of the meteorite event.

  7. Infrasound and seismic signals from Baikonur spaceport rocket launches recorded by Kazakh stations

    NASA Astrophysics Data System (ADS)

    Smirnov, Alexandr; Sokolova, Inna; Mikhailova, Natalya

    2015-04-01

    The monitoring network of the Institute of Geophysical Researches, Kazakhstan consists of 2 infrasound arrays, 8 seismic arrays and 7 3C stations. 5 of these stations are a part of IMS CTBTO. The Institute of Geophysical Researches monitors round-the-clock many sorts of seismoacoustic events. Tens of rockets are launched every year from Baikonur spaceport located in Central Kazakhstan. Baikonur rockets fly over several regions of Kazakhstan. Kazakh monitoring stations record launches, rocket stage falls, satellite recovery and sometimes accidents. A catalog of events associated with such activity is built. Some waveform features are collected. The catalog also contains some kinematic and dynamic parameters of the events sources. The signals from accidents of Dnepr rocket of July 26, 2006 and Proton rocket of September 5, 2007 and of July 2, 2013 were studied in details. Discrimination of the events associated with spaceport activity and its exclusion from seismic bulletins allows improving the bulletins quality. And in case of accident this information helps to estimate the event parameters and to start recovery procedures in proper time.

  8. Scaling Relationship Among Source Parameters of Microearthquake," From Near Source Observation in a Deep Mine

    NASA Astrophysics Data System (ADS)

    Hiramatsu, Y.; Yoshimura, M.; Furumoto, M.

    2004-12-01

    Scaling relationships among various source parameters are important clues to understand the source process. In particular the relationship between the corner frequency, fC, and the seismic moment, MO, has been investigated by many researchers. Aki(1967) investigated fC and MO using the spectra of seismic waves and reported that these parameters obeyed a relationship of MO ∝ fC-3. For small earthquakes, the breakdown of this relationship was often reported. On the other hand, no breakdown of the relationship for microearthquakes has been reported from high quality observation at deep boreholes and in a deep gold mine. We report here these scaling relationships using waveform of microearthquakes observed at the distance range of 15m to 1km. We installed nine tri-axial borehole accelerometers within 200 m along a haulage tunnel 2650m deep in Mponeng mine in South Africa from February to December in 1996. More than 25 thousand seismic events were recorded with a sampling frequency of 15 kHz and a dynamic range of 120 dB. The recording system has flat response up to 2 KHz. Among those events, we select 378 events with high S/N. We locate hypocenters assuming infinite medium with the P-wave velocity 5.5 km/s and the S-wave velocity 3.2 km/s. We calculate the green function using the discrete wavenumber integral method into account the effect of anelasticity by Takeo (1985) and determine the seismic moment and the mechanism using moment tensor inversion. We apply the omega square model by Brune (1970) to determine the corner frequency and the stress drop. Minimizing L2 norm between the observed spectra of P and S waves and the synthetic ones give the optimum source parameters. The earthquakes analyzed in this study show the constant stress drop of 0.4 ˜8MPa in the ranges of 40

  9. Infrasound from lightning measured in Ivory Coast from 2004 to 2014

    NASA Astrophysics Data System (ADS)

    Farges, Thomas; Le Pichon, Alexis; Ceranna, Lars; Diawara, Adama

    2016-04-01

    It is well established that more than 2,000 thunderstorms occur continuously around the world and that about 45 lightning flashes are produced per second over the globe. 80 % of the infrasound stations of the International Monitoring System (IMS) of the CTBTO (Comprehensive nuclear Test Ban Treaty Organisation) are now certified and routinely measure signals due to natural activity (e.g., airflow over mountains, aurora, microbaroms, surf, volcanoes, severe weather including lightning flashes …). Some of the IMS stations are located where lightning activity is high (e.g. Africa, South America). These infrasound stations are well localised to study lightning flash activity and its disparity, which is a good proxy for global warming. Progress in infrasound array data processing over the past ten years makes such lightning studies possible. Assink et al. (2008) and Farges and Blanc (2010) show clearly that it is possible to measure lightning infrasound from thunderstorms within 300 km. One-to-one correlation is possible when the thunderstorm is within about 75 km from the station. When the lightning flash occurs within 20 km, it is also possible to rebuild the 3D geometry of the discharges when the network size is less than 100 m (Arechiga et al., 2011; Gallin, 2014). An IMS infrasound station has been installed in Ivory Coast since 2002. The lightning rate of this region is 10-20 flashes/km²/year from space-based instrument OTD (Christian et al., 2003). Ivory Coast is therefore a good place to study infrasound data associated with lightning activity and its temporal variation. First statistical results will be presented in this paper based on 10 years of data (2005-2014). Correlation between infrasound having a mean frequency higher than 1 Hz and lightning flashes detected by the World Wide Lightning Location Network (WWLLN) is systematically looked for. One-to-one correlation is obtained for flashes occurring within about 100 km. An exponential decrease of the

  10. 75 FR 37742 - Addition of New Export Control Classification Number 6A981 Passive Infrasound Sensors to the...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-30

    ... Classification Number 6A981 Passive Infrasound Sensors to the Commerce Control List of the Export Administration... Control List (CCL) to control passive infrasound sensors because of their military and commercial utility... CONTACT: James Thompson, Sensors and Aviation Division, Bureau of Industry and Security, Telephone:...

  11. Merging Infrasound and Electromagnetic Signals as a Means for Nuclear Explosion Detection

    NASA Astrophysics Data System (ADS)

    Ashkenazy, Joseph; Lipshtat, Azi; Kesar, Amit S.; Pistinner, Shlomo; Ben Horin, Yochai

    2016-04-01

    The infrasound monitoring network of the CTBT consists of 60 stations. These stations are capable of detecting atmospheric events, and may provide approximate location within time scale of a few hours. However, the nature of these events cannot be deduced from the infrasound signal. More than two decades ago it was proposed to use the electromagnetic pulse (EMP) as a means of discriminating nuclear explosion from other atmospheric events. An EMP is a unique signature of nuclear explosion and is not detected from chemical ones. Nevertheless, it was decided to exclude the EMP technology from the official CTBT verification regime, mainly because of the risk of high false alarm rate, due to lightning electromagnetic pulses [1]. Here we present a method of integrating the information retrieved from the infrasound system with the EMP signal which enables us to discriminate between lightning discharges and nuclear explosions. Furthermore, we show how spectral and other characteristics of the electromagnetic signal emitted from a nuclear explosion are distinguished from those of lightning discharge. We estimate the false alarm probability of detecting a lightning discharge from a given area of the infrasound event, and identifying it as a signature of a nuclear explosion. We show that this probability is very low and conclude that the combination of infrasound monitoring and EMP spectral analysis may produce a reliable method for identifying nuclear explosions. [1] R. Johnson, Unfinished Business: The Negotiation of the CTBT and the End of Nuclear Testing, United Nations Institute for Disarmament Research, 2009.

  12. The influence of periodic wind turbine noise on infrasound array measurements

    NASA Astrophysics Data System (ADS)

    Pilger, Christoph; Ceranna, Lars

    2017-02-01

    Aerodynamic noise emissions from the continuously growing number of wind turbines in Germany are creating increasing problems for infrasound recording systems. These systems are equipped with highly sensitive micro pressure sensors accurately measuring acoustic signals in a frequency range inaudible to the human ear. Ten years of data (2006-2015) from the infrasound array IGADE in Northern Germany are analysed to quantify the influence of wind turbine noise on infrasound recordings. Furthermore, a theoretical model is derived and validated by a field experiment with mobile micro-barometer stations. Fieldwork was carried out 2004 to measure the infrasonic pressure level of a single horizontal-axis wind turbine and to extrapolate the sound effect for a larger number of nearby wind turbines. The model estimates the generated sound pressure level of wind turbines and thus enables for specifying the minimum allowable distance between wind turbines and infrasound stations for undisturbed recording. This aspect is particularly important to guarantee the monitoring performance of the German infrasound stations I26DE in the Bavarian Forest and I27DE in Antarctica. These stations are part of the International Monitoring System (IMS) verifying compliance with the Comprehensive Nuclear-Test-Ban Treaty (CTBT), and thus have to meet stringent specifications with respect to infrasonic background noise.

  13. Neutron stars as sources of gamma-ray bursts: Constraints from X-ray observations of source locations

    NASA Technical Reports Server (NTRS)

    Pizzichini, G.; Cline, T. L.; Desai, U.; Teegarden, B. J.; Hurley, K.; Niel, M.; Vedrenne, G.; Evans, W. D.; Fenimore, E. E.; Klebesadel, R. W.

    1982-01-01

    Results for three burst locations observed with the imaging proportional counter of the Einstein Observatory are given. The observations are used to determine temperature and accretion constraints for the burst source.

  14. The 2013 Russian fireball largest ever detected by CTBTO infrasound sensors

    NASA Astrophysics Data System (ADS)

    Le Pichon, Alexis; Ceranna, Lars; Pilger, Christoph; Mialle, Pierrick; Brown, David; Herry, Pascal; Brachet, Nicolas

    2013-07-01

    15 February 2013, a large Earth-impacting fireball disintegrated over the Ural Mountains. This extraordinary event is, together with the 1908 Tunguska fireball, among the most energetic events ever instrumentally recorded. It generated infrasound returns, after circling the globe, at distances up to ~85,000 km, and was detected at 20 infrasonic stations of the global International Monitoring System (IMS). For the first time since the establishment of the IMS infrasound network, multiple arrivals involving waves that traveled twice round the globe have been clearly identified. A preliminary estimate of the explosive energy using empirical period-yield scaling relations gives a value of 460 kt of TNT equivalent. In the context of the future verification of the Comprehensive Nuclear-Test-Ban Treaty, this event provides a prominent milestone for studying in detail infrasound propagation around the globe for almost 3 days as well as for calibrating the performance of the IMS network.

  15. Design of infrasound-detection system via adaptive LMSTDE algorithm

    NASA Technical Reports Server (NTRS)

    Khalaf, C. S.; Stoughton, J. W.

    1984-01-01

    A proposed solution to an aviation safety problem is based on passive detection of turbulent weather phenomena through their infrasonic emission. This thesis describes a system design that is adequate for detection and bearing evaluation of infrasounds. An array of four sensors, with the appropriate hardware, is used for the detection part. Bearing evaluation is based on estimates of time delays between sensor outputs. The generalized cross correlation (GCC), as the conventional time-delay estimation (TDE) method, is first reviewed. An adaptive TDE approach, using the least mean square (LMS) algorithm, is then discussed. A comparison between the two techniques is made and the advantages of the adaptive approach are listed. The behavior of the GCC, as a Roth processor, is examined for the anticipated signals. It is shown that the Roth processor has the desired effect of sharpening the peak of the correlation function. It is also shown that the LMSTDE technique is an equivalent implementation of the Roth processor in the time domain. A LMSTDE lead-lag model, with a variable stability coefficient and a convergence criterion, is designed.

  16. Multiwavelength observations of unidentified high energy gamma ray sources

    NASA Technical Reports Server (NTRS)

    Halpern, Jules P.

    1993-01-01

    As was the case for COS B, the majority of high-energy (greater than 100 MeV) gamma-ray sources detected by the EGRET instrument on GRO are not immediately identifiable with cataloged objects at other wavelengths. These persistent gamma-ray sources are, next to the gamma-ray bursts, the least understood objects in the universe. Even a rudimentary understanding of their nature awaits identifications and follow-up work at other wavelengths to tell us what they are. The as yet unidentified sources are potentially the most interesting, since they may represent unrecognized new classes of astronomical objects, such as radio-quiet pulsars or new types of active galactic nuclei (AGN's). This two-year investigation is intended to support the analysis, correlation, and theoretical interpretation of data that we are obtaining at x ray, optical, and radio wavelengths in order to render the gamma-ray data interpretable. According to plan, in the first year concentration was on the identification and study of Geminga. The second year will be devoted to studies of similar unidentified gamma-ray sources which will become available in the first EGRET catalogs. The results obtained so far are presented in the two papers which are reproduced in the Appendix. In these papers, we discuss the pulse profiles of Geminga, the geometry and efficiency of the magnetospheric accelerator, the distance to Geminga, the implications for theories of polar cap heating, the effect of the magnetic field on the surface emission and environment of the neutron star, and possible interpretations of a radio-quiet Geminga. The implications of the other gamma-ray pulsars which were discovered to have high gamma-ray efficiency are also discussed, and the remaining unidentified COS B sources are attributed to a population of efficient gamma-ray sources, some of which may be radio quiet.

  17. Implementation and evaluation of an inexpensive low-power low-noise infrasound sensor and its use in a dense sensor network around an active volcanic vent

    NASA Astrophysics Data System (ADS)

    Marcillo, O. E.; Johnson, J. B.; Hart, D. M.

    2011-12-01

    The development and evaluation of a low-cost infrasound sensor, the infraNMT, and its use as part of a dense (45-element) sensor network around an active volcanic vent, are described. This sensor is based on a commercial micro-machined piezo-resistive differential pressure transducer that uses a mechanical high-pass filter to reject low-frequency out-band energy. The sensor features low noise, 2.02 mPa rms (0.5-2 Hz), 5.47 mPa RMS (0.1-20 Hz), or 5.62 mPa rms (0.05-20 Hz), flat response between 0.01 Hz to at least 40 Hz, inband sensitivity of 45.13 +/-0.23 μV/Pa, and nominal linear range of -124.5 to +124.5 Pa. The sensor consumes a minimum of 24 mW, and operates with voltages above 8V while drawing 3mA of current. The infraNMT specifications described above were independently verified using the infrasound test chamber at the Sandia National Laboratories' Facility for Acceptance, Calibration, and Testing (SNL-FACT) and following procedures for comparison calibration against traceable reference stands in voltage and pressure. Due to the intended broad frequency response of this sensor the testing chamber was configured in a double reference sensor scheme. A well-characterized MB2000 micro-barometer (with a flat amplitude response between 0.01 and 8 Hz) and microphone (with a flat amplitude response above 8Hz) were used simultaneously in this double reference test configuration. The characteristics of the infraNMT, including small size, low power consumption, high dynamic range, and low cost, favor its use in array or network configurations for near source and/or higher noise environments. This sensor has been used for infrasound array studies associated with various sources, including volcanic and chemical explosions, glacier earthquakes, and thunder. In this study we report on the Summer 2010 deployment of a network of 45 infraNMT sensors at Kilauea volcano to study the infrasound generated by degassing of the active Halema'uma'u vent. For this experiment, the

  18. Acoustic source characterization of impulsive Strombolian eruptions from the Mount Erebus lava lake

    NASA Astrophysics Data System (ADS)

    Johnson, Jeffrey; Aster, Richard; Jones, Kyle R.; Kyle, Philip; McIntosh, Bill

    2008-11-01

    We invert for acoustic source volume outflux and momentum imparted to the atmosphere using an infrasonic network distributed about the erupting lava lake at Mount Erebus, Ross Island, Antarctica. By modeling these relatively simple eruptions as monopole point sources we estimate explosively ejected gas volumes that range from 1,000 m 3 to 24,000 m 3 for 312 lava lake eruptions recorded between January 6 and April 13, 2006. Though these volumes are compatible with bubble volumes at rupture (as estimated from explosion video records), departures from isotropic radiation are evident in the recorded acoustic wavefield for many eruptions. A point-source acoustic dipole component with arbitrary axis orientation and strength provides precise fit to the recorded infrasound. This dipole source axis, corresponding to the axis of inferred short-duration material jetting, varies significantly between events. Physical interpretation of dipole orientation as being indicative of eruptive directivity is corroborated by directional emissions of ejecta observed in Erebus eruption video footage. Although three azimuthally distributed stations are insufficient to fully characterize the eruptive acoustic source we speculate that a monopole with a minor amount of oriented dipole radiation may reasonably model the primary features of the recorded infrasound for these eruptions.

  19. The Ionosphere's Pocket Litter: Exploiting Crowd-Sourced Observations

    NASA Astrophysics Data System (ADS)

    Miller, E. S.; Frissell, N. A.; Kaeppler, S. R.; Demajistre, R.; Knuth, A. A.

    2015-12-01

    One of the biggest challenges faced in developing and testing our understanding of the ionosphere is acquiring data that characterizes the latitudinal and longitudinal variability of the ionosphere. While there are extensive networks of ground sites that sample the vertical distribution, we have rather poor coverage over the oceans and in parts of the southern hemisphere. Our ability to validate the ionospheric models is limited by the lack of point measurements and those measurements that essentially constitute characterization of horizontal gradients. In this talk, we discuss and demonstrate the use of various types of crowd-sourced information that enables us to extend our coverage over these regions. We will discuss new sources of these data, concepts for new experiments and the use of these data in assimilative models. We note that there are new, low cost options for obtaining data that broaden the participation beyond the aeronomy/ionospheric community.

  20. Tropical sources and sinks of carbonyl sulfide observed from space

    NASA Astrophysics Data System (ADS)

    Glatthor, Norbert; Höpfner, Michael; Baker, Ian T.; Berry, Joe; Campbell, Elliott; Kawa, Stephan R.; Krysztofiak, Gisele; Sinnhuber, Björn-Martin; Stiller, Gabriele; Stinecipher, Jim; von Clarmann, Thomas

    2016-04-01

    According to current budget estimations the seasonal variation of carbonyl sulfide (COS) is governed by oceanic release and vegetation uptake. Its assimilation by plants is assumed to be similar to the photosynthetic uptake of CO2 but, contrary to the latter process, to be irreversible. Therefore COS has been suggested as co-tracer of the carbon cycle. Observations of COS, however, are sparse, especially in tropical regions. We use the comprehensive data set of spaceborne measurements of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) to analyze its global distribution. Two major features are observed in the tropical upper troposphere around 250 hPa: enhanced amounts over the western Pacific and the Maritime Continent, peaking around 550 pptv in boreal summer, and a seasonally varying depletion of COS extending from tropical South America to Africa. The large-scale COS depletion, which in austral summer amounts up to -40 pptv as compared to the rest of the respective latitude band, has not been observed before and reveals the seasonality of COS uptake through tropical vegetation. The observations can only be reproduced by global models, when a large vegetation uptake and a corresponding increase in oceanic emissions as proposed in several recent publications is assumed.

  1. Observations of collective effects at the Advanced Light Source

    SciTech Connect

    Byrd, J.M.; Barry, W.; Corlett, J.N.; Fox, J.; Teytelman, D.

    1995-10-01

    We present a summary of measurements of single beam collective effects in the Advanced Light Source (ALS). We describe measurements of coupled-bunch instabilities, including some recent results using the newly commissioned feedback systems and the results of an initial search for the fast ion instability. Single bunch effects include bunch lengthening, energy spread increase, HOM loss measurements, head-tail damping rates, current dependent tune shifts, and transverse mode coupling instability threshold. The longitudinal measurements are consistent with a broadband impedance {vert_bar}{Zeta}{sub {parallel}}/{eta}{vert_bar}{sub eff} = 0.22{plus_minus}0.07 {Omega} and transverse measurements indicate broadband impedances of {Zeta}{sub y,eff} = 155 k{Omega}/m and Z{sub x,eff} = 58 k{Omega}/m.

  2. Seasonal variations of infrasonic arrivals from long term ground truth observations in Nevada and implication for event location

    NASA Astrophysics Data System (ADS)

    Negraru, Petru; Golden, Paul

    2017-01-01

    SUMMARYLong term ground truth <span class="hlt">observations</span> were collected at two <span class="hlt">infrasound</span> arrays in Nevada to investigate how seasonal atmospheric variations affect the detection, travel time and signal characteristics (azimuth, trace velocity, frequency content and amplitudes) of infrasonic arrivals at regional distances. The arrays were located in different azimuthal directions from a munition disposal facility in Nevada. FNIAR, located 154 km north of the <span class="hlt">source</span> has a high detection rate throughout the year. Over 90% of the detonations have travel times indicative of stratospheric arrivals, while tropospheric waveguides are <span class="hlt">observed</span> from only 27% of the detonations. The second array, DNIAR, located 293 km southeast of the <span class="hlt">source</span> exhibits strong seasonal variations with high stratospheric detection rates in winter and the virtual absence of stratospheric arrivals in summer. Tropospheric waveguides and thermospheric arrivals are also <span class="hlt">observed</span> for DNIAR. Modelling through the Naval Research Laboratory Ground to Space (G2S) atmospheric sound speeds leads to mixed results: FNIAR arrivals are usually not predicted to be present at all (either stratospheric or tropospheric), while DNIAR arrivals are usually correctly predicted, but summer arrivals show a consistent travel time bias. In the end we show the possible improvement in location using empirically calibrated travel time and azimuth <span class="hlt">observations</span>. Using the Bayesian <span class="hlt">Infrasound</span> <span class="hlt">Source</span> Localization we show that we can decrease the area enclosed by the 90% credibility contours by a factor of 2.5.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/18194788','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/18194788"><span>Testing nonlocal <span class="hlt">observation</span> as a <span class="hlt">source</span> of intuitive knowledge.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Radin, Dean</p> <p>2008-01-01</p> <p>This study explored the hypothesis that in some cases intuitive knowledge arises from perceptions that are not mediated through the ordinary senses. The possibility of detecting such nonlocal <span class="hlt">observation</span> was investigated in a pilot test based on the effects of <span class="hlt">observation</span> on a quantum system. Participants were asked to imagine that they could intuitively perceive a low-intensity laser beam in a distant Michelson interferometer. If such <span class="hlt">observation</span> were possible, it would theoretically perturb the photons' quantum wave functions and change the pattern of light produced by the interferometer. The optical apparatus was located inside a light-tight, double-steel walled, shielded chamber. Participants sat quietly outside the chamber with eyes closed. The light patterns were recorded by a cooled digital camera once per second, and average illumination levels of these images were compared in counterbalanced mental blocking versus nonblocking conditions. By design, perturbation would produce a lower overall level of illumination, which was predicted to occur during the blocking condition. Based on a series of planned experimental sessions, the outcome was in accordance with the prediction (z = -2.82; P = .002). This result was primarily due to nine sessions involving experienced meditators (combined z = -4.28; P = 9.4 x 10(-6)); the other nine sessions with nonmeditators were not significant (combined z = 0.29; P = .61). The same experimental protocol run immediately after 15 of these test sessions, but with no one present, revealed no hardware or protocol artifacts that might have accounted for these results (combined control z = 1.50; P = .93). Conventional explanations for these results were considered and judged to be implausible. This pilot study suggests the presence of a nonlocal perturbation effect that is consistent with traditional concepts of intuition as a direct means of gaining knowledge about the world, and with the predicted effects of <span class="hlt">observation</span> on a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012NatGe...5..499F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012NatGe...5..499F"><span>Riverine <span class="hlt">source</span> of Arctic Ocean mercury inferred from atmospheric <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fisher, Jenny A.; Jacob, Daniel J.; Soerensen, Anne L.; Amos, Helen M.; Steffen, Alexandra; Sunderland, Elsie M.</p> <p>2012-07-01</p> <p>Methylmercury is a potent neurotoxin that accumulates in aquatic food webs. Human activities, including industry and mining, have increased inorganic mercury inputs to terrestrial and aquatic ecosystems. Methylation of this mercury generates methylmercury, and is thus a public health concern. Marine methylmercury is a particular concern in the Arctic, where indigenous peoples rely heavily on marine-based diets. In the summer, atmospheric inorganic mercury concentrations peak in the Arctic, whereas they reach a minimum in the northern mid-latitudes. Here, we use a global three-dimensional ocean-atmosphere model to examine the cause of this Arctic summertime maximum. According to our simulations, circumpolar rivers deliver large quantities of mercury to the Arctic Ocean during summer; the subsequent evasion of this riverine mercury to the atmosphere can explain the summertime peak in atmospheric mercury levels. We infer that rivers are the dominant <span class="hlt">source</span> of mercury to the Arctic Ocean on an annual basis. Our simulations suggest that Arctic Ocean mercury concentrations could be highly sensitive to climate-induced changes in river flow, and to increases in the mobility of mercury in soils, for example as a result of permafrost thaw and forest fires.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PhRvD..91l3004E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PhRvD..91l3004E"><span>Possibility of <span class="hlt">observable</span> signatures of leptonium from astrophysical <span class="hlt">sources</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ellis, S. C.; Bland-Hawthorn, Joss</p> <p>2015-06-01</p> <p>The formation of positronium in our Galaxy is well measured, and has led to important and unanswered questions on the origin of the positrons. In principle it should be possible to form analogous systems from μ and τ leptons, viz. true muonium and true tauonium. However the probability of formation for these systems is greatly reduced due to the intrinsically short lifetimes of the μ and τ leptons. Likewise, the decay of the atoms is hastened by the high probability of the constituent particles decaying. Nevertheless, if sufficient numbers of μ and τ pairs are produced in high energy astrophysical environments there may be significant production of true muonium and true tauonium, despite the small probabilities. This paper addresses this possibility. We have calculated the pair production spectra of μ and τ leptons from photon-photon annihilation and electron-positron annihilation in astrophysical environments. We have computed the cross sections for radiative recombination and direct annihilation of the pairs, and the decay constants for the various allowable decays, and the wavelengths and energies of the recombination and annihilation signatures. In this way we have calculated the probabilities for the formation of true muonium and true tauonium, and the branching ratios for the various <span class="hlt">observable</span> signatures. We have estimated the expected fluxes from accretion disks around microquasars and active galactic nuclei, and from interactions of jets with clouds and stars. We find that accretion disks around stellar mass black holes in our own Galaxy should have <span class="hlt">observable</span> signatures at x-ray and γ -ray energies that are in principle <span class="hlt">observable</span> with current observatories.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFMIN21C3715F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFMIN21C3715F"><span>Open <span class="hlt">Source</span> Dataturbine (OSDT) Android Sensorpod in Environmental <span class="hlt">Observing</span> Systems</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fountain, T. R.; Shin, P.; Tilak, S.; Trinh, T.; Smith, J.; Kram, S.</p> <p>2014-12-01</p> <p>The OSDT Android SensorPod is a custom-designed mobile computing platform for assembling wireless sensor networks for environmental monitoring applications. Funded by an award from the Gordon and Betty Moore Foundation, the OSDT SensorPod represents a significant technological advance in the application of mobile and cloud computing technologies to near-real-time applications in environmental science, natural resources management, and disaster response and recovery. It provides a modular architecture based on open standards and open-<span class="hlt">source</span> software that allows system developers to align their projects with industry best practices and technology trends, while avoiding commercial vendor lock-in to expensive proprietary software and hardware systems. The integration of mobile and cloud-computing infrastructure represents a disruptive technology in the field of environmental science, since basic assumptions about technology requirements are now open to revision, e.g., the roles of special purpose data loggers and dedicated site infrastructure. The OSDT Android SensorPod was designed with these considerations in mind, and the resulting system exhibits the following characteristics - it is flexible, efficient and robust. The system was developed and tested in the three science applications: 1) a fresh water limnology deployment in Wisconsin, 2) a near coastal marine science deployment at the UCSD Scripps Pier, and 3) a terrestrial ecological deployment in the mountains of Taiwan. As part of a public education and outreach effort, a Facebook page with daily ocean pH measurements from the UCSD Scripps pier was developed. Wireless sensor networks and the virtualization of data and network services is the future of environmental science infrastructure. The OSDT Android SensorPod was designed and developed to harness these new technology developments for environmental monitoring applications.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015APS..APR.M9003I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015APS..APR.M9003I"><span><span class="hlt">Observing</span> the Earliest Galaxies: Looking for the <span class="hlt">Sources</span> of Reionization</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Illingworth, Garth</p> <p>2015-04-01</p> <p>Systematic searches for the earliest galaxies in the reionization epoch finally became possible in 2009 when the Hubble Space Telescope was updated with a powerful new infrared camera during the final Shuttle servicing mission SM4 to Hubble. The reionization epoch represents the last major phase transition of the universe and was a major event in cosmic history. The intense ultraviolet radiation from young star-forming galaxies is increasingly considered to be the <span class="hlt">source</span> of the photons that reionized intergalactic hydrogen in the period between the ``dark ages'' (the time before the first stars and galaxies at about 100-200 million years after the Big Bang) and the end of reionization around 800-900 million years. Yet finding and measuring the earliest galaxies in this era of cosmic dawn has proven to a challenging task, even with Hubble's new infrared camera. I will discuss the deep imaging undertaken by Hubble and the remarkable insights that have accrued from the imaging datasets taken over the last decade on the Hubble Ultra-Deep Field (HUDF, HUDF09/12) and other regions. The HUDF datasets are central to the story and have been assembled into the eXtreme Deep Field (XDF), the deepest image ever from Hubble data. The XDF, when combined with results from shallower wide-area imaging surveys (e.g., GOODS, CANDELS) and with detections of galaxies from the Frontier Fields, has provided significant insights into the role of galaxies in reionization. Yet many questions remain. The puzzle is far from being fully solved and, while much will done over the next few years, the solution likely awaits the launch of JWST. NASA/STScI Grant HST-GO-11563.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19820040381&hterms=ISIS&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DISIS','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820040381&hterms=ISIS&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DISIS"><span>Auroral kilometric radiation <span class="hlt">source</span> region <span class="hlt">observations</span> from ISIS 1</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Benson, R. F.</p> <p>1981-01-01</p> <p>The ISIS 1 <span class="hlt">observations</span> of the high-frequency portion of the auroral kilometric radiation (AKR) spectrum are considered, that is, from the minimum frequency encountered for the extraordinary mode cut-off (approximately 450 kHz) to the upper frequency cut-off (approximately 800 kHz). AKR is found to be generated in the extraordinary mode just above the local cutoff frequency and to emanate in a direction that is nearly perpendicular to the magnetic field. It occurs within local depletions of electron density, where the ratio of plasma frequency to cyclotron frequency is below 0.2. The density depletion is restricted to altitudes above approximately 2,000 km, and the upper AKR frequency limit corresponds to the extraordinary cutoff frequency at this altitude.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3656933','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3656933"><span>Group Behavioural Responses of Atlantic Salmon (Salmo salar L.) to Light, <span class="hlt">Infrasound</span> and Sound Stimuli</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Bui, Samantha; Oppedal, Frode; Korsøen, Øyvind J.; Sonny, Damien; Dempster, Tim</p> <p>2013-01-01</p> <p>Understanding species-specific flight behaviours is essential in developing methods of guiding fish spatially, and requires knowledge on how groups of fish respond to aversive stimuli. By harnessing their natural behaviours, the use of physical manipulation or other potentially harmful procedures can be minimised. We examined the reactions of sea-caged groups of 50 salmon (1331±364 g) to short-term exposure to visual or acoustic stimuli. In light experiments, fish were exposed to one of three intensities of blue LED light (high, medium and low) or no light (control). Sound experiments included exposure to <span class="hlt">infrasound</span> (12 Hz), a surface disturbance event, the combination of <span class="hlt">infrasound</span> and surface disturbance, or no stimuli. Groups that experienced light, <span class="hlt">infrasound</span>, and the combination of <span class="hlt">infrasound</span> and surface disturbance treatments, elicited a marked change in vertical distribution, where fish dived to the bottom of the sea-cage for the duration of the stimulus. Light treatments, but not sound, also reduced the total echo-signal strength (indicative of swim bladder volume) after exposure to light, compared to pre-stimulus levels. Groups in <span class="hlt">infrasound</span> and combination treatments showed increased swimming activity during stimulus application, with swimming speeds tripled compared to that of controls. In all light and sound treatments, fish returned to their pre-stimulus swimming depths and speeds once exposure had ceased. This work establishes consistent, short-term avoidance responses to these stimuli, and provides a basis for methods to guide fish for aquaculture applications, or create avoidance barriers for conservation purposes. In doing so, we can achieve the manipulation of group position with minimal welfare impacts, to create more sustainable practices. PMID:23691087</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993GMS....80..239M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993GMS....80..239M"><span>DE 1 particle and wave <span class="hlt">observations</span> in an AKR <span class="hlt">source</span> region</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Menietti, J. D.; Burch, J. L.</p> <p></p> <p>Near the AKR <span class="hlt">source</span> region wave-particle interactions appear to have modified the <span class="hlt">observed</span> electron distributions. We compare the <span class="hlt">observations</span> to those predicted by recently published numerical simulations. <span class="hlt">Observations</span> of electron distributions indicate a region of perpendicular heating (T⊥/T∥>10) adjacent to and within the <span class="hlt">source</span> region. Loss cones, trapped particles, beams, and electron conical distributions are also <span class="hlt">observed</span> near and within the <span class="hlt">source</span> region, which extends perpendicular to the magnetic field line for at least 20 km in a density cavity. The high altitude plasma instrument on board the DE 1 satellite was operating during a near crossing of the AKR <span class="hlt">source</span> in the nightside auroral region.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993JGR....98.5865M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993JGR....98.5865M"><span>DE 1 particle and wave <span class="hlt">observations</span> in Auroral Kilometric Radiation (AKR) <span class="hlt">source</span> regions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Menietti, J. D.; Burch, J. L.; Winglee, R. M.; Gurnett, D. A.</p> <p>1993-04-01</p> <p>The high-altitude plasma instrument on board the DE 1 satellite was operating during several near crossings of the AKR <span class="hlt">source</span> in the nightside auroral region. <span class="hlt">Observations</span> of electron distributions indicate a region of perpendicular heating adjacent to, and within, the <span class="hlt">source</span> region. Loss cones, trapped particles, beams, and electron conical distributions are also <span class="hlt">observed</span> near and within the <span class="hlt">source</span> region, which extends perpendicular to the magnetic field line for at least 20 km. Near the AKR <span class="hlt">source</span> region wave-particle interactions appear to have modified the <span class="hlt">observed</span> electron distributions. We compare the <span class="hlt">observations</span> to those predicted by recently published numerical simulations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19840018452','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19840018452"><span>Catalog of infrared <span class="hlt">observations</span> including: Bibliography of infrared astronomy and index of infrared <span class="hlt">source</span> positions</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gezari, D. Y.; Schmitz, M.; Mead, J. M.</p> <p>1984-01-01</p> <p>The Catalog of Infrared <span class="hlt">Observations</span> and its Far Infrared Supplement summarize all infrared astronomical <span class="hlt">observations</span> at infrared wavelengths published in the scientific literature between 1965 and 1982. The Catalog includes as appendices the Bibliography of infrared astronomy which keys <span class="hlt">observations</span> in the Catalog with the original journal references, and the index of infrared <span class="hlt">source</span> positions which gives <span class="hlt">source</span> positions for alphabetically listed <span class="hlt">sources</span> in the Catalog. The Catalog data base contains over 85,000 <span class="hlt">observations</span> of about 10,000 infrared <span class="hlt">sources</span>, of which about 2,000 have no known visible counterpart.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/986599','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/986599"><span><span class="hlt">Observations</span> on vapor pressure in SPR caverns : <span class="hlt">sources</span>.</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Munson, Darrell Eugene</p> <p>2010-05-01</p> <p>The oil of the Strategic Petroleum Reserve (SPR) represents a national response to any potential emergency or intentional restriction of crude oil supply to this country, and conforms to International Agreements to maintain such a reserve. As assurance this reserve oil will be available in a timely manner should a restriction in supply occur, the oil of the reserve must meet certain transportation criteria. The transportation criteria require that the oil does not evolve dangerous gas, either explosive or toxic, while in the process of transport to, or storage at, the destination facility. This requirement can be a challenge because the stored oil can acquire dissolved gases while in the SPR. There have been a series of reports analyzing in exceptional detail the reasons for the increases, or regains, in gas content; however, there remains some uncertainty in these explanations and an inability to predict why the regains occur. Where the regains are prohibitive and exceed the criteria, the oil must undergo degasification, where excess portions of the volatile gas are removed. There are only two known <span class="hlt">sources</span> of gas regain, one is the salt dome formation itself which may contain gas inclusions from which gas can be released during oil processing or storage, and the second is increases of the gases release by the volatile components of the crude oil itself during storage, especially if the stored oil undergoes heating or is subject to biological generation processes. In this work, the earlier analyses are reexamined and significant alterations in conclusions are proposed. The alterations are based on how the fluid exchanges of brine and oil uptake gas released from domal salt during solutioning, and thereafter, during further exchanges of fluids. Transparency of the brine/oil interface and the transfer of gas across this interface remains an important unanswered question. The contribution from creep induced damage releasing gas from the salt surrounding the cavern is</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JGRA..121.2683M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JGRA..121.2683M"><span>Ionosonde tracking of <span class="hlt">infrasound</span> wavefronts in the thermosphere launched by seismic waves after the 2010 M8.8 Chile earthquake</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maruyama, Takashi; Yusupov, Kamil; Akchurin, Adel</p> <p>2016-03-01</p> <p>Ionospheric disturbances associated with the M8.8 Chile earthquake (35.91°S, 72.73°W) on 27 February 2010 were <span class="hlt">observed</span> at Kazan, Russia (55.85°N, 48.81°E). Rapid-run ionograms at 1 min intervals exhibited multiple-cusp signatures (MCSs) for more than 30 min, which have been <span class="hlt">observed</span> several times after large earthquakes. The ionospheric disturbances were caused by <span class="hlt">infrasound</span> propagating upward in the atmosphere, which modified the electron density distribution through ion-neutral collisions. The anomaly of the vertical electron density distribution responsible for the MCSs was analyzed by converting the ionogram traces into real height profiles. The density profiles at 1 min intervals allowed the tracking of the vertical propagation of <span class="hlt">infrasound</span> and provided information on parameters of acoustic waves, which was not possible from the previous measurements such as standard ionograms at 5-15 min intervals, HF Doppler soundings, and total electron content using satellite beacon signals. The speed of acoustic waves in the thermosphere was evaluated from the consecutive ionograms with MCSs, and it was found that the thermospheric temperature was slightly higher than that calculated using the Mass Spectrometer and Incoherent Scatter Radar empirical model (NRLMSISE-00).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012EGUGA..14.4306G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012EGUGA..14.4306G"><span>Infrasonic and seismic signals from earthquakes and explosions <span class="hlt">observed</span> with Plostina seismo-acoustic array</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ghica, D.; Ionescu, C.</p> <p>2012-04-01</p> <p>Plostina seismo-acoustic array has been recently deployed by the National Institute for Earth Physics in the central part of Romania, near the Vrancea epicentral area. The array has a 2.5 km aperture and consists of 7 seismic sites (PLOR) and 7 collocated <span class="hlt">infrasound</span> instruments (IPLOR). The array is being used to assess the importance of collocated seismic and acoustic sensors for the purposes of (1) seismic monitoring of the local and regional events, and (2) acoustic measurement, consisting of detection of the <span class="hlt">infrasound</span> events (explosions, mine and quarry blasts, earthquakes, aircraft etc.). This paper focuses on characterization of infrasonic and seismic signals from the earthquakes and explosions (accidental and mining type). Two Vrancea earthquakes with magnitude above 5.0 were selected to this study: one occurred on 1st of May 2011 (MD = 5.3, h = 146 km), and the other one, on 4th October 2011 (MD = 5.2, h = 142 km). The infrasonic signals from the earthquakes have the appearance of the vertical component of seismic signals. Because the mechanism of the infrasonic wave formation is the coupling of seismic waves with the atmosphere, trace velocity values for such signals are compatible with the characteristics of the various seismic phases <span class="hlt">observed</span> with PLOR array. The study evaluates and characterizes, as well, <span class="hlt">infrasound</span> and seismic data recorded from the explosion caused by the military accident produced at Evangelos Florakis Naval Base, in Cyprus, on 11th July 2011. Additionally, seismo-acoustic signals presumed to be related to strong mine and quarry blasts were investigated. Ground truth of mine <span class="hlt">observations</span> provides validation of this interpretation. The combined seismo-acoustic analysis uses two types of detectors for signal identification: one is the automatic detector DFX-PMCC, applied for <span class="hlt">infrasound</span> detection and characterization, while the other one, which is used for seismic data, is based on array processing techniques (beamforming and frequency</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21576566','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21576566"><span>LUMINOSITY FUNCTIONS AND POINT-<span class="hlt">SOURCE</span> PROPERTIES FROM MULTIPLE CHANDRA <span class="hlt">OBSERVATIONS</span> OF M81</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Sell, P. H.; Pooley, D.; Heinz, S.; Zezas, A.; Homan, J.; Lewin, W. H. G.</p> <p>2011-07-01</p> <p>We present an analysis of 15 Chandra <span class="hlt">observations</span> of the nearby spiral galaxy M81 taken over the course of six weeks in 2005 May-July. Each <span class="hlt">observation</span> reaches a sensitivity of {approx}10{sup 37} erg s{sup -1}. With these <span class="hlt">observations</span> and one previous deeper Chandra <span class="hlt">observation</span>, we compile a master <span class="hlt">source</span> list of 265 point <span class="hlt">sources</span>, extract and fit their spectra, and differentiate basic populations of <span class="hlt">sources</span> through their colors. We also carry out variability analyses of individual point <span class="hlt">sources</span> and of X-ray luminosity functions (XLFs) in multiple regions of M81 on timescales of days, months, and years. We find that, despite measuring significant variability in a considerable fraction of <span class="hlt">sources</span>, snapshot <span class="hlt">observations</span> provide a consistent determination of the XLF of M81. We also fit the XLFs for multiple regions of M81 and, using common parameterizations, compare these luminosity functions to those of two other spiral galaxies, M31 and the Milky Way.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA530075','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA530075"><span>Seismic <span class="hlt">Observations</span> and Interpretation in NE China, <span class="hlt">Infrasound</span> <span class="hlt">Observations</span> and Interpretation in Utah</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2010-07-30</p> <p>INTRODUCTION Motivation The Yanqing-Huailai Basin is the geographic focus of this study and is one of the extensional features in the North...by secondary sources—regions that can be remote from the epicenter. 51 INTRODUCTION Infrasonic signals, which correspond to acoustic energy at...felt in Nevada, Utah, California , Idaho, Montana, Wyoming, Arizona, Oregon, and Washington. More than 3100 entries in more than 300 ZIP areas were</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780037753&hterms=infrared+spectrophotometry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dinfrared%2Bspectrophotometry','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780037753&hterms=infrared+spectrophotometry&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dinfrared%2Bspectrophotometry"><span>Infrared <span class="hlt">observations</span> of the galactic center. I - Nature of the compact <span class="hlt">sources</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Becklin, E. E.; Matthews, K.; Neugebauer, G.; Willner, S. P.</p> <p>1978-01-01</p> <p>Photometry from 1.25 to 12 micrometers and spectrophotometry from 8 to 13 micrometers of the compact <span class="hlt">sources</span> found in the galactic-center region are reported. In addition, revised 10 and new 20 micrometers maps with 2''.3 resolution are given. The nature of the compact <span class="hlt">sources</span> is discussed. Some are best identified as stars or star clusters; the brightest <span class="hlt">source</span> at 2 micrometers is probably a supergiant, and the infrared <span class="hlt">source</span> near the nonthermal radio <span class="hlt">source</span> is probably a stellar cluster with density greater than 1 million solar masses/cu pc. Other <span class="hlt">sources</span> emit most of their luminosity at wavelengths of 10 micrometers and greater; this emission is probably from heated dust. One of the <span class="hlt">sources</span> is <span class="hlt">observationally</span> similar to extremely red OH/infrared stars. Other <span class="hlt">sources</span> have luminosities and linear sizes similar to those of compact H II regions; emission from optically thin silicate dust is seen in these.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014NatSR...4E6105K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014NatSR...4E6105K"><span>Nanotube Aerogel Sheet Flutter for Actuation, Power Generation, and <span class="hlt">Infrasound</span> Detection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kang, Tae June; Kim, Taewoo; Jang, Eui Yun; Im, Hyeongwook; Lepro-Chavez, Xavier; Ovalle-Robles, Raquel; Oh, Jiyoung; Kozlov, Mikhail E.; Baughman, Ray H.; Lee, Hong H.; Kim, Yong Hyup</p> <p>2014-08-01</p> <p>Electromagnetic induction (EMI) is a mechanism of classical physics that can be utilized to convert mechanical energy to electrical energy or electrical to mechanical energy. This mechanism has not been exploited fully because of lack of a material with a sufficiently low force constant. We here show that carbon nanotube (CNT) aerogel sheets can exploit EMI to provide mechanical actuation at very low applied voltages, to harvest mechanical energy from small air pressure fluctuations, and to detect <span class="hlt">infrasound</span> at inaudible frequencies below 20 Hz. Using conformal deposition of 100 nm thick aluminum coatings on the nanotubes in the sheets, mechanical actuation can be obtained by applying millivolts, as compared with the thousand volts needed to achieve giant-stroke electrostatic actuation of carbon nanotube aerogel sheets. Device simplicity and performance suggest possible applications as an energy harvester of low energy air fluctuations and as a sensor for <span class="hlt">infrasound</span> frequencies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4135338','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4135338"><span>Nanotube Aerogel Sheet Flutter for Actuation, Power Generation, and <span class="hlt">Infrasound</span> Detection</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Kang, Tae June; Kim, Taewoo; Jang, Eui Yun; Im, Hyeongwook; Lepro-Chavez, Xavier; Ovalle-Robles, Raquel; Oh, Jiyoung; Kozlov, Mikhail E.; Baughman, Ray H.; Lee, Hong H.; Kim, Yong Hyup</p> <p>2014-01-01</p> <p>Electromagnetic induction (EMI) is a mechanism of classical physics that can be utilized to convert mechanical energy to electrical energy or electrical to mechanical energy. This mechanism has not been exploited fully because of lack of a material with a sufficiently low force constant. We here show that carbon nanotube (CNT) aerogel sheets can exploit EMI to provide mechanical actuation at very low applied voltages, to harvest mechanical energy from small air pressure fluctuations, and to detect <span class="hlt">infrasound</span> at inaudible frequencies below 20 Hz. Using conformal deposition of 100 nm thick aluminum coatings on the nanotubes in the sheets, mechanical actuation can be obtained by applying millivolts, as compared with the thousand volts needed to achieve giant-stroke electrostatic actuation of carbon nanotube aerogel sheets. Device simplicity and performance suggest possible applications as an energy harvester of low energy air fluctuations and as a sensor for <span class="hlt">infrasound</span> frequencies. PMID:25130708</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_12");'>12</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li class="active"><span>14</span></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_14 --> <div id="page_15" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="281"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoRL..42.6324J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoRL..42.6324J"><span>Lahar <span class="hlt">infrasound</span> associated with Volcán Villarrica's 3 March 2015 eruption</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Johnson, Jeffrey B.; Palma, Jose L.</p> <p>2015-08-01</p> <p>The paroxysmal 2015 eruption of Volcán Villarrica (Chile) produced a 2.5 h long lahar, which descended more than 20 km within the Rio Correntoso/Turbio drainage and destroyed two small bridges. A three-element <span class="hlt">infrasound</span> array 10 km from the summit, and 4 km from the lahar's closest approach, was used to study the flow's progression. Array processing using cross-correlation lag times and semblance places constraints on the lahar's dynamics, including detection of an initial flow pulse that traveled from 2 to 12 km at an average speed of 38 m/s. Subsequently, the lahar signal evolved to a relatively stationary infrasonic tremor located 10 to 12 km from the vent and adjacent to a topographic notch, through which sound may have preferentially diffracted toward the recording site. This study demonstrates the powerful capabilities of <span class="hlt">infrasound</span> arrays for lahar study and suggests their potential application for future hazard monitoring.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA590009','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA590009"><span>Detection Optimization of the Progressive Multi-Channel Correlation Algorithm Used in <span class="hlt">Infrasound</span> Nuclear Treaty Monitoring</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2013-03-01</p> <p>microbaroms, mountain associated waves, volcanic eruptions , auroras, earthquakes, rockets, and explosions [5] [6]. Examination of <span class="hlt">infrasound</span> dating...progressive search for distant sensors to add to initial sub- arrays, a PMCC pitfall more comprehensively addressed in Section 2.3. WinPMCC’s solution to this...the goal is to minimize the total number of false alarm and missed detection categorization decisions. Specifically, the solution to this approach</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/1326653','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/1326653"><span>Detection of regional <span class="hlt">infrasound</span> signals using array data: Testing, tuning, and physical interpretation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Park, Junghyun; Stump, Brian W.; Hayward, Chris; Arrowsmith, Stephen J.; Che, Il-Young; Drob, Douglas P.</p> <p>2016-07-14</p> <p>This work quantifies the physical characteristics of <span class="hlt">infrasound</span> signal and noise, assesses their temporal variations, and determines the degree to which these effects can be predicted by time-varying atmospheric models to estimate array and network performance. An automated detector that accounts for both correlated and uncorrelated noise is applied to <span class="hlt">infrasound</span> data from three seismo-acoustic arrays in South Korea (BRDAR, CHNAR, and KSGAR), cooperatively operated by Korea Institute of Geoscience and Mineral Resources (KIGAM) and Southern Methodist University (SMU). Arrays located on an island and near the coast have higher noise power, consistent with both higher wind speeds and seasonably variable ocean wave contributions. On the basis of the adaptive F-detector quantification of time variable environmental effects, the time-dependent scaling variable is shown to be dependent on both weather conditions and local site effects. Significant seasonal variations in <span class="hlt">infrasound</span> detections including daily time of occurrence, detection numbers, and phase velocity/azimuth estimates are documented. These time-dependent effects are strongly correlated with atmospheric winds and temperatures and are predicted by available atmospheric specifications. As a result, this suggests that commonly available atmospheric specifications can be used to predict both station and network detection performance, and an appropriate forward model improves location capabilities as a function of time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/pages/biblio/1326653-detection-regional-infrasound-signals-using-array-data-testing-tuning-physical-interpretation','SCIGOV-DOEP'); return false;" href="https://www.osti.gov/pages/biblio/1326653-detection-regional-infrasound-signals-using-array-data-testing-tuning-physical-interpretation"><span>Detection of regional <span class="hlt">infrasound</span> signals using array data: Testing, tuning, and physical interpretation</span></a></p> <p><a target="_blank" href="http://www.osti.gov/pages">DOE PAGES</a></p> <p>Park, Junghyun; Stump, Brian W.; Hayward, Chris; ...</p> <p>2016-07-14</p> <p>This work quantifies the physical characteristics of <span class="hlt">infrasound</span> signal and noise, assesses their temporal variations, and determines the degree to which these effects can be predicted by time-varying atmospheric models to estimate array and network performance. An automated detector that accounts for both correlated and uncorrelated noise is applied to <span class="hlt">infrasound</span> data from three seismo-acoustic arrays in South Korea (BRDAR, CHNAR, and KSGAR), cooperatively operated by Korea Institute of Geoscience and Mineral Resources (KIGAM) and Southern Methodist University (SMU). Arrays located on an island and near the coast have higher noise power, consistent with both higher wind speeds and seasonablymore » variable ocean wave contributions. On the basis of the adaptive F-detector quantification of time variable environmental effects, the time-dependent scaling variable is shown to be dependent on both weather conditions and local site effects. Significant seasonal variations in <span class="hlt">infrasound</span> detections including daily time of occurrence, detection numbers, and phase velocity/azimuth estimates are documented. These time-dependent effects are strongly correlated with atmospheric winds and temperatures and are predicted by available atmospheric specifications. As a result, this suggests that commonly available atmospheric specifications can be used to predict both station and network detection performance, and an appropriate forward model improves location capabilities as a function of time.« less</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/19045635','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/19045635"><span>Finite-difference time-domain synthesis of <span class="hlt">infrasound</span> propagation through an absorbing atmosphere.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>de Groot-Hedlin, C</p> <p>2008-09-01</p> <p>Equations applicable to finite-difference time-domain (FDTD) computation of <span class="hlt">infrasound</span> propagation through an absorbing atmosphere are derived and examined in this paper. It is shown that over altitudes up to 160 km, and at frequencies relevant to global <span class="hlt">infrasound</span> propagation, i.e., 0.02-5 Hz, the acoustic absorption in dB/m varies approximately as the square of the propagation frequency plus a small constant term. A second-order differential equation is presented for an atmosphere modeled as a compressible Newtonian fluid with low shear viscosity, acted on by a small external damping force. It is shown that the solution to this equation represents pressure fluctuations with the attenuation indicated above. Increased dispersion is predicted at altitudes over 100 km at <span class="hlt">infrasound</span> frequencies. The governing propagation equation is separated into two partial differential equations that are first order in time for FDTD implementation. A numerical analysis of errors inherent to this FDTD method shows that the attenuation term imposes additional stability constraints on the FDTD algorithm. Comparison of FDTD results for models with and without attenuation shows that the predicted transmission losses for the attenuating media agree with those computed from synthesized waveforms.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/27475150','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/27475150"><span>Detection of regional <span class="hlt">infrasound</span> signals using array data: Testing, tuning, and physical interpretation.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Park, Junghyun; Stump, Brian W; Hayward, Chris; Arrowsmith, Stephen J; Che, Il-Young; Drob, Douglas P</p> <p>2016-07-01</p> <p>This work quantifies the physical characteristics of <span class="hlt">infrasound</span> signal and noise, assesses their temporal variations, and determines the degree to which these effects can be predicted by time-varying atmospheric models to estimate array and network performance. An automated detector that accounts for both correlated and uncorrelated noise is applied to <span class="hlt">infrasound</span> data from three seismo-acoustic arrays in South Korea (BRDAR, CHNAR, and KSGAR), cooperatively operated by Korea Institute of Geoscience and Mineral Resources (KIGAM) and Southern Methodist University (SMU). Arrays located on an island and near the coast have higher noise power, consistent with both higher wind speeds and seasonably variable ocean wave contributions. On the basis of the adaptive F-detector quantification of time variable environmental effects, the time-dependent scaling variable is shown to be dependent on both weather conditions and local site effects. Significant seasonal variations in <span class="hlt">infrasound</span> detections including daily time of occurrence, detection numbers, and phase velocity/azimuth estimates are documented. These time-dependent effects are strongly correlated with atmospheric winds and temperatures and are predicted by available atmospheric specifications. This suggests that commonly available atmospheric specifications can be used to predict both station and network detection performance, and an appropriate forward model improves location capabilities as a function of time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AJ....152..151X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AJ....152..151X"><span>The <span class="hlt">Source</span> Structure of 0642+449 Detected from the CONT14 <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xu, Ming H.; Heinkelmann, Robert; Anderson, James M.; Mora-Diaz, Julian; Schuh, Harald; Wang, Guang L.</p> <p>2016-11-01</p> <p>The CONT14 campaign with state-of-the-art very long baseline interferometry (VLBI) data has <span class="hlt">observed</span> the <span class="hlt">source</span> 0642+449 with about 1000 <span class="hlt">observables</span> each day during a continuous <span class="hlt">observing</span> period of 15 days, providing tens of thousands of closure delays—the sum of the delays around a closed loop of baselines. The closure delay is independent of the instrumental and propagation delays and provides valuable additional information about the <span class="hlt">source</span> structure. We demonstrate the use of this new “observable” for the determination of the structure in the radio <span class="hlt">source</span> 0642+449. This <span class="hlt">source</span>, as one of the defining <span class="hlt">sources</span> in the second realization of the International Celestial Reference Frame, is found to have two point-like components with a relative position offset of -426 microarcseconds (μas) in R.A. and -66 μas in decl. The two components are almost equally bright, with a flux-density ratio of 0.92. The standard deviation of closure delays for <span class="hlt">source</span> 0642+449 was reduced from 139 to 90 ps by using this two-component model. Closure delays larger than 1 ns are found to be related to the <span class="hlt">source</span> structure, demonstrating that structure effects for a <span class="hlt">source</span> with this simple structure could be up to tens of nanoseconds. The method described in this paper does not rely on a priori <span class="hlt">source</span> structure information, such as knowledge of <span class="hlt">source</span> structure determined from direct (Fourier) imaging of the same <span class="hlt">observations</span> or <span class="hlt">observations</span> at other epochs. We anticipate our study to be a starting point for more effective determination of the structure effect in VLBI <span class="hlt">observations</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20090023877','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20090023877"><span>Chemical <span class="hlt">Source</span> Inversion using Assimilated Constituent <span class="hlt">Observations</span> in an Idealized Two-dimensional System</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tangborn, Andrew; Cooper, Robert; Pawson, Steven; Sun, Zhibin</p> <p>2009-01-01</p> <p>We present a <span class="hlt">source</span> inversion technique for chemical constituents that uses assimilated constituent <span class="hlt">observations</span> rather than directly using the <span class="hlt">observations</span>. The method is tested with a simple model problem, which is a two-dimensional Fourier-Galerkin transport model combined with a Kalman filter for data assimilation. Inversion is carried out using a Green's function method and <span class="hlt">observations</span> are simulated from a true state with added Gaussian noise. The forecast state uses the same spectral spectral model, but differs by an unbiased Gaussian model error, and emissions models with constant errors. The numerical experiments employ both simulated in situ and satellite <span class="hlt">observation</span> networks. <span class="hlt">Source</span> inversion was carried out by either direct use of synthetically generated <span class="hlt">observations</span> with added noise, or by first assimilating the <span class="hlt">observations</span> and using the analyses to extract <span class="hlt">observations</span>. We have conducted 20 identical twin experiments for each set of <span class="hlt">source</span> and <span class="hlt">observation</span> configurations, and find that in the limiting cases of a very few localized <span class="hlt">observations</span>, or an extremely large <span class="hlt">observation</span> network there is little advantage to carrying out assimilation first. However, in intermediate <span class="hlt">observation</span> densities, there decreases in <span class="hlt">source</span> inversion error standard deviation using the Kalman filter algorithm followed by Green's function inversion by 50% to 95%.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014acm..conf...63B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014acm..conf...63B"><span>Using the international monitoring system of seismic, <span class="hlt">infrasound</span>, and hydroacoustic sensors for global airburst detection</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brown, P.</p> <p>2014-07-01</p> <p>The impact of meter-sized objects with the Earth occurs every few weeks [1,2]. Most of these collisions result in airbursts, here defined as impacts where the meteoroid's initial kinetic energy is of order a small nuclear weapon (> 0.1 kilotons of TNT equivalent = 4.185×10^{11} J) and where this energy is fully deposited at high altitude in the atmosphere. Historically, the majority of these airbursts go undetected over oceans or remote land areas as dedicated fireball camera networks (eg.[ 3]) cover less than 1 % of the globe. Airbursts often produce meteorite falls and hence airburst data may yield pre-atmospheric orbits and physical properties for the impacting NEO providing context for recovered meteorite samples [4]. With the advent of more capable telescopic survey systems, pre-atmospheric detection of NEO-producing airbursts has become possible as evidenced by the impacts of 2014 AA and 2008 TC_3 [5]. Detection of ''terminal plungers'' is expected to become more common as projects such as ATLAS [6] become operational. This increases the need for instrumental data of the corresponding airburst, particularly its location and energy. Beginning in the late 1990s, a global network of seismic, <span class="hlt">infrasound</span>, and hydroacoustic sensors has been deployed globally to provide treaty verification for a nuclear test ban. This network is the International Monitoring System (IMS) overseen by Comprehensive Nuclear Test Ban Treaty Organisation (CTBTO) [7]. The IMS is a unique global resource for detection of explosions worldwide and in recent years shock waves from many airbursts [8] have been detected by the system. Data from the IMS permits airburst location, origin time and energy to be measured. In rare cases, <span class="hlt">source</span> heights, trajectories, and details of fragmentation may be obtained. Here the current capabilities of the IMS will be presented in the context of airburst detection and characterization. Empirical characteristics of the long-range sound produced by airbursts</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://files.eric.ed.gov/fulltext/ED562869.pdf','ERIC'); return false;" href="http://files.eric.ed.gov/fulltext/ED562869.pdf"><span>Using Generalizability Theory to Examine <span class="hlt">Sources</span> of Variance in <span class="hlt">Observed</span> Behaviors within High School Classrooms</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Abry, Tashia; Cash, Anne H.; Bradshaw, Catherine P.</p> <p>2014-01-01</p> <p>Generalizability theory (GT) offers a useful framework for estimating the reliability of a measure while accounting for multiple <span class="hlt">sources</span> of error variance. The purpose of this study was to use GT to examine multiple <span class="hlt">sources</span> of variance in and the reliability of school-level teacher and high school student behaviors as <span class="hlt">observed</span> using the tool,…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhRvD..90d3005A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhRvD..90d3005A"><span>Pinpointing extragalactic neutrino <span class="hlt">sources</span> in light of recent IceCube <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ahlers, Markus; Halzen, Francis</p> <p>2014-08-01</p> <p>The IceCube Collaboration has recently reported the <span class="hlt">observation</span> of a flux of high-energy astrophysical neutrinos. The angular distribution of events is consistent with an isotropic arrival direction of neutrinos which is expected for an extragalactic origin. We estimate the prospects of detecting individual neutrino <span class="hlt">sources</span> from a quasidiffuse superposition of many extragalactic <span class="hlt">sources</span> at the level of the IceCube <span class="hlt">observation</span>. Unlike previous analyses, we take into account ensemble variations of the <span class="hlt">source</span> distribution as well as the event statistics of individual <span class="hlt">sources</span>. We show that IceCube in its present configuration is sensitive to rare ≲10-8 Mpc-3 yr-1 transient <span class="hlt">source</span> classes within five years of operation via the <span class="hlt">observation</span> of event clusters. Identification of time-independent <span class="hlt">sources</span> is more challenging due to larger backgrounds. We estimate that during the same period IceCube is sensitive to sparse <span class="hlt">sources</span> with densities of ≲10-6 Mpc-3 via association of events with the closest 100 <span class="hlt">sources</span> of an ensemble. We show that a next-generation neutrino observatory with 5 times the effective area of IceCube and otherwise similar detector performance would increase the sensitivity to <span class="hlt">source</span> densities and rates by about 2 orders of magnitude.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22365559','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22365559"><span>JVLA <span class="hlt">observations</span> of IC 348 SW: Compact radio <span class="hlt">sources</span> and their nature</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Rodríguez, Luis F.; Zapata, Luis A.; Palau, Aina E-mail: l.zapata@crya.unam.mx</p> <p>2014-07-20</p> <p>We present sensitive 2.1 and 3.3 cm Jansky Very Large Array radio continuum <span class="hlt">observations</span> of the region IC 348 SW. We detect a total of 10 compact radio <span class="hlt">sources</span> in the region, 7 of which are first reported here. One of the <span class="hlt">sources</span> is associated with the remarkable periodic time-variable infrared <span class="hlt">source</span> LRLL 54361, opening the possibility of monitoring this object at radio wavelengths. Four of the <span class="hlt">sources</span> appear to be powering outflows in the region, including HH 211 and HH 797. In the case of the rotating outflow HH 797, we detect a double radio <span class="hlt">source</span> at its center, separated by ∼3''. Two of the <span class="hlt">sources</span> are associated with infrared stars that possibly have gyrosynchrotron emission produced in active magnetospheres. Finally, three of the <span class="hlt">sources</span> are interpreted as background objects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MNRAS.460.3829M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MNRAS.460.3829M"><span>Swift <span class="hlt">observations</span> of unidentified radio <span class="hlt">sources</span> in the revised Third Cambridge Catalogue</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Maselli, A.; Massaro, F.; Cusumano, G.; La Parola, V.; Harris, D. E.; Paggi, A.; Liuzzo, E.; Tremblay, G. R.; Baum, S. A.; O'Dea, C. P.</p> <p>2016-08-01</p> <p>We have investigated a group of unassociated radio <span class="hlt">sources</span> included in the Third Cambridge Catalogue (3CR) to increase the multifrequency information on them and possibly obtain an identification. We have carried out an <span class="hlt">observational</span> campaign with the Swift satellite to <span class="hlt">observe</span> with the Ultraviolet/Optical Telescope (UVOT) and the X-Ray Telescope (XRT) the field of view of 21 bright NRAO VLA Sky Survey (NVSS) <span class="hlt">sources</span> within the positional uncertainty region of the 3CR <span class="hlt">sources</span>. Furthermore, we have searched in the recent AllWISE <span class="hlt">Source</span> Catalogue for infrared <span class="hlt">sources</span> matching the position of these NVSS <span class="hlt">sources</span>. We have detected significant emission in the soft X-ray band for nine of the investigated NVSS <span class="hlt">sources</span>. To all of them, and in four cases with no soft X-ray association, we have associated a Wide-field Infrared Survey Explorer infrared counterpart. Eight of these infrared candidates have not been proposed earlier in the literature. In the five remaining cases our candidate matches one among a few optical candidates suggested for the same 3CR <span class="hlt">source</span> in previous studies. No <span class="hlt">source</span> has been detected in the UVOT filters at the position of the NVSS objects, confirming the scenario that all of them are heavily obscured. With this in mind, a spectroscopic campaign, preferably in the infrared band, will be necessary to establish the nature of the <span class="hlt">sources</span> that we have finally identified.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19770015077','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19770015077"><span><span class="hlt">Observation</span> of the X-ray <span class="hlt">source</span> Sco X-1 from Skylab. [radiant flux density</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wilson, R. M.</p> <p>1977-01-01</p> <p>An attempt to <span class="hlt">observe</span> the discrete X-ray <span class="hlt">source</span> Sco X-1 on 20 September 1973 between 0856 and 0920 UT is reported. Data obtained with the ATM/S-056 X-ray event analyzer, in particular the flux <span class="hlt">observed</span> with the 1.71 to 4.96 KeV counter, is analyzed. No photographic image of the <span class="hlt">source</span> was obtained because Sco X-1 was outside the field of view of the X-ray telescope.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1985ApJ...295..134F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1985ApJ...295..134F"><span>VLBI <span class="hlt">observations</span> at 22.2 gigahertz of the radio <span class="hlt">source</span> 0552 + 398 (DA 193)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fey, A. L.; Spangler, S. R.; Mutel, R. L.; Benson, J. M.</p> <p>1985-08-01</p> <p>The authors report 22.2 GHz <span class="hlt">observations</span> of the quasar 0552+398 (DA 193). The data are used to refine the <span class="hlt">source</span> structure model and magnetic field estimate previously reported by Spangler and colleagues in 1983. The <span class="hlt">source</span> is found to be more compact and the magnetic field to be weaker than indicated by the previous <span class="hlt">observations</span>. It is suggested that the object may be considered a highly compact, "naked core" object.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920046806&hterms=Monsters&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DMonsters','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920046806&hterms=Monsters&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DMonsters"><span>VLA <span class="hlt">observations</span> of radio <span class="hlt">sources</span> in interacting galaxy pairs in poor clusters</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Batuski, David J.; Hanisch, Robert J.; Burns, Jack O.</p> <p>1992-01-01</p> <p><span class="hlt">Observations</span> of 16 radio <span class="hlt">sources</span> in interacting galaxies in 14 poor clusters were made using the Very Large Array in the B configuration at lambda of 6 and 2 cm. These <span class="hlt">sources</span> had been unresolved in earlier <span class="hlt">observations</span> at lambda of 21 cm, and were chosen as a sample to determine which of three models for radio <span class="hlt">source</span> formation actually pertains in interacting galaxies. From the analysis of this sample, the starburst model appears most successful, but the 'central monster' model could pertain in some cases.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19780012086','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19780012086"><span><span class="hlt">Observations</span> of low luminosity X-ray <span class="hlt">sources</span> in Vela-Puppis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pravdo, S. H.; Becker, R. H.; Boldt, E. A.; Holt, S. S.; Erlemitsos, P. J.; Swank, J. H.</p> <p>1978-01-01</p> <p>Results of a study of the X-ray emission from a small portion of the galactic plane near galactic longitude 260 deg are presented. This region contains at least six low luminosity X-ray <span class="hlt">sources</span> within approximately 10 deg. of PSRO833-45, which is near the center of the Gum Nebula. The X-ray <span class="hlt">source</span> associated with the Vela pulsar, 4U0833-45, is <span class="hlt">observed</span> at twice its 4U catalogue intensity. The lack of X-ray pulsations at the pulsar period, the non thermal power law spectrum, and models of the X-ray come from an extended <span class="hlt">source</span> approximately 1 deg in radius. The <span class="hlt">observation</span> of a high temperature spectrum in a field of view containing only Puppis A among known <span class="hlt">sources</span> has led to the discovery of a new OSO-8 <span class="hlt">source</span>, OSO752-39. Other spectra from this region are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/21895058','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/21895058"><span>In situ calibration of atmospheric-<span class="hlt">infrasound</span> sensors including the effects of wind-noise-reduction pipe systems.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Gabrielson, Thomas B</p> <p>2011-09-01</p> <p>A worldwide network of more than 40 <span class="hlt">infrasound</span> monitoring stations has been established as part of the effort to ensure compliance with the Comprehensive Nuclear Test Ban Treaty. Each station has four to eight individual <span class="hlt">infrasound</span> elements in a kilometer-scale array for detection and bearing determination of acoustic events. The frequency range of interest covers a three-decade range-roughly from 0.01 to 10 Hz. A typical <span class="hlt">infrasound</span> array element consists of a receiving transducer connected to a multiple-inlet pipe network to average spatially over the short-wavelength turbulence-associated "wind noise." Although the frequency response of the transducer itself may be known, the wind-noise reduction system modifies that response. In order to understand the system's impact on detection and identification of acoustical events, the overall frequency response must be determined. This paper describes a technique for measuring the absolute magnitude and phase of the frequency response of an <span class="hlt">infrasound</span> element including the wind-noise-reduction piping by comparison calibration using ambient noise and a reference-microphone system. Measured coherence between the reference and the <span class="hlt">infrasound</span> element and the consistency between the magnitude and the phase provide quality checks on the process.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19750017777&hterms=sas&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dsas','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19750017777&hterms=sas&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Dsas"><span><span class="hlt">Observations</span> of discrete gamma ray <span class="hlt">sources</span> with SAS-2. [compact <span class="hlt">sources</span> centered on Crab nebula and Vela X supernova remnant</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Thompson, D. J.; Fichtel, C. E.; Hartman, R. C.; Kniffen, D. A.; Bignami, G. F.</p> <p>1974-01-01</p> <p>Compact gamma ray <span class="hlt">sources</span> centered on the Crab nebula and the Vela X supernova remnant are considered. An excess in the galactic radiation was <span class="hlt">observed</span> in both regions. Data indicate that a large fraction of this flux is pulsed. The excess from the Vela region could reflect either a large-scale galactic feature, such as a superposition of spiral arm segments, or it could be associated with the Vela supernova remnant. Low-energy gamma ray bursts were <span class="hlt">observed</span> in the SAS-2 anticoincidence shielding.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950036102&hterms=charles+fishman&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dcharles%2Bfishman','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950036102&hterms=charles+fishman&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dcharles%2Bfishman"><span>Constraints on galactic distributions of gamma-ray burst <span class="hlt">sources</span> from BATSE <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hakkila, Jon; Meegan, Charles A.; Pendleton, Geoffrey N.; Fishman, Gerald J.; Wilson, Robert B.; Paciesas, William S.; Brock, Martin N.; Horack, John M.</p> <p>1994-01-01</p> <p>The paradigm that gamma-ray bursts originate from Galactic <span class="hlt">sources</span> is studied in detail using the angular and intensity distributions <span class="hlt">observed</span> by the Burst and Transient <span class="hlt">Source</span> Experiment (BATSE) on NASA's Compton Gamma Ray Observatory (CGRO). Monte Carlo models of gamma-ray burst spatial distributions and luminosity functions are used to simulate bursts, which are then folded through mathematical models of BATSE selection effects. The <span class="hlt">observed</span> and computed angular intensity distributions are analyzed using modifications of standard statistical homogeneity and isotropy studies. Analysis of the BATSE angular and intensity distributions greatly constrains the origins and luminosities of burst <span class="hlt">sources</span>. In particular, it appears that no single population of <span class="hlt">sources</span> confined to a Galactic disk, halo, or localized spiral arm satisfactorily explains BATSE <span class="hlt">observations</span> and that effects of the burst luminosity function are secondary when considering such models. One family of models that still satisfies BATSE <span class="hlt">observations</span> comprises <span class="hlt">sources</span> located in an extended spherical Galactic corona. Coronal models are limited to small ranges of burst luminosity and core radius, and the allowed parameter space for such models shrinks with each new burst BATSE <span class="hlt">observes</span>. Multiple-population models of bursts are found to work only if (1) the primary population accounts for the general isotropy and inhomogeneity seen in the BATSE <span class="hlt">observations</span> and (2) secondary populations either have characteristics similar to the primary population or contain numbers that are small relative to the primary population.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_13");'>13</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li class="active"><span>15</span></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_15 --> <div id="page_16" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="301"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22089676','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22089676"><span>DEEP CHANDRA MONITORING <span class="hlt">OBSERVATIONS</span> OF NGC 4649. I. CATALOG OF <span class="hlt">SOURCE</span> PROPERTIES</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Luo, B.; Fabbiano, G.; Strader, J.; Kim, D.-W.; Fragos, T.; Brodie, J. P.; King, A.; Zezas, A.</p> <p>2013-02-15</p> <p>We present the X-ray <span class="hlt">source</span> catalog for the Chandra monitoring <span class="hlt">observations</span> of the elliptical galaxy, NGC 4649. The galaxy has been <span class="hlt">observed</span> with Chandra ACIS-S3 in six separate pointings, reaching a total exposure of 299 ks. There are 501 X-ray <span class="hlt">sources</span> detected in the 0.3-8.0 keV band in the merged <span class="hlt">observation</span> or in one of the six individual <span class="hlt">observations</span>; 399 <span class="hlt">sources</span> are located within the D{sub 25} ellipse. The <span class="hlt">observed</span> 0.3-8.0 keV luminosities of these 501 <span class="hlt">sources</span> range from 9.3 Multiplication-Sign 10{sup 36} erg s{sup -1} to 5.4 Multiplication-Sign 10{sup 39} erg s{sup -1}. The 90% detection completeness limit within the D{sub 25} ellipse is 5.5 Multiplication-Sign 10{sup 37} erg s{sup -1}. Based on the surface density of background active galactic nuclei (AGNs) and detection completeness, we expect Almost-Equal-To 45 background AGNs among the catalog <span class="hlt">sources</span> ( Almost-Equal-To 15 within the D{sub 25} ellipse). There are nine <span class="hlt">sources</span> with luminosities greater than 10{sup 39} erg s{sup -1}, which are candidates for ultraluminous X-ray <span class="hlt">sources</span>. The nuclear <span class="hlt">source</span> of NGC 4649 is a low-luminosity AGN, with an intrinsic 2.0-8.0 keV X-ray luminosity of 1.5 Multiplication-Sign 10{sup 38} erg s{sup -1}. The X-ray colors suggest that the majority of the catalog <span class="hlt">sources</span> are low-mass X-ray binaries (LMXBs). We find that 164 of the 501 X-ray <span class="hlt">sources</span> show long-term variability, indicating that they are accreting compact objects. We discover four transient candidates and another four potential transients. We also identify 173 X-ray <span class="hlt">sources</span> (141 within the D{sub 25} ellipse) that are associated with globular clusters (GCs) based on Hubble Space Telescope and ground-based data; these LMXBs tend to be hosted by red GCs. Although NGC 4649 has a much larger population of X-ray <span class="hlt">sources</span> than the structurally similar early-type galaxies, NGC 3379 and NGC 4278, the X-ray <span class="hlt">source</span> properties are comparable in all three systems.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/917735','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/917735"><span>X-Ray <span class="hlt">Observations</span> of Unidentified H.E.S.S. Gamma-Ray <span class="hlt">Sources</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Funk, S.; /SLAC</p> <p>2007-10-10</p> <p>In a survey of the inner part of the Galaxy, performed with the H.E.S.S. Instrument (High energy stereoscopic system) in 2004 and 2005, a large number of new unidentified very high energy (VHE) {gamma}-ray <span class="hlt">sources</span> above an energy of 100 GeV was discovered. Often the {gamma}-ray spectra in these <span class="hlt">sources</span> reach energies of up to {approx} 10 TeV. These are the highest energy particles ever attributed to single astrophysical objects. While a few of these <span class="hlt">sources</span> can be identified at other wavebands, most of these <span class="hlt">sources</span> remain unidentified so far. A positive identification of these new g-ray <span class="hlt">sources</span> with a counterpart object at other wavebands requires (a) a positional coincidence between the two <span class="hlt">sources</span>,( b) a viable {gamma}-ray emission mechanism and (c) a consistent multiwavelength behavior of the two <span class="hlt">sources</span>. X-ray <span class="hlt">observations</span> with satellites such as XMM-Newton, Chandra or Suzaku provide one of the best channels to studying these enigmatic {gamma}-ray <span class="hlt">sources</span> at other wavebands, since they combine high angular resolution and sensitivity with the ability to access non-thermal electrons through their synchrotron emission. We therefore have started a dedicated program to investigate VHE {gamma}-ray <span class="hlt">sources</span> with high-sensitivity X-ray instruments.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/25562705','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/25562705"><span>Full-Sun <span class="hlt">observations</span> for identifying the <span class="hlt">source</span> of the slow solar wind.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Brooks, David H; Ugarte-Urra, Ignacio; Warren, Harry P</p> <p>2015-01-06</p> <p>Fast (>700 km s(-1)) and slow (~400 km s(-1)) winds stream from the Sun, permeate the heliosphere and influence the near-Earth environment. While the fast wind is known to emanate primarily from polar coronal holes, the <span class="hlt">source</span> of the slow wind remains unknown. Here we identify possible sites of origin using a slow solar wind <span class="hlt">source</span> map of the entire Sun, which we construct from specially designed, full-disk <span class="hlt">observations</span> from the Hinode satellite, and a magnetic field model. Our map provides a full-Sun <span class="hlt">observation</span> that combines three key ingredients for identifying the <span class="hlt">sources</span>: velocity, plasma composition and magnetic topology and shows them as solar wind composition plasma outflowing on open magnetic field lines. The area coverage of the identified <span class="hlt">sources</span> is large enough that the sum of their mass contributions can explain a significant fraction of the mass loss rate of the solar wind.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4354106','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4354106"><span>Full-Sun <span class="hlt">observations</span> for identifying the <span class="hlt">source</span> of the slow solar wind</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Brooks, David H.; Ugarte-Urra, Ignacio; Warren, Harry P.</p> <p>2015-01-01</p> <p>Fast (>700 km s−1) and slow (~400 km s−1) winds stream from the Sun, permeate the heliosphere and influence the near-Earth environment. While the fast wind is known to emanate primarily from polar coronal holes, the <span class="hlt">source</span> of the slow wind remains unknown. Here we identify possible sites of origin using a slow solar wind <span class="hlt">source</span> map of the entire Sun, which we construct from specially designed, full-disk <span class="hlt">observations</span> from the Hinode satellite, and a magnetic field model. Our map provides a full-Sun <span class="hlt">observation</span> that combines three key ingredients for identifying the <span class="hlt">sources</span>: velocity, plasma composition and magnetic topology and shows them as solar wind composition plasma outflowing on open magnetic field lines. The area coverage of the identified <span class="hlt">sources</span> is large enough that the sum of their mass contributions can explain a significant fraction of the mass loss rate of the solar wind. PMID:25562705</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013ApJS..208...25T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013ApJS..208...25T"><span>Multiband Diagnostics of Unidentified 1FGL <span class="hlt">Sources</span> with Suzaku and Swift X-Ray <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Takeuchi, Y.; Kataoka, J.; Maeda, K.; Takahashi, Y.; Nakamori, T.; Tahara, M.</p> <p>2013-10-01</p> <p>We have analyzed all the archival X-ray data of 134 unidentified (unID) gamma-ray <span class="hlt">sources</span> listed in the first Fermi/LAT (1FGL) catalog and subsequently followed up by the Swift/XRT. We constructed the spectral energy distributions (SEDs) from radio to gamma-rays for each X-ray <span class="hlt">source</span> detected, and tried to pick up unique objects that display anomalous spectral signatures. In these analyses, we target all the 1FGL unID <span class="hlt">sources</span>, using updated data from the second Fermi/LAT (2FGL) catalog on the Large Area Telescope (LAT) position and spectra. We found several potentially interesting objects, particularly three <span class="hlt">sources</span>, 1FGL J0022.2-1850, 1FGL J0038.0+1236, and 1FGL J0157.0-5259, which were then more deeply <span class="hlt">observed</span> with Suzaku as a part of an AO-7 program in 2012. We successfully detected an X-ray counterpart for each <span class="hlt">source</span> whose X-ray spectra were well fitted by a single power-law function. The positional coincidence with a bright radio counterpart (currently identified as an active galactic nucleus, AGN) in the 2FGL error circles suggests these <span class="hlt">sources</span> are definitely the X-ray emission from the same AGN, but their SEDs show a wide variety of behavior. In particular, the SED of 1FGL J0038.0+1236 is not easily explained by conventional emission models of blazars. The <span class="hlt">source</span> 1FGL J0022.2-1850 may be in a transition state between a low-frequency peaked and a high-frequency peaked BL Lac object, and 1FGL J0157.0-5259 could be a rare kind of extreme blazar. We discuss the possible nature of these three <span class="hlt">sources</span> <span class="hlt">observed</span> with Suzaku, together with the X-ray identification results and SEDs of all 134 <span class="hlt">sources</span> <span class="hlt">observed</span> with the Swift/XRT.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19870029334&hterms=landau&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dlandau','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19870029334&hterms=landau&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dlandau"><span>Active extragalactic <span class="hlt">sources</span> - Nearly simultaneous <span class="hlt">observations</span> from 20 centimeters to 1400 A</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Landau, R.; Golisch, B.; Jones, T. J.; Jones, T. W.; Pedelty, J.; Rudnick, L.; Sitko, M. L.; Kenney, J.; Roellig, T.; Salonen, E.</p> <p>1986-01-01</p> <p>IRAS, IUE, and ground-based optical, NIR, mm and submm, and radio <span class="hlt">observations</span> obtained mainly on Apr. 9-23, 1983, are reported for 19 active extragalactic <span class="hlt">sources</span> and eight control <span class="hlt">sources</span>. The overall spectra of the compact active <span class="hlt">sources</span> are shown to be well represented by continuous-curvature functions such as parabolas. The spectra are found to be consistent with models involving continuous particle injection (with synchrotron losses) or first-order Fermi acceleration (with escape and synchrotron losses), but not with models using relativistic Maxwellian electron distributions.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19900049524&hterms=primary+source&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dprimary%2Bsource','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19900049524&hterms=primary+source&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dprimary%2Bsource"><span>Evidence for halo-like radio <span class="hlt">sources</span> from kilometric type III burst <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Reiner, M. J.; Stone, R. G.</p> <p>1990-01-01</p> <p>The radio azimuths for many kilometric type III bursts that originate near or behind the limb of the sun are <span class="hlt">observed</span> to drift far to the east or far to the west of the spacecraft-sun line. It is shown that the behavior of the <span class="hlt">observed</span> burst parameters for these events corresponds to the response of a spinning dipole antenna to halolike <span class="hlt">sources</span> of radiation around the sun. These results provide evidence for a previous suggestion that behind-the-limb type III events should appear as halolike <span class="hlt">sources</span> of radiation to an <span class="hlt">observer</span> on the opposite side of the sun, due to scattering of the radiation from the primary <span class="hlt">source</span> back around the sun.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016AN....337..159T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016AN....337..159T"><span>The impact of compact radio <span class="hlt">sources</span> on their host galaxies: <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tadhunter, C.</p> <p>2016-02-01</p> <p>I review the <span class="hlt">observational</span> evidence that CSS/GPS radio <span class="hlt">sources</span> have a significant impact on the evolution of their host galaxies, particularly on the kpc-scales of the galaxy bulges. Starting with an overview of the <span class="hlt">observational</span> evidence for jet-cloud interactions and warm ionised outflows in CSS/GPS <span class="hlt">sources</span>, I then consider the challenges involved in quantifying the feedback effect of the warm outflows in terms of their mass outflow rates and kinetic powers. For the best-<span class="hlt">observed</span> cases it is shown that the warm outflows may have a major negative feedback effect in the very central regions, but probably lack the power to heat and eject the full cool ISM contents of the host galaxies. In contrast, the recently-discovered neutral and molecular outflows are more massive and powerful and therefore carry more destructive potential. However, the feedback effect of such outflows is not necessarily negative: there is now clear <span class="hlt">observational</span> evidence that the molecular outflows are formed as the hot, compressed gas cools behind fast shocks driven into the ISM by the relativistic jets. The natural endpoint of this process is the formation of stars. Therefore, jet-induced star formation may be a significant process in CSS/GPS radio galaxies. Finally, I discuss whether CSS/GPS <span class="hlt">sources</span> are ``imposters'' in flux-limited radio samples, due the flux boosting of the radio <span class="hlt">sources</span> by strong jet-cloud interactions in the early stages of radio <span class="hlt">source</span> evolution.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014EGUGA..16.2446E','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014EGUGA..16.2446E"><span>Complex monitoring and alert network for electromagnetic, <span class="hlt">infrasound</span>, acoustic seismotectonic phenomena</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>-Emilian Toader, Victorin; Moldovan, Iren-Adelina; Constantin, Ionescu</p> <p>2014-05-01</p> <p>The Romanian seismicity recorded in 2013 three important events: the largest seismic "silence", the shortest sequence of two earthquakes greater than 4.8R in less than 14 days after the "Romanian National Institute for Earth Physics" (NIEP) developed a digital network, and a very high crustal activity in Galati area. We analyze the variations of the telluric currents and local magnetic field, variations of the atmospheric electrostatic field, <span class="hlt">infrasound</span>, temperature, humidity, wind speed and direction, atmospheric pressure, variations in the earth crust with inclinometers and animal behavior. The general effect is the first high seismic energy discontinuity that could be a precursor factor. Since 1977 Romania did not register any important earthquake that would generate a sense of fear among the population. In parallel with the seismic network NIEP developed a magneto-telluric, bioseismic, VLF and acoustic network. A large frequency spectrum is covered for mechanical vibration, magnetic and electric field with ground and air sensors. Special software was designed for acquisition, analysis and real time alert using internet direct connection, web page, email and SMS. Many examples show the sensitivity of telluric current, <span class="hlt">infrasound</span>, acoustic records (from air-ground), and the effect of tectonic stress on the magnetic field or ground deformation. The next update of the multidisciplinary monitoring network will include measurement of ionization, radon emission, sky color, solar radiation and extension of <span class="hlt">infrasound</span> and VL/LF equipment. NOAA Space Weather satellites transmit solar activity magnetic field data, X ray flux, electron, and proton flux information useful for complex analysis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017A%26A...600A..93F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017A%26A...600A..93F"><span>Star formation towards the Galactic H II region RCW 120. Herschel <span class="hlt">observations</span> of compact <span class="hlt">sources</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Figueira, M.; Zavagno, A.; Deharveng, L.; Russeil, D.; Anderson, L. D.; Men'shchikov, A.; Schneider, N.; Hill, T.; Motte, F.; Mège, P.; LeLeu, G.; Roussel, H.; Bernard, J.-P.; Traficante, A.; Paradis, D.; Tigé, J.; André, P.; Bontemps, S.; Abergel, A.</p> <p>2017-04-01</p> <p>Context. The expansion of H ii regions can trigger the formation of stars. An overdensity of young stellar objects is <span class="hlt">observed</span> at the edges of H ii regions but the mechanisms that give rise to this phenomenon are not clearly identified. Moreover, it is difficult to establish a causal link between H ii -region expansion and the star formation <span class="hlt">observed</span> at the edges of these regions. A clear age gradient <span class="hlt">observed</span> in the spatial distribution of young <span class="hlt">sources</span> in the surrounding might be a strong argument in favor of triggering. Aims: We aim to characterize the star formation <span class="hlt">observed</span> at the edges of H ii regions by studying the properties of young stars that form there. We aim to detect young <span class="hlt">sources</span>, derive their properties and their evolution stage in order to discuss the possible causal link between the first-generation massive stars that form the H ii region and the young <span class="hlt">sources</span> <span class="hlt">observed</span> at their edges. Methods: We have <span class="hlt">observed</span> the Galactic H ii region RCW 120 with Herschel PACS and SPIRE photometers at 70, 100, 160, 250, 350 and 500 μm. We produced temperature and H2 column density maps and use the getsources algorithm to detect compact <span class="hlt">sources</span> and measure their fluxes at Herschel wavelengths. We have complemented these fluxes with existing infrared data. Fitting their spectral energy distributions with a modified blackbody model, we derived their envelope dust temperature and envelope mass. We computed their bolometric luminosities and discuss their evolutionary stages. Results: The overall temperatures of the region (without background subtraction) range from 15 K to 24 K. The warmest regions are <span class="hlt">observed</span> towards the ionized gas. The coldest regions are <span class="hlt">observed</span> outside the ionized gas and follow the emission of the cold material previously detected at 870 μm and 1.3 mm. The H2 column density map reveals the distribution of the cold medium to be organized in filaments and highly structured. Column densities range from 7 × 1021 cm-2 up to 9 × 1023 cm-2</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005A%26AT...24..421D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005A%26AT...24..421D"><span><span class="hlt">Observations</span> of the power cosmic radio <span class="hlt">sources</span> on the radio telescope URAN-4 during 1998 2004</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Derevyagin, V. G.; Isaeva, E. A.; Kravetz, R. O.; Litvinenko, O. A.; Panishko, S. K.</p> <p>2005-10-01</p> <p>To investigate the variability of the flux density, <span class="hlt">observations</span> of four power radio <span class="hlt">sources</span> (3C144, 3C274, 3C405 and 3C461) were carried out on the radio telescope URAN-4 at two frequencies, 20 and 25MHz, during 1998 2005. The automatic procedure for obtaining the <span class="hlt">observations</span> is considered briefly in this paper. The results of previous procedures are presented in the tables. They contained information that allows the vast amount of material that has been gathered to be analysed in more detail as follows: estimation of the <span class="hlt">source</span> flux densities, study of ionospheric scintillations, investigation of the dependence of the direction pattern on the hour angle and the solving of other tasks. The dependence of the URAN-4 direction pattern on the hour angle is cited as an example of the mean procedure using many <span class="hlt">observation</span> data. Long-time <span class="hlt">observation</span> series allowed the cycle year dependence of the ionospheric scintillation index to be obtained.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.9450P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.9450P"><span>On the use of <span class="hlt">infrasound</span> sensors for low frequency atmospheric studies</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ponceau, Damien; Marty, Julien; Koenig, Jean-Marc; Denis, Stéphane; Ulziibat, Munkhuu</p> <p>2010-05-01</p> <p>Most of infrasonic stations from International Monitoring System (IMS) of the Comprehensive Nuclear Test Organization (CTBTO) use absolute <span class="hlt">infrasound</span> sensors associated with acquisition units dedicated to geophysics. These sensors measure ambient atmospheric pressure over a frequency bandwidth from DC to tens of Hz, including the entire <span class="hlt">infrasound</span> frequency range. The reference cavity vacuum gives them an intrinsic thermal sensitivity much lower than that of differential <span class="hlt">infrasound</span> sensors such as microphones. Experience shows that this is especially interesting when low frequency pressure measurements are needed. Direct digitizing of such signals requires a dynamic range better than 145 dB over the frequency bandwidth of interest. Microbarometers were equipped with an additional output attenuating the very low frequencies with a simple first order high pass filter with a cutoff frequency of 0.01 Hz and a gain over its bandwidth of 20. This output has a dynamic range of about 108 dB easier to digitize. It is made from electronic components selected for their accuracy, their stability and insensitivity to environment. This is the "filtered output" which is generally used on the IMS. More and more scientific studies for civilian applications focus on low frequency signals affected by this filtering. This presentation discusses how the use of this filtered output affects data quality in this frequency range and how it is possible to exploit them. Microbarometer output stage has been modeled to estimate the noise induced by filtering and its influence on the infrasonic signals of interest. This presentation discusses how it is possible to compensate filter's influence to recover the "true" signals of interest. It explains how the operating principle of these sensors can minimize errors. Three stations consisting in four sensors were set up in Mongolia in order to record pressure variations produced by the total solar eclipse of the 1 August 2008. For each sensor, the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/7036139','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/7036139"><span>Stereoscopic <span class="hlt">observations</span> of a solar flare hard X-ray <span class="hlt">source</span> in the high corona</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Kane, S.R.; Mctiernan, J.; Loran, J.; Fenimore, E.E.; Klebesadel, R.W.; Laros, J.G. Los Alamos National Laboratory, NM )</p> <p>1992-05-01</p> <p>The vertical structure of the impulsive and gradual hard X-ray <span class="hlt">sources</span> in high coronae and the characteristics of the impulsive soft X-ray emission are investigated on the basis of PVE, ICE, and GOES <span class="hlt">observations</span> of the energetic flare on February 16, 1984. The average photon spectra <span class="hlt">observed</span> by these instruments during the impulsive and gradual hard X-ray bursts are summarized. A comparison of these unocculted and partially occulted spectra shows that the <span class="hlt">sources</span> of the impulsive hard X-ray (greater than about 25 keV) and impulsive soft X-ray (2-5 keV) emissions in this flare extended to coronal altitudes greater than about 200,000 km above the photosphere. At about 100 keV, the ratio of the coronal <span class="hlt">source</span> brightness to the total <span class="hlt">source</span> brightness was 0.001 during the impulsive phase and less than about 0.01 during the gradual hard X-ray burst. The <span class="hlt">sources</span> of the gradual hard X-ray burst and gradual soft X-ray burst were almost completely occulted, indicating that these <span class="hlt">sources</span> were located at heights less than 200,000 km above the photosphere. 47 refs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780059335&hterms=gums&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dgums','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780059335&hterms=gums&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D80%26Ntt%3Dgums"><span><span class="hlt">Observations</span> of low-luminosity X-ray <span class="hlt">sources</span> in Vela-Puppis</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pravdo, S. H.; Becker, R. H.; Boldt, E. A.; Holt, S. S.; Serlemitsos, P. J.; Swank, J. H.</p> <p>1978-01-01</p> <p>Results are presented for a study of the X-ray emission from a small portion of the galactic plane near galactic longitude 260 deg. This region contains at least six low-luminosity X-ray <span class="hlt">sources</span> within about 10 deg of PSR 0833-45, which is near the center of the Gum nebula. The X-ray <span class="hlt">source</span> 4U 0833-45, associated with the Vela pulsar, is <span class="hlt">observed</span> at twice its 4U catalog intensity. The lack of X-ray pulsations at the pulsar period (greater than 99% nonpulsed), the nonthermal power-law spectrum, and models of the X-ray <span class="hlt">source</span> distribution in this region suggest that a large fraction of the X-rays come from an extended <span class="hlt">source</span> about 1 deg of arc in radius. The <span class="hlt">observation</span> of a high-temperature (effective temperature at least 100 million K) spectrum in a field of view containing only Puppis A among known <span class="hlt">sources</span> has led to the discovery of new OSO 8 <span class="hlt">source</span>, OS 0752-39. Other spectra from this region are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014ACP....1412133D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014ACP....1412133D"><span>Characteristics and <span class="hlt">sources</span> of gravity waves <span class="hlt">observed</span> in noctilucent cloud over Norway</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Demissie, T. D.; Espy, P. J.; Kleinknecht, N. H.; Hatlen, M.; Kaifler, N.; Baumgarten, G.</p> <p>2014-11-01</p> <p>Four years of noctilucent cloud (NLC) images from an automated digital camera in Trondheim and results from a ray-tracing model are used to extend the climatology of gravity waves to higher latitudes and to identify their <span class="hlt">sources</span> during summertime. The climatology of the summertime gravity waves detected in NLC between 64 and 74° N is similar to that <span class="hlt">observed</span> between 60 and 64° N by Pautet et al. (2011). The direction of propagation of gravity waves <span class="hlt">observed</span> in the NLC north of 64° N is a continuation of the north and northeast propagation as <span class="hlt">observed</span> in south of 64° N. However, a unique population of fast, short wavelength waves propagating towards the SW is <span class="hlt">observed</span> in the NLC, which is consistent with transverse instabilities generated in situ by breaking gravity waves (Fritts and Alexander, 2003). The relative amplitude of the waves <span class="hlt">observed</span> in the NLC Mie scatter have been combined with ray-tracing results to show that waves propagating from near the tropopause, rather than those resulting from secondary generation in the stratosphere or mesosphere, are more likely to be the <span class="hlt">sources</span> of the prominent wave structures <span class="hlt">observed</span> in the NLC. The coastal region of Norway along the latitude of 70° N is identified as the primary <span class="hlt">source</span> region of the waves generated near the tropopause.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2001AtmEn..35.2507R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2001AtmEn..35.2507R"><span>Estimating <span class="hlt">source</span> regions of European emissions of trace gases from <span class="hlt">observations</span> at Mace Head</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ryall, D. B.; Derwent, R. G.; Manning, A. J.; Simmonds, P. G.; O'Doherty, S.</p> <p></p> <p>A technique is described for identifying probable <span class="hlt">source</span> locations for a range of greenhouse and ozone-depleting trace gases from the long-term measurements made at Mace Head, Ireland. The Met. Office's dispersion model NAME is used to predict concentrations at Mace Head from all possible <span class="hlt">sources</span> in Europe, then <span class="hlt">source</span> regions identified as those which consistently lead to elevated concentrations at Mace Head. Estimates of European emissions and their distribution are presented for a number of trace gases for the period 1995-1998. Estimated emission patterns are realistic, given the nature and varied applications of the species considered. The results indicate that whilst there are limitations, useful information about <span class="hlt">source</span> distribution can be extracted from continuous measurements at a remote site. It is probable that much improved estimates could be derived if <span class="hlt">observations</span> were available from a number of sites. The ability to assess emissions has obvious implications in monitoring compliance with internationally agreed quota and protocols.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19820046851&hterms=observation+spatiale&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dobservation%2Bspatiale','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19820046851&hterms=observation+spatiale&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dobservation%2Bspatiale"><span>Einstein <span class="hlt">observations</span> of the 1978 November 19 gamma ray burst <span class="hlt">source</span> field</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Pizzichini, G.; Cline, T. L.; Desai, U. D.; Mushotzky, R.; Teegarden, B. J.; Evans, W. D.; Klebesadel, R. W.; Laros, J. G.; Barat, C.; Hurley, K.</p> <p>1982-01-01</p> <p>It is pointed out that several years after the discovery of cosmic gamma ray bursts (GRB) their <span class="hlt">sources</span> have not yet been identified, although searches have been conducted in optical, X-ray, and radio wavelengths. The three smallest error boxes are now related to the events of Mar. 5, 1979, Apr. 6, 1979, and Nov. 19, 1978. X-ray <span class="hlt">observations</span>, with the Imaging Proportional Counter (IPC) of the Einstein Observatory, were made for all three locations. A description is presented of the results of the 8200 second IPC <span class="hlt">observation</span> of the Nov. 19, 1978 GRB, made on July 1 and 2, 1980. Three <span class="hlt">sources</span> were detected. However, two of them were outside the GRB error box. The third <span class="hlt">source</span> is located well inside the burst error box.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19770067741&hterms=Lewin&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DA.%2BLewin','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19770067741&hterms=Lewin&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DA.%2BLewin"><span><span class="hlt">Observations</span> of the X-ray burst <span class="hlt">source</span> MXB 1636-53</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hoffman, J. A.; Lewin, W. H. G.; Doty, J.</p> <p>1977-01-01</p> <p>X-ray bursts have been <span class="hlt">observed</span> from MXB 1636-53, almost certainly associated with the strong steady X-ray <span class="hlt">source</span> 2S 1636-536 (Norma X-1, 3U 1636-53). The steady <span class="hlt">source</span> was <span class="hlt">observed</span> in January 1977 at roughly half the intensity reported in the 3U catalog and showed about 15% variability on a time scale of hours. The spectra of the X-ray bursts are well fitted by blackbody radiation whose temperature rises rapidly to a maximum of approximately 28 million K and then cools slowly. If the <span class="hlt">source</span> is at a distance of 10 kpc, the radius of the projected burst emission region is about 10 km, similar to the size of a neutron star.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016JApA...37...27D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016JApA...37...27D"><span>Probing Individual <span class="hlt">Sources</span> during Reionization and Cosmic Dawn using Square Kilometre Array HI 21-cm <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Datta, Kanan K.; Ghara, Raghunath; Majumdar, Suman; Choudhury, T. Roy; Bharadwaj, Somnath; Roy, Himadri; Datta, Abhirup</p> <p>2016-12-01</p> <p>Detection of individual luminous <span class="hlt">sources</span> during the reionization epoch and cosmic dawn through their signatures in the HI 21-cm signal is one of the direct approaches to probe the epoch. Here, we summarize our previous works on this and present preliminary results on the prospects of detecting such <span class="hlt">sources</span> using the SKA1-low experiment. We first discuss the expected HI 21-cm signal around luminous <span class="hlt">sources</span> at different stages of reionization and cosmic dawn. We then introduce two visibility based estimators for detecting such signals: one based on the matched filtering technique and the other relies on simply combing the visibility signal from different baselines and frequency channels. We find that the SKA1-low should be able to detect ionized bubbles of radius Rb ≳ 10 Mpc with ˜100 h of <span class="hlt">observations</span> at redshift z˜8 provided that the mean outside neutral hydrogen fraction x_{ {HI}} ≳ 0.5. We also investigate the possibility of detecting HII regions around known bright QSOs such as around ULASJ1120+0641 discovered by Mortlock et al. ( Nature 474, 7353 (2011)). We find that a 5 σ detection is possible with 600 h of SKA1-low <span class="hlt">observations</span> if the QSO age and the outside xHI are at least ˜2×107 Myr and ˜0.2 respectively. Finally, we investigate the possibility of detecting the very first X-ray and Ly- α <span class="hlt">sources</span> during the cosmic dawn. We consider mini-QSOs like <span class="hlt">sources</span> which emits in X-ray frequency band. We find that with a total ˜ 1000 h of <span class="hlt">observations</span>, SKA1-low should be able to detect those <span class="hlt">sources</span> individually with a ˜ 9 σ significance at redshift z=15. We summarize how the SNR changes with various parameters related to the <span class="hlt">source</span> properties.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015PASJ...67...99J','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015PASJ...67...99J"><span>Structure and <span class="hlt">sources</span> of the sporadic meteor background from video <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Jakšová, Ivana; Porubčan, Vladimír; Klačka, Jozef</p> <p>2015-10-01</p> <p>We investigate and discuss the structure of the sporadic meteor background population in the near-Earth space based on video meteor orbits from the SonotaCo database (SonotaCo 2009, WGN, 37, 55). The selection of the shower meteors was done by the Southworth-Hawkins streams-search criterion (Southworth & Hawkins 1963, Smithson. Contr. Astrophys., 7, 261). Of a total of 117786 orbits, 69.34% were assigned to sporadic background meteors. Our analysis revealed all the known sporadic <span class="hlt">sources</span>, such as the dominant apex <span class="hlt">source</span> which is splitting into the northern and southern branch. Part of a denser ring structure about the apex <span class="hlt">source</span> connecting the antihelion and north toroidal <span class="hlt">sources</span> is also evident. We showed that the annual activity of the apex <span class="hlt">source</span> is similar to the annual variation in activity of the whole sporadic background. The antihelion <span class="hlt">source</span> exhibits a very broad maximum from July until January and the north toroidal <span class="hlt">source</span> shows three maxima similar to the radar <span class="hlt">observations</span> by the Canadian Meteor Orbit Radar (CMOR). Potential parent bodies of the sporadic population were searched for by comparison of the distributions of the orbital elements of sporadic meteors, minor planets and comets.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_14");'>14</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li class="active"><span>16</span></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_16 --> <div id="page_17" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="321"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19850026635','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19850026635"><span>Advanced techniques for high resolution spectroscopic <span class="hlt">observations</span> of cosmic gamma-ray <span class="hlt">sources</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Matteson, J. L.; Pelling, M. R.; Peterson, L. E.; Lin, R. P.; Anderson, K. A.; Pehl, R. H.; Hurley, K. C.; Vedrenne, G.; Sniel, M.; Durouchoux, P.</p> <p>1985-01-01</p> <p>An advanced gamma-ray spectrometer that is currently in development is described. It will obtain a sensitivity of 0.0001 ph/sq cm./sec in a 6 hour balloon <span class="hlt">observation</span> and uses innovative techniques for background reduction and <span class="hlt">source</span> imaging.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://eric.ed.gov/?q=reinforcement&pg=3&id=EJ1062576','ERIC'); return false;" href="http://eric.ed.gov/?q=reinforcement&pg=3&id=EJ1062576"><span>Is the <span class="hlt">Source</span> of Reinforcement for Naming Multiple Conditioned Reinforcers for <span class="hlt">Observing</span> Responses?</span></a></p> <p><a target="_blank" href="http://www.eric.ed.gov/ERICWebPortal/search/extended.jsp?_pageLabel=advanced">ERIC Educational Resources Information Center</a></p> <p>Longano, Jennifer M.; Greer, R. Douglas</p> <p>2015-01-01</p> <p>Naming refers to the incidental acquisition of word-object relations as listener and speaker without explicit reinforcement. To investigate possible <span class="hlt">sources</span> of reinforcement for naming, we examined the effects of a procedure for conditioning reinforcement for <span class="hlt">observing</span> responses on the emergence of naming in children who previously lacked it. The…</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A23J..03F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A23J..03F"><span>Constraining the <span class="hlt">Sources</span> and Sinks of Atmospheric Methane Using Stable Isotope <span class="hlt">Observations</span> and Chemistry Climate Modeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Feinberg, A.; Coulon, A.; Stenke, A.; Peter, T.</p> <p>2015-12-01</p> <p>Methane acts as both a greenhouse gas and a driver of atmospheric chemistry. There is a lack of consensus for the explanation behind the atmospheric methane trend in recent years (1980-2010). High uncertainties are associated with the magnitudes of individual methane <span class="hlt">source</span> and sink processes. Methane isotopes have the potential to distinguish between the different methane fluxes, as each flux is characterized by an isotopic signature. Methane emissions from each <span class="hlt">source</span> category are expressed explicitly in a chemistry climate model SOCOL, including wetlands, rice paddies, biomass burning, industry, etc. The model includes 48 methane tracers based on <span class="hlt">source</span> type and geographical origin in order to track methane after it has been emitted. SOCOL simulations for the years 1980-2010 are performed in "nudged mode", so that model dynamics reflect <span class="hlt">observed</span> meteorology. Available database estimates of the various surface emission fluxes are inputted into SOCOL. The model diagnostic methane tracers are compared to methane isotope <span class="hlt">observations</span> from measurement networks. Inconsistencies between the model results and <span class="hlt">observations</span> point to deficiencies in the available emission estimates or model sink processes. Because of their dependence on the OH sink, deuterated methane <span class="hlt">observations</span> and methyl chloroform tracers are used to investigate the variability of OH mixing ratios in the model and the real world. The analysis examines the validity of the methane <span class="hlt">source</span> and sink category estimates over the last 30 years.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...832..190Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...832..190Z"><span>Radio <span class="hlt">Sources</span> in the NCP Region <span class="hlt">Observed</span> with the 21 Centimeter Array</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zheng, Qian; Wu, Xiang-Ping; Johnston-Hollitt, Melanie; Gu, Jun-hua; Xu, Haiguang</p> <p>2016-12-01</p> <p>We present a catalog of 624 radio <span class="hlt">sources</span> detected around the North Celestial Pole (NCP) with the 21 Centimeter Array (21CMA), a radio interferometer dedicated to the statistical measurement of the epoch of reionization (EoR). The data are taken from a 12 hr <span class="hlt">observation</span> made on 2013 April 13, with a frequency coverage from 75 to 175 MHz and an angular resolution of ˜4‧. The catalog includes flux densities at eight sub-bands across the 21CMA bandwidth and provides the in-band spectral indices for the detected <span class="hlt">sources</span>. To reduce the complexity of interferometric imaging from the so-called “w” term and ionospheric effects, the present analysis is restricted to the east-west baselines within 1500 m only. The 624 radio <span class="hlt">sources</span> are found within 5° around the NCP down to ˜0.1 Jy. Our <span class="hlt">source</span> counts are compared, and also exhibit a good agreement, with deep low-frequency <span class="hlt">observations</span> made recently with the GMRT and MWA. In particular, for fainter radio <span class="hlt">sources</span> below ˜1 Jy, we find a flattening trend of <span class="hlt">source</span> counts toward lower frequencies. While the thermal noise (˜0.4 mJy) is well controlled to below the confusion limit, the dynamical range (˜104) and sensitivity of current 21CMA imaging are largely limited by calibration and deconvolution errors, especially the grating lobes of very bright <span class="hlt">sources</span>, such as 3C061.1, in the NCP field, which result from the regular spacings of the 21CMA. We note that particular attention should be paid to the extended <span class="hlt">sources</span>, and their modeling and removal may constitute a large technical challenge for current EoR experiments. Our analysis may serve as a useful guide to the design of next generation low-frequency interferometers like the Square Kilometre Array.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMSM23A2207G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMSM23A2207G"><span>Determination of <span class="hlt">Source</span> Hemisphere of Auroral Kilometric Radiation (AKR) <span class="hlt">observed</span> by KAGUYA</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Goto, Y.; Uda, K.; Kasahara, Y.; Hashimoto, K.</p> <p>2013-12-01</p> <p>The auroral kilometric radiation (AKR) were <span class="hlt">observed</span> with a plasma wave receiver called WFC (waveform capture) [1] onboard the lunar orbiter KAGUYA during the whole mission period (2007-2009). It is well-known that the AKR is dominated by right-handed mode wave with small contribution of left-handed one. Investigation of <span class="hlt">observation</span> conditions of each mode wave is still an interesting subject associated with AKR generation and propagation characteristics. A problem in the AKR polarization analysis is that the relation between the <span class="hlt">source</span> polarization and the <span class="hlt">observed</span> polarization depends on the <span class="hlt">source</span> hemisphere. Because the WFC measured only two orthogonal electric field components, wave normal vectors of the AKR cannot be determined from the measurements. A simple way to determine the <span class="hlt">source</span> hemisphere is to examine whether AKR is <span class="hlt">observed</span> when the polar region of one hemisphere is seen and that of the other is shadowed by the Moon. However, its usable conditions are limited. In this study, we used a new technique to determine the <span class="hlt">source</span> hemisphere of the <span class="hlt">observed</span> AKR. Because the KAGUYA orbits around the moon in two-hour periods, the log-ratio of the two measured electric fields of the AKR has a clear sinusoidal time variation with the two-hour periodicity. The phase of the variation depends on the <span class="hlt">source</span> location. For example, the times when the log-ratio becomes zero are several minutes different in two cases: the AKR <span class="hlt">sources</span> exist in the north and south polar regions, respectively. Since the time resolution of the WFC measurements were 0.5 - 8 seconds, it is not difficult to determine the phase of the sinusoidal variations. Using the technique, the <span class="hlt">source</span> hemispheres of the AKR were determined even when the AKR from the both hemispheres had been simultaneously <span class="hlt">observed</span>. The statistical characteristic of the AKR polarization will be discussed. [1] Y. Kasahara, Y. Goto, K. Hashimoto, T. Imachi, A. Kumamoto, T. Ono, and H. Matsumoto, Plasma Wave <span class="hlt">Observation</span> Using</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19900003472','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19900003472"><span>A statistical study of radio-<span class="hlt">source</span> structure effects on astrometric very long baseline interferometry <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Ulvestad, J. S.</p> <p>1989-01-01</p> <p>Errors from a number of <span class="hlt">sources</span> in astrometric very long baseline interferometry (VLBI) have been reduced in recent years through a variety of methods of calibration and modeling. Such reductions have led to a situation in which the extended structure of the natural radio <span class="hlt">sources</span> used in VLBI is a significant error <span class="hlt">source</span> in the effort to improve the accuracy of the radio reference frame. In the past, work has been done on individual radio <span class="hlt">sources</span> to establish the magnitude of the errors caused by their particular structures. The results of calculations on 26 radio <span class="hlt">sources</span> are reported in which an effort is made to determine the typical delay and delay-rate errors for a number of <span class="hlt">sources</span> having different types of structure. It is found that for single <span class="hlt">observations</span> of the types of radio <span class="hlt">sources</span> present in astrometric catalogs, group-delay and phase-delay scatter in the 50 to 100 psec range due to <span class="hlt">source</span> structure can be expected at 8.4 GHz on the intercontinental baselines available in the Deep Space Network (DSN). Delay-rate scatter of approx. 5 x 10(exp -15) sec sec(exp -1) (or approx. 0.002 mm sec (exp -1) is also expected. If such errors mapped directly into <span class="hlt">source</span> position errors, they would correspond to position uncertainties of approx. 2 to 5 nrad, similar to the best position determinations in the current JPL VLBI catalog. With the advent of wider bandwidth VLBI systems on the large DSN antennas, the system noise will be low enough so that the structure-induced errors will be a significant part of the error budget. Several possibilities for reducing the structure errors are discussed briefly, although it is likely that considerable effort will have to be devoted to the structure problem in order to reduce the typical error by a factor of two or more.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920030109&hterms=Matthew+Robinson&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DMatthew%2BRobinson','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920030109&hterms=Matthew+Robinson&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D10%26Ntt%3DMatthew%2BRobinson"><span>Near-infrared <span class="hlt">observations</span> of the z about 2.3 IRAS <span class="hlt">source</span> FSC 10214 + 4724</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Soifer, B. T.; Neugebauer, G.; Graham, J. R.; Matthews, K.; Mazzarella, J. M.; Lonsdale, C. J.; Rowan-Robinson, M.; Broadhurst, T.; Lawrence, A.; Mcmahon, R.</p> <p>1991-01-01</p> <p>Near-infrared imaging and spectroscopy of the extremely luminous IRAS <span class="hlt">source</span> FSC 10214 + 4724 have been obtained using the Cassegrain infrared camera on the 200-inch Hale Telescope. A low-resolution spectrum in the 2.0-2.4 micron atmospheric window shows a very strong H-alpha line at the optically determined redshift z = 2.286. The <span class="hlt">observed</span> rest-frame equivalent width of H-alpha is 0.07 +/-0.02 microns, consistent with the largest values found in quasars. The images show an unresolved <span class="hlt">source</span>, while the near-infrared colors are somewhat redder than the mean colors of quasars <span class="hlt">observed</span> at the same redshift. The reddening inferred is about 1.5 mag, with an upper limit of about 3.0 mag. If FSC 10214 + 4724 is a quasar, the reddening-corrected bolometric luminosity is approximately equal to the <span class="hlt">observed</span> infrared luminosity.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MNRAS.463.2997M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MNRAS.463.2997M"><span>The Lockman Hole project: LOFAR <span class="hlt">observations</span> and spectral index properties of low-frequency radio <span class="hlt">sources</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mahony, E. K.; Morganti, R.; Prandoni, I.; van Bemmel, I. M.; Shimwell, T. W.; Brienza, M.; Best, P. N.; Brüggen, M.; Calistro Rivera, G.; de Gasperin, F.; Hardcastle, M. J.; Harwood, J. J.; Heald, G.; Jarvis, M. J.; Mandal, S.; Miley, G. K.; Retana-Montenegro, E.; Röttgering, H. J. A.; Sabater, J.; Tasse, C.; van Velzen, S.; van Weeren, R. J.; Williams, W. L.; White, G. J.</p> <p>2016-12-01</p> <p>The Lockman Hole is a well-studied extragalactic field with extensive multi-band ancillary data covering a wide range in frequency, essential for characterizing the physical and evolutionary properties of the various <span class="hlt">source</span> populations detected in deep radio fields (mainly star-forming galaxies and AGNs). In this paper, we present new 150-MHz <span class="hlt">observations</span> carried out with the LOw-Frequency ARray (LOFAR), allowing us to explore a new spectral window for the faint radio <span class="hlt">source</span> population. This 150-MHz image covers an area of 34.7 square degrees with a resolution of 18.6 × 14.7 arcsec and reaches an rms of 160 μJy beam-1 at the centre of the field. As expected for a low-frequency selected sample, the vast majority of <span class="hlt">sources</span> exhibit steep spectra, with a median spectral index of α _{150}^{1400}=-0.78± 0.015. The median spectral index becomes slightly flatter (increasing from α _{150}^{1400}=-0.84 to α _{150}^{1400}=-0.75) with decreasing flux density down to S150 ˜10 mJy before flattening out and remaining constant below this flux level. For a bright subset of the 150-MHz selected sample, we can trace the spectral properties down to lower frequencies using 60-MHz LOFAR <span class="hlt">observations</span>, finding tentative evidence for <span class="hlt">sources</span> to become flatter in spectrum between 60 and 150 MHz. Using the deep, multi-frequency data available in the Lockman Hole, we identify a sample of 100 ultra-steep-spectrum <span class="hlt">sources</span> and 13 peaked-spectrum <span class="hlt">sources</span>. We estimate that up to 21 per cent of these could have z > 4 and are candidate high-z radio galaxies, but further follow-up <span class="hlt">observations</span> are required to confirm the physical nature of these objects.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910058127&hterms=archetypal&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Darchetypal','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910058127&hterms=archetypal&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Darchetypal"><span>Multifrequency VLA <span class="hlt">observations</span> of PKS 0745 - 191 - The archetypal 'cooling flow' radio <span class="hlt">source</span>?</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Baum, S. A.; O'Dea, C. P.</p> <p>1991-01-01</p> <p>Ninety-, 20-, 6- and 2-cm VLA <span class="hlt">observations</span> of the high-radio-luminosity cooling-flow radio <span class="hlt">source</span> PKS 0745 - 191 are presented. The radio <span class="hlt">source</span> was found to have a core with a very steep spectrum (alpha is approximately -1.5) and diffuse emission with an even steeper spectrum (alpha is approximately -1.5 to -2.3) without clear indications of the jets, hotspots, or double lobes found in the other radio <span class="hlt">sources</span> of comparable luminosity. It is inferred that the energy to power the radio <span class="hlt">source</span> comes from the central engine, but the <span class="hlt">source</span>'s structure may be heavily influenced by the past history of the galaxy and the inflowing intracluster medium. It is shown that, while the radio <span class="hlt">source</span> is energetically unimportant for the cluster as a whole, it is important on the scale of the cooling flow. The mere existence of cosmic rays and magnetic fields within a substantial fraction of the volume inside the cooling radius has important consequences for cooling-flow models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1991MNRAS.250..737B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1991MNRAS.250..737B"><span>Multifrequency VLA <span class="hlt">observations</span> of PKS 0745 - 191 - The archetypal 'cooling flow' radio <span class="hlt">source</span>?</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Baum, S. A.; O'Dea, C. P.</p> <p>1991-06-01</p> <p>Ninety-, 20-, 6- and 2-cm VLA <span class="hlt">observations</span> of the high-radio-luminosity cooling-flow radio <span class="hlt">source</span> PKS 0745 - 191 are presented. The radio <span class="hlt">source</span> was found to have a core with a very steep spectrum (alpha is approximately -1.5) and diffuse emission with an even steeper spectrum (alpha is approximately -1.5 to -2.3) without clear indications of the jets, hotspots, or double lobes found in the other radio <span class="hlt">sources</span> of comparable luminosity. It is inferred that the energy to power the radio <span class="hlt">source</span> comes from the central engine, but the <span class="hlt">source</span>'s structure may be heavily influenced by the past history of the galaxy and the inflowing intracluster medium. It is shown that, while the radio <span class="hlt">source</span> is energetically unimportant for the cluster as a whole, it is important on the scale of the cooling flow. The mere existence of cosmic rays and magnetic fields within a substantial fraction of the volume inside the cooling radius has important consequences for cooling-flow models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030022790','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030022790"><span>Chandra <span class="hlt">Observation</span> of the X-ray <span class="hlt">Source</span> Population of NGC 6946</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Holt, S. S.; Schlegel, E. M.; Hwang, U.; Petre, R.</p> <p>2003-01-01</p> <p>We present the results of a study of discrete X-ray <span class="hlt">sources</span> in NGC 6946 using a deep Chandra ACIS <span class="hlt">observation</span>. Based on the slope of the log N-log S distribution and the general correlation of <span class="hlt">sources</span> with the spiral arms, we infer that the overall discrete <span class="hlt">source</span> sample in NGC 6946 is dominated by high mass X-ray binaries, in contrast to the <span class="hlt">source</span> distributions in M31 and the Milky Way. This is consistent with the higher star formation rate in NGC 6946 than in those galaxies. We find that the strong X-ray <span class="hlt">sources</span> in the region of the galactic center do not correlate in detail with images of the region in the near-IR, although one of them may be coincident with the galactic center. The non-central ultra-luminous X-ray <span class="hlt">source</span> in NGC 6946, previously identified with a supernova remnant, has an X-ray spectrum and luminosity that is inconsistent with either a traditional pulsar wind nebula or a blast wave remnant.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19760018969&hterms=college+board&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dcollege%2Bboard','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19760018969&hterms=college+board&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D50%26Ntt%3Dcollege%2Bboard"><span>Copernicus <span class="hlt">observations</span> of a number of galactic X-ray <span class="hlt">sources</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Culhane, J. L.; Mason, K. O.; Sanford, P. W.; White, N. E.</p> <p>1976-01-01</p> <p>The Copernicus satellite was launched on 21 August 1972. The main experiment on board is the University of Princeton UV telescope. In addition a cosmic X-ray package of somewhat modest aperture was provided by the Mullard Space Science Laboratory (MSSL) of University College London. Following a brief description of the instrument, a list of galactic <span class="hlt">sources</span> <span class="hlt">observed</span> during the year is presented. Although the X-ray detection aperture is small, the ability to point the satellite for long periods of time with high accuracy makes Copernicus an ideal vehicle for the study of variable <span class="hlt">sources</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA564065','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA564065"><span><span class="hlt">Infrasound</span> Studies for Yield Estimation of HE Explosions</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2012-06-05</p> <p>while during days 174 and 175 raytracing suggests the <span class="hlt">observed</span> arrivals propagated in near surface ducts. No stratospheric arrivals were <span class="hlt">observed</span>...and DNIAR which may point to a different propagation mechanism (perhaps scattering). The FNIAR arrivals are not predicted by classic raytracing</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..12.4394B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..12.4394B"><span>The IDC Seismic, Hydroacoustic and <span class="hlt">Infrasound</span> low and high noise models</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Brown, David; Brachet, Nicolas; Mialle, Pierrick; Lebras, Ronan</p> <p>2010-05-01</p> <p>The International Data Centre (IDC) of the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) in Vienna, Austria, is developing the capability to routinely determine the sensor noise levels for all Seismic, Hydroacoustic and <span class="hlt">Infrasound</span> (SHI) stations of the International Monitoring System (IMS) sending data to the IDC. This noise data can be used to provide state of health information to station maintenance personnel, and can be used in network detection capability analyses, and can also be used as a quality control measure in automatic processing. Station noise is being determined as a Power Spectral Density (PSD) using the Welch overlapping method. When PSD's for a given sensor are collected over time and considered together it is possible to generate a Probability Density Function (PDF) for the power spectra and determine low- and high-noise curves that bound the PDF. When used in data quality control applications warnings can be issued if the PSD for incoming data for a given sensor is not found to be bounded by the previously determined low and high noise models for that sensor. In this paper, low and high noise models will be presented for representative seismic, hydroacoustic and <span class="hlt">infrasound</span> stations, as well as preliminary global low and high noise models for each of these technologies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.S51C2697P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.S51C2697P"><span>Detection of Regional <span class="hlt">Infrasound</span> Signals Using Array Data - Testing, Tuning, and Physical Interpretation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Park, J.; Stump, B. W.; Hayward, C.; Arrowsmith, S.; Che, I. Y.; Drob, D. P.</p> <p>2015-12-01</p> <p>In order to understand the impact environmental conditions have on <span class="hlt">infrasound</span> detection, an automated detector that accounts for both correlated and uncorrelated noise is run on data from a number of infrasonic arrays, all in a regional context. Data from six seismo-acoustic arrays in South Korea (BRDAR, CHNAR, KMPAR, KSGAR, TJIAR, and YPDAR), which are cooperatively operated by Korea Institute of Geoscience and Mineral Resources (KIGAM) and Southern Methodist University (SMU), were used. An adaptive F-detector (AFD) (Arrowsmith et al., 2009) is applied that utilizes the F-statistic (Blandford, 1974) with an adaptive procedure that assesses variations in coherent noise in order to reduce false alarms. The adaptive procedure is characterized by the time dependent C-value that is found to depend on the weather conditions and local site effects. Arrays located on islands or near the coast produce noise power densities that are higher, consistent with both higher wind speeds as well as ocean wave contributions that vary seasonally. These results suggest that optimal detection processing requires careful characterization of background noise level and its relationship to enviornmental measures at individual arrays. This study also documents significant seasonal variations in <span class="hlt">infrasound</span> detections including daily time of occurrence, total number of detections, and phase velocity/azimuth estimates. These time-dependent effects in most part explained by atmospheric models across the Korean peninsula as described by Drob et al. (2003).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD1004164','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD1004164"><span>Linear and Nonlinear <span class="hlt">Infrasound</span> Propagation to 1000 km</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2015-12-15</p> <p>to their average sea level values and the ambient temperature is set to 15oC, giving a static sound speed of 340 m/s. The <span class="hlt">source</span> is centered at an...alters the governing equations, but results in quantifiable dispersion characteristics. It is shown that this method leaves sound speeds and...2. Profiles of a) density, b) sound speed, and c) attenuation as a function of altitude -- 13 3. FDTD Pressure fluctuation snapshots, with</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015MNRAS.448.3731R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015MNRAS.448.3731R"><span>Local Group dSph radio survey with ATCA (I): <span class="hlt">observations</span> and background <span class="hlt">sources</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Regis, Marco; Richter, Laura; Colafrancesco, Sergio; Massardi, Marcella; de Blok, W. J. G.; Profumo, Stefano; Orford, Nicola</p> <p>2015-04-01</p> <p>Dwarf spheroidal (dSph) galaxies are key objects in near-field cosmology, especially in connection to the study of galaxy formation and evolution at small scales. In addition, dSphs are optimal targets to investigate the nature of dark matter. However, while we begin to have deep optical photometric <span class="hlt">observations</span> of the stellar population in these objects, little is known so far about their diffuse emission at any <span class="hlt">observing</span> frequency, and hence on thermal and non-thermal plasma possibly residing within dSphs. In this paper, we present deep radio <span class="hlt">observations</span> of six local dSphs performed with the Australia Telescope Compact Array (ATCA) at 16 cm wavelength. We mosaicked a region of radius of about 1 deg around three `classical' dSphs, Carina, Fornax, and Sculptor, and of about half of degree around three `ultrafaint' dSphs, BootesII, Segue2, and Hercules. The rms noise level is below 0.05 mJy for all the maps. The restoring beams full width at half-maximum ranged from 4.2 arcsec × 2.5 arcsec to 30.0 arcsec × 2.1 arcsec in the most elongated case. A catalogue including the 1392 <span class="hlt">sources</span> detected in the six dSph fields is reported. The main properties of the background <span class="hlt">sources</span> are discussed, with positions and fluxes of brightest objects compared with the FIRST, NVSS, and SUMSS <span class="hlt">observations</span> of the same fields. The <span class="hlt">observed</span> population of radio emitters in these fields is dominated by synchrotron <span class="hlt">sources</span>. We compute the associated <span class="hlt">source</span> number counts at 2 GHz down to fluxes of 0.25 mJy, which prove to be in agreement with AGN count models.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20040171614','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20040171614"><span><span class="hlt">Source</span> and Propagation Characteristics of Kilometric Continuum <span class="hlt">Observed</span> with Multiple Satellites</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hashimoto, K.; Anderson, R. R.; Green, J. L.; Matsumoto, H.</p> <p>2004-01-01</p> <p>Kilometric continuum radiation was first identified with the GEOTAIL Plasma Wave Instrument (PWI) as the high frequency extension of escaping continuum emissions in the frequency range from 100 kHz to 800 kHz. It consists of from a few to many narrow-band emissions. It was <span class="hlt">observed</span> mainly near the magnetic equator, and its <span class="hlt">source</span> was expected to be inside of the plasmapause and the topside equatorial region. Recently, data from the IMAGE Radio Plasma Imager (RPI) and Extreme ultraviolet (EUV) experiments have been used to show that kilometric continuum is generated at the plasmapause, in or near the magnetic equator, within a notch region, and have confirmed the expectation. Data from the CRRES PWI have also identified other <span class="hlt">sources</span> from the equatorial density irregularities. An example of CRRES <span class="hlt">observations</span> reveals a possibility that kilometric continuum has been radiated as a wide beam emission. The IMAGE and GEOTAIL simultaneous <span class="hlt">observations</span> are not like the previous <span class="hlt">observations</span> since they show it has been <span class="hlt">observed</span> to have a very broad emission cone. It could also be the highest frequency continuum enhancement so far <span class="hlt">observed</span> since it is associated with a high energy electron injection event.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008AGUFM.V51C2056W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008AGUFM.V51C2056W"><span>Seismo-Acoustic Array <span class="hlt">Observations</span> of Shallow Conduit Processes at Fuego Volcano, Guatemala</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Waite, G. P.; Lyons, J. J.; Nadeau, P. A.</p> <p>2008-12-01</p> <p>We deployed small antennas of six broadband seismic and five acoustic sensors 900 m north of the active vent of Fuego volcano during January 2008 to investigate the <span class="hlt">source</span> of explosions and background tremor. The L-shaped seismic array had stations spaced 30 m apart with one axis parallel to the ridge that runs north from the summit and the other axis down to the west for a total aperture of 150 m. The <span class="hlt">infrasound</span> sensors were deployed in a similar array, but with an average station spacing of 50 m. There was no lava effusion during the four-day deployment, but explosions were clearly recorded with the seismic and acoustic arrays approximately once per hour with varied amounts of ash, and with durations from ~20-150 s. In addition to the explosions, our seismic array recorded constant volcanic tremor at 1.9 Hz and various discrete events that were not generally detected by the acoustic array. The dominant class of such events, which repeated approximately 10 times per hour, had an impulsive onset with first motion toward the vent, a short duration of <5 s, dominant frequencies from 1-3 Hz, and no <span class="hlt">infrasound</span> component. All of the seismic signals were predominately surface waves radiating from the direction of the vent. Apparent velocities from overlapping 1 or 2 s windows of explosions decreased from 1-2 km/s at the onset to about 500 m/s at the arrival of the ground-coupled airwave. Events with no apparent <span class="hlt">infrasound</span> also have low apparent velocities of 0.5 - 2 km/s, suggesting they are occurring at shallow depths. For these events, a weak P-wave arrival was typically <span class="hlt">observed</span> about 200 ms before the shear- and surface-wave train. We also recorded some explosions that had very little seismic signal until the arrival of the ground-coupled airwave. <span class="hlt">Source</span> inversion was not possible due to the limited array geometry, but we used forward modeling of candidate <span class="hlt">source</span> geometries to infer differences between the <span class="hlt">sources</span> of the dominant seismic signals. Constraints from</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20000026343&hterms=analysis+energy+sources&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Danalysis%2Benergy%2Bsources','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20000026343&hterms=analysis+energy+sources&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D90%26Ntt%3Danalysis%2Benergy%2Bsources"><span>EGRET/COMPTEL <span class="hlt">Observations</span> of an Unusual, Steep-Spectrum Gamma-Ray <span class="hlt">Source</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Thompson, D. J.; Bertsch, D. L.; Hartman, R. C.; Collmar, W.; Johnson, W. N.</p> <p>1999-01-01</p> <p>During analysis of <span class="hlt">sources</span> below the threshold of the third EGRET catalog, we have discovered a <span class="hlt">source</span>, named GRO J1400-3956 based on the best position, with a remarkably steep spectrum. Archival analysis of COMPTEL data shows that the spectrum must have a strong turn-over in the energy range between COMPTEL and EGRET. The EGRET data show some evidence of time variability, suggesting an AGN, but the spectral change of slope is larger than that seen for most gamma-ray blazars. The sharp cutoff resembles the high-energy spectral breaks seen in some gamma-ray pulsars. There have as yet been no OSSE <span class="hlt">observations</span> of this <span class="hlt">source</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_15");'>15</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li class="active"><span>17</span></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_17 --> <div id="page_18" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="341"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19940036475&hterms=radio+telescope&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dradio%2Btelescope','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19940036475&hterms=radio+telescope&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Dradio%2Btelescope"><span>Spectral <span class="hlt">observations</span> of active region <span class="hlt">sources</span> with RATAN-600 and WSRT. [Westerbork Synthesis Radio Telescope</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Alissandrakis, C. E.; Gel'frejkh, G. B.; Borovik, V. N.; Korzhavin, A. N.; Bogod, V. M.; Nindos, A.; Kundu, M. R.</p> <p>1993-01-01</p> <p>We present spectral <span class="hlt">observations</span> of neutral line and sunspot associated <span class="hlt">sources</span> obtained with the RATAN-600 radio telescope and the WSRT in the wavelength range of 2 to 6 cm. <span class="hlt">Sources</span> associated with large sunspots have flat spectra, while neutral line <span class="hlt">sources</span> have very steep spectra. In the case of a large spot we estimated the magnetic field to be at least 2700 G at the base of the transition region and 1800 G in the low corona. We consider possible interpretations of the radio emission above the neutral lines. Gyroresonance emission at the fourth harmonic is inadequate, whereas emission from a small population of nonthermal electrons (total number 10 exp 30 to 10 exp 31) with a delta = 3 power law distribution seems to be sufficient.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016GeoRL..43.4263Y','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016GeoRL..43.4263Y"><span>Rapid estimation of tsunami <span class="hlt">source</span> centroid location using a dense offshore <span class="hlt">observation</span> network</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Yamamoto, N.; Hirata, K.; Aoi, S.; Suzuki, W.; Nakamura, H.; Kunugi, T.</p> <p>2016-05-01</p> <p>This paper proposes a rapid method of estimating tsunami <span class="hlt">source</span> locations using real-time ocean-bottom hydrostatic pressure data from a dense offshore <span class="hlt">observation</span> network. We defined two characteristic locations representing the real-time tsunami disturbance and the initial sea surface height distribution. First, we defined the tsunami centroid location (TCL), which is the centroid location of the maximum absolute amplitude of the real-time ocean-bottom hydrostatic pressure changes. Second, we defined the centroid location of the absolute values of the initial sea surface height displacements. To determine whether the TCL can approximate the centroid location of the tsunami <span class="hlt">source</span>, we examined approximately 1000 near-field synthetic tsunami scenarios and a realistic tsunami scenario of the 2011 Tohoku earthquake in the Japan Trench. From these examinations, it was confirmed that in most scenarios, the TCLs obtained within a few minutes after the occurrence of an earthquake were close to the actual corresponding tsunami <span class="hlt">source</span> locations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..1815102M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..1815102M"><span>Investigating the value of passive microwave <span class="hlt">observations</span> for monitoring volcanic eruption <span class="hlt">source</span> parameters</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Montopoli, Mario; Cimini, Domenico; Marzano, Frank</p> <p>2016-04-01</p> <p>Volcanic eruptions inject both gas and solid particles into the Atmosphere. Solid particles are made by mineral fragments of different sizes (from few microns to meters), generally referred as tephra. Tephra from volcanic eruptions has enormous impacts on social and economical activities through the effects on the environment, climate, public health, and air traffic. The size, density and shape of a particle determine its fall velocity and thus residence time in the Atmosphere. Larger particles tend to fall quickly in the proximity of the volcano, while smaller particles may remain suspended for several days and thus may be transported by winds for thousands of km. Thus, the impact of such hazards involves local as well as large scales effects. Local effects involve mostly the large sized particles, while large scale effects are caused by the transport of the finest ejected tephra (ash) through the atmosphere. Forecasts of ash paths in the atmosphere are routinely run after eruptions using dispersion models. These models make use of meteorological and volcanic <span class="hlt">source</span> parameters. The former are usually available as output of numerical weather prediction models or large scale reanalysis. <span class="hlt">Source</span> parameters characterize the volcanic eruption near the vent; these are mainly the ash mass concentration along the vertical column and the top altitude of the volcanic plume, which is strictly related to the flux of the mass ejected at the emission <span class="hlt">source</span>. These parameters should be known accurately and continuously; otherwise, strong hypothesis are usually needed, leading to large uncertainty in the dispersion forecasts. However, direct <span class="hlt">observations</span> during an eruption are typically dangerous and impractical. Thus, satellite remote sensing is often exploited to monitor volcanic emissions, using visible (VIS) and infrared (IR) channels available on both Low Earth Orbit (LEO) and Geostationary Earth Orbit (GEO) satellites. VIS and IR satellite imagery are very useful to monitor</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AAS...22033516C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AAS...22033516C"><span>EVLA <span class="hlt">Observations</span> of FR II Radio <span class="hlt">Sources</span> with Candidate Relativistic Hotspots</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Chartrand, Alexander M.; Miller, B. P.; Brandt, W. N.; Gawronski, M. P.; Cederbloom, S. E.</p> <p>2012-05-01</p> <p>We have identified six FR II radio <span class="hlt">sources</span> that are candidates to possess hotspots with modestly relativistic (0.2 < v/c < 0.7) bulk velocities, in contrast to the vast majority of FR II radio <span class="hlt">sources</span> that possess non-relativistic hotspot bulk velocities (e.g., v/c = 0.03 +/- 0.02 from Scheuer 1995). These candidates were selected based on their arm-length and flux-ratio asymmetries from a parent sample of 900 SDSS/FIRST double-lobed radio-loud quasars. For the four candidates lacking higher-resolution radio mapping, we obtained EVLA <span class="hlt">observations</span> at 5 GHz to confirm the hotspot parameters, to measure their radio spectral indices, and to check for the presence of any jets. The <span class="hlt">observations</span> were carried out on 12 June 2011 using 27 antennas in the A configuration. For one candidate, the morphology is found to be likely contaminated by an unrelated intruding <span class="hlt">source</span>. For two candidates, the fainter lobes are not detected at 5 GHz. Simulations suggest that 4-6/900 objects may randomly display asymmetries (e.g., due to environmental interactions) as found for the candidates. It is ruled out that the candidates are young <span class="hlt">sources</span> <span class="hlt">observed</span> prior to deceleration of their hotspots because their intrinsic lobe distances are not abnormal for FR II <span class="hlt">sources</span>. While it remains possible that a few of the candidates possess long-lived relativistic hotspots (e.g., one object shows additional supportive evidence in the form of a one-sided jet aligned with the brighter hotspot), we conclude that relativistic hotspots are extremely rare (<0.5%) or absent within double-lobed radio-loud quasars.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017AAS...22934606A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017AAS...22934606A"><span>Chandra <span class="hlt">Observation</span> of the WAT Radio <span class="hlt">Source</span>/ICM Interaction in Abell 623</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Anand, Gagandeep; Blanton, Elizabeth L.; Randall, Scott W.; Paterno-Mahler, Rachel; Douglass, Edmund</p> <p>2017-01-01</p> <p>Galaxy clusters are important objects for studying the physics of the intracluster medium (ICM), galaxy formation and evolution, and cosmological parameters. Clusters containing wide-angle tail (WAT) radio <span class="hlt">sources</span> are particularly valuable for studies of the interaction between these <span class="hlt">sources</span> and the surrounding ICM. These <span class="hlt">sources</span> are thought to form when the ram pressure from the ICM caused by the relative motion between the host radio galaxy and the cluster bends the radio lobes into a distinct wide-angle morphology. We present our results from the analysis of a Chandra <span class="hlt">observation</span> of the nearby WAT hosting galaxy cluster Abell 623. A clear decrement in X-ray emission is coincident with the southern radio lobe, consistent with being a cavity carved out by the radio <span class="hlt">source</span>. We present profiles of surface brightness, temperature, density, and pressure and find evidence for a possible shock. Based on the X-ray pressure in the vicinity of the radio lobes and assumptions about the content of the lobes, we estimate the relative ICM velocity required to bend the lobes into the <span class="hlt">observed</span> angle. We also present spectral model fits to the overall diffuse cluster emission and see no strong signature for a cool core. The sum of the evidence indicates that Abell 623 may be undergoing a large scale cluster-cluster merger.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20020080796','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20020080796"><span>Chandra and XMM <span class="hlt">Observations</span> of the ADC <span class="hlt">Source</span> 0921-630</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kallman, T. R.; Angelini, L.; Boroson, B.; Cottam, J.; White, Nicholas E. (Technical Monitor)</p> <p>2002-01-01</p> <p>We analyze <span class="hlt">observations</span> of the low mass X-ray binary 2S0921-63 obtained with the gratings and CCDs on Chandra and XMM. This object is a high inclination system showing evidence for an accretion disk corona (ADC). Such a corona has the potential to constrain the properties of the heated accretion disk in this system, and other LMXBs by extension. We find evidence for line emission which is generally consistent with that found by previous experiments, although we are able to detect more lines. For the first time in this <span class="hlt">source</span>, we find that the iron K line has multiple components. We set limits on the line widths and velocity offsets, and we fit the spectra to photoionization models and discuss the implications for accretion disk corona models. For the first time in any ADC <span class="hlt">source</span> we use these fits, together with density constraints based on the O VII line ratio, in order to constrain the flux in the medium-ionization region of the ADC. Under various assumptions about the <span class="hlt">source</span> luminosity this constrains the location of the emitting region. These estimates, together with estimates for the emission measure, favor a scenario in which the intrinsic luminosity of the <span class="hlt">source</span> is comparable to what we <span class="hlt">observe</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2003EAEJA....12733P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2003EAEJA....12733P"><span>Inversion of tsunami <span class="hlt">sources</span> by the adjoint method in the presence of <span class="hlt">observational</span> and model errors</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pires, C.; Miranda, P. M. A.</p> <p>2003-04-01</p> <p>The adjoint method is applied to the inversion of tsumani <span class="hlt">sources</span> from tide-gauge <span class="hlt">observations</span> in both idealized and realistic setups, with emphasis on the effects of <span class="hlt">observational</span>, bathymetric and other model errors in the quality of the inversion. The method is developed in a way that allows for the direct optimization of seismic focal parameters, in the case of seismic tsunamis, through a 4-step inversion procedure that can be fully automated, consisting in (i) <span class="hlt">source</span> area delimitation, by adjoint backward ray-tracing, (ii) adjoint optimization of the initial sea state, from a vanishing first-guess, (iii) non-linear adjustment of the fault model and (iv) final adjoint optimization in the fault parameter space. The methodology is systematically tested with synthetic data, showing its flexibility and robustness in the presence of significant amounts of error.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013HEAD...1312301A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013HEAD...1312301A"><span>TeV Signatures of Fermi and IACT <span class="hlt">Sources</span> <span class="hlt">Observed</span> by Milagro</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Abeysekara, Anushka U.; Milagro Collaboration</p> <p>2013-04-01</p> <p>We perform targeted searches in Milagro data to detect TeV emissions from potential TeV-emitting candidates. Galactic candidates were GeV pulsars from the Fermi LAT second <span class="hlt">source</span> catalog (2FGL) in the Milagro sky coverage (-7°< DEC < 80° ). Extragalactic candidates are selected from the 2FGL and from the Imaging Air Cerenkov Telescope (IACT) detections in the TeVCat catalog. Out of 52 pulsar targets, emission in the 1-100 TeV energy range is found coincident with 15 of them. We studied the TeV-GeV flux correlation of these <span class="hlt">observations</span>. Among 709 extragalactic <span class="hlt">observations</span> Markarian 421 was indentified with a high statistical significance and three other AGNs were identified as potential TeV emitting <span class="hlt">sources</span> with a flux just below our sensitivity threshold. Our measurements and comparisons of results with existing models will be presented in this talk.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19780003962&hterms=sas&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dsas','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19780003962&hterms=sas&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dsas"><span>SAS-2 <span class="hlt">observations</span> of high energy gamma rays from discrete <span class="hlt">sources</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Kniffen, D. A.; Fichtel, C. E.; Hartman, R. C.; Lamb, R. C.; Thompson, D. J.</p> <p>1977-01-01</p> <p>The SAS-2 identified six localized high energy (greater than 35 MeV) gamma ray <span class="hlt">sources</span>. Four of these are the radio pulsars, PSR 0531+21, PSR 0833-45, PSR 1818-04, and PSR 1717-46 discovered in a search of 75 radio pulsars. The fact that only one of these is <span class="hlt">observed</span> in X-rays, and the significant differences in pulse profiles in the gamma ray and radio <span class="hlt">observations</span>, leads to the speculation that different mechanisms are involved.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19800009714','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19800009714"><span>Satellite <span class="hlt">Observations</span> of Rapidly Varying Cosmic X-ray <span class="hlt">Sources</span>. Ph.D. Thesis - Catholic Univ.</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Maurer, G. S.</p> <p>1979-01-01</p> <p>The X-ray <span class="hlt">source</span> data obtained with the high energy celestial X-ray detector on the Orbiting Solar Observatory -8 are presented. The results from the 1977 Crab <span class="hlt">observation</span> show nonstatistical fluctuations in the pulsed emission and in the structure of the integrated pulse profile which cannot be attributed to any known systematic effect. The Hercules <span class="hlt">observations</span> presented here provide information on three different aspects of the pulsed X-ray emission: the variation of pulsed flux as a function of the time from the beginning of the ON-state, the variation of pulsed flux as a function of binary phase, and the energy spectrum of the pulse emission.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19740027123','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19740027123"><span><span class="hlt">Observation</span> of soft X-rays from extended <span class="hlt">sources</span>. [such as Perseus star cluster</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Catura, R. C.; Acton, L. W.</p> <p>1974-01-01</p> <p>Efforts were directed toward surveying several supernova remnants for the emission of soft X-rays. Rather than attempt to detect such faint X-ray emission, the program was redirected to <span class="hlt">observe</span> the spectrum and angular structure of the extended X-ray <span class="hlt">source</span> in the Perseus cluster of galaxies and the super-nova remnant Puppis A. An attempt was made to detect X-ray line emission from Puppis A with a Bragg crystal spectrometer. <span class="hlt">Observations</span> provide evidence for the presence of X-ray line emission in the spectrum of Puppis A near .65 keV.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19950026840','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19950026840"><span>Compton Observatory <span class="hlt">observations</span> of clusters of galaxies and extragalactic radio <span class="hlt">sources</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p></p> <p>1995-01-01</p> <p>This task involved the investigation of the emission of clusters of galaxies, particularly those which contain extended radio emission, in the gamma-ray region of the spectrum. <span class="hlt">Observations</span> were made of several clusters using the Compton Observatory EGRET instrument. For each cluster a measured flux or upper limit on the gamma-ray flux was obtained. In only one case, Abell 2199, was there a significant measured flux. This <span class="hlt">source</span> is spatially confused with a know blazar in the field of view. The <span class="hlt">observation</span> is consistent with all emissions being from the blazar.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApJS..218...21L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApJS..218...21L"><span>CASSIS: The Cornell Atlas of Spitzer/Infrared Spectrograph <span class="hlt">Sources</span>. II. High-resolution <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lebouteiller, V.; Barry, D. J.; Goes, C.; Sloan, G. C.; Spoon, H. W. W.; Weedman, D. W.; Bernard-Salas, J.; Houck, J. R.</p> <p>2015-06-01</p> <p>The Infrared Spectrograph (IRS) on board the Spitzer Space Telescope <span class="hlt">observed</span> about 15,000 objects during the cryogenic mission lifetime. <span class="hlt">Observations</span> provided low-resolution (R=λ /{Δ }λ ≈ 60-127) spectra over ≈ 5-38 μm and high-resolution (R≈ 600) spectra over 10-37 μm. The Cornell Atlas of Spitzer/IRS <span class="hlt">Sources</span> (CASSIS) was created to provide publishable quality spectra to the community. Low-resolution spectra have been available in CASSIS since 2011, and here we present the addition of the high-resolution spectra. The high-resolution <span class="hlt">observations</span> represent approximately one-third of all staring <span class="hlt">observations</span> performed with the IRS instrument. While low-resolution <span class="hlt">observations</span> are adapted to faint objects and/or broad spectral features (e.g., dust continuum, molecular bands), high-resolution <span class="hlt">observations</span> allow more accurate measurements of narrow features (e.g., ionic emission lines) as well as a better sampling of the spectral profile of various features. Given the narrow aperture of the two high-resolution modules, cosmic ray hits and spurious features usually plague the spectra. Our pipeline is designed to minimize these effects through various improvements. A super-sampled point-spread function was created in order to enable the optimal extraction in addition to the full aperture extraction. The pipeline selects the best extraction method based on the spatial extent of the object. For unresolved <span class="hlt">sources</span>, the optimal extraction provides a significant improvement in signal-to-noise ratio over a full aperture extraction. We have developed several techniques for optimal extraction, including a differential method that eliminates low-level rogue pixels (even when no dedicated background <span class="hlt">observation</span> was performed). The updated CASSIS repository now includes all the spectra ever taken by the IRS, with the exception of mapping <span class="hlt">observations</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoRL..42.6614C','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoRL..42.6614C"><span>On the use of remote <span class="hlt">infrasound</span> and seismic stations to constrain the eruptive sequence and intensity for the 2014 Kelud eruption</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Caudron, Corentin; Taisne, Benoít; Garcés, Milton; Alexis, Le Pichon; Mialle, Pierrick</p> <p>2015-08-01</p> <p>The February 2014 eruption of Kelud volcano (Indonesia) destroyed most of the instruments near it. We use remote seismic and <span class="hlt">infrasound</span> sensors to reconstruct the eruptive sequence. The first explosions were relatively weak seismic and <span class="hlt">infrasound</span> events. A major stratospheric ash injection occurred a few minutes later and produced long-lasting atmospheric and ground-coupled acoustic waves that were detected as far as 11,000 km by <span class="hlt">infrasound</span> sensors and up to 2300 km away on seismometers. A seismic event followed ˜12 minutes later and was recorded 7000 km away by seismometers. We estimate a volcanic intensity around 10.9, placing the 2014 Kelud eruption between the 1980 Mount St. Helens and 1991 Pinatubo eruptions intensities. We demonstrate how remote <span class="hlt">infrasound</span> and seismic sensors are critical for the early detection of volcanic explosions, and how they can help to constrain and understand eruptive sequences.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.S51D2702T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.S51D2702T"><span>On the use of remote <span class="hlt">infrasound</span> and seismic stations to constrain the eruptive sequence and intensity for the 2014 Kelud eruption</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Taisne, B.; Caudron, C.; Garces, M. A.; Mialle, P.; LE Pichon, A.</p> <p>2015-12-01</p> <p>The February 2014 eruption of Kelud volcano (Indonesia) destroyed most of the instruments near it. We use remote seismic and <span class="hlt">infrasound</span> sensors to reconstruct the eruptive sequence. The first explosions were relatively weak seismic and <span class="hlt">infrasound</span> events. A major stratospheric ash injection occurred a few minutes later and produced long-lasting atmospheric and ground-coupled acoustic waves that were detected as far as 11,000 km by <span class="hlt">infrasound</span> sensors, and up to 2,300 km away on seismometers. A seismic event followed ~12 minutes later and was recorded 7,000 km away by seismometers. We estimate a volcanic intensity [Pyle,2000] around 10.9, placing the 2014 Kelud eruption between the 1980 Mount St. Helens and 1991 Pinatubo eruptions intensities. We demonstrate how remote <span class="hlt">infrasound</span> and seismic sensors are critical for the early detection of volcanic explosions, and how they can help to constrain and understand eruptive sequences.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013EGUGA..1513741S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013EGUGA..1513741S"><span>Characterization of dust emission from alluvial <span class="hlt">sources</span> using aircraft <span class="hlt">observations</span> and high-resolution modeling</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schepanski, Kerstin; Flamant, Cyrille; Chaboureau, Jean-Pierre; Kocha, Cecile; Banks, Jamie; Brindley, Helen; Lavaysse, Christophe; Marnas, Fabien; Pelon, Jacques; Tulet, Pierre</p> <p>2013-04-01</p> <p>We investigate mineral dust emission from alluvial sediments within the upland region in northern Mauritania in the vicinity of a decaying nocturnal low-level jet (LLJ). For the first time, the impact of valleys that are embedded in a rather homogeneous surrounding is investigated with regard to their role as dust <span class="hlt">source</span>. Measures for local atmospheric dust burden were retrieved from airborne <span class="hlt">observations</span>, satellite <span class="hlt">observations</span>, and model simulations and analyzed in order to provide complementary information at different horizontal scales. <span class="hlt">Observations</span> by the LNG backscatter lidar system flying aboard the SAFIRE Falcon 20 aircraft were taken along five parallel flight legs perpendicular to the orientation of the main valley system dominating the topography of the study area. Results from a comparison of lidar-derived extinction coefficients with topography and aerial photographs confirm the relevance of (1) alluvial sediments at the valley bottoms as a dust <span class="hlt">source</span>, and (2) the break-down of the nocturnal LLJ as a trigger for dust emission in this region. An evaluation of the AROME regional model, forecasting dust at high resolution (5 km grid), points towards an underrepresentation of alluvial dust <span class="hlt">sources</span> in this region. This is also evident from simulations by the MesoNH research model. Although MesoNH simulations show higher dust loadings than AROME which are more comparable to the <span class="hlt">observations</span>, both models understimate the dust concentrations within the boundary layer compared to lidar <span class="hlt">observations</span>. A sensitivity study on the impact of horizontal grid spacing (5 km versus 1 km) highlights the importance of spatial resolution on simulated dust loadings.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2011AGUFM.V33A2608M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2011AGUFM.V33A2608M"><span>Volcanic jet noise: infrasonic <span class="hlt">source</span> processes and atmospheric propagation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Matoza, R. S.; Fee, D.; Ogden, D. E.</p> <p>2011-12-01</p> <p>Volcanic eruption columns are complex flows consisting of (possibly supersonic) injections of ash-gas mixtures into the atmosphere. A volcanic eruption column can be modeled as a lower momentum-driven jet (the gas-thrust region), which transitions with altitude into a thermally buoyant plume. Matoza et al. [2009] proposed that broadband infrasonic signals recorded during this type of volcanic activity represent a low-frequency form of jet noise. Jet noise is produced at higher acoustic frequencies by smaller-scale man-made jet flows (e.g., turbulent jet flow from jet engines and rockets). Jet noise generation processes could operate at larger spatial scales and produce infrasonic frequencies in the lower gas-thrust portion of the eruption column. Jet-noise-like infrasonic signals have been <span class="hlt">observed</span> at ranges of tens to thousands of kilometers from sustained volcanic explosions at Mount St. Helens, WA; Tungurahua, Ecuador; Redoubt, AK; and Sarychev Peak, Kuril Islands. Over such distances, the atmosphere cannot be considered homogeneous. Long-range <span class="hlt">infrasound</span> propagation takes place primarily in waveguides formed by vertical gradients in temperature and horizontal winds, and exhibits strong spatiotemporal variability. The timing and location of volcanic explosions can be estimated from remote infrasonic data and could be used with ash cloud dispersion forecasts for hazard mitigation. <span class="hlt">Source</span> studies of infrasonic volcanic jet noise, coupled with <span class="hlt">infrasound</span> propagation modeling, hold promise for being able to constrain more detailed eruption jet parameters with remote, ground-based geophysical data. Here we present recent work on the generation and propagation of volcanic jet noise. Matoza, R. S., D. Fee, M. A. Garcés, J. M. Seiner, P. A. Ramón, and M. A. H. Hedlin (2009), Infrasonic jet noise from volcanic eruptions, Geophys. Res. Lett., 36, L08303, doi:10.1029/2008GL036486.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110011697','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110011697"><span>Lessons Learned from OMI <span class="hlt">Observations</span> of Point <span class="hlt">Source</span> SO2 Pollution</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Krotkov, N.; Fioletov, V.; McLinden, Chris</p> <p>2011-01-01</p> <p>The Ozone Monitoring Instrument (OMI) on NASA Aura satellite makes global daily measurements of the total column of sulfur dioxide (SO2), a short-lived trace gas produced by fossil fuel combustion, smelting, and volcanoes. Although anthropogenic SO2 signals may not be detectable in a single OMI pixel, it is possible to see the <span class="hlt">source</span> and determine its exact location by averaging a large number of individual measurements. We describe new techniques for spatial and temporal averaging that have been applied to the OMI SO2 data to determine the spatial distributions or "fingerprints" of SO2 burdens from top 100 pollution <span class="hlt">sources</span> in North America. The technique requires averaging of several years of OMI daily measurements to <span class="hlt">observe</span> SO2 pollution from typical anthropogenic <span class="hlt">sources</span>. We found that the largest point <span class="hlt">sources</span> of SO2 in the U.S. produce elevated SO2 values over a relatively small area - within 20-30 km radius. Therefore, one needs higher than OMI spatial resolution to monitor typical SO2 <span class="hlt">sources</span>. TROPOMI instrument on the ESA Sentinel 5 precursor mission will have improved ground resolution (approximately 7 km at nadir), but is limited to once a day measurement. A pointable geostationary UVB spectrometer with variable spatial resolution and flexible sampling frequency could potentially achieve the goal of daily monitoring of SO2 point <span class="hlt">sources</span> and resolve downwind plumes. This concept of taking the measurements at high frequency to enhance weak signals needs to be demonstrated with a GEOCAPE precursor mission before 2020, which will help formulating GEOCAPE measurement requirements.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.G41A1016L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.G41A1016L"><span>Deep <span class="hlt">source</span> model for Nevado del Ruiz Volcano, Colombia, constrained by interferometric synthetic aperture radar <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Lundgren, P.; Samsonov, S. V.; López, C. M.; Ordoñez, M.</p> <p>2015-12-01</p> <p>Nevado del Ruiz (NRV) is part of a large volcano complex in the northern Andes of Colombia with a large glacier that erupted in 1985, generating a lahar killing over 23,000 people in the city of Armero and 2,000 people in the town of Chinchina. NRV is the most active volcano in Colombia and since 2012 has generated small eruptions, with no casualties, and constant gas and ash emissions. Interferometric synthetic aperture radar (InSAR) <span class="hlt">observations</span> from ascending and descending track RADARSAT-2 data show a large (>20 km) wide inflation pattern apparently starting in late 2011 to early 2012 and continuing to the time of this study in early 2015 at a LOS rate of over 3-4 cm/yr (Fig. 1). Volcano pressure volume models for both a point <span class="hlt">source</span> (Mogi) and a spheroidal (Yang) <span class="hlt">source</span> find solutions over 14 km beneath the surface, or 10 km below sea level, and centered 10 km to the SW of Nevado del Ruiz volcano. The spheroidal <span class="hlt">source</span> has a roughly horizontal long axis oriented parallel to the Santa Isabel - Nevado del Ruiz volcanic line and perpendicular to the ambient compressive stress direction. Its solution provides a statistically significant improvement in fit compared to the point <span class="hlt">source</span>, though consideration of spatially correlated noise <span class="hlt">sources</span> may diminish this significance. Stress change computations do not favor one model over the other but show that propagating dikes would become trapped in sills, leading to a more complex pathway to the surface and possibly explaining the significant lateral distance between the modeled <span class="hlt">sources</span> and Nevado del Ruiz volcano.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110016130','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110016130"><span>High Resolution Rapid Response <span class="hlt">Observations</span> of Compact Radio <span class="hlt">Sources</span> with the Ceduna Hobart Interferometer (CHI)</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Blanchard, Jay M.; Lovell, James E. J.; Ojha, Roopesh; Kadler, Matthias; Dickey, John M.; Edwards, Philip G.</p> <p>2011-01-01</p> <p>Context. Frequent, simultaneous <span class="hlt">observations</span> across the electromagnetic spectrum are essential to the study of a range of astrophysical phenomena including Active Galactic Nuclei. A key tool of such studies is the ability to <span class="hlt">observe</span> an object when it flares i.e. exhibits a rapid and significant increase in its flux density. Aims. We describe the specific <span class="hlt">observational</span> procedures and the calibration techniques that have been developed and tested to create a single baseline radio interferometer. that can rapidly <span class="hlt">observe</span> a flaring object. This is the only facility that is dedicated to rapid high resolution radio <span class="hlt">observations</span> of an object south of -30 degrees declination. An immediate application is to provide rapid contemporaneous radio coverage of AGN flaring at y-ray frequencies detected by the Fermi Gamma-ray Space Telescope. Methods. A single baseline interferometer was formed with radio telescopes in Hobart, Tasmania and Ceduna, South Australia. A software correlator was set up at the University of Tasmania to correlate these data. Results. Measurements of the flux densities of flaring objects can be made using our <span class="hlt">observing</span> strategy within half an hour of a triggering event. These <span class="hlt">observations</span> can be calibrated with amplitude errors better than 20%. Lower limits to the brightness temperatures of the <span class="hlt">sources</span> can also be calculated using CHI. Key words. instrumentation:interferometers - galaxies:active - galaxies:jets - galaxies:nuclei quasars:general gamma rays:galaxies- 1.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_16");'>16</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li class="active"><span>18</span></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_18 --> <div id="page_19" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="361"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3958625','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=3958625"><span><span class="hlt">Sources</span> of Information and Behavioral Patterns in Online Health Forums: <span class="hlt">Observational</span> Study</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Friede, Tim; Grabowski, Jens; Koschack, Janka; Makedonski, Philip; Himmel, Wolfgang</p> <p>2014-01-01</p> <p>Background Increasing numbers of patients are raising their voice in online forums. This shift is welcome as an act of patient autonomy, reflected in the term “expert patient”. At the same time, there is considerable concern that patients can be easily misguided by pseudoscientific research and debate. Little is known about the <span class="hlt">sources</span> of information used in health-related online forums, how users apply this information, and how they behave in such forums. Objective The intent of the study was to identify (1) the <span class="hlt">sources</span> of information used in online health-related forums, and (2) the roles and behavior of active forum visitors in introducing and disseminating this information. Methods This <span class="hlt">observational</span> study used the largest German multiple sclerosis (MS) online forum as a database, analyzing the user debate about the recently proposed and controversial Chronic Cerebrospinal Venous Insufficiency (CCSVI) hypothesis. After extracting all posts and then filtering relevant CCSVI posts between 01 January 2008 and 17 August 2012, we first identified hyperlinks to scientific publications and other information <span class="hlt">sources</span> used or referenced in the posts. Employing k-means clustering, we then analyzed the users’ preference for <span class="hlt">sources</span> of information and their general posting habits. Results Of 139,912 posts from 11,997 threads, 8628 posts discussed or at least mentioned CCSVI. We detected hyperlinks pointing to CCSVI-related scientific publications in 31 posts. In contrast, 2829 different URLs were posted to the forum, most frequently referring to social media, such as YouTube or Facebook. We identified a total of 6 different roles of hyperlink posters including Social Media Fans, Organization Followers, and Balanced <span class="hlt">Source</span> Users. Apart from the large and nonspecific residual category of the “average user”, several specific behavior patterns were identified, such as the small but relevant groups of CCSVI-Focused Responders or CCSVI Activators. Conclusions The bulk</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20100020935','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20100020935"><span>Deep Galex <span class="hlt">Observations</span> of the Coma Cluster: <span class="hlt">Source</span> Catalog and Galaxy Counts</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hammer, D.; Hornschemeier, A. E.; Mobasher, B.; Miller, N.; Smith, R.; Arnouts, S.; Milliard, B.; Jenkins, L.</p> <p>2010-01-01</p> <p>We present a <span class="hlt">source</span> catalog from deep 26 ks GALEX <span class="hlt">observations</span> of the Coma cluster in the far-UV (FUV; 1530 Angstroms) and near-UV (NUV; 2310 Angstroms) wavebands. The <span class="hlt">observed</span> field is centered 0.9 deg. (1.6 Mpc) south-west of the Coma core, and has full optical photometric coverage by SDSS and spectroscopic coverage to r-21. The catalog consists of 9700 galaxies with GALEX and SDSS photometry, including 242 spectroscopically-confirmed Coma member galaxies that range from giant spirals and elliptical galaxies to dwarf irregular and early-type galaxies. The full multi-wavelength catalog (cluster plus background galaxies) is 80% complete to NUV=23 and FUV=23.5, and has a limiting depth at NUV=24.5 and FUV=25.0 which corresponds to a star formation rate of 10(exp -3) solar mass yr(sup -1) at the distance of Coma. The GALEX images presented here are very deep and include detections of many resolved cluster members superposed on a dense field of unresolved background galaxies. This required a two-fold approach to generating a <span class="hlt">source</span> catalog: we used a Bayesian deblending algorithm to measure faint and compact <span class="hlt">sources</span> (using SDSS coordinates as a position prior), and used the GALEX pipeline catalog for bright and/or extended objects. We performed simulations to assess the importance of systematic effects (e.g. object blends, <span class="hlt">source</span> confusion, Eddington Bias) that influence <span class="hlt">source</span> detection and photometry when using both methods. The Bayesian deblending method roughly doubles the number of <span class="hlt">source</span> detections and provides reliable photometry to a few magnitudes deeper than the GALEX pipeline catalog. This method is also free from <span class="hlt">source</span> confusion over the UV magnitude range studied here: conversely, we estimate that the GALEX pipeline catalogs are confusion limited at NUV approximately 23 and FUV approximately 24. We have measured the total UV galaxy counts using our catalog and report a 50% excess of counts across FUV=22-23.5 and NUV=21.5-23 relative to previous GALEX</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010EGUGA..1213066R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010EGUGA..1213066R"><span>Parallel Grid approach to solve Feature Selection problem in volcanic <span class="hlt">infrasound</span> signals classification</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Reitano, Danilo; Pistagna, Fabrizio; Russo, Gaetano; Valenti, Vincenzo</p> <p>2010-05-01</p> <p>The continuous monitoring of an active volcano, such as Mt. Etna (Sicily, Italy), represents one of the main tasks for the Italian National Institute of Geophysics and Volcanology (INGV), Catania Branch. Around the volcano summit area, four <span class="hlt">infrasound</span> sensors have been installed during the last recent years, which allow to acquire, real time waveforms that are subsequently stored on a server, located inside the INGV Control Room. A new method here introduced, based on Genetic Algorithms (GA), has been used to analyze the data coming from the remote <span class="hlt">infrasound</span> sensors stations. In particular, the acquired signals have been processed by a custom modular software: the first module allows the visual manipulation, filtering and, in order to optimize performances, resampling the data to better elaborate them. The second module, using an alghorithm (G. Russo, 2009 ) based on two different thresholds (upper and lower) and the standard deviation, is able to recognize and collect <span class="hlt">infrasound</span> events (IE) from the stored data. In the third step, the Green & Nueberg algorithm (2006) is used to correlate different families of IE and define the clusters nodes. Once a minimum number of families are characterized, they define the main features inside each cluster. Feature extraction process is a very complex algorithm due to the large number of requested correlations. In order to speed up the time needed to carry out so many simulations, the code has been deployed and executed on the Sicilian Grid infrastructure owned and managed by the Consorzio Cometa, a not-for-profit organisation including INGV among its members. The infrastructure, distributed across the Sicilian territory, is composed of 7 sites for a total of about 2000 CPU cores and more than 250 TB of storage. All the sites of the infrastructure are equipped with low latency Infiniband networks and are installed with MPI libraries. A complete workflow has been created from scratch to execute the various phases of the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AGUFM.S41B4468B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AGUFM.S41B4468B"><span>Implementation and Testing of an Improved Mathematical Framework for the Bayesian Infrasonic <span class="hlt">Source</span> Localization Method</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Blom, P. S.; Arrowsmith, S.; Marcillo, O. E.</p> <p>2014-12-01</p> <p>The Bayesian Infrasonic <span class="hlt">Source</span> Localization (BISL) framework for estimating the location and time of an infrasonic event using distant <span class="hlt">observations</span> was proposed in 2010 and expanded in 2013 to allow inclusion of propagation based priors. Recently, modifications to the mathematical framework have been made to remove redundancies in the parameter space and generalize the framework. Such modifications are aimed at improving the performance and efficiency of the method. This new mathematical formulation has been implemented using the Python scripting language and is planned to be included in the InfraPy software package alongside the existing detection and association methods. The details of the new mathematical framework and its implementation will be presented along with results of performance tests. IMS data has been used to evaluate the method at global distances and <span class="hlt">infrasound</span> from the smaller scale explosions provides an opportunity to study regional performance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19890039754&hterms=1608&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3D%2526%25231608','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19890039754&hterms=1608&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3D%2526%25231608"><span>Exosat <span class="hlt">observations</span> of the X-ray burst <span class="hlt">source</span> 4U 1608-52</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Penninx, W.; Damen, E.; Van Paradijs, J.; Tan, J.; Lewin, W. H. G.</p> <p>1989-01-01</p> <p>The results of an analysis of two Exosat <span class="hlt">observations</span> (July 1984, May 1986) of the highly variable X-ray burst <span class="hlt">source</span> 4U 1608-52 are presented. During both <span class="hlt">observations</span> the persistent X-ray flux was low (quiescence), and the persistent X-ray spectrum could be well fitted with a power-law model, with approximately the same index, but a somewhat different low-energy cut off. During both <span class="hlt">observations</span> one type 1 burst was seen. It is shown that the relation between color temperature and effective temperature differs markedly from simple relations derived from theoretical models. A dip in the bolometric flux occurred near the peak of the 1986 burst. Possible models for this dip are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/934992','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/934992"><span>Preseismic Velocity Changes <span class="hlt">Observed</span> from Active <span class="hlt">Source</span> Monitoringat the Parkfield SAFOD Drill Site</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Daley, Thomas; Niu, Fenglin; Silver, Paul G.; Daley, Thomas M.; Cheng, Xin; Majer, Ernest L.</p> <p>2008-06-10</p> <p>Measuring stress changes within seismically active fault zones has been a long-sought goal of seismology. Here we show that such stress changes are measurable by exploiting the stress dependence of seismic wave speed from an active <span class="hlt">source</span> cross-well experiment conducted at the SAFOD drill site. Over a two-month period we <span class="hlt">observed</span> an excellent anti-correlation between changes in the time required for an S wave to travel through the rock along a fixed pathway--a few microseconds--and variations in barometric pressure. We also <span class="hlt">observed</span> two large excursions in the traveltime data that are coincident with two earthquakes that are among those predicted to produce the largest coseismic stress changes at SAFOD. Interestingly, the two excursions started approximately 10 and 2 hours before the events, respectively, suggesting that they may be related to pre-rupture stress induced changes in crack properties, as <span class="hlt">observed</span> in early laboratory studies.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014AtmEn..98..510S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014AtmEn..98..510S"><span><span class="hlt">Source</span> apportionment of PM10 in the Western Mediterranean based on <span class="hlt">observations</span> from a cruise ship</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Schembari, C.; Bove, M. C.; Cuccia, E.; Cavalli, F.; Hjorth, J.; Massabò, D.; Nava, S.; Udisti, R.; Prati, P.</p> <p>2014-12-01</p> <p>Two intensive PM10 sampling campaigns were performed in the summers of 2009 and 2010 on the ship Costa Pacifica during cruises in the Western Mediterranean. Samples, mainly collected on an hourly basis, were analysed with different techniques (Particle Induced X-Ray Emission, PIXE; Energy Dispersive - X Ray Fluorescence, ED-XRF; Ion Chromatography, IC; Thermo-optical analysis) to retrieve the PM10 composition and its time pattern. The data were used for obtaining information about the <span class="hlt">sources</span> of aerosol, with a focus on ship emissions, through apportionment using chemical marker compounds, correlation analysis and Positive Matrix Factorization (PMF) receptor modelling. For the campaign in 2010, 66% of the aerosol sulphate was found to be anthropogenic, only minor contributions of dust and sea salt sulphate were <span class="hlt">observed</span> while the biogenic contribution, estimated based on the measurements of MSA, was found to be more important (26%), but influenced by large uncertainties. V and Ni were found to be suitable tracers of ship emissions during the campaigns. Four <span class="hlt">sources</span> of aerosol were resolved by the PMF analysis; the <span class="hlt">source</span> having the largest impact on PM10, BC and sulphate was identified as a mixed <span class="hlt">source</span>, comprising emissions from ships. The correlations between sulphate and V and Ni showed the influence of ship emissions on sulphate in marine air masses. For the leg Palma-Tunis crossing a main ship route, the correlations between aerosol sulphate and V and Ni were particularly strong (r2 = 0.9 for both elements).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012AGUFM.P33B1928S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012AGUFM.P33B1928S"><span><span class="hlt">Sources</span> and Losses of Mg in Mercury's Exosphere Inferred from MESSENGER <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Sarantos, M.; Killen, R. M.; McClintock, W. E.; Merkel, A. W.; Vervack, R. J.; Burger, M. H.; Cassidy, T.; Slavin, J. A.; Sprague, A. L.; Solomon, S. C.</p> <p>2012-12-01</p> <p>Modeling of MESSENGER data from three Mercury years suggests that exospheric Mg at high altitudes can be most often fit by a combination of components at temperatures of 3000 K and 20,000 K, although on most days just a 5000 K <span class="hlt">source</span> fits equally well. Signatures consistent with sputtering by the solar wind were not <span class="hlt">observed</span> often, with the possible exception of nightside precipitation. The combined <span class="hlt">source</span> fluxes inferred from orbital phase data approach locally 2 × 10^6 atoms cm-2 s-1, consistent with the flyby results. These rates may be provided by impact vaporization, and the inferred temperatures could be explained if both cool atoms and Mg-bearing molecules, a precursor to fast atoms, were ejected from the surface. The inferred <span class="hlt">source</span> of exospheric Mg is non-uniform. The hot Mg component (20,000 K) is almost always inferred to originate near dawn and is highly correlated with the hot Ca <span class="hlt">source</span>, suggesting that hot Ca and Mg atoms could be produced by the same physical process. The cooler (3000 K) component is more variable and does not always correlate spatially with the hot component.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20030106014','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20030106014"><span>A XMM-Newton <span class="hlt">Observation</span> of Nova LMC 1995, a Bright Supersoft X-ray <span class="hlt">Source</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Orio, Marina; Hartmann, Wouter; Still, Martin; Greiner, Jochen</p> <p>2003-01-01</p> <p>Nova LMC 1995, previously detected during 1995-1998 with ROSAT, was <span class="hlt">observed</span> again as a luminous supersoft X-ray <span class="hlt">source</span> with XMM-Newton in December of 2000. This nova offers the possibility to <span class="hlt">observe</span> the spectrum of a hot white dwarf, burning hydrogen in a shell and not obscured by a wind or by nebular emission like in other supersoft X-ray <span class="hlt">sources</span>. Notwithstanding uncertainties in the calibration of the EPIC instruments at energy E<0.5 keV, using atmospheric models in Non Local Thermonuclear Equilibrium we derived an effective temperature in the range 400,000-450,000 K, a bolometric luminosity Lbolabout equal to 2.3 times 10 sup37 erg s sup-l, and we verified that the abundance of carbon is not significantly enhanced in the X-rays emitting shell. The RGS grating spectra do not show emission lines (originated in a nebula or a wind) <span class="hlt">observed</span> for some other supersoft X-ray <span class="hlt">sources</span>. The crowded atmospheric absorption lines of the white dwarf cannot be not resolved. There is no hard component (expected from a wind, a surrounding nebula or an accretion disk), with no counts above the background at E>0.6 keV, and an upper limit Fx,hard = 10 sup-14 erg s sup-l cm sup-2 to the X-ray flux above this energy. The background corrected count rate measured by the EPIC instruments was variable on time scales of minutes and hours, but without the flares or sudden obscuration <span class="hlt">observed</span> for other novae. The power spectrum shows a peak at 5.25 hours, possibly due to a modulation with the orbital period. We also briefly discuss the scenarios in which this nova may become a type Ia supernova progenitor.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22034695','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22034695"><span>ON THE NATURE OF HARD X-RAY EXTRAGALACTIC <span class="hlt">SOURCES</span> <span class="hlt">OBSERVED</span> WITH XMM-NEWTON</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jimenez-Bailon, E.; Huerta, E. M.; Krongold, Y.; Chavushyan, V.; Schartel, N.; Santos-Lleo, M.</p> <p>2012-03-15</p> <p>Over the last decade, X-ray surveys have provided outstanding new results due to the lack of the common selection effects present at other wavelengths. Here, we have selected a sample of unidentified <span class="hlt">sources</span> from the XMM-Newton Slew Survey Catalog, likely to be extragalactic. Five of them were <span class="hlt">observed</span> with the XMM-Newton observatory. In this work, we present the results of the spectral analysis of these objects in the X-ray and optical bands. Only three of them had useful spectroscopic X-ray data, and follow up <span class="hlt">observations</span> were carried out in the optical range to determine their coordinates, classification, and redshift. The <span class="hlt">sources</span> are different types of active galactic nuclei (AGNs) with redshifts ranging from 0.059 to 0.386. The properties at both spectral ranges (X-rays and optical) are compatible with the common properties of their types of AGNs. Although the <span class="hlt">sources</span> were selected by their hard X-ray properties, none of the three detected objects turned out to be an obscured AGN.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010hers.prop.1122P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010hers.prop.1122P"><span>OT1_rpaladin_1: PACS and SPIRE <span class="hlt">observations</span> of Galactic anomalous emission <span class="hlt">sources</span>.</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Paladini, R.</p> <p>2010-07-01</p> <p>Despite the increasing evidence that the anomalous emission is a new physical mechanism acting in the diffuse interstellar medium, the nature and distribution of this component remains elusive. The currently most favored models attribute the <span class="hlt">observed</span> microwave excess to rotating very small dust grains (PAHs and VSGs). Nonetheless, the infrared properties of the <span class="hlt">sources</span> which, to date, are known to exhibit this type of emission are very poorly known mostly due to the limited angular resolution and frequency coverage of DIRBE and IRAS data. We propose HERSCHEL PACS and SPIRE mapping of three Galactic anomalous emission <span class="hlt">sources</span> (LDN 1780, LDN 675 and LDN 1111). This data, when combined with ancillary NIR and mid-IR data of comparable angular resolution (mainly from Spitzer), and coupled with available dust models, will allow to set tight constraints on the radiation field in the emitting <span class="hlt">sources</span> as well as in their immediate surroundings. Such constraints, in turn, will allow to estimate the abundances of PAHs, VSGs and BGs, hence to shed light on the potential link between these dust populations and the <span class="hlt">observed</span> microwave excess.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4846444','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=4846444"><span><span class="hlt">Observation</span> of image pair creation and annihilation from superluminal scattering <span class="hlt">sources</span></span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Clerici, Matteo; Spalding, Gabriel C.; Warburton, Ryan; Lyons, Ashley; Aniculaesei, Constantin; Richards, Joseph M.; Leach, Jonathan; Henderson, Robert; Faccio, Daniele</p> <p>2016-01-01</p> <p>The invariance of the speed of light is one of the foundational pillars of our current understanding of the universe. It implies a series of consequences related to our perception of simultaneity and, ultimately, of time itself. Whereas these consequences are experimentally well studied in the case of subluminal motion, the kinematics of superluminal motion lack direct evidence or even a clear experimental approach. We investigate kinematic effects associated with the superluminal motion of a light <span class="hlt">source</span>. By using high-temporal-resolution imaging techniques, we directly demonstrate that if the <span class="hlt">source</span> approaches an <span class="hlt">observer</span> at superluminal speeds, the temporal ordering of events is inverted and its image appears to propagate backward. Moreover, for a <span class="hlt">source</span> changing its speed and crossing the interface between subluminal and superluminal propagation regions, we <span class="hlt">observe</span> image pair annihilation and creation, depending on the crossing direction. These results are very general and show that, regardless of the emitter speed, it is not possible to unambiguously determine the kinematics of an event from imaging and time-resolved measurements alone. This has implications not only for light, but also, for example, for sound and other wave phenomena. PMID:27152347</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012NIMPA.692..184A','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012NIMPA.692..184A"><span>Search for neutrinos from transient <span class="hlt">sources</span> with the ANTARES telescope and optical follow-up <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ageron, Michel; Al Samarai, Imen; Akerlof, Carl; Basa, Stéphane; Bertin, Vincent; Boer, Michel; Brunner, Juergen; Busto, Jose; Dornic, Damien; Klotz, Alain; Schussler, Fabian; Vallage, Bertrand; Vecchi, Manuela; Zheng, Weikang</p> <p>2012-11-01</p> <p>The ANTARES telescope is well suited to detect neutrinos produced in astrophysical transient <span class="hlt">sources</span> as it can <span class="hlt">observe</span> a full hemisphere of the sky at all the times with a duty cycle close to unity and an angular resolution better than 0.5°. Potential <span class="hlt">sources</span> include gamma-ray bursts (GRBs), core collapse supernovae (SNe), and flaring active galactic nuclei (AGNs). To enhance the sensitivity of ANTARES to such <span class="hlt">sources</span>, a new detection method based on coincident <span class="hlt">observations</span> of neutrinos and optical signals has been developed. A fast online muon track reconstruction is used to trigger a network of small automatic optical telescopes. Such alerts are generated one or two times per month for special events such as two or more neutrinos coincident in time and direction or single neutrinos of very high energy. Since February 2009, ANTARES has sent 37 alert triggers to the TAROT and ROTSE telescope networks, 27 of them have been followed. First results on the optical images analysis to search for GRBs are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1995PASJ...47..725I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1995PASJ...47..725I"><span>Search for High Rotation Measures in Extragalactic Radio <span class="hlt">Sources</span> I. Multi-Channel <span class="hlt">Observations</span> at 10 GHz</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Inoue, M.; Tabara, H.; Kato, T.; Aizu, K.</p> <p>1995-12-01</p> <p>Multi-channel polarimetry has been performed to detect high rotation measure (RM) at 3 cm using the Nobeyama 45-m telescope. The high RM candidates of 96 radio <span class="hlt">sources</span> were selected to be <span class="hlt">observed</span>, and RMs of 35 <span class="hlt">sources</span> were derived from the <span class="hlt">observations</span>. Since the four channels are set contiguously from 2.84 cm to 3.31 cm, |RM| can be derived uniquely up to 15000 rad m(-2) by this polarimeter. We found that there exist <span class="hlt">sources</span> with RM of several thousands rad m(-2) . In fact, 5 <span class="hlt">sources</span> have |RM| > 1000 rad m(-2) . On the other hand, all <span class="hlt">sources</span> <span class="hlt">observed</span> are well within this system limits, and therefore we suggest the <span class="hlt">observed</span> upper limit of |RM| is around 5000 rad m(-2) for extragalactic radio <span class="hlt">sources</span>, even taken into account the redshift of <span class="hlt">sources</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/6322972','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/6322972"><span><span class="hlt">Observations</span> of prolonged ionospheric anomalies following passage of an <span class="hlt">infrasound</span> pulse through the lower thermosphere</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Jacobson, A.R.; Carlos, R.C.</p> <p>1987-06-01</p> <p>We have studied the Doppler spectra of E-layer vertical-incidence HF soundings around the time of passage of a brief (duration approx.10 s) acoustic shock. Following the exit of the shock from the reflection volume, there occurred a several-minute episode of spectral derangement. We have analyzed this derangement in some detail and have related it to other studies of possibly the same phenomenon. 18 refs., 10 figs.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5047777','PMC'); return false;" href="https://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=5047777"><span>Neurodevelopmental Deceleration by Urban Fine Particles from Different Emission <span class="hlt">Sources</span>: A Longitudinal <span class="hlt">Observational</span> Study</span></a></p> <p><a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pmc">PubMed Central</a></p> <p>Basagaña, Xavier; Esnaola, Mikel; Rivas, Ioar; Amato, Fulvio; Alvarez-Pedrerol, Mar; Forns, Joan; López-Vicente, Mònica; Pujol, Jesús; Nieuwenhuijsen, Mark; Querol, Xavier; Sunyer, Jordi</p> <p>2016-01-01</p> <p>Background: A few studies have reported associations between traffic-related air pollution exposure at schools and cognitive development. The role of PM components or <span class="hlt">sources</span> other than traffic on cognitive development has been little explored. Objectives: We aimed to explore the role of PM <span class="hlt">sources</span> in school air on cognitive development. Methods: A cohort of 2,618 schoolchildren (average age, 8.5 years) belonging to 39 schools in Barcelona (Spain) was followed up for a year. Children completed computerized tests assessing working memory, superior working memory, and inattentiveness during four visits. Particulate matter ≤ 2.5 μm (PM2.5) was measured during two 1-week campaigns in each school, both outdoors and in the classroom. <span class="hlt">Source</span> apportionment resulted in nine <span class="hlt">sources</span>: mineral, organic/textile/chalk, traffic, secondary sulfate and organics, secondary nitrate, road dust, metallurgy, sea spray, and heavy oil combustion. Differences in cognitive growth trajectories were assessed with mixed models with age-by-<span class="hlt">source</span> interaction terms. Results: An interquartile range increase in indoor traffic-related PM2.5 was associated with reductions in cognitive growth equivalent to 22% (95% CI: 2%, 42%) of the annual change in working memory, 30% (95% CI: 6%, 54%) of the annual change in superior working memory, and 11% (95% CI: 0%, 22%) of the annual change in the inattentiveness scale. None of the other PM2.5 <span class="hlt">sources</span> was associated with adverse effects on cognitive development. Conclusions: Traffic was the only <span class="hlt">source</span> of fine particles associated with a reduction in cognitive development. Reducing air pollution from traffic at primary schools may result in beneficial effects on cognition. Citation: Basagaña X, Esnaola M, Rivas I, Amato F, Alvarez-Pedrerol M, Forns J, López-Vicente M, Pujol J, Nieuwenhuijsen M, Querol X, Sunyer J. 2016. Neurodevelopmental deceleration by urban fine particles from different emission <span class="hlt">sources</span>: a longitudinal <span class="hlt">observational</span> study. Environ</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009ACP.....9...39Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009ACP.....9...39Z"><span>Modeled and <span class="hlt">observed</span> ozone sensitivity to mobile-<span class="hlt">source</span> emissions in Mexico City</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zavala, M.; Lei, W.; Molina, M. J.; Molina, L. T.</p> <p>2009-01-01</p> <p>The emission characteristics of mobile <span class="hlt">sources</span> in the Mexico City Metropolitan Area (MCMA) have changed significantly over the past few decades in response to emission control policies, advancements in vehicle technologies and improvements in fuel quality, among others. Along with these changes, concurrent non-linear changes in photochemical levels and criteria pollutants have been <span class="hlt">observed</span>, providing a unique opportunity to understand the effects of perturbations of mobile emission levels on the photochemistry in the region using <span class="hlt">observational</span> and modeling approaches. The <span class="hlt">observed</span> historical trends of ozone (O3), carbon monoxide (CO) and nitrogen oxides (NOx) suggest that ozone production in the MCMA has changed from a low to a high VOC-sensitive regime over a period of 20 years. Comparison of the historical emission trends of CO, NOx and hydrocarbons derived from mobile-<span class="hlt">source</span> emission studies in the MCMA from 1991 to 2006 with the trends of the concentrations of CO, NOx, and the CO/NOx ratio during peak traffic hours also indicates that fuel-based fleet average emission factors have significantly decreased for CO and VOCs during this period whereas NOx emission factors do not show any strong trend, effectively reducing the ambient VOC/NOx ratio. This study presents the results of model analyses on the sensitivity of the <span class="hlt">observed</span> ozone levels to the estimated historical changes in its precursors. The model sensitivity analyses used a well-validated base case simulation of a high pollution episode in the MCMA with the mathematical Decoupled Direct Method (DDM) and the standard Brute Force Method (BFM) in the 3-D CAMx chemical transport model. The model reproduces adequately the <span class="hlt">observed</span> historical trends and current photochemical levels. Comparison of the BFM and the DDM sensitivity techniques indicates that the model yields ozone values that increase linearly with NOx emission reductions and decrease linearly with VOC emission reductions only up to 30% from the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2008ACPD....814991Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2008ACPD....814991Z"><span>Modeled and <span class="hlt">observed</span> ozone sensitivity to mobile-<span class="hlt">source</span> emissions in Mexico City</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zavala, M.; Lei, W. F.; Molina, M. J.; Molina, L. T.</p> <p>2008-08-01</p> <p>The emission characteristics of mobile <span class="hlt">sources</span> in the Mexico City Metropolitan Area (MCMA) have changed significantly over the past few decades in response to emission control policies, advancements in vehicle technologies and improvements in fuel quality, among others. Along with these changes, concurrent non-linear changes in photochemical levels and criteria pollutants have been <span class="hlt">observed</span>, providing a unique opportunity to understand the effects of perturbations of mobile emission levels on the photochemistry in the region using <span class="hlt">observational</span> and modeling approaches. The <span class="hlt">observed</span> historical trends of ozone (O3), carbon monoxide (CO) and nitrogen oxides (NOx) suggest that ozone production in the MCMA has changed from a low to a high VOC-sensitive regime over a period of 20 years. Comparison of the historical emission trends of CO, NOx and hydrocarbons derived from mobile-<span class="hlt">source</span> emission studies in the MCMA from 1991 to 2006 with the trends of the concentrations of CO, NOx, and the CO/NOx ratio during peak traffic hours also indicates that fuel-based fleet average emission factors have significantly decreased for CO and VOCs during this period whereas NOx emission factors do not show any strong trend, effectively reducing the ambient VOC/NOx ratio. This study presents the results of model analyses on the sensitivity of the <span class="hlt">observed</span> ozone levels to the estimated historical changes in its precursors. The model sensitivity analyses used a well-validated base case simulation of a high pollution episode in the MCMA with the mathematical Decoupled Direct Method (DDM) and the standard Brute Force Method (BFM) in the 3-D CAMx chemical transport model. The model reproduces adequately the <span class="hlt">observed</span> historical trends and current photochemical levels. Comparison of the BFM and the DDM sensitivity techniques indicates that the model yields ozone values that increase linearly with NOx emission reductions and decrease linearly with VOC emission reductions only up to 30% from the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20050092400&hterms=energy+shields+possible&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Denergy%2Bshields%2Bpossible','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20050092400&hterms=energy+shields+possible&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3Denergy%2Bshields%2Bpossible"><span>Using the EXIST Active Shields for Earth Occultation <span class="hlt">Observations</span> of X-Ray <span class="hlt">Sources</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Wilson, Colleen A.; Fishman, Gerald; Hong, Jae-Sub; Gridlay, Jonathan; Krawczynski, Henric</p> <p>2005-01-01</p> <p>The EXIST active shields, now being planned for the main detectors of the coded aperture telescope, will have approximately 15 times the area of the BATSE detectors; and they will have a good geometry on the spacecraft for viewing both the leading and training Earth's limb for occultation <span class="hlt">observations</span>. These occultation <span class="hlt">observations</span> will complement the imaging <span class="hlt">observations</span> of EXIST and can extend them to higher energies. Earth occultatio <span class="hlt">observations</span> of the hard X-ray sky with BATSE on the Compton Gamma Ray Observatory developed and demonstrated the capabilities of large, flat, uncollimated detectors for this method. With BATSE, a catalog of 179 X-ray <span class="hlt">sources</span> was monitored twice every spacecraft orbit for 9 years at energies above about 25 keV, resulting in 83 definite detections and 36 possible detections with 5-sigma detection sensitivities of 3.5-20 mcrab (20-430 keV) depending on the sky location. This catalog included four transients discovered with this technique and many variable objects (galactic and extragalactic). This poster will describe the Earth occultation technique, summarize the BATSE occultation <span class="hlt">observations</span>, and compare the basic <span class="hlt">observational</span> parameters of the occultation detector elements of BATSE and EXIST.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1985A%26A...143..292F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1985A%26A...143..292F"><span>Compact Steep Spectrum 3CR radio <span class="hlt">sources</span> - VLBI <span class="hlt">observations</span> at 18 CM</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Fanti, C.; Fanti, R.; Parma, P.; Schilizzi, R. T.; van Breugel, W. J. M.</p> <p>1985-02-01</p> <p>Results of a program to investigate the kiloparsec-sized radio structure of a representative sample of Compact Steep Spectrum (CSS) <span class="hlt">sources</span> from the 3CR catalog (Jenkins et al., 1977) are presented. Ten objects (3C49,67, 119, 237, 241, 268.3, 287, 303.1, 343, 343.1) have been mapped at 18 cm with a resolution of about 30 marcsec using the European VLBI Network. In some cases the VLBI data have been supplemented by MERLIN <span class="hlt">observations</span> at the same wavelength to enhance sensitivity to large-scale structure. The overall sizes of the CSS <span class="hlt">sources</span> range from about 0.1 to 1 or 2 arcsec, corresponding to linear sizes of the order of 1 to 10 kpc. The morphological classification ranges from double to core-jet to complex; CSS quasars are generally core-jets or complex, while CSS radio galaxies are doubles, although not necessarily simple doubles.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_17");'>17</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li class="active"><span>19</span></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_19 --> <div id="page_20" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="381"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21576553','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21576553"><span>CHANDRA <span class="hlt">OBSERVATION</span> OF THE TeV <span class="hlt">SOURCE</span> HESS J1834-087</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Misanovic, Zdenka; Kargaltsev, Oleg; Pavlov, George G. E-mail: oyk100@astro.ufl.edu</p> <p>2011-07-01</p> <p>Chandra ACIS <span class="hlt">observed</span> the field of the extended TeV <span class="hlt">source</span> HESS J1834-087 for 47 ks. A previous XMM-Newton EPIC <span class="hlt">observation</span> of the same field revealed a point-like <span class="hlt">source</span> (XMMU J183435.3-084443) and an offset region of faint extended emission. In the low-resolution, binned EPIC images the two appear to be connected. However, the high-resolution Chandra ACIS images do not support the alleged connection. In these images, XMMU J183435.3-084443 is resolved into a point <span class="hlt">source</span>, CXOU J183434.9-084443 (L{sub 0.5-8keV} {approx_equal} 2.3 x 10{sup 33} erg s{sup -1}, for a distance of 4 kpc; photon index {Gamma} {approx_equal} 1.1), and a compact ({approx}< 20'') nebula with an isotropic morphology and a softer spectrum (L{sub 0.5-8keV} {approx_equal} 4.1 x 10{sup 33} erg s{sup -1}, {Gamma} {approx_equal} 2.7). The nature of the nebula is uncertain. We discuss a dust scattering halo and a pulsar-wind nebula as possible interpretations. Based on our analysis of the X-ray data, we re-evaluate the previously suggested interpretations of HESS J1834-087 and discuss a possible connection to the Fermi Large Area Telescope <span class="hlt">source</span> 1FGL J1834.3-0842c. We also obtained an upper limit of 3 x 10{sup -14} erg cm{sup -2} s{sup -1} on the unabsorbed flux of the SGR J1833-0832 (in quiescence), which happened to be in the ACIS field of view.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.S43E..01S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.S43E..01S"><span>Estimating Earthquake <span class="hlt">Source</span> Parameters from P-wave Spectra: Lessons from Theory and <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Shearer, P. M.; Denolle, M.; Kaneko, Y.</p> <p>2015-12-01</p> <p><span class="hlt">Observations</span> make clear that some earthquakes radiate relatively more high frequency energy that others of the same moment. But translating these differences into traditional <span class="hlt">source</span> parameter measures, such as stress drop and radiated energy, can be problematic. Some of the issues include: (1) Because of directivity and other rupture propagation details, theoretical results show that recorded spectra will vary in shape among stations. <span class="hlt">Observational</span> studies often neglect this effect or assume it will average out when multiple stations are used, but this averaging is rarely perfect, particularly considering the narrow range of takeoff angles used in teleseismic studies. (2) Depth phases for shallow events create interference in the spectra that can severely bias spectral estimates, unless depth phases are taken into account. (3) Corner frequency is not a well-defined parameter and different methods for its computation will yield different results. In addition, stress drop estimates inferred from corner frequencies rely on specific theoretical rupture models, and different assumed crack geometries and rupture velocities will yield different stress drop values. (4) Attenuation corrections may be inaccurate or not fully reflect local 3D near-<span class="hlt">source</span> attenuation structure. The use of empirical Green's function (EGF) events can help, but these often have signal-to-noise issues or are not very close to the target earthquake. (5) Energy estimates typically rely on some degree of extrapolation of spectra beyond their <span class="hlt">observational</span> band, introducing model assumptions into what is intended to be a direct measure of an earthquake property. (6) P-wave spectra are analyzed much more than S-wave spectra because of their greater frequency content, but they only carry a small fraction of the total radiated seismic energy and thus total energy estimates may rely on poorly known Es/Ep scaling relations. We will discuss strategies to address these problems and to compute improved <span class="hlt">source</span></p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://pubs.er.usgs.gov/publication/70018972','USGSPUBS'); return false;" href="http://pubs.er.usgs.gov/publication/70018972"><span><span class="hlt">Observational</span> constraints on earthquake <span class="hlt">source</span> scaling: Understanding the limits in resolution</span></a></p> <p><a target="_blank" href="http://pubs.er.usgs.gov/pubs/index.jsp?view=adv">USGS Publications Warehouse</a></p> <p>Hough, S.E.</p> <p>1996-01-01</p> <p>I examine the resolution of the type of stress drop estimates that have been used to place <span class="hlt">observational</span> constraints on the scaling of earthquake <span class="hlt">source</span> processes. I first show that apparent stress and Brune stress drop are equivalent to within a constant given any <span class="hlt">source</span> spectral decay between ??1.5 and ??3 (i.e., any plausible value) and so consistent scaling is expected for the two estimates. I then discuss the resolution and scaling of Brune stress drop estimates, in the context of empirical Green's function results from recent earthquake sequences, including the 1992 Joshua Tree, California, mainshock and its aftershocks. I show that no definitive scaling of stress drop with moment is revealed over the moment range 1019-1025; within this sequence, however, there is a tendency for moderate-sized (M 4-5) events to be characterized by high stress drops. However, well-resolved results for recent M > 6 events are inconsistent with any extrapolated stress increase with moment for the aftershocks. Focusing on comer frequency estimates for smaller (M < 3.5) events, I show that resolution is extremely limited even after empirical Green's function deconvolutions. A fundamental limitation to resolution is the paucity of good signal-to-noise at frequencies above 60 Hz, a limitation that will affect nearly all surficial recordings of ground motion in California and many other regions. Thus, while the best available <span class="hlt">observational</span> results support a constant stress drop for moderate-to large-sized events, very little robust <span class="hlt">observational</span> evidence exists to constrain the quantities that bear most critically on our understanding of <span class="hlt">source</span> processes: stress drop values and stress drop scaling for small events.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/116295','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/116295"><span>Reduction of swimming time in mice through interaction of <span class="hlt">infrasound</span> and alcohol.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Lehmann, A G; Busnel, R G</p> <p>1979-09-01</p> <p>The effects of noise, alcohol, and the combination of the two were studied on muscular fatigue in several mouse strains to investigate a possible interaction between the two stresses. Muscular fatigue was measured by latency to submersion during a forced-swimming test. Animals were exposed to acoustic stimuli of fixed frequency and intensity for 2h preceding the test. Ethanol was administered orally from 30 min to 3h 30 min prior to testing. Alcohol doses and sound intensities were subliminal when administered separately. While no significant interaction occurred between alcohol and audible sound, the interaction between alcohol and <span class="hlt">infrasound</span> was highly significant indicating that their joint effects are more than merely additive. Blood alcohol measurements indicate that these interactive effects are prolonged for more than 2h after elimination of alcohol from the blood. Effects are similar in genetically deaf and hearing mice, implicating involvement of nonauditory pathways.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19770028845&hterms=1608&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3D%2526%25231608','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19770028845&hterms=1608&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3D%2526%25231608"><span>Uhuru <span class="hlt">observations</span> of 4U 1608-52 - The 'steady' X-ray <span class="hlt">source</span> associated with the X-ray burst <span class="hlt">source</span> in Norma</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Tananbaum, H.; Chaisson, L. J.; Forman, W.; Jones, C.; Matilsky, T. A.</p> <p>1976-01-01</p> <p>Data are presented for the X-ray <span class="hlt">source</span> 4U 1608-52, summarizing its light curve, location, and spectral parameters. Evidence is presented showing that this <span class="hlt">source</span> is the 'steady' X-ray counterpart of the X-ray burst <span class="hlt">source</span> in Norma. The spectrum of the 'steady' <span class="hlt">source</span> is compared with the spectrum <span class="hlt">observed</span> during two bursts, and it is noted that there is substantially more low-energy absorption during the bursts. The 'steady' <span class="hlt">source</span> spectral data are used to examine the optical data, and it is concluded that if the X-ray spectrum is thermal, then a globular-cluster counterpart probably would have been detected (whereas none has been). Further X-ray and optical <span class="hlt">observations</span> are suggested for this <span class="hlt">source</span>, since an optical identification may be central in determining whether all X-ray bursts have a common origin and if this origin requires a globular-cluster environment.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21560535','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21560535"><span>SEVEN-YEAR WILKINSON MICROWAVE ANISOTROPY PROBE (WMAP ) <span class="hlt">OBSERVATIONS</span>: PLANETS AND CELESTIAL CALIBRATION <span class="hlt">SOURCES</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Weiland, J. L.; Odegard, N.; Hill, R. S.; Greason, M. R.; Wollack, E.; Hinshaw, G.; Kogut, A.; Bennett, C. L.; Gold, B.; Larson, D.; Dunkley, J.; Halpern, M.; Komatsu, E.; Limon, M.; Meyer, S. S.; Nolta, M. R.; Smith, K. M.; Spergel, D. N.</p> <p>2011-02-01</p> <p>We present WMAP seven-year <span class="hlt">observations</span> of bright <span class="hlt">sources</span> which are often used as calibrators at microwave frequencies. Ten objects are studied in five frequency bands (23-94 GHz): the outer planets (Mars, Jupiter, Saturn, Uranus, and Neptune) and five fixed celestial <span class="hlt">sources</span> (Cas A, Tau A, Cyg A, 3C274, and 3C58). The seven-year analysis of Jupiter provides temperatures which are within 1{sigma} of the previously published WMAP five-year values, with slightly tighter constraints on variability with orbital phase (0.2% {+-} 0.4%), and limits (but no detections) on linear polarization. <span class="hlt">Observed</span> temperatures for both Mars and Saturn vary significantly with viewing geometry. Scaling factors are provided which, when multiplied by the Wright Mars thermal model predictions at 350 {mu}m, reproduce WMAP seasonally averaged <span class="hlt">observations</span> of Mars within {approx}2%. An empirical model is described which fits brightness variations of Saturn due to geometrical effects and can be used to predict the WMAP <span class="hlt">observations</span> to within 3%. Seven-year mean temperatures for Uranus and Neptune are also tabulated. Uncertainties in Uranus temperatures are 3%-4% in the 41, 61, and 94 GHz bands; the smallest uncertainty for Neptune is 8% for the 94 GHz band. Intriguingly, the spectrum of Uranus appears to show a dip at {approx}30 GHz of unidentified origin, although the feature is not of high statistical significance. Flux densities for the five selected fixed celestial <span class="hlt">sources</span> are derived from the seven-year WMAP sky maps and are tabulated for Stokes I, Q, and U, along with polarization fraction and position angle. Fractional uncertainties for the Stokes I fluxes are typically 1% to 3%. <span class="hlt">Source</span> variability over the seven-year baseline is also estimated. Significant secular decrease is seen for Cas A and Tau A: our results are consistent with a frequency-independent decrease of about 0.53% per year for Cas A and 0.22% per year for Tau A. We present WMAP polarization data with uncertainties of a</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009JGRD..114.8112L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009JGRD..114.8112L"><span>Assessing the performance of the International Monitoring System's <span class="hlt">infrasound</span> network: Geographical coverage and temporal variabilities</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Le Pichon, A.; Vergoz, J.; Blanc, E.; Guilbert, J.; Ceranna, L.; Evers, L.; Brachet, N.</p> <p>2009-04-01</p> <p>A global-scale analysis of detections made at all 36 currently operating International Monitoring System (IMS) <span class="hlt">infrasound</span> arrays confirms that the primary factor controlling signal detectability is the seasonal variability of the stratospheric zonal wind. At most arrays, ˜80% of the detections in the 0.2- to 2-Hz bandpass are associated with propagation downwind of the dominant stratospheric wind direction. Previous IMS <span class="hlt">infrasound</span> network performance models neglect the time- and site-dependent effects of both stratospheric meteorological variability and ambient noise models. In this study both effects are incorporated; we compare empirical and improved specifications of the stratospheric wind and include station-dependent wind noise models. Using a deterministic approach, the influence of individual model parameters on the network performance is systematically assessed. At frequencies of interest for detecting atmospheric explosions (0.2-2 Hz), the simulations predict that explosions equivalent to ˜500 t of TNT would be detected by at least two stations at any time of the year. The detection capability is best around January and July when stratospheric winds are strongest, compared to the equinox periods when zonal winds reduce and reverse. The model predicts that temporal fluctuations in the ground-to-stratosphere meteorological variables generate detection threshold variations on daily and seasonal timescales of ˜50 and ˜500 t, respectively. While the strong zonal winds lead to an improvement in detection capability, their highly directional nature leads to an increase in the location uncertainty owing to the decreased azimuthal separation of the detecting stations.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22047654','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22047654"><span>ALMA <span class="hlt">OBSERVATIONS</span> OF THE OUTFLOW FROM <span class="hlt">SOURCE</span> I IN THE ORION-KL REGION</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Zapata, Luis A.; Rodriguez, Luis F.; Loinard, Laurent; Schmid-Burgk, Johannes; Menten, Karl M.; Curiel, Salvador</p> <p>2012-07-20</p> <p>In this Letter, we present sensitive millimeter SiO (J = 5-4; {nu} = 0) line <span class="hlt">observations</span> of the outflow arising from the enigmatic object Orion <span class="hlt">Source</span> I made with the Atacama Large Millimeter/Submillimeter Array (ALMA). The <span class="hlt">observations</span> reveal that at scales of a few thousand AU, the outflow has a marked 'butterfly' morphology along a northeast-southwest axis. However, contrary to what is found in the SiO and H{sub 2}O maser <span class="hlt">observations</span> at scales of tens of AU, the blueshifted radial velocities of the moving gas are found to the northwest, while the redshifted velocities are in the southeast. The ALMA <span class="hlt">observations</span> are complemented with SiO (J = 8-7; {nu} = 0) maps (with a similar spatial resolution) obtained with the Submillimeter Array. These <span class="hlt">observations</span> also show a similar morphology and velocity structure in this outflow. We discuss some possibilities to explain these differences at small and large scales across the flow.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2017ApJ...836..117I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2017ApJ...836..117I"><span>CO Spectral Line Energy Distributions in Galactic <span class="hlt">Sources</span>: Empirical Interpretation of Extragalactic <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Indriolo, Nick; Bergin, E. A.; Goicoechea, J. R.; Cernicharo, J.; Gerin, M.; Gusdorf, A.; Lis, D. C.; Schilke, P.</p> <p>2017-02-01</p> <p>The relative populations in rotational transitions of CO can be useful for inferring gas conditions and excitation mechanisms at work in the interstellar medium. We present CO emission lines from rotational transitions <span class="hlt">observed</span> with Herschel/HIFI in the star-forming cores Orion S, Orion KL, Sgr B2(M), and W49N. Integrated line fluxes from these <span class="hlt">observations</span> are combined with those from Herschel/PACS <span class="hlt">observations</span> of the same <span class="hlt">sources</span> to construct CO spectral line energy distributions (SLEDs) from 5 ≤ J u ≤ 48. These CO SLEDs are compared to those reported in other galaxies, with the intention of empirically determining which mechanisms dominate excitation in such systems. We find that CO SLEDs in Galactic star-forming cores cannot be used to reproduce those <span class="hlt">observed</span> in other galaxies, although the discrepancies arise primarily as a result of beam filling factors. The much larger regions sampled by the Herschel beams at distances of several megaparsecs contain significant amounts of cooler gas, which dominate the extragalactic CO SLEDs, in contrast to <span class="hlt">observations</span> of Galactic star-forming regions, which are focused specifically on cores containing primarily hot molecular gas. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19910022962&hterms=tempo&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dtempo','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19910022962&hterms=tempo&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3Dtempo"><span>JPL 1990-3: A 5-nrad extragalactic <span class="hlt">source</span> catalog based on combined radio interferometric <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Sovers, O. J.</p> <p>1991-01-01</p> <p>A combined analysis merges 17,000 Deep Space Network (DSN) Very Long Baseline Interferometric (VLBI) <span class="hlt">observations</span> with 303,000 <span class="hlt">observations</span> from the Crustal Dynamics Project (CDP) and the International Radio Interferometric Surveying (IRIS) project. <span class="hlt">Observations</span> from the Radio Reference Frame Development (RRFD) and Time and Earth Motion Precision <span class="hlt">Observations</span> (TEMPO) programs through late 1990 form the DSN VLBI data set. The combined analysis yields angular coordinates of extragalactic radio <span class="hlt">sources</span> with a precision of a few nanoradians, as compared with 5 to 10 nrad precision for coordinates derived in the past solely from DSN data. The improvement in the combined analysis is due to the new Mark III DSN data, as well as to increased statistical strength from the large volume of <span class="hlt">observations</span> from non-DSN experiments. Such a unified analysis is made possible by recent improvements in parameter estimation software efficiency. The terrestrial reference frame is based on joint VLBI experiments using both DSN and CDP antennas, and on specifying the coordinates of VLBI antennas in a proper geocentric coordinate system by means of Global Positioning System (GPS) collocation of VLBI, LLR, and SLR (Laser Ranging) sites.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/22243063','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/22243063"><span><span class="hlt">Observational</span> constraints on multimessenger <span class="hlt">sources</span> of gravitational waves and high-energy neutrinos.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Bartos, Imre; Finley, Chad; Corsi, Alessandra; Márka, Szabolcs</p> <p>2011-12-16</p> <p>Many astronomical <span class="hlt">sources</span> of intense bursts of photons are also predicted to be strong emitters of gravitational waves (GWs) and high-energy neutrinos (HENs). Moreover some suspected classes, e.g., choked gamma-ray bursts, may only be identifiable via nonphoton messengers. Here we explore the reach of current and planned experiments to address this question. We derive constraints on the rate of GW and HEN bursts based on independent <span class="hlt">observations</span> by the initial LIGO and Virgo GW detectors and the partially completed IceCube (40-string) HEN detector. We then estimate the reach of joint GW+HEN searches using advanced GW detectors and the completed km(3) IceCube detector to probe the joint parameter space. We show that searches undertaken by advanced detectors will be capable of detecting, constraining, or excluding, several existing models with 1 yr of <span class="hlt">observation</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015OcMod..96....2Z','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015OcMod..96....2Z"><span><span class="hlt">Observation</span>-based <span class="hlt">source</span> terms in the third-generation wave model WAVEWATCH</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Zieger, Stefan; Babanin, Alexander V.; Erick Rogers, W.; Young, Ian R.</p> <p>2015-12-01</p> <p>Measurements collected during the AUSWEX field campaign, at Lake George (Australia), resulted in new insights into the processes of wind wave interaction and whitecapping dissipation, and consequently new parameterizations of the input and dissipation <span class="hlt">source</span> terms. The new nonlinear wind input term developed accounts for dependence of the growth on wave steepness, airflow separation, and for negative growth rate under adverse winds. The new dissipation terms feature the inherent breaking term, a cumulative dissipation term and a term due to production of turbulence by waves, which is particularly relevant for decaying seas and for swell. The latter is consistent with the <span class="hlt">observed</span> decay rate of ocean swell. This paper describes these <span class="hlt">source</span> terms implemented in WAVEWATCH III ®and evaluates the performance against existing <span class="hlt">source</span> terms in academic duration-limited tests, against buoy measurements for windsea-dominated conditions, under conditions of extreme wind forcing (Hurricane Katrina), and against altimeter data in global hindcasts. Results show agreement by means of growth curves as well as integral and spectral parameters in the simulations and hindcast.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20070017443','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20070017443"><span>Suzaku <span class="hlt">Observation</span> of Two Ultraluminous X-ray <span class="hlt">Sources</span> in NGC 1313</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mizuno, T.; Miyawaki, R.; Ebisawa, K.; Kubota, A.; Miyamoto, M.; Winter, L.; Ueda, Y.; Isobe, N.; Dewangan, G.; Mushotzky, R.F.; Petre, R.</p> <p>2007-01-01</p> <p>TA study was made of two ultraluminous X-ray <span class="hlt">sources</span> (ULXs) in the nearby faceon, late-type Sb galaxy NGC 1313 using data from Suzaku, the 5th Japanese X-ray satellite. Within the 90 ks <span class="hlt">observation</span>, both <span class="hlt">sources</span> named X-1 and X-2 exhibited luminosity change by about 50%. The o.4-10keV X-ray luminosity was measured. For X-1, the spectrum exhibited a strong power-law component with a high energy cutoff which is thought to arise from strong Comptonization by a disk corona, suggesting the <span class="hlt">source</span> was in a very high state. Absorption line features with equivalent widths of 40-80 eV found at 7.00 keV and 7.8 keV in the X-1 spectrum support the presence of a highly ionized plasma and a high mass accretion rate on the system. The spectrum of X-2 in fainter phase is presented by a multicolor disk blackbody model.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/23953054','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/23953054"><span>Tundra ecosystems <span class="hlt">observed</span> to be CO2 <span class="hlt">sources</span> due to differential amplification of the carbon cycle.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Belshe, E F; Schuur, E A G; Bolker, B M</p> <p>2013-10-01</p> <p>Are tundra ecosystems currently a carbon <span class="hlt">source</span> or sink? What is the future trajectory of tundra carbon fluxes in response to climate change? These questions are of global importance because of the vast quantities of organic carbon stored in permafrost soils. In this meta-analysis, we compile 40 years of CO2 flux <span class="hlt">observations</span> from 54 studies spanning 32 sites across northern high latitudes. Using time-series analysis, we investigated if seasonal or annual CO2 fluxes have changed over time, and whether spatial differences in mean annual temperature could help explain temporal changes in CO2 flux. Growing season net CO2 uptake has definitely increased since the 1990s; the data also suggest (albeit less definitively) an increase in winter CO2 emissions, especially in the last decade. In spite of the uncertainty in the winter trend, we estimate that tundra sites were annual CO2 <span class="hlt">sources</span> from the mid-1980s until the 2000s, and data from the last 7 years show that tundra continue to emit CO2 annually. CO2 emissions exceed CO2 uptake across the range of temperatures that occur in the tundra biome. Taken together, these data suggest that despite increases in growing season uptake, tundra ecosystems are currently CO2 <span class="hlt">sources</span> on an annual basis.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21255150','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21255150"><span>X-ray follow-up <span class="hlt">observations</span> of unidentified VHE {gamma}-ray <span class="hlt">sources</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Puehlhofer, Gerd</p> <p>2008-12-24</p> <p>A large fraction of the recently discovered Galactic Very High Energy (VHE) <span class="hlt">source</span> population remains unidentified to date. VHE {gamma}-ray emission traces high energy particles in these <span class="hlt">sources</span>, but for example in case of hadronic processes also the gas density at the emission site. Moreover, the particles have sufficiently long lifetimes to be able to escape from their acceleration sites. Therefore, the {gamma}-ray <span class="hlt">sources</span> or at least the areas of maximum surface brightness are in many cases spatially offset from the actual accelerators. A promising way to identify the objects in which the particles are accelerated seems to be to search for emission signatures of the acceleration process (like emission from shock-heated plasma). Also the particles themselves (through primary or secondary synchrotron emission) can be traced in lower wavebands. Those signatures are best visible in the X-ray band, and current X-ray observatories are well suited to conduct such follow-up <span class="hlt">observations</span>. Some aspects of the current status of these investigations are reviewed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MNRAS.463.3115T','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MNRAS.463.3115T"><span>LENSED: a code for the forward reconstruction of lenses and <span class="hlt">sources</span> from strong lensing <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Tessore, Nicolas; Bellagamba, Fabio; Metcalf, R. Benton</p> <p>2016-12-01</p> <p>Robust modelling of strong lensing systems is fundamental to exploit the information they contain about the distribution of matter in galaxies and clusters. In this work, we present LENSED, a new code which performs forward parametric modelling of strong lenses. LENSED takes advantage of a massively parallel ray-tracing kernel to perform the necessary calculations on a modern graphics processing unit (GPU). This makes the precise rendering of the background lensed <span class="hlt">sources</span> much faster, and allows the simultaneous optimization of tens of parameters for the selected model. With a single run, the code is able to obtain the full posterior probability distribution for the lens light, the mass distribution and the background <span class="hlt">source</span> at the same time. LENSED is first tested on mock images which reproduce realistic space-based <span class="hlt">observations</span> of lensing systems. In this way, we show that it is able to recover unbiased estimates of the lens parameters, even when the <span class="hlt">sources</span> do not follow exactly the assumed model. Then, we apply it to a subsample of the Sloan Lens ACS Survey lenses, in order to demonstrate its use on real data. The results generally agree with the literature, and highlight the flexibility and robustness of the algorithm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/1087682','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/1087682"><span>An Optical Streak Diagnostic for <span class="hlt">Observing</span> Anode-Cathode Plasmas for Radiographic <span class="hlt">Source</span> Development</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Droemer, Darryl W.; Crain, Marlon D.; Lare, Gregory A.; Bennett, Nichelle L.; Johnston, Mark D.</p> <p>2013-06-13</p> <p>National Security Technologies, LLC, and Sandia National Laboratories are collaborating in the development of pulsed power–driven flash x-ray radiographic <span class="hlt">sources</span> that utilize high-intensity electron beam diodes. The RITS 6 (Radiographic Integrated Test Stand) accelerator at Sandia is used to drive a self magnetic pinch diode to produce a Bremsstrahlung x-ray <span class="hlt">source</span>. The high electric fields and current densities associated with these short A-K gap pinch beam diodes present many challenges in diode development. Plasmas generated at both the anode and cathode affect the diode performance, which is manifested in varying spot (<span class="hlt">source</span>) sizes, total dose output, and impedance profiles. Understanding the nature of these plasmas including closure rates and densities is important in modeling their behavior and providing insight into their mitigation. In this paper we describe a streak camera–based optical diagnostic that is capable of <span class="hlt">observing</span> and measuring plasma evolution within the A-K gap. By imaging a region of interest onto the input slit of a streak camera, we are able to produce a time-resolved one-dimensional image of the evolving plasma. Typical data are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040111407&hterms=robert+yin&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Drobert%2Byin','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040111407&hterms=robert+yin&qs=N%3D0%26Ntk%3DAll%26Ntx%3Dmode%2Bmatchall%26Ntt%3Drobert%2Byin"><span><span class="hlt">Sources</span> of Tropospheric Ozone along the Asian Pacific Rim: An Analysis of Ozonesonde <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Liu, Hong-Yu; Jacob, Daniel J.; Chan, Lo Yin; Oltmans, Samuel J.; Bey, Isabelle; Yantosca, Robert M.; Harris, Joyce M.; Duncan, Bryan N.; Martin, Randall V.</p> <p>2002-01-01</p> <p>The <span class="hlt">sources</span> contributing to tropospheric ozone over the Asian Pacific Rim in different seasons are quantified by analysis of Hong Kong and Japanese ozonesonde <span class="hlt">observations</span> with a global three-dimensional (3-D) chemical transport model (GEOS-CHEM) driven by assimilated meteorological <span class="hlt">observations</span>. Particular focus is placed on the extensive <span class="hlt">observations</span> available from Hong Kong in 1996. In the middle-upper troposphere (MT- UT), maximum Asian pollution influence along the Pacific Rim occurs in summer, reflecting rapid convective transport of surface pollution. In the lower troposphere (LT) the season of maximum Asian pollution influence shifts to summer at midlatitudes from fall at low latitudes due to monsoonal influence. The UT ozone minimum and high variability <span class="hlt">observed</span> over Hong Kong in winter reflects frequent tropical intrusions alternating with stratospheric intrusions. Asian biomass burning makes a major contribution to ozone at less than 32 deg.N in spring. Maximum European pollution influence (less than 5 ppbv) occurs in spring in the LT. North American pollution influence exceeds European influence in the UT-MT, reflecting the uplift from convection and the warm conveyor belts over the eastern seaboard of North America. African outflow makes a major contribution to ozone in the low-latitude MT-UT over the Pacific Rim during November- April. Lightning influence over the Pacific Rim is minimum in summer due to westward UT transport at low latitudes associated with the Tibetan anticyclone. The Asian outflow flux of ozone to the Pacific is maximum in spring and fall and includes a major contribution from Asian anthropogenic <span class="hlt">sources</span> year-round.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ISPAr41B8..117M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ISPAr41B8..117M"><span>Near Real-Time Determination of Earthquake <span class="hlt">Source</span> Parameters for Tsunami Early Warning from Geodetic <span class="hlt">Observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Manneela, Sunanda; Srinivasa Kumar, T.; Nayak, Shailesh R.</p> <p>2016-06-01</p> <p>Exemplifying the tsunami <span class="hlt">source</span> immediately after an earthquake is the most critical component of tsunami early warning, as not every earthquake generates a tsunami. After a major under sea earthquake, it is very important to determine whether or not it has actually triggered the deadly wave. The near real-time <span class="hlt">observations</span> from near field networks such as strong motion and Global Positioning System (GPS) allows rapid determination of fault geometry. Here we present a complete processing chain of Indian Tsunami Early Warning System (ITEWS), starting from acquisition of geodetic raw data, processing, inversion and simulating the situation as it would be at warning center during any major earthquake. We determine the earthquake moment magnitude and generate the centroid moment tensor solution using a novel approach which are the key elements for tsunami early warning. Though the well established seismic monitoring network, numerical modeling and dissemination system are currently capable to provide tsunami warnings to most of the countries in and around the Indian Ocean, the study highlights the critical role of geodetic <span class="hlt">observations</span> in determination of tsunami <span class="hlt">source</span> for high-quality forecasting.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19960010533','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19960010533"><span>Detectability of electrostatic decay products in Ulysses and Galileo <span class="hlt">observations</span> of type 3 solar radio <span class="hlt">sources</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cairns, Iver H.</p> <p>1995-01-01</p> <p>Recent in situ Ulysses and Galileo <span class="hlt">observations</span> of the <span class="hlt">source</span> regions of type 3 solar radio bursts appear to show an absence of ion acoustic waves S produced by nonlinear Langmuir wave processes such as the electrostatic (ES) decay, in contradiction with earlier ISEE 3 <span class="hlt">observations</span> and analytic theory. This letter resolves these apparent contradictions. Refined analyses of the maximum S-wave electric fields produced by ES decay and of the characteristics of the Ulysses Wave Form Analyzer (WFA) instrument show that the bursty S waves <span class="hlt">observed</span> by the ISEE 3 should be essentially undetectable by the Ulysses WFA. It is also shown that the maximum S-wave levels predicted for the Galileo event are approximately less than the instrumental noise level, thereby confirming an earlier suggestion. Thus, no contradictions exist between the ISEE 3 and Ulysses/Galileo <span class="hlt">observation</span>, and no evidence exists against ES decay in the published Ulysses and Galileo data. All available data are consistent with, or at worst not inconsistent with, the ES decay proceeding and being the dominant nonlinear process in type 3 bursts.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_18");'>18</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li class="active"><span>20</span></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_20 --> <div id="page_21" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="401"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20000032748','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20000032748"><span>ASCA <span class="hlt">Observations</span> of "Type 2" LINERs Evidence for a Stellar <span class="hlt">Source</span> of Ionization</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Terashima, Yuichi; Ho, Luis C.; Ptak, Andrew F.; Mushotzky, Richard F.; Serlemitsos, Peter J.; Yaqoob, Tahir; Kunieda, Hideyo</p> <p>1999-01-01</p> <p>We present ASCA <span class="hlt">observations</span> of LINERs without broad H.alpha emission in their optical spectra. The sample of "type 2" LINERs consists of NGC 404, 4111, 4192, 4457, and 4569. We have detected X-ray emission from all the objects except for NGC 404; among the detected objects are two so-called transition objects (NGC 4192 and NGC 4569), which have been postulated to be composite nuclei having both an H II region and a LINER component. The images of NGC 4111 and NGC 4569 in the soft (0.5-2 keV) and hard (2-7 keV) X-ray bands are extended on scales of several kpc. The X-ray spectra of NGC 4111, NGC 4457 and NGC 4569 are well fitted by a two-component model that consists of soft thermal emission with kT approximately 0.65 keV and a hard component represented by a power law (photon index approximately 2) or by thermal bremsstrahlung emission (kT approximately several keV). The extended hard X-rays probably come from discrete <span class="hlt">sources</span>, while the soft emission most likely originates from hot gas produced by active star formation in the host galaxy. We have found no clear evidence for the presence of active galactic nuclei (AGNs) in the sample. Using black hole masses estimated from host galaxy bulge luminosities, we obtain an upper limit on the implied Eddington ratios less than 5 x 10(exp -5). If an AGN component is the primary ionization <span class="hlt">source</span> of the optical emission lines, then it must be heavily obscured with a column density significantly larger than 10(exp 23)/sq cm, since the <span class="hlt">observed</span> X-ray luminosity is insufficient to drive the luminosities of the optical emission lines. Alternatively, the optical emission could be ionized by a population of exceptionally hot stars. This interpretation is consistent with the small [O I] lambda6300/H.alpha ratios <span class="hlt">observed</span> in these <span class="hlt">sources</span>, the ultraviolet spectral characteristics in the cases where such information exists, and the X-ray results reported here. We also analyze the X-ray properties of NGC 4117, a low</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015RvGeo..53..545N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015RvGeo..53..545N"><span>A review of tropical cyclone-generated storm surges: Global data <span class="hlt">sources</span>, <span class="hlt">observations</span>, and impacts</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Needham, Hal F.; Keim, Barry D.; Sathiaraj, David</p> <p>2015-06-01</p> <p>Tropical cyclone-generated storm surges are among the world's most deadly and destructive natural hazards. This paper provides the first comprehensive global review of tropical storm surge data <span class="hlt">sources</span>, <span class="hlt">observations</span>, and impacts while archiving data in SURGEDAT, a global database. Available literature has provided data for more than 700 surge events since 1880, the majority of which are found in the western North Atlantic (WNA), followed by Australia/Oceania, the western North Pacific (WNP), and the northern Indian Ocean (NIO). The Bay of Bengal (BOB) in the NIO consistently <span class="hlt">observes</span> the world's highest surges, as this subbasin averages five surges ≥5 m per decade and has <span class="hlt">observed</span> credible storm tide levels reaching 13.7 m. The WNP <span class="hlt">observes</span> the highest rate of low-magnitude surges, as the coast of China averages 54 surges ≥1 m per decade, and rates are likely higher in the Philippines. The U.S. Gulf Coast <span class="hlt">observes</span> the second highest frequency of both high-magnitude (≥5 m) and low-magnitude (≥1 m) surges. The BOB <span class="hlt">observes</span> the most catastrophic surge impacts, as 59% of global tropical cyclones that have killed at least 5000 people occurred in this basin. The six deadliest cyclones in this region have each killed at least 140,000 people, and two events have killed 300,000. Storm surge impacts transportation, agriculture, and energy sectors in the WNA. Oceania experiences long-term impacts, including contamination of fresh water and loss of food supplies, although the highest surges in this region are lower than most other basins.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SPIE.9306E..0JE','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SPIE.9306E..0JE"><span>Apices of maxillary premolars <span class="hlt">observed</span> by swept <span class="hlt">source</span> optical coherence tomography</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ebihara, Arata; Iino, Yoshiko; Yoshioka, Toshihiko; Hanada, Takahiro; Sunakawa, Mitsuhiro; Sumi, Yasunori; Suda, Hideaki</p> <p>2015-02-01</p> <p>Apicoectomy is performed for the management of apical periodontitis when orthograde root canal treatment is not possible or is ineffective. Prior to the surgery, cone beam computed tomography (CBCT) examination is often performed to evaluate the lesion and the adjacent tissues. During the surgical procedure, the root apex is resected and the resected surface is usually <span class="hlt">observed</span> under dental operating microscope (DOM). However, it is difficult to evaluate the details and the subsurface structure of the root using CBCT and DOM. A new diagnostic system, swept <span class="hlt">source</span> optical coherence tomography (SS-OCT), has been developed to <span class="hlt">observe</span> the subsurface anatomical structure. The aim of this study was to <span class="hlt">observe</span> resected apical root canals of human maxillary premolars using SS-OCT and compare the findings with those <span class="hlt">observed</span> using CBCT and DOM. Six extracted human maxillary premolars were used. After microfocus computed tomography (Micro CT; for gold standard) and CBCT scanning of the root, 1 mm of the apex was cut perpendicular to the long axis of the tooth. Each resected surface was treated with EDTA, irrigated with saline solution, and stained with methylene blue dye. The resected surface was <span class="hlt">observed</span> with DOM and SS-OCT. This sequence was repeated three times. The number of root canals was counted and statistically evaluated. There was no significant difference in the accuracy of detecting root canals among CBCT, DOM and SS-OCT (p > 0.05, Wilcoxon test). Because SS-OCT can be used in real time during surgery, it would be a useful tool for <span class="hlt">observing</span> resected apical root canals.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ISPAr39B4...19P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ISPAr39B4...19P"><span>Coastal Ocean <span class="hlt">Observing</span> Network - Open <span class="hlt">Source</span> Architecture for Data Management and Web-Based Data Services</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pattabhi Rama Rao, E.; Venkat Shesu, R.; Udaya Bhaskar, T. V. S.</p> <p>2012-07-01</p> <p>The <span class="hlt">observations</span> from the oceans are the backbone for any kind of operational services, viz. potential fishing zone advisory services, ocean state forecast, storm surges, cyclones, monsoon variability, tsunami, etc. Though it is important to monitor open Ocean, it is equally important to acquire sufficient data in the coastal ocean through coastal ocean <span class="hlt">observing</span> systems for re-analysis, analysis and forecast of coastal ocean by assimilating different ocean variables, especially sub-surface information; validation of remote sensing data, ocean and atmosphere model/analysis and to understand the processes related to air-sea interaction and ocean physics. Accurate information and forecast of the state of the coastal ocean at different time scales is vital for the wellbeing of the coastal population as well as for the socio-economic development of the country through shipping, offshore oil and energy etc. Considering the importance of ocean <span class="hlt">observations</span> in terms of understanding our ocean environment and utilize them for operational oceanography, a large number of platforms were deployed in the Indian Ocean including coastal observatories, to acquire data on ocean variables in and around Indian Seas. The coastal <span class="hlt">observation</span> network includes HF Radars, wave rider buoys, sea level gauges, etc. The surface meteorological and oceanographic data generated by these <span class="hlt">observing</span> networks are being translated into ocean information services through analysis and modelling. Centralized data management system is a critical component in providing timely delivery of Ocean information and advisory services. In this paper, we describe about the development of open-<span class="hlt">source</span> architecture for real-time data reception from the coastal <span class="hlt">observation</span> network, processing, quality control, database generation and web-based data services that includes on-line data visualization and data downloads by various means.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016EGUGA..18.1187F','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016EGUGA..18.1187F"><span>MELODIST - An open-<span class="hlt">source</span> MEteoroLOgical <span class="hlt">observation</span> time series DISaggregation Tool</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Förster, Kristian; Hanzer, Florian; Winter, Benjamin; Marke, Thomas; Strasser, Ulrich</p> <p>2016-04-01</p> <p>Automatic weather station recordings at sub-daily time steps are being used as input data for various applications in many disciplines such as hydrology or ecology. Evaluations at sub-daily time steps for multi-decadal periods are thereby of great interest due to their climatological representativeness. However, the availability of continuous hourly meteorological time series is restricted to a small number of decades with records covering the full length of three decades being an exception. In contrast, daily <span class="hlt">observations</span> are available with much better spatial and temporal coverage, i.e. higher network density and longer, multi-decadal records. To benefit from the huge amount of available daily meteorological <span class="hlt">observations</span> worldwide, disaggregation methods are suitable tools to derive, e.g., hourly out of daily time series. We present an open-<span class="hlt">source</span> software package, written in Python, that can be used to fill the gap between the advantages of daily time series and methods requiring time series of the meteorological variables with higher temporal resolution. MELODIST (MEteoroLOgical <span class="hlt">observation</span> time series DISaggregation Tool) includes methods to independently disaggregate the most relevant meteorological variables including (i) precipitation, (ii) temperature, (iii) humidity, (iv) wind speed, and (v) radiation data for a given location. This poster gives a brief review of the available methods applicable for each variable, and also provides a sample application and insights on model performance.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20070016014','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20070016014"><span>Suzaku <span class="hlt">Observation</span> of Two Ultraluminous X-Ray <span class="hlt">Sources</span> in NGC 1313</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Mizuno, T.; Miyawaki, R.; Ebisawa, K.; Kubota, A.; Miyamoto, M.; Winter, L.; Ueda, Y.; Isobe, N.; Dewangan, G.; Done, C.; Griffiths, R. E.; Haba, Y.; Kokubun, M.; Kotoku J.; Makishima, K.; Matsushita, K.; Mushotzky, R. F.; Namiki, M.; Petre, R.; Takahashi, H.; Tamagaw, T.; Terashima, Y.</p> <p>2001-01-01</p> <p>A study was made of two ultraluminous X-ray soures (ULXs) in the nearby face-on, late-type Sb galaxy NGC 1313 using data from Suzaku, the 5th Japanese X-ray satellite. Within the 90 ks <span class="hlt">observation</span>, both <span class="hlt">sources</span> named X-1 and X-2 exhibited luminosity change by about 50%. The 0.4-10 keV X-ray luminosity was measured to be 2.5 x 10(exp 40) erg per second and 5.8 x 10 erg per second for X-1 and X-2, respectively, requiring a black hole of 50-200 solar mass in order not to exceed the Eddingtion limit. For X-1: the spectrum exhibited a strong power-law component with a high energy cutoff which is thought to arise from strong Comptonization by a disk corona, suggesting the <span class="hlt">source</span> was in a very high state. Absorption line features with equivalent widths of 40-80 eV found at 7.0 keV and 7.8 keV in the X-1 spectrum support the presence of a highly ionized plasma and a high mass accretion rate on the system. Oxygen abundance of the NGC 1313 circumstellar matter toward X-1 was found to be subsolar, viz. O/H = (5.0 plus or minus 1.0) x 10(exp -4). The spectrum of X-2 in fainter phase is best represented by a multicolor disk blackbody model with T (sub in) = 1.2-1.3 keV and becomes flatter as the flux increases; the <span class="hlt">source</span> is interpreted to be in a slim disk state.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...833..219P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...833..219P"><span>ALMA <span class="hlt">Observations</span> of Orion <span class="hlt">Source</span> I at 350 and 660 GHz</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Plambeck, R. L.; Wright, M. C. H.</p> <p>2016-12-01</p> <p>Orion <span class="hlt">Source</span> I (“SrcI”) is the protostar at the center of the Kleinmann-Low Nebula. ALMA <span class="hlt">observations</span> of SrcI with 0.″2 angular resolution were made at 350 and 660 GHz to search for the H26α and H21α hydrogen recombination lines and to measure the continuum flux densities. The recombination lines were not detected, ruling out the possibility that SrcI is a hypercompact H ii region. The deconvolved size of the continuum <span class="hlt">source</span> is approximately 0.″23 × 0.″07 (˜100 × 30 au); it is interpreted as a disk viewed almost edge-on. Optically thick thermal emission from ˜500 K dust is the most plausible <span class="hlt">source</span> of the continuum, even at frequencies as low as 43 GHz; the disk mass is most likely in the range 0.02-0.2 {M}⊙ . A rich spectrum of molecular lines is detected, mostly from sulfur- and silicon-rich molecules like SO, SO2, and SiS, but also including vibrationally excited CO and several unidentified transitions. Lines with upper energy levels {E}{{U}}\\gt 500 K appear in emission and are symmetric about the source’s LSR velocity of 5 {km} {{{s}}}-1, while lines with {E}{{U}}\\lt 500 K appear as blueshifted absorption features against the continuum, indicating that they originate in outflowing gas. The emission lines exhibit a velocity gradient along the major axis of the disk that is consistent with rotation around a 5-7 {M}⊙ central object. The relatively low mass of SrcI and the existence of a 100 au disk around it are difficult to reconcile with the model in which SrcI and the nearby Becklin-Neugebauer Object were ejected from a multiple system 500 years ago.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhRvX...4d1004M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhRvX...4d1004M"><span><span class="hlt">Source</span> Redshifts from Gravitational-Wave <span class="hlt">Observations</span> of Binary Neutron Star Mergers</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Messenger, C.; Takami, Kentaro; Gossan, Sarah; Rezzolla, Luciano; Sathyaprakash, B. S.</p> <p>2014-10-01</p> <p>Inspiraling compact binaries as standard sirens will become an invaluable tool for cosmology when we enter the gravitational-wave detection era. However, a degeneracy in the information carried by gravitational waves between the total rest-frame mass M and the redshift z of the <span class="hlt">source</span> implies that neither can be directly extracted from the signal; only the combination M(1+z), the redshifted mass, can be directly extracted from the signal. Recent work has shown that for third-generation detectors, a tidal correction to the gravitational-wave phase in the late-inspiral signal of binary neutron star systems can be used to break the mass-redshift degeneracy. Here, we propose to use the signature encoded in the postmerger signal allowing the accurate extraction of the intrinsic rest-frame mass of the <span class="hlt">source</span>, in turn permitting the determination of <span class="hlt">source</span> redshift and luminosity distance. The entirety of this analysis method and any subsequent cosmological inference derived from it would be obtained solely from gravitational-wave <span class="hlt">observations</span> and, hence, would be independent of the cosmological distance ladder. Using numerical simulations of binary neutron star mergers of different mass, we model gravitational-wave signals at different redshifts and use a Bayesian parameter estimation to determine the accuracy with which the redshift and mass can be extracted. We find that for a known illustrative neutron star equation of state and using the Einstein telescope, the median of the 1σ confidence regions in redshift corresponds to ˜10%-20% uncertainties at redshifts of z <0.04.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/21454920','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/21454920"><span>BLAST <span class="hlt">OBSERVATIONS</span> OF THE SOUTH ECLIPTIC POLE FIELD: NUMBER COUNTS AND <span class="hlt">SOURCE</span> CATALOGS</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Valiante, Elisabetta; Braglia, Filiberto G.; Chapin, Edward L.; Halpern, Mark; Marsden, Gaelen; Scott, Douglas; Ade, Peter A. R.; Griffin, Matthew; Hargrave, Peter C.; Mauskopf, Philip; Pascale, Enzo; Bock, James J.; Devlin, Mark J.; Klein, Jeff; Gundersen, Joshua O.; Hughes, David H.; Netterfield, Calvin B.; Olmi, Luca; Patanchon, Guillaume; Rex, Marie</p> <p>2010-12-15</p> <p>We present results from a survey carried out by the Balloon-borne Large Aperture Submillimeter Telescope (BLAST) on a 9 deg{sup 2} field near the South Ecliptic Pole at 250, 350, and 500 {mu}m. The median 1{sigma} depths of the maps are 36.0, 26.4, and 18.4 mJy, respectively. We apply a statistical method to estimate submillimeter galaxy number counts and find that they are in agreement with other measurements made with the same instrument and with the more recent results from Herschel/SPIRE. Thanks to the large field <span class="hlt">observed</span>, the new measurements give additional constraints on the bright end of the counts. We identify 132, 89, and 61 <span class="hlt">sources</span> with S/N {>=}4 at 250, 350, 500 {mu}m, respectively and provide a multi-wavelength combined catalog of 232 <span class="hlt">sources</span> with a significance {>=}4{sigma} in at least one BLAST band. The new BLAST maps and catalogs are available publicly at http://blastexperiment.info.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1996A%26AT....9..127D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1996A%26AT....9..127D"><span>The fields of reference stars for optical positional <span class="hlt">observations</span> of astrometric extragalactic radio <span class="hlt">sources</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Dement'eva, A. A.; Ryl'Kov, V. P.</p> <p></p> <p>The Pulkovo programme (Pul ERS) and the techniques used to create a catalogue of coordinates and magnitudes for more than 7000 faint stars in 73 small fields around extragalactic radiosources (ERS) are described. Accurate positions of stars in the fields around ERS 2200+420 and ERS 2021+614 are given. The catalogue containing 223 stars is presented. The errors of coordinate reductions in the system of reference stars from the CMC catalogue are found to be 1.5-2.0 times smaller than for those in the system of the PPM catalogue. This programme (Pul ERS) is required for quick identification of the extragalactic radio <span class="hlt">sources</span> and for obtaining their characteristics from <span class="hlt">observations</span> with large telescopes and CCD detectors.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20120004023','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20120004023"><span>Implications of the <span class="hlt">Observed</span> Ultraluminous X-Ray <span class="hlt">Source</span> Luminosity Function</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Swartz, Douglas A.; Tennant, Allyn; Soria, Roberto; Yukita, Mihoko</p> <p>2012-01-01</p> <p>We present the X-ray luminosity function (XLF) of ultraluminous X-ray (ULX) <span class="hlt">sources</span> with 0.3-10.0 keV luminosities in excess of 10(sup 39) erg/s in a complete sample of nearby galaxies. The XLF shows a break or cut-off at high luminosities that deviates from its pure power law distribution at lower luminosities. The cut-off is at roughly the Eddington luminosity for a 90-140 solar mass accretor. We examine the effects on the <span class="hlt">observed</span> XLF of sample biases, of small-number statistics (at the high luminosity end) and of measurement uncertainties. We consider the physical implications of the shape and normalization of the XLF. The XLF is also compared and contrasted to results of other recent surveys.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014cosp...40E1097G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014cosp...40E1097G"><span><span class="hlt">Observations</span> of substorms during storms connected with different <span class="hlt">sources</span> in the solar wind</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Guineva, Veneta; Despirak, Irina; Kozelov, Boris; Borovkov, Leonid</p> <p></p> <p>All-sky cameras data at Kola Peninsula from the 2012/2013 winter seasons have been used to study the variations of substorm development under different conditions of the interplanetary medium. Solar wind and interplanetary magnetic field parameters were taken from OMNI data base. Using solar wind data for the examined periods, different solar wind streams were revealed: recurrent high-speed streams (RS) and magnetic clouds (MC). It is known that these solar wind structures are the <span class="hlt">sources</span> of geomagnetic storms. In our study substorm developments during storms with different origins and during quiet geomagnetic conditions were compared. Substorm onset time and further development were verified by data of IMAGE magnetometers network and by data of all-sky cameras at Apatity and Lovozero. The particularities in the behaviour of substorms <span class="hlt">observed</span> by storms connected with solar wind recurrent streams and by magnetic clouds are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22398947','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22398947"><span>Experimental <span class="hlt">observation</span> of sub-Rayleigh quantum imaging with a two-photon entangled <span class="hlt">source</span></span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Xu, De-Qin; Song, Xin-Bing; Li, Hong-Guo; Zhang, De-Jian; Wang, Hai-Bo; Xiong, Jun Wang, Kaige</p> <p>2015-04-27</p> <p>It has been theoretically predicted that N-photon quantum imaging can realize either an N-fold resolution improvement (Heisenberg-like scaling) or a √(N)-fold resolution improvement (standard quantum limit) beyond the Rayleigh diffraction bound, over classical imaging. Here, we report the experimental study on spatial sub-Rayleigh quantum imaging using a two-photon entangled <span class="hlt">source</span>. Two experimental schemes are proposed and performed. In a Fraunhofer diffraction scheme with a lens, two-photon Airy disk pattern is <span class="hlt">observed</span> with subwavelength diffraction property. In a lens imaging apparatus, however, two-photon sub-Rayleigh imaging for an object is realized with super-resolution property. The experimental results agree with the theoretical prediction in the two-photon quantum imaging regime.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ApPhL.106q1104X','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ApPhL.106q1104X"><span>Experimental <span class="hlt">observation</span> of sub-Rayleigh quantum imaging with a two-photon entangled <span class="hlt">source</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Xu, De-Qin; Song, Xin-Bing; Li, Hong-Guo; Zhang, De-Jian; Wang, Hai-Bo; Xiong, Jun; Wang, Kaige</p> <p>2015-04-01</p> <p>It has been theoretically predicted that N-photon quantum imaging can realize either an N-fold resolution improvement (Heisenberg-like scaling) or a √{ N } -fold resolution improvement (standard quantum limit) beyond the Rayleigh diffraction bound, over classical imaging. Here, we report the experimental study on spatial sub-Rayleigh quantum imaging using a two-photon entangled <span class="hlt">source</span>. Two experimental schemes are proposed and performed. In a Fraunhofer diffraction scheme with a lens, two-photon Airy disk pattern is <span class="hlt">observed</span> with subwavelength diffraction property. In a lens imaging apparatus, however, two-photon sub-Rayleigh imaging for an object is realized with super-resolution property. The experimental results agree with the theoretical prediction in the two-photon quantum imaging regime.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016PhRvS..19i3401M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016PhRvS..19i3401M"><span>Compton <span class="hlt">sources</span> for the <span class="hlt">observation</span> of elastic photon-photon scattering events</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Micieli, D.; Drebot, I.; Bacci, A.; Milotti, E.; Petrillo, V.; Conti, M. Rossetti; Rossi, A. R.; Tassi, E.; Serafini, L.</p> <p>2016-09-01</p> <p>We present the design of a photon-photon collider based on conventional Compton gamma <span class="hlt">sources</span> for the <span class="hlt">observation</span> of elastic γ γ scattering. Two symmetric electron beams, generated by photocathodes and accelerated in linacs, produce two primary gamma rays through Compton backscattering with two high energy lasers. The elastic photon-photon scattering is analyzed by start-to-end simulations from the photocathodes to the detector. A new Monte Carlo code has been developed ad hoc for the counting of the QED events. Realistic numbers of the secondary gamma yield, obtained by using the parameters of existing or approved Compton devices, a discussion of the feasibility of the experiment and of the nature of the background are presented.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005WRR....41.2015N','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005WRR....41.2015N"><span>Backward probability model using multiple <span class="hlt">observations</span> of contamination to identify groundwater contamination <span class="hlt">sources</span> at the Massachusetts Military Reservation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Neupauer, R. M.; Wilson, J. L.</p> <p>2005-02-01</p> <p>Backward location and travel time probability density functions characterize the possible former locations (or the <span class="hlt">source</span> location) of contamination that is <span class="hlt">observed</span> in an aquifer. For an <span class="hlt">observed</span> contaminant particle the backward location probability density function (PDF) describes its position at a fixed time prior to sampling, and the backward travel time probability density function describes the amount of time required for the particle to travel to the sampling location from a fixed upgradient position. The backward probability model has been developed for a single <span class="hlt">observation</span> of contamination (e.g., Neupauer and Wilson, 1999). In practical situations, contamination is sampled at multiple locations and times, and these additional data provide information that can be used to better characterize the former position of contamination. Through Bayes' theorem we combine the individual PDFs for each <span class="hlt">observation</span> to obtain a PDF for multiple <span class="hlt">observations</span> that describes the possible <span class="hlt">source</span> locations or release times of all <span class="hlt">observed</span> contaminant particles, assuming they originated from the same instantaneous point <span class="hlt">source</span>. We show that the multiple-<span class="hlt">observation</span> probability density function is the normalized product of the single-<span class="hlt">observation</span> PDFs. The additional information available from multiple <span class="hlt">observations</span> reduces the variances of the <span class="hlt">source</span> location and travel time probability density functions and improves the characterization of the contamination <span class="hlt">source</span>. We apply the backward probability model to a trichloroethylene (TCE) plume at the Massachusetts Military Reservation (MMR). We use four TCE samples distributed throughout the plume to obtain single-<span class="hlt">observation</span> and multiple-<span class="hlt">observation</span> location and travel time PDFs in three dimensions. These PDFs provide information about the possible <span class="hlt">sources</span> of contamination. Under assumptions that the existing MMR model is properly calibrated and the conceptual model is correct the results confirm the two suspected <span class="hlt">sources</span> of</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2014PhDT.........4O','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2014PhDT.........4O"><span>Solar Atmospheric Energy Redistribution Across Multiple Classes of <span class="hlt">Observable</span> <span class="hlt">Sources</span> of Solar Radiation</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Orange, Norton Brice</p> <p></p> <p>This thesis investigates solar atmospheric energy redistribution across multiple classes of <span class="hlt">observable</span> <span class="hlt">sources</span>, while carrying out extensive work for increasing the proficiency of solar <span class="hlt">observational</span> data's scientific return via a semi-autonomous data-acquisition algorithm. Minimal long-term pointing variations between limb and correlation derived pointings of the Atmospheric Imaging Assembly (AIA) and Helioseismic Magnetic Imager instruments provide evidence that the image-center positions achieve single-pixel accuracy on time scales shorter than their characterization. However, daily AIA passband pointing variations indicate autonomous sub-arcsecond co-registration is not yet fully achievable. Three year variations of ultra-violet (UV), far UV, and extreme-UV flux in coronal hole (CH), quiet Sun (QS), active region (AR), and flares (FLs), as well as irradiances, are consistent with expected trends of chromospheric, transition region (TR), and coronal plasmas. Radiative and magnetic energy couplings reveal a self-similarity between CH, QS, and ARs; indicative of a single dominant heating mechanism. FLs provide evidence of a runaway self-organized criticality of flaring activity -- a heating component married to the magnetic field distribution. Large scale statistical properties of BP phenomena, and a detailed comparison of a transition region BP, coronal BP, and blinker, indicated that measuring similar characteristics across multiple event types holds class-predictive power, and is a significant step towards automated multi-class classification of unresolved transient EUV <span class="hlt">sources</span>. This work directly ties the catastrophic cooling of a cool loop to its non-equilibrium structure (via reconnection at a single footpoint site), and indicates the TR as its heating site due to subsequent plasma evaporation. The first evidence of "S-shape" loop arcades at TR temperatures in QS conditions is provided, as well as that their demise, i.e., relaxed non-potential magnetic</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015GeoRL..42.5243K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015GeoRL..42.5243K"><span>Acoustic <span class="hlt">source</span> inversion to estimate volume flux from volcanic explosions</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kim, Keehoon; Fee, David; Yokoo, Akihiko; Lees, Jonathan M.</p> <p>2015-07-01</p> <p>We present an acoustic waveform inversion technique for <span class="hlt">infrasound</span> data to estimate volume fluxes from volcanic eruptions. Previous inversion techniques have been limited by the use of a 1-D Green's function in a free space or half space, which depends only on the <span class="hlt">source</span>-receiver distance and neglects volcanic topography. Our method exploits full 3-D Green's functions computed by a numerical method that takes into account realistic topographic scattering. We apply this method to vulcanian eruptions at Sakurajima Volcano, Japan. Our inversion results produce excellent waveform fits to field <span class="hlt">observations</span> and demonstrate that full 3-D Green's functions are necessary for accurate volume flux inversion. Conventional inversions without consideration of topographic propagation effects may lead to large errors in the <span class="hlt">source</span> parameter estimate. The presented inversion technique will substantially improve the accuracy of eruption <span class="hlt">source</span> parameter estimation (cf. mass eruption rate) during volcanic eruptions and provide critical constraints for volcanic eruption dynamics and ash dispersal forecasting for aviation safety. Application of this approach to chemical and nuclear explosions will also provide valuable <span class="hlt">source</span> information (e.g., the amount of energy released) previously unavailable.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015ACPD...1517093W','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015ACPD...1517093W"><span><span class="hlt">Source</span> analysis of peroxyacetyl nitrate (PAN) in Guangzhou, China: a yearlong <span class="hlt">observation</span> study</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Wang, B. G.; Zhu, D.; Zou, Y.; Wang, H.; Zhou, L.; Ouyang, X.; Shao, H. F.; Deng, X. J.</p> <p>2015-06-01</p> <p>In recent years, photochemical smog has been a major cause of air pollution in the metropolitan area of Guangzhou, China, with a continuing increase in the concentrations of photochemical pollutants. The concentration of peroxyacetyl nitrate (PAN) has often been found to reach very high levels, posing a potential threat to the public health. To better understand the changes in PAN concentration and its <span class="hlt">sources</span>, a study was carried from January to December of 2012 at the Guangzhou Panyu Atmospheric Composition Station (GPACS) to measure the atmospheric concentrations of PAN as well as those of ozone (O3), nitrogen oxides (NOx), and non-methane hydrocarbon (NMHC). These data were analyzed to investigate the quantitative relationships between PAN and its precursors. In the study period, the hourly concentrations of PAN varied from below instrument detection limit to 12.0 ppbv. The yearly mean concentration of PAN was 0.84 ppbv, with the daily mean concentration exceeding 5 ppbv in 32 of the total <span class="hlt">observation</span> days. Calculations indicate that among the measured NMHC species, alkenes accounted for 53 % of the total NMHC contribution to the PAN production, with aromatics and alkanes accounting for about 11 and 7 % of the total, respectively. During the period of our <span class="hlt">observation</span> only a modest correlation was found between the concentrations of PAN and O3 for daytime hours, and <span class="hlt">observed</span> PAN concentrations were relatively high even though the <span class="hlt">observed</span> NMHCs/NOx ratio was low. This suggests regional air mass transport of pollutants had a major impact on the PAN concentrations in Guangzhou area.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2009A%26A...500.1211M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2009A%26A...500.1211M"><span>Deep optical <span class="hlt">observations</span> of the central X-ray <span class="hlt">source</span> in the Puppis A supernova remnant</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mignani, R. P.; de Luca, A.; Mereghetti, S.; Caraveo, P. A.</p> <p>2009-06-01</p> <p>Context: X-ray <span class="hlt">observations</span> revealed a group of radio-silent isolated neutron stars (INSs) at the centre of young supernova remnants (SNRs), dubbed central compact objects or CCOs, with properties different from those of classical rotation-powered pulsars. In at least three cases, evidence points towards CCOs being low-magnetized INSs, born with slow rotation periods, and possibly accreting from a debris disc of material formed out of the supernova event. Understanding the origin of the diversity of the CCOs can shed light on supernova explosion and neutron star formation models. Optical/infrared (IR) <span class="hlt">observations</span> are crucial to test different CCO interpretations. Aims: The aim of our work is to perform a deep optical investigation of the CCO RX J0822.0-4300 in the Puppis A SNR, one of the most poorly understood in the CCO family. Methods: By using as a reference the Chandra X-ray coordinates of RX J0822.0-4300 we performed deep optical <span class="hlt">observations</span> in the B, V and I bands with the Very Large Telescope (VLT). Results: We found no candidate optical counterpart within 3 σ of the computed Chandra X-ray position down to 5 σ limits of B ~ 27.2, V ~ 26.9, and I ~ 25.6, the deepest obtained in the optical band for this <span class="hlt">source</span>. Conclusions: These limits confirm the non-detection of a companion brighter than an M 5 dwarf. At the same time, they do not constrain optical emission from the neutron star surface, while emission from the magnetosphere would require a spectral break in the optical/IR. Based on <span class="hlt">observations</span> collected at ESO, Paranal, under Programme 78.D-0706(A).</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_19");'>19</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li class="active"><span>21</span></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_21 --> <div id="page_22" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="421"> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22136605','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22136605"><span>KECK <span class="hlt">OBSERVATIONS</span> OF THE GALACTIC CENTER <span class="hlt">SOURCE</span> G2: GAS CLOUD OR STAR?</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Phifer, K.; Meyer, L.; Ghez, A. M.; Witzel, G.; Yelda, S.; Boehle, A.; Morris, M. R.; Becklin, E. E.; Do, T.; Lu, J. R.; Matthews, K.</p> <p>2013-08-10</p> <p>We present new <span class="hlt">observations</span> and analysis of G2-the intriguing red emission-line object which is quickly approaching the Galaxy's central black hole. The <span class="hlt">observations</span> were obtained with the laser guide star adaptive optics systems on the W. M. Keck I and II telescopes (2006-2012) and include spectroscopy (R {approx} 3600) centered on the hydrogen Br{gamma} line as well as K' (2.1 {mu}m) and L' (3.8 {mu}m) imaging. Analysis of these <span class="hlt">observations</span> shows the Br{gamma} line emission has a positional offset from the L' continuum. This offset is likely due to background <span class="hlt">source</span> confusion at L'. We therefore present the first orbital solution derived from Br{gamma} line astrometry, which, when coupled with radial velocity measurements, results in a later time of closest approach (2014.21 {+-} 0.14), closer periastron (130 AU, 1600 R{sub s}), and higher eccentricity (0.9814 {+-} 0.0060) compared to a solution using L' astrometry. It is shown that G2 has no K' counterpart down to K' {approx} 20 mag. G2's L' continuum and the Br{gamma} line emission appears unresolved in almost all epochs, which implies that the bulk of the emission resides in a compact region. The <span class="hlt">observations</span> altogether suggest that while G2 has a gaseous component that is tidally interacting with the central black hole, there is likely a central star providing the self-gravity necessary to sustain the compact nature of this object.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22036968','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22036968"><span>XMM-NEWTON <span class="hlt">OBSERVATIONS</span> OF FIVE INTEGRAL <span class="hlt">SOURCES</span> LOCATED TOWARD THE SCUTUM ARM</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Bodaghee, A.; Tomsick, J. A.; Rodriguez, J.</p> <p>2012-07-01</p> <p>Results are presented for XMM-Newton <span class="hlt">observations</span> of five hard X-ray <span class="hlt">sources</span> discovered by INTEGRAL in the direction of the Scutum Arm. Each <span class="hlt">source</span> received {approx}>20 ks of effective exposure time. We provide refined X-ray positions for all five targets enabling us to pinpoint the most likely counterpart in optical/infrared archives. Spectral and timing information (much of which is provided for the first time) allow us to give a firm classification for IGR J18462-0223 and to offer tentative classifications for the others. For IGR J18462-0223, we discovered a coherent pulsation period of 997 {+-} 1 s, which we attribute to the spin of a neutron star in a highly obscured (N{sub H} =2 Multiplication-Sign 10{sup 23} cm{sup -2}) high-mass X-ray binary (HMXB). This makes IGR J18462-0223 the seventh supergiant fast X-ray transient candidate with a confirmed pulsation period. IGR J18457+0244 is a highly absorbed (N{sub H} =8 Multiplication-Sign 10{sup 23} cm{sup -2}) <span class="hlt">source</span> in which the possible detection of an iron line suggests an active galactic nucleus (AGN) of type Sey-2 situated at z = 0.07(1). A periodic signal at 4.4 ks could be a quasi-periodic oscillation which would make IGR J18457+0244 one of a handful of AGNs in which such features have been claimed, but a slowly rotating neutron star in an HMXB cannot be ruled out. IGR J18482+0049 represents a new obscured HMXB candidate with N{sub H} =4 Multiplication-Sign 10{sup 23} cm{sup -2}. We tentatively propose that IGR J18532+0416 is either an AGN or a pulsar in an HMXB system. The X-ray spectral properties of IGR J18538-0102 are consistent with the AGN classification that has been proposed for this <span class="hlt">source</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1993A%26AS...97..273P','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1993A%26AS...97..273P"><span><span class="hlt">Observations</span> of X-ray transient <span class="hlt">source</span> GS2023+338 with the TTM coded mask telescope</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Pan, H. C.; in 't Zand, J. J. M.; Skinner, G. K.; Borozdin, K. N.; Gil'Fanov, M. R.; Siuniaev, R. A.</p> <p>1993-01-01</p> <p>TTM <span class="hlt">observations</span> in which the bright X-ray transient <span class="hlt">source</span> GS2023+338 (=V404 Cyg) in the period June-August 1989 are reported. The <span class="hlt">observed</span> spectral structure can be modeled using a model of a power-law <span class="hlt">source</span> with a photon index of about 1.5, surrounded by partially ionized material. The <span class="hlt">observed</span> X-rays consist of a component from the power-law <span class="hlt">source</span> and those reflected (down-scattered) by the partially ionized material. Varying the clumpy structure or changing the ionization state of the circumstellar matter will cause the low-energy absorption to fluctuate.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.ncbi.nlm.nih.gov/pubmed/28234491','PUBMED'); return false;" href="https://www.ncbi.nlm.nih.gov/pubmed/28234491"><span>Black carbon <span class="hlt">sources</span> constrained by <span class="hlt">observations</span> in the Russian high Arctic.</span></a></p> <p><a target="_blank" href="https://www.ncbi.nlm.nih.gov/entrez/query.fcgi?DB=pubmed">PubMed</a></p> <p>Popovicheva, Olga Borsovna; Evangeliou, Nikolaos; Eleftheriadis, Konstantinos; Kalogridis, Athina Cerise; Movchan, Vadim Vadimovich; Sitnikov, Nikolay; Eckhardt, Sabine; Makshtas, Alexander; Stohl, Andreas</p> <p>2017-02-24</p> <p>Understanding the role of short-lived climate forcers like black carbon (BC) at high northern latitudes in climate change is hampered by the scarcity of surface <span class="hlt">observations</span> in the Russian Arctic. In this study, highly time resolved Equivalent BC (EBC) measurements during a ship campaign in the White, Barents and Kara Seas in October 2015 are presented. The measured EBC concentrations are compared with BC concentrations simulated with a Lagrangian particle dispersion model coupled with a recently completed global emission inventory to quantify the origin of the Arctic BC. EBC showed increased values (100-400 ng m-3) in the Kara Strait, Kara Sea, and Kola Peninsula, and an extremely high concentration (1000 ng m-3) in the White Sea. Assessment of BC origin throughout the expedition showed that gas flaring emissions from the Yamal/Khanty-Mansiysk and Nenets/Komi regions contributed the most when the ship was close to the Kara Strait, north of 70˚N. Near Arkhangelsk (White Sea), biomass burning in mid-latitudes, surface transportation, and residential and commercial combustion from Central and Eastern Europe were found to be important BC <span class="hlt">sources</span>. The model reproduced <span class="hlt">observed</span> EBC concentrations efficiently, building credibility in the emission inventory for BC emissions at high northern latitudes.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013yCat..74301961D','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013yCat..74301961D"><span>VizieR Online Data Catalog: 93.2GHz <span class="hlt">observations</span> of 9C <span class="hlt">sources</span> (Davies+, 2013)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Davies, M. L.; Stefan, I. I.; Bolton, R. C.; Carpenter, J. M.; Franzen, T. M. O.; Grainge, K. J. B.; Green, D. A.; Hobson, M. P.; Hurley-Walker, N.; Lasenby, A. N.; Olamaie, M.; Perrott, Y. C.; Pooley, G. G.; Riley, J. M.; Rodriguez-Gonzalvez, C.; Saunders, R. D. E.; Scaife, A. M. M.; Schammel, M. P.; Scott, P. F.; Shimwell, T. W.; Titterington, D. J.; Waldram, E. M.; Whittam, I. H.</p> <p>2013-11-01</p> <p>In this paper, results are presented from 93.2-GHz <span class="hlt">observations</span> of 80 9C <span class="hlt">sources</span> from the samples of Bolton et al. 2004, Cat. J/MNRAS/354/485. The six 10.4-m diameter and nine 6.1-m diameter CARMA (Combined Array for Research in Millimeter-wave Astronomy) antennas were used to make 93.2-GHz <span class="hlt">observations</span> of the <span class="hlt">sources</span> in the 00h field in nine days between 2008 August 18 and 2008 October 4, and of the <span class="hlt">sources</span> in the 15h field in nine days between 2009 June 14 and 2009 June 30. The Arcminute Microkelvin Imager Large Array (AMI LA) was used to carry out <span class="hlt">observations</span> at 15.7GHz of the 00h-field <span class="hlt">sources</span> between 2008 August 21 and 2008 August 24 and the 15h-field <span class="hlt">sources</span> between 2009 June 16 and 2009 June 20. (1 data file).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMIN43C..06H','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMIN43C..06H"><span>Proteus - A Free and Open <span class="hlt">Source</span> Sensor <span class="hlt">Observation</span> Service (SOS) Client</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Henriksson, J.; Satapathy, G.; Bermudez, L. E.</p> <p>2013-12-01</p> <p>The Earth's 'electronic skin' is becoming ever more sophisticated with a growing number of sensors measuring everything from seawater salinity levels to atmospheric pressure. To further the scientific application of this data collection effort, it is important to make the data easily available to anyone who wants to use it. Making Earth Science data readily available will allow the data to be used in new and potentially groundbreaking ways. The US National Science and Technology Council made this clear in its most recent National Strategy for Civil Earth <span class="hlt">Observations</span> report, when it remarked that Earth <span class="hlt">observations</span> 'are often found to be useful for additional purposes not foreseen during the development of the <span class="hlt">observation</span> system'. On the road to this goal the Open Geospatial Consortium (OGC) is defining uniform data formats and service interfaces to facilitate the discovery and access of sensor data. This is being done through the Sensor Web Enablement (SWE) stack of standards, which include the Sensor <span class="hlt">Observation</span> Service (SOS), Sensor Model Language (SensorML), <span class="hlt">Observations</span> & Measurements (O&M) and Catalog Service for the Web (CSW). End-users do not have to use these standards directly, but can use smart tools that leverage and implement them. We have developed such a tool named Proteus. Proteus is an open-<span class="hlt">source</span> sensor data discovery client. The goal of Proteus is to be a general-purpose client that can be used by anyone for discovering and accessing sensor data via OGC-based services. Proteus is a desktop client and supports a straightforward workflow for finding sensor data. The workflow takes the user through the process of selecting appropriate services, bounding boxes, <span class="hlt">observed</span> properties, time periods and other search facets. NASA World Wind is used to display the matching sensor offerings on a map. Data from any sensor offering can be previewed in a time series. The user can download data from a single sensor offering, or download data in bulk from all</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013OAP....26..243G','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013OAP....26..243G"><span><span class="hlt">Observation</span> on the Radio Telescope Uran-4 Of Radio <span class="hlt">Sources</span>, Connected with the Coronal Mass Ejection on the Sun</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Galanin, V. V.; Derevjagin, V. G.; Kravetz, R. O.</p> <p></p> <p>In 2012 and 2013 the <span class="hlt">observations</span> of radio <span class="hlt">sources</span> covering by the solar corona was conducted on the radio telescope URAN-4. In obtained data there was fixed the records of the strong radio <span class="hlt">sources</span>, which had flow level comparable with the 3c461 <span class="hlt">source</span>. As a result of information analysis from miscellaneous observatories about the solar activity conditions there is done the conclusion that they are connected with the coronal mass ejections which was took place that time.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2006MNRAS.371.1877R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2006MNRAS.371.1877R"><span>Chandra monitoring <span class="hlt">observations</span> of the ultraluminous X-ray <span class="hlt">source</span> NGC 5204 X-1</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Roberts, T. P.; Kilgard, R. E.; Warwick, R. S.; Goad, M. R.; Ward, M. J.</p> <p>2006-10-01</p> <p>We report the results of a two-month campaign conducted with the Chandra X-ray observatory to monitor the ultraluminous X-ray <span class="hlt">source</span> (ULX) NGC 5204 X-1. This was composed of a 50-ks <span class="hlt">observation</span>, followed by ten 5-ks follow-ups spaced initially at ~3, then at ~10-d intervals. The ULX flux is seen to vary by factors ~5 on time-scales of a few days, but no strong variability is seen on time-scales shorter than an hour. There is no evidence for a periodic signal in the X-ray data. An examination of the X-ray colour variations over the period of the campaign shows the ULX emission consistently becomes spectrally harder as its flux increases. The X-ray spectrum from the 50-ks <span class="hlt">observation</span> can be fitted by a number of disparate spectral models, all of which describe a smooth continuum with, unusually for a ULX, a broad emission feature evident at 0.96keV. The spectral variations, both within the 50-ks <span class="hlt">observation</span> and over the course of the whole campaign, can then be explained solely by variations in the continuum component. In the context of an optically thick corona model (as found in other recent results for ULXs) the spectral variations can be explained by the heating of the corona as the luminosity of the ULX increases, consistent with the behaviour of at least one Galactic black hole system in the strongly Comptonized very high state. We find no new evidence supporting the presence of an intermediate-mass black hole in this ULX.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015AGUFM.A41I0159K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015AGUFM.A41I0159K"><span>GOSAT-OCO-2 synergetic CO2 <span class="hlt">observations</span> over calibration & validation sites and large emission <span class="hlt">sources</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kuze, A.; Shiomi, K.; Suto, H.; Kataoka, F.; Crisp, D.; Schwandner, F. M.; Bruegge, C. J.; Taylor, T.; Kawakami, S.</p> <p>2015-12-01</p> <p>GOSAT and OCO-2 have different <span class="hlt">observation</span> strategies. TANSO-FTS onboard GOSAT has wide spectral coverage from SWIR to TIR and an agile pointing system at the expense of spatial context, while OCO-2 targets CO2with higher spatial resolution using imaging grating spectrometers. Since the early phase of the two projects, both teams have worked in calibration and validation to demonstrate the effectiveness of satellite greenhouse gases <span class="hlt">observation</span>. In 2008, the pre-launch cross-calibration agreement between GOSAT and OCO radiometers was better than 2% when measuring the traceable GOSAT calibration sphere (Sakuma et. al, 2010). Since GOSAT's launch in 2009, annual joint vicarious calibration campaigns at the Railroad Valley (RRV) playa have estimated radiometric degradation factors with time at an uncertainty of 7%. (Kuze et al., 2014). After OCO-2 launch, two independent measurements can now be compared to distinguish common forward calculation errors such as molecule absorption line parameters, solar lines and light-path modification by aerosol scattering from instrument-specific errors. On 25 Mach 2015, both GOSAT and OCO-2 targeted RRV simultaneously. The measured radiance spectra at the top of the atmosphere agree within 5% for all common bands. On June 29 and July 1 during the 7th RRV campaign, coincidence <span class="hlt">observation</span> of GOSAT, OCO-2, AJAX airplane, radiosonde, and FTS and radiometers on the ground, provided surface albedo, BRDF, temperature, humidity CO2 and CH4 density to demonstrate consistency between forward radiative transfer calculation and satellite measured data. Both GOSAT and OCO-2 have been regularly targeting the TCCON site at Lamont and large emission <span class="hlt">sources</span> such as mega cities and oil fields and glint over the ocean. Retrieved parameters such as surface albedo, pressure, column averaged mole fraction and aerosol related parameters can be compared firstly where aerosol optical thickness is low and topography is flat, and then over aerosol</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19950036974&hterms=omega&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Domega','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19950036974&hterms=omega&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Domega"><span>The faint X-ray <span class="hlt">sources</span> in and out of omega Centauri: X-ray <span class="hlt">observations</span> and optical identifications</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cool, Adrienne M.; Grindlay, Jonathan E.; Bailyn, Charles D.; Callanan, Paul J.; Hertz, Paul</p> <p>1995-01-01</p> <p>We present the results of an <span class="hlt">observation</span> of the globular cluster omega Cen (NGC 5139) with the Einstein high-resolution imager (HRI). Of the five low-luminosity X-ray <span class="hlt">sources</span> toward omega Cen which were first identified with the Einstein imaging proportional counter (IPC) (Hertz and Grindlay 1983a, b), two are detected in the Einstein HRI <span class="hlt">observation</span>: IPC <span class="hlt">sources</span> A and D. These detections provide <span class="hlt">source</span> positions accurate to 3 sec-4 sec; the positions are confirmed in a ROSAT HRI <span class="hlt">observation</span> reported here. Using CCD photometry and spectroscopy, we have identified both <span class="hlt">sources</span> as foreground dwarf M stars with emission lines (dMe). The chance projection of two Mde stars within approximately 13 min of the center of omega Cen is not extraordinary, given the space density of these stellar coronal X-ray <span class="hlt">sources</span>. We discuss the possible nature of the three as yet unidentified IPC <span class="hlt">sources</span> toward omega Cen, and consider the constraints that the Einstein <span class="hlt">observations</span> place on the total population of X-ray <span class="hlt">sources</span> in this cluster. The integrated luminosity from faint X-ray <span class="hlt">sources</span> in omega Cen appears to be low relative to both the old open cluster M67 and the post-core-collapse globular, NGC 6397.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/20110011797','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/20110011797"><span>Global VLBI <span class="hlt">Observations</span> of Weak Extragalactic Radio <span class="hlt">Sources</span>: Imaging Candidates to Align the VLBI and Gaia Frames</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Bourda, Geraldine; Collioud, Arnaud; Charlot, Patrick; Porcas, Richard; Garrington, Simon</p> <p>2010-01-01</p> <p>The space astrometry mission Gaia will construct a dense optical QSO-based celestial reference frame. For consistency between optical and radio positions, it will be important to align the Gaia and VLBI frames (International Celestial Reference Frame) with the highest accuracy. In this respect, it is found that only 10% of the ICRF <span class="hlt">sources</span> are suitable to establish this link (70 <span class="hlt">sources</span>), either because most of the ICRF <span class="hlt">sources</span> are not bright enough at optical wavelengths or because they show extended radio emission which precludes reaching the highest astrometric accuracy. In order to improve the situation, we initiated a multi-step VLBI <span class="hlt">observational</span> project, dedicated to finding additional suitable radio <span class="hlt">sources</span> for aligning the two frames. The sample consists of about 450 optically-bright radio <span class="hlt">sources</span>, typically 20 times weaker than the ICRF <span class="hlt">sources</span>, which have been selected by cross-correlating optical and radio catalogs. The initial <span class="hlt">observations</span>, aimed at checking whether these <span class="hlt">sources</span> are detectable with VLBI, and conducted with the European VLBI Network (EVN) in 2007, showed an excellent 90% detection rate. This paper reports on global VLBI <span class="hlt">observations</span> carried out in March 2008 to image 105 from the 398 previously detected <span class="hlt">sources</span>. All <span class="hlt">sources</span> were successfully imaged, revealing compact VLBI structure for about half of them, which is very promising for the future.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=311899&keyword=population+AND+growth&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=90529429&CFTOKEN=80136937','EPA-EIMS'); return false;" href="http://cfpub.epa.gov/si/si_public_record_report.cfm?dirEntryId=311899&keyword=population+AND+growth&actType=&TIMSType=+&TIMSSubTypeID=&DEID=&epaNumber=&ntisID=&archiveStatus=Both&ombCat=Any&dateBeginCreated=&dateEndCreated=&dateBeginPublishedPresented=&dateEndPublishedPresented=&dateBeginUpdated=&dateEndUpdated=&dateBeginCompleted=&dateEndCompleted=&personID=&role=Any&journalID=&publisherID=&sortBy=revisionDate&count=50&CFID=90529429&CFTOKEN=80136937"><span>Examining Long-Term Trends in Mobile <span class="hlt">Source</span> Related Pollutants through Analysis of Emissions, <span class="hlt">Observations</span> and Model Simulations</span></a></p> <p><a target="_blank" href="http://oaspub.epa.gov/eims/query.page">EPA Science Inventory</a></p> <p></p> <p></p> <p>Anthropogenic emissions from a variety of sectors including mobile <span class="hlt">sources</span> have decreased substantially over the past decades despite continued growth in population and economic activity. In this study, we analyze 1990-2010 trends in emission inventories, ambient <span class="hlt">observations</span> and...</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ACP....1610133B','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ACP....1610133B"><span>Nine years of global hydrocarbon emissions based on <span class="hlt">source</span> inversion of OMI formaldehyde <span class="hlt">observations</span></span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Bauwens, Maite; Stavrakou, Trissevgeni; Müller, Jean-François; De Smedt, Isabelle; Van Roozendael, Michel; van der Werf, Guido R.; Wiedinmyer, Christine; Kaiser, Johannes W.; Sindelarova, Katerina; Guenther, Alex</p> <p>2016-08-01</p> <p>As formaldehyde (HCHO) is a high-yield product in the oxidation of most volatile organic compounds (VOCs) emitted by fires, vegetation, and anthropogenic activities, satellite <span class="hlt">observations</span> of HCHO are well-suited to inform us on the spatial and temporal variability of the underlying VOC <span class="hlt">sources</span>. The long record of space-based HCHO column <span class="hlt">observations</span> from the Ozone Monitoring Instrument (OMI) is used to infer emission flux estimates from pyrogenic and biogenic volatile organic compounds (VOCs) on the global scale over 2005-2013. This is realized through the method of <span class="hlt">source</span> inverse modeling, which consists in the optimization of emissions in a chemistry-transport model (CTM) in order to minimize the discrepancy between the <span class="hlt">observed</span> and modeled HCHO columns. The top-down fluxes are derived in the global CTM IMAGESv2 by an iterative minimization algorithm based on the full adjoint of IMAGESv2, starting from a priori emission estimates provided by the newly released GFED4s (Global Fire Emission Database, version 4s) inventory for fires, and by the MEGAN-MOHYCAN inventory for isoprene emissions. The top-down fluxes are compared to two independent inventories for fire (GFAS and FINNv1.5) and isoprene emissions (MEGAN-MACC and GUESS-ES). The inversion indicates a moderate decrease (ca. 20 %) in the average annual global fire and isoprene emissions, from 2028 Tg C in the a priori to 1653 Tg C for burned biomass, and from 343 to 272 Tg for isoprene fluxes. Those estimates are acknowledged to depend on the accuracy of formaldehyde data, as well as on the assumed fire emission factors and the oxidation mechanisms leading to HCHO production. Strongly decreased top-down fire fluxes (30-50 %) are inferred in the peak fire season in Africa and during years with strong a priori fluxes associated with forest fires in Amazonia (in 2005, 2007, and 2010), bushfires in Australia (in 2006 and 2011), and peat burning in Indonesia (in 2006 and 2009), whereas generally increased fluxes</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19780007027','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19780007027"><span>Cygnus A at 99 GHz: <span class="hlt">Observations</span> of the three principal components and interpretation of the central <span class="hlt">source</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Hobbs, R. W.; Maran, S. P.; Kafatos, M.; Brown, L. W.</p> <p>1977-01-01</p> <p>The three principal emission components of Cygnus A were <span class="hlt">observed</span> at 99 GHz, the highest frequency at which radio measurements of this <span class="hlt">source</span> have been accomplished. The <span class="hlt">observations</span> show no definite indication of a high-frequency cutoff in the spectrum of the compact central component, which perhaps may be attributed to an optically thin synchrotron <span class="hlt">source</span> that peaks at a frequency of several hundred GHz.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2013AGUFMNH21D..04S','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2013AGUFMNH21D..04S"><span>Seismoacoustic Signatures from Chelyabinsk Meteor <span class="hlt">Observed</span> by the Kazakhstan Nuclear Explosion Monitoring Network (Invited)</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Smirnov, A.; Mikhailova, N.; Garces, M. A.</p> <p>2013-12-01</p> <p><span class="hlt">Infrasound</span> and seismic stations of the Kazakhstan Nuclear Explosion Monitoring network recorded high-fidelity seismoacoustic signatures from the Chelyabinsk meteor. <span class="hlt">Infrasound</span> array I31KZ in Aktyubinsk was the closest IMS <span class="hlt">infrasound</span> station to the <span class="hlt">source</span>. This station is in the Northwest Kazakhstan, approximately 520 km southward from the bolide blast. The propitious station position relative to the entry trajectory, coupled with calm weather during the event, permitted a detailed, broadband record of the bolide explosion. All eight I31KZ <span class="hlt">infrasound</span> array channels show an extremely strong broadband signal at 03:48 UTC and a duration of ~20 minutes. Array processing of the signal with PMCC4 shows that signal contains unprecedented detail on the <span class="hlt">source</span> characteristics. Another Kazakhstani <span class="hlt">infrasound</span> array in Kurchatov, Northeast Kazakhstan, also recorded the explosion signals. This is third closest <span class="hlt">infrasound</span> array to the <span class="hlt">source</span>. The second one is Russian array I43RU, Dubna. Epicentral distances are 1090 km for Dubna and 1300 km for Kurchatov. Traveltimes are 26 minutes for I31KZ Aktyubinsk and 66 minutes for the Kurchatov array. In addition to <span class="hlt">infrasound</span> arrays, Kazakhstani seismic arrays belonging to Institute of Geophysical Research also recorded the signals generated by the bolide. The epicentral seismic <span class="hlt">source</span> location corresponds to the pressure shock wave ground impact, and is under the meteor hypercenter. The seismic signal was recorded by Akbulak, Borovoe, Karatau and Makanchy arrays and other Kazakhstani seismic stations. Akbulak was the station nearest to epicenter, at a range of 630 km southward. The estimated origin time of the seismic event following the bolide explosion is 03:21:59.64 GMT. The difference between ground truth time 3:20:33 GMT provided by NASA and the seismic origin time is in reasonable agreement with the reported hypercenter altitude range of 25-30 km asl. The seismic event had a body wave magnitude of Mb 3.5, with energy class K 8</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ACPD...1210223M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ACPD...1210223M"><span><span class="hlt">Sources</span> of atmospheric mercury in the tropics: continuous <span class="hlt">observations</span> at a coastal site in Suriname</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Müller, D.; Wip, D.; Warneke, T.; Holmes, C. D.; Dastoor, A.; Notholt, J.</p> <p>2012-04-01</p> <p>Mercury measurements at a coastal site in Nieuw Nickerie (5°56' N, 56°59' W), Suriname, provide the only continuous records of atmospheric mercury in the tropics. Here we evaluate <span class="hlt">observations</span> of total gaseous mercury (TGM) during 2007. Nieuw Nickerie typically samples marine air from the Atlantic Ocean, with occasional influence from continental South America. Over the year, average concentrations are 1.40 ng m-3. As the intertropical convergence zone passes over Suriname twice each year, the site samples both northern and southern hemispheric air masses. We use back trajectories to classify each measurement by hemisphere, as well as continental or ocean. For air passing over ocean before sampling, TGM concentrations are 10% higher in air coming from the Northern Hemisphere (1.45 ng m-3) than from the Southern Hemisphere (1.32 ng m-3). Air from the South American continent also carries higher TGM (1.43 ng m-3) than air from the South Atlantic Ocean, with most of these trajectories occurring in August and September. Biomass burning in Brazil peaks in the same months and likely contributes significantly to elevated concentrations seen in Nickerie. We also compare the <span class="hlt">observed</span> seasonal cycle to two atmospheric mercury chemistry and transport models (GRAHM and GEOS-Chem). Both models simulate transition between northern and southern hemispheric air, thus capturing the seasonal cycle; however the models overestimate the TGM concentrations during months when Nickerie samples Northern Hemisphere air. It is difficult to determine whether the models' <span class="hlt">sources</span> or sinks in the Northern Hemisphere tropics are responsible.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2012ACP....12.7391M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2012ACP....12.7391M"><span><span class="hlt">Sources</span> of atmospheric mercury in the tropics: continuous <span class="hlt">observations</span> at a coastal site in Suriname</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Müller, D.; Wip, D.; Warneke, T.; Holmes, C. D.; Dastoor, A.; Notholt, J.</p> <p>2012-08-01</p> <p>Mercury measurements at a coastal site in Nieuw Nickerie (5°56' N, 56°59' W), Suriname, provide the only continuous records of atmospheric mercury in the tropics. Here we evaluate <span class="hlt">observations</span> of total gaseous mercury (TGM) during 2007. Nieuw Nickerie typically samples marine air from the Atlantic Ocean, with occasional influence from continental South America. Over the year, average concentrations are 1.40 ng m-3. As the intertropical convergence zone passes over Suriname twice each year, the site samples both northern and southern hemispheric air masses. We use back trajectories to classify each measurement by hemisphere, as well as continental or ocean. For air passing over ocean before sampling, TGM concentrations are 10% higher in air coming from the Northern Hemisphere (1.45 ng m-3) than from the Southern Hemisphere (1.32 ng m-3). Air from the South American continent also carries higher TGM (1.43 ng m-3) than air from the South Atlantic Ocean, with most of these trajectories occurring in August and September. Biomass burning in Brazil peaks in the same months and likely contributes significantly to elevated concentrations seen in Nickerie. We also compare the <span class="hlt">observed</span> seasonal cycle to two atmospheric mercury chemistry and transport models (GRAHM and GEOS-Chem). Both models simulate transition between northern and southern hemispheric air, thus capturing the seasonal cycle; however the models overestimate the TGM concentrations during months when Nickerie samples Northern Hemisphere air. It is difficult to determine whether the models' <span class="hlt">sources</span> or sinks in the Northern Hemisphere tropics are responsible.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19920039695&hterms=einstein&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Deinstein','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19920039695&hterms=einstein&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3Deinstein"><span>The spectral archive of cosmic X-ray <span class="hlt">sources</span> <span class="hlt">observed</span> by the Einstein Observatory Focal Plane Crystal Spectrometer</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Lum, Kenneth S. K.; Canizares, Claude R.; Clark, George W.; Coyne, Joan M.; Markert, Thomas H.; Saez, Pablo J.; Schattenburg, Mark L.; Winkler, P. F.</p> <p>1992-01-01</p> <p>The Einstein Observatory Focal Plane Crystal Spectrometer (FPCS) used the technique of Bragg spectroscopy to study cosmic X-ray <span class="hlt">sources</span> in the 0.2-3 keV energy range. The high spectral resolving power (E/Delta-E is approximately equal to 100-1000) of this instrument allowed it to resolve closely spaced lines and study the structure of individual features in the spectra of 41 cosmic X-ray <span class="hlt">sources</span>. An archival summary of the results is presented as a concise record the FPCS <span class="hlt">observations</span> and a <span class="hlt">source</span> of information for future analysis by the general astrophysics community. For each <span class="hlt">observation</span>, the instrument configuration, background rate, X-ray flux or upper limit within the energy band <span class="hlt">observed</span>, and spectral histograms are given. Examples of the contributions the FPCS <span class="hlt">observations</span> have made to the understanding of the objects <span class="hlt">observed</span> are discussed.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19770027736&hterms=investigacion&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dinvestigacion','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19770027736&hterms=investigacion&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3Dinvestigacion"><span>Preliminary results on the apparent size of the <span class="hlt">sources</span> of type III bursts <span class="hlt">observed</span> at low frequencies</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Alvarez, H.</p> <p>1976-01-01</p> <p>We present preliminary results on the apparent angular size of the <span class="hlt">sources</span> of four type III bursts <span class="hlt">observed</span> between 3500 and 50 kHz from the IMP-6 spacecraft. The <span class="hlt">observations</span> were made with a dipole rotating in the plane of the ecliptic where the <span class="hlt">sources</span> are assumed to be. The apparent angular sizes obtained are unexpectedly large. We discuss different explanations for the results. It seems that the scattering of radio waves by electron density inhomogeneities is the most likely cause. We report a temporal increase of the apparent angular size of the <span class="hlt">source</span> during the burst lifetime for some bursts. From its characteristics it appears to be a real effect.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MNRAS.461.2879V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MNRAS.461.2879V"><span>Deep 3-GHz <span class="hlt">observations</span> of the Lockman Hole North with the Very Large Array - I. <span class="hlt">Source</span> extraction and uncertainty analysis</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vernstrom, T.; Scott, Douglas; Wall, J. V.; Condon, J. J.; Cotton, W. D.; Perley, R. A.</p> <p>2016-09-01</p> <p>This is the first of two papers describing the <span class="hlt">observations</span> and cataloguing of deep 3-GHz <span class="hlt">observations</span> of the Lockman Hole North using the Karl G. Jansky Very Large Array. The aim of this paper is to investigate, through the use of simulated images, the uncertainties and accuracy of <span class="hlt">source</span>-finding routines, as well as to quantify systematic effects due to resolution, such as <span class="hlt">source</span> confusion and <span class="hlt">source</span> size. While these effects are not new, this work is intended as a particular case study that can be scaled and translated to other surveys. We use the simulations to derive uncertainties in the fitted parameters, as well as bias corrections for the actual catalogue (presented in Paper II). We compare two different <span class="hlt">source</span>-finding routines, OBIT and AEGEAN, and two different effective resolutions, 8 and 2.75 arcsec. We find that the two routines perform comparably well, with OBIT being slightly better at de-blending <span class="hlt">sources</span>, but slightly worse at fitting resolved <span class="hlt">sources</span>. We show that 30-70 per cent of <span class="hlt">sources</span> are missed or fit inaccurately once the <span class="hlt">source</span> size becomes larger than the beam, possibly explaining <span class="hlt">source</span> count errors in high-resolution surveys. We also investigate the effect of blending, finding that any <span class="hlt">sources</span> with separations smaller than the beam size are fit as single <span class="hlt">sources</span>. We show that the use of machine-learning techniques can correctly identify blended <span class="hlt">sources</span> up to 90 per cent of the time, and prior-driven fitting can lead to a 70 per cent improvement in the number of de-blended <span class="hlt">sources</span>.</p> </li> </ol> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_20");'>20</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li class="active"><span>22</span></li> <li><a href="#" onclick='return showDiv("page_23");'>23</a></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div><!-- col-sm-12 --> </div><!-- row --> </div><!-- page_22 --> <div id="page_23" class="hiddenDiv"> <div class="row"> <div class="col-sm-12"> <div class="pull-right"> <ul class="pagination"> <li><a href="#" onclick='return showDiv("page_1");'>«</a></li> <li><a href="#" onclick='return showDiv("page_21");'>21</a></li> <li><a href="#" onclick='return showDiv("page_22");'>22</a></li> <li class="active"><span>23</span></li> <li><a href="#" onclick='return showDiv("page_24");'>24</a></li> <li><a href="#" onclick='return showDiv("page_25");'>25</a></li> <li><a href="#" onclick='return showDiv("page_25");'>»</a></li> </ul> </div> </div> </div> <div class="row"> <div class="col-sm-12"> <ol class="result-class" start="441"> <li> <p><a target="_blank" onclick="trackOutboundLink('http://hdl.handle.net/2060/19790015680','NASA-TRS'); return false;" href="http://hdl.handle.net/2060/19790015680"><span>New hard X-ray <span class="hlt">sources</span> <span class="hlt">observed</span> with HEAO-A2</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Marshall, F. E.; Boldt, E. A.; Holt, S. S.; Mushotzky, R. F.; Pravdo, S. H.; Rothschild, R. E.; Serlemitsos, P. J.</p> <p>1978-01-01</p> <p>A search for new hard X-ray <span class="hlt">sources</span> using data from the first complete view of the sky with the HEAO-A2 experiment discovered 47 new <span class="hlt">sources</span>, detected 7 <span class="hlt">sources</span> recently discovered with other experiments, and significantly reduced the size of the error boxes for 6 previously known <span class="hlt">sources</span>. Intensities and error boxes are given for each of these <span class="hlt">sources</span>; identifications are suggested when an error contains an object similar to known X-ray <span class="hlt">sources</span>. The new identifications consist of seven Type 1 Seyfert galaxies, including two whose Seyfert characteristics were discovered due to their location in an X-ray error box; one intermediate Seyfert galaxy; three Abell clusters; five N-galaxies; two bursting radio <span class="hlt">sources</span>; and an additional three nearby galaxies with bright nuclei and narrow emission lines.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20110007245&hterms=Butterfly&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DButterfly','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20110007245&hterms=Butterfly&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D30%26Ntt%3DButterfly"><span>Solar <span class="hlt">Sources</span> and Geospace Consequences of Interplanetary Magnetic Clouds <span class="hlt">Observed</span> During Solar Cycle 23</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Gopalswamy, N.; Akiyama, S.; Yashiro, S.; Michalek, G.; Lepping, R. P.</p> <p>2007-01-01</p> <p>We present results of a statistical investigation of 99 magnetic clouds (MCs) <span class="hlt">observed</span> during 1995-2005. The MC-associated coronal mass ejections (CMEs) are faster and wider on the average and originate within +/-30deg from the solar disk center. The solar <span class="hlt">sources</span> of MCs also followed the butterfly diagram. The correlation between the magnetic field strength and speed of MCs was found to be valid over a much wider range of speeds. The number of south-north (SN) MCs was dominant and decreased with solar cycle, while the number of north-south (NS) MCs increased confirming the odd-cycle behavior. Two-thirds of MCs were geoeffective; the Dst index was highly correlated with speed and magnetic field in MCs as well as their product. Many (55%) fully northward (FN) MCs were geoeffective solely due to their sheaths. The non-geoeffective MCs were slower (average speed approx. 382 km/s), had a weaker southward magnetic field (average approx. -5.2nT), and occurred mostly during the rise phase of the solar activity cycle.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20040073167&hterms=Taro&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DTaro','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20040073167&hterms=Taro&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D40%26Ntt%3DTaro"><span>ASCA <span class="hlt">Observation</span> of the Superluminal Jet <span class="hlt">Source</span> GRO J1655-40 in the 1997 Outburst</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Yamaoka, Kazutaka; Ueda, Yoshihiro; Hajime, Inoue; Nagase, Fumiski; Ebisawa, Ken; Kotani, Taro; Tanaka, Yasuo; Zhang, Shang Nan</p> <p>2001-01-01</p> <p>We report on the results of an ASCA <span class="hlt">observation</span> of the Galactic jet <span class="hlt">source</span> GRO 51655-40 performed from 1997 February 25 to February 28 covering a full orbital period (2.62 d). The averaged 2-10 keV flux was about 1.1 Crab. An absorption line feature centered at 6.8 keV was detected both in the GIS and SIS spectra. We interpret this as a blend of two resonance-absorption K alpha lines from H-like and He-like iron ions. We can consistently explain both the ASCA spectra and the simultaneous RXTE/PCA spectrum by a combination of K-absorption lines and K-absorption edges of iron ions. The fact that the absorption line is stably present over the whole orbital phase implies that the distribution of the highly ionized plasma is not affected by the companion star, which is consistent with its presence around the black hole. A curve of growth analysis shows that the plasma contains velocity dispersion along the line-of-sight larger than 300 km/s attributed to bulk motions. It is probably a part of a geometrically thick accretion flow in turbulent motions with velocities of 500-1600 km/s at an estimated radius of sim 10(exp 10)/cm.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015jsrs.conf....9R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015jsrs.conf....9R"><span>On the systematics in apparent proper motions of radio <span class="hlt">sources</span> <span class="hlt">observed</span> by VLBI</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Raposo-Pulido, V.; Lambert, S.; Capitaine, N.; Nilsson, T.; Heinkelmann, R.; Schuh, H.</p> <p>2015-08-01</p> <p>For about twenty years, several authors have been investigating the systematics in the apparent proper motions of radio <span class="hlt">source</span> positions. In some cases, the theoretical work developed (Pyne et al., 1996) could not be assessed due to the few number of VLBI <span class="hlt">observations</span>. In other cases, the effects attributed to apparent proper motion could not be related successfully because there were no significant evidences from a statistical point of view (MacMillan, 2005). In this work we provide considerations about the estimation of the coefficients of spherical harmonics, based on a three-step procedure used by Titov et al. (2011) and Titov and Lambert (2013). The early stage of this work has been to compare step by step the computations and estimation processes between the Calc/Solve (http://gemini.gsfc.nasa.gov/solve/) and VieVS software (Böhm et al., 2012). To achieve this, the results were analyzed and compared with the previous study done by Titov and Lambert (2013).</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2004GBioC..18.4004M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2004GBioC..18.4004M"><span>CH4 <span class="hlt">sources</span> estimated from atmospheric <span class="hlt">observations</span> of CH4 and its 13C/12C isotopic ratios: 1. Inverse modeling of <span class="hlt">source</span> processes</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mikaloff Fletcher, Sara E.; Tans, Pieter P.; Bruhwiler, Lori M.; Miller, John B.; Heimann, Martin</p> <p>2004-12-01</p> <p>A time-dependent inverse modeling approach that estimates the global magnitude of atmospheric methane <span class="hlt">sources</span> from the <span class="hlt">observed</span> spatiotemporal distribution of atmospheric CH4, 13C/12C isotopic ratios, and a priori estimates of the <span class="hlt">source</span> strengths is presented. Relative to the a priori <span class="hlt">source</span> estimates, the inverse model calls for increased CH4 flux from <span class="hlt">sources</span> with strong spatial footprints in the tropics and Southern Hemisphere and decreases in <span class="hlt">sources</span> in the Northern Hemisphere. The CH4 and 13C/12C isotopic ratio <span class="hlt">observations</span> suggest an unusually high CH4 flux from swamps (˜200 ± 44 Tg CH4/yr) and biomass burning (88 ± 18 Tg CH4/yr) with relatively low estimates of emissions from bogs (˜20 ± 14 Tg CH4/yr), and landfills (35 ± 14 Tg CH4/yr). The model results support the hypothesis that the 1998 CH4 growth rate anomaly was caused in part by a large increase in CH4 production from wetlands, and indicate that wetland <span class="hlt">sources</span> were about 40 Tg CH4/yr higher in 1998 than 1999.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015EGUGA..17.8516V','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015EGUGA..17.8516V"><span>Validation of simulated flow direction and hydraulic gradients with hydraulic head <span class="hlt">observations</span> using open <span class="hlt">source</span> GIS</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Vandersteen, Katrijn; Rogiers, Bart; Gedeon, Matej</p> <p>2015-04-01</p> <p>It is recommended to check hydraulic gradients and flow directions predicted by a groundwater flow model that is calibrated solely with hydraulic head <span class="hlt">observations</span>. It has been demonstrated in literature that substantial errors can be made when the model is not calibrated on these state variables. Therefore, in this work, we perform a validation of a steady-state groundwater flow model, representing part of the Neogene aquifer (60 km2) in Belgium. This model was developed and calibrated solely on groundwater head measurements, in the framework of the environmental impact assessment of the near surface repository for low- and intermediate-level short-lived waste, realized by ONDRAF/NIRAS at Dessel, Belgium. Horizontal flow directions, horizontal and vertical gradients for the entire area of the groundwater model were estimated from measurements at shallow monitoring wells within the groundwater flow model domain, and compared to the flow directions and vertical gradients predicted by the model. For obtaining horizontal flow directions and gradients, triangulation of groundwater levels was performed for combinations of three neighboring hydraulic head <span class="hlt">observations</span> in the same hydrogeological layer within the model. The simulated equivalents at the same monitoring wells were used to repeat the same methodology, and calculate flow direction components. This analysis was performed in SAGA GIS and was visualized through QGIS. Comparison of the flow directions and flow gradients obtained from measurements and simulations gives an indication on the model performance. The calculations were performed for three sandy hydrogeological units used in the model. A similar procedure was performed for the vertical hydraulic head gradients, where any combination of two hydraulic head <span class="hlt">observations</span> at the same location but at different levels within the aquifer were used to validate the vertical gradients predicted by the model. Besides model validation on average hydraulic heads, the</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010JGRD..115.0K22L','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010JGRD..115.0K22L"><span>Anthropogenic air pollution <span class="hlt">observed</span> near dust <span class="hlt">source</span> regions in northwestern China during springtime 2008</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Li, Can; Tsay, Si-Chee; Fu, Joshua S.; Dickerson, Russell R.; Ji, Qiang; Bell, Shaun W.; Gao, Yang; Zhang, Wu; Huang, Jianping; Li, Zhanqing; Chen, Hongbin</p> <p>2010-04-01</p> <p>Trace gases and aerosols were measured in Zhangye (39.082°N, 100.276°E, 1460 m a.s.l.), a rural site near the Gobi deserts in northwestern China during spring 2008. Primary trace gases (CO: 265 ppb; SO2: 3.4 ppb; NOy*: 4.2 ppb; hereafter results given as means of hourly data) in the area were lower than in eastern China, but still indicative of marked anthropogenic emissions. Sizable aerosol mass concentration (153 μg/m3) and light scattering (159 Mm-1 at 500 nm) were largely attributable to dust emissions, and aerosol light absorption (10.3 Mm-1 at 500 nm) was dominated by anthropogenic pollution. Distinct diurnal variations in meteorology and pollution were induced by the local valley terrain. Strong daytime northwest valley wind cleaned out pollution and was replaced by southeast mountain wind that allowed pollutants to build up overnight. In the afternoon, aerosols had single scattering albedo (SSA, 500 nm) of 0.95 and were mainly of supermicron particles, presumably dust, while at night smaller particles and SSA of 0.89-0.91 were related to pollution. The diverse local emission <span class="hlt">sources</span> were characterized: the CO/SO2, CO/NOy, NOy/SO2 (by moles), and BC/CO (by mass) ratios for small point <span class="hlt">sources</span> such as factories were 24.6-54.2, 25.8-35.9, 0.79-1.31, and 4.1-6.1 × 10-3, respectively, compared to the corresponding inventory ratios of 43.7-71.9, 23.7-25.7, 1.84-2.79, and 3.4-4.0 × 10-3 for the industrial sector in the area. The mixing between dust and pollution can be ubiquitous in this region. During a dust storm shown as an example, pollutants were <span class="hlt">observed</span> to mix with dust, causing discernible changes in both SSA and aerosol size distribution. Further interaction between dust and pollutants during transport may modify the properties of dust particles that are critical for their large-scale impact on radiation, clouds, and global biogeochemical cycles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=20110007810&hterms=Air+pollution&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DAir%2Bpollution','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=20110007810&hterms=Air+pollution&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D20%26Ntt%3DAir%2Bpollution"><span>Anthropogenic Air Pollution <span class="hlt">Observed</span> Near Dust <span class="hlt">Source</span> Regions in Northwestern China During Springtime 2008</span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Li, Can; Tsay, Si-Chee; Fu, Joshua S.; Dickerson, Russell R.; Ji, Qiang; Bell, Shaun W.; Gao, Yang; Zhang, Wu; Huang, Jianping; Li, Zhanqing; Chen, Hongbin</p> <p>2010-01-01</p> <p>Trace gases and aerosols were measured in Zhangye (39.082degN, 100.276degE, 1460 m a.s. 1.), a rural site near the Gobi deserts in northwestern China during spring 2008. Primary trace gases (CO:265 ppb; SO2:3.4 ppb; NO(*y): 4.2 ppb; hereafter results given as means of hourly data) in the area were lower than in eastern China, but still indicative of marked anthropogenic emissions. Sizable aerosol mass concentration (153 micro-g/cu m) and light scattering (159/Mm at 500 nm) were largely attributable to dust emissions, and aerosol light absorption (10.3/Mm at 500 nm) was dominated by anthropogenic pollution. Distinct diurnal variations in meteorology and pollution were induced by the local valley terrain. Strong daytime northwest valley wind cleaned out pollution and was replaced by southeast mountain wind that allowed pollutants to build up overnight. In the afternoon, aerosols had single scattering albedo (SSA, 500 mn) of 0.95 and were mainly of supermicron particles, presumably dust, while at night smaller particles and SSA of 0.89-0.91 were related to Pollution. The diverse local emission <span class="hlt">sources</span> were characterized: the CO/SO2, CO/NO(y), NO(y)/SO2 (by moles), and BC/CO (by mass) ratios for small point <span class="hlt">sources</span> such as factories were 24.6-54.2, 25.8-35.9, 0.79-1.31, and 4.1-6.1 x 10(exp -3), respectively, compared to the corresponding inventory ratios of 43.7-71.9, 23.7-25.7, 1.84-2.79, and 3.4-4.0 x 10(exp -3) for the industrial sector in the area. The mixing between dust and pollution can be ubiquitous in this region. During a dust storm shown as an example, pollutants were <span class="hlt">observed</span> to mix with dust, causing discernible changes in both SSA and aerosol size distribution. Further interaction between dust and pollutants during transport may modify the properties of dust particles that are critical for their large-scale impact on radiation, clouds, and global biogeochemical cycles.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/AD0687438','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/AD0687438"><span>ADDITIONAL <span class="hlt">OBSERVATIONS</span> OF PLANETS AND QUASI-STELLAR RADIO <span class="hlt">SOURCES</span> AT 3 MM,</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p></p> <p>MERCURY ( PLANET ), VENUS( PLANET ), PERIODIC VARIATIONS, RADIO ASTRONOMY, SPECTRUM SIGNATURES...EXTRATERRESTRIAL RADIO WAVES, <span class="hlt">SOURCES</span>), GALAXIES, BLACKBODY RADIATION, BRIGHTNESS, TEMPERATURE, MARS( PLANET ), JUPITER( PLANET ), SATURN( PLANET</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2005A%26A...440...93K','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2005A%26A...440...93K"><span>FIRST-based survey of Compact Steep Spectrum <span class="hlt">sources</span>. II. MERLIN and VLA <span class="hlt">observations</span> of medium-sized symmetric objects</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Kunert-Bajraszewska, M.; Marecki, A.; Thomasson, P.; Spencer, R. E.</p> <p>2005-09-01</p> <p>A new sample of candidate Compact Steep Spectrum (CSS) <span class="hlt">sources</span> that are much weaker than the CSS <span class="hlt">source</span> prototypes has been selected from the VLA FIRST catalogue. MERLIN "snapshot" <span class="hlt">observations</span> of the <span class="hlt">sources</span> at 5 GHz indicate that six of them have an FR II-like morphology, but are not edge-brightened as is normal for Medium-sized Symmetric Objects (MSOs) and FR IIs. Further <span class="hlt">observations</span> of these six <span class="hlt">sources</span> with the VLA at 4.9 GHz and MERLIN at 1.7 GHz, as well as subsequent full-track <span class="hlt">observations</span> with MERLIN at 5 GHz of what appeared to be the two <span class="hlt">sources</span> of greatest interest are presented. The results are discussed with reference to the established evolutionary model of CSS <span class="hlt">sources</span> being young but in which not all of them evolve to become old objects with extended radio structures. A lack of stable fuelling in some of them may result in an early transition to a so-called coasting phase so that they fade away instead of growing to become large-scale objects. It is possible that one of the six <span class="hlt">sources</span> (1542+323) could be labelled as a prematurely "dying" MSO or a "fader".</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016ApJ...827..141M','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016ApJ...827..141M"><span><span class="hlt">Source</span> Regions of the Type II Radio Burst <span class="hlt">Observed</span> During a CME-CME Interaction on 2013 May 22</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Mäkelä, P.; Gopalswamy, N.; Reiner, M. J.; Akiyama, S.; Krupar, V.</p> <p>2016-08-01</p> <p>We report on our study of radio <span class="hlt">source</span> regions during the type II radio burst on 2013 May 22 based on direction-finding analysis of the Wind/WAVES and STEREO/WAVES (SWAVES) radio <span class="hlt">observations</span> at decameter-hectometric wavelengths. The type II emission showed an enhancement that coincided with the interaction of two coronal mass ejections (CMEs) launched in sequence along closely spaced trajectories. The triangulation of the SWAVES <span class="hlt">source</span> directions posited the ecliptic projections of the radio <span class="hlt">sources</span> near the line connecting the Sun and the STEREO-A spacecraft. The WAVES and SWAVES <span class="hlt">source</span> directions revealed shifts in the latitude of the radio <span class="hlt">source</span>, indicating that the spatial location of the dominant <span class="hlt">source</span> of the type II emission varies during the CME-CME interaction. The WAVES <span class="hlt">source</span> directions close to 1 MHz frequencies matched the location of the leading edge of the primary CME seen in the images of the LASCO/C3 coronagraph. This correspondence of spatial locations at both wavelengths confirms that the CME-CME interaction region is the <span class="hlt">source</span> of the type II enhancement. Comparison of radio and white-light <span class="hlt">observations</span> also showed that at lower frequencies scattering significantly affects radio wave propagation.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://www.osti.gov/scitech/biblio/22364704','SCIGOV-STC'); return false;" href="https://www.osti.gov/scitech/biblio/22364704"><span>IS COMPTON COOLING SUFFICIENT TO EXPLAIN EVOLUTION OF <span class="hlt">OBSERVED</span> QUASI-PERIODIC OSCILLATIONS IN OUTBURST <span class="hlt">SOURCES</span>?</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>Mondal, Santanu; Chakrabarti, Sandip K.; Debnath, Dipak E-mail: chakraba@bose.res.in</p> <p>2015-01-01</p> <p>In outburst <span class="hlt">sources</span>, quasi-periodic oscillation (QPO) frequency is known to evolve in a certain way: in the rising phase, it monotonically goes up until a soft intermediate state is achieved. In the propagating oscillatory shock model, oscillation of the Compton cloud is thought to cause QPOs. Thus, in order to increase QPO frequency, the Compton cloud must collapse steadily in the rising phase. In decline phases, the exact opposite should be true. We investigate cause of this evolution of the Compton cloud. The same viscosity parameter that increases the Keplerian disk rate also moves the inner edge of the Keplerian component, thereby reducing the size of the Compton cloud and reducing the cooling timescale. We show that cooling of the Compton cloud by inverse Comptonization is enough for it to collapse sufficiently so as to explain the QPO evolution. In the two-component advective flow configuration of Chakrabarti-Titarchuk, centrifugal force-induced shock represents the boundary of the Compton cloud. We take the rising phase of 2010 outburst of Galactic black hole candidate H 1743-322 and find an estimation of variation of the α parameter of the sub-Keplerian flow to be monotonically rising from 0.0001 to 0.02, well within the range suggested by magnetorotational instability. We also estimate the inward velocity of the Compton cloud to be a few meters per second, which is comparable to what is found in several earlier studies of our group by empirically fitting the shock locations with the time of <span class="hlt">observations</span>.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2015SPIE.9306E..0II','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2015SPIE.9306E..0II"><span><span class="hlt">Observation</span> of the pulp horn by swept <span class="hlt">source</span> optical coherence tomography and cone beam computed tomography</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Iino, Yoshiko; Yoshioka, Toshihiko; Hanada, Takahiro; Ebihara, Arata; Sunakawa, Mitsuhiro; Sumi, Yasunori; Suda, Hideaki</p> <p>2015-02-01</p> <p>Cone-beam computed tomography (CBCT) is one of the most useful diagnostic techniques in dentistry but it involves ionizing radiation, while swept <span class="hlt">source</span> optical coherence tomography (SS-OCT) has been introduced recently as a nondestructive, real-time, high resolution imaging technique using low-coherence interferometry, which involves no ionizing radiation. The purpose of this study was to evaluate the ability of SS-OCT to detect the pulp horn (PH) in comparison with that of CBCT. Ten extracted human mandibular molars were used. After horizontally removing a half of the tooth crown, the distance from the cut dentin surface to PH was measured using microfocus computed tomography (Micro CT) (SL) as the gold standard, by CBCT (CL) and by SS-OCT (OL). In the SS-OCT images, only when PH was <span class="hlt">observed</span> beneath the overlying dentin, the distance from the cut dentin surface to PH was recorded. If the pulp was exposed, it was defined as pulp exposure (PE). The results obtained by the above three methods were statistically analyzed by Spearman's rank correlation coefficient at a significance level of p < 0.01. SS-OCT detected the presence of PH when the distance from the cut dentin surface to PH determined by SL was 2.33 mm or less. Strong correlations of the measured values were found between SL and CL (r=0.87), SL and OL (r=0.96), and CL and OL (r=0.86). The results showed that SS-OCT images correlated closely with CBCT images, suggesting that SS-OCT can be a useful tool for the detection of PH.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('https://ntrs.nasa.gov/search.jsp?R=19990069932&hterms=State+observers&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DState%2Bobservers','NASA-TRS'); return false;" href="https://ntrs.nasa.gov/search.jsp?R=19990069932&hterms=State+observers&qs=Ntx%3Dmode%2Bmatchall%26Ntk%3DAll%26N%3D0%26No%3D60%26Ntt%3DState%2Bobservers"><span>Angular Broadening: Effects of Nonzero, Spatially Varying Plasma Frequency Between the <span class="hlt">Source</span> and <span class="hlt">Observer</span></span></a></p> <p><a target="_blank" href="http://ntrs.nasa.gov/search.jsp">NASA Technical Reports Server (NTRS)</a></p> <p>Cairns, Iver H.</p> <p>1998-01-01</p> <p>Angular broadening of radiation due to scattering by density irregularities is usually described using geometric optics (GO) or the parabolic wave equation (PWE) with the assumptions that the radiation frequency f greatly exceeds the local plasma frequency f(sub p0) or that f(sub p0)/f is constant along the path. These assumptions are inappropriate for many solar system radio phenomena. Here the PWE and GO formalisms are extended to treat angular broadening in plasmas with nonzero, spatially varying ratios, f(sub p0)(z)/f < 1. The new PWE results show that the correlation function, scattered angular spectrum, and other quantities are modified by inclusion of a denominator factor [1 - f(sup 2, sub p0)(z prime)/f prime] inside the path integral over z prime, while the mean-square scattering angle <theta(sup 2)> depends on both f(sub p0)(z)/f at the <span class="hlt">observer</span> and the foregoing factor inside the path integral. The PWE and GO predictions for <theta(sup 2)> are identical and involve equivalent assumptions. Previous GO and PWE results are recovered in the limits that f(sub p0)(z prime)/f is constant or zero. The new PWE and GO results will permit more accurate calculation of angular broadening for solar system and astrophysical <span class="hlt">sources</span>. Moreover and importantly, due to the PWE and GO results for <theta(sub 2)> being identical, previous GO analyses of <theta(sub 2)> in solar system contexts are essentially correct, except for the neglect of or minor deficiencies in the treatment of nonzero, spatially varying f(sub p0)/f effects. The identical GO and PWE results for <theta(sub 2)> and the form of the PWE equation for the correlation function raise questions as to whether diffraction is unimportant for angular broadening (under the usual PWE conditions). Future direct comparisons of the PWE predictions with angular spectra calculated using existing GO ray-tracing codes should answer these questions. Diffraction effects are probably important when the medium and turbulence are</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2016MNRAS.462..917R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2016MNRAS.462..917R"><span>Deep <span class="hlt">observations</span> of the Super-CLASS supercluster at 325 MHz with the GMRT: the low-frequency <span class="hlt">source</span> catalogue</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Riseley, C. J.; Scaife, A. M. M.; Hales, C. A.; Harrison, I.; Birkinshaw, M.; Battye, R. A.; Beswick, R. J.; Brown, M. L.; Casey, C. M.; Chapman, S. C.; Demetroullas, C.; Hung, C.-L.; Jackson, N. J.; Muxlow, T.; Watson, B.</p> <p>2016-10-01</p> <p>We present the results of 325 MHz Giant Metrewave Radio Telescope <span class="hlt">observations</span> of a supercluster field, known to contain five Abell clusters at redshift z ˜ 0.2. We achieve a nominal sensitivity of 34 μJy beam-1 towards the phase centre. We compile a catalogue of 3257 <span class="hlt">sources</span> with flux densities in the range 183 μ {Jy}-1.5 {Jy} within the entire ˜6.5 deg2 field of view. Subsequently, we use available survey data at other frequencies to derive the spectral index distribution for a sub-sample of these <span class="hlt">sources</span>, recovering two distinct populations - a dominant population which exhibit spectral index trends typical of steep-spectrum synchrotron emission, and a smaller population of <span class="hlt">sources</span> with typically flat or rising spectra. We identify a number of <span class="hlt">sources</span> with ultrasteep spectra or rising spectra for further analysis, finding two candidate high-redshift radio galaxies and three gigahertz-peaked-spectrum radio <span class="hlt">sources</span>. Finally, we derive the Euclidean-normalized differential <span class="hlt">source</span> counts using the catalogue compiled in this work, for <span class="hlt">sources</span> with flux densities in excess of 223 μJy. Our differential <span class="hlt">source</span> counts are consistent with both previous <span class="hlt">observations</span> at this frequency and models of the low-frequency <span class="hlt">source</span> population. These represent the deepest <span class="hlt">source</span> counts yet derived at 325 MHz. Our <span class="hlt">source</span> counts exhibit the well-known flattening at mJy flux densities, consistent with an emerging population of star-forming galaxies; we also find marginal evidence of a downturn at flux densities below 308 μJy, a feature so far only seen at 1.4 GHz.</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/2010AGUFM.P13A1364I','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/2010AGUFM.P13A1364I"><span>Ground <span class="hlt">Observation</span> of the Hayabusa Reentry: The Third Opportunity of Man-made Fireball from Interplanetary Orbit</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Ishihara, Y.; Yamamoto, M.; Hiramatsu, Y.; Furumoto, M.; Fujita, K.</p> <p>2010-12-01</p> <p>After 7 years and 6,000,000,000 km of challenging cruise in the solar system, the Hayabusa did come back to the Earth on June 13, 2010. The Hayabusa, the first sample-return explorer to NEA, landed on 25243 Itokawa in 2005, capturing surface particles on the S-type asteroid into its sample return capsule (SRC). Following to the reentries of the Genesis in 2004 and the Stardust in 2006, the return of the Hayabusa SRC was the third direct reentry event from the interplanetary transfer orbit to the Earth at a velocity of over 11.2 km/s. In addition, it was world first case of direct reentry of spacecraft from interplanetary transfer orbit. After the successful resumption of the SRC, it was carefully sent to ISAS/JAXA, and at present, small particles expected to be the first sample-return materials from the minor planet are carefully investigated. In order to obtain precise trajectory information to ensure the quick procedure for the Hayabusa SRC resumption team, we <span class="hlt">observed</span> the Hayabusa SRC reentry by optically in Australian night sky. High-resolution imaging and spectroscopy were carried out with several high-sensitivity instruments to investigate thermal-protection process of thermal protection ablator (TPA) as well as interaction process between SRC surface materials and upper atmospheric neutral and plasma components. Moreover, shockwaves were <span class="hlt">observed</span> by <span class="hlt">infrasound</span>/seismic sensor arrays on ground to investigate reentry related shockwaves as well as air-to-ground coupling process at the extremely rare opportunity. With respect to nominal trajectory of the Hayabusa SRC reentry, four optical stations were set inside and near the Woomera Prohibited Area, Australia, targeting on peak-heat and/or front-heat profiles of ablating TPA for engineering aspect. <span class="hlt">Infrasound</span> and seismic sensors were also deployed as three arrayed stations and three single stations to realize direction findings of sonic boom type shockwaves from the SRC and spacecraft and point <span class="hlt">source</span> type</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.dtic.mil/docs/citations/ADA596871','DTIC-ST'); return false;" href="http://www.dtic.mil/docs/citations/ADA596871"><span><span class="hlt">Observing</span> Short-wave Infrared Atmospheric Fluorescence Near Radioactive <span class="hlt">Sources</span>: A Feasibility Study</span></a></p> <p><a target="_blank" href="https://publicaccess.dtic.mil/psm/api/service/search/search">DTIC Science & Technology</a></p> <p></p> <p>2014-03-17</p> <p>UV detection is “solar blind.” Furthermore, Nagano et al [5] used atmospheric fluorescence from electrons produced though strontium - 90 β-decay to...as determine the minimum activity required for stand-off detection of a theoretical strontium -90 β-<span class="hlt">source</span> during a 2 s integration. Recently, there...functions as a <span class="hlt">source</span> of its secondary decay product, γ-rays. To estimate the strength of a strontium -90 β-<span class="hlt">source</span> that would be required for detection by</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://adsabs.harvard.edu/abs/1997SPIE.3116..156R','NASAADS'); return false;" href="http://adsabs.harvard.edu/abs/1997SPIE.3116..156R"><span>Infrasonic <span class="hlt">observations</span> of bolides on October 4, 1996</span></a></p> <p><a target="_blank" href="http://adsabs.harvard.edu/abstract_service.html">NASA Astrophysics Data System (ADS)</a></p> <p>Revelle, Douglas O.; Whitaker, Rodney W.; Armstrong, William T.</p> <p>1997-10-01</p> <p>During the evening of October 3, 1996, at least six bright fireballs were <span class="hlt">observed</span> over the western United States with reports from California to Louisiana. The event over California produced tremendous sonic boom reports in the Los Angeles area. This event was also detected locally by 31 seismometers which are part of a network of seismic stations operated by the California Institute of Technology. Subsequent investigations of the data from the four <span class="hlt">infrasound</span> arrays used by LANL (Los Alamo National Laboratory) and operated for the DOE (Department of Energy) as part of the CTBT Program (Comprehensive Test Ban Treaty) Research and Development program showed the presence of an infrasonic signal from the proper direction at the correct time for this bolide from two of our four arrays (Nevada Test Site; NTS and Pinedale, WY; PDL). Both the seismic and <span class="hlt">infrasound</span> recordings indicated that an explosion occurred in the atmosphere, having its epicenter near Little Lake, Calif. for possible <span class="hlt">sources</span> heights from 40 - 60 km. The infrasonic arrays are each composed of four elements, i.e., low frequency pressure sensors that are in near-continuous operation. The nominal spacing between elements is 150 - 200 m depending on the specific site. The basic sensor is a Globe Universal Sciences Model 100C microphone whose amplitude response is flat from 0.1 to 300 Hz. Each sensor is connected to 12 porous hoses which act to reduce wind noise. The signal characteristics, analyzed from 0.1 to 5.0 Hz, includes a total duration of 5 (NTS) to 20 minutes (PDL) for a <span class="hlt">source</span> directed toward 230 - 240 degrees from true North. The signal trace velocities ranged from 300 - 360 m/sec with a signal velocity of 0.30 plus or minus 0.03 km/sec, implying a stratospheric (S type) ducted path (with a reflection altitude of from 40 - 60 km). The dominant signal frequency is from 0.20 to 0.80 Hz, with a peak near 0.2 to 0.25 Hz. These highly correlated signals had a maximum amplitude of 1.0 microbars (0</p> </li> <li> <p><a target="_blank" onclick="trackOutboundLink('http://www.osti.gov/scitech/servlets/purl/674700','SCIGOV-STC'); return false;" href="http://www.osti.gov/scitech/servlets/purl/674700"><span>Infrasonic <span class="hlt">observations</span> of bolides on October 4, 1996</span></a></p> <p><a target="_blank" href="http://www.osti.gov/scitech">SciTech Connect</a></p> <p>ReVelle, D.O.; Whitaker, R.W.; Armstrong, W.T.</p> <p>1997-12-31</p> <p>During the evening of October 3, 1996, at least 6 bright fireballs were <span class="hlt">observed</span> over the western US with reports from California to Louisiana. The event over California produced tremendous sonic boom reports in the Los Angeles area. This event was also detected locally by 31 seismometers which are part of a network of seismic stations operated by the California Institute of Technology. Subsequent investigations of the data from the four <span class="hlt">infrasound</span> arrays used by LANL (Los Alamos National Laboratory) and operated for the DOE (Department of Energy) as a part of the CTBT Program (Comprehensive Test Ban Treaty) Research and Development program showed the presence of an infrasonic signal from the proper direction at the correct time for this bolide from two of the four arrays (Nevada Test Site; NTS and Pinedale, WY; PDL). Both the seismic and <span class="hlt">infrasound</span> recordings indicated that an explosion occurred in the atmosphere, having its epicenter near Little Lake, CA for possible <span class="hlt">sources</span> heights from 40--60 km. The infrasonic arrays are each composed of fur elements, i.e., low frequency pressure sensors that are in near-continuous operation. The nominal spacing between elements is 150--200 m depending on the specific site. The basic sensor is a Globe Universal Sciences Model 100C microphone whose amplitude response is flat from 0.1 to 300 Hz. Each sensor is connected to 12 porous hoses which act to reduce wind noise. The signal characteristics, analyzed from 0.1 to 5.0 Hz, includes a total duration of 5 (NTS) to 20 minutes (PDL) for a <span class="hlt">source</span> directed toward 230--240 degrees from true North. The sign