Science.gov

Sample records for period event observations

  1. Observations of deep long-period (DLP) seismic events beneath Aleutian arc volcanoes; 1989-2002

    USGS Publications Warehouse

    Power, J.A.; Stihler, S.D.; White, R.A.; Moran, S.C.

    2004-01-01

    Between October 12, 1989 and December 31, 2002, the Alaska Volcano Observatory (AVO) located 162 deep long-period (DLP) events beneath 11 volcanic centers in the Aleutian arc. These events generally occur at mid- to lower-crustal depths (10-45 km) and are characterized by emergent phases, extended codas, and a strong spectral peak between 1.0 and 3.0 Hz. Observed wave velocities and particle motions indicate that the dominant phases are P- and S-waves. DLP epicenters often extend over broad areas (5-20 km) surrounding the active volcanoes. The average reduced displacement of Aleutian DLPs is 26.5 cm2 and the largest event has a reduced displacement of 589 cm2 (or ML2.5). Aleutian DLP events occur both as solitary events and as sequences of events with several occurring over a period of 1-30 min. Within the sequences, individual DLPs are often separated by lower-amplitude volcanic tremor with a similar spectral character. Occasionally, volcano-tectonic earthquakes that locate at similar depths are contained within the DLP sequences.At most, Aleutian volcanoes DLPs appear to loosely surround the main volcanic vent and occur as part of background seismicity. A likely explanation is that they reflect a relatively steady-state process of magma ascent over broad areas in the lower and middle portions of the crust. At Mount Spurr, DLP seismicity was initiated by the 1992 eruptions and then slowly declined until 1997. At Shishaldin Volcano, a short-lived increase in DLP seismicity occurred about 10 months prior to the April 19, 1999 eruption. These observations suggest a link between eruptive activity and magma flux in the mid- to lower-crust and uppermost mantle.

  2. Cells anticipate periodic events

    NASA Astrophysics Data System (ADS)

    Nakagaki, Toshiyuki

    2009-03-01

    We show that an amoeboid organism can anticipate the timing of periodic events. The plasmodium of the true slime mold Physarum polycephalum moves rapidly under favourable conditions, but stops moving when transferred to less-favourable conditions. Plasmodia exposed to unfavourable conditions, presented in three consecutive pulses at constant intervals, reduced their locomotive speed in response to each episode. When subsequently subjected to favourable conditions, the plasmodia spontaneously reduced their locomotive speed at the time point when the next unfavourable episode would have occurred. This implied anticipation of impending environmental change. After this behaviour had been evoked several times, the locomotion of the plasmodia returned to normal; however, the anticipatory response could subsequently be induced by a single unfavourable pulse, implying recall of the memorized periodicity. We explored the mechanisms underlying these behaviours from a dynamical systems perspective. Our results hint at the cellular origins of primitive intelligence and imply that simple dynamics might be sufficient to explain its emergence.

  3. Climatology of Mid-Latitude Mstid Events Observed by the Demeter Satellite in the Period 2005-2010.

    NASA Astrophysics Data System (ADS)

    Berthelier, J. J.; Nguyen, C. T.; Amory-Mazaudier, C. C.; Petitdidier, M.

    2015-12-01

    Using plasma measurements from the CNES DEMETER micro-satellite, we have performed a global survey of ionospheric disturbances observed at middle and low latitudes on the nightime part of the DEMETER orbit in the local time sector 21.30-22.30 LT. This study encompasses the 6 years of the satellite operations, from 2005 to 2010, including years of moderate magnetic activity of solar cycles 23 and 24 and the deep solar minimum in 2009-2010. We report in this poster a statistical analysis of MSTID events characterized by quasi-periodic variations of the O+ density observed below ~ 40° geomagnetic latitudes with wavelengths ranging from 350 to 700 km. Although detected in both hemispheres they occur predominantly at southern latitudes with a rather strong peak over the Pacific ocean. A detailed analysis has shown that these events may be sorted in 4 categories according to their latitudinal extent. Most of them are restricted to a latitude band between ~ 15° and 40° geomagnetic in North or South but some of them extend from mid latitudes in one hemisphere to low latitude in the other hemisphere, thus spanning equatorial regions up to 5-10°. The apparent negative correlation with magnetic activity seems to indicate that most of these events are driven by AGW originating from low altitude atmospheric levels and not triggered by auroral phenomena. We shall present the seasonal and inter-annual variations showing significant changes associated with solar activity. Our results will be compared to other ground-based or satellite observations and our investigation pointed out a strong effect of these MSTID and their parent AGW on the electrodynamics of the low latitude ionosphere.

  4. Periodicity in marine extinction events

    NASA Technical Reports Server (NTRS)

    Sepkoski, J. John, Jr.; Raup, David M.

    1986-01-01

    The periodicity of extinction events is examined in detail. In particular, the temporal distribution of specific, identifiable extinction events is analyzed. The nature and limitations of the data base on the global fossil record is discussed in order to establish limits of resolution in statistical analyses. Peaks in extinction intensity which appear to differ significantly from background levels are considered, and new analyses of the temporal distribution of these peaks are presented. Finally, some possible causes of periodicity and of interdependence among extinction events over the last quarter billion years of earth history are examined.

  5. Inner magnetosphere variations after solar proton events. Observations on Mir space station in 1989-1994 time period.

    PubMed

    Dachev TsP; Semkova, J V; Matviichuk YuN; Tomov, B T; Koleva, R T; Baynov, P T; Petrov, V M; Shurshakov, V V; Ivanov, Y u

    1998-01-01

    Measurements on board the Mir space station have been used to study the dose rate and the particle flux distribution in the inner magnetosphere. The measurements have been performed with the Bulgarian-Russian dosimeter-radiometer Liulin. The paper concentrates on the dynamics of the observed "new" and "second" maxima which were created after Solar Proton Events (SPE) in the 1989-1994 time. The "second" belt was first observed after the SPE on October 20, 1989, and the last observation was after the SPE on February 20, 1994. The creation of the "new" belt is a unique phenomena seen in the Liulin data set after the SPE on March 23, 1991 and relates to the magnetic storm on March 24. The new belt fully disappears in the middle of 1993.

  6. Operation of a digital seismic network on Mount St. Helens volcano and observations of long period seismic events that originate under the volcano

    SciTech Connect

    Fehler, M.; Chouet, B.

    1982-09-01

    A 9 station digital seismic array was operated on Mount St. Helens volcano in Washington State during 1981. One of the stations was placed inside the crater of the volcano, six were located on the flanks of the volcano within two km of the crater and two were approximately ten km from the crater. Four of the instruments recorded three components of motion and the remaining five recorded only the vertical component. A one day experiment was carried out during which the crater monitoring seismometer was complimented by the addition of two ink recording instruments. During the one day experiment six observers recorded times of rockfall, felt-earthquake occurrences, and changes in steam emissions from the dome in the crater. Using information obtained during the one day experiment seismic events recorded by the digital instruments were classified as earthquakes, rockfalls, helicopter noise and a type of event that is unique to volcanoes which is called long period. Waveforms of these long period events have a duration of up to 30 seconds and a spectrum that is peaked at approximately 2 Hz. The frequency at which the peak in the spectrum occurs is nearly the same at all stations which means that the unique waveform of long period events is due to a source effect, not a path effect. The peak frequency is fairly insensitive to the amplitude of the signal which means that the size of the source region is constant, independent of the signal amplitude. Long period events were not felt and were accompanied by no visible changes inside the crater which lead to the conclusion that they are some sort of seismic disturbance generated inside the Volcano.

  7. Auroral activities observed by SNPP VIIRS day/night band during a long period geomagnetic storm event on April 29-30, 2014

    NASA Astrophysics Data System (ADS)

    Shao, Xi; Cao, Changyong; Liu, Tung-chang; Zhang, Bin; Wang, Wenhui; Fung, Shing F.

    2015-10-01

    The Day/Night Band (DNB) of the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard Suomi-NPP represents a major advancement in night time imaging capabilities. The DNB senses radiance that can span 7 orders of magnitude in one panchromatic (0.5-0.9 μm) reflective solar band and provides imagery of clouds and other Earth features over illumination levels ranging from full sunlight to quarter moon. When the satellite passes through the day-night terminator, the DNB sensor is affected by stray light due to solar illumination on the instrument. With the implementation of stray light correction, stray light-corrected DNB images enable the observation of aurora occurred in the high latitude regions during geomagnetic storms. In this paper, DNB observations of auroral activities are analyzed during a long period (> 20 hours) of geomagnetic storm event occurred on Apr. 29-30, 2014. The storm event has the Bz component of interplanetary magnetic field (IMF) pointing southward for more than 20 hours. During this event, the geomagnetic storm index Dst reached -67 nT and the geomagnetic auroral electrojet (AE) index increased and reached as high as 1200 nT with large amplitude fluctuations. The event occurred during new moon period and DNB observation has minimum moon light contamination. During this event, auroras are observed by DNB for each orbital pass on the night side (~local time 1:30am) in the southern hemisphere. DNB radiance data are processed to identify regions of aurora during each orbital pass. The evolution of aurora is characterized with time series of the poleward and equatorward boundary of aurora, area, peak radiance and total light emission of the aurora in DNB observation. These characteristic parameters are correlated with solar wind and geomagnetic index parameters. It is found that the evolution of total area-integrated radiance of auroral region over the southern hemisphere correlated well with the ground geomagnetic AE index with correlation

  8. PERIODIC SIGNALS IN BINARY MICROLENSING EVENTS

    SciTech Connect

    Guo, Xinyi; Stefano, Rosanne Di; Esin, Ann; Taylor, Jeffrey

    2015-08-20

    Gravitational microlensing events are powerful tools for the study of stellar populations. In particular, they can be used to discover and study a variety of binary systems. A large number of binary lenses have already been found through microlensing surveys and a few of these systems show strong evidence of orbital motion on the timescale of the lensing event. We expect that more binary lenses of this kind will be detected in the future. For binaries whose orbital period is comparable to the event duration, the orbital motion can cause the lensing signal to deviate drastically from that of a static binary lens. The most striking property of such light curves is the presence of quasi-periodic features, which are produced as the source traverses the same regions in the rotating lens plane. These repeating features contain information about the orbital period of the lens. If this period can be extracted, then much can be learned about the lensing system even without performing time-consuming, detailed light-curve modeling. However, the relative transverse motion between the source and the lens significantly complicates the problem of period extraction. To resolve this difficulty, we present a modification of the standard Lomb–Scargle periodogram analysis. We test our method for four representative binary lens systems and demonstrate its efficiency in correctly extracting binary orbital periods.

  9. Detectability of Discrete Event Systems with Dynamic Event Observation

    PubMed Central

    Shu, Shaolong; Lin, Feng

    2009-01-01

    Our previous work considers detectability of discrete event systems which is to determine the current state and subsequent states of a system based on event observation. We assume that event observation is static, that is, if an event is observable, then all its occurrences are observable. However, in practical systems such as sensor networks, event observation often needs to be dynamic, that is, the occurrences of same events may or may not be observable, depending on the state of the system. In this paper, we generalize static event observation into dynamic event observation and consider the detectability problem under dynamic event observation. We define four types of detectabilities. To check detectabilities, we construct the observer with exponential complexity. To reduce computational complexity, we can also construct a detector with polynomial complexity to check strong detectabilities. Dynamic event observation can be implemented in two possible ways: a passive observation and an active observation. For the active observation, we discuss how to find minimal event observation policies that preserve four types of detectabilities respectively. PMID:20161618

  10. Operation of a digital seismic network on Mount St. Helens volcano and observations of long-period seismic events that originate under the volcano

    SciTech Connect

    Fehler, M.; Chouet, B.

    1982-01-01

    During the period May through October 1981, a nine station digital seismic array was operated on the flanks of Mount St. Helens volcano in the state of Washington. The purpose was to obtain high quality digital seismic data from a dense seismic array operating near and in the summit crater of the volcano to facilitate study of near field seismic waveforms generated under the volcano. Our goal is to investigate the source mechanism of volcanic tremor and seismic activity associated with magma intrusion, dome growth and steam-ash emissions occurring within the crater of Mount St. Helens.

  11. PULSAR OBSERVATIONS OF EXTREME SCATTERING EVENTS

    SciTech Connect

    Coles, W. A.; Kerr, M.; Shannon, R. M.; Hobbs, G. B.; Manchester, R. N.; Dai, S.; Ravi, V.; Reardon, D.; Toomey, L.; Zhu, X. J.; You, X.-P.; Bailes, M.; Straten, W. van; Bhat, N. D. R.; Burke-Spolaor, S.; Keith, M. J.; Levin, Y.; Osłowski, S.; Wang, J. B.; Wen, L.

    2015-08-01

    Extreme scattering events (ESEs) in the interstellar medium (ISM) were first observed in regular flux measurements of compact extragalactic sources. They are characterized by a flux variation over a period of weeks, suggesting the passage of a “diverging plasma lens” across the line of sight (LOS). Modeling the refraction of such a lens indicates that the structure size must be of the order of AU and the electron density of the order of 10s of cm{sup −3}. Similar structures have been observed in measurements of pulsar intensity scintillation and group delay. Here we report observations of two ESEs, showing increases in both intensity scintillation and dispersion made with the Parkes Pulsar Timing Array. These allow us to make more complete models of the ESE, including an estimate of the “outer-scale” of the turbulence in the plasma lens. These observations clearly show that the ESE structure is fully turbulent on an AU scale. They provide some support for the idea that the structures are extended along the LOS, such as would be the case for a scattering shell. The dispersion measurements also show a variety of AU scale structures that would not be called ESEs, yet involve electron density variations typical of ESEs and likely have the same origin.

  12. Solar Energetic Particle Events Observed by MAVEN

    NASA Astrophysics Data System (ADS)

    Lee, C. O.; Larson, D. E.; Lillis, R. J.; Luhmann, J. G.; Halekas, J. S.; Brain, D.; Connerney, J. E. P.; Espley, J. R.; Epavier, F.; Thiemann, E.; Zeitlin, C.; Jakosky, B. M.

    2015-12-01

    We present observations of solar energetic particle (SEP) events made by the Mars Atmosphere and Volatile EvolutioN (MAVEN) SEP instrument, which measures energetic ions and electrons impacting the upper Martian atmosphere. Since the arrival of the MAVEN spacecraft at Mars, a large number of solar flares and a few major coronal mass ejections (CMEs) erupted from the Sun. The SEPs are accelerated by the related shock in the solar corona or by the propagating interplanetary shock ahead of the CME ejecta. Mixed in with these SEPs are particles accelerated by the shocks of corotating streams, some of which have recurred for several solar cycles due to the persistent coronal hole sources. The SEP events are analyzed together with the upstream solar wind observations from the MAVEN Solar Wind Ion Analyzer (SWIA) and magnetometer (MAG). The sources of the SEP events are determined from Earth-based solar imagery and the MAVEN Extreme Ultra-violet Monitor (EUVM) together with numerical simulations of the inner heliospheric conditions. A comparison with the radiation dose rate measurements from the Mars Science Laboratory (MSL) Radiation Assessment Detector (RAD) reveals a lack of ground signatures during the onset of the highest energy SEPs for the events observed by MAVEN, indicating that the SEPs fully deposit their energies into the Martian atmosphere. Using measurements made from the ensemble of instruments onboard MAVEN, we investigate the consequences of SEPs at Mars for a number of events observed during the primary science mapping phase of the MAVEN mission.

  13. Observations of Pluto-Charon mutual events

    SciTech Connect

    Blanco, C.; Di Martino, M.; Ferreri, W.; Osservatorio Astronomico, Turin )

    1989-07-01

    As part of the planned 'Pluto-Charon Mutual Eclipse Season Campaign', one mutual event was observed at the ESO Observatory on July 10, 1986 and seven mutual events were observed at the Serra La Nave stellar station of Catania Astrophysical Observatory from April 29 to July 21, 1987. At ESO the measurements were performed at the 61-cm Bochum telescope equipped with a photon-counting system and U, B, V, filters; at Serra La Nave the Cassegrain focus of the 91-cm reflector was equipped with a photon-counting system and B and V filters. The observed light losses and contact times do not show relevant systematic deviations from the predicted ones. An examination of the behavior of the B and V light curves gives slight indications of a different slope of the B and V light loss of the same event for a superior or an inferior event, and shows that the superior events are shallower at wavelengths longer than B. 6 refs.

  14. Crres Observations of Particle Flux Dropout Events

    NASA Technical Reports Server (NTRS)

    Fennell, J.; Roeder, J.; Spence, H.; Singer, H.; Korth, A.; Grande, M.; Vampola, A.

    1999-01-01

    The complete disappearance of energetic electrons was observed by CRRES in the near geosynchronous region in 7.5% of the orbits examined. These total flux dropouts were defined by the fluxes rapidly dropping to levels below the sensitivity of the MEA energetic electron spectrometer on the CRRES satellite. They were separated into those that were only energetic electron dropouts and those that were associated with energetic ion and plasma dropouts. Approximately 20% of the events showed dropouts of 0 particle fluxes, and these were usually coincident with large increases in the local magnetic intensity and signatures of strong current systems. The energetic particle instruments and magnetometer on CRRES provide a detailed picture of the particle and field responses to these unusual conditions. Both the local morning and dusk events were associated with strong azimuthal (eastward) and radial changes in the magnetic field indicative of a strong current system approaching and sometimes crossing the CRRES position at the time of the flux dropouts. The direction of the field changes and the details of particle observations are consistent with CRRES passing through the plasma sheet boundary layer and entering the tail lobe for a significant number of the events.

  15. Black Hole Observations - Towards the Event Horizon

    NASA Astrophysics Data System (ADS)

    Britzen, Silke

    Black Holes are probably the most elusive solutions of Einstein's theory of General Relativity. Despite numerous observations of the direct galactic environment and indirect influence of astrophysical black holes (e.g. jets, variable emission across the wavelength spectrum, feedback processes, etc.) -- a direct proof of their existence is still lacking. This article highlights some aspects deduced from many observations and concentrates on the experimental results with regard to black holes with masses from millions to billions of solar masses. The focus will be on the challenges and remaining questions. The Event Horizon Telescopce (EHT) project to image the photon sphere of Sgr A* and its potential is briefly sketched. This instrumental approach shall lead to highest resolution observations of the supermassive black hole at the center of the Milky Way (Sgr A*).

  16. Validation in the Absence of Observed Events

    DOE PAGES

    Lathrop, John; Ezell, Barry

    2015-07-22

    Here our paper addresses the problem of validating models in the absence of observed events, in the area of Weapons of Mass Destruction terrorism risk assessment. We address that problem with a broadened definition of “Validation,” based on “backing up” to the reason why modelers and decision makers seek validation, and from that basis re-define validation as testing how well the model can advise decision makers in terrorism risk management decisions. We develop that into two conditions: Validation must be based on cues available in the observable world; and it must focus on what can be done to affect thatmore » observable world, i.e. risk management. That in turn leads to two foci: 1.) the risk generating process, 2.) best use of available data. Based on our experience with nine WMD terrorism risk assessment models, we then describe three best use of available data pitfalls: SME confidence bias, lack of SME cross-referencing, and problematic initiation rates. Those two foci and three pitfalls provide a basis from which we define validation in this context in terms of four tests -- Does the model: … capture initiation? … capture the sequence of events by which attack scenarios unfold? … consider unanticipated scenarios? … consider alternative causal chains? Finally, we corroborate our approach against three key validation tests from the DOD literature: Is the model a correct representation of the simuland? To what degree are the model results comparable to the real world? Over what range of inputs are the model results useful?« less

  17. Validation in the Absence of Observed Events

    SciTech Connect

    Lathrop, John; Ezell, Barry

    2015-07-22

    Here our paper addresses the problem of validating models in the absence of observed events, in the area of Weapons of Mass Destruction terrorism risk assessment. We address that problem with a broadened definition of “Validation,” based on “backing up” to the reason why modelers and decision makers seek validation, and from that basis re-define validation as testing how well the model can advise decision makers in terrorism risk management decisions. We develop that into two conditions: Validation must be based on cues available in the observable world; and it must focus on what can be done to affect that observable world, i.e. risk management. That in turn leads to two foci: 1.) the risk generating process, 2.) best use of available data. Based on our experience with nine WMD terrorism risk assessment models, we then describe three best use of available data pitfalls: SME confidence bias, lack of SME cross-referencing, and problematic initiation rates. Those two foci and three pitfalls provide a basis from which we define validation in this context in terms of four tests -- Does the model: … capture initiation? … capture the sequence of events by which attack scenarios unfold? … consider unanticipated scenarios? … consider alternative causal chains? Finally, we corroborate our approach against three key validation tests from the DOD literature: Is the model a correct representation of the simuland? To what degree are the model results comparable to the real world? Over what range of inputs are the model results useful?

  18. The international seismological observing period in Africa

    USGS Publications Warehouse

    Engdahl, E.R.; Bergman, Eric A.

    1992-01-01

    The International Seismological Observing Period (ISOP) is a specific time interval designated for enhanced international cooperation in the collection and dissemination of observatory measurements from the global seismographic network. The primary purpose of the ISOP is to strengthen the international infrastructure that supports current seismological practice and increase the cooperation among nations that operate seismological observatories. Measurements, reported by the existing global network and compiled by agencies such as the International Seismological Centre (ISC), are providing new information about earthquakes and the structure of the Earth of fundamental importance to the Earth sciences. However, these data represent but a small fraction of the information contained in the seismograms. One of the goals of the ISOP is to collect improved sets of data. In particular, the measurement and reporting of later-arriving phases, during a fixed ISOP period, from earthquakes selected for detailed observation by the cooperating stations will be encouraged. The use of advanced, digital instrumentation provides an unprecedented opportunity for enhancing the methods of seismogram interpretation and seismic parameter extraction, by the implementation of digital processing methods at seismic observatories worldwide. It must be ensured that this new information will be available to the entire seismological community. It is believed that this purpose is best served with an ISOP that promotes increased on-site processing at digital stations in Africa and elsewhere. Improvements in seismology require truly international cooperation and the educational aspects of seismological practice form one of the goals of the ISOP. Thus, workshops will be needed in Africa to train analysts in ISOP procedures and to introduce them to modern techniques and applications of the data. Participants will, thus, benefit from theoretical results and practical experience that are of direct

  19. 1 CFR 19.4 - Proclamations calling for the observance of special days or events.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... special days or events. 19.4 Section 19.4 General Provisions ADMINISTRATIVE COMMITTEE OF THE FEDERAL... PROCLAMATIONS § 19.4 Proclamations calling for the observance of special days or events. Except as may be... calling for the observance of special days, or other periods of time, or events, shall be assigned by...

  20. 1 CFR 19.4 - Proclamations calling for the observance of special days or events.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... special days or events. 19.4 Section 19.4 General Provisions ADMINISTRATIVE COMMITTEE OF THE FEDERAL... PROCLAMATIONS § 19.4 Proclamations calling for the observance of special days or events. Except as may be... calling for the observance of special days, or other periods of time, or events, shall be assigned by...

  1. 1 CFR 19.4 - Proclamations calling for the observance of special days or events.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... special days or events. 19.4 Section 19.4 General Provisions ADMINISTRATIVE COMMITTEE OF THE FEDERAL... PROCLAMATIONS § 19.4 Proclamations calling for the observance of special days or events. Except as may be... calling for the observance of special days, or other periods of time, or events, shall be assigned by...

  2. 1 CFR 19.4 - Proclamations calling for the observance of special days or events.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... special days or events. 19.4 Section 19.4 General Provisions ADMINISTRATIVE COMMITTEE OF THE FEDERAL... PROCLAMATIONS § 19.4 Proclamations calling for the observance of special days or events. Except as may be... calling for the observance of special days, or other periods of time, or events, shall be assigned by...

  3. 1 CFR 19.4 - Proclamations calling for the observance of special days or events.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... special days or events. 19.4 Section 19.4 General Provisions ADMINISTRATIVE COMMITTEE OF THE FEDERAL... PROCLAMATIONS § 19.4 Proclamations calling for the observance of special days or events. Except as may be... calling for the observance of special days, or other periods of time, or events, shall be assigned by...

  4. Protoplasmic Computing to Memorize and Recall Periodic Environmental Events

    NASA Astrophysics Data System (ADS)

    Tero, Atsushi; Saigusa, Tetsu; Nakagaki, Toshiyuki

    Single-celled organisms might be more intelligent than previously envisaged [1]-[5]. The acts of anticipating and recalling events are higher functions performed by the brains of higher animals; their evolutionary origins and the way they self-organize, however, remain open questions. Here we show that an amoeboid organism can anticipate the timing of periodic events. The plasmodium of the true slime mold Physarum polycephalum moves rapidly under favorable conditions, but stops moving when transferred to less-favorable conditions. For example, plasmodia exposed to low temperature and low humidity, presented in three consecutive pulses at constant intervals, reduced their locomotive speed in response to each episode. When favorable conditions were subsequently reintroduced, the plasmodia spontaneously reduced their locomotive speed at the point in time when the next unfavorable episode would have occurred. This implies that the plasmodia are able to anticipate impending environmental change. After this anticipatory response had been evoked several times, the locomotion of the plasmodia returned to normal speed; however, the slowing down could subsequently be induced by a single unfavorable pulse, implying recall of the periodicity that had been memorized. We have explored the mechanisms underlying this behavior from a dynamical systems perspective. Our results suggest that this primitive intelligence is of cellular origin and that simple dynamics might be sufficient to explain its emergence. abstract environment.

  5. Multiple Flux transfer events observed by Cluster

    NASA Astrophysics Data System (ADS)

    Trenchi, Lorenzo; Trattner, Karlheinz; Fazakerley, Andrew; Fear, Robert; Mihaljcic, Branislav

    2016-07-01

    Time-varying reconnection at the Earth magnetopause generates magnetic structures called Flux Transfer Events (FTE) characterized by the typical bipolar variation in the magnetic field component normal to the magnetopause. Different generation mechanisms have been proposed: the original Russell and Elphic FTE model (1978) predicts a pair of elbow shaped flux tubes of reconnected field lines generated by intermittent and localized reconnection. Alternatively, Lee and Fu (1985) propose that FTEs are caused by reconnection along multiple extended X-lines while a third FTE model is based on bursty reconnection along a single X-line (Scholer et al. 1988; Southwood et al., 1988). In this presentation, we present the detailed analysis of several FTEs sequentially observed by Cluster on 27 March 2007. While the Grad Shafranov analysis gives FTE orientations completely different from each other that are more in agreement with the Russell and Elphic model, the FTE orientations obtained from multi-spacecraft timing, which are probably more reliable, have smaller deviations with respect to the X line orientation, and are therefore more consistent with the extended X line models. Most of these FTEs are associated with a single reconnection jet, moving in the same direction of the FTEs, which appears consistently at the trailing edge of the FTEs. This signature suggests a generation mechanism based on single X line reconnection. We also used the Grad Shafranov reconstruction to recover the field topology of a large FTE, which is not associated with reconnection jets. The reconstruction suggests that this FTE is a flux rope with nested helical field lines, which is expected in the multiple X line reconnection. A possible interpretation suggests that both single X line and multiple X line generation mechanisms contributed to the formation of the FTEs during this magnetopause crossing.

  6. Aerosol classification using EARLINET measurements for an intensive observational period

    NASA Astrophysics Data System (ADS)

    Papagiannopoulos, Nikolaos; Mona, Lucia; Pappalardo, Gelsomina

    2016-04-01

    ACTRIS (Aerosols, Clouds and Trace gases Research Infrastructure Network) organized an intensive observation period during summer 2012. This campaign aimed at the provision of advanced observations of physical and chemical aerosol properties, at the delivery of information about the 3D distribution of European atmospheric aerosols, and at the monitoring of Saharan dust intrusions events. EARLINET (European Aerosol Research Lidar Network) participated in the ACTRIS campaign through the addition of measurements according to the EARLINET schedule as well as daily lidar-profiling measurements around sunset by 11 selected lidar stations for the period from 8 June - 17 July. EARLINET observations during this almost two-month period are used to characterize the optical properties and vertical distribution of long-range transported aerosol over the broader area of Mediterranean basin. The lidar measurements of aerosol intensive parameters (lidar ratio, depolarization, Angstrom exponents) are shown to vary with location and aerosol type. A methodology based on EARLINET observations of frequently observed aerosol types is used to classify aerosols into seven separate types. The summertime Mediterranean basin is prone to African dust aerosols. Two major dust events were studied. The first episode occurred from the 18 to 21 of the June and the second one lasted from 28 June to 6 July. The lidar ratio within the dust layer was found to be wavelength independent with mean values of 58±14 sr at 355 nm and 57±11 sr at 532 nm. For the particle linear depolarization ratio, mean values of 0.27±0.04 at 532 nm have been found. Acknowledgements. The financial support for EARLINET in the ACTRIS Research Infrastructure Project by the European Union's Horizon 2020 research and innovation programme under grant agreement no. 654169 and previously under grant agreement no. 262254 in the Seventh Framework Programme (FP7/2007-2013) is gratefully acknowledged.

  7. Observations of a possible ground signature of flux transfer events

    NASA Technical Reports Server (NTRS)

    Goertz, C. K.; Nielsen, E.; Korth, A.; Haldoupis, C.; Hoeg, P.; Hayward, D.; Glassmeier, K. H.

    1985-01-01

    Questions regarding the mechanism by which the large-scale cross-tail electric field and associated convection in the magnetosphere is maintained have not yet been completely answered. According to Dungey (1961), the boundary layer (BL) inside the magnetopause (MP) in which the tailward transport of mass, momentum, and magnetic flux takes place can be produced by reconnection. Observations made with the aid of the ISEE spacecraft show that reconnection can occur both in a quasisteady form and in a more unsteady form known under the name 'flux transfer event' (FTE). The present investigation proposes observation of the ground signature of an FTE. It is pointed out that the STARE radar system has the potential for making observations pertinent to identifying and studying the ionospheric signatures of FTE's. An analysis is conducted of two periods during which the convective boundary (CB) moved into the STARE field of view. The significance of the observations is discussed.

  8. Exciting Developments in Tidal Disruption Event Observations

    NASA Astrophysics Data System (ADS)

    Gezari, Suvi

    2017-01-01

    In the past decade, there has been a steady rate of tidal disruption event (TDE) detections from wide-field surveys across the electromagnetic spectrum of a couple per year. I will highlight recent real-time TDE discoveries by optical time domain surveys that have enabled the detailed characterization of TDE light curves, broad-line emission, dust echoes, and outflows. In the next decade, ZTF and LSST will dramatically increase the survey capabilities in the optical time domain, potentially yielding tens to thousands of TDE detections per year. I will conclude with thoughts on how to achieve efficient and prompt classification of TDEs among the future deluge of optical transients, in order that they may be used as effective probes of supermassive black hole demographics and accretion physics.

  9. Semi-Periodic Sequences and Extraneous Events in Earthquake Forecasting: I. Theory and Method, Parkfield Application

    NASA Astrophysics Data System (ADS)

    Nava Pichardo, Fidencio Alejandro; Quinteros Cartaya, Claudia Beatriz; Glowacka, Ewa; Frez Cárdenas, José Duglas

    2014-07-01

    We present a new method to identify semi-periodic sequences in the occurrence times of large earthquakes, which allows for the presence of multiple semi-periodic sequences and/or events not belonging to any identifiable sequence in the time series. The method, based on the analytic Fourier transform, yields estimates of the departure from periodicity of an observed sequence, and of the probability that the sequence is not due to chance. These estimates are used to make and to evaluate forecasts of future events belonging to each sequence. Numerous tests with synthetic catalogs show that the method is surprisingly capable of correctly identifying sequences, unidentifiable by eye, in complicated time series. Correct identification of a given sequence depends on the number of events it contains, on the sequence's departure from periodicity, and, in some cases, on the choice of starting and ending times of the analyzed time window; as well as on the total number of events in the time series. Some particular data combinations may result in spectra where significant periods are obscured by large amplitudes artifacts of the transform, but artifacts can be usually recognized because they lack harmonics; thus, in most of these cases, true semi-periodic sequences may not be identified, but no false identifications will be made. A first example of an application of the method to real seismicity data is the analysis of the Parkfield event series. The analysis correctly aftcasts the September 2004 earthquake. Further applications to real data from Japan and Venezuela are shown in a companion paper.

  10. Earthquake nucleation mechanisms and periodic loading: Models, Experiments, and Observations

    NASA Astrophysics Data System (ADS)

    Dahmen, K.; Brinkman, B.; Tsekenis, G.; Ben-Zion, Y.; Uhl, J.

    2010-12-01

    The project has two main goals: (a) Improve the understanding of how earthquakes are nucleated ¬ with specific focus on seismic response to periodic stresses (such as tidal or seasonal variations) (b) Use the results of (a) to infer on the possible existence of precursory activity before large earthquakes. A number of mechanisms have been proposed for the nucleation of earthquakes, including frictional nucleation (Dieterich 1987) and fracture (Lockner 1999, Beeler 2003). We study the relation between the observed rates of triggered seismicity, the period and amplitude of cyclic loadings and whether the observed seismic activity in response to periodic stresses can be used to identify the correct nucleation mechanism (or combination of mechanisms). A generalized version of the Ben-Zion and Rice model for disordered fault zones and results from related recent studies on dislocation dynamics and magnetization avalanches in slowly magnetized materials are used in the analysis (Ben-Zion et al. 2010; Dahmen et al. 2009). The analysis makes predictions for the statistics of macroscopic failure events of sheared materials in the presence of added cyclic loading, as a function of the period, amplitude, and noise in the system. The employed tools include analytical methods from statistical physics, the theory of phase transitions, and numerical simulations. The results will be compared to laboratory experiments and observations. References: Beeler, N.M., D.A. Lockner (2003). Why earthquakes correlate weakly with the solid Earth tides: effects of periodic stress on the rate and probability of earthquake occurrence. J. Geophys. Res.-Solid Earth 108, 2391-2407. Ben-Zion, Y. (2008). Collective Behavior of Earthquakes and Faults: Continuum-Discrete Transitions, Evolutionary Changes and Corresponding Dynamic Regimes, Rev. Geophysics, 46, RG4006, doi:10.1029/2008RG000260. Ben-Zion, Y., Dahmen, K. A. and J. T. Uhl (2010). A unifying phase diagram for the dynamics of sheared solids

  11. Multisatellite Observations of a Giant Pulsation Event

    NASA Astrophysics Data System (ADS)

    Takahashi, K.; Glassmeier, K.; Angelopoulos, V.; Bonnell, J. W.; Nishimura, T.; Singer, H. J.; Russell, C. T.

    2011-12-01

    Giant pulsations (Pgs; frequency ~10 mHz) were detected with ground magnetometers in the North American continent on October 2008, when the GOES-10, -11, -12, and -13 geostationary satellites and the THEMIS-A probe were magnetically connected to the region of the ground pulsation activity. This unique observational configuration allowed us to determine the properties of magnetospheric ultra-low-frequency (ULF) waves that caused the Pgs on the ground. All spacecraft detected monochromatic ULF waves at ~10 mHz, and the coherence between the Pg at the Gillam ground station and the ULF wave at THEMIS-A was high when the magnetic field foot point of the spacecraft came close to the ground station, indicating a causal relationship between the two oscillation phenomena. The ULF waves observed by the five spacecraft had perturbations in the radial and compressional components of the magnetic field and in the azimuthal component of the electric field, which are attributed to poloidal mode standing Alfvén waves. The poloidal waves were accompanied by multiharmonic toroidal waves, and from the frequency relationship among these, it is concluded that the ~10 mHz oscillations correspond to the fundamental (odd, or symmetric) mode. The standing wave mode also explains the amplitude variation with latitude and the phase delay between the magnetic and electric fields. Numerical models of poloidal waves incorporating finite ionospheric conductivity indicate that the fundamental mode interpretation is valid even when the damping of the standing waves is strong. Our observations are the most comprehensive to date in terms of spacecraft data, and we believe that theoretical work on the Pg generation mechanism should focus on mechanisms specific to odd mode standing waves, such as drift resonance of ring current ions.

  12. Multisatellite observations of a giant pulsation event

    NASA Astrophysics Data System (ADS)

    Takahashi, Kazue; Glassmeier, Karl-Heinz; Angelopoulos, Vassilis; Bonnell, John; Nishimura, Yukitoshi; Singer, Howard J.; Russell, Christopher T.

    2011-11-01

    Giant pulsations (Pgs; frequency ˜10 mHz) were detected with ground magnetometers on the North American continent on 19 October 2008, when the GOES-10, -11, -12, and -13 geostationary satellites and the THEMIS-A probe were magnetically connected to the region of the ground pulsation activity. This unique configuration allowed us to determine the properties of magnetospheric ultra-low-frequency (ULF) waves that caused the Pgs on the ground. All spacecraft detected monochromatic ULF waves at ˜10 mHz, and the coherence between the Pg at the Gillam ground station and the ULF wave at THEMIS-A was high when the magnetic field foot point of the spacecraft came close to the ground station. The ULF waves observed by the five spacecraft had perturbations in the radial and compressional components of the magnetic field and in the azimuthal component of the electric field, which are attributed to poloidal mode standing Alfvén waves. The poloidal waves were accompanied by multiharmonic toroidal waves, and from the frequency relationship among these, it is concluded that the ˜10 mHz oscillations correspond to the fundamental (odd, or symmetric) mode. The standing wave mode also explains the amplitude variation with latitude and the phase delay between the magnetic and electric fields. Numerical models of poloidal waves incorporating finite height integrated ionospheric conductivity indicate that the fundamental mode interpretation is valid even when the damping of the standing waves is strong. Our observations are the most comprehensive to date in terms of spacecraft data, and we believe that theoretical work on the Pg generation mechanism should focus on mechanisms specific to odd mode standing waves, such as drift resonance of ring current ions.

  13. γ-ray observations of extraterrestrial neutrino track events

    NASA Astrophysics Data System (ADS)

    Brown, Anthony M.; Adams, Jenni; Chadwick, Paula M.

    2015-07-01

    In this paper we report the results of a γ-ray study of IceCube's extraterrestrial neutrino candidates detected as track-like events. Using 70 months of Fermi-Large Area Telescope (LAT) observations, a likelihood analysis of all 1-300 GeV photons within 5° of the track-like neutrino candidates' origin was undertaken, to search for spatially coincident γ-ray emission. One of IceCube's HESE (High Energy Starting Event) track events was found to be spatially coincident with a γ-ray bright active galactic nucleus (AGN), PKS 0723-008. We find however that the chance probability for Fermi-LAT detected AGN to be spatially coincident with a single HESE track-like event is high (˜37 per cent). We therefore find no evidence of γ-ray emission associated with the detection of IceCube's HESE track-like neutrino candidates. Upper limits were calculated in the energy range of 1-300 GeV, assuming a point source origin for the neutrino events considered. The implications for the non-detection of γ-ray emission from the source of the HESE track-like events are briefly discussed. The large time period analysed in our study did however reveal two new γ-ray point sources. With a flux of (1.28 ± 0.08) × 10-9 photons cm-2 s-1, in the 1-300 GeV energy range, and an associated TS value of 220.6, one of these new point sources is positionally coincident with the AGN PKS 1346-112. The other point source has a 1-300 GeV flux of (7.95 ± 1.23) × 10-10 photons cm-2 s-1 and an associated TS value of 92.4. This new point source is spatially coincident with the radio source NVSS J072534 + 021645 suggesting that it too is an AGN.

  14. First observations of Trimpi events at Durban (L = 1. 69) using an OMSKI receiver

    SciTech Connect

    Friedel, R.H.W.; Hughes, A.R.W. ); Dowden, R.L.; Adams, C.D.D. )

    1993-02-01

    We report observations of transient ionospheric disturbances at VLF reflection heights, manifested as perturbations on sub-ionospherically propagating VLF transmitter signals: Trimpi events. Four VLF transmitter signals were monitored at Durban using an OM- SKI receiver. Both traditional Trimpi events and a new dome shaped event were observed at Durban. Occurrence of Trimpis at low L values can be interpreted as the precipitation of very high energy electrons which are capable of producing events during daylight, or as evidence of the fast Trimpi mechanism which could dominate at low L. The average winter event rate observed at Durban was quite low (7 per day on four transmitter signals) but during one very active period on the NAA-Durban signal 88 Trimpi events were observed in 2 hours. This activity was linked to an isolated thunderstorm occurring over the signal path over South Africa. 26 refs., 14 figs., 2 tabs.

  15. Characteristics of Long-Period Events Associated With Volcanic Degassing at Popocatepetl Volcano, Mexico.

    NASA Astrophysics Data System (ADS)

    Arciniega, A.; Chouet, B.; Dawson, P.

    2004-05-01

    Emissions of gas and ash dominate volcanic eruptive activity in Popocatepetl volcano since 1994. Volcanic eruptive activity consists of construction and destruction dome phases. Ash emissions ranged from small short-lived plumes rising a few hundred meters above the crater rim, to larger plumes reaching up to 15 km above the crater. Resulting tephra falls dusted the entire summit area. Bursts of volcanic degassing accompanied by long-period (LP) seismic signals observed as isolated events, or as sequences of discrete events with overall durations and amplitudes. Some gas emissions accompanied by persistent or spasmodic tremor. There are four families of LP events identified within the frequency range between 0.5 and 5 Hz. Family-one presents low-frequency emergent onsets with higher amplitudes at higher frequencies. Family-two includes emergent onsets with modulate amplitudes simulating tremor and dominant frequencies in defined picks in the band between 1 and 3 Hz. Family-three presents LP events with impulsive onset and decaying amplitude with time, these events present a wide range of amplitudes and dominant frequencies around 2 Hz. Family-four includes LP events with monochromatic appearance with sharp picks below 3 Hz. From thousands of LP events preliminary locations based on phase picks suggest that LP seismicity occur within uppermost 1000 m below the crater floor, consistently constrain defined clusters in the east-region of the crater and in the area where the domes growth. The network used to located LP events included 15 broadband stations distributed along radial profiles on the upper flanks of Popocatepetl. We report data collected during a broadband seismic experiment carried out at Popocatepetl Volcano as part of an international cooperative program between the GeoForschungsZentr um, Potsdam, Germany, the U.S. Geological Survey and the Institute of Geophysics, UNAM, MEXICO.

  16. Determining Optimal Machine Replacement Events with Periodic Inspection Intervals

    DTIC Science & Technology

    2013-03-01

    replacement policies for a generic machine with periodic inspection intervals. The considered reliability models consist of a single machine that can fail...during operation or else may be found to be inoperative during regularly-scheduled maintenance inspections. Most single-machine reliability models ...17 3.1 Model Development

  17. The complex frequencies of long-period seismic events as probes of fluid composition beneath volcanoes

    USGS Publications Warehouse

    Kumagai, H.; Chouet, B.A.

    1999-01-01

    Long-period (LP) events have been widely observed in relation to magmatic and hydrothermal activities in volcanic areas. LP waveforms characterized by their harmonic signature have been interpreted as oscillations of a fluid-filled resonator, and mixtures of liquid and gas in the form of bubbly liquids have been mainly assumed for the fluid. To investigate the characteristic properties of the resonator system, we analyse waveforms of LP events observed at four different volcanoes in Hawaii, Alaska, Colombia and Japan using a newly developed spectral method. This method allows an estimation of the complex frequencies of decaying sinusoids based on an autoregressive model. The results of our analysis show a wide variety of Q factors, ranging from tens to several hundred. We compare these complex frequencies with those predicted by the fluid-filled crack model for various mixtures of liquid, gas and ash. Although the oscillations of LP events with Q smaller than 50 can be explained by various combinations of liquids and gases, we find that ash-laden gases are required to explain long-lasting oscillations with Q larger than 100. The complex frequencies of LP events yield useful information on the types of fluids. Temporal and spatial variations of the complex frequencies can be used as probes of fluid composition beneath volcanoes.

  18. Cardiovascular events in patients with obesity: an observational study

    PubMed Central

    Buitrago, Francisco; Calvo, Juan Ignacio; Redondo-López, Verónica; Cañón-Barroso, Lourdes; Rodríguez-Pérez, Leoncio; Hinojosa-Díaz, José Francisco

    2010-01-01

    Background Overweight and obesity are positively correlated with increased risk of morbidity and mortality. Aim To evaluate whether obesity may be considered an independent cardiovascular risk factor in patients of ages from 35 to 74 years followed-up for 10 years. Design of study Observational, longitudinal retrospective study. Setting Primary care practices in Badajoz (Spain). Method A cohort of 899 patients (mean 55.7 years; 58.2% female) without evidence of cardiovascular disease was studied. Results A total of 33.5% of the population were obese (body mass index ≥30 kg/m2). Patients meeting the obesity criteria were more commonly female (36.6%) and were older, had higher mean values of blood pressure and triglycerides, higher percentages of diabetes, and higher coronary risk using either the original Framingham or the Framingham function calibrated for the Spanish population (Framingham-REGICOR). During the follow-up period, the rates of cardiovascular events and death in patients with obesity tended to be higher: 16.3% versus 11.7%, P = 0.056 and 4.7% versus 2.2%, P<0.05, respectively. In the final model of the logistic regression multivariate analysis, the significant predictors of cardiovascular events in patients with obesity were age, sex (male), diastolic blood pressure, diabetes, and smoking. The highest odds ratio corresponded to smoking (odds ratio 2.03; 95% confidence interval = 1.22 to 3.38). Conclusion Obesity may not be considered an independent cardiovascular risk factor in patients aged from 35 to 74 years followed-up for 10 years. PMID:20822691

  19. Observable consequences of event-by-event fluctuations of HBT radii

    NASA Astrophysics Data System (ADS)

    Plumberg, Christopher; Heinz, Ulrich

    2016-12-01

    We explore the effects of event-by-event fluctuations of Hanbury Brown-Twiss (HBT) radii and show how they can be observed experimentally. The relation of measured HBT radii extracted from ensemble-averaged correlation functions to the mean of their event-by-event probability distribution is clarified. We propose a method to experimentally determine the mean and variance of this distribution and test it on an ensemble of fluctuating events generated with the viscous hydrodynamic code VISH2+1. Using the same code, the sensitivity of the mean and variance of the HBT radii to the specific QGP shear viscosity η / s is studied. We report sensitivity of the mean pion HBT radii and their variances to the temperature dependence of η / s near the quark-hadron transition at a level similar (10-20%) to that which was previously observed for elliptic and quadrangular flow of charged hadrons [1].

  20. Two types of flow reversal events observed in magnetotail

    NASA Astrophysics Data System (ADS)

    Shinohara, I.; Nagai, T.; Fujimoto, M.; Kojima, H.; Zenitani, S.

    2015-12-01

    Geotail survey in magnetotail provides us with about 200 rapid flow reversal events where tailward flow (< -500 km/s) turns to earthward flow (> +300 km/s) within 10 minutes. We selected 46 definite flow reversal events from them in order to study the physics of X-lines, removing events where stationary plasma and/or tail lobe components are observed at the timing of flow reversals. We found that flow reversal events can be classified into two types according to electron heating/acceleration and low frequency wave activity. About 2/3 of the flow reversal events look "active." In these events, strong electron heating/acceleration and existence of ion-electron decoupling region are commonly observed. The intense wave active in the lower-hybrid frequency range is also observed even in high β region around the neutral sheet. These features are consistent with the collisionless reconnection model demonstrated by recent full kinetic numerical simulations. In contrast, other 1/3 of flow reversal events do not present any of them. No visible ion-electron decoupling is found in these "non-active" flow reversal events. This new finding indicates that the strong wave activity in the electric field would be related to the ion-electron decoupling process and that wave activity is a possible indicator for liveliness of reconnection (= evidence of fast electron flow). The fact that the non-active flow reversals tend to be distributed at the outer fringes of the active flow reversal regions implies that they are related to the three-dimensional structure of magnetic reconnection. In this presentation, we will discuss physical meaning of the difference between active and non-active flow reversal events. It is hard to discuss further collectively the nature of the non-active flow reversals only with single spacecraft measurements. This would be a good topic to be explored using multi-spacecraft data.

  1. 7 CFR 760.1001 - Eligible counties, disaster events, and disaster periods.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 7 2010-01-01 2010-01-01 false Eligible counties, disaster events, and disaster..., disaster events, and disaster periods. (a) Except as provided in this subpart, FSA will provide assistance... eligible disaster events in eligible disaster counties provided in paragraph (c) of this section. (b)...

  2. 7 CFR 760.1001 - Eligible counties, disaster events, and disaster periods.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 7 2011-01-01 2011-01-01 false Eligible counties, disaster events, and disaster..., disaster events, and disaster periods. (a) Except as provided in this subpart, FSA will provide assistance... eligible disaster events in eligible disaster counties provided in paragraph (c) of this section. (b)...

  3. 7 CFR 760.1001 - Eligible counties, disaster events, and disaster periods.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 7 2014-01-01 2014-01-01 false Eligible counties, disaster events, and disaster..., disaster events, and disaster periods. (a) Except as provided in this subpart, FSA will provide assistance... eligible disaster events in eligible disaster counties provided in paragraph (c) of this section. (b)...

  4. 7 CFR 760.1001 - Eligible counties, disaster events, and disaster periods.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 7 2013-01-01 2013-01-01 false Eligible counties, disaster events, and disaster..., disaster events, and disaster periods. (a) Except as provided in this subpart, FSA will provide assistance... eligible disaster events in eligible disaster counties provided in paragraph (c) of this section. (b)...

  5. 7 CFR 760.1001 - Eligible counties, disaster events, and disaster periods.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 7 2012-01-01 2012-01-01 false Eligible counties, disaster events, and disaster..., disaster events, and disaster periods. (a) Except as provided in this subpart, FSA will provide assistance... eligible disaster events in eligible disaster counties provided in paragraph (c) of this section. (b)...

  6. Periodic variability in cetacean strandings: links to large-scale climate events

    PubMed Central

    Evans, K; Thresher, R; Warneke, R.M; Bradshaw, C.J.A; Pook, M; Thiele, D; Hindell, M.A

    2005-01-01

    Cetacean strandings elicit much community and scientific interest, but few quantitative analyses have successfully identified environmental correlates to these phenomena. Data spanning 1920–2002, involving a total of 639 stranding events and 39 taxa groups from southeast Australia, were found to demonstrate a clear 11–13- year periodicity in the number of events through time. These data positively correlated with the regional persistence of both zonal (westerly) and meridional (southerly) winds, reflecting general long-term and large-scale shifts in sea-level pressure gradients. Periods of persistent zonal and meridional winds result in colder and presumably nutrient-rich waters being driven closer to southern Australia, resulting in increased biological activity in the water column during the spring months. These observations suggest that large-scale climatic events provide a powerful distal influence on the propensity for whales to strand in this region. These patterns provide a powerful quantitative framework for testing hypotheses regarding environmental links to strandings and provide managers with a potential predictive tool to prepare for years of peak stranding activity. PMID:17148151

  7. A study of the equatorial signatures of long period transient events (600 - 7200 s)

    NASA Astrophysics Data System (ADS)

    Santos, J.; Dutra, S.; Trivedi, N.; Vieira, L.; Echer, E.; Schuch, N.

    Transient variations in the H magnetic field component of magnetograms at high latitude are a common feature. They are associated with energy transference from solar wind to the magnetosphere. Abrupt changes in the solar wind generate Alfvén and fast mode waves through the magnetosphere. The Alfvén wave doesn't propagate in the direction perpendicular to the geomagnetic field, so equatorial signatures are probably caused by fast mode waves. On the other hand, complicated signatures observed at high latitudes represent a composition of Alfvén and fast mode waves. A second suggested propagation mechanism to low latitudes is the Earth-ionosphere wave-guide. In this work, geomagnetic data from the Brazilian magnetic stations at Belém (BLM), Eusébio (EUS), Ji-Paraná (JIP), São luis (SLZ) and São Martinho da Serra (SMS), all located near the geomagnetic equator, are used to look for equatorial signatures of transient events with periods of 600 - 7200s. This period range includes two special types of transient variations named Traveling convection vortices (TCV) and DP2 fluctuations. We try to identify their morphological characteristics and compare with the high latitude phenomena's characteristics. Satellite data (WIND, ACE and GOES) are used to see magnetosphere signatures and solar wind and interplanetary magnetic field (IMF) conditions during the events. The main objective is try to find the contribution of each propagation mechanism of these transient events arriving at the equatorial latitudes.

  8. Analysis of recurrent event data with incomplete observation gaps.

    PubMed

    Kim, Yang-Jin; Jhun, Myoungshic

    2008-03-30

    In analysis of recurrent event data, recurrent events are not completely experienced when the terminating event occurs before the end of a study. To make valid inference of recurrent events, several methods have been suggested for accommodating the terminating event (Statist. Med. 1997; 16:911-924; Biometrics 2000; 56:554-562). In this paper, our interest is to consider a particular situation, where intermittent dropouts result in observation gaps during which no recurrent events are observed. In this situation, risk status varies over time and the usual definition of risk variable is not applicable. In particular, we consider the case when information on the observation gap is incomplete, that is, the starting time of intermittent dropout is known but the terminating time is not available. This incomplete information is modeled in terms of an interval-censored mechanism. Our proposed method is applied to the study of the Young Traffic Offenders Program on conviction rates, wherein a certain proportion of subjects experienced suspensions with intermittent dropouts during the study.

  9. Location of long-period events below Kilauea Volcano using seismic amplitudes and accurate relative relocation

    USGS Publications Warehouse

    Battaglia, J.; Got, J.-L.; Okubo, P.

    2003-01-01

    We present methods for improving the location of long-period (LP) events, deep and shallow, recorded below Kilauea Volcano by the permanent seismic network. LP events might be of particular interest to understanding eruptive processes as their source mechanism is assumed to directly involve fluid transport. However, it is usually difficult or impossible to locate their source using traditional arrival time methods because of emergent wave arrivals. At Kilauea, similar LP waveform signatures suggest the existence of LP multiplets. The waveform similarity suggests spatially close sources, while catalog solutions using arrival time estimates are widely scattered beneath Kilauea's summit caldera. In order to improve estimates of absolute LP location, we use the distribution of seismic amplitudes corrected for station site effects. The decay of the amplitude as a function of hypocentral distance is used for inferring LP location. In a second stage, we use the similarity of the events to calculate their relative positions. The analysis of the entire LP seismicity recorded between January 1997 and December 1999 suggests that a very large part of the LP event population, both deep and shallow, is generated by a small number of compact sources. Deep events are systematically composed of a weak high-frequency onset followed by a low-frequency wave train. Aligning the low-frequency wave trains does not lead to aligning the onsets indicating the two parts of the signal are dissociated. This observation favors an interpretation in terms of triggering and resonance of a magmatic conduit. Instead of defining fault planes, the precise relocation of similar LP events, based on the alignment of the high-energy low-frequency wave trains, defines limited size volumes. Copyright 2003 by the American Geophysical Union.

  10. Body and Surface Wave Modeling of Observed Seismic Events

    DTIC Science & Technology

    1982-10-31

    COVERED Body and Surface Wave Modeling of Observed Seismic Events 1’ 6. PERFOkMING ORG. REPORT NUMBER 7. AUTHOR(e) S. CONTRACT OR GRANT NUMBER(s) David...Short Title of Work: Body and Surface Wave Modeling of Observed Seismic Events The views and conclusions contained in this document are those of the...synthetics generated with the Cogniard do-Hoop technique, P-SV modes, and DWFE codes. For a ten layered crust upper mantle model with a V bandwidth of 0-10

  11. 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

  12. Periodic Properties and Inquiry: Student Mental Models Observed during a Periodic Table Puzzle Activity

    ERIC Educational Resources Information Center

    Larson, Kathleen G.; Long, George R.; Briggs, Michael W.

    2012-01-01

    The mental models of both novice and advanced chemistry students were observed while the students performed a periodic table activity. The mental model framework seems to be an effective way of analyzing student behavior during learning activities. The analysis suggests that students do not recognize periodic trends through the examination of…

  13. OBSERVED CORE OF A GRADUAL SOLAR ENERGETIC PARTICLE EVENT

    SciTech Connect

    Kocharov, L.; Valtonen, E.; Reiner, M. J.; Thompson, B. J.; Klassen, A.

    2010-12-20

    Using space-borne particle and EUV detection and radio spectrograms from both ground-based and space-borne instruments, we study the first phase of the major solar energetic particle (SEP) event associated with the western solar flare and fast and wide coronal mass ejection (CME) on 2000 April 4. The SEP event being observed at the magnetic connection to the eruption's center starts with deka-MeV nucl{sup -1} helium- and relativistic electron-rich production from coronal sources identified with the electromagnetic diagnostics and the SEP event modeling. The broadband observations and modeling of the initial phase of the 'well-connected' major SEP event support the idea that acceleration of SEPs starts in the helium-rich plasma of the eruption's core in association with coronal shocks and magnetic reconnections caused by the CME liftoff, and that the coronal component dominates during the first hour of the SEP event considered, not yet being shielded by the CME bow shock in the solar wind. The first phase of the SEP event is followed by a second phase of SEP production associated with a decelerating CME-driven shock wave in the solar wind, which accelerates ions from a distinct, helium-poor seed particle population that may originate from the CME interaction with a coronal streamer.

  14. Source process of a long-period event at Kilauea volcano, Hawaii

    USGS Publications Warehouse

    Kumagai, H.; Chouet, B.A.; Dawson, P.B.

    2005-01-01

    We analyse a long-period (LP) event observed by a dense seismic network temporarily operated at Kilauea volcano, Hawaii, in 1996. We systematically perform spectral analyses, waveform inversions and forward modeling of the LP event to quantify its source process. Spectral analyses identify two dominant spectral frequencies at 0.6 and 1.3 Hz with associated Q values in the range 10-20. Results from waveform inversions assuming six moment-tensor and three single-force components point to the resonance of a horizontal crack located at a depth of approximately 150 m near the northeastern rim of the Halemaumau pit crater. Waveform simulations based on a fluid-filled crack model suggest that the observed frequencies and Q values can be explained by a crack filled with a hydrothermal fluid in the form of either bubbly water or steam. The shallow hydrothermal crack located directly above the magma conduit may have been heated by volcanic gases leaking from the conduit. The enhanced flux of heat raised the overall pressure of the hydrothermal fluid in the crack and induced a rapid discharge of fluid from the crack, which triggered the acoustic vibrations of the resonator generating the LP waveform. The present study provides further support to the idea that LP events originate in the resonance of a crack. ?? 2005 RAS.

  15. Optimizing observing sequence design for periodic and non-periodic phenomena : a Bayesian approach

    NASA Technical Reports Server (NTRS)

    Johnston, Mark D.; Knight, Russell

    2005-01-01

    In this paper we report on our progress on addressing these issues. We have developed an approximate expression for the uniformity of phase coverage that can be used when scheduling to assess candidate sample times. We describe the results obtained using this estimator, and compare them with detailed simulations. We describe our progress and plans for integrating optimizing criteria for both periodic and non-periodic observations into a single observation sequence.

  16. Stochastic Event Counter for Discrete-Event Systems Under Unreliable Observations

    SciTech Connect

    Tae-Sic Yoo; Humberto E. Garcia

    2008-06-01

    This paper addresses the issues of counting the occurrence of special events in the framework of partiallyobserved discrete-event dynamical systems (DEDS). First, we develop a noble recursive procedure that updates active counter information state sequentially with available observations. In general, the cardinality of active counter information state is unbounded, which makes the exact recursion infeasible computationally. To overcome this difficulty, we develop an approximated recursive procedure that regulates and bounds the size of active counter information state. Using the approximated active counting information state, we give an approximated minimum mean square error (MMSE) counter. The developed algorithms are then applied to count special routing events in a material flow system.

  17. Thirty Years of Natural Satellites Mutual Events Observations

    NASA Astrophysics Data System (ADS)

    Arlot, Jean-eudes; Events Observers, Mutual

    2009-09-01

    Phenomena in the Solar System have been observed for years: solar and lunar eclipses, occultations of stars by the Moon and the asteroids, eclipses of the satellites of Jupiter. Since 1973, mutual occultations and eclipses of the satellites of Jupiter, Saturn and Uranus were observed extensively during each opportunity i.e. the equinox on the planet: why? The study of the systems of natural satellites needs to explore the dynamics of these objects: each small dynamical effect is the signature of some physical property. In order to validate the theoretical models, very accurate observations are needed. Most of the direct astrometric observations have their accuracy limited by the diffraction of the light in the telescope and by the star catalogues used for calibration. Phenomena have not this limitation: the accuracy is not in angle but in kilometres in space. Since, the observed satellites have no atmosphere, these photometric events are easy to analyse providing relative positions accurate to a few kilometres corresponding to a few mas in geocentric angle. More, during an occultation, the surface of the satellites may be studied: volcanoes of Io (positions and fluxes) were observed that way. Mutual events observations together with the best observations made since several decades allowed improving dynamical models of the satellites systems of Jupiter, Saturn and Uranus. Concerning Io, the dissipation of energy in its internal structure by the Jovian tides has been made into evidence thanks to fitting the models on accurate observations including mutual events. Eight observational campaigns were organized for the Jovian satellites, three for the Saturnians and one for the Uranians providing more than 1400 light curves (see the data base at http://www.imcce.fr/fr/ephemerides/generateur/saimirror/obsindhe.htm ). The author acknowledges the numerous observers worldwide who provide the observations, the observatories permitting observations and the French CNRS who

  18. Wavefield properties of a shallow long-period event and tremor at Kilauea Volcano, Hawaii

    USGS Publications Warehouse

    Saccorotti, G.; Chouet, B.; Dawson, P.

    2001-01-01

    The wavefields of tremor and a long-period (LP) event associated with the ongoing eruptive activity at Kilauea Volcano, Hawaii, are investigated using a combination of dense small-aperture (300 m) and sparse large-aperture (5 km) arrays deployed in the vicinity of the summit caldera. Measurements of azimuth and slowness for tremor recorded on the small-aperture array indicate a bimodal nature of the observed wavefield. At frequencies below 2 Hz, the wavefield is dominated by body waves impinging the array with steep incidence. These arrivals are attributed to the oceanic microseismic noise. In the 2-6 Hz band, the wavefield is dominated by waves propagating from sources located at shallow depths (<1 km) beneath the eastern edge of the Halemaumau pit crater. The hypocenter of the LP event, determined from frequency-slowness analyses combined with phase picks, appears to be located close to the source of tremor but at a shallower depth (<0.1 km). The wavefields of tremor and LP event are characterized by a complex composition of body and surface waves, whose propagation and polarization properties are strongly affected by topographic and structural features in the summit caldera region. Analyses of the directional properties of the wavefield in the 2-6 Hz band point to the directions of main scattering sources, which are consistent with pronounced velocity contrasts imaged in a high-resolution three-dimensional velocity model of the caldera region. The frequency and Q of the dominant peak observed in the spectra of the LP event may be explained as the dominant oscillation mode of a crack with scale length 20-100 m and aperture of a few centimeters filled with bubbly water. The mechanism driving the shallow tremor appears to be consistent with a sustained excitation originating in the oscillations of a bubbly cloud resulting from vesiculation and degassing in the magma. ?? 2001 Elsevier Science B.V. All rights reserved.

  19. Photometric, astrometric and polarimetric observations of gravitational microlensing events

    NASA Astrophysics Data System (ADS)

    Sajadian, Sedighe; Rahvar, Sohrab

    2015-09-01

    Gravitational microlensing can be used as a unique astrophysical tool to study the atmospheres of stars thousands of parsec away from us. This capability results from the bending of light rays in the gravitational field of a lens that can magnify the light of a background source star during the lensing. Moreover, one of the consequences of this light bending is that the circular symmetry of the source is broken because distorted images are produced at either side of the lens position. This property makes it possible to observe polarization, and also the light centroid shift of images. Assigning vectors for these two parameters, they are perpendicular to each other in simple and binary microlensing events, except in fold singularities. In this work, we investigate the advantages of polarimetric and astrometric observations during microlensing events (i) for studying the surface of the source star and spots on it and (ii) for obtaining extra information to determine the trajectory of source stars with respect to the lens. Finally, we analyse the largest sample of microlensing events from the Optical Gravitational Lensing Experiment (OGLE) catalogue and show that, for almost ˜4.3 per cent of events in the direction of the Galactic bulge, the polarization signals would be observable with large telescopes.

  20. ICME events at Mars: MAVEN observations and models

    NASA Astrophysics Data System (ADS)

    Curry, Shannon; Luhmann, Janet; Dong, Chuanfei; Hara, Takuya; Leblanc, Francois; Modolo, Ronan; Fraenz, Markus; Holmstrom, Mats; Ramstad, Robin; Juan Ma, Ying; Halekas, Jasper; Gruesbeck, Jacob; Dong, Yaxue; Brain, David; McFadden, James; Connerney, Jack; Mitchell, David; Fillingim, Matt; Espley, Jared; Jakosky, Bruce

    2016-04-01

    The MAVEN spacecraft has observed the Mars upper atmosphere, ionosphere, magnetic topology and interactions with the Sun and solar wind during numerous Interplanetary Coronal Mass Ejection (ICME) impacts spanning from March 2015 to January 2016. Observations include dramatic changes in the bow shock and magnetosheath boundaries, open and closed magnetic field lines, and extreme enhancements of escaping and precipitating pick-up ions. We will compare three ICMEs using MAVEN and MEX observations at Mars, with an emphasis on the response of the planetary pick-up ions. Additionally, we will present global MHD and test particle simulations of the ICMEs using MAVEN and MEX observations as initial conditions, which show a significant enhancement in the nonthermal escape of planetary ions during these events. We also will put the observed ICME events in context with a model of an idealized extreme ICME interacting with Mars. Accordingly, atmospheric escape during extreme solar events in Mars' early history may have been a significant contributor to the evolution of the Martian atmosphere and may also have implications for exoplanets interacting with younger, more active stars.

  1. Long-term Spatial and Temporal Variations of Aurora Borealis Events in the Period 1700 - 1905

    NASA Astrophysics Data System (ADS)

    Vázquez, M.; Vaquero, J. M.; Gallego, M. C.

    2014-05-01

    Catalogues and other records of aurora-borealis events were used to study the long-term spatial and temporal variation of these phenomena in the period from 1700 to 1905 in the Northern Hemisphere. For this purpose, geographic and geomagnetic coordinates were assigned to approximately 27 000 auroral events with more than 80 000 observations. They were analyzed separately in three large-scale areas: i) Europe and North Africa, ii) North America, and iii) Asia. There was a clear need to fill some gaps existing in the records so as to have a reliable proxy of solar activity, especially during the 18th century. In order to enhance the long-term variability, an 11-year smoothing window was applied to the data. Variations in the cumulative numbers of auroral events with latitude (in both geographic and geomagnetic coordinates) were used to discriminate between the two main solar sources: coronal mass ejections and high-speed streams from coronal holes. The characteristics of the associated auroras correlate differently with the solar-activity cycle.

  2. Semi-Periodic Sequences and Extraneous Events in Earthquake Forecasting. II: Application, Forecasts for Japan and Venezuela

    NASA Astrophysics Data System (ADS)

    Quinteros Cartaya, Claudia Beatriz; Nava Pichardo, Fidencio Alejandro; Glowacka, Ewa; Frez Cárdenas, José Duglas

    2014-07-01

    In order to analyze observed seismicity in central Japan and Venezuela, we applied a new method to identify semi-periodic sequences in the occurrence times of large earthquakes, which allows for the presence of multiple periodic sequences and/or events not belonging to any sequence in the time series. We also explored a scheme for diminishing the effects of a sharp cutoff magnitude threshold in selecting the events to analyze. A main four-event sequence with probability P c = 0.991 of not having occurred by chance was identified for earthquakes with M ≥ 8.0 in central Japan. Venezuela is divided, from West to East, into four regions; for each of these, the magnitude ranges and identified sequences are as follows. Region 1: M ≥ 6.0, a six-event sequence with P c = 0.923, and a four-event sequence with P c = 0.706. Region 2: M ≥ 5.6, a five-event sequence with P c = 0.942. Region 3: M ≥ 5.6, a four-event sequence with P c = 0.882. Region 4: M ≥ 6.0, a five-event sequence with P c = 0.891. Forecasts are made and evaluated for all identified sequences having four or more events and probabilities ≥0.5. The last event of all these sequences was satisfactorily aftcast by previous events. Whether the identified sequences do, in fact, correspond to physical processes resulting in semi-periodic seismicity is, of course, an open question; but the forecasts, properly used, may be useful as a factor in seismic hazard estimation.

  3. Synoptic Evolution of the Arctic Vortex During Elevated Stratopause Events: WACCM vs. Observations

    NASA Astrophysics Data System (ADS)

    Harvey, V.; Collins, R. L.; Randall, C. E.

    2013-12-01

    The structure of the Arctic polar vortex is diagnosed during 15 elevated stratopause (ES) events using 40 years of output from the Whole Atmosphere Community Climate Model (WACCM). For each event, stratopause height maxima are interpreted in the context of the structure of the Arctic vortex. The WACCM results are compared to the 2006, 2009, 2012, and 2013 ES events observed by the Microwave Limb Sounder (MLS) and the Arctic vortex in the Goddard Earth Observing System (GEOS) version 5 analyses. The stratopause first reforms at high altitudes over confined geographic regions before it becomes elevated over the entire polar cap. Thus, defining the day that the stratopause reformed using polar cap averaged temperatures results in a later date than if polar maps of stratopause height are used. Even once an ES event has started based on polar cap mean temperatures, the ES is not at a uniform altitude over the polar cap. Complex patterns change rapidly from day-to-day. ES events simulated by WACCM are zonally asymmetric 33% of the time due to large amplitude planetary waves in the upper stratosphere. This frequency agrees with observations in that the 2012 ES event was zonally asymmetric. For the 66% of ES events that are zonally symmetric in a monthly mean following each event, there are significant periods when zonal symmetry is violated and the vortex structure tilts westward with height over 270o in longitude.

  4. Quasi-periodic events in crystal plasticity and the self-organized avalanche oscillator.

    PubMed

    Papanikolaou, Stefanos; Dimiduk, Dennis M; Choi, Woosong; Sethna, James P; Uchic, Michael D; Woodward, Christopher F; Zapperi, Stefano

    2012-10-25

    When external stresses in a system--physical, social or virtual--are relieved through impulsive events, it is natural to focus on the attributes of these avalanches. However, during the quiescent periods between them, stresses may be relieved through competing processes, such as slowly flowing water between earthquakes or thermally activated dislocation flow between plastic bursts in crystals. Such smooth responses can in turn have marked effects on the avalanche properties. Here we report an experimental investigation of slowly compressed nickel microcrystals, covering three orders of magnitude in nominal strain rate, in which we observe unconventional quasi-periodic avalanche bursts and higher critical exponents as the strain rate is decreased. Our experiments are faithfully reproduced by analytic and computational dislocation avalanche modelling that we have extended to incorporate dislocation relaxation, revealing the emergence of the self-organized avalanche oscillator: a novel critical state exhibiting oscillatory approaches towards a depinning critical point. This theory suggests that whenever avalanches compete with slow relaxation--in settings ranging from crystal microplasticity to earthquakes--dynamical quasi-periodic scale invariance ought to emerge.

  5. Origin of Observed Periodic Components in Astrophysical Masers' Spectra

    NASA Astrophysics Data System (ADS)

    Siparov, S.; Samodurov, V.; Laptev, G.

    2017-01-01

    Further analysis of data previously obtained during the monitoring observations of 49 astrophysical water (22 GHz) masers shows that in some cases the intensity of an individual component of the maser spectrum changes periodically, on timescales of tens of minutes. It is argued that this variation cannot be the effect of instrumental errors, weather conditions or interstellar medium instabilities, because only a single feature of the maser spectrum fluctuates but not the whole spectrum. The suggested interpretation of this effect is based on the optic-metrical parametric resonance produced by gravitational radiation emitted by short-period binary stars, with the examples of such binaries sufficing the conditions given.

  6. Identifying Long-period Planets from Single Transit Events with the MEarth Project

    NASA Astrophysics Data System (ADS)

    Dittmann, Jason; Irwin, Jonathan; Charbonneau, David; Bonfils, Xavier; Astudillo, Nicola; Newton, Elisabeth R.; Berta-Thompson, Zachory K.

    2017-01-01

    The MEarth Project consists of 2 arrays of 8 telescopes each, one in the northern hemisphere at Mt. Hopkins, AZ and one in the southern hemisphere at CTIO, Chile. MEarth is monitoring the stars with estimated radii less than 0.3 solar radii and estimated distances within 33 parsecs for transiting exoplanets. Rocky planets transiting these small, nearby stars are ideal targets for atmospheric characterization with JWST and the ELTs, as the relative signal size is larger than for planets around main-sequence FGK stars, and the star’s proximity ensures a high photon rate. Planets in the habitable zone of these stars will have orbital periods of several weeks. Thus, we would typically have only one or a few observable transits per observing season per site. Our strategy to discover these planets is to identify them in real time from a single (partial) transit event, and subsequently determine the orbital periods from radial velocity measurements. This, in turn, would allow us to predict future transits. MEarth generates a large number of triggers; we used machine learning methods informed by atmospheric and observatory state variables to cull this list. We are gathering radial velocity measurements for our top resulting candidates and will present an update on their status.The MEarth Project gratefully acknowledges funding from the David and Lucile Packard Foundation and the National Science Foundation. This work was made possible by a grant from the John Templeton Foundation. EN is supported by an NSF Astronomy and Astrophysics Postdoctoral Research Fellowship.

  7. Observations and modeling of dynamically triggered high frequency burst events

    NASA Astrophysics Data System (ADS)

    Fischer, Adam David

    2008-10-01

    A series of high-frequency (>20Hz) bursts of energy are observed on strong motion records during the 1999 Chi-Chi, Taiwan Earthquake Mw7.6. We hypothesized that these bursts originated near the individual stations as small, shallow events that were dynamically triggered by the P- and S-waves generated by the Chi-Chi mainshock. These bursts were originally interpreted as a mainshock source signal by Chen et al., [2006] but our observations of events on strong motion records recorded at stations up to 170 km from the mainshock epicenter is consistent with the local triggering hypothesis. If the bursts originated on the Chi-Chi fault plane, as hypothesized by Chen et al. [2006] based on their analysis of recordings within 20Km from the Chelungpu fault, then they should not be observable at this distance assuming any reasonable value of crustal attenuation. The bursts on all strong motion stations in the Taiwan Central Weather Bureau network (TWCB) were identified using a numerical algorithm approach. This data set was analyzed in the context of local dynamic triggering which resulted in a stress threshold for triggering in the range 0.03 to 0.05 MPa for S-wave triggering and 0.0013 to 0.0033 MPa for P-wave triggering, consistent with prior observations of surface wave triggering. In an attempt to better characterize the nature of high frequency bursts, similar analysis of strong motion records was performed on the records of the 2004 Parkfield, CA earthquake (Mw6) at the USGS UPSAR array. The average array spacing was relatively small compared to the instruments in Taiwan so that further constraint of the location of bursts was possible. Bursts were found to be incoherent even for stations spaced 40m apart, suggesting that they occur in a region approximately 20m from the stations. The triggering threshold was found to be ~0.02Mpa, consistent with the observations from Taiwan. To test the possibility of nucleating unstable slip events in the very shallow crust we

  8. New particle formation events observed at a high altitude site Pico Espejo, Venezuela

    NASA Astrophysics Data System (ADS)

    Nieminen, Tuomo; Kontkanen, Jenni; Krejci, Radovan; Ström, Johan; Tunved, Peter; Hamburger, Thomas; Calderon, Silvia; Hoffman, Pedro

    2013-05-01

    Formation and growth events of nucleation mode particles (10-25 nm in diameter) were analyzed from 27 month period of particle size distribution measurements at the high altitude site Pico Espejo in Venezuela. Particle formation was observed both in air masses connected to boundary layer air and in free tropospheric conditions. The frequency and magnitude of particle formation at this high altitude site was comparable to many observations at lower altitude sites.

  9. 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

  10. Event-by-event study of neutron observables in spontaneous and thermal fission

    SciTech Connect

    Vogt, R; Randrup, J

    2011-09-14

    The event-by-event fission model FREYA is extended to spontaneous fission of actinides and a variety of neutron observables are studied for spontaneous fission and fission induced by thermal neutrons with a view towards possible applications for SNM detection. We have shown that event-by-event models of fission, such as FREYA, provide a powerful tool for studying fission neutron correlations. Our results demonstrate that these correlations are significant and exhibit a dependence on the fissioning nucleus. Since our method is phenomenological in nature, good input data are especially important. Some of the measurements employed in FREYA are rather old and statistics limited. It would be useful to repeat some of these studies with modern detector techniques. In addition, most experiments made to date have not made simultaneous measurements of the fission products and the prompt observables, such as neutron and photons. Such data, while obviously more challenging to obtain, would be valuable for achieving a more complete understanding of the fission process.

  11. Skylab ATM/S-056 X-ray event analyzer observations versus solar flare activity: An event compilation. [tables (data)

    NASA Technical Reports Server (NTRS)

    Wilson, R. M.

    1977-01-01

    An event compilation is presented which correlates ATM/S-056 X-ray event analyzer solar observations with solar flare activity. Approximately 1,070 h of pulse height analyzed X-ray proportional counter data were obtained with the X-ray event analyzer during Skylab. During its operation, 449 flares (including 343 flare peaks) were observed. Seventy events of peak X-ray emission or = Cl were simultaneously observed by ground based telescopes, SOLRAD 9 and/or Vela, and the X-ray event analyzer. These events were observed from preflare through flare rise to peak and through flare decline.

  12. Periodic Impact Cratering and Extinction Events Over the Last 260 Million Years

    NASA Technical Reports Server (NTRS)

    Rampino, Michael R.; Caldeira, Ken

    2015-01-01

    The claims of periodicity in impact cratering and biological extinction events are controversial. Anewly revised record of dated impact craters has been analyzed for periodicity, and compared with the record of extinctions over the past 260 Myr. A digital circular spectral analysis of 37 crater ages (ranging in age from 15 to 254 Myr ago) yielded evidence for a significant 25.8 +/- 0.6 Myr cycle. Using the same method, we found a significant 27.0 +/- 0.7 Myr cycle in the dates of the eight recognized marine extinction events over the same period. The cycles detected in impacts and extinctions have a similar phase. The impact crater dataset shows 11 apparent peaks in the last 260 Myr, at least 5 of which correlate closely with significant extinction peaks. These results suggest that the hypothesis of periodic impacts and extinction events is still viable.

  13. Saturn's planetary period oscillations observed during 10 years of Cassini

    NASA Astrophysics Data System (ADS)

    Provan, Gabrielle; Andrews, David; Cowley, Stanley; Dougherty, Michele

    2014-05-01

    Planetary period oscillations (PPOs) with periods close to Saturn's rotational period are ubiquitous throughout Saturn's magnetospheric system. Here we review the observational studies of PPOs determined from magnetospheric magnetic field data throughout the Cassini mission to date. As first shown using radio data, two oscillatory systems are present, one associated with the northern polar region and the other with the southern. We show that within the northern (southern) open-field polar region only the northern (southern) PPO oscillations are detected. However, within the equatorial 'core' region of Saturn's magnetosphere (dipole L ≤ 12), the two oscillations are superposed and interfere. The PPO periods are shown to lie in the range ~10.6 to 10.8 h, are persistently shorter north than south to date, and undergo a strong seasonal cycle together with the oscillation amplitudes. We discuss these observations in relation to theoretical models that have been proposed to explain them, and emphasize the importance of continued measurement of their properties during the Cassini solstice mission.

  14. Ulysses particle observations of the March 1991 solar flare events

    NASA Technical Reports Server (NTRS)

    Sanderson, T. R.; Marsden, R. G.; Heras, A. M.; Wenzel, K.-P.; Anglin, J. D.; Balogh, A.; Forsyth, R.

    1992-01-01

    Observations of energetic ions from the COSPIN instrument on the Ulysses spacecraft at 2.5 AU during the March 1991 series of solar flare events arae presented. The intensity profiles observed during this sequence of events were affected both by the presence of interplanetary shocks and large-scale discontinuities in the magnetic field, the low-energy (about 1 MeV) protons being influenced mainly by the shocks and the discontinuities, and the high-energy (about 100 MeV) protons by the discontinuities. The first shock observed at Ulysses was followed by several discontinuities and a Coronal Mass Ejection (CME) which were probably moving with the shock. Particles following this shock were prevented from propagating freely into the heliosphere by the structure moving with the shock, and were carried along with it. A second shock was followed by a region containing bi-directional particle anisotropies. A subsequent enhancement of low-energy particles suggests the passage of another shock. This was followed by a slow intensity decay which coincided with a second CME and where bi-directional particle anisotropies were again observed.

  15. Limb Event Brightenings and Fast Ejection Using IRIS Mission Observations

    NASA Astrophysics Data System (ADS)

    Tavabi, E.; Koutchmy, S.; Golub, L.

    2015-10-01

    The Interface Region Imaging Spectrograph (IRIS) of the recently commissioned NASA small explorer mission provides significantly more complete and higher resolution spectral coverage of the dynamical conditions inside the chromosphere and transition region (TR) than has been available ever before. High temporal, spatial (0.3'') and spectral resolution observations from the ultraviolet IRIS spectra near the solar limb reveal high-energy limb event brightenings (LEBs) at low chromospheric heights at about 1 Mm above the limb. They can be characterized as explosive events producing jets. We selected two events showing spectra of a confined eruption just off or near the quiet-Sun limb, the jet part showing obvious moving material with short-duration large Doppler shifts in three directions that were identified as macrospicules on slit-jaw (SJ) images in Si iv and He ii 304 Å. The events were analyzed from a sequence of very close rasters taken near the central meridian and the South Pole limb. We analyzed the processed SJ images and the simultaneously observed fast spectral sequences, which have large Doppler shifts, with a pair of redshifted elements together with a faster blueshifted element from almost the same position. Shifts correspond to velocities of up to 100 km s^{-1} in projection on the plane of the sky. Erupting spicules and macrospicules from these regions are visible in images taken before and after the spectra. The cool low first ionization potential (FIP) element simultaneous line emissions of the Mg ii h and k resonance lines do not clearly show a similar signature because of optical thickness effects, but the Si iv broadband SJ images do. The bidirectional plasma jets ejected from a small reconnection site are interpreted to be the result of coronal loop-loop interactions that lead to reconnection in nearby sites.

  16. Analyzing and Identifying Teens Stressful Periods and Stressor Events from a Microblog.

    PubMed

    Li, Qi; Xue, Yuanyuan; Zhao, Liang; Jia, Jia; Feng, Ling

    2016-06-30

    Increased health problems among adolescents caused by psychological stress have aroused worldwide attention. Long-standing stress without targeted assistance and guidance negatively impacts the healthy growth of adolescents, threatening the future development of our society. So far, research focused on detecting adolescent psychological stress revealed from each individual post on microblogs. However, beyond stressful moments, identifying teens stressful periods and stressor events that trigger each stressful period is more desirable to understand the stress from appearance to essence. In this paper, we define the problem of identifying teens stressful periods and stressor events from the open social media microblog. Starting from a case study of adolescents' posting behaviors during stressful school events, we build a poisson-based probability model for the correlation between stressor events and stressful posting behaviors through a series of posts on Tencent Weibo (referred to as the microblog throughout the paper). With the model, we discover teen's maximal stressful periods and further extract details of possible stressor events that cause the stressful periods. We generalize and present the extracted stressor events in a hierarchy based on common stress dimensions and event types. Taking 122 scheduled stressful study-related events in a high school as the ground truth, we test the approach on 124 students' posts from January 1, 2012 to February 1, 2015, and obtain some promising experimental results: (stressful periods: recall 0.761, precision 0.737, and F1-measure 0.734) and (top-3 stressor events: recall 0.763, precision 0.756, and F1-measure 0.759). The most prominent stressor events extracted are in the self-cognition domain, followed by the school life domain. This conforms to the adolescent psychological investigation result that problems in school life usually accompanied with teens inner cognition problems. Compared with the state-of-art top-1

  17. MESSENGER Observations of Large Flux Transfer Events at Mercury

    NASA Technical Reports Server (NTRS)

    Slavin, James A.; Lepping, Ronald P.; Wu, Chin-Chun; Anderson, Brian J.; Baker, Daniel N.; Benna, Mehdi; Boardsen, Scott A.; Killen, Rosemary M.; Korth, Haje; Krimigis, Stamatios M.; McClintock, William E.; McNutt, Ralph L., Jr.; Sarantos, Menelaos; Schriver, David; Solomon, Sean C.; Travnicek, Pavel; Zurbuchen, Thomas H.

    2010-01-01

    Six flux transfer events (FTEs) were encountered during MESSENGER's first two flybys of Mercury (M1 and M2). For M1 the interplanetary magnetic field (IMF) was predominantly northward and four FTEs with durations of 1 to 6 s were observed in the magnetosheath following southward IMF turnings. The IMF was steadily southward during M2, and an FTE 4 s in duration was observed just inside the dawn magnetopause followed approx. 32 s later by a 7 s FTE in the magnetosheath. Flux rope models were fit to the magnetic field data to determine FTE dimensions and flux content. The largest FTE observed by MESSENGER had a diameter of approx. 1 R(sub M) (where R(sub M) is Mercury s radius), and its open magnetic field increased the fraction of the surface exposed to the solar wind by 10 - 20 percent and contributed up to approx. 30 kV to the cross-magnetospheric electric potential.

  18. MESSENGER Observations of Large Flux Transfer Events at Mercury

    NASA Technical Reports Server (NTRS)

    Slavin, James A.; Lepping, Ronald P.; Wu, Chin-Chun; Anderson, Brian J.; Baker, Daniel N.; Benna, Mehdi; Boardsen, Scott A.; Killen, Rosemary M.; Korth, Haje; Krimigis, Stamatios M.; McClintock, William E.; McNutt, Ralph L., Jr.; Sarantos, Menelaos; Schriver, David; Solomon, Sean C.; Travnicek, Pavel; Zurbuchen, Thomas H.

    2010-01-01

    Six flux transfer events (FTEs) were encountered during MESSENGER's first two flybys of Mercury (MI and M2). For MI the interplanetary magnetic field (IMF) was predominantly northward and four FTEs with durations of 1 to 6 s were observed in the magnetosheath following southward 1M F turnings. The IMF was steadily southward during M2, and an FTE 4 s in duration was observed just inside the dawn magnetopause followed approx.32 s later by a 7-s FTE in the magnetosheath. Flux rope models were fit to the magnetic field data to detem11ne PTE dimensions and flux content The largest FTE observed by MESSENGER had a diameter of approx. 1 R(sub M) (where R(sub M) is Mercury's radius), and its open magnetic field increased the fraction of the surface exposed to the solar wind by 10 - 20 percent and contributed up to approx.30 kV to the cross-magnetospheric electric potential.

  19. VLP-Discriminated Strombolian Event Families and Video Observations at Mount Erebus, Antarctica

    NASA Astrophysics Data System (ADS)

    Aster, R. C.; Mah, S. Y.; McNamara, S.; Ruiz, M.; Kyle, P.; McIntosh, W.; Dunbar, N.

    2002-12-01

    Strombolian eruptive activity from the phonolitic lava lake of Mt. Erebus generates VLP (Very Long Period) signals with spectral components as grave as 20 s. These signals have been observed on a seasonal basis with broadband seismometers during three Antarctic field seasons in targeted PASSCAL deployments and, more recently, with permanently installed broadband seismometers. Associated eruptive and other lava lake behavior has also been observed since 2000 with a time-stamped crater surveillance video camera. VLP signals persist for several minutes during lava lake refilling following eruptions and have highly similar waveform characteristics from event to event. The initial few seconds of signal associated with the pre-eruptive phase, however, exhibit significant variations and can be readily classified into 3 families, two simply based on initial polarity. A third event family, infrequently observed, shows a very different pulse-like shape and different frequency content. Video observation of eruptions suggest a correlation between the eruptive character and the initial polarity of the event. Positive polarity events have a vertical, jet-like eruptive style, while negative polarity events feature more radial ejecta. All lava lake eruptions are due to simple Strombolian gas slugs nucleating in the near-summit conduit system, becoming dislodged from buoyancy forces, and rising nearly intact to the lake surface. Distinct families of eruptive styles from a single vent and their correlation with VLP signals generated by ascent forces suggest distinct source zones and/or delivery paths of gas slugs to the lava lake surface.

  20. Solar particle events observed at Mars: dosimetry measurements and model calculations.

    PubMed

    Cleghorn, Timothy F; Saganti, Premkumar B; Zeitlin, Cary J; Cucinotta, Francis A

    2004-01-01

    During the period from March 13, 2002 to mid-September, 2002, six solar particle events (SPE) were observed by the MARIE instrument onboard the Odyssey Spacecraft in Martian Orbit. These events were observed also by the GOES 8 satellite in Earth orbit, and thus represent the first time that the same SPE have been observed at these separate locations. The characteristics of these SPE are examined, given that the active regions of the solar disc from which the event originated can usually be identified. The dose rates at Martian orbit are calculated, both for the galactic and solar components of the ionizing particle radiation environment. The dose rates due to galactic cosmic rays (GCR) agree well with the HZETRN model calculations.

  1. Solar particle events observed at Mars: dosimetry measurements and model calculations

    NASA Technical Reports Server (NTRS)

    Cleghorn, Timothy F.; Saganti, Premkumar B.; Zeitlin, Cary J.; Cucinotta, Francis A.

    2004-01-01

    During the period from March 13, 2002 to mid-September, 2002, six solar particle events (SPE) were observed by the MARIE instrument onboard the Odyssey Spacecraft in Martian Orbit. These events were observed also by the GOES 8 satellite in Earth orbit, and thus represent the first time that the same SPE have been observed at these separate locations. The characteristics of these SPE are examined, given that the active regions of the solar disc from which the event originated can usually be identified. The dose rates at Martian orbit are calculated, both for the galactic and solar components of the ionizing particle radiation environment. The dose rates due to galactic cosmic rays (GCR) agree well with the HZETRN model calculations. Published by Elsevier Ltd on behalf of COSPAR.

  2. The Search for Periodic Components in Observational Data

    NASA Astrophysics Data System (ADS)

    Baluev, R. V.

    2014-09-01

    This review is devoted to the problem of searching for periodicities in observational data using periodograms based on the general statistical likelihood ratio test and special variants of it, including the classical Lomb-Scargle periodogram. Primary emphasis is on the problem of estimating the statistical significance of the periodicities detected in this manner. We assume that a universal solution of this problem exists involving an effective method in which the periodogram is regarded as a random process (or random field), while an approximation for the required "false alarm probability" is constructed by a generalized Rice method. Besides a unified method for determining the expected noise levels (or significance levels) of these periodograms, we also examine some important special cases with different models of periodic signals (linear and nonlinear). The false alarm probability associated with an observed signal is approximated in most cases by a formula of the type , where z is the observed maximum readout in the periodogram and P is an algebraic polynomial with coefficients that depend on the conditions of the problem. We also examine the problem of separating composite signals with several frequencies from noise. In this case correct analysis of the data requires the use of so-called multifrequency periodograms based on models of signals containing several periodic components. We show that a complete solution to this problem requires construction of 2n-1 such periodograms, where n is the total number of possible frequencies. Finally, we describe some program packages that we have developed which make it easier to perform practical frequency analysis of series using this theory.

  3. Substorms observations over Apatity during geomagnetic storms in the period 2012 - 2016

    NASA Astrophysics Data System (ADS)

    Guineva, Veneta; Werner, Rolf; Despirak, Irina; Kozelov, Boris

    2016-07-01

    In this work we studied substorms, generated during enhanced geomagnetic activity in the period 2012 - 2016. Observations of the Multiscale Aurora Imaging Network (MAIN) in Apatity have been used. Solar wind and interplanetary magnetic field parameters were judged by the 1-min sampled OMNI data base. Substorm onset and further development were verified by the 10-s sampled data of IMAGE magnetometers and by data of the all-sky camera at Apatity. Subject of the study were substorms occurred during geomagnetic storms. The so-called "St. Patrick's day 2015 event" (17-21 March 2015), the events on 17-18 March 2013 and 7-17 March 2012 (a chain of events generated four consecutive storms) which were among the events of strongest geomagnetic activity during the current solar cycle 24, were part of the storms under consideration. The behavior of the substorms developed during different phases of the geomagnetic storms was discussed.

  4. Quantifying uncertainties in location and source mechanism for Long-Period events at Mt Etna, Italy.

    NASA Astrophysics Data System (ADS)

    Cauchie, Léna; Saccorotti, Gilberto; Bean, Christopher

    2014-05-01

    The manifestation of Long-Period events is documented at many volcanoes worldwide. However the mechanism at their origin is still object of discussion. Models proposed so far involve (i) the resonance of fluid-filled cracks or conduits that are triggered by fluid instabilities or the brittle failure of high viscous magmas and (ii) the slow-rupture earthquakes in the shallow portion of volcanic edifices. Since LP activity usually precedes and accompanies volcanic eruption, the understanding of these sources is important in terms of hazard assessment and eruption early warning. The work is thus primarily aimed at the assessment of the uncertainties in the determination of LP source properties as a consequence of poor knowledge of the velocity structure and location errors. We used data from temporary networks deployed on Mt Etna in 2005. During August, 2005, about 13000 LP events were detected through a STA/LTA approach, and were classified into two families on the basis of waveform similarity. For each family of events, we located the source using three different approaches: (1) a single-station-location method based on the back-propagation of the polarization vector estimated from covariance analysis of three-component signals; (2) multi-channel analysis of data recorded by two seismic arrays; (3) relative locations based on inversion of differential times obtained through cross-correlation of similar waveforms. For all these three different methods, the solutions are very sensitive to the chosen velocity model. We thus iterated the location procedure for different medium properties; the preferred velocity is that for which the results obtained with the three different methods are consistent each other. For each family, we then defined a volume of possible source location and performed a full-waveform, moment tensor (MT) inversion for the entire catalog of events. In this manner, we obtained a MT solution for each grid node of the investigated volume. The MT

  5. Current reduction in a pseudo-breakup event: THEMIS observations

    NASA Astrophysics Data System (ADS)

    Yao, Z. H.; Pu, Z. Y.; Owen, C. J.; Fu, S. Y.; Chu, X. N.; Liu, J.; Angelopoulos, V.; Rae, I. J.; Yue, C.; Zhou, X.-Z.; Zong, Q.-G.; Cao, X.; Shi, Q. Q.; Forsyth, C.; Du, A. M.

    2014-10-01

    Pseudo-breakup events are thought to be generated by the same physical processes as substorms. This paper reports on the cross-tail current reduction in an isolated pseudo-breakup observed by three of the THEMIS probes (THEMIS A (THA), THEMIS D (THD), and THEMIS E (THE)) on 22 March 2010. During this pseudo-breakup, several localized auroral intensifications were seen by ground-based observatories. Using the unique spatial configuration of the three THEMIS probes, we have estimated the inertial and diamagnetic currents in the near-Earth plasma sheet associated with flow braking and diversion. We found the diamagnetic current to be the major contributor to the current reduction in this pseudo-breakup event. During flow braking, the plasma pressure was reinforced, and a weak electrojet and an auroral intensification appeared. After flow braking/diversion, the electrojet was enhanced, and a new auroral intensification was seen. The peak current intensity of the electrojet estimated from ground-based magnetometers, ~0.7 × 105 A, was about 1 order of magnitude lower than that in a typical substorm. We suggest that this pseudo-breakup event involved two dynamical processes: a current-reduction associated with plasma compression ahead of the earthward flow and a current-disruption related to the flow braking/diversion. Both processes are closely connected to the fundamental interaction between fast flows, the near-Earth ambient plasma, and the magnetic field.

  6. ISO spectroscopic observations of short-period comets

    NASA Astrophysics Data System (ADS)

    Crovisier, J.; Encrenaz, Th.; Lellouch, E.; Bockelée-Morvan, D.; Altieri, B.; Leech, K.; Salama, A.; Griffin, M. J.; de Graauw, Th.; van Dishoeck, E. F.; Knacke, R.; Brooke, T. Y.

    1999-03-01

    Two Infrared Space Observatory programmes (guaranteed time and open time) were devoted to high-resolution spectroscopic observations of short-period comets. 22P/Kopff was observed on October-December 1996 with SWS and LWS. Due to the weakness of the object, only the ν3 ro-vibrational lines of water were detected, with SWS. Comet 103P/Hartley 2 was observed close to its perihelion (at 1.04 AU from Sun and 0.82 AU from Earth) on January 1998 with SWS, LWS and CAM. The bands of H2O and CO2 at 2.7 and 4.3 μm are detected, with [CO2]/[H2O] = 10 %. The 2.7 μm band of H2O is observed with a high signal-to-noise ratio with SWS, which permits to evaluate the rotational temperature of water to 16-20 K and its ortho-to-para ratio to ~ 2.7, corresponding to a spin temperature of ~ 35 K. The 5-17 μm spectrum of comet Hartley 2 observed with CAM-CVF shows the 9-12 μm signature of silicates. Silicate emission around 10 μm is present at a level of about 20 % of the continuum, with a peak at 11.3 μm indicative of crystalline silicates. This is the first time crystalline silicates are found in a short-period comet. The ISO observations of the Jupiter-family comet P/Hartley 2, presumably originating from the Edgeworth-Kuiper belt, are compared to those of comet Hale-Bopp which came from the Oort cloud.

  7. 313 new asteroid rotation periods from Palomar Transient Factory observations

    SciTech Connect

    Chang, Chan-Kao; Ip, Wing-Huen; Lin, Hsing-Wen; Cheng, Yu-Chi; Ngeow, Chow-Choong; Yang, Ting-Chang; Waszczak, Adam; Kulkarni, Shrinivas R.; Levitan, David; Sesar, Branimir; Prince, Thomas A.; Laher, Russ; Surace, Jason

    2014-06-10

    A new asteroid rotation period survey has been carried out by using the Palomar Transient Factory (PTF). Twelve consecutive PTF fields, which covered an area of 87 deg{sup 2} in the ecliptic plane, were observed in the R band with a cadence of ∼20 minutes during 2013 February 15-18. We detected 2500 known asteroids with a diameter range of 0.5 km ≤D ≤ 200 km. Of these, 313 objects had highly reliable rotation periods and exhibited the 'spin barrier' at ∼2 hr. In contrast to the flat spin-rate distribution of the asteroids with 3 km ≤D ≤ 15 km shown by Pravec et al., our results deviated somewhat from a Maxwellian distribution and showed a decrease at the spin rate greater than 5 rev day{sup –1}. One superfast rotator candidate and two possible binary asteroids were also found in this work.

  8. Wave and plasma observations during a compressional Pc 5 wave event August 10, 1982

    NASA Technical Reports Server (NTRS)

    Engebretson, M. J.; Cahill, L. J., Jr.; Waite, J. H., Jr.; Gallagher, D. L.; Chandler, M. O.; Sugiura, M.

    1986-01-01

    Magnetometer and thermal plasma instruments on the polar-orbiting Dynamics Explorer 1 satellite observed a small-amplitude ultralow frequency pulsation event at the outer edge of the plasmapause near the geomagnetic equator in the midafternoon sector on August 10, 1982, during the recovery phase of a magnetic storm. Transverse pulsations of 30-50 s period were observed throughout the event, and a 270-s period, purely compressional Pc 5 pulsation with several shifts in phase occurred within + or - 5 deg of the geomagnetic equator. Electric fields and the motion of thermal ions appeared to be in quadrature with pulsations in magnetic field magnitude throughout the event. This suggests that the net Poynting flux for the compressional waves was zero, consistent with their being standing waves. Large fluxes of trapped 90 deg pitch angle 10-eV protons, also symmetric about the geomagnetic equator, were observed in conjunction with the waves. These may serve as a source of free energy for the pulsations. These observations lend support to recent studies suggesting that many dayside compressional wave events are related to localized field line resonance near plasmapauselike boundaries, but also include features that cannot be explained by existing theories.

  9. Substorms observations during two geomagnetically active periods in March 2012 and March 2015

    NASA Astrophysics Data System (ADS)

    Guineva, V.; Despirak, I.; Kozelov, B.

    2016-05-01

    In this work two events of strong geomagnetic activity were examined: the period 7-17 March 2012, which is one of the most disturbed periods during the ascending phase of Solar Cycle 24, and the severe geomagnetic storm on 17-20 March 2015. During the first period four consecutive magnetic storms occurred on 7, 9, 12, and 15 March. These storms were caused by Sheath, MC and HSS, and the detailed scenarios for the storms were different. The second event is a storm of fourth level with Kp = 8, the strongest one during the last four years, the so-called "St. Patrick's Day 2015 Event". A geomagnetic storm of such intensity was observed in September 2011. Our analysis was based on the 10-s sampled IMAGE magnetometers data, the 1-min sampled OMNI solar wind and interplanetary magnetic field (IMF) data and observations of the Multiscale Aurora Imaging Network (MAIN) in Apatity. The particularities in the behaviours of substorms connected with different storms during these two interesting strongly disturbed periods are discussed.

  10. Direct observation of ice nucleation events on individual atmospheric particles

    SciTech Connect

    Wang, Bingbing; Knopf, Daniel A.; China, Swarup; Arey, Bruce W.; Harder, Tristan H.; Gilles, Mary K.; Laskin, Alexander

    2016-01-01

    Heterogeneous ice nucleation is a physical chemistry process of critical relevance to a range of topics in the fundamental and the applied sciences and technologies. Heterogeneous ice nucleation remains insufficiently understood. This is in part due to the lack of experimental methods capable of in situ visualization of ice formation over nucleating substrates with microscopically characterized morphology and composition. We present development, validation and first applications of a novel electron microscopy platform allowing observation of individual ice nucleation events at temperature and relative humidity (RH) relevant for ice formation in a broad range of environmental and applied technology processes. The approach utilizes a custom-built ice nucleation cell, interfaced with an Environmental Scanning Electron Microscope (IN-ESEM system). The IN-ESEM system allows dynamic observations of individual ice formation events over particles of atmospheric relevance and determination of the ice nucleation mechanisms. Additional IN-ESEM experiments allow examination of the location of ice formation on the surface of individual particles and micro-spectroscopy analysis of the ice nucleating particles (INPs). This includes elemental composition detected by the energy dispersed analysis of X-rays (EDX), speciation of the organic content in particles using scanning transmission X-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS), and Helium ion microscopy (HeIM). The capabilities of the IN-ESEM experimental platform are demonstrated first on laboratory standards and then by chemical imaging of INPs using a complex sample of ambient particles.

  11. OMI Tropospheric NO2 from Lightning in Observed Convective Events

    NASA Technical Reports Server (NTRS)

    Pickering, Kenneth; Bucsela, Eric; Gleason, James; Levelt, Pieternel

    2007-01-01

    Lightning is responsible for an estimated 10-20% of NO(x) emissions in the troposphere. In this study, we present evidence of lightning-generated NO2 (LNO2) using data from the Ozone Monitoring Instrument (OMI), which has observed tropospheric NO2 since its launch in 2004. Although LNO2 has been also reported in previous satellite studies from the Global Ozone Monitoring Experiment (GOME) and SCIAMACHY, OMI is better suited for such measurements by virtue of its higher resolution and daily global coverage. The LNO2 signal is clearly seen in OMI data on two days over and downwind of convective systems in the US Midwest in 2006. We also present an analysis of OMI data over northern Australia during the SCOUT-O3/ACTIVE field campaigns in November and December 2005. Both single- and multi-day averages are presented to examine possible LNO2 signals from individual diurnally recurrent convective events. In these events we compare the OMI signals with aircraft observations from the storm anvils.

  12. Characteristics of extreme rainfall events in northwestern Peru during the 1982-1983 El Nino period

    NASA Technical Reports Server (NTRS)

    Goldberg, R. A.; Tisnado, G. M.; Scofield, R. A.

    1987-01-01

    Histograms and contour maps describing the daily rainfall characteristics of a northwestern Peru area most severely affected by the 1982-1983 El Nino event were prepared from daily rainfall data obtained from 66 stations in this area during the El Nino event, and during the same 8-month intervals for the two years preceding and following the event. These data were analyzed, in conjunction with the anlysis of visible and IR satellite images, for cloud characteristics and structure. The results present a comparison of the rainfall characteristics as a function of elevation, geographic location, and the time of year for the El Nino and non-El Nino periods.

  13. Calculation of 239Pu fission observables in an event-by-event simulation

    SciTech Connect

    Vogt, R; Randrup, J; Pruet, J; Younes, W

    2010-03-31

    The increased interest in more exclusive fission observables has demanded more detailed models. We describe a new computational model, FREYA, that aims to meet this need by producing large samples of complete fission events from which any observable of interest can then be extracted consistently, including any interesting correlations. The various model assumptions are described and the potential utility of the model is illustrated. As a concrete example, we use formal statistical methods, experimental data on neutron production in neutron-induced fission of {sup 239}Pu, along with FREYA, to develop quantitative insights into the relation between reaction observables and detailed microscopic aspects of fission. Current measurements of the mean number of prompt neutrons emitted in fission taken together with less accurate current measurements for the prompt post-fission neutron energy spectrum, up to the threshold for multi-chance fission, place remarkably fine constraints on microscopic theories.

  14. Asynchronous Periodic Edge-Event Triggered Control for Double-Integrator Networks With Communication Time Delays.

    PubMed

    Duan, Gaopeng; Xiao, Feng; Wang, Long

    2017-01-23

    This paper focuses on the average consensus of double-integrator networked systems based on the asynchronous periodic edge-event triggered control. The asynchronous property lies in the edge event-detecting procedure. For different edges, their event detections are performed at different times and the corresponding events occur independently of each other. When an event is activated, the two adjacent agents connected by the corresponding link sample their relative state information and update their controllers. The application of incidence matrix facilitates the transformation of control objects from the agent-based to the edge-based. Practically, due to the constraints of network bandwidth and communication distance, agents usually cannot receive the instantaneous information of some others, which has an impact on the system performance. Hence, it is necessary to investigate the presence of communication time delays. For double-integrator multiagent systems with and without communication time delays, the average state consensus can be asynchronously achieved by designing appropriate parameters under the proposed event-detecting rules. The presented results specify the relationship among the maximum allowable time delays, interaction topologies, and event-detecting periods. Furthermore, the proposed protocols have the advantages of reduced communication costs and controller-updating costs. Simulation examples are given to illustrate the proposed theoretical results.

  15. W-band spaceborne radar observations of atmospheric river events

    NASA Astrophysics Data System (ADS)

    Matrosov, S. Y.

    2010-12-01

    While the main objective of the world first W-band radar aboard the CloudSat satellite is to provide vertically resolved information on clouds, it proved to be a valuable tool for observing precipitation. The CloudSat radar is generally able to resolve precipitating cloud systems in their vertical entirety. Although measurements from the liquid hydrometer layer containing rainfall are strongly attenuated, special retrieval approaches can be used to estimate rainfall parameters. These approaches are based on vertical gradients of observed radar reflectivity factor rather than on absolute estimates of reflectivity. Concurrent independent estimations of ice cloud parameters in the same vertical column allow characterization of precipitating systems and provide information on coupling between clouds and rainfall they produce. The potential of CloudSat for observations atmospheric river events affecting the West Coast of North America is evaluated. It is shown that spaceborne radar measurements can provide high resolution information on the height of the freezing level thus separating areas of rainfall and snowfall. CloudSat precipitation rate estimates complement information from the surface-based radars. Observations of atmospheric rivers at different locations above the ocean and during landfall help to understand evolutions of atmospheric rivers and their structures.

  16. Event-based internet biosurveillance: relation to epidemiological observation

    PubMed Central

    2012-01-01

    Background The World Health Organization (WHO) collects and publishes surveillance data and statistics for select diseases, but traditional methods of gathering such data are time and labor intensive. Event-based biosurveillance, which utilizes a variety of Internet sources, complements traditional surveillance. In this study we assess the reliability of Internet biosurveillance and evaluate disease-specific alert criteria against epidemiological data. Methods We reviewed and compared WHO epidemiological data and Argus biosurveillance system data for pandemic (H1N1) 2009 (April 2009 – January 2010) from 8 regions and 122 countries to: identify reliable alert criteria among 15 Argus-defined categories; determine the degree of data correlation for disease progression; and assess timeliness of Internet information. Results Argus generated a total of 1,580 unique alerts; 5 alert categories generated statistically significant (p < 0.05) correlations with WHO case count data; the sum of these 5 categories was highly correlated with WHO case data (r = 0.81, p < 0.0001), with expected differences observed among the 8 regions. Argus reported first confirmed cases on the same day as WHO for 21 of the first 64 countries reporting cases, and 1 to 16 days (average 1.5 days) ahead of WHO for 42 of those countries. Conclusion Confirmed pandemic (H1N1) 2009 cases collected by Argus and WHO methods returned consistent results and confirmed the reliability and timeliness of Internet information. Disease-specific alert criteria provide situational awareness and may serve as proxy indicators to event progression and escalation in lieu of traditional surveillance data; alerts may identify early-warning indicators to another pandemic, preparing the public health community for disease events. PMID:22709988

  17. Increased thermohaline stratification as a possible cause for an ocean anoxic event in the Cretaceous period.

    PubMed

    Erbacher, J; Huber, B T; Norris, R D; Markey, M

    2001-01-18

    Ocean anoxic events were periods of high carbon burial that led to drawdown of atmospheric carbon dioxide, lowering of bottom-water oxygen concentrations and, in many cases, significant biological extinction. Most ocean anoxic events are thought to be caused by high productivity and export of carbon from surface waters which is then preserved in organic-rich sediments, known as black shales. But the factors that triggered some of these events remain uncertain. Here we present stable isotope data from a mid-Cretaceous ocean anoxic event that occurred 112 Myr ago, and that point to increased thermohaline stratification as the probable cause. Ocean anoxic event 1b is associated with an increase in surface-water temperatures and runoff that led to decreased bottom-water formation and elevated carbon burial in the restricted basins of the western Tethys and North Atlantic. This event is in many ways similar to that which led to the more recent Plio-Pleistocene Mediterranean sapropels, but the greater geographical extent and longer duration (approximately 46 kyr) of ocean anoxic event 1b suggest that processes leading to such ocean anoxic events in the North Atlantic and western Tethys were able to act over a much larger region, and sequester far more carbon, than any of the Quaternary sapropels.

  18. Overview of the first HyMeX special observation period over Croatia

    NASA Astrophysics Data System (ADS)

    Ivančan-Picek, Branka; Tudor, Martina; Horvath, Kristian; Stanešić, Antonio; Ivatek-Šahdan, Stjepan

    2016-12-01

    The HYdrological cycle in the Mediterranean EXperiment (HyMeX) is intended to improve the capabilities of predicting high-impact weather events. Within its framework, the aim of the first special observation period (SOP1), 5 September to 6 November 2012, was to study heavy precipitation events and flash floods. Here, we present high-impact weather events over Croatia that occurred during SOP1. Particular attention is given to eight intense observation periods (IOPs), during which high precipitation occurred over the eastern Adriatic and Dinaric Alps. During the entire SOP1, the operational model forecasts generally well represented medium intensity precipitation, but heavy precipitation was frequently underestimated by the ALADIN model at an 8 km grid spacing and was overestimated at a higher resolution (2 km grid spacing). During IOP2, intensive rainfall occurred over a wider area around the city of Rijeka in the northern Adriatic. The short-range maximum rainfall totals were the largest ever recorded at the Rijeka station since the beginning of measurements in 1958. The rainfall amounts measured in intervals of 20, 30 and 40 min were exceptional, with return periods that exceeded a thousand, a few hundred and one hundred years, respectively. The operational precipitation forecast using the ALADIN model at an 8 km grid spacing provided guidance regarding the event but underestimated the rainfall intensity. An evaluation of numerical sensitivity experiments suggested that the forecast was slightly enhanced by improving the initial conditions through variational data assimilation. The operational non-hydrostatic run at a 2 km grid spacing using a configuration with the ALARO physics package further improved the forecast. This article highlights the need for an intensive observation period in the future over the Adriatic region to validate the simulated mechanisms and improve numerical weather predictions via data assimilation and model improvements in descriptions

  19. Upstream gyrating ion events: Cluster observations and simulations

    SciTech Connect

    Sauer, K.; Fraenz, M.; Dubinin, E.; Korth, A.; Mazelle, C.; Reme, H.; Dandouras, I.

    2005-08-01

    Localized events of low-frequency quasi-monochromatic waves in the 30s range observed by Cluster in the upstream region of Earth are analyzed. They are associated with a gyro-motion of the two ion populations consisting of the incoming solar wind protons and the back-streaming ions from the shock. A coordinate system is chosen in which one axis is parallel to the ambient magnetic field B0 and the other one is in the vswxB0 direction. The variation of the plasma parameters is compared with the result of two-fluid Hall-MHD simulations using different beam densities and velocities. Keeping a fixed (relative) beam density (e.g. {alpha}=0.005), non-stationary 'shock-like' structures are generated if the beam velocity exceeds a certain threshold of about ten times the Alfven velocity. Below the threshold, the localized events represent stationary, nonlinear waves (oscillitons) in a beam-plasma system in which the Reynold's stresses of the plasma and beam ions are balanced by the magnetic field stress.

  20. Solar particle events observed at Mars: dosimetry measurements and model calculations

    NASA Astrophysics Data System (ADS)

    Cleghorn, T.; Saganti, P.; Zeitlin, C.; Cucinotta, F.

    The first solar particle events from a Martian orbit are observed with the MARIE (Martian Radiation Environment Experiment) on the 2001 Mars Odyssey space -craft that is currently in orbit and collecting the mapping data of the red planet. These solar particle events observed at Mars during March and April 2002, are correlated with the GOES-8 and ACE satellite data from the same time period at Earth orbits. Dosimetry measurements for the Mars orbit from the period of March 13t h through April 29t h . Particle count rate and the corresponding dose rate enhancements were observed on March 16t h through 20t h and on April 22n d corresponding to solar particle events that were observed at Earth orbit on March 16t h through 21s t and beginning on April 21s t respectively. The model calculations with the HZETRN (High Z=atomic number and high Energy Transport) code estimated the background GCR (Galactic Cosmic Rays) dose rates. The dose rates observed by the MARIE instrument are within 10% of the model calculations. Dosimetry measurements and model calculation will be presented.

  1. Evolution of the December 14, 1989 precursory long-period event swarm at Redoubt volcano, Alaska

    USGS Publications Warehouse

    Stephens, C.D.; Chouet, B.A.

    2001-01-01

    The intermittency pattern and evolution in waveforms of long-period (LP) seismic events during the intense, 23-h swarm that preceded the December 14, 1989 eruption of Redoubt volcano are investigated. Utilizing cross correlation to exploit the high degree of similarity among waveforms, a substantially more complete event catalog is generated than was available from near realtime detection based on short-term/long-term amplitude ratios, which was saturated by the high rate of activity. The temporal magnitude distribution of the predominant LP events is found to have an unusual banded structure in which the average magnitude of each band slowly increases and then decreases through time. A bifurcation that appears in the uppermost band shortly after the peak in magnitudes is characterized by a quasi-periodicity in intermittency and magnitude that is reminiscent of one of the classic routes to chaotic behavior in some non-linear systems. The waveforms of the predominant events evolve slowly but unsteadily through time. These gradual changes appear to result from variations in the relative amplitudes of spectral peaks that remain stable in frequency, which suggests that they are due to differential excitation of a single, resonant source. Two other previously unrecognized, repetitive waveforms are also identified, but the signals from these secondary events are not clearly recorded at distances beyond the closest station. Similarities among the spectra of the predominant and secondary events suggest that the signals from these events also could represent different modes of exciting the same source. Significant changes in the rates and the sizes of the largest of these secondary events appear to coincide with the peak in the size distribution of the predominant LPs. At least some of the non-repetitive LP waveforms in the swarm appear to be the result of the superposition of signals from the rapid repetition of predominant LP source, thus placing a constraint on the

  2. Observations of Quasi-Periodic Whistler Mode Waves by the Van Allen Probes

    NASA Astrophysics Data System (ADS)

    Hospodarsky, George; Wilkinson, Darrelle; Kurth, William; Kletzing, Craig; Santolik, Ondrej

    2016-10-01

    Observed in Earth's inner magnetosphere, quasi-periodic whistler mode emissions (QP) are electromagnetic waves in the frequency range from a few hundred Hz to a few kHz that exhibit a periodic modulation (typically a few minutes) of their wave intensity. These waves were first detected at high latitude ground stations, but more recently have been observed by a number of spacecraft, including the twin Van Allen Probes. The Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument simultaneously measures the vector wave magnetic field and electric field, allowing wave propagation parameters, such as wave normal angle and Poynting vector, to be obtained. Almost four years of Van Allen Probes data have been examined and a statistical survey of the occurrence and properties of the QP emissions has been performed. The QP emissions were found to have periods ranging from 1 to 16 minutes with events lasting from less than 1 hour up to 6 hours. Some events were detected on successive orbits and a number of events were simultaneously detected by both spacecraft, even during large spacecraft separations, providing an opportunity to investigate the source and propagation properties of these waves.

  3. The first massive astronomical observation event in Mexico City

    NASA Astrophysics Data System (ADS)

    Espinosa, Mariana; Hernandez, Xavier

    2011-06-01

    On the night of the 20th of February 2008 there was a total eclipse of the moon visible from Mexico City, with a total duration from 19:42 hrs to 23:09 hrs. At the Instituto de Astronomía, UNAM, we took this opportunity to organise a massive astronomical party on the central plaza of the city, the Zocalo. Over a period of about 6 hrs. we set up a huge astro-party, with free use of over 100 telescopes, where we estimate over 40,000 persons looked through an astronomical telescope at the moon and Saturn, most for the first time in their lives. Numerous stands including a children's games, an Astronomy conference room, and the free distribution of Astronomical material were organised. Here we describe some of the issues associated with the planning and implementation of the event. Coordination issues were complex, involving interaction with divers and numerous authorities, city, national, police, traffic, medical assistance in readiness, aide from other universities, and amateur astronomical societies, which supplied most of the telescopes. An extensive publicity campaign was launched with several weeks of anticipation, and although we had no way of estimating the public response, we were ready with over 800 volunteers at the Zócalo on the 20th of February. The public response was massive and overwhelmingly positive, thousands swarmed the square in a completely peaceful and well organised interaction between Astronomy and society at large, over many complementary levels

  4. A novel approach to periodic event-triggered control: Design and application to the inverted pendulum.

    PubMed

    Aranda-Escolástico, Ernesto; Guinaldo, María; Gordillo, Francisco; Dormido, Sebastián

    2016-11-01

    In this paper, periodic event-triggered controllers are proposed for the rotary inverted pendulum. The control strategy is divided in two steps: swing-up and stabilization. In both cases, the system is sampled periodically but the control actions are only computed at certain instances of time (based on events), which are a subset of the sampling times. For the stabilization control, the asymptotic stability is guaranteed applying the Lyapunov-Razumikhin theorem for systems with delays. This result is applicable to general linear systems and not only to the inverted pendulum. For the swing-up control, a trigger function is provided from the derivative of the Lyapunov function for the swing-up control law. Experimental results show a significant improvement with respect to periodic control in the number of control actions.

  5. Time period and lesbian identity events: a comparison of Norwegian lesbians across 1986 and 2005.

    PubMed

    Giertsen, Merethe; Anderssen, Norman

    2007-11-01

    The purpose of the present work was to investigate the assumption that the lives of lesbians are easier today. When exploring the hypothesis that identity events (e.g., coming out to parents) among lesbian women have changed over time and happen earlier in life today, we expected to find several time period effects. Two national samples obtained through mailed questionnaires were compared, 1986 (n = 123) and 2005 (n = 236), age range 20-49. Time period effects were found, including informants reporting identifying as lesbian earlier in life. Time period effects, however, were not found regarding relational identity events such as informing others about one's identity status. The findings did not reveal any conclusive evidence that it is easier to establish a lesbian lifestyle today.

  6. The variations of long time period slow slip events along the Ryukyu subduction zone

    NASA Astrophysics Data System (ADS)

    Tu, Y. T.; Heki, K.

    2014-12-01

    Slow slip events (SSEs) are a type of slow earthquakes that can be observed with Global Positioning System (GPS) networks in the world. Those events are detected on intensely coupled plate boundaries such as Cascadia subduction zone (Dragert et al., 2001), western North America, Mexico (Kostoglodov et al., 2003), Alaska (Ohta et al., 2007) and Tokai and Boso areas (Ozawa et al., 2002, 2003), central Japan and are considered to have relations to large subduction thrust earthquakes. However, in southwestern Ryukyu trench where most of researchers believe that it should be a decoupled plate boundary, SSEs recur regularly and are located at a patch that is as deep as 20 to 40 km (Heki and Kataoka, 2008). For comprehending the characteristics and time variations of SSEs in this area, the GEONET GPS data of 16 years are used in this study. During 1997 to 2014, more than thirty SSEs are identified near Hateruma Island, Ryukyu. The average recurrence interval is calculated to be 6.3 months and release seismic moment is Mw 6.6 on average. However, the values of recurrence interval are not invariable. From 1997 to 2002, interval period of SSEs is 7.5 months, but during 2002 to 2008, the interval period decreases suddenly to 5.5 months. After 2008, the value restores to 7.2 months again. Furthermore, the slip amount of SSEs in this area varies with time. From 1997 to 2002, the slip is 9.5 cm/year; and during 2002 to 2008, the value slightly increases to 10.5 cm/year. However, in 2008 to 2013, the slip drops to 6.6 cm/year, but accord to the trend of cumulative slip, the slip value would increase in 2014. Considering these data, we find the slip values increase conspicuously in 2002 and 2013. Coincidentally, one Mw 7.1 thrust earthquake occurred in 2002 and earthquake swarm activity started in the Okinawa trough approximately 50km north of the SSE patch. In 2013, another earthquake swarm activity occurred in nearly the same area as the 2002 activity. This suggests that the

  7. Variability in eruption style and associated very long period events at Fuego volcano, Guatemala

    NASA Astrophysics Data System (ADS)

    Waite, Gregory P.; Nadeau, Patricia A.; Lyons, John J.

    2013-04-01

    Repeated short-term deployments of seismic, infrasound, video, and gas-emission instruments at Fuego volcano, Guatemala have revealed three types of very long period (VLP) events associated with conduit sealing, pressure accumulation, and release. In 2008, ash-rich explosions issued from a vent on the western flank and produced one type of VLP (Type 1). Impulsive, bomb-rich explosions from the summit vent in 2009 produced a shorter period VLP (Type 2), but also generated ash release. Type 3 VLP events occurred during ash-free exhalations from the summit in 2008 and had waveform shapes similar to Type 2 events. Weak infrasound records for Type 1 explosions compared to Type 2 suggest lower pressures and higher magma porosity for Type 1. Type 3 events correlate with spikes in SO2 emission rate and are driven by partial sealing and rapid release of ash-free gas at the summit vent. Variations in the VLP period may provide a new tool for monitoring conditions within the conduit.

  8. Nucleation events at a coastal city during the warm period: Kerbside versus urban background measurements

    NASA Astrophysics Data System (ADS)

    Siakavaras, D.; Samara, C.; Petrakakis, M.; Biskos, G.

    2016-09-01

    Number size distributions of atmospheric aerosol particles were simultaneously measured at a kerbside and an urban background site in the city of Thessaloniki, Greece, from June to October 2009. New particle formation events were observed ca. 27% of the days at the urban kerbside site and 29% of the days at the urban background site. In almost all the cases the events started between 10:00 and 12:00, and continued for several hours. The total number concentration (TNC) of the particles having diameters from 10 to ca. 500 nm during the events increased from 1.4 × 104 to 6.5 × 104 #/cm3 at the urban kerbside site, and from 0.2 × 104 to 2.4 × 104 #/cm3 at the urban background site. At the urban kerbside site, 9% of the days exhibited class I events (i.e., events followed by a clear growth of the newly formed particles), 10% class II (i.e., events during which the concentration of nucleation mode particles were high but their growth was not continuous), 67% were characterised as non-event days, and 14% of the days exhibited no clear particle formation pattern (undefined). At the urban background site, 15% of the days were classified as class I, 5% as class II, 75% of the days showed no nucleation, whereas only 5% of the days were undefined. While the fraction of event days (both class I and class II) at both sites was similar (ca. 20%), the higher fraction of class I events observed at Eptapyrgio can be attributed to the cleaner environment of the urban background site that allows better identification of the particle concentration increase. The nucleation bursts show a similar pattern at both sites, with the newly formed particles reaching a final size of ca. 80-100 nm. A distinct difference between the two stations was that the smallest particles observed during the new-particle formation events had a diameter of ca. 10 nm (i.e., the smallest particles we could observe) at the kerbside site and ca. 20 nm at the urban background site. This is an indication that

  9. Periodicity in the spatial-temporal earthquake distributions for the Pacific region: observation and modeling.

    NASA Astrophysics Data System (ADS)

    Sasorova, Elena; Levin, Boris

    2014-05-01

    In the course of the last century a cyclic increasing and decreasing of the Earth's seismic activity (SA) was marked. The variations of the SA for the events with M>=7.0 from 1900 up to date were under study. The two subsets of the worldwide NEIC (USGS) catalog were used: USGS/NEIC from 1973 to 2012 and catalog of the significant worldwide earthquakes (2150 B.C. - 1994 A.D.), compiled by USGS/NEIC from the NOAA agency. The preliminary standardization of magnitudes and elimination of aftershocks from list of events was performed. The entire period of observations was subdivided into 5-year intervals. The temporal distributions of the earthquake (EQ) density and released energy density were calculated separately for the Southern hemisphere (SH), and for the Northern hemisphere (NH) and for eighteen latitudinal belts: 90°-80°N, 80°-70°N, 70°-60°N, 60°-50°N and so on (the size of each belt is equal to 10°). The periods of the SA was compared for different latitudinal belts of the Earth. The peaks and decays of the seismicity do not coincide in time for different latitudinal belts and especially for the belts located in NH and SH. The peaks and decays of the SA for the events (with M>=8) were marked in the temporal distributions of the EQ for all studied latitudinal belts. The two-dimension distributions (over latitudes and over time) of the EQ density and released energy density highlighted that the periods of amplification of the SA are equal to 30-35 years approximately. Next, we check the existence of a non-random component in the EQ occurrence between the NH and the SH. All events were related to the time axis according to their origin time. We take into consideration the set of the EQs in the studied catalog as the sequence of events if each event may have only one of two possible outcome (occurrence in the NH or in the SH). A nonparametric run test was used for testing of hypothesis about an existence the nonrandom component in the examined sequence of

  10. November 2004 space weather events: Real-time observations and forecasts

    NASA Astrophysics Data System (ADS)

    Trichtchenko, L.; Zhukov, A.; van der Linden, R.; Stankov, S. M.; Jakowski, N.; StanisłAwska, I.; Juchnikowski, G.; Wilkinson, P.; Patterson, G.; Thomson, A. W. P.

    2007-06-01

    Space weather events with their solar origin and their distribution through the heliosphere affect the whole magnetosphere-ionosphere-Earth system. Their real-time monitoring and forecasting are important for science and technology. Here we discuss one of the largest space weather events of Solar Cycle 23, in November 2004, which was also one of the most difficult periods to forecast. Nine halo coronal mass ejections (CMEs), interacting on their way through the interplanetary medium and forming two geoeffective interplanetary structures, exemplify the complexity of the event. Real-time and quasi-real-time observations of the ground geomagnetic field show rapid and extensive expansion of the auroral oval to 55° in geomagnetic latitude accompanied by great variability of the ionosphere. Geomagnetically induced currents (GICs) seen in ground networks, such as power grids and pipelines, were significant during the event, although no problems were reported. Forecasts of the CME propagation, global and local ground geomagnetic activity, and ionospheric parameters, issued by several regional warning centers, revealed certain deficiencies in predictions of the interplanetary characteristics of the CME, size of the geomagnetic disturbances, and complexity of the ionospheric variations produced by this event. This paper is a collective report based on the materials presented at the splinter session on November 2004 events during the first European Space Weather Week.

  11. A mesoscale gravity wave event observed during CCOPE. III - Wave environment and probable source mechanisms

    NASA Technical Reports Server (NTRS)

    Koch, Steven E.; Dorian, Paul B.

    1988-01-01

    The multiscale environment of gravity wave events and the probable mechanisms of their origin are examined on the basis of observations taken during the Cooperative Convective Precipitation Experiment in extreme eastern Montana, during the period from 1200 UTC July 11, 1981, to 0500 UTC July 12. During this time, two distinct gravity wave episodes were diagnosed. The results of the analysis of the evolving structures in the subsynoptic-scale and mesoscale environments indicate that the observed mesoscale gravity waves were generated by geostrophic adjustment processes, with additional energy supplied through interaction with the critical level; their coherence was maintained through a ducting mechanism.

  12. Transition-zone observations of rapid flare events as observed by OSO-8

    NASA Technical Reports Server (NTRS)

    Lites, B. W.

    1981-01-01

    The rapid dissipation of flare energy has been observed in the transition-zone line of C IV at 1548.2 A using the University of Colorado spectrometer aboard OSO-8. Impulsive brightenings have been resolved with characteristic rise times as low as 3.5s. One event is analyzed in detail, and it is inferred that the electron density is greater than 2 x 10 to the 11th/cu cm at a temperature of 60,000 K, and that the flare energy is deposited at a rate of 2 ergs/cu cm per sec or greater. The temporal behavior of the intensity at the center of the C IV line is consistent with a nonequilibrium ionization of C III through C V. If this event is a result of the multiple tearing mode instability as the primary energy release mechanism, then the observations indicate a preflare magnetic field of about 175 G.

  13. Constraints on Cumulus Parameterization from Simulations of Observed MJO Events

    NASA Technical Reports Server (NTRS)

    Del Genio, Anthony; Wu, Jingbo; Wolf, Audrey B.; Chen, Yonghua; Yao, Mao-Sung; Kim, Daehyun

    2015-01-01

    Two recent activities offer an opportunity to test general circulation model (GCM) convection and its interaction with large-scale dynamics for observed Madden-Julian oscillation (MJO) events. This study evaluates the sensitivity of the Goddard Institute for Space Studies (GISS) GCM to entrainment, rain evaporation, downdrafts, and cold pools. Single Column Model versions that restrict weakly entraining convection produce the most realistic dependence of convection depth on column water vapor (CWV) during the Atmospheric Radiation Measurement MJO Investigation Experiment at Gan Island. Differences among models are primarily at intermediate CWV where the transition from shallow to deeper convection occurs. GCM 20-day hindcasts during the Year of Tropical Convection that best capture the shallow–deep transition also produce strong MJOs, with significant predictability compared to Tropical Rainfall Measuring Mission data. The dry anomaly east of the disturbance on hindcast day 1 is a good predictor of MJO onset and evolution. Initial CWV there is near the shallow–deep transition point, implicating premature onset of deep convection as a predictor of a poor MJO simulation. Convection weakly moistens the dry region in good MJO simulations in the first week; weakening of large-scale subsidence over this time may also affect MJO onset. Longwave radiation anomalies are weakest in the worst model version, consistent with previous analyses of cloud/moisture greenhouse enhancement as the primary MJO energy source. The authors’ results suggest that both cloud-/moisture-radiative interactions and convection–moisture sensitivity are required to produce a successful MJO simulation.

  14. Continental seismic events observed by the MPL vertical DIFAR array

    SciTech Connect

    Harris, D.B.; D`Spain, G.

    1993-11-01

    The vertical DIFAR array, an underwater acoustic sensor system, deployed by the Marine Physical Laboratory (MPL) was in place over the continental shelf off of Southern California and recorded the HUNTERS TROPHY nuclear test and nearly a score of after-shocks of the Landers/Big Bear earthquakes. Data from this array raise the possibility that detection thresholds for continental events may be significantly lower for arrays over the continental shelf than for arrays in the deep ocean basins. Offshore stations could be used to fill gaps in land-based seismic networks for monitoring the NPT and a CTBT, especially for monitoring non-cooperating nations with large coastlines. This preliminary report provides an analysis of the HUNTERS TROPHY observation as well as one of the Landers aftershocks. The analysis suggests detection thresholds for vertical hydrophone arrays below mb 3.0 at ranges between 3 and 4 degrees, and below mb 4.4 out to 6 degrees. This report also describes two signal processing techniques that enhance the detection potential of short vertical arrays. These methods are deterministic null steering to suppress horizontally propagating ambient ocean noise, and matched field processing for vertically-incident acoustic fields. The latter technique is ideally suited for acoustic fields derived from incident seismic waves, and may be viewed as a {open_quotes}synthetic aperture{close_quotes} approach to increase the effective aperture of the array.

  15. Examining Periodic Solar-Wind Density Structures Observed in the SECCHI Heliospheric Imagers

    NASA Technical Reports Server (NTRS)

    Viall, Nicholeen M.; Spence, Harlan E.; Vourlidas, Angelos; Howard, Russell

    2010-01-01

    We present an analysis of small-scale, periodic, solar-wind density enhancements (length scales as small as approximately equals 1000 Mm) observed in images from the Heliospheric Imager (HI) aboard STEREO-A. We discuss their possible relationship to periodic fluctuations of the proton density that have been identified at 1 AU using in-situ plasma measurements. Specifically, Viall, Kepko, and Spence examined 11 years of in-situ solar-wind density measurements at 1 AU and demonstrated that not only turbulent structures, but also nonturbulent, periodic density structures exist in the solar wind with scale sizes of hundreds to one thousand Mm. In a subsequent paper, Viall, Spence, and Kasper analyzed the alpha-to-proton solar-wind abundance ratio measured during one such event of periodic density structures, demonstrating that the plasma behavior was highly suggestive that either temporally or spatially varying coronal source plasma created those density structures. Large periodic density structures observed at 1 AU, which were generated in the corona, can be observable in coronal and heliospheric white-light images if they possess sufficiently high density contrast. Indeed, we identify such periodic density structures as they enter the HI field of view and follow them as they advect with the solar wind through the images. The smaller, periodic density structures that we identify in the images are comparable in size to the larger structures analyzed in-situ at 1 AU, yielding further evidence that periodic density enhancements are a consequence of coronal activity as the solar wind is formed.

  16. The observed periods of AP and BP stars

    NASA Astrophysics Data System (ADS)

    Catalano, F. A.; Renson, P.

    1998-02-01

    A catalogue of all the periods up to now proposed for the variations of CP2, CP3, and CP4 stars is presented. The main identifiers (HD and HR), the proper name, the variable-star name, and the spectral type and peculiarity are given for each star as far as the coordinates at 2000.0 and the visual magnitude. The nature of the observed variations (light, spectrum, magnetic field, etc.) is presented in a codified way. The catalogue is arranged in three tables: the bulk of the data, i.e. those referring to CP2, CP3, and CP4 stars, are given in Table 1, while the data concerning He-strong stars are given in Table 2 and those for eclipsing or ellipsoidal variables are collected in Table 3. Notes are also provided at the end of each table, mainly about duplicities. The catalogue contains data on 364 CP stars and is updated to 1996, October 31. This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France.

  17. Observations of Early/Fast VLF Events on Vieques Island, Puerto Rico

    NASA Astrophysics Data System (ADS)

    Pasko, V. P.; Inan, U. S.; Wood, T. G.; Stanley, M. A.; Mathews, J. D.; George, J. J.; Fong, N. T.

    2002-12-01

    Early/Fast VLF events are registered as sudden (i.e., "fast" < 20 ms) subionospheric VLF signal changes, occurring simultaneously (i.e., "early", <20 ms) with lightning discharges [e.g., Inan et al., GRL, 20, 2355, 1993]. These events constitute evidence of the direct energetic coupling between tropospheric thunderstorms and the overlying mesospheric and lower ionospheric regions. In August-September 2001 Penn State University organized an experimental campaign in Puerto Rico to perform correlative studies of lightning and lightning-induced ionospheric effects. A set of instruments employed for these studies included Arecibo Observatory 430 MHz UHF radar, New Mexico Tech Interferometer, and a video system. As part of this campaign Stanford University deployed broadband and narrowband VLF receivers at Casa Cielo, Vieques Island, Puerto Rico (18.12 deg N, 65.50 deg W), which were operated continuously during the time period August 21- September 15, 2001. The narrowband measurements of the NAU (Aguadilla, Puerto Rico), NLK (Jim Creek, Washington) and NAA (Cutler, Maine) signals were performed every day from 1500UT to 1400UT while broadband recordings were made 1 minute out of every 5 minutes from 1630UT to 1000UT. In this talk we report observations of spectacular early/fast VLF events, which were detected on the 40.75 kHz NAU signal on multiple occasions during August 31, September 1, 2 and 13, 2001. The observed signal amplitude changes ranged from a fraction of a dB up to 19 dB, with both positive and negative field changes. The unusually large events were superposed on top of a very high degree of variability of signal amplitude, caused by the fact that the magnetic loop antenna was aligned to null the ground signal and was thus disposed to only detect the sky wave signal. Some of the observed events exhibited recovery signatures with duration on the order of several tens of seconds, while a subset of events did not exhibit clear recovery signatures, possibly

  18. Locations and focal mechanisms of deep long period events beneath Aleutian Arc volcanoes using back projection methods

    NASA Astrophysics Data System (ADS)

    Lough, A. C.; Roman, D. C.; Haney, M. M.

    2015-12-01

    Deep long period (DLP) earthquakes are commonly observed in volcanic settings such as the Aleutian Arc in Alaska. DLPs are poorly understood but are thought to be associated with movements of fluids, such as magma or hydrothermal fluids, deep in the volcanic plumbing system. These events have been recognized for several decades but few studies have gone beyond their identification and location. All long period events are more difficult to identify and locate than volcano-tectonic (VT) earthquakes because traditional detection schemes focus on high frequency (short period) energy. In addition, DLPs present analytical challenges because they tend to be emergent and so it is difficult to accurately pick the onset of arriving body waves. We now expect to find DLPs at most volcanic centers, the challenge lies in identification and location. We aim to reduce the element of human error in location by applying back projection to better constrain the depth and horizontal position of these events. Power et al. (2004) provided the first compilation of DLP activity in the Aleutian Arc. This study focuses on the reanalysis of 162 cataloged DLPs beneath 11 volcanoes in the Aleutian arc (we expect to ultimately identify and reanalyze more DLPs). We are currently adapting the approach of Haney (2014) for volcanic tremor to use back projection over a 4D grid to determine position and origin time of DLPs. This method holds great potential in that it will allow automated, high-accuracy picking of arrival times and could reduce the number of arrival time picks necessary for traditional location schemes to well constrain event origins. Back projection can also calculate a relative focal mechanism (difficult with traditional methods due to the emergent nature of DLPs) allowing the first in depth analysis of source properties. Our event catalog (spanning over 25 years and volcanoes) is one of the longest and largest and enables us to investigate spatial and temporal variation in DLPs.

  19. Determining the Return Period of Storm Surge Events in the Philippines

    NASA Astrophysics Data System (ADS)

    Santiago, Joy; Suarez, John Kenneth; Lapidez, John Phillip; Mendoza, Jerico; Caro, Carl Vincent; Tablazon, Judd; Ladiero, Christine; Mahar Francisco Lagmay, Alfredo

    2015-04-01

    The devastating damages generated by the Tropical Cyclone Haiyan storm surges in Eastern Samar, Philippines prompted the Department of Science and Technology-Project NOAH (Nationwide Operational Assessment of Hazards) to calculate the return period and storm surge exceedance probability of these events. The recurrence interval or the period of return of a storm surge event is the estimated likelihood that that event would occur again. Return periods are measured through historical data denoting the interval of recurrence in average over a period of time. The exceedance probability however, is a graphical representation that describes the probability that some various levels of loss will be exceeded over a future time period or will be surpassed over a given time. DOST-Project NOAH simulates storm surge height time series using JMA storm surge model which is a numerical model based on shallow water equations. To determine the period of recurrence of storm surges with this type of intensity, the agency intends to compute the estimation of storm surge heights generated by tropical cyclones for 2-year, 5-year, 10-year, 25-year, 50-year and 100-year return periods for the Philippine coast. The storm surge time series generated from JMA combined with WXTide simulation, a software containing archives/catalogues of world-wide astronomical tides, and 5-meter resolution DEM were used as input parameters for the inundation model, which shows probable extent of flooding at a specific storm surge return period. Flo-2D two-dimensional flood routing model, a GIS integrated software tool that facilitates the creation of the flood model grid system, was used for flood hazard model. It is a simple volume conservation model composed of processor program that facilitate graphical editing and mapping of flooding details which uses continuity equation and the dynamic wave momentum equations. The measurements of storm surge return period and probable extent of coastal flooding in the

  20. Superconducting gravimeter observation for identifying slow slip events at Ryukyu Trench

    NASA Astrophysics Data System (ADS)

    Imanishi, Y.; Nawa, K.; Tamura, Y.; Ikeda, H.; Miyaji, T.; Tanaka, Y.

    2012-12-01

    Analysis of the data from the dense GPS network of Japan (GEONET) revealed quasi-periodic occurrences of long-term slow slip events at the Ryukyu Trench (Heki and Kataoka, 2008). The recurrence period of the events is about half a year, much shorter than typically found in other regions where slow slips are known to take place. Therefore, this region provides an interesting field for investigating the nature of slow slip events. In February 2012, we started gravity observation using a superconducting gravimeter (SG) at the VERA Ishigakijima Station, National Astronomical Observatory of Japan. The Ishigakijima island is located slightly east off the presumed fault area of the slow slip events. Our purpose is to detect gravity changes associated with the slow slip events by making full use of the high resolution of the SG. Of particular interest is the possible effect of water on the slow slip events, which might be identified from gravity observations. In addition to the SG, we installed an FG5 absolute gravimeter at the Iriomotejima island, located about 10 km west of the Ishigakijima island. The SG used in this study (serial number CT36) is the one which was in operation at the Inuyama Seismological Observatory, Nagoya University for about ten years. Before moving it to Ishigakijima, we made a thorough examination of the instruments. Because we found a serious problem in transferring liquid helium because of the ice inside, we warmed up the Dewar to initialize it. This not only solved the ice problem but also resulted in a significant decrease of the heater power for the gravity sensor. As of this writing, we have about six months worth of data from the SG. The condition of the gravimeter is good except for the first month when temperature control was unstable. Because of the ground vibrations caused by the movement of the 20-m VLBI antenna (about 30 m apart from the SG), the noise level is significantly enhanced compared with other domestic SG stations. Also we

  1. "Zipper-like" periodic magnetosonic waves: Van Allen Probes, THEMIS, and magnetospheric multiscale observations

    NASA Astrophysics Data System (ADS)

    Li, J.; Bortnik, J.; Li, W.; Ma, Q.; Thorne, R. M.; Kletzing, C. A.; Kurth, W. S.; Hospodarsky, G. B.; Wygant, J.; Breneman, A.; Thaller, S.; Funsten, H. O.; Mitchell, D. G.; Manweiler, J. W.; Torbert, R. B.; Le Contel, O.; Ergun, R. E.; Lindqvist, P.-A.; Torkar, K.; Nakamura, R.; Andriopoulou, M.; Russell, C. T.

    2017-02-01

    An interesting form of "zipper-like" magnetosonic waves consisting of two bands of interleaved periodic rising-tone spectra was newly observed by the Van Allen Probes, the Time History of Events and Macroscale Interactions during Substorms (THEMIS), and the Magnetospheric Multiscale (MMS) missions. The two discrete bands are distinct in frequency and intensity; however, they maintain the same periodicity which varies in space and time, suggesting that they possibly originate from one single source intrinsically. In one event, the zipper-like magnetosonic waves exhibit the same periodicity as a constant-frequency magnetosonic wave and an electrostatic emission, but the modulation comes from neither density fluctuations nor ULF waves. A statistical survey based on 3.5 years of multisatellite observations shows that zipper-like magnetosonic waves mainly occur on the dawnside to noonside, in a frequency range between 10 fcp and fLHR. The zipper-like magnetosonic waves may provide a new clue to nonlinear excitation or modulation process, while its cause still remains to be fully understood.

  2. Observations of Single Event Failure in Power MOSFETS

    NASA Technical Reports Server (NTRS)

    Nichols, D.; McCarty, K.; Coss, J.

    1994-01-01

    The first compendium of single event test data for power MOSFETs provides failure thresholds from burnout or gate rupture for over 100 devices of eight manufacturers. Ordering the data has also provided some useful insights.

  3. Dust storm events over Delhi: verification of dust AOD forecasts with satellite and surface observations

    NASA Astrophysics Data System (ADS)

    Singh, Aditi; Iyengar, Gopal R.; George, John P.

    2016-05-01

    Thar desert located in northwest part of India is considered as one of the major dust source. Dust storms originate in Thar desert during pre-monsoon season, affects large part of Indo-Gangetic plains. High dust loading causes the deterioration of the ambient air quality and degradation in visibility. Present study focuses on the identification of dust events and verification of the forecast of dust events over Delhi and western part of IG Plains, during the pre-monsoon season of 2015. Three dust events have been identified over Delhi during the study period. For all the selected days, Terra-MODIS AOD at 550 nm are found close to 1.0, while AURA-OMI AI shows high values. Dust AOD forecasts from NCMRWF Unified Model (NCUM) for the three selected dust events are verified against satellite (MODIS) and ground based observations (AERONET). Comparison of observed AODs at 550 nm from MODIS with NCUM predicted AODs reveals that NCUM is able to predict the spatial and temporal distribution of dust AOD, in these cases. Good correlation (~0.67) is obtained between the NCUM predicted dust AODs and location specific observations available from AERONET. Model under-predicted the AODs as compared to the AERONET observations. This may be mainly because the model account for only dust and no anthropogenic activities are considered. The results of the present study emphasize the requirement of more realistic representation of local dust emission in the model both of natural and anthropogenic origin, to improve the forecast of dust from NCUM during the dust events.

  4. Periodic waves in the lower thermosphere observed by OI630 nm airglow images

    NASA Astrophysics Data System (ADS)

    Paulino, I.; Medeiros, A. F.; Vadas, S. L.; Wrasse, C. M.; Takahashi, H.; Buriti, R. A.; Leite, D.; Filgueira, S.; Bageston, J. V.; Sobral, J. H. A.; Gobbi, D.

    2016-02-01

    Periodic wave structures in the thermosphere have been observed at São João do Cariri (geographic coordinates: 36.5° W, 7.4° S; geomagnetic coordinates based on IGRF model to 2015: 35.8° E, 0.48° N) from September 2000 to November 2010 using OI630.0 nm airglow images. During this period, which corresponds to almost one solar cycle, characteristics of 98 waves were studied. Similarities between the characteristics of these events and observations at other places around the world were noted, primarily the spectral parameters. The observed periods were mostly found between 10 and 35 min; horizontal wavelengths ranged from 100 to 200 km, and phase speed from 30 to 180 m s-1. These parameters indicated that some of the waves, presented here, are slightly faster than those observed previously at low and middle latitudes (Indonesia, Carib and Japan), indicating that the characteristics of these waves may change at different places. Most of observed waves have appeared during magnetically quiet nights, and the occurrence of those waves followed the solar activity. Another important characteristic is the quasi-monochromatic periodicity that distinguish them from the single-front medium-scale traveling ionospheric disturbances (MSTIDs) that have been observed previously over the Brazilian region. Moreover, most of the observed waves did not present a phase front parallel to the northeast-southwest direction, which is predicted by the Perkins instability process. It strongly suggests that most of these waves must have had different generation mechanisms from the Perkins instability, which have been pointed out as being a very important mechanism for the generation of MSTIDs in the lower thermosphere.

  5. Estimating interevent time distributions from finite observation periods in communication networks

    NASA Astrophysics Data System (ADS)

    Kivelä, Mikko; Porter, Mason A.

    2015-11-01

    A diverse variety of processes—including recurrent disease episodes, neuron firing, and communication patterns among humans—can be described using interevent time (IET) distributions. Many such processes are ongoing, although event sequences are only available during a finite observation window. Because the observation time window is more likely to begin or end during long IETs than during short ones, the analysis of such data is susceptible to a bias induced by the finite observation period. In this paper, we illustrate how this length bias is born and how it can be corrected without assuming any particular shape for the IET distribution. To do this, we model event sequences using stationary renewal processes, and we formulate simple heuristics for determining the severity of the bias. To illustrate our results, we focus on the example of empirical communication networks, which are temporal networks that are constructed from communication events. The IET distributions of such systems guide efforts to build models of human behavior, and the variance of IETs is very important for estimating the spreading rate of information in networks of temporal interactions. We analyze several well-known data sets from the literature, and we find that the resulting bias can lead to systematic underestimates of the variance in the IET distributions and that correcting for the bias can lead to qualitatively different results for the tails of the IET distributions.

  6. Estimating interevent time distributions from finite observation periods in communication networks.

    PubMed

    Kivelä, Mikko; Porter, Mason A

    2015-11-01

    A diverse variety of processes-including recurrent disease episodes, neuron firing, and communication patterns among humans-can be described using interevent time (IET) distributions. Many such processes are ongoing, although event sequences are only available during a finite observation window. Because the observation time window is more likely to begin or end during long IETs than during short ones, the analysis of such data is susceptible to a bias induced by the finite observation period. In this paper, we illustrate how this length bias is born and how it can be corrected without assuming any particular shape for the IET distribution. To do this, we model event sequences using stationary renewal processes, and we formulate simple heuristics for determining the severity of the bias. To illustrate our results, we focus on the example of empirical communication networks, which are temporal networks that are constructed from communication events. The IET distributions of such systems guide efforts to build models of human behavior, and the variance of IETs is very important for estimating the spreading rate of information in networks of temporal interactions. We analyze several well-known data sets from the literature, and we find that the resulting bias can lead to systematic underestimates of the variance in the IET distributions and that correcting for the bias can lead to qualitatively different results for the tails of the IET distributions.

  7. Multi-Spacecraft Observations of Interplanetary Shock Accelerated Particle Events

    NASA Technical Reports Server (NTRS)

    Ho, G. C.; Lario, D.; Decker, R. B.; Desai, M. I.; Hu, Q.; Kasper, J.

    2006-01-01

    We use simultaneous measurements from the Wind and ACE spacecraft to determine the spatial properties of both interplanetary (IP) shocks and the shock-associated energetic particle events. We combine plasma, magnetic field and energetic particle data from ACE and Wind for 124 energetic storm particle (ESP) events from 1998 to 2003 and examine the spatial and temporal variations of these events in the Earth's vicinity. We find that even though the two spacecraft were occasionally separated by more than 400 RE, the plasma, field, and energetic particle time-intensity profiles during the events were very similar. In addition, we find that the ion composition and energy spectra in individual IP shock events are identical at the two spacecraft locations. We also use the fitted shock velocity along the normal from ACE and estimate the shock transit time to Wind location. In general, there is poor agreement between the estimated transit time and the actual measured transit time. Hence, our assumptions that a) the IP shock at 1 AU propagates radially, and/or b) the IP shock is spherically symmetric at 1 AU are not valid. In this paper, we will also study, for the first time, the anisotropy measurements of low-energy IP shock-associated ions at both ACE and Wind. We will then compare these new anisotropy analyses with locally measured shock parameters and identify possible signatures of different shock acceleration processes as predicted by the first-order Fermi and shock-drift models.

  8. Experimental observation of 3-D, impulsive reconnection events in a laboratory plasma

    SciTech Connect

    Dorfman, S.; Ji, H.; Yamada, M.; Yoo, J.; Lawrence, E.; Myers, C.; Tharp, T. D.

    2014-01-15

    Fast, impulsive reconnection is commonly observed in laboratory, space, and astrophysical plasmas. In this work, impulsive, local, 3-D reconnection is identified for the first time in a laboratory current sheet. The two-fluid, impulsive reconnection events observed on the Magnetic Reconnection Experiment (MRX) [Yamada et al., Phys Plasmas 4, 1936 (1997)] cannot be explained by 2-D models and are therefore fundamentally three-dimensional. Several signatures of flux ropes are identified with these events; 3-D high current density regions with O-point structure form during a slow buildup period that precedes a fast disruption of the reconnecting current layer. The observed drop in the reconnection current and spike in the reconnection rate during the disruption are due to ejection of these flux ropes from the layer. Underscoring the 3-D nature of the events, strong out-of-plane gradients in both the density and reconnecting magnetic field are found to play a key role in this process. Electromagnetic fluctuations in the lower hybrid frequency range are observed to peak at the disruption time; however, they are not the key physics responsible for the impulsive phenomena observed. Important features of the disruption dynamics cannot be explained by an anomalous resistivity model. An important discrepancy in the layer width and force balance between the collisionless regime of MRX and kinetic simulations is also revisited. The wider layers observed in MRX may be due to the formation of flux ropes with a wide range of sizes; consistent with this hypothesis, flux rope signatures are observed down to the smallest scales resolved by the diagnostics. Finally, a 3-D two-fluid model is proposed to explain how the observed out-of-plane variation may lead to a localized region of enhanced reconnection that spreads in the direction of the out-of-plane electron flow, ejecting flux ropes from the layer in a 3-D manner.

  9. Survey of DMSP Charging Events During the Period Preceding Cycle 23 Solar Maximum

    NASA Technical Reports Server (NTRS)

    Parker, Linda Neergaard; Minow, Joseph I.

    2013-01-01

    It has been well established that POLAR orbiting satellites can see mild to severe charging levels during solar minimum conditions (Frooninckx and Sojka, 1992, Anderson and Koons, 1996, Anderson, 2012). However, spacecraft operations during solar maximum cannot be considered safe from auroral charging. Recently, we have seen examples of high level charging during the recent approach to solar maximum. We present here a survey of charging events seen by the Defense Meteorological Satellite Program (DMSP) satellites (F16, F17) during the solstices of 2011 and 2012. In this survey, we summarize the condition necessary for charging to occur in this environment, we describe how the lower than normal maximum conditions are conducive to the environment conditions necessary for charging in the POLAR orbit, and we show examples of the more extreme charging events, sometimes exceeding 1 kV, during this time period. We also show examples of other interesting phenomenological events seen in the DMSP data, but which are not considered surface charging events, and discuss the differences.

  10. An observation-based approach to identify local natural dust events from routine aerosol ground monitoring

    NASA Astrophysics Data System (ADS)

    Tong, D. Q.; Dan, M.; Wang, T.; Lee, P.

    2012-02-01

    Dust is a major component of atmospheric aerosols in many parts of the world. Although there exist many routine aerosol monitoring networks, it is often difficult to obtain dust records from these networks, because these monitors are either deployed far away from dust active regions (most likely collocated with dense population) or contaminated by anthropogenic sources and other natural sources, such as wildfires and vegetation detritus. Here we propose a new approach to identify local dust events relying solely on aerosol mass and composition from general-purpose aerosol measurements. Through analyzing the chemical and physical characteristics of aerosol observations during satellite-detected dust episodes, we select five indicators to be used to identify local dust records: (1) high PM10 concentrations; (2) low PM2.5/PM10 ratio; (3) higher concentrations and percentage of crustal elements; (4) lower percentage of anthropogenic pollutants; and (5) low enrichment factors of anthropogenic elements. After establishing these identification criteria, we conduct hierarchical cluster analysis for all validated aerosol measurement data over 68 IMPROVE sites in the Western United States. A total of 182 local dust events were identified over 30 of the 68 locations from 2000 to 2007. These locations are either close to the four US Deserts, namely the Great Basin Desert, the Mojave Desert, the Sonoran Desert, and the Chihuahuan Desert, or in the high wind power region (Colorado). During the eight-year study period, the total number of dust events displays an interesting four-year activity cycle (one in 2000-2003 and the other in 2004-2007). The years of 2003, 2002 and 2007 are the three most active dust periods, with 46, 31 and 24 recorded dust events, respectively, while the years of 2000, 2004 and 2005 are the calmest periods, all with single digit dust records. Among these deserts, the Chihuahua Desert (59 cases) and the Sonoran Desert (62 cases) are by far the most active

  11. Tests of ionospheric control of young injection events identified from magnetometer observations at Saturn

    NASA Astrophysics Data System (ADS)

    Kivelson, M.; Jia, X.

    2015-12-01

    Kennelly et al. (2013) reported that young plasma injection events observed in Saturn's nightside magnetosphere and identified from plasma wave signatures are modulated at the period associated with the winter hemisphere. In a system unstable to interchange, radial motion of flux tubes is constrained by the "line-tying" effect of high ionospheric conductance (Southwood and Kivelson, 1989). Slippage of a flux tube would then occur initially in the hemisphere in which the ionospheric conductance is lowest. Saturn's ionospheric conductances vary not only with season, but also with rotation phase because of the presence of a pattern of rotating field-aligned currents that drive "planetary period oscillations" (Jia and Kivelson, 2012). The conductance should minimize near the center of the downward current region and, at this rotation phase in the winter hemisphere, the growth rate of the instability would be largest, accounting for control by the northern period. With motion starting in the winter hemisphere, the flux tube would develop a tilt of predictable sense and the initial inward motion of the interchanging flux tube would occur at a specific rotation phase of the winter ionosphere. For a subset of the Kennelly events, we found that the tilt and phase are consistent with expectations based on the control of displacement by ionospheric conductance. Many additional young interchange events have been identified by K. K. Khurana [personal communication, 2015] whom we thank for making the list available. We examine this more extensive set of events and use them to investigate the proposed mechanism more fully. __________ Jia, X., and M. G. Kivelson (2012), J. Geophys. Res., 117, A11219. Kennelly, T. J., J. S. Leisner, G. B. Hospodarsky, and D. A. Gurnett (2013), J. Geophys. Res. Space Physics, 118, 832-838. Kivelson, M., and X. Jia (2014), , AGU Fall meeting, 2014, SM51E-4295. Southwood, D. J., and M. G. Kivelson (1989), J. Geophys. Res., 94, 299-308.

  12. Long-period seismic events with strikingly regular temporal patterns on Katla volcano's south flank (Iceland)

    NASA Astrophysics Data System (ADS)

    Sgattoni, Giulia; Jeddi, Zeinab; Gudmundsson, Ólafur; Einarsson, Páll; Tryggvason, Ari; Lund, Björn; Lucchi, Federico

    2016-09-01

    Katla is a threatening volcano in Iceland, partly covered by the Mýrdalsjökull ice cap. The volcano has a large caldera with several active geothermal areas. A peculiar cluster of long-period seismic events started on Katla's south flank in July 2011, during an unrest episode in the caldera that culminated in a glacier outburst. The seismic events were tightly clustered at shallow depth in the Gvendarfell area, 4 km south of the caldera, under a small glacier stream at the southern margin of Mýrdalsjökull. No seismic events were known to have occurred in this area before. The most striking feature of this seismic cluster is its temporal pattern, characterized by regular intervals between repeating seismic events, modulated by a seasonal variation. Remarkable is also the stability of both the time and waveform features over a long time period, around 3.5 years. We have not found any comparable examples in the literature. Both volcanic and glacial processes can produce similar waveforms and therefore have to be considered as potential seismic sources. Discerning between these two causes is critical for monitoring glacier-clad volcanoes and has been controversial at Katla. For this new seismic cluster on the south flank, we regard volcano-related processes as more likely than glacial ones for the following reasons: 1) the seismic activity started during an unrest episode involving sudden melting of the glacier and a jökulhlaup; 2) the glacier stream is small and stagnant; 3) the seismicity remains regular and stable for years; 4) there is no apparent correlation with short-term weather changes, such as rainstorms. We suggest that a small, shallow hydrothermal system was activated on Katla's south flank in 2011, either by a minor magmatic injection or by changes of permeability in a local crack system.

  13. Characterization And State-Of-The-Art Modeling Of Extreme Precipitation Events Over Africa During The Historical Period

    NASA Astrophysics Data System (ADS)

    Gibba, P.; Sylla, M. B.

    2015-12-01

    The ability of the state-of-the-art climate models to reproduce the mean spatial characteristics of extreme precipitation indices over Africa is evaluated. The ensembles of eight precipitation-based indices as defined by ETCCDI were extracted from seventeen CMIP5 GCMs and twelve CORDEX RCMs simulations based on absolute and percentile (95th) thresholds and computed from the 1975 to 2004 historical period. Daily precipitation indices calculated from GPCP and TRMM satellite-derived observation datasets during the period 1997 to 2012 and 1998 to 2011 respectively were also employed in this study for model validation. Results of spatial representation of the frequency of extreme precipitation events (R1mm, CDD, CWD and R95p) highlight a generally good consistency between the two observations. Equally, in the regional analysis some similarities exist in their median and interquartile (25th and 75th percentile) spread especially for CDD, CWD and R95p for most regions. In the associated intensities (SDII, RX5day, R95 and R95ptot), results indicate large spatial differences between the two observational datasets, with finer resolution TRMM generating higher rainfall intensities than the coarser resolution GPCP. TRMM has also demonstrated higher median and interquartile range as compared to GPCP. The CORDEX RCMs and CMIP5 GCMs simulations have estimated more number of extreme precipitation events, while underestimated the intensities. The differences between the models and observations can be as large as the typical model interquartile spread of the ensembles for some indices (R1mm, CWD, SDII and R95) in some regions. Meanwhile, CORDEX estimations are generally closer to the observations than CMIP5 in reproducing the frequency of extreme rainfall indices. For the estimation of rainfall intensities, CORDEX simulations are in most cases more consistence with TRMM observations whilst the CMIP5 GCMs simulations are closer to GPCP observations.

  14. On quasi-periodic variations of low-energy cosmic rays observed near earth.

    PubMed

    Kudela, Karel; Langer, Ronald

    2015-06-01

    Cosmic ray (CR) may partially, especially at high altitudes, contribute to the dosimetric characteristics. Along with irregular CR variations as Forbush decreases and solar particle events are, the quasi-periodic variations may be of some relevance too. A very short review (with references to original papers) of the present knowledge of various types of such variations is presented, namely (i) diurnal wave, (ii) ~27 d variability due to the solar rotation, (iii) Rieger-type periodicity, and (iv) quasi-biennial oscillations as well as waves on longer time scales related to solar activity and to polarity of magnetic field of the Sun. Variability is illustrated in measurements of secondary CR on the ground including the high-altitude observations at Lomnický štít.

  15. Recurrence times and periodicities in 4U 1608-52 as observed by Vela 5B

    NASA Technical Reports Server (NTRS)

    Lochner, James C.; Roussel-Dupre, Diane

    1994-01-01

    We report on the Vela 5B 10 year history of the soft X-ray transient 4U 1608-52, and on the characteristics of its soft X-ray outbursts. The Vela 5B satellite observed the four known outbursts in 1975, 1977, and 1979, and four new outbursts in 1970 and 1971, altering the recurrence pattern of outbursts from this source. One of the 1970 outbursts is symmetric in its intensity profile, while the two outbursts in 1971 have short exponential profiles separated by 80 days. Despite suggestive recurrence periods of approximately 85 and approximately 150 days evident in the time intervals between the outbursts, there is no single statistically significant recurrence time on which the outbursts recur consistently. In the 1970 symmetric event, there is evidence for a period of either 4.10 or 5.19 days. Drawing upon the analogy with SU Ursa Majoris dwarf novae, we suggest that the short period is orbital and any longer period would be associated with a precession period of the accretion disk.

  16. Comparative energetics of the observed and simulated global circulation during the special observing periods of FGGE

    NASA Technical Reports Server (NTRS)

    Kung, E. C.; Baker, W. E.

    1986-01-01

    Energetics of the observed and simulated global circulation are evaluated in the zonal spectral domain for the special observing periods of FGGE. The study utilizes GLA analyses of FGGE observational data and parallel simulation experiments. There are noticeable differences in energy transformations between the observation and simulation during SOP-1. These include the baroclinic conversion C(n) by the zonal mean motion and short-wave disturbances, and the nonlinear wave-wave interaction L(n) at the long and short waves. The energy transformations of the short-wave disturbances are much more intense in the simulated circulation than in the observation. However, good agreement is noted in the conversion and dissipation of kinetic energy in the large- and cyclone-wave range n = 1-10. Spectral distributions of global energy transformations at the long- and cyclone-wave range indicate that the SOP-2 simulation agrees more closely with the observed fields than the SOP-1 simulation. Other pertinent points of energetics diagnosis are also included in the discussion.

  17. Concentric waves and short-period oscillations observed in the ionosphere after the 2013 Moore EF5 tornado

    NASA Astrophysics Data System (ADS)

    Nishioka, Michi; Tsugawa, Takuya; Kubota, Minoru; Ishii, Mamoru

    2013-11-01

    We detected clear concentric waves and short-period oscillations in the ionosphere after an Enhanced Fujita scale (EF)5 tornado hit Moore, Oklahoma, U.S., on 20 May 2013 using dense wide-coverage ionospheric total electron content (TEC) observations in North America. These concentric waves were nondispersive, with a horizontal wavelength of ~120 km and a period of ~13 min. They were observed for more than 7 h throughout North America. TEC oscillations with a period of ~4 min were also observed to the south of Moore for more than 8 h. A comparison between the TEC observations and infrared cloud image from the GOES satellite indicates that the concentric waves and short-period oscillations are caused by supercell-induced atmospheric gravity waves and acoustic resonances, respectively. This observational result provides the first clear evidence of a severe meteorological event causing atmospheric waves propagating upward in the upper atmosphere and reaching the ionosphere.

  18. Observations on the cortical silent period in Parkinson's disease.

    PubMed

    Van Der Werf, Y D; Berendse, H W; van Someren, E J W; Stoffers, D; Stam, C J; Wolters, E Ch

    2007-01-01

    Transcranial magnetic stimulation is a tool in the neurosciences to study motor functions and nervous disorders, amongst others. Single pulses of TMS applied over the primary motor cortex lead to a so-called cortical silent period in the recording from the corresponding muscle, i.e. a period of approximately 100ms with no muscle activity. We here show that in Parkinson's disease (PD), this cortical silent period in some cases is interrupted by short bursts of EMG activity. We describe in detail these interruptions in two patients with PD. These interruptions may number up to 3 per cortical silent period and show a consistent frequency across trials and hemispheres within a given patient; the two patients described here do differ, however, in the time-delay of the interruptions and hence the induced frequency. For one patient, the frequency of the interruptions proved to be around 13 Hz, the other patient showed a frequency of around 17 Hz. The results corroborate earlier findings of cortical oscillations elicited by pulses of TMS and may be related to abnormal oscillatory activity found in the cortical-subcortical motor system in PD.

  19. Drifting Quasi-Periodic Modulation of the Fast Magnetosonic Mode: Van Allen Probe Observations

    NASA Astrophysics Data System (ADS)

    Boardsen, S. A.; Hospodarsky, G. B.; Kletzing, C.; Pfaff, R. F., Jr.; Kurth, W. S.; Wygant, J. R.; MacDonald, E.

    2014-12-01

    The fast magnetosonic mode is one of the dominant wave modes in the Earth's radiation belts. These waves influence the ring current by scattering ions in energy in the 10's of keV range, and are believed to be a heat source for radiation belt electrons. The fast magnetosonic mode observed around the Earth's inner equatorial magnetosphere sometimes exhibits quasi-periodic modulation as detected by the Van Allen probes. During each modulation the wave frequency exhibits a strong drifting (dispersive) signature characterized by a rising tone. Each tone is composed of harmonics with spacing close to the proton cyclotron frequency. The tones are band limited in frequency and mainly observed above the 20th harmonic of the local proton cyclotron frequency. We observe this modulation mainly outside the plasmapause, but it has also been observed to penetrate down to 1.5 RE. The modulation is observed up to magnetic latitudes of ±17º, at all magnetic local times, but its signatures are more pronounced on the dayside. For events where lower frequency ULF waves are detected, the period of the ULF wave is about twice the modulation period of the fast magnetosonic mode, suggesting strong wave-wave interactions. The modulation period varies from 50 to 200 s and its duration ranges from 0.2 to 3 h, with the maximum duration limited by the spacecraft orbit. We hypothesize that the rising tone is produced by changing Alfven velocities created by steepened density fluctuations due to plasma modification by an underlying ULF wave.

  20. Array analysis of the seismic wavefield of long-period events and volcanic tremor at Arenal volcano, Costa Rica

    NASA Astrophysics Data System (ADS)

    Almendros, Javier; Abella, Rafael; Mora, Mauricio M.; Lesage, Philippe

    2014-07-01

    We use wavefield decomposition methods (time domain cross correlation and frequency domain multiple-signal classification) to analyze seismic data recorded by a dense, small-aperture array located 2 km West of Arenal volcano, Costa Rica, and operated during 2.5 days. The recorded wavefield is dominated by harmonic tremor and includes also spasmodic tremor and long-period (LP) events. We find that the initial stages of LP events are characterized by three different wave arrivals. These arrivals propagate with similar back azimuths pointing to the volcano summit (˜80°N) and increasing apparent slowness of 0.4, 1.1, and 1.7 s/km. Spasmodic tremors cannot be regarded as coherent signals. On the contrary, harmonic tremors are highly coherent, characterized by the stability of the apparent slowness vector estimates. Apparent slowness lays in the range 1-2 s/km. Back azimuths point in the general direction of the volcano but with a large variability (40-120°N). Nevertheless, there are long-term variations and evidences of multiple simultaneous components in the harmonic tremor wavefield. These observations suggest that LP events and tremor are generated in a shallow source area near the volcano summit, although they do not share exactly the same source region or source processes. The tremor source is located in the shallowest part of the plumbing system, beneath the lava crust. This dynamic region is subject to complex fluctuations of the physical conditions. Degassing events at different locations of this region might generate variable seismic radiation patterns. The effects of topography and heterogeneous shallow structure of the volcano may amplify these variations and produce the wide directional span observed for volcanic tremor. On the other hand, the LP source seems to be more repeatable. LP events are likely triggered by fragmentation of the fluid flow in a slightly deeper portion of the volcanic conduits.

  1. Comparisons of water quality parameters from diverse catchments during dry periods and following rain events.

    PubMed

    Shah, Vikaskumar G; Dunstan, R Hugh; Geary, Phillip M; Coombes, Peter; Roberts, Timothy K; Rothkirch, Tony

    2007-08-01

    In this study, 12 catchments sites located along the north coast of New South Wales in Australia were grouped into the four categories of septic, cattle, sewage treatment plant (STP) and forested sites via cluster analysis based on their land use patterns. Water samples from all these sites were collected between October 2004 and June 2006 at a regular monthly interval and within 48 h of rain events. The samples were analyzed for bacterial counts including faecal coliform and total coliform; faecal sterols including coprostanol, epicoprostanol, cholesterol, cholestanol, 24-ethylcoprostanol, campesterol, stigmasterol and beta-sitosterol; and the elements including Na, Rb, Sr, Ag, Cd, Sn, Cs, Ba, Hg, Tl, Pb, Bi, U, Mg, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, K, As, Se, P and Mo. Over the course of the sampling period, the STP site had the highest average coprostanol level of 1693+/-567 ng/L which was significantly higher (p<0.05) than the septic sites (190+/-71 ng/L), the cattle sites (163+/-94 ng/L) and forested sites (14+/-4 ng/L). As expected, the forested sites had significantly lower average level of faecal coliforms (373+/-87 cfu/100 mL) compared with the STP (1395+/-574 cfu/100 mL), septic (1243+/-494 cfu/100 mL) and cattle sites (535+/-112 cfu/100 mL). The concentrations of coprostanol were not correlated with the numbers of faecal coliform bacteria when the entire data set was evaluated. The forested sites generally had the lowest average levels of elemental compositions, with significantly lower levels noted for Na, U, Mg, V, Cu, Sr, K, As, P and Mo, whereas Fe was the only element notably higher in the forested sites. Temporal and rain events analyses of the data set revealed that elevated levels of both coprostanol and faecal coliforms were not exclusive to rain events. The average coprostanol levels in rain event samples at each site were not significantly different compared with the corresponding dry event samples. Conversely, faecal coliform numbers increased

  2. Periodic Mid-cretaceous Ocean Anoxic Events Linked By Oscillations of The Phosphorus and Oxygen Cycles

    NASA Astrophysics Data System (ADS)

    Lenton, T.; Handoh, I.

    A series of ocean anoxic events (OAEs) occurred in the mid-Cretaceous warm period (120-80 Ma) that have been linked with high rates of organic carbon burial, warm high- and low- latitude temperatures and sea-level changes. OAEs have been studied individually, but a causal mechanism that connects them has been lacking. We show that peaks in global reactive phosphorus accumulation rate coincide with OAEs 1d, 2 and 3, and exhibit a 6 Myr periodicity over 100-80 Ma. Oxic-anoxic oscillations of 6 Myr period can be triggered in a model of the coupled N, P, C and O2 biogeochemical cycles, by increasing phosphorus weathering rates. The oscillations are sustained by a positive feedback between phosphate concentration, new production and anoxia and a counteracting but slower negative feedback between atmospheric oxygen and anoxia. We suggest that elevated atmospheric CO2 and global warmth driven by increased tectonic and volcanic activity 120-80 Ma, together with the rise of flowering plants 100 Ma, drove increased phosphorus weathering rates and triggered periodic OAEs in the mid-Cretaceous.

  3. Observation and Analysis of Jovian and Saturnian Satellite Mutual Events

    NASA Technical Reports Server (NTRS)

    Tholen, David J.

    2001-01-01

    The main goal of this research was to acquire high time resolution photometry of satellite-satellite mutual events during the equatorial plane crossing for Saturn in 1995 and Jupiter in 1997. The data would be used to improve the orbits of the Saturnian satellites to support Cassini mission requirements, and also to monitor the secular acceleration of Io's orbit to compare with heat flow measurements.

  4. Estimating return periods for daily precipitation extreme events over the Brazilian Amazon

    NASA Astrophysics Data System (ADS)

    Santos, Eliane Barbosa; Lucio, Paulo Sérgio; Santos e Silva, Cláudio Moisés

    2016-11-01

    This paper aims to model the occurrence of daily precipitation extreme events and to estimate the return period of these events through the extreme value theory (generalized extreme value distribution (GEV) and the generalized Pareto distribution (GPD)). The GEV and GPD were applied in precipitation series of homogeneous regions of the Brazilian Amazon. The GEV and GPD goodness of fit were evaluated by quantile-quantile (Q-Q) plot and by the application of the Kolmogorov-Smirnov (KS) test, which compares the cumulated empirical distributions with the theoretical ones. The Q-Q plot suggests that the probability distributions of the studied series are appropriated, and these results were confirmed by the KS test, which demonstrates that the tested distributions have a good fit in all sub-regions of Amazon, thus adequate to study the daily precipitation extreme event. For all return levels studied, more intense precipitation extremes is expected to occur within the South sub-regions and the coastal area of the Brazilian Amazon. The results possibly will have some practical application in local extreme weather forecast.

  5. Results of Lunar Impact Observations During Geminid Meteor Shower Events

    NASA Technical Reports Server (NTRS)

    Suggs, R. J.; Suggs, R. M.

    2015-01-01

    Geminids' relatively large intensity and unique origin, it is important to monitor and gain information about the Geminids so as to improve their forecasts and understand their contribution to the meteoroid environment in Earth's orbit and at the Moon. It is the purpose of this Technical Memorandum (TM) to document two lunar observing periods coinciding with the Geminid meteor showers that occurred in 2006 and 2010.

  6. GLE and the NON-GLE Solar Events Observed by AMS-02 in Solar Cycle 24

    NASA Astrophysics Data System (ADS)

    Bindi, V.; Consolandi, C.; Corti, C.; Whitman, K.

    2014-12-01

    The Alpha Magnetic Spectrometer (AMS-02) is a high energy particle detector installed on the International Space Station (ISS) on May 2011 to study origin and nature of cosmic rays in the energy range from hundreds of MeV to a few TeV. In the first 3 years of operation, AMS-02 measured the highest part of the Solar Energetic Particle (SEP) spectra produced during M-and X-class flares and fast Coronal Mass Ejection. AMS-02 is able to perform precise measurements in a short period of time which is typical of these transient phenomena and to collected enough statistics to fully measure fine structures and time evolution of the spectrum. So far in Solar Cycle 24, one official Ground Level Enhancement (GLE) was observed on May 17, 2012 by Neutron Monitors (NM) while another possible GLE on January 6, 2014 was detected by South Pole NM. Observations by GOES-13, in the high energy proton channels, suggest that there were only 5 SEP events with energies above 500 MeV in this Cycle 24. AMS-02 observations, instead, indicate that since May 2011 there were more than 5 solar events with energies above 500 MeV at Earth. AMS-02 observations, with unprecedented resolution, large acceptance and high statistics, can therefore help the heliophysics community to better understand the true behavior of SEPs at high energies and to constrain models of SEP production. The SEP fluxes of GLE and NON-GLE events observed by AMS-02 will be presented.

  7. Adverse events from spinal manipulation in the pregnant and postpartum periods: a critical review of the literature

    PubMed Central

    2012-01-01

    Background The safety of spinal manipulation during pregnancy and the postpartum periods has been a matter of debate among manual therapists. Spinal manipulative therapy during these periods is a commonly performed intervention as musculoskeletal pain is common in these patients. To date there has not been an evaluation of the literature on this topic exclusively. Methods A literature search was conducted on PubMed, CINAHL and the Index to Chiropractic Literature along with reference searching for articles published in English and French in the peer-reviewed literature that documented adverse effects of spinal manipulation during either pregnancy or postpartum. Case reports, case series, and any other clinical study designs were deemed acceptable for inclusion, as were systematic reviews. The appropriate Scottish Intercollegiate Guidelines Network (SIGN) tools were used to rate included articles for quality when applicable. Results Five articles identifying adverse events in seven subjects following spinal manipulation were included in this review, along with two systematic reviews. The articles were published between 1978 and 2009. Two articles describing adverse effects from spinal manipulation on two postpartum patients were included, while the remaining three articles on five patients with adverse effects following spinal manipulation were on pregnant patients. Injury severity ranged from minor injury such as increasing pain after treatment that resolved within a few days to more severe injuries including fracture, stroke, and epidural hematoma. SIGN scores of the prospective observational cohort study and systematic reviews indicated acceptable quality. Conclusions There are only a few reported cases of adverse events following spinal manipulation during pregnancy and the postpartum period identified in the literature. While improved reporting of such events is required in the future, it may be that such injuries are relatively rare. PMID:22455720

  8. Observations of Very-Long-Period Tremor at the Tatun Volcano Group, Northern Taiwan

    NASA Astrophysics Data System (ADS)

    Yeh, Y.; Lin, C.; Konstantino, K.

    2006-12-01

    The Tatun Volcano Group lies at the northern tip of Taiwan and is only 15 km north of the capital Taipei, which has more than seven million inhabitants. To examine the possibility of both volcanic and seismic activity in the future, a dense seismic array consisting of 8 stations equipped with both broad-band and short-period sensors has been installed in Tatun area since 2003. In addition to common volcano-tectonic earthquakes, we have observed a variety of volcanoseismic signals such as tornillos, short duration monochromatic events and long duration spasmodic bursts from the short-period seismic data. Further examination of broadband seismic data shows that there also were some very-long-period (VLP) volcanic signals, which are often reported at some active volcanoes in the world. Based on the polarization and travel-time of the VLP signals recorded at 4 broadband stations, the source of VLP seismic signals was located at a depth around 2.0 km. These observations put into doubt the long-standing suggestion that the Tatun volcanoes are extinct and prompt for a thorough assessment of the volcanic hazard for this area.

  9. Large-Scale periodic solar velocities: An observational study

    NASA Technical Reports Server (NTRS)

    Dittmer, P. H.

    1977-01-01

    Observations of large-scale solar velocities were made using the mean field telescope and Babcock magnetograph of the Stanford Solar Observatory. Observations were made in the magnetically insensitive ion line at 5124 A, with light from the center (limb) of the disk right (left) circularly polarized, so that the magnetograph measures the difference in wavelength between center and limb. Computer calculations are made of the wavelength difference produced by global pulsations for spherical harmonics up to second order and of the signal produced by displacing the solar image relative to polarizing optics or diffraction grating.

  10. CRRES observations of ion composition during EMIC mode wave events

    SciTech Connect

    Macdonald, Elizabeth; Larsen, Brian

    2010-12-13

    EMIC mode waves may play an important role in the dynamics of the growth and loss of the radiation belts. CRRES mission analysis has provided extensive information on the distributions of EMIC mode waves. Less well studied and understood is the role that ion composition plays in the formation of the EMIC mode waves. The CRESS plasma mass spectrometer LOMICS measured all ion species of interest up to 45 keV/q. This preliminary study will examine the characteristics of heavy ions during a multitude of wave events, in particular, the effect of ion composition on wave-particle interactions, amplitude, and frequency. The relevance of such data to the upcoming RBSP mission will be highlighted.

  11. Human event observations in the individual plant examinations

    SciTech Connect

    Forester, J.

    1995-04-01

    A major objective of the Individual Plant Examination Insights Program is to identify the important determinants of core damage frequency for the different reactor and containment types and plant designs as indicated in the IPEs. The human reliability analysis is a critical component of the probabilistic risk assessments which were done for the IPEs. The determination and selection of human actions for incorporation into the event and fault tree models and the quantification of their failure probabilities can have an important impact on the resulting estimates of CDF and risk. Two important goals of the NRCs IPE Insights Program are (1) to determine the extent to which human actions and their corresponding failure probabilities influenced the results of the IPEs and (2) to identify which factors played significant roles in determining the differences and similarities in the results of the HRA analyses across the different plants. To obtain the relevant information, the NRC`s IPE database, which contains information on plant design, CDF, and containment performance obtained from the IPEs, was used in conjunction with a systematic examination of the HRA analyses and results from the IPEs. Regarding the extent to which the results of the HRA analyses were significant contributors to the plants` CDFs, examinations of several different measures indicated that while individual human actions could have important influences on CDF for particular initiators, the HRA results did not appear to be the most significant driver of plant risk. Another finding was that while there were relatively wide variations in the calculated human error probabilities for similar events across plants, there was no evidence for any systematic variation as a function of the HRA methods used in the analyses. Much of the variability in HEP values can be explained by differences in plant characteristics and sequence-specific factors. Details of these results and other findings are discussed.

  12. Human event observations in the individual plant examinations

    SciTech Connect

    Forester, J.

    1995-01-01

    A major objective of the Nuclear Regulatory Commission`s (NRC) Individual Plant Examination (IPE) Insights Program is to identify the important determinants of core damage frequency (CDF) for the different reactor and containment types and plant designs as indicated in the IPEs. The human reliability analysis (HRA) is a critical component of the probabilistic risk assessments (PRAS) which were done for the IPES. The determination and selection of human actions for incorporation into the event and fault tree models and the quantification of their failure probabilities can have an important impact on the resulting estimates of CDF and risk. Therefore, two important goals of the NRCs IPE Insights Program are (1) to determine the extent to which human actions and their corresponding failure probabilities influenced the results of the IPEs and (2) to identify which factors played significant roles in determining the differences and similarities in the results of the HRA analyses across the different plants. To obtain the relevant information, the NRC`s IPE database, which contains information on plant design, CDF, and containment performance obtained from the IPES, was used in conjunction with a systematic examination of the HRA analyses and results from the IPES. Regarding the extent to which the results of the HRA analyses were significant contributors to the plants` CDFs, examinations of several different measures indicated that while individual human actions could have important influences on CDF for particular initiators, the HRA results did not appear to be the most significant driver of plant risk (CDF). Another finding was that while there were relatively wide variations in the calculated human error probabilities (HEPs) for similar events across plants, there was no evidence for any systematic variation as a function of the HRA methods used in the analyses.

  13. Observations of the Lunar Impact Plume from the LCROSS Event

    NASA Technical Reports Server (NTRS)

    Killen, R. M.; Potter, A. E.; Hurley, D. M.; Plymate, C.; Naidu, S.

    2010-01-01

    We observed emission from sodium (Na) ejected from the Lunar Crater Observing and Sensing Satellite (LCROSS) impact into Cabeus Crater on October 9, 2009, using the McMath-Pierce telescope. In our 88 sq km field of view, we saw on the order of2 g of Na in the first 9 minutes after the LCROSS impact. A comparison of our observed Na above the limb with simulations that assume a gas temperature of 1000 K indicates that 0.5-2.6 (1.5 +/- 1) kg of Na were released during the LCROSS impact. Lower temperatures would result in a lower total sodium release. The model of an isotropic expanding cloud best reproduces the observations.

  14. Temporal evolution of a hydrothermal system in Kusatsu-Shirane Volcano, Japan, inferred from the complex frequencies of long-period events

    USGS Publications Warehouse

    Kumagai, H.; Chouet, B.A.; Nakano, M.

    2002-01-01

    We present a detailed description of temporal variations in the complex frequencies of long-period (LP) events observed at Kusatsu-Shirane Volcano. Using the Sompi method, we analyze 35 LP events that occurred during the period from August 1992 through January 1993. The observed temporal variations in the complex frequencies can be divided into three periods. During the first period the dominant frequency rapidly decreases from 5 to 1 Hz, and Q of the dominant spectral peak remains roughly constant with an average value near 100. During the second period the dominant frequency gradually increases up to 3 Hz, and Q gradually decreases from 160 to 30. During the third period the dominant frequency increases more rapidly from 3 to 5 Hz, and Q shows an abrupt increase at the beginning of this period and then remains roughly constant with an average value near 100. Such temporal variations can be consistently explained by the dynamic response of a hydrothermal crack to a magmatic heat pulse. During the first period, crack growth occurs in response to the overall pressure increase in the hydrothermal system caused by the heat pulse. Once crack formation is complete, heat gradually changes the fluid in the crack from a wet misty gas to a dry gas during the second period. As heating of the hydrothermal system gradually subsides, the overall pressure in this system starts to decrease, causing the collapse of the crack during the third period.

  15. Investigation of a convection event using multisensor observations during HyMeX SOP1

    NASA Astrophysics Data System (ADS)

    Roberto, Nicoletta; Adirosi, Elisa; Casella, Daniele; Dietrich, Stefano; Panegrossi, Giulia; Petracca, Marco; Sanò, Paolo; Gatlin, Patrick; Baldini, Luca

    2014-05-01

    A multisensor analysis of the convective precipitation event occurred over Rome during the IOP13 (October 15th, 2012) of the HyMeX (Hydrological cycle in the Mediterranean eXperiment) Special Observation Period (SOP) 1 is presented. Thanks to the cooperation among Italian meteorological services and scientific community and a specific agreement with NASA-GSFC, different types of devices for meteorological measurements were made available during the HyMeX SOP.1. For investigating this event, used are the 3-D lightning data provided by the LINET, the CNR ISAC dual-pol C-band radar (Polar 55C), located in Rome, the Drop Size Distributions (DSD) collected by the 2D Video Disdrometer (2DVD) and the collocated Micro Rain Radar (MRR) installed at the Radio Meteorology Lab. of "Sapienza" University of Rome, located 14 km from the Polar 55C radar. The relation between microphysical structure and electrical activity during the convective phase of the event was investigated using LINET lightning data and Polar 55C (working both in PPI and RHI scanning mode) observations. Location of regions of high horizontal reflectivity (Zh) values ( > 50 dBz), indicating convective precipitation, were found to be associated to a high number of LINET strokes. In addition, an hydrometeor classification scheme applied to the Polar 55C scans was used to detect graupel and to identify a relation between number of LINET strokes and integrated IWC of graupel along the event. Properties of DSDs measured by the 2DVD and vertical DSD profiles estimated by MRR and their relation with the lighting activity registered by LINET were investigated with specific focus on the transition from convective to stratiform regimes. A good agreement was found between convection detected by these instruments and the number of strokes detected by LINET.

  16. Shallow degassing events as a trigger for very-long-period seismicity at Kīlauea Volcano, Hawai‘i

    USGS Publications Warehouse

    Patrick, Matthew; Wilson, David; Fee, David; Orr, Tim R.; Swanson, Donald A.

    2011-01-01

    The first eruptive activity at Kīlauea Volcano’s summit in 25 years began in March 2008 with the opening of a 35-m-wide vent in Halema‘uma‘u crater. The new activity has produced prominent very-long-period (VLP) signals corresponding with two new behaviors: episodic tremor bursts and small explosive events, both of which represent degassing events from the top of the lava column. Previous work has shown that VLP seismicity has long been present at Kīlauea’s summit, and is sourced approximately 1 km below Halema‘uma‘u. By integrating video observations, infrasound and seismic data, we show that the onset of the large VLP signals occurs within several seconds of the onset of the degassing events. This timing indicates that the VLP is caused by forces—sourced at or very near the lava free surface due to degassing—transmitted down the magma column and coupling to the surrounding rock at 1 km depth.

  17. Observing and Studying Extreme Low Pressure Events with Altimetry

    PubMed Central

    Carrère, Loren; Mertz, Françoise; Dorandeu, Joel; Quilfen, Yves; Patoux, Jerome

    2009-01-01

    The ability of altimetry to detect extreme low pressure events and the relationship between sea level pressure and sea level anomalies during extra-tropical depressions have been investigated. Specific altimeter treatments have been developed for tropical cyclones and applied to obtain a relevant along-track sea surface height (SSH) signal: the case of tropical cyclone Isabel is presented here. The S- and C-band measurements are used because they are less impacted by rain than the Ku-band, and new sea state bias (SSB) and wet troposphere corrections are proposed. More accurate strong altimeter wind speeds are computed thanks to the Young algorithm. Ocean signals not related to atmospheric pressure can be removed with accuracy, even within a Near Real Time context, by removing the maps of sea level anomaly (SLA) provided by SSALTO/Duacs. In the case of Extra-Tropical Depressions, the classical altimeter processing can be used. Ocean signal not related to atmospheric pressure is along-track filtered. The sea level pressure (SLP)-SLA relationship is investigated for the North Atlantic, North Pacific and Indian oceans; three regression models are proposed allowing restoring an altimeter SLP with a mean error of 5 hPa if compared to ECMWF or buoys SLP. The analysis of barotropic simulation outputs points out the regional variability of the SLP/Model Sea Level relationship and the wind effects. PMID:22573955

  18. Observing trends in total ozone and extreme ozone events

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2014-05-01

    The ozone layer in the stratosphere has been recovering since the 1989 Montreal Protocol reduced the use of ozone-destroying chlorofluorocarbons. Fitzka et al. observed trends in total ozone levels and the vertical distribution of ozone at Hoher Sonnblick, a mountain in Austria, from 1994 to 2011.

  19. A Semi-Automatic, Remote-Controlled Video Observation System for Transient Luminous Events

    NASA Astrophysics Data System (ADS)

    Allin, T.; Neubert, T.; Laursen, S.; Rasmussen, I. L.; Soula, S.

    2003-12-01

    In support for global ELF/VLF observations, HF measurements in France, and conjugate photometry/VLF observations in South Africa, we developed and operated a semi-automatic, remotely controlled video system for the observation of middle-atmospheric transient luminous events (TLEs). Installed at the Pic du Midi Observatory in Southern France, the system was operational during the period from July 18 to September 15, 2003. The video system, based two low-light, non-intensified CCD video cameras, was mounted on top of a motorized pan/tilt unit. The cameras and the pan/tilt unit were controlled over serial links from a local computer, and the video outputs were distributed to a pair of PCI frame grabbers in the computer. This setup allowed remote users to log in and operate the system over the internet. Event detection software provided means of recording and time-stamping single TLE video fields and thus eliminated the need for continuous human monitoring of TLE activity. The computer recorded and analyzed two parallel video streams at the full 50 Hz field rate, while uploading status images, TLE images, and system logs to a remote web server. The system detected more than 130 TLEs - mostly sprites - distributed over 9 active evenings. We have thus demonstrated the feasibility of remote agents for TLE observations, which are likely to find use in future ground-based TLE observation campaigns, or to be installed at remote sites in support for space-borne or other global TLE observation efforts.

  20. Earthquake Sequences Identification, from Analysis of Earthquake Occurrence Time Series Considering Multiple Semi-Periodic Sequences and Extraneous Events. Parkfield et al

    NASA Astrophysics Data System (ADS)

    Nava Pichardo, F. A.; Quinteros, C. B.; Glowacka, E.; Frez, J.

    2013-05-01

    We present a new method, based on the analytic Fourier transform, to identify semi-periodic sequences in regional large earthquake occurrence times series, which allows for the presence of multiple semi-periodic sequences and/or events not belonging to any identifiable sequence in the time series. The method yields estimates of the departure from periodicity of an observed sequence, and of the probability that the sequence is not due to chance. These estimates are used to make and to evaluate forecasts of future events belonging to each sequence. The method is surprisingly capable of correctly identifying sequences, unidentifiable by eye, in complicated time series. An example of application of the method to real seismicity data is analysis of the Parkfield event series, which correctly aftcasts the September 2004 earthquake. Other examples of sequence identification in earthquakes from central Japan and Venezuela are also shown.

  1. Coupling rainfall observations and satellite soil moisture for predicting event soil loss in Central Italy

    NASA Astrophysics Data System (ADS)

    Todisco, Francesca; Brocca, Luca; Termite, Loris Francesco; Wagner, Wolfgang

    2015-04-01

    always the lowest; the accuracy in estimating the event soil loss of a models with erosivity factor that includes the estimated runoff is always overcome by at least one model that uses the antecedent soil moisture θ in the erosivity index; the power models generally, at Masse, work better than the linear. The more accurate models are that with the estimated antecedent soil moisture, θest, when all the database is used and with the satellite retrieved soil moisture, θsat, when only the wet periods' events are considered. In fact it was also verified that much of the inaccuracy of the tested models is due to summer rainfall events, probably because of the particular characteristics that the soil assumes in the dry period (superficial crusts causing higher runoff): in this cases, high soil losses are observed in association to low values of soil moisture, while the simulated runoff assume low values too, since they are based on the antecedent wetness conditions. Thus, the analyses were repeated excluding the summer events. As expected, the performance of all the models increases, but still the use of θ provides the best results. The results of the analysis open interesting scenarios in the use of USLE-derived models for the unit event soil loss estimation at large scale. In particular the use of the soil moisture to correct the rainfall erosivity factor acquires a great practical importance, since it is a relatively simple measurable data and moreover because remote sensing soil moisture data are widely available and useful in large-scale erosion assessment. Bagarello, V., Di Piazza, G. V., Ferro, V., Giordano, G., 2008. Predicting unit soil loss in Sicily, south Italy. Hydrol. Process. 22, 586-595. Bagarello, V., Ferro, V., Giordano, G., Mannocchi, F., Todisco, F., Vergni, L., 2013. Predicting event soil loss form bare plots at two Italian sites. Catena 109, 96-102. Brocca, L., Melone, F., Moramarco, T., 2011. Distributed rainfall-runoff modeling for flood frequency

  2. Simultaneous observations of periodic non-Io decametric radio emission by ground radio telescope URAN-2 and STEREO/WAVES

    NASA Astrophysics Data System (ADS)

    Panchenko, M.; Brazhenko, A. I.; Rucker, H. O.; Frantzusenko, A.; Shaposhnikov, V. E.; Konovalenko, A. A.

    2013-09-01

    Periodic bursts of the non-Io component of Jovian decametric radio emission (non-Io DAM) is observed as (1) series of arc-like radio bursts with negative frequency drift which reoccur with 1.5% longer period than the Jovian magnetosphere rotation rate, (2) series of bursts with positive frequency drift which reoccur with Jupiter's rotation period and (3) periodic non-arc like radio features [1, 2]. These bursts are typically detected during several Jupiter rotations in decametric frequency range from 4 MHz to 12 - 16 MHz between 300° and 60° of CML. We present simultaneous observations of the periodic non-Io controlled DAM performed by the WAVES radio experiment onboard the two STEREO spacecraft and the groundbased radio telescope URAN-2 (Poltava, Ukraine) operated in the decametric frequency range. URAN-2 with an effective area of about 30000 m2 consists of 512 broadband crossed dipoles and equipped with the high performance digital radio spectrometer with polarization measurement capability. During the observation campaign Sep., 2012 - Apr., 2013 URAN-2 recorded a large amount of Jovian DAM events with the high time-frequency resolution (4 kHz - 100 ms) in a frequency range 8-32 MHz. In the same time the two spatially separated STEREO spacecraft was able to observe DAM in the frequency range up to 16 MHz. The first analysis of the acquired stereoscopic observations is presented. In particular, we show one episode when the periodic non-arc DAM was recorded together with long lasting Jovian narrow band (NB) emissions. These NB emission was observed at the high frequency cutoff of DAM and can be interpreted as propagation of the decametric radiation in the Jovian ionosphere [3]. We discuss the possible relations between the observed NB events and the periodic non-Io controlled Jovian decametric radio emission.

  3. An event observed by the Mont Blanc underground neutrino detector on February 23, 1987

    NASA Astrophysics Data System (ADS)

    Dadykin, V. L.; Zatsepin, G. T.; Korchaguin, V. B.; Korchaguin, P. V.; Malgin, A. S.; Ryazhskaya, O. G.; Ryassny, V. G.; Talochkin, V. P.; Khalchukov, F. F.; Yakushev, V. F.; Aglietta, M.; Badino, G.; Bologna, G.; Vernetto, S.; Galeotti, P.; Castagnoli, C.; Castellina, A.; Saavedra, O.; Trinchero, G.; Fulgione, W.

    1988-02-01

    An analysis is made of the event detected by the Soviet-Italian neutrino scintillation detector (LSD) beneath Mont Blanc on Februrary 23, 1987 at 2:52:37 UT. Corrected energies of the pulses of the event have been determined along with the probability of event imitiation by the background. The LSD data are compared with Kamiokande and IMB data. The possibility that the observed event may be connected with the explosion of SN 1987A is examined.

  4. OMI Tropospheric NO2 from Lightning in Observed Convective Events

    NASA Technical Reports Server (NTRS)

    Pickering, Kenneth; Bucsela, Eric; Kucsera, Tom; Pan, Laura; Davis, Chris; Gleason, James; Levelt, Pieternel

    2007-01-01

    Lightning is responsible for an estimated 15 percent of total NO emissions, and is one of the most prominent sources in the upper troposphere. In this study, we present evidence of lightning-generated NO2 (LNO2) using data from the Ozone Monitoring Instrument (OMI), which has observed tropospheric NO2 since its launch in 2004. Although LNO2 has been also reported in previous satellite studies from the Global Ozone Monitoring Experiment (GOME) and SCIAMACHY, OMI is better suited for such measurements by virtue of its higher spatial resolution and daily global coverage. We will present data clearly showing the LNO2 signal in the OMI tropospheric NO2 product on two days over and downwind of specific convective systems in the US Midwest. Gridded monthly mean tropospheric NO 2 data are subtracted from the daily gridded data to obtain the presumed LNO2 signal. Observed cloud-to-ground (CG) lightning flashes from the National Lightning Detection Network (NLDN) were counted along middle and upper tropospheric back trajectories that were run from the regions containing the LNO2 signal. A vertically-weighted average number of upwind CG flashes was obtained using a profile of LNO(x) mass obtained from a series of midlatitude cloud-resolved storm chemistry simulations. The number of CG flashes was scaled up to total flashes (intracloud (IC) flashes plus CG) using a climatological IC/CG ratio. The number of moles of LNO(x) in the region considered was estimated by assuming that LNO2 is 30 percent of LNO(x). This value was divided by the number of upwind flashes to obtain an average estimate of the number of moles produced per flash. Results yield values in the range obtained through other estimation techniques (e.g., aircraft measurements, models). We will also present a similar analysis over northern Australia during the SCOUT-O3/ACTIVE field campaigns in November and December 2005, in which we will compare the OMI LNOx signals with aircraft observations from the storm anvils.

  5. Modulation of Young Injection Events at Saturn at the Rotation Period of Perturbations in the Winter Hemisphere: A Proposed Mechanism

    NASA Astrophysics Data System (ADS)

    Kivelson, M.; Jia, X.

    2014-12-01

    Non-dispersive or "young" plasma injection events observed near midnight at Saturn are modulated at the period associated with the winter hemisphere [Kennelly et al., 2013]. Most other periodic dynamics of the magnetosphere are dominated by responses at the period of the summer hemisphere. The anomalous periodicity of plasma injection has not been explained. We present a theoretical explanation of ionospheric control, noting (as do Kennelly et al.) that the growth rate of the interchange instability is controlled by ionospheric conductance although the instability condition does not involve the ionosphere [Southwood and Kivelson, 1989]. The motion of the foot of a flux tube through the ionosphere is impeded by high conductance (line tying). Low conductance allows slippage and rapid growth of the instability. When the ionospheres have very different conductances, flux tube motion may be asymmetrical, with rapid displacement occurring only in the low conductance, winter hemisphere. A rotationally modulated low conductivity in that hemisphere would impose periodicity on injections. Pre-equinox (2009) at Saturn, the northern hemisphere conductance was low but probably varied with rotation phase because of the pattern of field-aligned currents (FACs) thought to rotate about the pole at the northern period, TN[Jia and Kivelson, 2012]. The upward current region in the ionosphere was probably more highly ionized than the downward current region because of electron precipitation. Two predictions follow. (1) The probability of an injection event in the midnight sector should maximize when the downward FAC in the winter hemisphere (conductivity minimum) has rotated into the midnight sector and (2) in northern winter, the tilt of the interchanging flux tube should produce positive radial field perturbations at and above the equator for inward-moving flux tubes and negative radial field perturbations for outward-moving flux tubes. Tests of these predictions will be reported

  6. Freja observations of multiple injection events in cusp

    NASA Astrophysics Data System (ADS)

    Norberg, O.; Yamauchi, M.; Eliasson, L.; Lundin, R.

    The TICS (Three-dimensional Ion Composition Spectrometer) instrument on board the Freja satellite provides particle data with high spatial, temporal, spectral, and mass resolution. The Freja orbit (inclination 63°) is suitable for studies of the cusp since the satellite traverses this region longitudinally when the cusp is located lower than 75° geomagnetic latitude, i.e. when the interplanetary magnetic field (IMF) points southward. The satellite traverses the dayside polar region during two weeks every 100 days due to orbit precession, and nearly 50 cusp traversals were recorded during the first year of operation. Both multiple injections and single injections are clearly identified and distinguished, the former being more frequently observed than the latter. Freja has also resolved overlapping injections (special cases of multiple injections), for the first time at low altitudes.

  7. Uni- and crossmodal refractory period effects of event-related potentials provide insights into the development of multisensory processing

    PubMed Central

    Johannsen, Jessika; Röder, Brigitte

    2014-01-01

    To assess uni- and multisensory development in humans, uni- and crossmodal event-related potential (ERP) refractory period effects were investigated. Forty-one children from 4 to 12 years of age and 15 young adults performed a bimodal oddball task with frequent and rare visual and auditory stimuli presented with two different interstimulus intervals (ISIs). Amplitudes of the visual and auditory ERPs were modulated as a function of the age of the participants, the modality of the preceding stimulus (same vs. different) and the preceding ISI (1000 or 2000 ms). While unimodal refractory period effects were observed in all age groups, crossmodal refractory period effects differed among age groups. Early crossmodal interactions (<150 ms) existing in the youngest age group (4–6 years) disappeared, while later crossmodal interactions (>150 ms) emerged with a parietal topography in older children and adults. Our results are compatible with the intersensory differentiation and the multisensory perceptual narrowing approach of multisensory development. Moreover, our data suggest that uni- and multisensory development run in parallel with unimodal development leading. PMID:25120454

  8. Observations and predictions of eclipse times by astronomers in the pre-telescopic period.

    NASA Astrophysics Data System (ADS)

    Steele, J. M.

    Eclipses of the Sun and Moon are among the most impressive of celestial events. It is therefore unsurprising that they have played an important role in the astronomy and astrology of most early cultures. Many hundreds of references to eclipses are found in the writings of the chroniclers and astronomers of the pre-telescopic world. In particular, the astronomers of Babylon, Ancient Greece, the Islamic Near East. Later Medieval and Renaissance Europe, China, and Japan, recorded a large number of observations and predictions of the time of an eclipse. The present study contains an extensive compilation of all known timed reports of eclipse observations and predictions made by astronomers in the pre-telescopic period. By performing a basic analysis of the recorded times, it has been possible to trace the gradual development of the techniques used by the astronomers to observe and predict eclipses. In order to conduct this analysis, it has been necessary to investigate a number of other problems including the dating of damaged observational accounts, the units of time used by the early astronomers, and the methods by which the Babylonians predicted eclipses. Many of these questions have not previously been answered. Therefore, the results of this study provide important information regarding the astronomies of these early cultures.

  9. A Phreatic Explosion Model Inferred from a Very Long Period Seismic Event at Mayon Volcano, Philippines

    NASA Astrophysics Data System (ADS)

    Maeda, Y.; Kumagai, H.; Lacson, R. _Jr., Jr.; Figueroa, M. S., II; Yamashina, T.; Ohkura, T.; Baloloy, A. V.

    2014-12-01

    Mayon is one of the most active volcanoes in the Philippines with 49 known historical eruptions from 1616 to 2010. A phreatic explosion took place at Mayon on 7 May 2013 that killed five climbers. During the explosion, a very long period seismic event with a peak frequency of 0.4 Hz was recorded by three broadband seismometers. Our frequency-domain waveform inversion solution of the event in the frequency range 0.1-0.6 Hz is consistent with a subhorizontal tensile crack and a vertical single force at a shallow location beneath the summit crater. The source time functions obtained by the waveform inversion are band-passed forms (filtered source time functions; FSTFs), which may be distorted from the source time functions without filters (deconvolved forms of the source time functions; DSTFs). To estimate the DSTFs, we assumed several simple trial functions as candidates for the DSTFs and applied a band-pass filter of 0.1-0.6 Hz to them. A comparison with the FSTFs suggested that the DSTFs of both the crack and single force are better approximated by an impulse-type function than by a step-type function. The estimated DSTF of the crack showed inflation followed by deflation, whereas that of the single force suggested a downward impulse. The inflation of the crack may be attributed to boiling of underground water and its deflation can be attributed to discharge of water vapor. The downward force may be understood as the counterforce of the explosion. Our results suggest that only a portion of the crack wall was destroyed by the explosion. We present a model of repeated explosions in which an explosion can occur once the fragmented portion of the crack is sealed by precipitation of clay minerals or hydrothermal secondary deposits. This model may explain the absence of clear precursory signals before the 2013 explosion.

  10. The excitation and characteristic frequency of the long-period volcanic event: An approach based on an inhomogeneous autoregressive model of a linear dynamic system

    USGS Publications Warehouse

    Nakano, M.; Kumagai, H.; Kumazawa, M.; Yamaoka, K.; Chouet, B.A.

    1998-01-01

    We present a method to quantify the source excitation function and characteristic frequencies of long-period volcanic events. The method is based on an inhomogeneous autoregressive (AR) model of a linear dynamic system, in which the excitation is assumed to be a time-localized function applied at the beginning of the event. The tail of an exponentially decaying harmonic waveform is used to determine the characteristic complex frequencies of the event by the Sompi method. The excitation function is then derived by operating an AR filter constructed from the characteristic frequencies to the entire seismogram of the event, including the inhomogeneous part of the signal. We apply this method to three long-period events at Kusatsu-Shirane Volcano, central Japan, whose waveforms display simple decaying monochromatic oscillations except for the beginning of the events. We recover time-localized excitation functions lasting roughly 1 s at the start of each event and find that the estimated functions are very similar to each other at all the stations of the seismic network for each event. The phases of the characteristic oscillations referred to the estimated excitation function fall within a narrow range for almost all the stations. These results strongly suggest that the excitation and mode of oscillation are both dominated by volumetric change components. Each excitation function starts with a pronounced dilatation consistent with a sudden deflation of the volumetric source which may be interpreted in terms of a choked-flow transport mechanism. The frequency and Q of the characteristic oscillation both display a temporal evolution from event to event. Assuming a crack filled with bubbly water as seismic source for these events, we apply the Van Wijngaarden-Papanicolaou model to estimate the acoustic properties of the bubbly liquid and find that the observed changes in the frequencies and Q are consistently explained by a temporal change in the radii of the bubbles

  11. Fortuitous Plasma Observations During the Mars Atmospheric "Plume" Event of March-April 2012

    NASA Astrophysics Data System (ADS)

    Andrews, D. J.; Barbash, S.; Edberg, N. J. T.; Gurnett, D. A.; Hall, B. E. S.; Lester, M.; Morgan, D. D.; Opgenoorth, H. J.; Ramstadt, R.; Sanchez-Cano, B.; Way, M.; Witasse, O. G.

    2015-12-01

    We present initial analysis and conclusions from plasma observations made during the reported `Mars Dust plume event' of March - April 2012.During this period, multiple independent amateur observers detected a localized, high-altitude feature over the Martian terminator [Sanchez-Lavega et al., Nature, 2015, doi:10.1038/nature14162], the explanation for which remains incomplete. The brightness of the feature in visible light is too extreme for auroral emissions to explain, despite its occurrence at a location where these have been previously reported. Likewise, the (projected) altitude of the feature is significantly too high to allow for the local formation of clouds.Fortuitously, the orbit of ESA's Mars Express allowed the measurement of ionospheric plasma density and solar wind parameters over the precise location of the plume sighting at multiple points during this interval.Based on these observations, we tentatively conclude that the formation and/or transport of this plume to the altitudes where it was observed was in part the result of a large Coronal Mass Ejection encountering the Martian system.However, while measurements of ionospheric plasma density at the corresponding altitudes indicate a disturbed structure, this is not a-typical of this location over Mars. Finally, we briefly discuss some possible mechanisms that may lead to the formation of this plume.

  12. Fortuitous Plasma Observations During the Mars Atmospheric "Plume" Event of March-April 2012

    NASA Astrophysics Data System (ADS)

    Andrews, David; Barabash, Stas; Edberg, Niklas; Gurnett, Donald; Hall, Ben; Holmström, Mats; Lester, Mark; Opgenoorth, Hermann; Ramstad, Robin; Sanchez-Cano, Beatriz; Way, Michael; Witasse, Olivier; Morgan, David

    2016-04-01

    We present initial analysis and conclusions from plasma observations made during the reported `Mars Dust plume event' of March - April 2012.During this period, multiple independent amateur observers detected a localized, high-altitude feature over the Martian terminator [Sanchez-Lavega et al., Nature, 2015, doi:10.1038/nature14162], the explanation for which remains incomplete. The brightness of the feature in visible light is too extreme for auroral emissions to explain, despite its occurrence at a location where these have been previously reported. Likewise, the (projected) altitude of the feature is significantly too high to allow for the local formation of clouds. Fortuitously, the orbit of ESA's Mars Express allowed the measurement of ionospheric plasma density and solar wind parameters over the precise location of the plume sighting at multiple points during this interval. Based on these observations, we tentatively conclude that the formation and/or transport of this plume to the altitudes where it was observed was in part the result of a large Coronal Mass Ejection encountering the Martian system. However, while measurements of ionospheric plasma density at the corresponding altitudes indicate a disturbed structure, this is not a-typical of this location over Mars. Finally, we briefly discuss some possible mechanisms that may lead to the formation of this plume.

  13. Transition Region and Chromospheric Signatures of Impulsive Heating Events. I. Observations

    NASA Astrophysics Data System (ADS)

    Warren, Harry P.; Reep, Jeffrey W.; Crump, Nicholas A.; Simões, Paulo J. A.

    2016-09-01

    We exploit the high spatial resolution and high cadence of the Interface Region Imaging Spectrograph (IRIS) to investigate the response of the transition region and chromosphere to energy deposition during a small flare. Simultaneous observations from the Reuven Ramaty High Energy Solar Spectroscopic Imager provide constraints on the energetic electrons precipitating into the flare footpoints, while observations of the X-Ray Telescope, Atmospheric Imaging Assembly, and Extreme Ultraviolet Imaging Spectrometer (EIS) allow us to measure the temperatures and emission measures from the resulting flare loops. We find clear evidence for heating over an extended period on the spatial scale of a single IRIS pixel. During the impulsive phase of this event, the intensities in each pixel for the Si iv 1402.770 Å, C ii 1334.535 Å, Mg ii 2796.354 Å, and O i 1355.598 Å emission lines are characterized by numerous small-scale bursts typically lasting 60 s or less. Redshifts are observed in Si iv, C ii, and Mg ii during the impulsive phase. Mg ii shows redshifts during the bursts and stationary emission at other times. The Si iv and C ii profiles, in contrast, are observed to be redshifted at all times during the impulsive phase. These persistent redshifts are a challenge for one-dimensional hydrodynamic models, which predict only short-duration downflows in response to impulsive heating. We conjecture that energy is being released on many small-scale filaments with a power-law distribution of heating rates.

  14. Source Mechanism of Tiny Long-Period Events at Mount St. Helens in July 2005

    NASA Astrophysics Data System (ADS)

    Matoza, R. S.; Chouet, B. A.; Dawson, P. B.; Shearer, P. M.; Haney, M. M.; Waite, G. P.; Moran, S. C.; Mikesell, T. D.

    2015-12-01

    Long-period (LP, 0.5-5 Hz) seismicity is a recognized signature of unrest and eruption at volcanoes worldwide. The characteristic seismicity during the sustained dome-building phase of the 2004-2008 eruption of Mount St. Helens (MSH), USA was cyclic LP "drumbeating". However, accompanying the LP drumbeating was a near-continuous, randomly occurring series of tiny LP seismic events (LP "subevents"), which may hold important additional information on the mechanism of seismogenesis at restless volcanoes. We employ template matching, phase-weighted stacking, and full-waveform inversion to image the source mechanism of one multiplet of these LP subevents at MSH in July 2005. We apply network-based template matching to 8 days of continuous velocity waveform data from 29 June to 7 July 2005. We stack waveforms for high-quality triggers at each station and component, using a combination of linear and phase-weighted stacking to produce clean stacks for use in waveform inversion. The derived source mechanism points to the volumetric oscillation (~10 m3) of a subhorizontal crack located at shallow depth (~30 m) in an area to the south of Crater Glacier in the southern portion of the breached MSH crater. A possible excitation mechanism is the sudden condensation of metastable steam from a shallow pressurized hydrothermal system as it encounters cool meteoric water in the outer parts of the edifice.

  15. Damaging events along roads during bad weather periods: a case study in Calabria (Italy)

    NASA Astrophysics Data System (ADS)

    Petrucci, O.; Pasqua, A. A.

    2012-02-01

    The study focuses on circumstances that affect people during periods of bad weather conditions characterised by winds, rainfall, landslides, flooding, and storm surges. A methodological approach and its application to a study area in southern Italy are presented here. A 10-yr database was generated by mining data from a newspaper. Damaging agents were sorted into five types: flood, urban flooding, landslide, wind, and storm surge. Damage to people occurred in 126 cases, causing 13 victims, 129 injured and about 782 people involved but not injured. For cases of floods, urban flooding and landslides, the analysis does not highlight straightforward relationships between rainfall and damage to people, even if the events showed different features according to the months of occurrence. The events occurring between May and October were characterised by concentrated and intense rainfall, and between May and July, the highest values of hourly (103 mm on the average) and monthly rainfall (114 mm on the average) were recorded. Urban flooding and flash floods were the most common damaging agents: injured, involved people and more rarely, cases with victims were reported. Between November and April, the highest number of events was recorded. Rainfall presented longer durations and hourly and sub-hourly rainfall were lower than those recorded between May and October. Landslides were the most frequent damaging agents but the highest number of cases with victims, which occurred between November and January, were mainly related to floods and urban flooding. Motorists represent the totality of the victims; 84% of the people were injured and the whole of people involved. All victims were men, and the average age was 43 yr. The primary cause of death was drowning caused by floods, and the second was trauma suffered in car accidents caused by urban flooding. The high number of motorists rescued in submerged cars reveals an underestimation of danger in the case of floods, often

  16. Short period airglow temperature and emission rate oscillations in the high Arctic MLT region during stratospheric warming events

    NASA Astrophysics Data System (ADS)

    Lederman, J. I.

    2015-12-01

    The airglow is a photochemical glow in the upper atmosphere that occurs in thin layers corresponding to different chemical processes. The O2 Atmospheric airglow layer exists at about 94 km altitude and the hydroxyl layer at about 87 km. The intensity of the light gives information about the concentration of atomic oxygen there, while the shape of the spectrum gives accurate values of the temperature. In this investigation, these are measured above Eureka in the Canadian Arctic (80N, 86W) using an instrument called SATI (Spectral Airglow Temperature Imager). The optical data are employed to characterize short period oscillations in rotational temperatures and integral emission rates of OH (6,2) Meinel and O2 (0,1) Atm. bands during a stratospheric warming event from January 2015. In this presentation, SATI observations coupled with wind radiosonde data at Eureka and the ECMWF model are used to compare the January 2015 warming with the major stratospheric warming event of January 2009, thereby providing a window into high frequency atmospheric wave dynamics at play between altitudes of 20 km - 100 km.

  17. The importance of weather and short period climate events in driving projected high sea level extremes along the California Coast

    NASA Astrophysics Data System (ADS)

    Cayan, D. R.

    2012-12-01

    Relative sea level rise along southern and central California over the last century has been observed at nearly 2mm/year, similar to estimated global rates. Sea level rise scenarios over the next several decades vary widely, but recent projections tend to be much larger than the historical rate. However, even if sea level rise is amplified considerably, weather and short period climate effects will play a key role. Historically, the most severe high sea level conditions have arisen when North Pacific storms and ENSO conditions have coincided with high astronomical tides. In many instances, high wind-generated waves exacerbate high sea level events, and in some settings, heavy fresh water runoff also contributes. A model which includes these mechanisms, driven by factors derived from a set of global climate model simulations, provides an ensemble of hourly sea level projections that demonstrate that the occurrence high sea level events along the California coast will continue to be dominated by high tide and large storm occurrences during the next several decades, although their amplitude and duration will increase progressively. In the Sacramento/San Joaquin Delta estuary, fresh water flooding that sometimes accompanies large winter storms will compound high oceanic sea level impacts.

  18. The results of the 2015 campaign of observation of mutual events of the Jovian satellites

    NASA Astrophysics Data System (ADS)

    Arlot, J. E.; Saquet, E.; Emelianov, N.

    2015-10-01

    From September 2014 to June 2015 mutual events of the Galilean satellites occurred around the Jovian equinox occurring on February 6, 2015. The observations of these events provide very accurate information on the relative astrometry of the satellites. Previous campaign of observations have shown the high interest of such observations now performed mainly by amateur astronomers: the Galilean satellites are bright and the magnitude drop during these events is easily observable. The 2014- 2015 campaign is especially favorable because of the maximum of events which will occur during the opposition between the Sun and Jupiter. More, eclipses of Thebe and Amalthea by the Galileans have been observed. Note that the positive declination of Jupiter made the observations easier in the Northern hemisphere where, unfortunately, the meteorological conditions were bad.

  19. Plasma observations during the Mars atmospheric "plume" event of March-April 2012

    NASA Astrophysics Data System (ADS)

    Andrews, D. J.; Barabash, S.; Edberg, N. J. T.; Gurnett, D. A.; Hall, B. E. S.; Holmström, M.; Lester, M.; Morgan, D. D.; Opgenoorth, H. J.; Ramstad, R.; Sanchez-Cano, B.; Way, M.; Witasse, O.

    2016-04-01

    We present initial analyses and conclusions from plasma observations made during the reported "Mars plume event" of March-April 2012. During this period, multiple independent amateur observers detected a localized, high-altitude "plume" over the Martian dawn terminator, the cause of which remains to be explained. The estimated brightness of the plume exceeds that expected for auroral emissions, and its projected altitude greatly exceeds that at which clouds are expected to form. We report on in situ measurements of ionospheric plasma density and solar wind parameters throughout this interval made by Mars Express, obtained over the same surface region but at the opposing terminator. Measurements in the ionosphere at the corresponding location frequently show a disturbed structure, though this is not atypical for such regions with intense crustal magnetic fields. We tentatively conclude that the formation and/or transport of this plume to the altitudes where it was observed could be due in part to the result of a large interplanetary coronal mass ejection (ICME) encountering the Martian system. Interestingly, we note that the only similar plume detection in May 1997 may also have been associated with a large ICME impact at Mars.

  20. The French component of the FENNEC Saharan Climate project 2011 Special Observing Period

    NASA Astrophysics Data System (ADS)

    Flamant, C.; Chaboureau, J.-P.; Kocha, C.; Lavaysse, C.; Schepanski, K.; Chazette, P.; Bock, O.; Marticorena, B.; Tulet, P.; Pelon, J.; Marnas, F.; Mokhtari, M.; Lafore, J.-P.; Roehrig, R.; Koulali Idrissi, A.; Tsamalis, C.; Chedin, A.

    2012-04-01

    The central Sahara has one of the most extreme climates on Earth. During the northern summer months, a large low pressure system caused by intense solar heating develops over a huge, largely uninhabited expanse of northern Mali, southern Algeria and eastern Mauritania. This Saharan heat low plays a pivotal role in the West African Monsoon. Based on this, the interested French, British and German communities have decided to propose the FENNEC project which aims at (i) characterizing the Saharan atmospheric boundary layer, (ii) evaluating its representation in regional and global models, and (iii) improving "aerosol" products issued from space-borne observations. A key element of this programme was the organization of an international field campaign in June 2011 over the Saharan heat low region, which will include both ground-based and airborne detachments. The Special Observing Period component of FENNEC-France included the implementation of the SAFIRE Falcon 20 to conduct research on the atmospheric boundary layer and the dust cycle of the Sahara, the installation of a remote sensing station in southern Spain, equipped with a backscatter lidar and a sunphotometer, to study the transport of desert dust to Europe, as well as a couple of GPS stations installed in southern Morocco to investigate the moisture inflow from the Atlantic Ocean into the Sahara. For the first time, the ALADIN and AROME models (5 and 24 km grid spacing, respectively) have been implemented operationally to provide forecasts of dust events over the Sahara and parts of the Sahel in June 2011 to assist in planning for airborne operations. This effort was complemented by the forecasts made with the Meso-NH model (5 and 20 km resolution). During the SOP period, the ground-based, airborne and space-borne observations have documented the evolution of dynamic properties of thermodynamic and the atmospheric boundary layer Saharan Africa (Mauritania and Mali) during the installation phase of the Saharan

  1. Modeling Pluto-Charon Mutual Events. 2; CCD Observations with the 60 in. Telescope at Palomar Mountain

    NASA Technical Reports Server (NTRS)

    Buratti, B. J.; Dunbar, R. S.; Tedesco, E. F.; Gibson, J.; Marcialis, R. L.; Wong, F.; Bennett, S.; Dobrovolskis, A.

    1995-01-01

    We present observations of 15 Pluto-Charon mutual events which were obtained with the 60 in. telescope at Palomar Mountain Observatory. A CCD camera and Johnson V filter were used for the observations, except for one event that was observed with a Johnson B filter, and another event that was observed with a Gunn R filter. We observed two events in their entirety, and three pairs of complementary mutual occultation-transit events.

  2. Long-Period seismic events at Ubinas Volcano (Peru): their implications and potentiality as monitoring tool

    NASA Astrophysics Data System (ADS)

    Zandomeneghi, D.; Inza, A.; Metaxian, J.-P.; Macedo, O.

    2012-04-01

    Ubinas volcano (Southern Peru) is an active andesitic stratovolcano, located 75 km East of Arequipa City, with an average occurrence of 6-7 eruptions per century and persistent fumarolic and phreatic activity. The most recent eruption, accompanied by explosions and by the extrusion of a lava dome, started on March 2006 with an increase of seismicity and observed fumarole occurrence followed in April by more intense explosions, recorded until May 2009. To monitor the volcanic activity, the Geophysical Institute of Peru and the Institut de Recherche pour le Développment (France), built up a seismic network around the volcano, installing 4 permanent stations and deploying 8 supplementary temporary broadband seismometers. In addition, in the period May to July 2009, a seismic experiment was carried out on the volcano flanks with 2 cross-shaped dense antennas with broadband seismometers. As the seismic activity was characterized by recurring low-frequency waveforms, we identify their pattern of occurrence through waveform cross-correlation technique, with respect to major eruptive phases and other observations (as volcano ground deformation from tiltmeters, volcanic product composition, etc). Once established their likely association with the eruptive sequence, we utilize both local network and dense-array data and analyze their location, changes in location, spectral content variations and possible physical explanation. The final aim is to introduce this kind of analysis as quantitative tool to understand ongoing eruptive phases at andesitic volcanoes and possibly to forecast magma/fluid significant movements.

  3. Observation of a Short Period Quasi-periodic Pulsation in Solar X-Ray, Microwave, and EUV Emissions

    NASA Astrophysics Data System (ADS)

    Kumar, Pankaj; Nakariakov, Valery M.; Cho, Kyung-Suk

    2017-02-01

    This paper presents the multiwavelength analysis of a 13 s quasi-periodic pulsation (QPP) observed in hard X-ray (12–300 keV) and microwave (4.9–34 GHz) emissions during a C-class flare that occurred on 2015 September 21. Atmospheric Image Assembly (AIA) 304 and 171 Å images show an emerging loop/flux tube (L1) moving radially outward, which interacts with the preexisting structures within the active region (AR). The QPP was observed during the expansion of and rising motion of L1. The Nobeyama Radioheliograph microwave images in 17/34 GHz channels reveal a single radio source that was co-spatial with a neighboring loop (L2). In addition, using AIA 304 Å images, we detected intensity oscillations in the legs of L2 with a period of about 26 s. A similar oscillation period was observed in the GOES soft X-ray flux derivative. This oscillation period seems to increase with time. We suggest that the observed QPP is most likely generated by the interaction between L2 and L3 observed in the AIA hot channels (131 and 94 Å). The merging speed of loops L2 and L3 was ∼35 km s‑1. L1 was destroyed possibly by its interaction with preexisting structures in the AR, and produced a cool jet with the speed of ∼106–118 km s‑1 associated with a narrow CME (∼770 km s‑1). Another mechanism of the QPP in terms of a sausage oscillation of the loop (L2) is also possible.

  4. Identification of Atmospheric Events Using Data Mining and Observations From an Atmospheric Monitoring Cyberinfrastructure

    NASA Astrophysics Data System (ADS)

    Verhoef, B. D.; Parikh, N.; Fernando, H. J.; Liu, H.; Montenegro, L.

    2006-05-01

    As part of the National Science Foundation's Collaborative Large-scale Engineering Analysis Network for Environmental Research (CLEANER) initiative researchers at Arizona State University in connection with the Arizona Department of Environmental Quality have established an atmospheric monitoring cyberinfrastructure. One of the cyberinfrastructure's valuable constituents is the use of data mining algorithms to identify atmospheric events. Results show that the algorithms have the ability to accurately identify events of interest using routine observations. Before the data mining algorithms are used to identify specific atmospheric events they must be trained and tested. They are first trained using historical data. Events are carefully identified within historical data and used by the algorithms in learning to recognize data patterns. For atmospheric events the patterns include changes in wind speed, wind direction, temperature, barometric pressure, and relative humidity. Training is conducted for each instrument being used. Once training of the algorithm is completed it is tested against more recent observations to check its accuracy. In the present case, the atmospheric events being analyzed are evening transition fronts -- mixing events that initiate katabatic flow down gradual mountain slopes. Observations received via the cyberinfrastructure are scanned for evidence of the event using the data mining algorithms and then labeled accordingly. A good agreement is shown to exist between actual event occurrence and identification of events through data mining. The labeled data are assisting researchers in identifying the events, thus reducing the time required for data analysis. Eventually, this will allow events with complicated signatures to be automatically identified. Data mining as a means of identifying atmospheric phenomena will one day assist weather prediction models in the automation of severe weather warning systems as well as lead to the design of more

  5. Neutron Monitor Observations and Space Weather, 1. Automatically Search of Great Solar Energetic Particle Event Beginning.

    NASA Astrophysics Data System (ADS)

    Dorman, L. I.; Pustil'Nik, L. A.; Sternlieb, A.; Zukerman, I. G.

    It is well known that in periods of great SEP fluxes of energetic particles can be so big that memory of computers and other electronics in space may be destroyed, satellites and spacecrafts became dead: according to NOAA Space Weather Scales are danger- ous Solar Radiation Storms S5-extreme (flux level of particles with energy > 10 MeV more than 10^5), S4-severe (flux more than 10^4) and S3-strong (flux more than 10^3). In these periods is necessary to switch off some part of electronics for few hours to protect computer memories. These periods are also dangerous for astronauts on space- ships, and passengers and crew in commercial jets (especially during S5 storms). The problem is how to forecast exactly these dangerous phenomena. We show that exact forecast can be made by using high-energy particles (few GeV/nucleon and higher) which transportation from the Sun is characterized by much bigger diffusion coeffi- cient than for small and middle energy particles. Therefore high energy particles came from the Sun much more early (8-20 minutes after acceleration and escaping into so- lar wind) than main part of smaller energy particles caused dangerous situation for electronics (about 30-60 minutes later). We describe here principles and experience of automatically working of program "FEP-Search". The positive result which shows the exact beginning of FEP event on the Emilio Segre' Observatory (2025 m above sea level, Rc=10.8 GV), is determined now automatically by simultaneously increas- ing on 2.5 St. Dev. in two sections of neutron supermonitor. The next 1-min data the program "FEP-Search" uses for checking that the observed increase reflects the begin- ning of real great FEP or not. If yes, automatically starts to work on line the programs "FEP-Research".

  6. Periodization

    PubMed Central

    Lorenz, Daniel S.; Reiman, Michael P.; Walker, John C.

    2010-01-01

    Background: Clinicians are constantly faced with the challenge of designing training programs for injured and noninjured athletes that maximize healing and optimize performance. Periodization is a concept of systematic progression—that is, resistance training programs that follow predictable patterns of change in training variables. The strength training literature is abundant with studies comparing periodization schemes on uninjured, trained, and untrained athletes. The rehabilitation literature, however, is scarce with information about how to optimally design resistance training programs based on periodization principles for injured athletes. The purpose of this review is to discuss relevant training variables and methods of periodization, as well as periodization program outcomes. A secondary purpose is to provide an anecdotal framework regarding implementation of periodization principles into rehabilitation programs. Evidence Acquisition: A Medline search from 1979 to 2009 was implemented with the keywords periodization, strength training, rehabilitation, endurance, power, hypertrophy, and resistance training with the Boolean term AND in all possible combinations in the English language. Each author also undertook independent hand searching of article references used in this review. Results: Based on the studies researched, periodized strength training regimens demonstrate improved outcomes as compared to nonperiodized programs. Conclusions: Despite the evidence in the strength training literature supporting periodization programs, there is a considerable lack of data in the rehabilitation literature about program design and successful implementation of periodization into rehabilitation programs. PMID:23015982

  7. Evaluating Heating and Moisture Variability Associated with MJO Events in a Low-Dimension Dynamic Model with Observations and Reanalyses

    NASA Astrophysics Data System (ADS)

    Stachnik, J. P.; Waliser, D. E.; Majda, A.; Stechmann, S.

    2013-12-01

    The Madden-Julian Oscillation (MJO) is the leading mode of intraseasonal variability in the tropics. Despite its importance toward determining large-scale variability at both low-latitudes and the extratropics, MJO prediction often suffers from low skill regarding event initiation and its overall simulation remains a challenge in many global climate models (GCMs). The MJO 'skeleton' model, originally developed by Majda and Stechmann (2009), is a new low-order dynamic model that is capable of reproducing several salient features of the MJO despite its many simplifications relative to higher-order GCMs. Among their successes, the newest version of the skeleton model is able to reproduce the intermittent generation of MJO events, including organization into MJO wave trains that experience both growth and decay. This study presents an analysis of initiation events in the skeleton model. Higher-order features, such as the organization into wave trains, are examined herein and we document the simulated heating and moisture variability in the model compared to satellite-derived observations and reanalyses. We likewise present a composite analysis of the thermodynamic fields related to the initiation of primary and successive MJO events, as well as those precursor conditions leading to quiescent periods of the MJO. Time permitting, we also evaluate the multi-scale structures and other aspects of heating and moisture variability in the model (e.g., asymmetry between active and inactive periods) compared to distributions of integrated heating and moisture in Tropical Rainfall Measuring Mission (TRMM) observations and other datasets.

  8. Observations of Time Variable Magnitude Events of Phoebe, Ariel, and Titania

    NASA Astrophysics Data System (ADS)

    Miller, Charles; Chanover, N. J.; Holtzman, J. A.; Verbiscer, A. J.

    2007-10-01

    Visual observations of Saturn's moon Phoebe and Uranus' moons Ariel and Titania were made from the Apache Point Observatory (APO). Phoebe was observed with the APO 1 meter telescope over a two month period from 06 January to 04 March 2005, bracketing the zero-phase opposition on 13 January 2005. Phoebe was observed at Sun-Phoebe-Earth phase angles as low as 0.05 degrees on consecutive nights immediately before and after opposition in V, B, R, and I filters. Light curves of the opposition surge, the brightness increase that occurs as the phase angle drops below 0.10 degrees, are presented from this data. The data were processed using standard IRAF aperture photometry image processing techniques. The magnitude and duration of the opposition surge provide clues about the grain size of surface particles on Phoebe. Observations were also made of Uranian moons during mutual occultations in August 2007. Mutual satellite occultations are taking place throughout 2007 as Uranus passes through its equinox, which occurs once every 42 years. The timing and flux variation of satellite occultations provide a check on the accuracy of satellite orbital models. Light curves for Ariel and Titania in R and I filters as they are occulted by Umbriel are presented from data acquired with the APO 1 meter and 3.5 meter telescopes. Comparison is made to the predicted total flux reduction and event timing for each occultation as calculated by the Institut de Mecanique Celeste et de Calcul des Ephemerides (IMCCE) and implications of the results on determination of the relative orbital inclinations of Umbriel, Ariel, and Titania are discussed. This work was supported by an NMSU Space and Aerospace Research Cluster Graduate Fellowship .

  9. The number distribution of weak Explosive Events observed by SUMER/SoHO

    NASA Astrophysics Data System (ADS)

    Mendoza-Torres, J. E.

    2016-11-01

    Explosive Events (EEs) observed by SUMER on SoHO at the 1393.8 Å Si IV line are analyzed. We look for EEs to study their number distribution at low energies. Eight data sets taken in June 1996 in raster observations are used. In these observations a field on the solar disk is scanned several times during a period considerably longer than the typical timelife of an EE. To look for EE, we first identified the maxima and locations of spectral line increases. The maxima that took place at inner locations of the rastered fields were considered as possible EEs. From this sample, the cases where the spectral line underwent Doppler shifts at most ±3″ from the location of the maximum were considered EEs. After a selection, the region within 5″ of the event was ignored for 5 min either side of the EE in order to conclusively select a different maxima. Based on the analysis of the locations of EEs, it was seen that the more intense EEs tend to take place at given regions while at the intermediate regions the observed EEs are less intense. Therefore we refer to them as Regions of Enhanced Emission (REE) and Quiet Regions (QR), respectively. The width of the REE regions, as seen in North-South direction is about 10-30″. In this work, a total of 487 EEs are analyzed, 266 at REE and 221 at QR. Also, Histograms are made of the maxima of the amplitude of the spectral line during EEs at both REE and QR. At the Histogram for EEs at QR the number grows as the flux decreases with a slope of -1.8. For EEs at REE the Histogram has a maximum about 1 Watts m-2 sr-1 Å-1 with a high energy slope of about -1.6. These numbers are both below the value required to give an important input of energy for coronal heating, as analyzed in the case of microflares (Hudson, 1991). The averages of the maxima of EEs at each set for the REE and QR are computed. The scatter plot of the average values indicates that there is a linear relation between them and the maximum amplitudes of EEs at REE are

  10. Response of a hydrothermal system to magmatic heat inferred from temporal variations in the complex frequencies of long-period events at Kusatsu-Shirane Volcano, Japan

    USGS Publications Warehouse

    Nakano, M.; Kumagai, H.

    2005-01-01

    We investigate temporal variations in the complex frequencies (frequency and quality factor Q) of long-period (LP) events that occurred at Kusatsu-Shirane Volcano, central Japan. We analyze LP waveforms observed at this volcano in the period between 1988 and 1995, which covers a seismically active period between 1989 and 1993. Systematic temporal variations in the complex frequencies are observed in October-November 1989, July-October 1991, and September 1992-January 1993. We use acoustic properties of a crack filled with hydrothermal fluids to interpret the observed temporal variations in the complex frequencies. The temporal variations in October-November 1989 can be divided into two periods, which are explained by a gradual decrease and increase of a gas-volume fraction in a water-steam mixture in a crack, respectively. The temporal variations in July-October 1991 can be also divided into two periods. These variations in the first and second periods are similar to those observed in November 1989 and in September-November 1992, respectively, and are interpreted as drying of a water-steam mixture and misty gas in a crack, respectively. The repeated nature of the temporal variations observed in similar seasons between July and November suggests the existence of seasonality in the occurrence of LP events. This may be caused by a seasonally variable meteoritic water supply to a hydrothermal system, which may have been heated by the flux of volcanic gases from magma beneath this volcano. ?? 2005 Elsevier B.V. All rights reserved.

  11. Conjugate observations of a remarkable quasiperiodic event by the low-altitude DEMETER spacecraft and ground-based instruments

    NASA Astrophysics Data System (ADS)

    Němec, F.; Bezděková, B.; Manninen, J.; Parrot, M.; Santolík, O.; Hayosh, M.; Turunen, T.

    2016-09-01

    We present a detailed analysis of a long-lasting quasiperiodic (QP) event observed simultaneously by the low-altitude DEMETER spacecraft and on the ground by the instrumentation of the Sodankylä Geophysical Observatory, Finland. The event was observed on 26 February 2008. It lasted for several hours, and it was detected both in the Northern and Southern Hemispheres. The time intervals when the event was observed on board the satellite and/or on the ground provide us with an estimate of the event dimensions. When the event is detected simultaneously by the satellite and on the ground, the observed frequency-time structure is generally the same. However, the ratio of detected intensities varies significantly as a function of the spacecraft latitude, indicating the wave guiding along the plasmapause. Moreover, there is a delay as large as about 13 s between the times when individual QP elements are detected by the spacecraft and on the ground. This appears to be related to the azimuthal separation of the instruments, and it is highly relevant to the identification of a possible source mechanism. We suggest that it is due to an azimuthally propagating ULF wave which periodically modulates the azimuthally extended source region. Finally, we find that at the times when the intensity of the QP event suddenly increases, there is a distinct increase of the amplitude of Alfvénic ULF pulsations measured on the ground at high latitudes. This might indicate that the source region is located at L shells larger than about 7.1.

  12. Observations of a transient event in the subsolar magnetosheath during strongly northward IMF

    NASA Astrophysics Data System (ADS)

    Dias Silveira, M. V.; Sibeck, D. G.; Gonzalez, W. D.; Koga, D.

    2013-12-01

    We present multipoint THEMIS observation of a transient event in the subsolar magnetosheath on July 10, 2007. The event exhibits some features of a flux transfer event, such as a bipolar variation in the magnetic field component normal to the nominal magnetopause centered on a peak in the total magnetic field strength. Four THEMIS spacecraft were in the magnetosheath and one in the magnetosphere. Timing analysis and the absence of flow perturbation suggest that the event is a small scale structure (~0.12 Re in the direction of the flow) moving with the background magnetosheath flow. Despite the inferred small size of the event, THC and THD both observed large amplitude (~40 nT) bipolar magnetic field signatures normal to the nominal magnetopause. Nearby spacecraft THE (only 0.2 Re further outward in the Xgsm direction) observed no significant magnetic field perturbation. Neither did THB or THA, located further away in the magnetosheath and magnetosphere, respectively. During the event, the IMF was strongly northward (approximately 20nT), which does not favor subsolar magnetic reconnection. Inside the structure, the magnetic field briefly rotates 90° away from northward to dawnward. Ions stream antiparallel to the magnetic field in the magnetosheath, parallel to the magnetic field in the event.

  13. Validation of a 6-hour observation period for cocaine body stuffers

    PubMed Central

    Moreira, Maria; Buchanan, Jennie; Heard, Kennon

    2010-01-01

    Often, patients are brought in to the emergency room after ingesting large amounts of cocaine in an attempt to conceal it. This act is known as “body stuffing.” The observation period required to recognize potential toxic side effects in these patients is not well described in the literature. We sought to validate a treatment algorithm for asymptomatic cocaine body stuffers utilizing a 6-hour observation period by observing the clinical course of cocaine body stuffers over a 24-hour period. A retrospective chart review was performed on all patients evaluated for witnessed or suspected stuffing over two years utilizing a standardized protocol. 106 patients met final inclusion criteria as adult cocaine stuffers. No patients developed life-threatening symptoms and no patients died during observation. In our medical setting, stuffers could be discharged after a 6- hour observation period if there was either complete resolution or absence of clinical symptoms. PMID:20825819

  14. Station Set Residual: Event Classification Using Historical Distribution of Observing Stations

    NASA Astrophysics Data System (ADS)

    Procopio, Mike; Lewis, Jennifer; Young, Chris

    2010-05-01

    Analysts working at the International Data Centre in support of treaty monitoring through the Comprehensive Nuclear-Test-Ban Treaty Organization spend a significant amount of time reviewing hypothesized seismic events produced by an automatic processing system. When reviewing these events to determine their legitimacy, analysts take a variety of approaches that rely heavily on training and past experience. One method used by analysts to gauge the validity of an event involves examining the set of stations involved in the detection of an event. In particular, leveraging past experience, an analyst can say that an event located in a certain part of the world is expected to be detected by Stations A, B, and C. Implicit in this statement is that such an event would usually not be detected by Stations X, Y, or Z. For some well understood parts of the world, the absence of one or more "expected" stations—or the presence of one or more "unexpected" stations—is correlated with a hypothesized event's legitimacy and to its survival to the event bulletin. The primary objective of this research is to formalize and quantify the difference between the observed set of stations detecting some hypothesized event, versus the expected set of stations historically associated with detecting similar nearby events close in magnitude. This Station Set Residual can be quantified in many ways, some of which are correlated with the analysts' determination of whether or not the event is valid. We propose that this Station Set Residual score can be used to screen out certain classes of "false" events produced by automatic processing with a high degree of confidence, reducing the analyst burden. Moreover, we propose that the visualization of the historically expected distribution of detecting stations can be immediately useful as an analyst aid during their review process.

  15. Analysis of volcanic long-period events with quasi-static displacements from high-density seismological networks

    NASA Astrophysics Data System (ADS)

    Thun, Johannes; Bean, Christopher J.; Lokmer, Ivan

    2014-05-01

    Volcanic long-period (LP) events are commonly thought to be related to fluid pressure fluctuations in cracks and conduits beneath volcanoes. Sudden pressure fluctuations can generate slow/crack waves that can propagate along the fluid-solid boundaries between the fluid-filled source and the surrounding medium and thus sustain the resonance of the source. Although there are different variations of this model proposed in the literature, all of them include the source resonance sustained by crack waves. An alternative model (Bean et al., 2014) involves slow-slip fracturing of the shallow volcanic edifice. One of the difficulties in confirming or disproving these models lies in the limited frequency band in which moment tensor inversions of seismic LP signals are typically carried out in order to obtain acceptable solutions. In order to remove low-frequency noise and the high-frequency part of signals, which is difficult to model with numerical simulations, signals are band pass filtered in their most energetic frequency band before the inversions. However, this means we are only recovering a narrow band of the source-time history and any information outside this range is lost. Furthermore, as possible lower frequency components are less sensitive to the complex (and usually poorly known) velocity structure in the shallow edifice, they are particularly interesting for inversions. In this study we are investigating possibilities to include a broader frequency spectrum of the observed displacement signals into moment tensor inversions. In particular, we have observed quasi-static displacement steps for numerous LP events on different volcanoes. These are visible mostly on stations near the summit area and have amplitudes of a few micrometres. We are exploring possibilities to use these signals and distinguish them from noise (e.g. induced by tilting of the instrument). For our analysis we use a combination of numerical simulations and laboratory data to constrain the

  16. Oscillation Responses to an Extreme Weather Event from a Deep Moored Observing System

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Dimarco, S. F.; Stoessel, M. M.; Zhang, X.; Ingle, S.

    2011-12-01

    In June 2007 tropical Cyclone Gonu passed directly over an ocean observing system consisting of four, deep autonomous mooring stations along the 3000 m isobath in the northern Arabian Sea. Gonu was the largest cyclone known to have occurred in the Arabian Sea or to strike the Arabian Peninsula. The mooring system was designed by Lighthouse R & D Enterprises, Inc. and installed in cooperation with the Oman Ministry of Agriculture and Fisheries Wealth. The instruments on the moorings continuously recorded water velocities, temperature, conductivity, pressure, dissolved oxygen and turbidity at multiple depths and at hourly intervals during the storm. Near-inertial oscillations at all moorings from thermocline to seafloor are coincident with the arrival of Gonu. Sub-inertial oscillations with periods of 2-10 days are recorded at the post-storm relaxation stage of Gonu, primarily in the thermocline. These oscillations consist of warm, saline water masses, likely originating from the Persian Gulf. Prominent 12.7-day sub-inertial waves, measured at a station ~300 km offshore, are bottom-intensified and have characteristics of baroclinic, topographically-trapped waves. Theoretical results from a topographically-trapped wave model are in a good agreement with the observed 12.7-day waves. The wavelength of the 12.7-day waves is about 590 km calculated from the dispersion relationship. Further analysis suggests that a resonant standing wave is responsible for trapping the 12.7-day wave energy inside the Sea of Oman basin. The observational results reported here are the first measurements of deepwater responses to a tropical cyclone in the Sea of Oman/Arabian Sea. Our study demonstrates the utility of sustained monitoring for studying the impact of extreme weather events on the ocean.

  17. Observation on internal waves propagation during Land breeze event in Northern Tyrrhenian coast

    NASA Astrophysics Data System (ADS)

    Martellucci, Riccardo; Pierattini, Alberto; Paladini de Mendoza, Francesco; Melchiorri, Cristiano; Piermattei, Viviana; Ciampa, Francesco; Marcelli, Marco

    2015-04-01

    Internal wave propagation and water column mixing phenomena play an important role in many marine ecosystem coastal process. In Northern Tyrrhenian coast the experimental proposed approach is aimed to identify these type of oscillation in presence of breeze circulation. Along the Tyrrhenian coast summer period climate conditions allow the generations of high frequency land-sea breeze events. This local circulation, land-sea breeze indeed, may generate significant modifications of the sea waters physical parameters. Thay often appear as internal gravity waves especially in presence of stratified water and stable thermocline. Since the whole investigated process evolves on diurnal scale and in the space of a few miles the sampling plan was operated with a series of oceanographic surveys at 40 meters depth with 20 minutes interval one from another between 5 a.m. and 11 a.m. and they were repeted during each summers between 2012 - 2014. Coupled with the acquisition of physical parameters current data were collected with 500 kHz ADCP every 20s, the resolution of vertical profiles of CTD matches the ADCP 1 meter magnitude vertical resolution. in order to investigate the water column layers dynamics behavior, Brunt-Vaisala and Richardson number were computed using the sampled physical parameters. Coastal surveys analysis highlights the presence of temperature oscillation in proximity of the thermocline and bottom layers; these oscillations have been observed during all measure surveys, when the land breeze was over. Indeed the land breeze tends to generate an offshore transport causing bottom layers to lift. At the same time solar radiation heating causes a sink of the surface layers which flatten the layers in proximity of the thermocline. Therefore the oscillations of temperature observed during the oceanographic surveys have to considered as internal waves, as during earlier studies conducted in the Tyrrhenian Sea has been observed.

  18. The streaming of 1.3 - 2.3 MeV cosmic-ray protons during periods between prompt solar particle events. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Marshall, F. E.

    1977-01-01

    The anisotropy of 1.3 to 2.3 MeV protons in interplanetary space was measured using the Caltech electron/isotope spectrometer aboard IMP-7 for 317 6 hour periods from 72/273 to 74/2. Periods dominated by prompt solar particle events are not included. The convective and diffusive anisotropies were determined from the observed anisotropy using concurrent solar wind speed measurements and observed energy spectra. The diffusive flow of particles was found to be typically toward the sun, indicating a positive radial gradient in the particle density. This anisotropy was inconsistent with previously proposed sources of low energy proton increases seen at 1 AU which involve continual solar acceleration. The typical properties of this new component of low-energy cosmic rays were determined for this period which is near solar minimum.

  19. Proxy records of Late Holocene climate events in the eastern United States: Medieval Warm Period and Little Ice Age

    NASA Astrophysics Data System (ADS)

    Willard, D. A.; Cronin, T. M.; Hayo, K. M.

    2006-12-01

    We are conducting a multiproxy, regional reconstruction of climate variability during the last two millennia including the Medieval Warm Period (MWP) and Little Ice Age (LIA) in eastern North America. Pollen, benthic foraminifers, ostracodes, and other proxies were analyzed from high-resolution sampling of continuous sedimentary records from lakes, wetlands, and estuaries in Florida, North Carolina, Chesapeake Bay, and Lake Champlain. These records document multi-decadal changes in vegetation, temperature, precipitation, and estuarine salinity across a latitudinal transect. During both the MWP and LIA, decreased precipitation altered plant community composition and distribution in the southeastern United States, and the LIA triggered threshold changes in vegetation that persisted until anthropogenic land-cover change overwhelmed the climate signature. In the mid-Atlantic region, progressively cooler and wetter late Holocene springs culminated in a cool, wet LIA; this trend correlates with observed oceanic changes. Trend analysis of the data suggest that inter-regional correlation of multi-decadal and centennial-scale Holocene climate events will be forthcoming.

  20. Biofilm formation and sanitizer resistance of Escherichia coli O157:H7 strains isolated from "high event period" meat contamination.

    PubMed

    Wang, Rong; Kalchayanand, Norasak; King, David A; Luedtke, Brandon E; Bosilevac, Joseph M; Arthur, Terrance M

    2014-11-01

    In the meat industry, a "high event period" (HEP) is defined as a time period during which commercial meat plants experience a higher than usual rate of Escherichia coli O157:H7 contamination. Genetic analysis indicated that within a HEP, most of the E. coli O157:H7 strains belong to a singular dominant strain type. This was in disagreement with the current beef contamination model stating that contamination occurs when incoming pathogen load on animal hides, which consists of diverse strain types of E. coli O157:H7, exceeds the intervention capacity. Thus, we hypothesize that the HEP contamination may be due to certain in-plant colonized E. coli O157:H7 strains that are better able to survive sanitization through biofilm formation. To test our hypothesis, a collection of 45 E. coli O157:H7 strains isolated from HEP beef contamination incidents and a panel of 47 E. coli O157:H7 strains of diverse genetic backgrounds were compared for biofilm formation and sanitizer resistance. Biofilm formation was tested on 96-well polystyrene plates for 1 to 6 days. Biofilm cell survival and recovery growth after sanitization were compared between the two strain collections using common sanitizers, including quaternary ammonium chloride, chlorine, and sodium chlorite. No difference in "early stage" biofilms was observed between the two strain collections after incubation at 22 to 25°C for 1 or 2 days. However, the HEP strains demonstrated significantly higher potency of "mature" biofilm formation after incubation for 4 to 6 days. Biofilms of the HEP strains also exhibited significantly stronger resistance to sanitization. These data suggest that biofilm formation and sanitization resistance could have a role in HEP beef contamination by E. coli O157:H7, which highlights the importance of proper and complete sanitization of food contact surfaces and food processing equipment in commercial meat plants.

  1. Quasi-periodic pulsations with varying period in multi-wavelength observations of an X-class flare

    SciTech Connect

    Huang, Jing; Tan, Baolin; Zhang, Yin; Karlický, Marian; Mészárosová, Hana

    2014-08-10

    This work presents an interesting phenomenon of the period variation in quasi-periodic pulsations (QPPs) observed during the impulsive phase of a coronal mass ejection-related X1.1 class flare on 2012 July 6. The period of QPPs was changed from 21 s at soft X-rays (SXR) to 22-23 s at microwaves, to ∼24 s at extreme ultraviolet emissions (EUV), and to 27-32 s at metric-decimetric waves. The microwave, EUV, and SXR QPPs, emitted from flare loops of different heights, were oscillating in phase. Fast kink mode oscillations were proposed to be the modulation mechanism, which may exist in a wide region in the solar atmosphere from the chromosphere to the upper corona or even to the interplanetary space. Changed parameters of flare loops through the solar atmosphere could result in the varying period of QPPs at different wavelengths. The first appearing microwave QPPs and quasi-periodic metric-decimetric type III bursts were generated by energetic electrons. This may imply that particle acceleration or magnetic reconnection were located between these two non-thermal emission sources. Thermal QPPs (in SXR and EUV emissions) occurred later than the nonthermal ones, which would suggest a some time for plasma heating or energy dissipation in flare loops during burst processes. At the beginning of flare, a sudden collapse and expansion of two separated flare loop structures occurred simultaneously with the multi-wavelength QPPs. An implosion in the corona, including both collapse and expansion of flare loops, could be a trigger of loop oscillations in a very large region in the solar atmosphere.

  2. An Observational Analysis of Coaching Behaviors for Career Development Event Teams: A Mixed Methods Study

    ERIC Educational Resources Information Center

    Ball, Anna L.; Bowling, Amanda M.; Sharpless, Justin D.

    2016-01-01

    School Based Agricultural Education (SBAE) teachers can use coaching behaviors, along with their agricultural content knowledge to help their Career Development Event (CDE) teams succeed. This mixed methods, collective case study observed three SBAE teachers preparing multiple CDEs throughout the CDE season. The teachers observed had a previous…

  3. Regional and local new particle formation events observed in the Yangtze River Delta region, China

    NASA Astrophysics Data System (ADS)

    Dai, Liang; Wang, Honglei; Zhou, Luyu; An, Junlin; Tang, Lili; Lu, Chunsong; Yan, Wenlian; Liu, Ruiyang; Kong, Shaofei; Chen, Mindong; Lee, Shanhu; Yu, Huan

    2017-02-01

    To study the spatial inhomogeneity of new particle formation (NPF) in the polluted atmosphere of China, we conducted simultaneous measurements at an urban site near a petrochemical industrial area and a regional background site in the Yangtze River Delta region from September to November 2015. At the urban site we observed a type of local NPF event (number of events: n = 5), in which nucleation was limited to a small area but persisted for 6.8 h on average during the daytime. Formation rates of 5 nm particles (J5) were found to be correlated positively with the H2SO4 proxy (log J5 versus log[H2SO4] slope near 1) in both local and regional events. Furthermore, J5 was enhanced by the anthropogenic volatile organic carbon (VOC) plumes from nearby industrial area in the local events compared to the regional events. Size-dependent aerosol dynamics calculation showed that in comparison with the observed regional events, the local events were featured with high nucleation rate (J1.3 > 1000 cm-3 s-1), high growth rate of sub-3 nm particles (GRsub-3 > 20 nm h-1), and high number concentration of nucleation mode particles (mean peak N5-20: 6 × 104 cm-3). Considering these features, the local NPF events of anthropogenic origin may also be an important contributor to cloud condensation nuclei concentrations in urban and regional scales. In addition, the comparison of simultaneous regional NPF events between the two sites (number of events: n = 7) suggested that regional NPF intensity may be underestimated by the single-point measurement at an urban site, due to the heterogeneity of air masses.

  4. Observation of Long Ionospheric Recoveries from Lightning-induced Electron Precipitation Events

    NASA Astrophysics Data System (ADS)

    Mohammadpour Salut, M.; Cohen, M.

    2015-12-01

    Lightning strokes induces lower ionospheric nighttime disturbances which can be detected through Very Low Frequency (VLF) remote sensing via at least two means: (1) direct heating and ionization, known as an Early event, and (2) triggered precipitation of energetic electrons from the radiation belts, known as Lightning-induced Electron Precipitation (LEP). For each, the ionospheric recover time is typically a few minutes or less. A small class of Early events have been identified as having unusually long ionospheric recoveries (10s of minutes), with the underlying mechanism still in question. Our study shows for the first time that some LEP events also demonstrate unusually long recovery. The VLF events were detected by visual inspection of the recorded data in both the North-South and East-West magnetic fields. Data from the National Lightning Detection Network (NLDN) are used to determine the location and peak current of the lightning responsible for each lightning-associated VLF perturbation. LEP or Early VLF events are determined by measuring the time delay between the causative lightning discharges and the onset of all lightning-associated perturbations. LEP events typically possess an onset delay greater than ~ 200 msec following the causative lightning discharges, while the onset of Early VLF events is time-aligned (<20 msec) with the lightning return stroke. Nonducted LEP events are distinguished from ducted events based on the location of the causative lightning relative to the precipitation region. From 15 March to 20 April and 15 October to 15 November 2011, a total of 385 LEP events observed at Indiana, Montana, Colorado and Oklahoma VLF sites, on the NAA, NLK and NML transmitter signals. 46 of these events exhibited a long recovery. It has been found that the occurrence rate of ducted long recovery LEP events is higher than nonducted. Of the 46 long recovery LEP events, 33 events were induced by ducted whistlers, and 13 events were associated with

  5. Video and photometric observations of a sprite in coincidence with a meteor-triggered jet event

    SciTech Connect

    Suszcynsky, D. M.; Strabley, R.; Roussel-Dupre, R.; Symbalisty, E. M. D.; Armstrong, R. A.; Lyons, W. A.; Taylor, M.

    1999-12-27

    Video and photometric observations of a meteor-triggered ''jet'' event in association with the occurrence of a sprite were collected during the SPRITES '98 campaign. The event raises interest in the question of possible meteoric triggering of upper atmospheric transients as originally suggested by Muller [1995]. The event consisted of three stages: (1) the observation of a moderately bright meteor, (2) the development of a sprite in the immediate vicinity of the meteor as the meteor reached no lower than {approx}70 km altitude, and (3) a slower-forming jet of luminosity that appeared during the late stages of the sprite and propagated back up the ionization trail of the meteor. The event is analyzed in terms of its geometry, its relevance to the meteor, and the implications to existing theories for sprite formation. (c) 1999 American Geophysical Union.

  6. Observation and Interpretation of Energetic Neutral Hydrogen Atoms from the December 5, 2006 Solar Event

    NASA Technical Reports Server (NTRS)

    Mewaldt, R. A.; Leske, R. A.; Stone, E. C.; Barghouty, A. F.; Shih, A. Y.; von Rosenvinge, T. T.; Labrador, A. W.; Cohen, C. M. S.; Cummings, A. C.; Cummings, A. C.

    2009-01-01

    We report the first observations of energetic neutral atoms (ENAs) from a solar flare/coronal mass ejection event. The observations were made during the December 5, 2006 X9 solar flare, located at E79, by the Low Energy Telescopes (LETs) on the STEREO A and B spacecraft. Within 1-2 hours of the flare onset, both LETs observed a sudden burst of 1.6 to 15 MeV protons arriving hours before the onset of the main solar energetic particle (SEP) event at Earth. More than 70% of these particles arrived from a longitude within +-10 degrees of the Sun. The derived emission profile at the Sun lasted for more than an hour and had a profile remarkably similar to the GOES soft X-ray profile. The observed arrival directions and energy spectrum argue strongly that the particle events <5 MeV were due to energetic neutral hydrogen atoms that were stripped of their electrons upon entering the LET sensor. To our knowledge, this is the first reported observation of ENA emission from a solar flare/coronal mass ejection. We discuss possible origins for the production of ENAs in solar events, including charge-transfer reactions involving both flare and shock-accelerated protons. Assuming isotropic emission, we find that 2 x 10E28 ENAs escaped from the Sun in the upper hemisphere. Based on the 2.2 MeV gamma-ray emission observed by RHESSI in this event, and using measured and theoretical cross sections, we estimate that 3 x 10E31 ENAs with 1.8 - 5 MeV could be produced by protons accelerated in the flare. CME-driven shock acceleration is also a possible ENA source, but unfortunately there were no CME observations available from this event. Taking into account ENA losses, we conclude that the observed ENAs were most likely produced in the high corona at heliocentric distances 1.6 solar radii.

  7. Estimating the length of waits: a description of the period lifetable method and comparison with census and event based methods.

    PubMed

    Armstrong, Paul W

    2012-05-01

    To discover whether the period lifetable provides more valid estimates of length of wait in prospect than are obtained using the lengths either of (current) waits captured at the time of the mid-period census or of the (prior) waits of those extracted over a specified period. We determined whether there was a surplus (or a deficiency) of extractions within the cross-classification of cohort and waiting time category which straddled each census. We used census-, event- and lifetable-based methods to produce three period-specific estimates of the percentage of waits of 0-2 months, and we determined whether length of wait grew shorter (or longer) from one period to the next. We used Lambda B to indicate the extent to which we were able to predict the direction of change in length of wait once we knew the direction of change in size of list. We found a direct correlation between change in length of wait and change in size of list, as expected under the stock-flow model, when length of wait was estimated using the lifetable for the period (L(B) = 58.33, 95% confidence interval [CI] = 29-88), but we obtained a null correlation when we used census-based estimates (L(B) = 6.45) and we obtained an inverse correlation when we used event-based estimates (L(B) = 57.14, 95% CI = 31-83). The period lifetable appears to provide more valid estimates of length of wait and should therefore be substituted for census- and event-based methods of estimation, wherever possible.

  8. Flux Transfer Event in the Subsolar Region and Near the Cusp: Simultaneous Polar and Cluster Observations

    NASA Technical Reports Server (NTRS)

    Le, G.; Zheng, Y.; Russell, C. T.; Pfaff, R. F.; Slavin, J. A.; Lin, N.; Mozer, F.; Parks, G.; Petrinec, S. M.; Lucek, e. A.; Reme, Henri

    2005-01-01

    The phenomenon called flux transfer events (FTEs) is widely accepted as the manifestation of time-dependent reconnection. In this paper, we present an observational evidence of a flux transfer event observed simultaneously at low-latitude by Polar and high-latitude by Cluster. This event occurred on March 21, 2002, when both Cluster and Polar were located near the local noon but with large latitudinal distance. Cluster was moving outbound from polar cusp to the magnetosheath, and Polar was in the magnetosheath near the equatorial magnetopause. The observations show that a flux transfer event was formed between the equator and the northern cusp. Polar and Cluster observed the FTE's two open flux tubes: Polar saw the southward moving flux tube near the equator; and Cluster the , northward moving flux tube at high latitude. Unlike low-latitude FTEs, the high-latitude FTE did not exhibit the characteristic bi-polar BN signature. But the plasma data clearly showed its open flux tube configuration. Enhanced electric field fluctuations were observed within the FTE core, both at low- and high-attitudes. This event provides us a unique opportunity to understand high-latitude FTE signatures and the nature of time-varying reconnection.

  9. Archive of observations of periodic comet Crommelin made during its 1983-84 apparition

    NASA Technical Reports Server (NTRS)

    Sekanina, Z. (Editor); Aronsson, M.

    1985-01-01

    This is an archive of 680 reduced observations of Periodic Comet Crommelin made during its 1984 apparition. The archive integrates reports by members of the eight networks of the International Halley Watch (IHW) and presents the results of a trial run designed to test the preparedness of the IHW organization for the current apparition of Periodic Comet Halley.

  10. Observing a Chemically and/or Climatically Important Volcano: Facilitating Rapid Response to an Unanticipated yet Inevitable Event

    NASA Astrophysics Data System (ADS)

    Kaye, J. A.

    2015-12-01

    A large volcanic event has the potential to influence the chemical and/or physical state of the Earth's atmosphere in a significant way. In particular, changes in the trace constituent and/or particulate composition of the stratosphere, as well as the temperature distribution of the troposphere and stratosphere can both take place (and persist over a period of time), as has been observed in several eruptions in recent years (e.g., the Mount Pinatubo eruption in 1991). Characterizing the impacts of these eruptions and predicting their impacts on the evolution of the atmosphere requires observations of gas and particle distributions over time period from as soon after eruption as possible to the longer time period over which the Earth system is affected. This characterization may make use of observation capabilities from ongoing surface-based and existing satellite-based observing systems, and can also benefit significantly from focused airborne campaigns that make use of both in situ and remote sensing instrumentation. This presentation will review the relevant surface- and space-based observing capability operated by NASA in the broader context of the global observing capabilities of the international community, and and will discuss potential approaches to airborne campaigns (platforms, sensors, systems, logistical consideration) that would provide the data most useful for both characterization and forecasting of both the chemical and climatic forcing and impacts associated with the eruption.

  11. Observed characteristics of dust storm events over the western United States using meteorological, satellite, and air quality measurements

    NASA Astrophysics Data System (ADS)

    Lei, H.; Wang, J. X. L.

    2014-08-01

    To improve dust storm identification over the western United States, historical dust events measured by air quality and satellite observations are analyzed based on their characteristics in data sets of regular meteorology, satellite-based aerosol optical depth (AOD), and air quality measurements. Based on the prevailing weather conditions associated with dust emission, dust storm events are classified into the following four typical types: (1) The key feature of cold front-induced dust storms is their rapid process with strong dust emissions. (2) Events caused by meso- to small-scale weather systems have the highest levels of emissions. (3) Dust storms caused by tropical disturbances show a stronger air concentration of dust and last longer than those in (1) and (2). (4) Dust storms triggered by cyclogenesis last the longest. In this paper, sample events of each type are selected and examined to explore characteristics observed from in situ and remote-sensing measurements. These characteristics include the lasting period, surface wind speeds, areas affected, average loading on ground-based optical and/or air quality measurements, peak loading on ground-based optical and/or air quality measurements, and loading on satellite-based aerosol optical depth. Based on these analyses, we compare the characteristics of the same dust events captured in different data sets in order to define the dust identification criteria. The analyses show that the variability in mass concentrations captured by in situ measurements is consistent with the variability in AOD from stationary and satellite observations. Our analyses also find that different data sets are capable of identifying certain common characteristics, while each data set also provides specific information about a dust storm event. For example, the meteorological data are good at identifying the lasting period and area impacted by a dust event; the ground-based air quality and optical measurements can capture the peak

  12. OBSERVATIONS OF EUV WAVES IN {sup 3}He-RICH SOLAR ENERGETIC PARTICLE EVENTS

    SciTech Connect

    Bucík, R.; Innes, D. E.; Guo, L.; Mason, G. M.; Wiedenbeck, M. E.

    2015-10-10

    Small {sup 3}He-rich solar energetic particle (SEP) events with their anomalous abundances, markedly different from the solar system, provide evidence for a unique acceleration mechanism that operates routinely near solar active regions. Although the events are sometimes accompanied by coronal mass ejections (CMEs), it is believed that mass and isotopic fractionation is produced directly in the flare sites on the Sun. We report on a large-scale extreme-ultraviolet (EUV) coronal wave observed in association with {sup 3}He-rich SEP events. In the two examples discussed, the observed waves were triggered by minor flares and appeared concurrently with EUV jets and type III radio bursts, but without CMEs. The energy spectra from one event are consistent with so-called class-1 (characterized by power laws) {sup 3}He-rich SEP events, while the other with class-2 (characterized by rounded {sup 3}He and Fe spectra), suggesting different acceleration mechanisms in the two. The observation of EUV waves suggests that large-scale disturbances, in addition to more commonly associated jets, may be responsible for the production of {sup 3}He-rich SEP events.

  13. High-cadence observations of spicular-type events and their wave-signatures

    NASA Astrophysics Data System (ADS)

    Shetye, Juie

    2016-05-01

    We present, a statistical study of spectral images, taken from the CRISP instrument at the Swedish 1-m Solar Telescope in H-alpha 656.28 nm of fast spicules with Doppler velocities in the range of -41km/s to +41 km/s. Remarkably, many of these spicules display apparent velocities above 500 km/s, very short lifetimes of up to 20 s combined with width or thickness of 100 km and apparent lengths of around 3500 km. Here we present, the other spectral properties of these events in the H-alpha line scan. Most features showed signature in multiple line position as we scan along the line scan. In around 89 % of the cases, there is temporal offset by 3.7 s to 5 s between the red-wing and blue-wing signatures. Another result is that 25% of cases are repetitive i.e. appear at the same location but they are not co-temporal or necessarily periodic in nature. Putting all the evidence together, we interpret the observations as mass motions (of flux tubes) that appear in the field-of-view of CRISP’s 0.0060 nm filters in the line of sight, along their projection as we scan. Further we observed transverse motion associated with these structures, which in some cases could be related to high-frequency kink-waves. We describe some cases showing this motion and the energies associated with them. The current work presented already tests the limits of current telescopes in terms of the temporal and spatial resolution. DKIST VTF instrument, having 3 times more spatial resolution than CRISP and much higher temporal resolution, we can being to understand the nature of such fine-scale transient phenomena in greater details.

  14. Approaching Solar Maximum 24 with Stereo-Multipoint Observations of Solar Energetic Particle Events

    NASA Technical Reports Server (NTRS)

    Dresing, N.; Cohen, C. M. S.; Gomez-Herrero, R.; Heber, B.; Klassen, A.; Leske, R. A.; Mason, G. M.; Mewaldt, R. A.; von Rosenvinge, T. T.

    2014-01-01

    Since the beginning of the Solar Terrestrial Relations Observatory (STEREO) mission at the end of 2006, the two spacecraft have now separated by more than 130? degrees from the Earth. A 360-degree view of the Sun has been possible since February 2011, providing multipoint in situ and remote sensing observations of unprecedented quality. Combining STEREO observations with near-Earth measurements allows the study of solar energetic particle (SEP) events over a wide longitudinal range with minimal radial gradient effects. This contribution provides an overview of recent results obtained by the STEREO/IMPACT team in combination with observations by the ACE and SOHO spacecraft. We focus especially on multi-spacecraft investigations of SEP events. The large longitudinal spread of electron and 3He-rich events as well as unusual anisotropies will be presented and discussed.

  15. Rupture directivity of fluid-induced microseismic events: Observations from an enhanced geothermal system

    NASA Astrophysics Data System (ADS)

    Folesky, Jonas; Kummerow, Jörn; Shapiro, Serge A.; Häring, Markus; Asanuma, Hiroshi

    2016-11-01

    The rupture process of fluid-induced microseismic events is still poorly understood, mainly due to usually small magnitudes and sparse monitoring geometries. The high-quality recordings of the earthquake sequence 2006-2007 at the enhanced geothermal system at Basel, Switzerland, constitute a rare exception, allowing a systematic directivity study of 195 events using the empirical Green's function method. We observe clear directivity signatures for about half the events which demonstrates that rupture directivity persists down to small magnitudes (ML˜1). The predominant rupture behavior is unilateral. We further find evidence that directivity is magnitude dependent and varies systematically with distance from the injection source. Whereas pore pressure seems to play the dominant role close to the injection source and no preferred rupture direction is observable, directivity aligns parallel to the event distribution with increasing distance (≳100 m) and is preferably oriented away from the injection point. The largest analyzed events (ML˜2) show a distinct behavior: They rupture toward the injection source, suggesting that they nucleate in the vicinity of the pressure front and propagate backward into the perturbed volume. This finding is of particular relevance for seismic hazard assessment of georeservoirs, since it implies that maximum event size is related to dimension of the fluid-perturbed volume. Our study also resolves rupture complexities for a small group of events. This shows that small fault heterogeneities exist down to a scale of a few tens of meters. The observation of directivity and complexity in induced microseismic events suggest that future source studies account for these phenomena.

  16. Origins of Anisotropic 40 300 keV Electron Events Observed at Low and High Latitudes

    NASA Astrophysics Data System (ADS)

    Hawkins, S. E., III; Gold, R. E.; Pick, M.; Maia, D.

    2001-05-01

    Using a survey of anisotropic electron events in the energy range of ˜40 300 keV observed by HI-SCALE on Ulysses, we have selected several time intervals during 1999 when Ulysses traveled from about 20° S at 5.2 AU (January 1999) to 42° S at 4.2 AU (January 2000). We compare these events with observations at ˜1 AU using the nearly identical instrument, EPAM on ACE. In order to study the solar origins of these electrons using the imaging Nançay Radioheliograph, we further restricted the list of events to those in which interplanetary magnetic field lines with origins on the visible solar disk, intersected Ulysses. We find that not all the anisotropic electron events are observed by both spacecraft and there exists a strong dependence on the spacecraft's magnetic connection back to the Sun. We have identified the solar origin for five electron events using radio observations, and correlate these with interplanetary type-III radio emissions using the WIND/WAVES experiment.

  17. Observing deeper magmatic cycles from shallow seismic and infrasonic events, Villarrica Volcano, Chile

    NASA Astrophysics Data System (ADS)

    Richardson, J. P.; Waite, G. P.

    2013-12-01

    Villarrica volcano is presently an open-vent volcano, characterized by continuous but variable passive degassing. This persistent degassing produces both infrasonic and seismic tremor. Minor strombolian style eruptions at the surface of the lava lake, which rarely deposit material outside of the crater rim, produce both seismic long-period events and infrasonic pulses. During three campaigns between 2010 and 2012, we investigated the activity using temporary seismic networks with collocated infrasound sensors. These sensors were deployed from within the crater to greater than ten kilometers distance. Using our station distribution, we created a matched filter to identify events similar to a template event associated with a strombolian eruption. Although the bubble bursting events were found to be small, we found that they were nearly identical in seismic signature. By stacking these events, we were able to perform an inversion of the event as seen by our network, and found that the best-fit was a nearly horizontal, E-W directed force within the crater. We interpret this mechanism as the response of the lava lake to outgassing, where lava sloshes to fill the void left by the escaping gas, producing seismic signals as the lava drags along the floor and sides of the crater. Using the catalog created by the matched filter for the seismic long-period events, we also compared the response of the collocated infrasound sensors to the bubble burst events. We found the signals recorded at the infrasound sensors to be coherent when aligned according to the seismic catalog, but the seismic-acoustic delay time was found to systematically vary throughout the deployment. We also calculated the volcano acoustic-seismic ratio (VASR) using our catalog of seismic and infrasonic events. We found that shorter seismic-acoustic delays were well correlated with a higher VASR, corresponding to shallower lava lake levels. The lava lake high stands also correlated with higher seismic and

  18. Probability Estimates of Solar Particle Event Doses During a Period of Low Sunspot Number for Thinly-Shielded Spacecraft and Short Duration Missions

    NASA Technical Reports Server (NTRS)

    Atwell, William; Tylka, Allan J.; Dietrich, William; Rojdev, Kristina; Matzkind, Courtney

    2016-01-01

    In an earlier paper (Atwell, et al., 2015), we investigated solar particle event (SPE) radiation exposures (absorbed dose) to small, thinly-shielded spacecraft during a period when the sunspot number (SSN) was less than 30. These SPEs contain Ground Level Events (GLE), sub-GLEs, and sub-sub-GLEs (Tylka and Dietrich, 2009, Tylka and Dietrich, 2008, and Atwell, et al., 2008). GLEs are extremely energetic solar particle events having proton energies extending into the several GeV range and producing secondary particles in the atmosphere, mostly neutrons, observed with ground station neutron monitors. Sub-GLE events are less energetic, extending into the several hundred MeV range, but do not produce secondary atmospheric particles. Sub-sub GLEs are even less energetic with an observable increase in protons at energies greater than 30 MeV, but no observable proton flux above 300 MeV. In this paper, we consider those SPEs that occurred during 1973-2010 when the SSN was greater than 30 but less than 50. In addition, we provide probability estimates of absorbed dose based on mission duration with a 95% confidence level (CL). We also discuss the implications of these data and provide some recommendations that may be useful to spacecraft designers of these smaller spacecraft.

  19. Observation of an optical event horizon in a silicon-on-insulator photonic wire waveguide.

    PubMed

    Ciret, Charles; Leo, François; Kuyken, Bart; Roelkens, Gunther; Gorza, Simon-Pierre

    2016-01-11

    We report on the first experimental observation of an optical analogue of an event horizon in integrated nanophotonic waveguides, through the reflection of a continuous wave on an intense pulse. The experiment is performed in a dispersion-engineered silicon-on-insulator waveguide. In this medium, solitons do not suffer from Raman induced self-frequency shift as in silica fibers, a feature that is interesting for potential applications of optical event horizons. As shown by simulations, this also allows the observation of multiple reflections at the same time on fundamental solitons ejected by soliton fission.

  20. Torsional oscillations and observed rotational period variations in early-type stars

    NASA Astrophysics Data System (ADS)

    Krtička, J.; Mikulášek, Z.; Henry, G. W.; Kurfürst, P.; Karlický, M.

    2017-01-01

    Some chemically peculiar stars in the upper main sequence show rotational period variations of unknown origin. We propose that these variations are a consequence of the propagation of internal waves in magnetic rotating stars that lead to the torsional oscillations of the star. We simulate the magnetohydrodynamic waves and calculate resonant frequencies for two stars that show rotational variations: CU Vir and HD 37776. We provide updated analyses of rotational period variations in these stars and compare our results with numerical models. For CU Vir, the length of the observed rotational period cycle, Π=67.6(5) yr, can be well reproduced by the models, which predict a cycle length of 51 yr. However, for HD 37776, the observed lower limit of the cycle length, Π ≥ 100 yr, is significantly longer than the numerical models predict. We conclude that torsional oscillations provide a reasonable explanation at least for the observed period variations in CU Vir.

  1. Antarctic Ground-based Observations During Selected THEMIS Satellite Event Studies

    NASA Astrophysics Data System (ADS)

    Weatherwax, A. T.; Lessard, M.; Lanzerotti, L.; Mende, S.; Frey, H.; Inan, U.; Spasojevic, M.; Engebretson, M.; Posch, J.; Petit, N.; Clauer, R.; Labelle, J.; Ridley, A.; Rosenberg, T.; Detrick, D.

    2007-12-01

    In Antarctica, the Polar Experiment Network for Geospace Upper-atmosphere Investigations (PENGUIn) team operates a suite of optical and radio wave imagers, magnetometers, riometers, and ELF-HF receivers at South Pole and McMurdo stations, as well as from the Automated Geophysical Observatories (AGOs) on the Antarctic polar plateau. These stations span locations from the auroral zone to deep in the polar cap. Employing data from this array, ground-based observations during several THEMIS satellite event studies will be discussed. These include: a flux transfer event (FTE) on May 20, 2007; a solar wind shock propagation on June 21; a hot flow anomaly on July 4; high latitude optical events on August 8th and 10th; and substorm events on March 23rd and 24th. Of particular interest is the FTE event where the magnetometer Z-component appears to have the signature of a line current passing overhead at South Pole and a sharp cutoff of 2-4 kHz VLF signals is also observed at the time the current moved overhead. Cosmic noise absorption and 630 nm optical signals also began about the time the currents moved overhead, and then tracked the H-component of the magnetometer. The enhanced optical signal was coincident with increased ionosphere currents as shown by the H-component. In this presentation, a southern hemisphere contextual description of this event, and the others listed above, will be presented.

  2. Observations and Light Curve Solutions of Four Ultrashort-Period Binaries

    NASA Astrophysics Data System (ADS)

    Kjurkchieva, D.; Popov, V.; Vasileva, D.; Petrov, N.

    2016-06-01

    The paper presents light curve solutions of our observations of four new ultrashort-period eclipsing binaries with MS components. Two of them have periods almost at the upper limit (0.22 days) of the ultrashort-period binaries, while the periods of around 0.18 days of CSS J171508.5+350658 and CSS J214633.8+120016 are amongst the shortest known orbital periods. CSS J171410.0+445850, CSS J214633.8+120016 and CSS J224326.0+154532 are overcontact binaries with fillout factors around 0.25 while CSS J171508.5+350658 is a semidetached system. The two targets with shortest periods consist of M dwarfs.

  3. The Trend in the Observation of Legacy Long Period Variable Stars (Poster abstract)

    NASA Astrophysics Data System (ADS)

    Dudley, R.

    2015-06-01

    (Abstract only) A decrease in the number of observers of the Legacy Long Period Variable Stars has been noted by the AAVSO. Amongst the observing community there is the perception that observers collecting digital data is making up for this gap. Data from the annual President's report (2002-2013) and the AAVSO International Data Base for the years 1993, 2003, and 2013 were analyzed. For the period of 2002 to 2013 the total number of observers remained fairly constant (816 ± 97) with a large bump in 2011. The number of observations has slowly declined since 2007 though there has recently been an increase in the number of observations. From the AID data the number of observations reached a maximum in 2003 and has slowly declined afterwards. These trends as well as other information gleamed from the data will be present and discussed.

  4. SAS 3 observations of two X-ray transient events with precursors

    NASA Technical Reports Server (NTRS)

    Hoffman, J. A.; Lewin, W. H. G.; Doty, J.; Jernigan, J. G.; Haney, M.; Richardson, J. A.

    1978-01-01

    SAS 3 has observed two unusual fast transient X-ray events from different sources, one lasting about 150 s and one, approximately 1500 s. Both events were preceded by precursor pulses which lasted a few seconds and which rose and fell in less than 0.4 s. The precursors were separated from the 'main' events by several seconds, during which no X-rays were detected. There are similarities between the two main events and X-ray bursts in both their temporal and spectral evolution. The spectra of the main events started out much softer than the spectra of the precursors, became harder as they approached maximum intensity, and softened as they decayed. In the 1500-s event, X-rays with energies greater than 10 keV were delayed by about 80 s compared with 1.5-6-keV X-rays. A blackbody fit to the spectral data of the main event of approximately 1500-s duration gives a maximum temperature of 29 million K and a radius for the emitting region of at least about 9 km (at a distance of 10 kpc); this is similar to the temperature and sizes found for several X-ray burst sources.

  5. River flood events in Thailand and Bangladesh observed by CryoSat-2

    NASA Astrophysics Data System (ADS)

    Nielsen, Karina; Villadsen, Heidi; Andersen, Ole; Stenseng, Lars; Knudsen, Per

    2015-04-01

    The high along track resolution of the SIRAL altimeter carried on-board CryoSat-2 offers a wide range of unique opportunities for satellite monitoring. This study focuses on the ability of CryoSat-2 to detect the effects of flood events such as increased river levels and inundation of land. Here we study two flood events; the Bangladesh flood event of June 2012 and the flooding in Thailand that lasted between July 2011 and January 2012. The flooding in these areas was caused by abnormal monsoonal rainfall and affected millions of people. We process CryoSat-2 level 1b SAR mode data to derive water levels for the areas and compare these levels before, during and after the flooding events. Other parameters such as the backscatter coefficient and pulse peakiness are also considered. To verify the extent of the flooding observed by CryoSat-2 we compare with independent sources such as Landsat images.

  6. Characteristics of Four Upward-Pointing Cosmic-Ray-like Events Observed with ANITA

    NASA Astrophysics Data System (ADS)

    Gorham, P. W.; Nam, J.; Romero-Wolf, A.; Hoover, S.; Allison, P.; Banerjee, O.; Beatty, J. J.; Belov, K.; Besson, D. Z.; Binns, W. R.; Bugaev, V.; Cao, P.; Chen, C.; Chen, P.; Clem, J. M.; Connolly, A.; Dailey, B.; Deaconu, C.; Cremonesi, L.; Dowkontt, P. F.; Duvernois, M. A.; Field, R. C.; Fox, B. D.; Goldstein, D.; Gordon, J.; Hast, C.; Hebert, C. L.; Hill, B.; Hughes, K.; Hupe, R.; Israel, M. H.; Javaid, A.; Kowalski, J.; Lam, J.; Learned, J. G.; Liewer, K. M.; Liu, T. C.; Link, J. T.; Lusczek, E.; Matsuno, S.; Mercurio, B. C.; Miki, C.; Miočinović, P.; Mottram, M.; Mulrey, K.; Naudet, C. J.; Ng, J.; Nichol, R. J.; Palladino, K.; Rauch, B. F.; Reil, K.; Roberts, J.; Rosen, M.; Rotter, B.; Russell, J.; Ruckman, L.; Saltzberg, D.; Seckel, D.; Schoorlemmer, H.; Stafford, S.; Stockham, J.; Stockham, M.; Strutt, B.; Tatem, K.; Varner, G. S.; Vieregg, A. G.; Walz, D.; Wissel, S. A.; Wu, F.; Anita Collaboration

    2016-08-01

    We report on four radio-detected cosmic-ray (CR) or CR-like events observed with the Antarctic Impulsive Transient Antenna (ANITA), a NASA-sponsored long-duration balloon payload. Two of the four were previously identified as stratospheric CR air showers during the ANITA-I flight. A third stratospheric CR was detected during the ANITA-II flight. Here, we report on characteristics of these three unusual CR events, which develop nearly horizontally, 20-30 km above the surface of Earth. In addition, we report on a fourth steeply upward-pointing ANITA-I CR-like radio event which has characteristics consistent with a primary that emerged from the surface of the ice. This suggests a possible τ -lepton decay as the origin of this event, but such an interpretation would require significant suppression of the standard model τ -neutrino cross section.

  7. Observations and Interpretations of Energetic Neutral Hydrogen Atoms from the December 5, 2006 Solar Event

    NASA Technical Reports Server (NTRS)

    Mewaldt, R. A.; Leske, R. A.; Shih, A. Y.; Stone, E. C.; Barghouty, A. f.; Cohen, C. M. S.; Cummings, A. c.; Labrador, A. W.; vonRosenvinge, T. T.

    2009-01-01

    We discuss recently reported observations of energetic neutral hydrogen atoms (ENAs) from an X9 solar flare/coronal mass ejection event on 5 December 2006, located at E79. The observations were made by the Low Energy Telescopes (LETs) on STEREO A and B. Prior to the arrival of the main solar energetic particle (SEP) event at Earth, both LETs observed a sudden burst of 1.6 to 15 MeV energetic neutral hydrogen atoms produced by either flare or shock-accelerated protons. RHESSI measurements of the 2.2-MeV gamma-ray line provide an estimate of the number of interacting flare-accelerated protons in this event, which leads to an improved estimate of ENA production by flare-accelerated protons. Taking into account ENA losses, we find that the observed ENAs must have been produced in the high corona at heliocentric distances > or equal to 2 solar radii. Although there are no CME images from this event, it is shown that CME-shock-accelerated protons can, in principle, produce a time-history consistent with the observations.

  8. Multipoint Observations of Coronal Mass Ejection and Solar Energetic Particle Events on Mars and Earth During November 2001

    NASA Technical Reports Server (NTRS)

    Falkenberg, T. V.; Vennerstrom, S.; Brain, D. A.; Delory, G.; Taktakishvili, A.

    2011-01-01

    Multipoint spacecraft observations provide unique opportunities to constrain the propagation and evolution of interplanetary coronal mass ejections (ICMEs) throughout the heliosphere. Using Mars Global Surveyor (MGS) data to study both ICME and solar energetic particle (SEP) events at Mars and OMNI and Geostationary Operational Environmental Satellite (GOES) data to study ICMEs and SEPs at Earth, we present a detailed study of three CMEs and flares in late November 2001. In this period, Mars trailed Earth by 56deg solar longitude so that the two planets occupied interplanetary magnetic field lines separated by only approx.25deg. We model the interplanetary propagation of CME events using the ENLIL version 2.6 3-D MHD code coupled with the Wang-Sheeley-Arge version 1.6 potential source surface model, using Solar and Heliospheric Observatory (SOHO) Large Angle and Spectrometric Coronagraph (LASCO) images to determine CME input parameters. We find that multipoint observations are essential to constrain the simulations of ICME propagation, as two very different ICMEs may look very similar in only one observational location. The direction and width of the CME as parameters essential to a correct estimation of arrival time and amplitude of the ICME signal. We find that these are problematic to extract from the analysis of SOHO/LASCO images commonly used for input to ICME propagation models. We further confirm that MGS magnetometer and electron reflectometer data can be used to study not only ICME events but also SEP events at Mars, with good results providing a consistent picture of the events when combined with near-Earth data.

  9. Studies of Arctic Tropospheric Ozone Depletion Events Through Buoy-Borne Observations and Laboratory Studies

    NASA Astrophysics Data System (ADS)

    Halfacre, John W.

    The photochemically-induced destruction of ground-level Arctic ozone in the Arctic occurs at the onset of spring, in concert with polar sunrise. Solar radiation is believed to stimulate a series of reactions that cause the production and release of molecular halogens from frozen, salty surfaces, though this mechanism is not yet well understood. The subsequent photolysis of molecular halogens produces reactive halogen atoms that remove ozone from the atmosphere in these so-called "Ozone Depletion Events" (ODEs). Given that much of the Arctic region is sunlit, meteorologically stable, and covered by saline ice and snow, it is expected that ODEs could be a phenomenon that occurs across the entire Arctic region. Indeed, an ever-growing body of evidence from coastal sites indicates that Arctic air masses devoid of O3 most often pass over sea ice-covered regions before arriving at an observation site, suggesting ODE chemistry occurs upwind over the frozen Arctic Ocean. However, outside of coastal observations, there exist very few long-term observations from the Arctic Ocean from which quantitative assessments of basic ODE characteristics can be made. This work presents the interpretation of ODEs through unique chemical and meteorological observations from several ice-tethered buoys deployed around the Arctic Ocean. These observations include detection of ozone, bromine monoxide, and measurements of temperature, relative humidity, atmospheric pressure, wind speed, and wind direction. To assess whether the O-Buoys were observing locally based depletion chemistry or the transport of ozone-poor air masses, periods of ozone decay were interpreted based on current understanding of ozone depletion kinetics, which are believed to follow a pseudo-first order rate law. In addition, the spatial extents of ODEs were estimated using air mass trajectory modeling to assess whether they are a localized or synoptic phenomenon. Results indicate that current understanding of the

  10. Solar wind plasma periodicities observed at 1 AU by IMP 8

    NASA Technical Reports Server (NTRS)

    Paularena, K. I.; Szabo, A.; Lazarus, A. J.

    1995-01-01

    The IMP 8 spacecraft has been in Earth orbit since 1973, gathering plasma data over one complete 22-year solar cycle. These data are being examined to look for periodicities at time scales ranging from several hours to the entire span of the data set. A 1.3-year periodicity in the radial speed observed by IMP 8 and Voyager 2 has already been reported for the years from 1987 to 1993. The periodogram method, useful for unevenly sampled data such as the IMP 8 plasma data, has been used to search for other periods. It is interesting to note that the 13-year period is not present in the out-of-the-ecliptic component of the velocity (Vz), although a 1-year period is very obvious both visually and on the periodogram. Both components show a very strong peak associated with the 11-year solar cycle variation. This work will be extended to the thermal speed (a measure of the wind's temperature) and density, although the frequent correlations between these parameters and the velocity are expected to cause similar results. Additionally, the fine resolution data will be examined for shorter time periods than are visible using the hourly average data which are appropriate for longer periods. A comparison with periods observed at other spacecraft may also be made.

  11. The magnetic network location of explosive events observed in the solar transition region

    NASA Technical Reports Server (NTRS)

    Porter, J. G.; Dere, K. P.

    1991-01-01

    Compact short-lived explosive events have been observed in solar transition region lines with the High-Resolution Telescope and Spectrograph (HRTS) flown by the Naval Research Laboratory on a series of rockets and on Spacelab 2. Data from Spacelab 2 are coaligned with a simultaneous magnetogram and near-simultaneous He I 10,380 -A spectroheliogram obtained at the National Solar Observatory at Kitt Peak. The comparison shows that the explosive events occur in the solar magnetic network lanes at the boundaries of supergranular convective cells. However, the events occur away from the larger concentrations of magnetic flux in the network, in contradiction to the observed tendency of the more energetic solar phenomena to be associated with the stronger magnetic fields.

  12. Diagnosing peak-discharge power laws observed in rainfall runoff events in Goodwin Creek experimental watershed

    NASA Astrophysics Data System (ADS)

    Furey, Peter R.; Gupta, Vijay K.

    2007-11-01

    Observations from the Goodwin Creek experimental watershed (GCEW), Mississippi show that peak-discharge Q( A) and drainage area A are related, on average, by a power law or scaling relationship, Q( A) = αAθ, during single rainfall-runoff events. Observations also show that α and θ change between events, and, based on a recent analysis of 148 events, observations indicate that α and θ change because of corresponding changes in the depth, duration, and spatial variability of excess-rainfall. To improve our physical understanding of these observations, a 5-step framework for diagnosing observed power laws, or other space-time patterns in a basin, is articulated and applied to GCEW using a combination of analysis and numerical simulations. Diagnostic results indicate how the power laws are connected to physical conditions and processes. Derived expressions for α and θ show that if excess-rainfall depth is fixed then there is a decreasing concave relationship between α and excess-rainfall duration, and an increasing and slightly convex relationship between θ and excess rainfall duration. These trends are consistent with observations only when hillslope velocity vh is given a physically realistic value near 0.1 m/s. If vh ≫ 0.1 m/s, then the predicted trends deviate from observed trends. Results also suggest that trends in α and θ can be impacted by the dependence of vh and link velocity vl on excess-rainfall rate.

  13. Characteristics of extreme dust events observed over two urban areas in Iran

    NASA Astrophysics Data System (ADS)

    Bidokhti, Abbas-Ali A.; Gharaylou, Maryam; Pegahfar, Nafiseh; Sabetghadam, Samaneh; Rezazadeh, Maryam

    2016-03-01

    Determination of dust loading in the atmosphere is important not only from the public health point of view, but also for regional climate changes. The present study focuses on the characteristics of two major dust events for two urban areas in Iran, Kermanshah and Tehran, over the period of 4 years from 2006 to 2009. To detect extreme dust outbreaks, various datasets including synoptic data, dust concentration, reanalysis data and numerical results of WRF and HYSPLIT models were used. The weather maps demonstrate that for these events dusts are mainly generated when wind velocity is high and humidity is low in the lower troposphere and the region is under the influence of a thermal low. The event lasts until the atmospheric stability prevails and the surface wind speed weakens. The thermal low nature of the synoptic conditions of these major events is also responsible for deep boundary layer development with its thermals affecting the vertical dust flux over the region. Trajectory studies show that the dust events originated from deserts in Iraq and Syria and transported towards Iran. The main distinction between the two types of mobilizations seems to affect the dust concentrations in the Tehran urban area.

  14. Largest SEP events observed on board CORONAS-F satellite from august 2001

    NASA Astrophysics Data System (ADS)

    Kuznetsov, S.; Kudela, K.; Myagkova, I.; Podorolsky, A.; Ryumin, S.; Yushkov, B.

    The "CORONAS-F" satellite, the second one of CORONAS satellite series, was launched on July 31, 2001 into a circular orbit with a titude 507+/-21 km and 82.5ol inclination. The satellite was oriented towards the Sun and was equipped with the set of instruments for studies of solar flares and corresponding solar energetic particle (SEP) events. These instruments are intended for different energetic particles measurements - electrons 0.3-112 MeV, protons 1 90 MeV, alpha particles 23-35- MeV/n, CNO (up to Mg) nuclei 3 30 MeV/n. All charged particle detectors were- oriented in the anti-Sunward direction. One of the instrument, SONG, was developed in cooperation of the Institutes (1) and (2). During time interval from August 14, 2001 (when we began to receive the data) to March 2002 more than ten solar flares leading to SEP were observed in different experiments. We have analyzed three most intensive SEP events, namely those observed after solar flares in September, 24, November, 4, and 23, 2001. We obtained SEP fluxes detected by "CORONAS-F" satellite in the polar caps, where it was during about 15 minutes every 47 minutes, and compared these data with GOES and ACE satellites ones. SEP generation and distribution were analyzed in view of conditions in the near-Earth interplanetary space. November 4 event is compared with ground based neutron monitor measurements (GLE62). Solar flare events September, 24 and November, 4 have taken place near to the central solar meridian. Flares September, 24 and November, 4 have generated CME and the powerful bow shock with an initial velocity about 1500-2000 km/s. Besides that the bow shock, generated by November, 4 event during CME propagation, interacted with CME ejected during November, 1 event. The event November, 22 was possibly connected with two flares observed with the time lag about three hours near to the western limb and have generated two interacting CME. The bow shock velocity in this event was also estimated about 2000

  15. Mutual Events of the Uranian Satellites Observed with the Faulkes Telescopes

    NASA Astrophysics Data System (ADS)

    Christou, Apostolos; Lewis, F.; Hidas, M. G.; Brown, T. M.; Roche, P.

    2008-09-01

    The 2007 Uranian Equinox allowed unique observations of the planet, its rings and satellites, possible only twice during the planet's 84 year orbit. Among these were mutual eclipses and occultations between the 5 classical satellites Ariel, Umbriel, Titania, Oberon and Miranda. These ``mutual'' events are extremely useful as reality checks of satellite ephemerides. In addition, they provide an opportunity to improve our knowledge of the satellite orbits and the system constants. We observed several mutual events in 2007 using the 2m Faulkes Telescopes North (FTN) and South (FTS) located in Haleakala, Maui and Siding Spring, Australia respectively, operated by the Las Cumbres Observatory Global Telescope (LCOGT) network. To mitigate against Uranus' glare, we utilized wide-band imaging in the near-IR, a small image scale and a posteriori subtraction of the planet's PSF. We obtained positive detections of six mutual events, three occultations and three eclipses, among these satellites. Three of these events involved Miranda, a difficult target due to its proximity to Uranus. Furthermore, we recorded at least two events that were predicted to occur with high confidence but did not, in fact, occur. During this presentation we will describe our observing strategy, operational setup and data reduction techniques and present examples of obtained lightcurves. Our observational results have been compared with predictions based on ephemerides by Laskar and Jacobson (1987; GUST86), by Lainey and Arlot (2006; LA06) and by Rush and Jacobson (2007; RJ07). Offsets with respect to the Voyager-era GUST86 are quite significant, of the order of minutes in the event midtimes. Smaller, yet significant trends in the data also appear with respect to LA06 and RJ07. We will discuss the nature of these trends and how they can be interpreted in terms of potential improvements in our knowledge of the Uranian system.

  16. Pregnancy outcome in patients with antiphospholipid syndrome after cerebral ischaemic events: an observational study.

    PubMed

    Fischer-Betz, R; Specker, C; Brinks, R; Schneider, M

    2012-10-01

    Among the most prominent features associated with antiphospholipid syndrome (APS) are cerebral ischaemic events (CVE). Pregnancy with APS increases the risk of thrombosis, including CVE. This study was undertaken to assess the risk of obstetric complications and recurrence of CVE during pregnancy in women with APS and previous CVE. We prospectively observed 23 pregnancies in 20 women (median age 31 years) with primary (n = 8) or secondary APS (n = 12). Eight patients had transient ischaemic attacks (TIA) and 12 had stroke before pregnancy. All patients received aspirin 100 mg daily in combination with low molecular weight heparin (LMWH) during their pregnancies. The live birth rate was 91.3% (n = 21). Obstetrical complications consisted mainly of preeclampsia (n = 8, 34.8%) and preterm delivery (n = 9, 42.9%). The risk for preeclampsia increased in patients who were positive for multiple antiphospholipid antibodies (aPL) (odds ratio (OR) 3.06 (95% confidence interval (CI) 1.01-9.32)) per positive aPL test (i.e anticardiolipin antibody, anti-ß2-glycoprotein I antibody, lupus anticoagulant) (p 0.049). Three patients experienced recurrent CVE in the context of pregnancy (one during pregnancy, two in the postpartum period). We found an increased, but not significant, risk of a new episode of cerebral ischaemia in patients with pregnancies complicated by preeclampsia (two out of the eight preeclampsia (p 0.15). Despite treatment, there is a significant risk for pregnancy complications in APS patients with previous CVE. Especially in the context of preeclampsia, anticoagulation should be given rigorously to prevent recurrence of CVE.

  17. BEACHES: An Observational System for Assessing Children's Eating and Physical Activity Behaviors and Associated Events.

    ERIC Educational Resources Information Center

    McKenzie, Thomas L.; And Others

    1991-01-01

    The Behaviors of Eating and Activity for Children's Health Evaluation System (BEACHES) codes direct observations of children's dietary and physical activity behaviors and associated environmental events, including physical location, antecedents, and consequences. The system's reliability and validity was assessed in a study of 42 children (ages…

  18. Transition Region Explosive Events in He II 304Å: Observation and Analysis

    NASA Astrophysics Data System (ADS)

    Rust, Thomas; Kankelborg, Charles C.

    2016-05-01

    We present examples of transition region explosive events observed in the He II 304Å spectral line with the Multi Order Solar EUV Spectrograph (MOSES). With small (<5000 km) spatial scale and large non-thermal (100-150 km/s) velocities these events satisfy the observational signatures of transition region explosive events. Derived line profiles show distinct blue and red velocity components with very little broadening of either component. We observe little to no emission from low velocity plasma, making the plasmoid instability reconnection model unlikely as the plasma acceleration mechanism for these events. Rather, the single speed, bi-directional jet characteristics suggested by these data are consistent with acceleration via Petschek reconnection.Observations were made during the first sounding rocket flight of MOSES in 2006. MOSES forms images in 3 orders of a concave diffraction grating. Multilayer coatings largely restrict the passband to the He II 303.8Å and Si XI 303.3Å spectral lines. The angular field of view is about 8.5'x17', or about 20% of the solar disk. These images constitute projections of the volume I(x,y,λ), the intensity as a function of sky plane position and wavelength. Spectral line profiles are recovered via tomographic inversion of these projections. Inversion is carried out using a multiplicative algebraic reconstruction technique.

  19. Acceleration of a Static Observer Near the Event Horizon of a Static Isolated Black Hole.

    ERIC Educational Resources Information Center

    Doughty, Noel A.

    1981-01-01

    Compares the magnitude of the proper acceleration of a static observer in a static, isolated, spherically symmetric space-time region with the Newtonian result including the situation in the interior of a perfect-fluid star. This provides a simple physical interpretation of surface gravity and illustrates the global nature of the event horizon.…

  20. Effect of initial conditions and of intra-event rainfall intensity variability on shallow landslide triggering return period

    NASA Astrophysics Data System (ADS)

    Peres, David Johnny; Cancelliere, Antonino

    2016-04-01

    Assessment of shallow landslide hazard is important for appropriate planning of mitigation measures. Generally, return period of slope instability is assumed as a quantitative metric to map landslide triggering hazard on a catchment. The most commonly applied approach to estimate such return period consists in coupling a physically-based landslide triggering model (hydrological and slope stability) with rainfall intensity-duration-frequency (IDF) curves. Among the drawbacks of such an approach, the following assumptions may be mentioned: (1) prefixed initial conditions, with no regard to their probability of occurrence, and (2) constant intensity-hyetographs. In our work we propose the use of a Monte Carlo simulation approach in order to investigate the effects of the two above mentioned assumptions. The approach is based on coupling a physically based hydrological and slope stability model with a stochastic rainfall time series generator. By this methodology a long series of synthetic rainfall data can be generated and given as input to a landslide triggering physically based model, in order to compute the return period of landslide triggering as the mean inter-arrival time of a factor of safety less than one. In particular, we couple the Neyman-Scott rectangular pulses model for hourly rainfall generation and the TRIGRS v.2 unsaturated model for the computation of transient response to individual rainfall events. Initial conditions are computed by a water table recession model that links initial conditions at a given event to the final response at the preceding event, thus taking into account variable inter-arrival time between storms. One-thousand years of synthetic hourly rainfall are generated to estimate return periods up to 100 years. Applications are first carried out to map landslide triggering hazard in the Loco catchment, located in highly landslide-prone area of the Peloritani Mountains, Sicily, Italy. Then a set of additional simulations are performed

  1. Gaseous elemental mercury depletion events observed at Cape Point during 2007-2008

    NASA Astrophysics Data System (ADS)

    Brunke, E.-G.; Labuschagne, C.; Ebinghaus, R.; Kock, H. H.; Slemr, F.

    2010-02-01

    Gaseous mercury in the marine boundary layer has been measured with a 15 min temporal resolution at the Global Atmosphere Watch station Cape Point since March 2007. The most prominent features of the data until July 2008 are the frequent occurrences of pollution (PEs) and depletion events (DEs). Both types of events originate mostly within a short transport distance (up to about 100 km), which are embedded in air masses ranging from marine background to continental. The Hg/CO emission ratios observed during the PEs are within the range reported for biomass burning and industrial/urban emissions. The depletion of gaseous mercury during the DEs is in many cases almost complete and suggests an atmospheric residence time of elemental mercury as short as a few dozens of hours, which is in contrast to the commonly used estimate of approximately 1 year. The DEs observed at Cape Point are not accompanied by simultaneous depletion of ozone which distinguishes them from the halogen driven atmospheric mercury depletion events (AMDEs) observed in Polar Regions. Nonetheless, DEs similar to those observed at Cape Point have also been observed at other places in the marine boundary layer. Additional measurements of mercury speciation and of possible mercury oxidants are hence called for to reveal the chemical mechanism of the newly observed DEs and to assess its importance on larger scales.

  2. International Observe the Moon Night: Using Public Outreach Events to Tell Your Story to the Public

    NASA Astrophysics Data System (ADS)

    Hsu, B. C.; International Observe the Moon Night Coordinating Committee

    2011-12-01

    From various interpretations of the lunar "face," early pictograms of the Moon's phases, or to the use of the lunar cycle for festivals or harvests, the Moon has an undeniable influence on human civilization. International Observe the Moon Night (InOMN) capitalizes on the human connection to the Moon by engaging the public in annual lunar observation campaigns that share the excitement of lunar science and exploration. In 2010 (InOMN's inaugural year), over 500,000 people attended events in 53 countries around the world. About 68% of InOMN hosts - astronomy clubs, museums, schools, or other groups - used the resources on the InOMN website (http://observethemoonnight.org). The InOMN website provided supporting materials for InOMN event hosts in the form of downloadable advertising materials, Moon maps, suggestions for hands-on educational activities, and links to lunar science content. InOMN event participants shared their experiences with the world using the Web and social media, event hosts shared their experiences with evaluation data, and amateur astronomers and photographers shared their images of the Moon through the lunar photography contest. The overwhelming response from InOMN in 2010 represents an untapped potential for infusing cutting edge lunar science and exploration into a large-scale public outreach event.

  3. Estimating the Period and Q of the Chandler Wobble from Observations and Models of its Excitation

    NASA Astrophysics Data System (ADS)

    Gross, R. S.; Nastula, J.

    2012-12-01

    Any irregularly shaped solid body rotating about some axis that is not aligned with its figure axis will freely wobble as it rotates. For the Earth, this free wobble is known as the Chandler wobble in honor of S. C. Chandler, Jr. who first observed it in 1891. Unlike the forced wobbles of the Earth, such as the annual wobble, whose periods are the same as the periods of the forcing mechanisms, the period of the free Chandler wobble is a function of the internal structure and rheology of the Earth, and its decay time constant, or quality factor Q, is a function of the dissipation mechanism(s), like mantle anelasticity, that are acting to dampen it. Improved estimates of the period and Q of the Chandler wobble can therefore be used to improve our understanding of these properties of the Earth. Here, estimates of the period and Q of the Chandler wobble are obtained by finding those values that minimize the power within the Chandler band of the difference between observed and modeled polar motion excitation spanning 1962-2010. Atmosphere, ocean, and hydrology models are used to model the excitation caused by both mass and motion variations within these global geophysical fluids. Direct observations of the excitation caused by mass variations as determined from GRACE time varying gravitational field measurements are also used. The resulting estimates of the period and Q of the Chandler wobble will be presented along with a discussion of the robustness of the estimates.

  4. Estimating the Period and Q of the Chandler Wobble from Observations and Models of its Excitation

    NASA Astrophysics Data System (ADS)

    Gross, R. S.; Nastula, J.

    2014-12-01

    Any irregularly shaped solid body rotating about some axis that is not aligned with its figure axis will freely wobble as it rotates. For the Earth, this free wobble is known as the Chandler wobble in honor of S. C. Chandler, Jr. who first observed it in 1891. Unlike the forced wobbles of the Earth, such as the annual wobble, whose periods are the same as the periods of the forcing mechanisms, the period of the free Chandler wobble is a function of the internal structure and rheology of the Earth, and its decay time constant, or quality factor Q, is a function of the dissipation mechanism(s), like mantle anelasticity, that are acting to dampen it. Improved estimates of the period and Q of the Chandler wobble can therefore be used to improve our understanding of these properties of the Earth. Here, estimates of the period and Q of the Chandler wobble are obtained by finding those values that minimize the power within the Chandler band of the difference between observed and modeled polar motion excitation spanning 1962-2010. Atmosphere, ocean, and hydrology models are used to model the excitation caused by both mass and motion variations within these global geophysical fluids. Direct observations of the excitation caused by mass variations as determined from GRACE time varying gravitational field measurements are also used. The resulting estimates of the period and Q of the Chandler wobble will be presented along with a discussion of the robustness of the estimates.

  5. On the Mechanisms Producing Iceberg Discharges During Last Glacial Period, Including Heinrich Events

    NASA Astrophysics Data System (ADS)

    Alvarez-Solas, J.; Robinson, A.; Banderas, R.; Montoya, M.

    2014-12-01

    Proxy data reveal the existence of episodes of increased deposition of ice-rafted debris in the North Atlantic Ocean during the last glacial period. These are interpreted as massive iceberg discharges mainly from the Laurentide Ice Sheet. Although these have long been attributed to self-sustained ice sheet oscillations, growing evidence points to an active role of the oceanic circulation. Here we present simulations of the last glacial period carried out with a hybrid ice sheet-ice shelf model. Two mechanisms producing iceberg discharges are compared. First, we reproduce the classic binge-purge by which the iceberg surges are produced thanks to the existence of an internal thermo-mechanical feedback that allows the ice sheet to behave under an oscillatory regime. Second, our ice-sheet model is forced by an oceanic warming index derived from proxy data that accounts for the impact of past ocean circulation changes on ocean temperatures. In this case, the model generates a time series of iceberg calving that agrees with ice-rafted debris records over the past 80 ka. We compare the two theories and discuss their advantages and weaknesses in terms of both the robustness of the physics on which they are based and their comparison with proxies.

  6. The effects of 8 Helios observed solar proton events of interplanetary magnetic field fluctuations

    NASA Technical Reports Server (NTRS)

    ValdezGalicia, J. F.; Alexander, P.; Otaola, J. A.

    1995-01-01

    There have been recent suggestions that large fluxes during solar energetic particle events may produce their own turbulence. To verify this argument it becomes essential to find out whether these flows cause an enhancement of interplanetary magnetic field fluctuations. In the present work, power and helicity spectra of the IMF before, during and after 8 Helios-observed solar proton events in the range 0.3 - 1 AU are analyzed. In order to detect proton self generated waves, the time evolution of spectra are followed.

  7. Analyzing the Energetics of Explosive Events Observed by SUMER on SOHO

    NASA Astrophysics Data System (ADS)

    Winebarger, Amy R.; Emslie, A. Gordon; Mariska, John T.; Warren, Harry P.

    1999-11-01

    The SUMER spectrometer on SOHO has obtained numerous observations of optically thin chromosphere-corona transition-region line profiles with high spatial, spectral, and temporal resolution. Many of these profiles exhibit asymmetries and broadenings associated with impulsive mass motions (explosive events) in the solar atmosphere. We present here a new method of analyzing non-Gaussian line profiles to calculate the distribution of fluid velocities and hence the associated energy flux. We illustrate this method through a preliminary analysis of explosive event line profiles observed by SUMER. We derive the magnitudes of the energy fluxes directed both toward and away from the observer, and their (``net flux'') differences. We also identify and quantify the various components of each (i.e., kinetic, thermal and nonthermal enthalpy, and the high-energy component associated with the skewed tail of the distribution). The global energy contribution of explosive events to the solar atmosphere is then estimated under two different ``grouping'' assumptions. This preliminary analysis reveals an average net upward energy flux over the entire Sun of 104-105 ergs cm-2 s-1, up to an order of magnitude larger than previous estimates based on characteristic velocities of the fluid. Furthermore, the global estimate for the separate upward- and downward-directed energy fluxes is 105-106 ergs cm-2 s-1, which is comparable to the energy flux required for heating of the quiet corona and indicates that explosive events may indeed have significant implications for the energy balance of the chromosphere and corona.

  8. Multi-Spacecraft Observations of the Longitudinal Properties of Solar Energetic Particle Events

    NASA Astrophysics Data System (ADS)

    Mewaldt, R. A.; Cohen, C. M.; Mason, G. M.; von Rosenvinge, T. T.; Gomez-Herrero, R.; Vourlidas, A.; Wiedenbeck, M. E.

    2012-12-01

    During the recent rise in solar activity, the twin STEREO spacecraft, in combination with near-Earth assets (e.g., ACE, GOES, RHESSI, SDO, SOHO, and Wind) have provided ~360° coverage of solar energetic particle (SEP) events, coronal mass ejections (CMEs), shocks, and other aspects of solar eruptions. This combination has provided an unprecedented opportunity to observe how the properties of SEP events vary with longitude. Initial results indicate that particles are distributed in longitude more easily than was earlier appreciated. Indeed, most recent large SEP events associated with CME-driven shocks are observed by both STEREOs and ACE, even as these spacecraft are separated by >100° in longitude. This talk will discuss longitudinal, intensity, composition, and spectral variations of large SEP events and compare them with models and previous studies. Small 3He-rich flares associated with flares and coronal jets are also found to be distributed more broadly in longitude than reported in single-point studies. Recent observations, issues, and proposed explanations for SEP longitudinal variations will be reviewed.

  9. C3Winds: A Novel 3D Wind Observing System to Characterize Severe Weather Events

    NASA Astrophysics Data System (ADS)

    Kelly, M. A.; Wu, D. L.; Yee, J. H.; Boldt, J.; Demajistre, R.; Reynolds, E.; Tripoli, G. J.; Oman, L.; Prive, N.; Heidinger, A. K.; Wanzong, S.

    2015-12-01

    The CubeSat Constellation Cloud Winds (C3Winds) is a NASA Earth Venture Instrument (EV-I) concept with the primary objective to resolve high-resolution 3D dynamic structures of severe wind events. Rapid evolution of severe weather events highlights the need for high-resolution mesoscale wind observations. Yet mesoscale observations of severe weather dynamics are quite rare, especially over the ocean where extratropical and tropical cyclones (ETCs and TCs) can undergo explosive development. Measuring wind velocity at the mesoscale from space remains a great challenge, but is critically needed to understand and improve prediction of severe weather and tropical cyclones. Based on compact, visible/IR imagers and a mature stereoscopic technique, C3Winds has the capability to measure high-resolution (~2 km) cloud motion vectors and cloud geometric heights accurately by tracking cloud features from two formation-flying CubeSats, separated by 5-15 minutes. Complementary to lidar wind measurements from space, C3Winds will provide high-resolution wind fields needed for detailed investigations of severe wind events in occluded ETCs, rotational structures inside TC eyewalls, and ozone injections associated with tropopause folding events. Built upon mature imaging technologies and long history of stereoscopic remote sensing, C3Winds provides an innovative, cost-effective solution to global wind observations with the potential for increased diurnal sampling via CubeSat constellation.

  10. Partitioning of integrated energy fluxes in four tail reconnection events observed by Cluster

    NASA Astrophysics Data System (ADS)

    Tyler, Evan; Cattell, Cynthia; Thaller, Scott; Wygant, John; Gurgiolo, Chris; Goldstein, Melvyn; Mouikis, Christopher

    2016-12-01

    We present the partitioning of integrated energy flux from four tail reconnection events observed by Cluster, focusing on the relative contributions of Poynting flux, electron, H+ and O+ enthalpy, and kinetic energy flux in the tailward and earthward directions in order to study temporal and spatial features of each event. We further subdivide the Poynting flux into three frequency bands to examine the possible structures and waves that contribute most significantly to the total Poynting flux from the reconnection region. Our results indicate that H+ enthalpy flux is often dominant, but O+ enthalpy, electron enthalpy, Poynting flux, and H+ kinetic energy flux can contribute significant or greater total energy flux depending on spacecraft location with respect the current sheet, flow direction, temporal scale, and local conditions. We observe integrated H+ enthalpy fluxes that differ by factors of 3-4 between satellites, even over ion inertial length scales. We observe strong differences in behavior between H+ and O+ enthalpy fluxes in all events, highlighting the importance of species-specific energization mechanisms. We find tailward-earthward asymmetry in H+ enthalpy flux, possibly indicative of the influence of the closed earthward boundary of the magnetotail system. Frequency filtering of the Poynting flux shows that current sheet surface waves and structures on the timescale of current sheet flapping contribute significantly, while large-scale structure contributions are relatively small. We observe that the direction and behavior of the Poynting flux differs between bands, indicating that the observed flux originates from multiple distinct sources or processes.

  11. Visual search is postponed during the period of the AB: An event-related potential study.

    PubMed

    Lagroix, Hayley E P; Grubert, Anna; Spalek, Thomas M; Di Lollo, Vincent; Eimer, Martin

    2015-08-01

    In the phenomenon known as the attentional blink (AB), perception of the second of two rapidly sequential targets (T2) is impaired when presented shortly after the first (T1). Studies in which T2 consisted of a pop-out search array provided evidence suggesting that visual search is postponed during the AB. In the present work, we used behavioral and electrophysiological measures to test this postponement hypothesis. The behavioral measure was reaction time (RT) to T2; the electrophysiological measure was the onset latency of an ERP index of attentional selection, known as the N2pc. Consistent with the postponement hypothesis, both measures were delayed during the AB. The delay in N2pc was substantially shorter than that in RT, pointing to multiple sources of delay in the chain of processing events, as distinct from the single source postulated in current theories of the AB. Finally, the finding that the N2pc was delayed during the AB strongly suggests that attention is involved in the processing of pop-out search arrays.

  12. Periodizing heat acclimation in elite Laser sailors preparing for a world championship event in hot conditions

    PubMed Central

    Casadio, Julia R.; Kilding, Andrew E.; Siegel, Rodney; Cotter, James D.; Laursen, Paul B.

    2016-01-01

    ABSTRACT Purpose: To examine the retention and re-acclimation responses during a periodized heat acclimation (HA) protocol in elite sailors preparing for the 2013 World Championships in Muscat, Oman (∼27–30°C, 40–60% RH). Methods: Two elite male Laser class sailors completed 5 consecutive days of HA (60 min per day in 35°C, 60% RH). Heat response tests (HRT) were performed on day 1 and 5 of HA, then 1 (decay 1, D1) and 2 (D2) weeks following HA. Participants were then re-acclimated (RA) for 2 days, within the next week, before a final HRT ∼72 h post-RA. Rectal temperature, plasma volume, heart rate, sweat rate, as well as thermal discomfort and rating of perceived exertion were measured during each HRT. Results: Rectal temperature decreased with HA (0.46 ± 0.05°C), while individual responses following D1, D2 and RA varied. Heart rate (14 ± 7 bpm), thermal discomfort (0.6 ± 0.1 AU) and rating of perceived exertion (1.8 ± 0.6 AU) decreased across HA, and adaptations were retained by D2. Plasma volume steadily increased over the decay period (D2 = 8.0 ± 1.3%) and after RA (15.5 ± 1.1%) compared with baseline. RA resulted in further thermoregulatory improvements in each Athlete, although individual adjustments varied. Conclusion: Heat strain was reduced in elite Laser sailors following HA and most thermoregulatory adaptations were retained for 2 weeks afterwards. RA may ‘top up’ adaptations after 2 weeks of HA decay. PMID:28349083

  13. Analysis of C3 Suggests Three Periods of Positive Selection Events and Different Evolutionary Patterns between Fish and Mammals

    PubMed Central

    Meng, Fanxing; Sun, Yuena; Liu, Xuezhu; Wang, Jianxin; Xu, Tianjun; Wang, Rixin

    2012-01-01

    Background The third complement component (C3) is a central protein of the complement system conserved from fish to mammals. It also showed distinct characteristics in different animal groups. Striking features of the fish complement system were unveiled, including prominent levels of extrahepatic expression and isotypic diversity of the complement components. The evidences of the involvement of complement system in the enhancement of B and T cell responses found in mammals indicated that the complement system also serves as a bridge between the innate and adaptive responses. For the reasons mentioned above, it is interesting to explore the evolutionary process of C3 genes and to investigate whether the huge differences between aquatic and terrestrial environments affected the C3 evolution between fish and mammals. Methodology/Principal Findings Analysis revealed that these two groups of animals had experienced different evolution patterns. The mammalian C3 genes were under purifying selection pressure while the positive selection pressure was detected in fish C3 genes. Three periods of positive selection events of C3 genes were also detected. Two happened on the ancestral lineages to all vertebrates and mammals, respectively, one happened on early period of fish evolutionary history. Conclusions/Significance Three periods of positive selection events had happened on C3 genes during history and the fish and mammals C3 genes experience different evolutionary patterns for their distinct living environments. PMID:22624039

  14. Quasi-Periodicities in the Anomalous Emission Events in Pulsars B1859+07 and B0919+06

    NASA Astrophysics Data System (ADS)

    Wahl, Haley; Rankin, Joanna M.

    2017-01-01

    A quasi-periodicity has been identified in the strange emission shifts in pulsar B1859+07 and possibly B0919+06. These events, first investigated by Rankin, Rodriguez & Wright in 2006, originally appeared disordered or random, but further mapping as well as Fourier analysis has revealed that they occur on a fairly regular basis of approximately 150 rotation periods in B1859+07 and perhaps some 700 in B0919+06. The events-which we now refer to as "swooshes"-are not the result of any known type of mode-changing, but rather we find that they are a uniquely different effect, produced by some mechanism other than any known pulse-modulation phenomenon. Given that we have yet to find another explanation for the swooshes, we have appealed to a last resort for periodicities in astrophysics: orbital dynamics in a binary system. Such putative "companions" would then have semi-major axes comparable to the light cylinder radius for both pulsars. However, in order to resist tidal disruption their densities must be at least some 10^5 grams/cm^3-therefore white-dwarf cores or something even denser might be indicated.

  15. Quasi-periodicities in the anomalous emission events in pulsars B1859+07 and B0919+06

    NASA Astrophysics Data System (ADS)

    Wahl, Haley M.; Orfeo, Daniel J.; Rankin, Joanna M.; Weisberg, Joel M.

    2016-10-01

    A quasi-periodicity has been identified in the strange emission shifts in pulsar B1859+07 and possibly B0919+06. These events, first investigated by Rankin, Rodriguez & Wright in 2006, originally appeared disordered or random, but further mapping as well as Fourier analysis has revealed that they occur on a fairly regular basis of approximately 150 rotation periods in B1859+07 and perhaps some 700 in B0919+06. The events - which we now refer to as `swooshes' - are not the result of any known type of mode-changing, but rather we find that they are a uniquely different effect, produced by some mechanism other than any known pulse-modulation phenomenon. Given that we have yet to find another explanation for the swooshes, we have appealed to a last resort for periodicities in astrophysics: orbital dynamics in a binary system. Such putative `companions' would then have semimajor axes comparable to the light cylinder radius for both pulsars. However, in order to resist tidal disruption, their densities must be at least some 105 g cm-3 - therefore, white-dwarf cores or something even denser might be indicated.

  16. Multi-spacecraft Observations and Transport Modeling of Energetic Electrons for a Series of Solar Particle Events in August 2010

    NASA Astrophysics Data System (ADS)

    Dröge, W.; Kartavykh, Y. Y.; Dresing, N.; Klassen, A.

    2016-08-01

    During 2010 August a series of solar particle events was observed by the two STEREO spacecraft as well as near-Earth spacecraft. The events, occurring on August 7, 14, and 18, originated from active regions 11093 and 11099. We combine in situ and remote-sensing observations with predictions from our model of three-dimensional anisotropic particle propagation in order to investigate the physical processes that caused the large angular spreads of energetic electrons during these events. In particular, we address the effects of the lateral transport of the electrons in the solar corona that is due to diffusion perpendicular to the average magnetic field in the interplanetary medium. We also study the influence of two coronal mass ejections and associated shock waves on the electron propagation, and a possible time variation of the transport conditions during the above period. For the August 18 event we also utilize electron observations from the MESSENGER spacecraft at a distance of 0.31 au from the Sun for an attempt to separate between radial and longitudinal dependencies in the transport process. Our modelings show that the parallel and perpendicular diffusion mean free paths of electrons can vary significantly not only as a function of the radial distance, but also of the heliospheric longitude. Normalized to a distance of 1 au, we derive values of λ ∥ in the range of 0.15-0.6 au, and values of λ ⊥ in the range of 0.005-0.01 au. We discuss how our results relate to various theoretical models for perpendicular diffusion, and whether there might be a functional relationship between the perpendicular and the parallel mean free path.

  17. Two long-term slow slip events around Tokyo Bay found by GNSS observation during 1996-2011

    NASA Astrophysics Data System (ADS)

    Tanaka, Yoshiyuki; Yabe, Suguru

    2017-03-01

    Slow slip events (SSEs) with durations ranging from days to more than a decade have been observed in plate subduction zones around the world. In the Kanto district in Japan, several SSEs have been identified based on geodetic observations. However, none of these events have had durations largely exceeding a year. In this study, we show that long-term SSEs with durations longer than 3 years occurred before the year 2000 and after 2007 on the upper interface of the Philippine Sea Plate at depths of 30-40 km. The fault model determined by inversion of global navigation satellite system data is located northeast of Tokyo Bay, where a seismic gap and low seismic wave velocities were detected by seismological observations. Moreover, the acceleration periods of the fault slip corresponded well with increases in the background seismicity for shallower earthquakes. The slip history was also temporally correlated with the long-term shear stress changes governed mainly by non-tidal variations in the ocean bottom pressure. However, the predicted slip from the long-term stress change was too small to reproduce the observed slow slips. To prove the causal relationship between the SSEs and the external stress change, more advanced modeling is necessary to confirm whether such a small slip can trigger an SSE.[Figure not available: see fulltext.

  18. Systematic observations of long-range transport events and climatological backscatter profiles with the DWD ceilometer network

    NASA Astrophysics Data System (ADS)

    Mattis, Ina; Müller, Gerhard; Wagner, Frank; Hervo, Maxime

    2015-04-01

    The German Meteorological Service (DWD) operates a network of about 60 CHM15K-Nimbus ceilometers for cloud base height observations. Those very powerful ceilometers allow for the detection and characterization of aerosol layers. Raw data of all network ceilometers are transferred online to DWD's data analysis center at the Hohenpeißenberg Meteorological Observatory. There, the occurrence of aerosol layers from long-range transport events in the free troposphere is systematically monitored on daily basis for each single station. If possible, the origin of the aerosol layers is determined manually from the analysis of the meteorological situation and model output. We use backward trajectories as well as the output of the MACC and DREAM models for the decision, whether the observed layer originated in the Sahara region, from forest fires in North America or from another, unknown source. Further, the magnitude of the observed layers is qualitatively estimated taking into account the geometrical layer depth, signal intensity, model output and nearby sun photometer or lidar observations (where available). All observed layers are attributed to one of the categories 'faint', 'weak', 'medium', 'strong', or 'extreme'. We started this kind of analysis in August 2013 and plan to continue this systematic documentation of long-range transport events of aerosol layers to Germany on long-term base in the framework of our GAW activities. Most of the observed aerosol layers have been advected from the Sahara region to Germany. In the 15 months between August 2013 and November 2014 we observed on average 46 days with Sahara dust layers per station, but only 16 days with aerosol layers from forest fires. The occurrence of Sahara dust layers vary with latitude. We observed only 28 dusty days in the north, close to the coasts of North Sea and Baltic Sea. In contrast, in southern Germany, in Bavarian Pre-Alps and in the Black Forest mountains, we observed up to 59 days with dust. At

  19. Total Lightning Observations of Extreme Weather Events over the Contiguous United States

    NASA Technical Reports Server (NTRS)

    Carey, Lawrence D.; Petersen, Walter A.; Christian, Hugh J.

    2008-01-01

    The overall objective is to investigate total lightning characteristics of extreme weather events over the contiguous United States (CONUS) using TRMM (Tropical Rainfall Measuring Mission) LIS (Lightning Image Sensor) and OTD (Optical Transient Detector) satellite observations. A large LIS (10+ years) and OTD (5 years) data base is available to study the instantaneous total or cloud-to-ground (CG) plus intracloud (IC) lightning characteristics of extreme weather events. More specifically, the LIS and OTD data are combined with National Lightning Detection Network (NLDN) observations to examine the total and CG lightning flash rate and density, the IC:CG ratio, and positive CG percentage. These instantaneous lightning characteristics can be used for basic science studies to better understand the physical and dynamical linkages between lightning and precipitation and their environmental controls. They can also provide a first-look of extreme weather events leading up to future satellite observations (e.g., NOAA GOES-R Geostationary Lightning Mapper [GLM]) for use in climate studies and the short-term prediction and warning process. Extreme weather events are defined by the NOAA Storm Data reports of tornadoes, large hail (at least 0.75 inch) and strong straight-line winds (at least 50 kts). Over CONUS, there are over 70,000 severe storm reports in the TRMM spatial domain (< 35 N) from 1998-2007 and over 100,000 storm reports in the OTD spatial domain (5/1995-4/2000). Temporal co-location is on the order of 1% (i.e., 1000 s of coincident overpasses), providing a statistically significant sample of instantaneous total lightning properties. This instantaneous behavior of lightning in extreme weather is then compared to that of typical thunderstorm events, or randomly sampled LIS/OTD events in which the extreme events have been eliminated from the population. Results describing the instantaneous behavior of total lightning within a large sample of extreme and typical

  20. Esthetic restorations: observations and insights gained over a 5-year period demonstrated with three case reports.

    PubMed

    Obama, Tadakazu

    2007-01-01

    This article presents two prosthodontically treated patient cases that were observed over a period of at least 5 years after treatment. The evaluation, diagnosis, treatment planning, and treatment stages were critically reviewed and reassessed from different perspectives. The conclusions drawn from this evaluation were subsequently implemented in a third clinical case. To ensure the long-term success of a restoration, certain biologic and mechanical principles must be observed, and the appropriate prosthodontic treatment must be chosen accordingly.

  1. A Transition Region Explosive Event Observed in He II with the MOSES Sounding Rocket

    NASA Astrophysics Data System (ADS)

    Fox, J. Lewis; Kankelborg, Charles C.; Thomas, Roger J.

    2010-08-01

    Transition region explosive events (EEs) have been observed with slit spectrographs since at least 1975, most commonly in lines of C IV (1548 Å, 1550 Å) and Si IV (1393 Å, 1402 Å). We report what we believe to be the first observation of a transition region EE in He II 304 Å. With the Multi-Order Solar EUV Spectrograph (MOSES) sounding rocket, a novel slitless imaging spectrograph, we are able to see the spatial structure of the event. We observe a bright core expelling two jets that are distinctly non-collinear, in directions that are not anti-parallel. The jets have sky-plane velocities of order 75 km s-1 and line-of-sight velocities of +75 km s-1 (blue) and -30 km s-1 (red). The core is a region of high non-thermal Doppler broadening, characteristic of EEs, with maximal broadening 380 km s-1 FWHM. It is possible to resolve the core broadening into red and blue line-of-sight components of maximum Doppler velocities +160 km s-1 and -220 km s-1. The event lasts more than 150 s. Its properties correspond to the larger, long-lived, and more energetic EEs observed in other wavelengths.

  2. Swift Follow-up Observations of Candidate Gravitational-wave Transient Events

    NASA Astrophysics Data System (ADS)

    Evans, P. A.; Fridriksson, J. K.; Gehrels, N.; Homan, J.; Osborne, J. P.; Siegel, M.; Beardmore, A.; Handbauer, P.; Gelbord, J.; Kennea, J. A.; Smith, M.; Zhu, Q.; LIGO Scientific Collaboration; Virgo Collaboration; Aasi, J.; Abadie, J.; Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M.; Accadia, T.; Acernese, F.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Ajith, P.; Allen, B.; Allocca, A.; Amador Ceron, E.; Amariutei, D.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Ast, S.; Aston, S. M.; Astone, P.; Atkinson, D.; Aufmuth, P.; Aulbert, C.; Aylott, B. E.; Babak, S.; Baker, P.; Ballardin, G.; Ballmer, S.; Bao, Y.; Barayoga, J. C. B.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barton, M. A.; Bartos, I.; Bassiri, R.; Bastarrika, M.; Basti, A.; Batch, J.; Bauchrowitz, J.; Bauer, Th. S.; Bebronne, M.; Beck, D.; Behnke, B.; Bejger, M.; Beker, M. G.; Bell, A. S.; Bell, C.; Belopolski, I.; Benacquista, M.; Berliner, J. M.; Bertolini, A.; Betzwieser, J.; Beveridge, N.; Beyersdorf, P. T.; Bhadbade, T.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Biswas, R.; Bitossi, M.; Bizouard, M. A.; Black, E.; Blackburn, J. K.; Blackburn, L.; Blair, D.; Bland, B.; Blom, M.; Bock, O.; Bodiya, T. P.; Bogan, C.; Bond, C.; Bondarescu, R.; Bondu, F.; Bonelli, L.; Bonnand, R.; Bork, R.; Born, M.; Boschi, V.; Bose, S.; Bosi, L.; Bouhou, B.; Braccini, S.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Breyer, J.; Briant, T.; Bridges, D. O.; Brillet, A.; Brinkmann, M.; Brisson, V.; Britzger, M.; Brooks, A. F.; Brown, D. A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Burguet-Castell, J.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Calloni, E.; Camp, J. B.; Campsie, P.; Cannon, K.; Canuel, B.; Cao, J.; Capano, C. D.; Carbognani, F.; Carbone, L.; Caride, S.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C.; Cesarini, E.; Chalermsongsak, T.; Charlton, P.; Chassande-Mottin, E.; Chen, W.; Chen, X.; Chen, Y.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Chow, J.; Christensen, N.; Chua, S. S. Y.; Chung, C. T. Y.; Chung, S.; Ciani, G.; Clara, F.; Clark, D. E.; Clark, J. A.; Clayton, J. H.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colacino, C. N.; Colla, A.; Colombini, M.; Conte, A.; Conte, R.; Cook, D.; Corbitt, T. R.; Cordier, M.; Cornish, N.; Corsi, A.; Costa, C. A.; Coughlin, M.; Coulon, J.-P.; Couvares, P.; Coward, D. M.; Cowart, M.; Coyne, D. C.; Creighton, J. D. E.; Creighton, T. D.; Cruise, A. M.; Cumming, A.; Cunningham, L.; Cuoco, E.; Cutler, R. M.; Dahl, K.; Damjanic, M.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Dattilo, V.; Daudert, B.; Daveloza, H.; Davier, M.; Daw, E. J.; Day, R.; Dayanga, T.; De Rosa, R.; DeBra, D.; Debreczeni, G.; Degallaix, J.; Del Pozzo, W.; Dent, T.; Dergachev, V.; DeRosa, R.; Dhurandhar, S.; Di Fiore, L.; Di Lieto, A.; Di Palma, I.; Emilio, M. Di Paolo; Di Virgilio, A.; Díaz, M.; Dietz, A.; Donovan, F.; Dooley, K. L.; Doravari, S.; Dorsher, S.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Dumas, J.-C.; Dwyer, S.; Eberle, T.; Edgar, M.; Edwards, M.; Effler, A.; Ehrens, P.; Eikenberry, S.; Endrőczi, G.; Engel, R.; Etzel, T.; Evans, K.; Evans, M.; Evans, T.; Factourovich, M.; Fafone, V.; Fairhurst, S.; Farr, B. F.; Favata, M.; Fazi, D.; Fehrmann, H.; Feldbaum, D.; Ferrante, I.; Ferrini, F.; Fidecaro, F.; Finn, L. S.; Fiori, I.; Fisher, R. P.; Flaminio, R.; Foley, S.; Forsi, E.; Forte, L. A.; Fotopoulos, N.; Fournier, J.-D.; Franc, J.; Franco, S.; Frasca, S.; Frasconi, F.; Frede, M.; Frei, M. A.; Frei, Z.; Freise, A.; Frey, R.; Fricke, T. T.; Friedrich, D.; Fritschel, P.; Frolov, V. V.; Fujimoto, M.-K.; Fulda, P. J.; Fyffe, M.; Gair, J.; Galimberti, M.; Gammaitoni, L.; Garcia, J.; Garufi, F.; Gáspár, M. E.; Gelencser, G.; Gemme, G.; Genin, E.; Gennai, A.; Gergely, L. Á.; Ghosh, S.; Giaime, J. A.; Giampanis, S.; Giardina, K. D.; Giazotto, A.; Gil-Casanova, S.; Gill, C.; Gleason, J.; Goetz, E.; González, G.; Gorodetsky, M. L.; Goßler, S.; Gouaty, R.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gray, C.; Greenhalgh, R. J. S.; Gretarsson, A. M.; Griffo, C.; Grote, H.; Grover, K.; Grunewald, S.; Guidi, G. M.; Guido, C.; Gupta, R.; Gustafson, E. K.; Gustafson, R.; Hallam, J. M.; Hammer, D.; Hammond, G.; Hanks, J.; Hanna, C.; Hanson, J.; Harms, J.; Harry, G. M.; Harry, I. W.; Harstad, E. D.; Hartman, M. T.; Haughian, K.; Hayama, K.; Hayau, J.-F.; Heefner, J.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M. A.; Heng, I. S.; Heptonstall, A. W.; Herrera, V.; Heurs, M.; Hewitson, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Holt, K.; Holtrop, M.; Hong, T.; Hooper, S.; Hough, J.; Howell, E. J.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Ingram, D. R.; Inta, R.; Isogai, T.; Ivanov, A.; Izumi, K.; Jacobson, M.; James, E.; Jang, Y. J.; Jaranowski, P.; Jesse, E.; Johnson, W. W.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; Kalmus, P.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Kasprzack, M.; Kasturi, R.; Katsavounidis, E.; Katzman, W.; Kaufer, H.; Kaufman, K.; Kawabe, K.; Kawamura, S.; Kawazoe, F.; Keitel, D.; Kelley, D.; Kells, W.; Keppel, D. G.; Keresztes, Z.; Khalaidovski, A.; Khalili, F. Y.; Khazanov, E. A.; Kim, B. K.; Kim, C.; Kim, H.; Kim, K.; Kim, N.; Kim, Y. M.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Klimenko, S.; Kline, J.; Kokeyama, K.; Kondrashov, V.; Koranda, S.; Korth, W. Z.; Kowalska, I.; Kozak, D.; Kringel, V.; Krishnan, B.; Królak, A.; Kuehn, G.; Kumar, P.; Kumar, R.; Kurdyumov, R.; Kwee, P.; Lam, P. K.; Landry, M.; Langley, A.; Lantz, B.; Lastzka, N.; Lawrie, C.; Lazzarini, A.; Le Roux, A.; Leaci, P.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Leong, J. R.; Leonor, I.; Leroy, N.; Letendre, N.; Lhuillier, V.; Li, J.; Li, T. G. F.; Lindquist, P. E.; Litvine, V.; Liu, Y.; Liu, Z.; Lockerbie, N. A.; Lodhia, D.; Logue, J.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J.; Lubinski, M.; Lück, H.; Lundgren, A. P.; Macarthur, J.; Macdonald, E.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Mageswaran, M.; Mailand, K.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mandel, I.; Mandic, V.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A.; Maros, E.; Marque, J.; Martelli, F.; Martin, I. W.; Martin, R. M.; Marx, J. N.; Mason, K.; Masserot, A.; Matichard, F.; Matone, L.; Matzner, R. A.; Mavalvala, N.; Mazzolo, G.; McCarthy, R.; McClelland, D. E.; McDaniel, P.; McGuire, S. C.; McIntyre, G.; McIver, J.; Meadors, G. D.; Mehmet, M.; Meier, T.; Melatos, A.; Melissinos, A. C.; Mendell, G.; Menéndez, D. F.; Mercer, R. A.; Meshkov, S.; Messenger, C.; Meyer, M. S.; Miao, H.; Michel, C.; Milano, L.; Miller, J.; Minenkov, Y.; Mingarelli, C. M. F.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moe, B.; Mohan, M.; Mohapatra, S. R. P.; Moraru, D.; Moreno, G.; Morgado, N.; Morgia, A.; Mori, T.; Morriss, S. R.; Mosca, S.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, C. L.; Mueller, G.; Mukherjee, S.; Mullavey, A.; Müller-Ebhardt, H.; Munch, J.; Murphy, D.; Murray, P. G.; Mytidis, A.; Nash, T.; Naticchioni, L.; Necula, V.; Nelson, J.; Neri, I.; Newton, G.; Nguyen, T.; Nishizawa, A.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E.; Nuttall, L.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Oldenberg, R. G.; O'Reilly, B.; O'Shaughnessy, R.; Osthelder, C.; Ott, C. D.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Page, A.; Palladino, L.; Palomba, C.; Pan, Y.; Pankow, C.; Paoletti, F.; Paoletti, R.; Papa, M. A.; Parisi, M.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Pedraza, M.; Penn, S.; Perreca, A.; Persichetti, G.; Phelps, M.; Pichot, M.; Pickenpack, M.; Piergiovanni, F.; Pierro, V.; Pihlaja, M.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Plissi, M. V.; Poggiani, R.; Pöld, J.; Postiglione, F.; Poux, C.; Prato, M.; Predoi, V.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prix, R.; Prodi, G. A.; Prokhorov, L. G.; Puncken, O.; Punturo, M.; Puppo, P.; Quetschke, V.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Rácz, I.; Radkins, H.; Raffai, P.; Rakhmanov, M.; Ramet, C.; Rankins, B.; Rapagnani, P.; Raymond, V.; Re, V.; Reed, C. M.; Reed, T.; Regimbau, T.; Reid, S.; Reitze, D. H.; Ricci, F.; Riesen, R.; Riles, K.; Roberts, M.; Robertson, N. A.; Robinet, F.; Robinson, C.; Robinson, E. L.; Rocchi, A.; Roddy, S.; Rodriguez, C.; Rodruck, M.; Rolland, L.; Rollins, J. G.; Romano, J. D.; Romano, R.; Romie, J. H.; Rosińska, D.; Röver, C.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Salemi, F.; Sammut, L.; Sandberg, V.; Sankar, S.; Sannibale, V.; Santamaría, L.; Santiago-Prieto, I.; Santostasi, G.; Saracco, E.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Savage, R. L.; Schilling, R.; Schnabel, R.; Schofield, R. M. S.; Schulz, B.; Schutz, B. F.; Schwinberg, P.; Scott, J.; Scott, S. M.; Seifert, F.; Sellers, D.; Sentenac, D.; Sergeev, A.; Shaddock, D. A.; Shaltev, M.; Shapiro, B.; Shawhan, P.; Shoemaker, D. H.; Sidery, T. L.; Siemens, X.; Sigg, D.; Simakov, D.; Singer, A.; Singer, L.; Sintes, A. M.; Skelton, G. R.; Slagmolen, B. J. J.; Slutsky, J.; Smith, J. R.; Smith, M. R.; Smith, R. J. E.; Smith-Lefebvre, N. D.; Somiya, K.; Sorazu, B.; Speirits, F. C.; Sperandio, L.; Stefszky, M.; Steinert, E.; Steinlechner, J.; Steinlechner, S.; Steplewski, S.; Stochino, A.; Stone, R.; Strain, K. A.; Strigin, S. E.; Stroeer, A. S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sung, M.; Susmithan, S.; Sutton, P. J.; Swinkels, B.; Szeifert, G.; Tacca, M.; Taffarello, L.; Talukder, D.; Tanner, D. B.; Tarabrin, S. P.; Taylor, R.; ter Braack, A. P. M.; Thomas, P.; Thorne, K. A.; Thorne, K. S.; Thrane, E.; Thüring, A.; Titsler, C.; Tokmakov, K. V.; Tomlinson, C.; Toncelli, A.; Tonelli, M.; Torre, O.; Torres, C. V.; Torrie, C. I.; Tournefier, E.; Travasso, F.; Traylor, G.; Tse, M.; Ugolini, D.; Vahlbruch, H.; Vajente, G.; van den Brand, J. F. J.; Van Den Broeck, C.; van der Putten, S.; van Veggel, A. A.; Vass, S.; Vasuth, M.; Vaulin, R.; Vavoulidis, M.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Verkindt, D.; Vetrano, F.; Viceré, A.; Villar, A. E.; Vinet, J.-Y.; Vitale, S.; Vocca, H.; Vorvick, C.; Vyatchanin, S. P.; Wade, A.; Wade, L.; Wade, M.; Waldman, S. J.; Wallace, L.; Wan, Y.; Wang, M.; Wang, X.; Wanner, A.; Ward, R. L.; Was, M.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Welborn, T.; Wen, L.; Wessels, P.; West, M.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; White, D. J.; Whiting, B. F.; Wiesner, K.; Wilkinson, C.; Willems, P. A.; Williams, L.; Williams, R.; Willke, B.; Wimmer, M.; Winkelmann, L.; Winkler, W.; Wipf, C. C.; Wiseman, A. G.; Wittel, H.; Woan, G.; Wooley, R.; Worden, J.; Yablon, J.; Yakushin, I.; Yamamoto, H.; Yamamoto, K.; Yancey, C. C.; Yang, H.; Yeaton-Massey, D.; Yoshida, S.; Yvert, M.; Zadrożny, A.; Zanolin, M.; Zendri, J.-P.; Zhang, F.; Zhang, L.; Zhao, C.; Zotov, N.; Zucker, M. E.; Zweizig, J.

    2012-12-01

    We present the first multi-wavelength follow-up observations of two candidate gravitational-wave (GW) transient events recorded by LIGO and Virgo in their 2009-2010 science run. The events were selected with low latency by the network of GW detectors (within less than 10 minutes) and their candidate sky locations were observed by the Swift observatory (within 12 hr). Image transient detection was used to analyze the collected electromagnetic data, which were found to be consistent with background. Off-line analysis of the GW data alone has also established that the selected GW events show no evidence of an astrophysical origin; one of them is consistent with background and the other one was a test, part of a "blind injection challenge." With this work we demonstrate the feasibility of rapid follow-ups of GW transients and establish the sensitivity improvement joint electromagnetic and GW observations could bring. This is a first step toward an electromagnetic follow-up program in the regime of routine detections with the advanced GW instruments expected within this decade. In that regime, multi-wavelength observations will play a significant role in completing the astrophysical identification of GW sources. We present the methods and results from this first combined analysis and discuss its implications in terms of sensitivity for the present and future instruments.

  3. A TRANSITION REGION EXPLOSIVE EVENT OBSERVED IN He II WITH THE MOSES SOUNDING ROCKET

    SciTech Connect

    Fox, J. Lewis; Kankelborg, Charles C.; Thomas, Roger J. E-mail: kankel@solar.physics.montana.ed

    2010-08-20

    Transition region explosive events (EEs) have been observed with slit spectrographs since at least 1975, most commonly in lines of C IV (1548 A, 1550 A) and Si IV (1393 A, 1402 A). We report what we believe to be the first observation of a transition region EE in He II 304 A. With the Multi-Order Solar EUV Spectrograph (MOSES) sounding rocket, a novel slitless imaging spectrograph, we are able to see the spatial structure of the event. We observe a bright core expelling two jets that are distinctly non-collinear, in directions that are not anti-parallel. The jets have sky-plane velocities of order 75 km s{sup -1} and line-of-sight velocities of +75 km s{sup -1} (blue) and -30 km s{sup -1} (red). The core is a region of high non-thermal Doppler broadening, characteristic of EEs, with maximal broadening 380 km s{sup -1} FWHM. It is possible to resolve the core broadening into red and blue line-of-sight components of maximum Doppler velocities +160 km s{sup -1} and -220 km s{sup -1}. The event lasts more than 150 s. Its properties correspond to the larger, long-lived, and more energetic EEs observed in other wavelengths.

  4. Swift Follow-Up Observations of Candidate Gravitational-Wave Transient Events

    NASA Technical Reports Server (NTRS)

    Evans, P. A.; Fridriksson, J. K.; Gehrels, N.; Homan, J.; Osborne, J. P.; Siegel, M.; Beardmore, A.; Handbauer, P.; Gelbord, J.; Kennea, J. A.; Smith, M.; Zhu, Q.; Aasi, J.; Abadie, J.; Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M.; Accadia, T.; Acernese, F.; Adams, C.; Adams, T.; Blackburn, J. K.; Camp, J. B.; Kanner, J. B.

    2012-01-01

    We present the first multi-wavelength follow-up observations of two candidate gravitational-wave (GW) transient events recorded by LIGO and Virgo in their 2009-2010 science run. The events were selected with low latency by the network of GW detectors (within less than 10 minutes) and their candidate sky locations were observed by the Swift observatory (within 12 hr). Image transient detection was used to analyze the collected electromagnetic data, which were found to be consistent with background. Off-line analysis of the GW data alone has also established that the selected GW events show no evidence of an astrophysical origin; one of them is consistent with background and the other one was a test, part of a "blind injection challenge." With this work we demonstrate the feasibility of rapid follow-ups of GW transients and establish the sensitivity improvement joint electromagnetic and GW observations could bring. This is a first step toward an electromagnetic follow-up program in the regime of routine detections with the advanced GW instruments expected within this decade. In that regime, multi-wavelength observations will play a significant role in completing the astrophysical identification of GW sources. We present the methods and results from this first combined analysis and discuss its implications in terms of sensitivity for the present and future instruments.

  5. Prospects for observations of transient UV Events with the TAUVEX UV observatory

    NASA Astrophysics Data System (ADS)

    Safonova, Margarita; Sivaram, C.; Murthy, Jayant

    2008-11-01

    Transient events have posed special problems in astronomy because of the intrinsic difficulty of their detection, and a new class of observatories such as the Pan-STARRS and LSST are coming up specifically to observe these energetic events. In this paper we discuss the UV transient events from two specific sources, such as possible collisions in extrasolar planetary systems and M dwarf flares, to find the probability of their detection by space UV observatories, in particular, by the Tel Aviv University Explorer (TAUVEX). TAUVEX is an UV imaging experiment that will image large parts of the sky in the wavelength region between 1200 and 3500 Å. TAUVEX is a collaborative effort between the Indian Institute of Astrophysics (IIA) and Tel Aviv University, and is scheduled for an early-2009 launch with at least three years of operations. The scientific instrument has been fabricated at El-Op in Israel, with the satellite interfaces, launch and flight operations provided by the Indian Space Research Organization (ISRO). The ground-based software development is the responsibility of the IIA while other aspects of the mission are the joint responsibility of IIA and Tel Aviv University. TAUVEX Science Team (TST) have created a coherent observing program to address several key science objectives, one of them is a program to study short-scale UV transient events. We have estimated that in one year of TAUVEX observations we can expect about 90 350 short-scale transient events. Because we obtain real-time telemetry with TAUVEX, we will be able to catch transients early in their evolution and to alert other observatories. We also present a description of TAUVEX mission, including instrument design and its estimated performance.

  6. Long-period events, the most characteristic seismicity accompanying the emplacement and extrusion of a lava dome in Galeras Volcano, Colombia, in 1991

    USGS Publications Warehouse

    Gil, Cruz F.; Chouet, B.A.

    1997-01-01

    Since its reactivation in 1988 the principal eruptions of Galeras Volcano occurred on May 4-9, 1989, July 16, 1992, and January 14, March 23, April 3, April 14 and June 7, 1993. The initial eruption was a phreatic event which clearly marked a new period of activity. A lava dome was extruded within the main crater in October 1991 and subsequently destroyed in an explosive eruption on July 16, 1992. The eruptions that followed were all vulcanian-type explosions. The seismicity accompanying the emplacement, extrusion, and destruction of the lava dome was dominated by a mix of long-period (LP) events and tremor displaying a variety of waveforms. Repetitive LP events with dominant periods in the range 0.2-1 s were observed in October and November 1991 and visually correlated with short energetic pulses of gas venting through a crack bisecting the dome surface. Each LP event was characterized by a weak precursory signal with dominant periods in the range 0.05-0.1 s lasting roughly 7 s. Using the fluid-driven crack model of Chouet (1988, 1992), we infer that two distinct cracks may have acted as sources for the LP and precursor signals. Spectral analyses of the data yield the following parameters for the LP source: crack length, 240-360 m; crack width, 130-150 m; crack aperture, 0.5-3.4 mm; crack stiffness, 100-500; sound speed of fluid, 880 m/s; and excess pressure, 0.01-0.19 MPa. Similar analyses yield the parameters of the precursor source: crack length, 20-30 m; crack width, 15-25 m; crack aperture, 2.3-8.7 mm; crack stiffness, 5-15; sound speed of fluid, 140 m/s; and excess pressure, 0.06-0.15 MPa. Combined with geologic and thermodynamic constraints obtained from field observations, these seismic parameters suggest a gas-release mechanism in which the episodic collapse of a foam layer trapped at the top of the magma column subjacent to the dome releases a slug of pressurized gas which escapes to the surface while dilating a preexisting system of cracks in the dome

  7. First observations of W Virginis stars with K2: detection of period doubling

    NASA Astrophysics Data System (ADS)

    Plachy, E.; Molnár, L.; Jurkovic, M. I.; Smolec, R.; Moskalik, P. A.; Pál, A.; Szabados, L.; Szabó, R.

    2017-02-01

    We present the first analysis of W Vir stars observed by the Kepler space telescope in the K2 mission. Clear cycle-to-cycle variations were detected in the light curves of KT Sco and the globular cluster member M80-V1. While the variations in the former star seem to be irregular on the short time-scale of the K2 data, the latter appears to experience period doubling in its pulsation. Ground-based colour data confirmed that both stars are W Vir-type pulsators, while a comparison with historical photometric time series data revealed drastic period changes in both stars. For comparison we reexamine ground-based observations of W Vir, the prototype of the class, and conclude that it shows period doubling instead of mode beating. These results support the notion that non-linear dynamics plays an important role in the pulsation of W Virginis-type stars.

  8. LOW-FREQUENCY OBSERVATIONS OF TRANSIENT QUASI-PERIODIC RADIO EMISSION FROM THE SOLAR ATMOSPHERE

    SciTech Connect

    Sasikumar Raja, K.; Ramesh, R.

    2013-09-20

    We report low-frequency observations of quasi-periodic, circularly polarized, harmonic type III radio bursts whose associated sunspot active regions were located close to the solar limb. The measured periodicity of the bursts at 80 MHz was ≈5.2 s, and their average degree of circular polarization (dcp) was ≈0.12. We calculated the associated magnetic field B (1) using the empirical relationship between the dcp and B for the harmonic type III emission, and (2) from the observed quasi-periodicity of the bursts. Both the methods result in B ≈ 4.2 G at the location of the 80 MHz plasma level (radial distance r ≈ 1.3 R{sub ☉}) in the active region corona.

  9. OBSERVATIONS OF A TWO-STAGE SOLAR ERUPTIVE EVENT (SEE): EVIDENCE FOR SECONDARY HEATING

    SciTech Connect

    Su Yang; Dennis, Brian R.; Holman, Gordon D.; Wang, Tongjiang; Chamberlin, Phillip C.; Savage, Sabrina; Veronig, Astrid

    2012-02-10

    We present RHESSI, SDO/AIA, SOHO/LASCO, STEREO, and GOES observations of a partially occulted solar eruptive event that occurred at the southwest limb on 2011 March 8. The GOES X-ray light curve shows two peaks separated by almost 2 hr that we interpret as two stages of a single event associated with the delayed eruption of a coronal mass ejection (CME). A hot flux rope formed during the first stage and continued expanding and rising throughout the event. The speed of the flux rope decreased from {approx}120 to 14 km s{sup -1} during the decay phase of the first stage and increased again during the second stage to become the CME with a speed of {approx}516 km s{sup -1}. RHESSI and GOES data analyses show that the plasma temperature reached over 20 MK in the first stage, then decreased to {approx}10 MK and increased to 15 MK in the second stage. This event provides clear evidence for a secondary heating phase. The enhanced EUV and X-ray emission came from the high corona ({approx}60 arcsec above the limb) in the second stage, {approx}40 arcsec higher than the site of the initial flare emission. STEREO-A on-disk observations indicate that the post-flare loops during this stage were of larger scale sizes and spatially distinct from those in the first stage.

  10. Observations of a Two-Stage Solar Eruptive Event (SEE): Evidence for Secondary Heating

    NASA Technical Reports Server (NTRS)

    Su, Yang; Dennis, Brian R.; Holman, Gordon D.; Wang, Tongjiang; Chamberlin, Phillip C.; Savage, Sabrina; Veronig, Astrid

    2012-01-01

    We present RHESSI, SDO/AIA, SOHO/LASCO, STEREO, and GOES observations of a partially occulted solar eruptive event (SEE) that occurred at the South-West limb on 8 March, 2011. The GOES X-ray light curve shows two peaks separated by almost two hours that we interpret as two stages of a single event associated with the delayed eruption of a CME. A hot flux rope formed during the first stage and continued expanding and rising throughout the event. The speed of the flux rope decreased from approx.120 to 14 km/s during the decay phase of the first stage and increased again during the second stage to become the CME with a speed of approx.516 km/s. RHESSI and GOES data analyses show that the plasma temperature reached over 20 MK in the first stage, then decreased to approx.10 MK and increased to 15 MK in the second stage. This event provides clear evidence for a secondary heating phase. The enhanced EUV and X-ray emission came from the high corona ( approx.60 arcsec above the limb) in the second stage, approx.40 arcsec higher than the site of the initial flare emission. STEREO-A on-disk observations indicate that the post-flare loops during this stage were of larger scale sizes and spatially distinct from those in the first stage.

  11. Spurious One-Month and One-Year Periods in Visual Observations of Variable Stars

    NASA Astrophysics Data System (ADS)

    Percy, J. R.

    2015-12-01

    Visual observations of variable stars, when time-series analyzed with some algorithms such as DC-DFT in vstar, show spurious periods at or close to one synodic month (29.5306 days), and also at about a year, with an amplitude of typically a few hundredths of a magnitude. The one-year periods have been attributed to the Ceraski effect, which was believed to be a physiological effect of the visual observing process. This paper reports on time-series analysis, using DC-DFT in vstar, of visual observations (and in some cases, V observations) of a large number of stars in the AAVSO International Database, initially to investigate the one-month periods. The results suggest that both the one-month and one-year periods are actually due to aliasing of the stars' very low-frequency variations, though they do not rule out very low-amplitude signals (typically 0.01 to 0.02 magnitude) which may be due to a different process, such as a physiological one. Most or all of these aliasing effects may be avoided by using a different algorithm, which takes explicit account of the window function of the data, and/or by being fully aware of the possible presence of and aliasing by very low-frequency variations.

  12. Observation of New Particle Formation and Growth Events in Asian Continental Outflow

    NASA Astrophysics Data System (ADS)

    Kim, S.; Kim, Y.; Yoon, S.; Kim, K.; Choi, W.; Lim, H.; Hong, C.

    2012-12-01

    This study is based on 3-year continuous measurements (January 2008-December 2010) of aerosol number size distributions recorded with a Scanning Mobility Particle Sizer (SMPS) at two regional background stations, Gosan Climate Observatory (GCO) and Korea Global Atmosphere Watch Center (KGAWC), in Korea. We identified new particle formation and growth (NPF) events by applying the Cyclostationary Empirical Orthogonal Function (CSEOF) technique to aerosol number size distributions. Based on the first mode loading vectors and the corresponding principle components in the CSEOF analysis, we classified strong, weak, and non NPF days. A strong NPF event was observed on 7.5% of days (60 days out of a total 800 days) at GCO and on 14.6% of days (140 days out of a total 958 days) at KGAWC. The maximum occurrence of strong NPF events was reported in spring at GCO, but in winter at KGAWC. Only 16 of these days were considered as simultaneous NPF events, and 7 days were identical NPF events. The airmass history analysis on simultaneous NPF days indicated the NPF events to be associated with a fast-moving cold and dry airmass from the Asian continent after the passage of a frontal system. The particle formation rate (FR) and growth rate (GR) were estimated to be 1.44 (1.20) cm-3 s-1 and 4.4 (4.7) nm h-1, respectively, at GCO and KGAWC (in parentheses). Almost identical values for the condensation sink were estimated in strong NPF (8.3 ~ 10-3 s-1) and non NPF (8.2 ~ 10-3 s-1) events at GCO, whereas the condensation sink for strong NPF days (8.5 ~ 10-5 s-1) was lower than that of non NPF days (1.1 ~ 10-2 s-1) at KGAWC. The FR, GR, condensation sink, and vapor source rate at both GCO and KGAWC were lower than those reported in polluted urban areas, but higher than those at clean sites. In this study, we also present direct observational evidence that freshly nucleated particles are capable of growing to sufficiently large sizes and act as cloud condensation nuclei (CCN). The

  13. Water quantity and quality response of a green roof to storm events: Experimental and monitoring observations.

    PubMed

    Carpenter, Corey M G; Todorov, Dimitar; Driscoll, Charles T; Montesdeoca, Mario

    2016-11-01

    Syracuse, New York is working under a court-ordered agreement to limit combined sewer overflows (CSO) to local surface waters. Green infrastructure technologies, including green roofs, are being implemented as part of a CSO abatement strategy and to develop co-benefits of diminished stormwater runoff, including decreased loading of contaminants to the wastewater system and surface waters. The objective of this study was to examine the quantity and quality of discharge associated with precipitation events over an annual cycle from a green roof in Syracuse, NY and to compare measurements from this monitoring program with results from a roof irrigation experiment. Wet deposition, roof drainage, and water quality were measured for 87 storm events during an approximately 12 month period over 2011-2012. Water and nutrient (total phosphorus, total nitrogen, and dissolved organic carbon) mass balances were conducted on an event basis to evaluate retention annually and during the growing and non-growing seasons. These results are compared with a hydrological manipulation experiment, which comprised of artificially watering of the roof. Loadings of nutrients were calculated for experimental and actual storms using the concentration of nutrients and the flow data of water discharging the roof. The green roof was effective in retaining precipitation quantity from storm events (mean percent retention 96.8%, SD = 2.7%, n = 87), although the relative fraction of water retained decreased with increases in the size of the event. There was no difference in water retention of the green roof for the growing and non-growing seasons. Drainage waters exhibited high concentration of nutrients during the warm temperature growing season, particularly total nitrogen and dissolved organic carbon. Overall, nutrient losses were low because of the strong retention of water. However, there was marked variation in the retention of nutrients by season due to variations in concentrations in roof

  14. Observations of narrow bipolar events reveal how lightning is initiated in thunderstorms.

    PubMed

    Rison, William; Krehbiel, Paul R; Stock, Michael G; Edens, Harald E; Shao, Xuan-Min; Thomas, Ronald J; Stanley, Mark A; Zhang, Yang

    2016-02-15

    A long-standing but fundamental question in lightning studies concerns how lightning is initiated inside storms, given the absence of physical conductors. The issue has revolved around the question of whether the discharges are initiated solely by conventional dielectric breakdown or involve relativistic runaway electron processes. Here we report observations of a relatively unknown type of discharge, called fast positive breakdown, that is the cause of high-power discharges known as narrow bipolar events. The breakdown is found to have a wide range of strengths and is the initiating event of numerous lightning discharges. It appears to be purely dielectric in nature and to consist of a system of positive streamers in a locally intense electric field region. It initiates negative breakdown at the starting location of the streamers, which leads to the ensuing flash. The observations show that many or possibly all lightning flashes are initiated by fast positive breakdown.

  15. Observations of narrow bipolar events reveal how lightning is initiated in thunderstorms

    SciTech Connect

    Rison, William; Krehbiel, Paul R.; Stock, Michael G.; Edens, Harald E.; Shao, Xuan-Min; Thomas, Ronald J.; Stanley, Mark A.; Zhang, Yang

    2016-02-15

    A long-standing but fundamental question in lightning studies concerns how lightning is initiated inside storms, given the absence of physical conductors. The issue has revolved around the question of whether the discharges are initiated solely by conventional dielectric breakdown or involve relativistic runaway electron processes. Here we report observations of a relatively unknown type of discharge, called fast positive breakdown, that is the cause of high-power discharges known as narrow bipolar events. We find that the breakdown has a wide range of strengths and is the initiating event of numerous lightning discharges. It appears to be purely dielectric in nature and to consist of a system of positive streamers in a locally intense electric field region. It initiates negative breakdown at the starting location of the streamers, which leads to the ensuing flash. The observations show that many or possibly all lightning flashes are initiated by fast positive breakdown.

  16. Observations of narrow bipolar events reveal how lightning is initiated in thunderstorms

    PubMed Central

    Rison, William; Krehbiel, Paul R.; Stock, Michael G.; Edens, Harald E.; Shao, Xuan-Min; Thomas, Ronald J.; Stanley, Mark A.; Zhang, Yang

    2016-01-01

    A long-standing but fundamental question in lightning studies concerns how lightning is initiated inside storms, given the absence of physical conductors. The issue has revolved around the question of whether the discharges are initiated solely by conventional dielectric breakdown or involve relativistic runaway electron processes. Here we report observations of a relatively unknown type of discharge, called fast positive breakdown, that is the cause of high-power discharges known as narrow bipolar events. The breakdown is found to have a wide range of strengths and is the initiating event of numerous lightning discharges. It appears to be purely dielectric in nature and to consist of a system of positive streamers in a locally intense electric field region. It initiates negative breakdown at the starting location of the streamers, which leads to the ensuing flash. The observations show that many or possibly all lightning flashes are initiated by fast positive breakdown. PMID:26876654

  17. Observations of narrow bipolar events reveal how lightning is initiated in thunderstorms

    DOE PAGES

    Rison, William; Krehbiel, Paul R.; Stock, Michael G.; ...

    2016-02-15

    A long-standing but fundamental question in lightning studies concerns how lightning is initiated inside storms, given the absence of physical conductors. The issue has revolved around the question of whether the discharges are initiated solely by conventional dielectric breakdown or involve relativistic runaway electron processes. Here we report observations of a relatively unknown type of discharge, called fast positive breakdown, that is the cause of high-power discharges known as narrow bipolar events. We find that the breakdown has a wide range of strengths and is the initiating event of numerous lightning discharges. It appears to be purely dielectric in naturemore » and to consist of a system of positive streamers in a locally intense electric field region. It initiates negative breakdown at the starting location of the streamers, which leads to the ensuing flash. The observations show that many or possibly all lightning flashes are initiated by fast positive breakdown.« less

  18. Catalogue of electron precipitation events as observed in the long-duration cosmic ray balloon experiment

    NASA Astrophysics Data System (ADS)

    Makhmutov, V. S.; Bazilevskaya, G. A.; Stozhkov, Yu. I.; Svirzhevskaya, A. K.; Svirzhevsky, N. S.

    2016-11-01

    Since the International Geophysical Year (1957), the Lebedev Physical Institute performs the regular measurements of charged particle fluxes in the Earth's atmosphere (from the ground level up to 30-35 km) at several latitudes. The unique experimental data base obtained during 58 years of cosmic rays observations in the atmosphere allows to investigate temporal, spatial and energetic characteristics of galactic and solar cosmic rays as well as the role of charged particles in the atmospheric processes. Analysis of this data base also revealed a special class of numerous events caused by energetic electron precipitation recorded in the atmosphere at polar latitudes. In this paper we present Catalogue of electron precipitation events observed in the polar atmosphere during 1961-2014 and briefly outline the previous results of this data set analysis.

  19. Observing a Severe Dust Storm Event over China using Multiple Satellite Data

    NASA Astrophysics Data System (ADS)

    Xu, Hui; Xue, Yong; Guang, Jie; Mei, Linlu

    2013-04-01

    A severe dust storm (SDS) event occurred from 19 to 21 March 2010 in China, originated in western China and Mongolia and propagated into eastern/southern China, affecting human's life in a large area. As reported by National Meteorological Center of CMA (China Meteorological Administration), 16 provinces (cities) of China were hit by the dust storm (Han et al., 2012). Satellites can provide global measurements of desert dust and have particular importance in remote areas where there is a lack of in situ measurements (Carboni et al., 2012). To observe a dust, it is necessary to estimate the spatial and temporal distributions of dust aerosols. An important metric in the characterisation of aerosol distribution is the aerosol optical depth (AOD) (Adhikary et al., 2008). Satellite aerosol retrievals have improved considerably in the last decade, and numerous satellite sensors and algorithms have been generated. Reliable retrievals of dust aerosol over land were made using POLarization and Directionality of the Earth's Reflectance instrument-POLDER (Deuze et al., 2001), Moderate Resolution Imaging Spectroradiometer-MODIS (Kaufman et al., 1997; Hsu et al., 2004), Multiangle Imaging Spectroradiometer-MISR (Martonchik et al., 1998), and Cloud-aerosol Lidar and infrared pathfinder satellite observations (CALIPSO). However, intercomparison exercises (Myhre et al., 2005) have revealed that discrepancies between satellite measurements are particularly large during events of heavy aerosol loading. The reason is that different AOD retrieval algorithms make use of different instrument characteristics to obtain retrievals over bright surfaces. For MISR, POLDER and MODIS instrument, the multi-angle approaches, the polarization measurements and single-view approaches were used to retrieval AOD respectively. Combining of multi-sensor AOD data can potentially create a more consistent, reliable and complete picture of the space-time evolution of dust storms (Ehlers, 1991). In order to

  20. IRIS observations and MHD simulations of explosive events in the transition region of the Sun

    NASA Astrophysics Data System (ADS)

    Guo, Lijia; Innes, Davina; Huang, Yi-Min; Bhattacharjee, Amitava

    2016-05-01

    Small-scale explosive events on the Sun are thought to be related to magnetic reconnection. While Petschek reconnection has been considered as a reconnection mechanism for explosive events on the Sun for quite a long time, the fragmentation of a current sheet in the high-Lundquist-number regime caused by the plasmoid instability has recently been proposed as a possible mechanism for fast reconnection. The actual reconnection sites are too small to be resolved with images but these reconnection mechanisms, Petschek and the plasmoid instability, have very different density and velocity structures and so can be distinguished by high-resolution line profiles observations. We use high-resolution sit-and-stare spectral observations of the Si IV line, obtained by the IRIS spectrometer, to identify sites of reconnection, and follow the development of line profiles. The aim is to obtain a survey of typical line profiles produced by small-scale reconnection events in the transition region and compare them with synthetic line profiles from numerical simulations of a reconnecting current sheet to determine whether reconnection occurs via the plasmoid instabilty or the Petschek mechanism. Direct comparison between IRIS observations and numerical results suggests that the observed Si IV profiles can be reproduced with a fragmented current layer subject to plasmoid instability but not by bi-directional jets that characterise the Petschek mechanism. This result suggests that if these small-scale events are reconnection sites, then fast reconnection proceeds via the plasmoid instability, rather than the Petschek mechanism during small-scale reconnection on the Sun.

  1. Total gaseous mercury depletion events observed at Cape Point during 2007-2008

    NASA Astrophysics Data System (ADS)

    Brunke, E.-G.; Labuschagne, C.; Ebinghaus, R.; Kock, H. H.; Slemr, F.

    2009-10-01

    Gaseous mercury in the marine boundary layer has been measured with a 15 min temporal resolution at the Global Atmosphere Watch station Cape Point since March 2007. The most prominent features of the data until July 2008 are the frequent occurrences of pollution (PEs) and depletion events (DEs). Both types of events originate mostly within a short transport distance (up to about 100 km), which are embedded in air masses ranging from marine background to continental. The Hg/CO emission ratios observed during the PEs are within the range reported for biomass burning and industrial/urban emissions. The depletion of gaseous mercury during the DEs is almost quantitative in many cases and suggests a lifetime of elemental mercury as short as a few dozens of hours, which is in contrast to the commonly used estimate of approximately 1 year. The characteristics of the DE occurrence at Cape Point is neither similar to the halogen driven atmospheric mercury depletion events (AMDEs) observed in Polar Regions nor to the DEs reported for plumes of urban air. Additional measurements are necessary to reveal the chemical mechanism of the observed DEs and to assess its importance on larger scales.

  2. Statistical properties of quasi-periodic pulsations in white-light flares observed with Kepler

    NASA Astrophysics Data System (ADS)

    Pugh, C. E.; Armstrong, D. J.; Nakariakov, V. M.; Broomhall, A.-M.

    2016-07-01

    We embark on a study of quasi-periodic pulsations (QPPs) in the decay phase of white-light stellar flares observed by Kepler. Out of the 1439 flares on 216 different stars detected in the short-cadence data using an automated search, 56 flares are found to have pronounced QPP-like signatures in the light curve, of which 11 have stable decaying oscillations. No correlation is found between the QPP period and the stellar temperature, radius, rotation period and surface gravity, suggesting that the QPPs are independent of global stellar parameters. Hence they are likely to be the result of processes occurring in the local environment. There is also no significant correlation between the QPP period and flare energy, however there is evidence that the period scales with the QPP decay time for the Gaussian damping scenario, but not to a significant degree for the exponentially damped case. This same scaling has been observed for MHD oscillations on the Sun, suggesting that they could be the cause of the QPPs in those flares. Scaling laws of the flare energy are also investigated, supporting previous reports of a strong correlation between the flare energy and stellar temperature/radius. A negative correlation between the flare energy and stellar surface gravity is also found.

  3. Ten-year transient luminous events and Earth observations of FORMOSAT-2

    NASA Astrophysics Data System (ADS)

    Chern, Rock Jeng-Shing; Lin, Shin-Fa; Wu, An-Ming

    2015-07-01

    The purpose of this paper is to summarize the enormous contributions of FS2 (FORMOSAT-2 or Formosa satellite #2) in both Earth and transient luminous events (TLEs) observations in 10 years. As a small satellite operated for 10 years (20 May 2004 to 20 May 2014) in orbit, FS2 keeps its two unique characteristics: (1) to orbit 14 revolutions around the Earth per day with daily revisit capability, and (2) to provide the capabilities of Earth observation in sunlight time and TLEs observation in eclipsed time every day. It carries two payloads: the remote sensing instrument (RSI) for Earth imaging in satellite's day time and the imager of sprites and upper atmospheric lightning instrument (ISUAL) for scientific observations in satellite's night time, respectively. Daily revisit capability provides changes of events on Earth in either short time (several days) or long term (several years). Examples include: Indian Ocean earthquake and tsunami (December 2004), disintegration of Wilkins Ice Shelf in Antarctica region (2006-2014, long term), Sichuan earthquake (May 2008), Tohoku earthquake and tsunami (March 2011), polar regions (2006-2014, long term), etc. In the TLEs observation, ISUAL had recorded more than 35,000 events in 10 years with 73.93% elves, 6.54% red sprites, 5.81% halos, 13.42% blue jets and 0.30% gigantic jets. Major contributions of FS2 in this specific scientific area are presented. In particular, current and future research topics on TLEs are discussed. Also, major contributions of FS2's RSI to the United Nations Institute for Training and Research (UNITAR) Operational Satellite Applications Programme (UNOSAT) and Group of Earth Observation System of Systems (GEOSS) are summarized. This paper also addresses briefly the health status of FS2 after working 10 years in orbit.

  4. Multi-wavelength Observations of a Subarcsecond Penumbral Transient Brightening Event

    NASA Astrophysics Data System (ADS)

    Bai, X. Y.; Su, J. T.; Cao, W. D.; Liu, S. Q.; Deng, Y. Y.; Priya, T. G.

    2016-05-01

    We report a subarcsecond penumbral transient brightening event with the high-spatial resolution observations from the 1.6 m New Solar Telescope (NST), Interface Region Imaging Spectrograph (IRIS), and the Solar Dynamics Observatory. The transient brightening, whose thermal energy is in the range of nanoflares, has signatures in the chromosphere, the transient region, and the corona. NST's Hα channel reveals the fine structure of the event with a width as narrow as 101 km (0.″14), which is much smaller than the width from the previous observation. The transient brightening lasts for about 3 minutes. It is associated with a redshift of about 17 km s-1, found in the Si iv 1402.77 Å line and exhibits an inward motion to the umbra with a speed of 87 km s-1. The small-scale energy released from the event has a multi-temperature component. Spectral analysis of the brightening region from IRIS shows that not only the transition region lines such as Si iv 1402.77 Å and C ii 1334.53 Å, but also the chromospheric Mg ii k 2796.35 Å line are significantly enhanced and broadened. In addition, the event can be found in all the extreme-ultraviolet passbands of the Atmospheric Imaging Assembly and the derived differential emission measure profile increases between 4 and 15 MK (or 6.6 ≤ log T ≤ 7.2) in the transient brightening phase. It is possible that the penumbral transient brightening event is caused by magnetic reconnection.

  5. Steady state and a singular event observed at the TAG hydrothermal mound by a long-term monitoring system

    NASA Astrophysics Data System (ADS)

    Fujioka, K.; Aoki, M.; Mitsuzawa, K.; Kato, K.; Kinoshita, M.; Nishizawa, A.

    2005-12-01

    The steady state variability and occasional O`randomO_L event of hydrothermal activity were observed by several long-term monitoring systems deployed on the TAG hydrothermal mound and observed by submersible video and still cameras in the Mid Atlantic Ridge 26 N. We measured current direction and velocity, visibility, temperature, and salinity of sea water as well as observed newly formed black smokers by video and still camera system. Heat flow measurement system and an OBSH were also deployed around the central black smoker and newly formed black smokers for more than two weeks. Steady state change of the temperature, current direction and velocity, visibility and pressure change by hydrophone show a regular semidiurnal periodic variation, which may be caused by ocean, and earth tides. A singular event occurred during our research at the TAG hydrothermal mound. Small earthquakes beneath the TAG mound were followed by a huge slope failure, which apparently caused by a debris flow, killing swimming eel-like fish. A thin bed of the dead shrimps may be related to a nearly simultaneous increase of hot water flux from vent.

  6. Air Twitter: Mashing Crowdsourced Air Quality Event Identification with Scientific Earth Observations (Invited)

    NASA Astrophysics Data System (ADS)

    Robinson, E. M.

    2010-12-01

    , which allows time series of the number of tweets hourly and daily. Monitoring the time series AQ events are identified from the background chatter about air quality. As the events are identified, collaborative, EventSpaces (Robinson, 2008) are created using the ESIP wiki to collect and merge social and scientific information about the event. The EventSpaces are monitored using Google Analytics. During the August California Fires the traffic increased five-fold to the ESIP wiki. Furthermore, the increase in traffic was entirely due to views of the SoCal FireEventSpace. A top driver to the site was through tweeting the link to the EventSpace and having that link re-tweeted by others like the LA Times. An interesting an unexpected observation, was that most of the increased traffic was coming from Southern California. So the right people were finding the right information at the right time. The overall benefit of using the online community as an AQ event indicator, allows specific effort to be made for initial documentation of air quality events and the result is a catalog of events with some sparse analysis that can be followed-up.

  7. Reconstructing Methane Emission Events in the Arctic Ocean: Observations from the Past to Present

    NASA Astrophysics Data System (ADS)

    Panieri, G.; Mienert, J.; Fornari, D. J.; Torres, M. E.; Lepland, A.

    2015-12-01

    Methane hydrates are ice-like crystals that are present along continental margins, occurring in the pore space of deep sediments or as massive blocks near the seafloor. They form in high pressure and low temperature environments constrained by thermodynamic stability, and supply of methane. In the Arctic, gas hydrates are abundant, and the methane released by their destabilization can affect local to global carbon budgets and cycles, ocean acidification, and benthic community survival. With the aim to locate in space and time the periodicity of methane venting, CAGE is engaged in a vast research program in the Arctic, a component of which comprises the analyses of numerous sediment cores and correlative geophysical and geochemical data from different areas. Here we present results from combined analyses of biogenic carbonate archives along the western Svalbard Margin, which reveal past methane venting events in this region. The reconstruction of paleo-methane discharge is complicated by precipitation of secondary carbonate on foraminifera shells, driven by an increase in alkalinity during anaerobic oxidation of methane (AOM). The biogeochemical processes involved in methane cycling and processes that drive methane migration affect the depth where AOM occurs, with relevance to secondary carbonate formation. Our results show the value and complexity of separating primary vs. secondary signals in bioarchives with relevance to understanding fluid-burial history in methane seep provinces. Results from our core analyses are integrated with observations made during the CAGE15-2 cruise in May 2015, when we deployed a towed vehicle equipped with camera, multicore and water sampling capabilities. The instrument design was based on the Woods Hole Oceanographic Institution (WHOI) MISO TowCam sled equipped with a deep-sea digital camera and CTD real-time system. Sediment sampling was visually-guided using this system. In one of the pockmarks along the Vestnesa Ridge where high

  8. Observation of quasi-periodic solar radio bursts associated with propagating fast-mode waves

    NASA Astrophysics Data System (ADS)

    Goddard, C. R.; Nisticò, G.; Nakariakov, V. M.; Zimovets, I. V.; White, S. M.

    2016-10-01

    Aims: Radio emission observations from the Learmonth and Bruny Island radio spectrographs are analysed to determine the nature of a train of discrete, periodic radio "sparks" (finite-bandwidth, short-duration isolated radio features) which precede a type II burst. We analyse extreme ultraviolet (EUV) imaging from SDO/AIA at multiple wavelengths and identify a series of quasi-periodic rapidly-propagating enhancements, which we interpret as a fast wave train, and link these to the detected radio features. Methods: The speeds and positions of the periodic rapidly propagating fast waves and the coronal mass ejection (CME) were recorded using running-difference images and time-distance analysis. From the frequency of the radio sparks the local electron density at the emission location was estimated for each. Using an empirical model for the scaling of density in the corona, the calculated electron density was used to obtain the height above the surface at which the emission occurs, and the propagation velocity of the emission location. Results: The period of the radio sparks, δtr = 1.78 ± 0.04 min, matches the period of the fast wave train observed at 171 Å, δtEUV = 1.7 ± 0.2 min. The inferred speed of the emission location of the radio sparks, 630 km s-1, is comparable to the measured speed of the CME leading edge, 500 km s-1, and the speeds derived from the drifting of the type II lanes. The calculated height of the radio emission (obtained from the density) matches the observed location of the CME leading edge. From the above evidence we propose that the radio sparks are caused by the quasi-periodic fast waves, and the emission is generated as they catch up and interact with the leading edge of the CME. The movie associated to Fig. 2 is available at http://www.aanda.org

  9. Observed changes of temperature extremes in Serbia over the period 1961 - 2010

    NASA Astrophysics Data System (ADS)

    Ruml, Mirjana; Gregorić, Enike; Vujadinović, Mirjam; Radovanović, Slavica; Matović, Gordana; Vuković, Ana; Počuča, Vesna; Stojičić, Djurdja

    2017-01-01

    The analysis of spatiotemporal changes of temperature extremes in Serbia, based on 18 ETCCDI indices, was performed using daily minimum and maximum temperature observations from 26 meteorological stations over the period 1961-2010. The observation period was divided into two sub-periods (1961-1980 and 1981-2010) according to the results of the sequential Mann-Kendall test. Temporal trends were evaluated by a least-squares linear regression method. The average annual minimum temperature displayed a mixed pattern of increasing, decreasing, and no trends over 1961-1980 and a significant increasing trend over 1981-2010 across the whole country, with a regionally averaged rate of 0.48 °C per decade. The average annual maximum temperature showed a decreasing trend during 1961-1980 and a significant increasing trend at all stations during 1981-2010, with a regionally averaged rate of 0.56 °C per decade. Hot indices exhibited a general cooling tendency until 1980 and a warming tendency afterwards, with the most pronounced trends in the number of summer and tropical days during the first period and in the frequency of warm days and nights in the second. Cold indices displayed a mostly warming tendency over the entire period, with the most remarkable increase in the lowest annual maximum temperature and the number of ice days during the first period and in the frequency of cool nights during the second. At most stations, the diurnal temperature range showed a decrease until 1980 and no change or a slight increase afterwards. The lengthening of the growing season was much more pronounced in the later period. The computed correlation coefficient between the annual temperature indices and large-scale circulation features revealed that the East Atlantic pattern displayed much stronger association with examined indices than the North Atlantic Oscillation and East Atlantic/West Russia pattern.

  10. IMAGING AND SPECTRAL OBSERVATIONS OF QUASI-PERIODIC PULSATIONS IN A SOLAR FLARE

    SciTech Connect

    Li, D.; Ning, Z. J.; Zhang, Q. M.

    2015-07-01

    We explore the quasi-periodic pulsations (QPPs) in a solar flare observed by Fermi Gamma-ray Burst Monitor, Solar Dynamics Observatory, Solar Terrestrial Relations Observatory, and Interface Region Imaging Spectrograph (IRIS) on 2014 September 10. QPPs are identified as the regular and periodic peaks on the rapidly varying components, which are the light curves after removing the slowly varying components. The QPPs display only three peaks at the beginning on the hard X-ray emissions, but 10 peaks on the chromospheric and coronal line emissions, and more than seven peaks (each peak corresponds to a type III burst on the dynamic spectra) at the radio emissions. A uniform quasi-period of about 4 minutes is detected among them. AIA imaging observations exhibit that the 4-minute QPPs originate from the flare ribbon and tend to appear on the ribbon front. IRIS spectral observations show that each peak of the QPPs tends to a broad line width and a red Doppler velocity at C i, O iv, Si iv, and Fe xxi lines. Our findings indicate that the QPPs are produced by the non-thermal electrons that are accelerated by the induced quasi-periodic magnetic reconnections in this flare.

  11. THEMIS Observations of Unusual Bow Shock Motion, Attending a Transient Magnetospheric Event

    NASA Technical Reports Server (NTRS)

    Korotova, Galina; Sibeck, David; Omidi, N.; Angelopoulos, V.

    2013-01-01

    We present a multipoint case study of solar wind and magnetospheric observations during a transient magnetospheric compression at 2319 UT on October 15, 2008. We use high-time resolution magnetic field and plasma data from the THEMIS and GOES-11/12 spacecraft to show that this transient event corresponded to an abrupt rotation in the IMF orientation, a change in the location of the foreshock, and transient outward bow shock motion. We employ results from a global hybrid code model to reconcile the observations indicating transient inward magnetopause motion with the outward bow shock motion.

  12. New Space Shuttle Observations of Transient Luminous Events During the MEIDEX

    NASA Astrophysics Data System (ADS)

    Yair, Y.; Price, C.; Israelevitch, P.; Devir, A.; Moalem, M.; Ziv, B.; Levin, Z.; Joseph, J.

    2003-12-01

    The Mediterranean Israeli Dust Experiment (MEIDEX) was conducted on-board the space shuttle Columbia during its last mission in January 2003. Nocturnal observations with a multispectral CCD video camera were targeted above thunderstorms near the Earth's limb, with the aim or recording Transient Luminous Events (TLEs) in the mesosphere. Most of our nighttime observations were conducted in the SE-Pacific (Australia and Papua-New Guinea), equatorial Africa, the southern Indian Ocean and South America. Relevant inputs and information on the active storms during a specific orbit were uplinked to the crew daily. The necessary shuttle attitude maneuvers were deduced based on the use of (almost) real-time IR satellite images and VLF lightning location data that were available on the Internet. In order to enhance the probability of success of each observation, the astronauts were instructed to visually observe lightning activity (easily discernable from the shuttle) and to direct the gimbaled camera toward these regions. A total of more than 8 hours of video obtained during the MEIDEX was saved, and it includes a considerable amount of new sprite data. Most events were captured at ranges 1600-1900 km from the shuttle, using the red filter (665nm). The results suggest the occurrence rate of sprites and elves over oceanic and continental storms may be higher than earlier estimates. Strong enhancements of the brightness of the airglow layer above lightning flashes were observed, with lateral dimensions on the order of 400-500 km. It is assumed that these may be Elves observed edge-on, though it may also be a new type of airglow enhancement. The calculated brightness of these events is in the range 2.2-8.8 MR. This phenomena seems to be widespread and is probably a manifestation of the interaction between lightning EMP and QE fields and the lower nocturnal ionosphere. A unique observation from space of the Congo basin in Africa caught a chain of events where in the span of less

  13. Local Scale Radiobrightness Modelling during Intensive Observing Period-4 of the Cold Land Processes Experiment-1

    NASA Technical Reports Server (NTRS)

    Kim, Edward J.; Tedesco, Marco; deRoo, Roger; England, Anthony W.; Gu, Haoyu; Pham, Hanh; Boprie, David; Graf, Tobias; Koike, Toshio; Armstrong, Richard

    2004-01-01

    The NASA Cold Land Processes Field Experiment (CLPX-1) was designed to provide microwave remote sensing observations and ground truth for studies of snow and frozen ground remote sensing, particularly issues related to scaling. CLPX-1 was conducted in the spring of 2003 in Colorado, USA. Initial forward model validation work is concentrating on the Local-Scale Observation Site (LSOS), a 0.8 ha study site consisting of open meadows separated by trees where the most detailed measurements were made of snow depth and temperature, density, and grain size profiles. This paper will focus on the ability of forward Dense Medium Radiative Transfer (DMRT) modelling, combined with snowpack measurements to reproduce the radiobrightness signatures observed by the University of Michigan s Truck-Mounted Radiometer System at 19 and 37 GHz during the 4th Intensive Observing Period (IOP4) in March, 2003. Unlike the earlier IOP3, conditions during IOP4 include both wet and dry periods, providing a valuable test of DMRT model performance. Observations of upwelling and downwelling tree radiobrightness will be used to formulate a simple model for the effect of trees within the field of view. In addition, a comparison will be made for the one day of coincident observations by the University of Tokyo s Ground- Based Microwave Radiometer-7 (GBMR-7). These analyses will help guide the choice of future snow retrieval algorithms and the design of future Cold Lands observing systems.

  14. Observations of long-period Cepheids between l = 294 and 331 deg

    NASA Technical Reports Server (NTRS)

    Grayzeck, E. J.

    1978-01-01

    Photoelectric and spectroscopic observations of long-period Cepheids, as well as 21-cm profiles in the directions of these young stars, are presented for the Crux-Centaurus-Circinus-Norma section of the Milky Way. The UBV data have been used to revise periods and light-curve parameters and ultimately to calculate the distances of these stars. From the spectroscopic information velocity estimates have been made. Finally, the stellar velocities have been compared with H I gas motions detected along the same line of sight. These results are briefly discussed with a view to understanding the spiral structure of the region.

  15. Observation of periodic waves in a pulse-coupled neural network.

    PubMed

    Johnson, J L; Ritter, D

    1993-08-01

    A pulse-coupled neural network was implemented, for the first time to our knowledge, in a hybrid electro-optical laboratory demonstration system. Dynamic coherent traveling-wave patterns were observed that repeated their spatial patterns at each locality with a period that depended on the local input pattern and strength. Coherence and periodicity were maintained far beyond the physical limits of the linking receptive fields, suggesting a new mechanism for information transmission in a network with limited local connectivity. With no linking, the output became chaotic because the relative phases increased linearly in time.

  16. Determination of solar wind elemental abundances from M/Q observations during three periods in 1980

    NASA Astrophysics Data System (ADS)

    Kunz, S.; Bochsler, P.; Geiss, J.; Ogilvie, K. W.; Coplan, M. A.

    1983-10-01

    Mass spectra in the range 2 ≤ M/Q ≤ 3 provided by a high resolution mode of the ISEE-3 Plasma Composition Experiment were evaluated for three selected periods during early 1980. The observed Ne/O ratios are compatible with estimated solar abundance ratios. In two of the three periods, the He/Ne-ratios agree with the Apollo foil results. Freezing-in temperatures for oxygen are similar to those obtained by other groups. Possible reasons for an unexpectedly high flux at M/Q = 2.4 are discussed.

  17. Time-varying autoregressive model for spectral analysis of microseismic experiments and long-period volcanic events

    NASA Astrophysics Data System (ADS)

    Tary, J. B.; Herrera, R. H.; van der Baan, M.

    2014-01-01

    Recent studies show that the frequency content of continuous passive recordings contains useful information for the study of hydraulic fracturing experiments as well as longstanding applications in volcano and global seismology. The short-time Fourier transform (STFT) is usually used to obtain the time-frequency representation of a seismic trace. Yet, this transform has two main disadvantages, namely its fixed time-frequency resolution and spectral leakage. Here, we describe two methods based on autoregressive (AR) models: the short-time autoregressive method (ST-AR) and the Kalman smoother (KS). These two methods allow for the AR coefficients to vary over time in order to follow time-varying frequency contents. The outcome of AR methods depends mainly on the number of AR coefficients. We use a robust approach to estimate the optimum order of the AR methods that best matches the spectral comparison between Fourier and AR spectra. Comparing the outcomes of the three methods on a synthetic signal, a long-period volcanic event, and microseismic data, we show that the STFT and both AR methods are able to track fast changes in frequency content. The STFT provides reasonable results even for noisy data using a simple and effective algorithm. The coefficients of the AR filter are defined at all time in the case of the KS. However, its better time resolution is slightly offset by a lower frequency resolution and its computational complexity. The ST-AR has a high spectral resolution and the lowest sensitivity to background noises, facilitating the identification of the various frequency components. The estimated AR coefficients can also be used to extract parts of the signal. The study of long-term phenomena, such as resonance frequencies, or transient events, such as long-period events, could help to gain further insight on reservoir deformation during hydraulic fracturing experiments as well as global or volcano seismological signals.

  18. Mechanisms and Observations of Coronal Dimming for the 2010 August 7 Event

    NASA Astrophysics Data System (ADS)

    Mason, James Paul; Woods, T. N.; Caspi, A.; Thompson, B. J.; Hock, R. A.

    2014-07-01

    Coronal dimming of extreme ultraviolet (EUV) emission has the potential to be a useful forecaster of coronal mass ejections (CMEs). As emitting material leaves the corona, a temporary void is left behind which can be observed in spectral images and irradiance measurements. The velocity and mass of the CMEs should impact the character of those observations. However, other physical processes can confuse the observations. We describe these processes and the expected observational signature, with special emphasis placed on the differences. We then apply this understanding to a coronal dimming event with an associated CME that occurred on 2010 August 7. Data from the Solar Dynamics Observatory's Atmospheric Imaging Assembly and EUV Variability Experiment (EVE) are used for observations of the dimming, while the Solar and Heliospheric Observatory's Large Angle and Spectrometric Coronagraph and the Solar Terrestrial Relations Observatory's COR1 and COR2 are used to obtain velocity and mass estimates for the associated CME. We develop a technique for mitigating temperature effects in coronal dimming from full-disk irradiance measurements taken by EVE. We find that for this event, nearly 100% of the dimming is due to mass loss in the corona.

  19. Mechanisms and Observations of Coronal Dimming for the 2010 August 7 Event

    NASA Technical Reports Server (NTRS)

    Mason, James P.; Woods, Thomas N.; Caspi, Amir; Thompson, Barbara J.; Hock, Rachel A.

    2014-01-01

    Coronal dimming of extreme ultraviolet (EUV) emission has the potential to be a useful forecaster of coronal mass ejections (CMEs). As emitting material leaves the corona, a temporary void is left behind which can be observed in spectral images and irradiance measurements. The velocity and mass of the CMEs should impact the character of those observations. However, other physical processes can confuse the observations. We describe these processes and the expected observational signature, with special emphasis placed on the differences. We then apply this understanding to a coronal dimming event with an associated CME that occurred on 2010 August 7. Data from the Solar Dynamics Observatory's (SDO) Atmospheric Imaging Assembly (AIA) and EUV Variability Experiment (EVE) are used for observations of the dimming, while the Solar and Heliospheric Observatory's (SoHO) Large Angle and Spectrometric Coronagraph (LASCO) and the Solar Terrestrial Relations Observatory's (STEREO) COR1 and COR2 are used to obtain velocity and mass estimates for the associated CME. We develop a technique for mitigating temperature effects in coronal dimming from full-disk irradiance measurements taken by EVE. We find that for this event, nearly 100% of the dimming is due to mass loss in the corona.

  20. The blue luminous events observed by ISUAL payload on board FORMOSAT-2 satellite

    NASA Astrophysics Data System (ADS)

    Kuo, C. L.; Su, H. T.; Hsu, R. R.

    2015-11-01

    We report the blue luminous events observed by the Imager of Sprite/Upper Atmospheric Lightning (ISUAL) payload on board the FORMOSAT-2 satellite. The ISUAL 427.8 nm filtered Imager campaign was conducted near Australia in the summer of the Southern Hemisphere during February-March 2008. On 18 February 2008, the 427.8 nm filtered Imager recorded a series of blue luminous events. One blue starter and nine smaller blue starters were recorded in 2 min and 34 s in a localized region with the radius < 4 km over the cloud top. The average time interval between subsequent blue luminous events was ~ 17 s. The occurrence rate of blue luminous events was 3.5 events per minute, slightly lower than the occurrence rate of pixies (4.2 events per minute) but higher than the occurrence rate of gnomes and blue jets in the previous observations. The recorded first blue starter lasted up to 2-3 frame times (60-90 ms) and extended its altitude about 8 ± 0.3 km with a width of ~2-4 km over the cloud top. After the first blue starter, subsequent nine smaller blue starters had the decreased heights of ~2-4 km, and their optical duration was shorter and is down to 1 ms. But their major emissions were 2PN2 and 1NN2+, without lightning OI 777.4 nm emission. The ISUAL recorded blue smaller starters had the spatial average brightness of 130 kR for the 427.8 nm filtered Imager with exposure time (29 ms) and 1.2 MR for the spectrophotometer (337 nm). Using the spectrophotometer, the emission time of blue starters was 1 ms. It is estimated that the 1NN2+ emission was ~ 22 MR and the 2PN2 emission was ~ 132 MR. We can estimate the degree of ionization was 10-11-10-12 in these blue luminous events using the 427.8 nm filtered Imager measured 1NN2+ (0,1) emission.

  1. Source mechanism of long-period events at Kusatsu-Shirane Volcano, Japan, inferred from waveform inversion of the effective excitation functions

    USGS Publications Warehouse

    Nakano, M.; Kumagai, H.; Chouet, B.A.

    2003-01-01

    We investigate the source mechanism of long-period (LP) events observed at Kusatsu-Shirane Volcano, Japan, based on waveform inversions of their effective excitation functions. The effective excitation function, which represents the apparent excitation observed at individual receivers, is estimated by applying an autoregressive filter to the LP waveform. Assuming a point source, we apply this method to seven LP events the waveforms of which are characterized by simple decaying and nearly monochromatic oscillations with frequency in the range 1-3 Hz. The results of the waveform inversions show dominant volumetric change components accompanied by single force components, common to all the events analyzed, and suggesting a repeated activation of a sub-horizontal crack located 300 m beneath the summit crater lakes. Based on these results, we propose a model of the source process of LP seismicity, in which a gradual buildup of steam pressure in a hydrothermal crack in response to magmatic heat causes repeated discharges of steam from the crack. The rapid discharge of fluid causes the collapse of the fluid-filled crack and excites acoustic oscillations of the crack, which produce the characteristic waveforms observed in the LP events. The presence of a single force synchronous with the collapse of the crack is interpreted as the release of gravitational energy that occurs as the slug of steam ejected from the crack ascends toward the surface and is replaced by cooler water flowing downward in a fluid-filled conduit linking the crack and the base of the crater lake. ?? 2003 Elsevier Science B.V. All rights reserved.

  2. Imaging Observations of Quasi-periodic Pulsations in Solar Flare Loops with SDO/AIA

    NASA Astrophysics Data System (ADS)

    Su, J. T.; Shen, Y. D.; Liu, Y.; Liu, Y.; Mao, X. J.

    2012-08-01

    Quasi-periodic pulsations (QPPs) of flaring emission with periods from a few seconds to tens of minutes have been widely detected from radio bands to γ-ray emissions. However, in the past the spatial information of pulsations could not be utilized well due to the instrument limits. We report here imaging observations of the QPPs in three loop sections during a C1.7 flare with periods of P = 24 s-3 minutes by means of the extreme-ultraviolet 171 Å channel of the Atmospheric Imaging Assembly (AIA) instrument on board the Solar Dynamics Observatory. We confirm that the QPPs with the shortest period of 24 s were not of an artifact produced by the Nyquist frequency of the AIA 12 s cadence. The QPPs in the three loop sections were interconnected and closely associated with the flare. The detected perturbations propagated along the loops at speeds of 65-200 km s-1, close to those of acoustic waves in them. The loops were made up of many bright blobs arranged in alternating bright and dark changes in intensity (spatial periodical distribution) with the wavelengths 2.4-5 Mm (as if they were magnetohydrodynamic waves). Furthermore, in the time-distance diagrams, the detected perturbation wavelengths of the QPPs are estimated to be ~10 Mm, which evidently do not fit the above ones of the spatial periodic distributions and produce a difference of a factor of 2-4 with them. It is suggested that the short QPPs with periods P < 60 s were possibly sausage-mode oscillations and the long QPPs with periods P > 60 s were the higher (e.g., >2nd) harmonics of slow magnetoacoustic waves.

  3. Identifying the occurrence of lightning and transient luminous events by nadir spectrophotometric observation

    NASA Astrophysics Data System (ADS)

    Adachi, Toru; Sato, Mitsuteru; Ushio, Tomoo; Yamazaki, Atsushi; Suzuki, Makoto; Kikuchi, Masayuki; Takahashi, Yukihiro; Inan, Umran S.; Linscott, Ivan; Hobara, Yasuhide; Frey, Harald U.; Mende, Stephen B.; Chen, Alfred B.; Hsu, Rue-Ron; Kusunoki, Kenichi

    2016-07-01

    We propose a new technique to identify the occurrence of lightning and transient luminous events (TLEs) using multicolor photometric data obtained by space borne nadir measurements. We estimate the spectral characteristics of lightning and TLEs by converting the optical data obtained by the ISUAL limb experiment to the GLIMS nadir geometry. We find that the estimated spectral shapes of TLE-accompanied lightning are clearly different from those of pure lightning. The obtained results show that (1) the intensity of FUV signals and (2) the ratio of 337/red (609-753 nm) spectral irradiance are useful to identify the occurrence of TLEs. The occurrence probabilities of TLEs are 10%, 40%, 80%, in the case of lightning events having the 337/red spectral irradiance ratio of 0.95, 2.95, 14.79, respectively. By using the 60% criterion of the 337/red ratio and the existence of FUV emissions, we classify the 1039 GLIMS-observed lightning events into 828 pure lightning and 211 TLE-accompanied lightning. Since the GLIMS trigger level is adjusted to observe extremely-bright events, the occurrence probability of TLEs obtained here most probably reflects the characteristics of energetic lightning. The estimated global map is consistent with previously determined distributions: the highest activities of lightning and TLEs are found over the North/South American continents, African continent, and Asian maritime regions. While the absolute occurrence number of pure lightning and TLE-accompanied lightning are found to maximize in the equatorial region, the occurrence probability of TLEs possibly increase somewhat in the mid-latitude region. Since the occurrence probabilities of TLEs are higher over the ocean than over land, it is likely that the GLIMS-observed TLEs are due primarily to elves which tends to occur more frequently over the ocean.

  4. River flood events in Thailand and Bangladesh observed by CryoSat

    NASA Astrophysics Data System (ADS)

    Andersen, O. B.; Nielsen, K.; Villadsen, H.; Stenseng, L.; Knudsen, P.

    2014-12-01

    The high along track resolution of the SIRAL altimeter carried on-board CryoSat-2 offers a wide range of unique opportunities for satellite monitoring of inland water level. This study focuses on the ability of CryoSat-2 to detect the effects of flood events such as increased river levels and inundation of land. Here we study two flood events; the Bangladesh flood event of June 2012 and the flooding in Thailand that lasted between July 2011 and January 2012. The flooding in these areas was caused by abnormal monsoonal rainfall and affected millions of people. We process CryoSat-2 level 1b SAR mode data to derive water levels for the areas and compare these levels before, during and after the flooding events. Other parameters such as the backscatter coefficient and pulse peakiness are also considered. To verify the extent of the flooding observed by CryoSat-2 we compare with independent sources such as Landsat images.

  5. Microlensing events from the 11-year Observations of the Wendelstein Calar Alto Pixellensing Project

    NASA Astrophysics Data System (ADS)

    Lee, C.-H.; Riffeser, A.; Seitz, S.; Bender, R.; Koppenhoefer, J.

    2015-06-01

    We present the results of the decade-long M31 observation from the Wendelstein Calar Alto Pixellensing Project (WeCAPP). WeCAPP has monitored M31 from 1997 until 2008 in both R- and I-filters, and thus provides the longest baseline of all M31 microlensing surveys. The data are analyzed with difference imaging analysis, which is most suitable for studying variability in crowded stellar fields. We extracted light curves based on each pixel, and devised selection criteria that are optimized to identify microlensing events. This leads to 10 new events, and adds up to a total of 12 microlensing events from WeCAPP, for which we derive their timescales, flux excesses, and colors from their light curves. The colors of the lensed stars fall in the range (R - I) = 0.56 to 1.36, with a median of 1.0 mag, in agreement with our expectation that the sources are most likely bright, red stars at the post-main-sequence stage. The event FWHM timescales range from 0.5 to 14 days, with a median of 3 days, in good agreement with predictions based on the model of Riffeser et al.

  6. Stable time patterns of railway suicides in Germany: comparative analysis of 7,187 cases across two observation periods (1995–1998; 2005–2008)

    PubMed Central

    2014-01-01

    Background The majority of fatalities on the European Union (EU) railways are suicides, representing about 60% of all railway fatalities. The aim of this study was to compare time patterns of suicidal behaviour on railway tracks in Germany between two observation periods (1995–1998 and 2005–2008) in order to investigate their stability and value in railway suicide prevention. Methods Cases were derived from the National Central Registry of person accidents on the German railway network (STABAG). The association of daytime, weekday and month with the mean number of suicides was analysed applying linear regression. Potential differences by observation period were assessed by adding observation period and the respective interaction terms into the linear regression. A 95% confidence interval for the mean number of suicides was computed using the t distribution. Results A total of 7,187 railway suicides were recorded within both periods: 4,102 (57%) in the first period (1995–1998) and 3,085 (43%) in the second (2005–2008). The number of railway suicides was highest on Mondays and Tuesdays in the first period with an average of 3.2 and 3.5 events and of 2.6 events on both days in the second period. In both periods, railway suicides were more common between 6:00 am and noon, and between 6:00 pm and midnight. Seasonality was only prominent in the period 1995–1998. Conclusions Over the course of two observation periods, the weekday and circadian patterns of railway suicides remained stable. Therefore, these patterns should be an integral part of railway suicide preventive measures, e.g. gatekeeper training courses. PMID:24498876

  7. Nitric oxide increase observed following the July 1982 solar proton event

    SciTech Connect

    McPeters, R.D.

    1986-07-01

    Following the solar proton event (SPE) of July 13, 1982, an increase in the strength of nitric oxide GAMMA bands was observed in spectral scans of the atmospheric albedo made by the solar backscattered ultraviolet instrument on Nimbus 7. Analysis of the (10), (01), and (02) GAMMA band strengths allows us to estimate the cumulative amount of nitric oxide above an altitude of 50 km. We observe an increase in nitric oxide in southern hemisphere high latitudes following the SPE amounting to about 5 x 10/sup 14/ molecules per cm/sup 2/ above an altitude of approximately 50 km. The observed increase persists until the middle of September. A similar increase is not observed in the northern hemisphere, indicating that under summer conditions the mesospheric/thermospheric NO distribution returns to normal within a few days after the end of an SPE.

  8. Simultaneous observation of whistlers and emissions during a geomagnetically quiet period at low latitude

    NASA Astrophysics Data System (ADS)

    Singh, Ashutosh K.; Singh, K. K.; Singh, A. K.; Lalmani

    2011-02-01

    A unique night-time natural electromagnetic disturbances in the VLF/ELF range received during a magnetically quite period at a low latitude Indian ground station, Jammu (geomag. lat. 19°26' N, L=1.17) has been reported. During the routine observation of VLF waves at Jammu, whistlers and different types of VLF/ELF emissions such as whistlers of varying dispersion confined to a small band limited frequency range, hisslers, pulsing hiss, discrete chorus emissions of rising and falling tones with multiple bands, oscillating tone discrete emission, whistler-triggered hook and discrete chorus risers emissions, etc. have been observed simultaneously during the quiet period on a single night. Such type of unique simultaneous observations has never been reported from any of the low latitude ground stations and this is the first observation of its kind. The results are discussed in the light of recorded features of whistlers and emissions. Generation and propagation mechanism are discussed briefly. Plasma parameters are further derived from the dispersion analysis of nighttime whistlers and emissions recorded simultaneously during magnetically quiet periods.

  9. Rayleigh/raman Greenland Lidar Observations of Atmospheric Temperature During a Major Arctic Stratospheric Warming Event

    NASA Technical Reports Server (NTRS)

    Meriwether, John W.; Farley, Robert; Mcnutt, R.; Dao, Phan D.; Moskowitz, Warren P.

    1992-01-01

    Between Jan. 22 1991 to Feb. 5 1991, we made numerous observations of atmospheric temperature profiles between 10 and 70 km by using the combination of Rayleigh and Raman lidar systems contained in the PL Mobile Lidar Facility located at the National Science Foundation Incoherent Radar Facility of Sondrestrom in Greenland. The purpose of these measurements was to observe the dynamics of the winter Arctic stratosphere and mesosphere regions during a winter period from the succession of temperature profiles obtained in our campaign observations. Various aspects of this investigation are presented.

  10. Aerosol and Cloud-Nucleating Particle Observations during an Atmospheric River Event

    NASA Astrophysics Data System (ADS)

    DeMott, P. J.; McCluskey, C. S.; Petters, M.; Suski, K. J.; Levin, E. J.; Hill, T. C. J.; Atwood, S. A.; Schill, G. P.; Rocci, K.; Boose, Y.; Martin, A.; Cornwell, G.; Al-Mashat, H.; Moore, K.; Prather, K. A.; Rothfuss, N.; Taylor, H.; Leung, L. R.; Tomlinson, J. M.; Mei, F.; Hubbe, J. M.; Rosenfeld, D.; Spackman, J. R.; Fairall, C. W.; Creamean, J.; White, A. B.; Kreidenweis, S. M.

    2015-12-01

    The multi-agency CalWater 2015 project occurred over North Central CA and the Eastern Pacific during January to March 2015 (Spackman et al., this session). The goals of the campaign were to document the structure of atmospheric rivers (ARs) that deliver much of the water vapor associated with major winter storms along the U.S. West Coast and to investigate the modulating effect of aerosols on precipitation. Aerosol sources that may influence orographic cloud properties for air lifted over the mountains in California in winter include pollution, biomass burning, soil dusts and marine aerosols, but their roles will also be influenced by transport, vertical stratification, and scavenging processes. We present results from a comprehensive study of aerosol distributions, compositions, and cloud nucleating properties during an intense winter storm during February 2015, including data from an NSF-supported measurement site at Bodega Bay, from the DOE-ARM Cloud Aerosol Precipitation Experiment that included sampling on the NOAA RV Ron Brown offshore and the G-1 aircraft over ocean and land, and with context provided by other NOAA aircraft and remote sensing facilities. With a special focus on the coastal site, we discuss changes in aerosol distributions, aerosol hygroscopicity, and number concentrations of fluorescent particles, cloud condensation nuclei (CCN), and ice nucleating particles (INPs) during the AR event. We compare with periods preceding and following the event. For example, total aerosol number and surface area concentrations at below 0.5 μm diameter decreased from typical values of a few thousand cm-3 and 100 μm2 cm-3, respectively, to a few hundred cm-3 and 10 μm2cm-3 at Bodega Bay during the AR event. CCN concentrations were similarly lower, but hygroscopicity parameter (kappa) increased from typical values of 0.2 to values > 0.5 during the AR.INP and fluorescent particle number concentrations were generally lower during the AR event than at any other

  11. AMPTE IRM observations of waves associated with flux transfer events in the magnetosphere

    NASA Technical Reports Server (NTRS)

    Labelle, J.; Treumann, R. A.; Haerendel, G.; Bauer, O. H.; Paschmann, G.

    1987-01-01

    The AMPTE IRM wave instrument has been applied to the study of flux transfer events (FTE's). This initial investigation concentrates on FTE's observed in the magnetosphere during the fall of 1984. The wave morphology consists of four significant features: at frequencies below the ion gyrofrequency, magnetic fluctuations occur with amplitudes of the order of 1 nT; at frequencies from a few hertz to a few hundred hertz, electric field fluctuations are observed which have a broadband amplitude of a few millivolts per meter, which are perpendicularly polarized at the lowest frequencies, and which are partly electrostatic and partly electromagnetic; in the frequency range from 100 Hz to 10 kHz, broadband spikelike waves occur with a time-averaged amplitude of about 0.1 mV/m; and near the electron plasma frequency, bursts of waves occur at the boundaries of FTE's. In none of the 25 events surveyed does the total broadband amplitude of all the waves exceed a few millivolts per meter, an amplitude far too small to provide the dissipation required by 'traditional' reconnection models in which the dissipation region has a thickness the order of an ion gyroradius. Thus, either all of the FTE's are observed at some distance from the diffusion region, or the observable waves play no significant role in the diffusion process, or 'traditional' reconnection models do not apply to reconnection in FTE's.

  12. Observations and Analysis of Mutual Events between the Uranus Main Satellites

    NASA Astrophysics Data System (ADS)

    Assafin, M.; Vieira-Martins, R.; Braga-Ribas, F.; Camargo, J. I. B.; da Silva Neto, D. N.; Andrei, A. H.

    2009-04-01

    Every 42 years, the Earth and the Sun pass through the plane of the orbits of the main satellites of Uranus. In these occasions, mutual occultations and eclipses between these bodies can be seen from the Earth. The current Uranus equinox from 2007 to 2009 offers a precious opportunity to observe these events. Here, we present the analysis of five occultations and two eclipses observed from Brazil during 2007. For the reduction of the CCD images, we developed a digital coronagraphic method that removed the planet's scattered light around the satellites. A simple geometric model of the occultation/eclipse was used to fit the observed light curves. Dynamical quantities such as the impact parameter, the relative speed, and the central time of the event were then obtained with precisions of 7.6 km, 0.18 km s-1, and 2.9 s, respectively. These results can be further used to improve the parameters of the dynamical theories of the main Uranus satellites. Based on observations made at Laboratório Nacional de Astrofísica (LNA), Itajubá-MG, Brazil.

  13. Elemental GCR Observations during the 2009-2010 Solar Minimum Period

    NASA Technical Reports Server (NTRS)

    Lave, K. A.; Israel, M. H.; Binns, W. R.; Christian, E. R.; Cummings, A. C.; Davis, A. J.; deNolfo, G. A.; Leske, R. A.; Mewaldt, R. A.; Stone, E. C.; vonRosenvinge, T. T.; Wiedenbeck, M. E.

    2013-01-01

    Using observations from the Cosmic Ray Isotope Spectrometer (CRIS) onboard the Advanced Composition Explorer (ACE), we present new measurements of the galactic cosmic ray (GCR) elemental composition and energy spectra for the species B through Ni in the energy range approx. 50-550 MeV/nucleon during the record setting 2009-2010 solar minimum period. These data are compared with our observations from the 1997-1998 solar minimum period, when solar modulation in the heliosphere was somewhat higher. For these species, we find that the intensities during the 2009-2010 solar minimum were approx. 20% higher than those in the previous solar minimum, and in fact were the highest GCR intensities recorded during the space age. Relative abundances for these species during the two solar minimum periods differed by small but statistically significant amounts, which are attributed to the combination of spectral shape differences between primary and secondary GCRs in the interstellar medium and differences between the levels of solar modulation in the two solar minima. We also present the secondary-to-primary ratios B/C and (Sc+Ti+V)/Fe for both solar minimum periods, and demonstrate that these ratios are reasonably well fit by a simple "leaky-box" galactic transport model that is combined with a spherically symmetric solar modulation model.

  14. BAYESIAN ANALYSIS OF REPEATED EVENTS USING EVENT-DEPENDENT FRAILTY MODELS: AN APPLICATION TO BEHAVIORAL OBSERVATION DATA

    PubMed Central

    Snyder, James

    2009-01-01

    In social interaction studies, one commonly encounters repeated displays of behaviors along with their duration data. Statistical methods for the analysis of such data use either parametric (e.g., Weibull) or semi-nonparametric (e.g., Cox) proportional hazard models, modified to include random effects (frailty) which account for the correlation of repeated occurrences of behaviors within a unit (dyad). However, dyad-specific random effects by themselves are not able to account for the ordering of event occurrences within dyads. The occurrence of an event (behavior) can make further occurrences of the same behavior to be more or less likely during an interaction. This paper develops event-dependent random effects models for analyzing repeated behaviors data using a Bayesian approach. The models are illustrated by a dataset relating to emotion regulation in families with children who have behavioral or emotional problems. PMID:20161593

  15. Bayesian Hierarchical Duration Model for Repeated Events : An Application to Behavioral Observations

    PubMed Central

    Dagne, Getachew A.; Snyder, James

    2009-01-01

    This paper presents a continuous-time Bayesian model for analyzing durations of behavior displays in social interactions. Duration data of social interactions are often complex because of repeated behaviors (events) at individual or group (e.g., dyad) level, multiple behaviors (multistates), and several choices of exit from a current event (competing risks). A multilevel, multistate model is proposed to adequately characterize the behavioral processes. The model incorporates dyad-specific and transition-specific random effects to account for heterogeneity among dyads and interdependence among competing risks. The proposed method is applied to child-parent observational data derived from the School Transitions Project to assess the relation of emotional expression in child-parent interaction to risk for early and persisting child conduct problems. PMID:20209032

  16. Periodicity in the occurrence of equatorial plasma bubbles derived from the C/NOFS observations in 2008-2012

    NASA Astrophysics Data System (ADS)

    Choi, Jong-Min; Kil, Hyosub; Kwak, Young-Sil; Park, Jaeheung; Lee, Woo Kyoung; Kim, Yong Ha

    2017-01-01

    The quasi-periodic occurrence of equatorial plasma bubbles is understood in terms of seeding mechanisms in the bottomside F region. However, no quantitative investigation has been conducted to identify how often quasi-periodic bubbles occur. This study investigates the wave property in the bubble occurrence (or spacing between bubbles) using the measurements of the plasma density in 2008-2012 by the Planar Langmuir Probe on board the Communication/Navigation Outage Forecasting System (C/NOFS) satellite. The wave property is investigated using the Lomb-Scargle periodograms derived from 664 segments of series of bubbles. In the majority of segments, the spacing between bubbles is represented by the combination of several wave components. Periodic bubbles whose property is represented by a few pronounced wave components are rare events. These results indicate that the spacing between bubbles is generally irregular. The manner of bubble occurrence does not show any notable variation with longitude and season. Because a consistent wave property does not exist in the occurrence of bubbles and the appearance of bubbles in the topside is affected by many factors, the manner of bubble occurrence in satellite observations does not provide a precise diagnostic of seeding mechanisms.

  17. Jellyfish: Observational Properties of Extreme Ram-Pressure Stripping Events in Massive Galaxy Clusters

    NASA Astrophysics Data System (ADS)

    Conor, McPartland; Ebeling, Harald; Roediger, Elke

    2015-08-01

    We investigate the physical origin and observational signatures of extreme ram-pressure stripping (RPS) in 63 massive galaxy clusters at z=0.3-0.7, based on data in the F606W passband obtained with the Advanced Camera for Surveys aboard the Hubble Space Telescope. Using a training set of a dozen ``jellyfish" galaxies identified earlier in the same imaging data, we define quantitative morphological criteria to select candidate galaxies which are similar to known cases of RPS. Considering a sample of 16 ``jellyfish" galaxies (10 of which we present for the first time), we visually derive estimates of the projected direction of motion based on dynamical features such as apparent compression shocks and debris trails. Our findings suggest that the observed events occur primarily at large distances from the cluster core and involve infall trajectories featuring high impact parameters. Simple models of cluster growth show that such trajectories are consistent with two scenarios: 1) galaxy infall along filaments; and 2) infall at high velocities (≥1000 km/s) characteristic of cluster mergers. The observed distribution of events is best described by timescales of ˜few Myr in agreement with recent numerical simulations of RPS. The broader areal coverage of the Hubble Frontier Fields should provide an even larger sample of RPS events to determine the relative contributions of infall and cluster mergers. Prompted by the discovery of several jellyfish galaxies whose brightness in the F606W passband rivals or exceeds that of the respective brightest cluster galaxy, we attempt to constrain the luminosity function of galaxies undergoing RPS. The observed significant excess at the bright end compared to the luminosity functions of blue cluster members strongly suggests enhanced star formation, thus challenging theoretical and numerical studies according to which RPS merely displaces existing star-forming regions. In-depth studies of individual objects will help test our

  18. First simultaneous observations of a near-relativistic electron spike event by both STEREO spacecraft

    NASA Astrophysics Data System (ADS)

    Klassen, A.; Dresing, N.; Gómez-Herrero, R.; Heber, B.

    2015-08-01

    Solar electron spike events are a special subclass of near-relativistic electron events characterized by their short duration, symmetric time profile, and their strong anisotropic pitch angle distribution. All previous studied events were only observed by a single spacecraft (s/c). For the first time, we present measurements of this kind of an electron spike event that was observed simultaneously by both close-spaced STEREO s/c on 2 May 2014. The longitudinal separation angle between STEREO-A (STA) and STEREO-B (STB) was 38°. The spikes at STA and STB are characterized by very short durations of ≤12 min at full-width at half maximum (FWHM) and almost identical and symmetric time profiles. They exhibit similar properties in durations, pitch angle distributions (PADs), energy spectra, and peak intensities. The spike parent source was situated close to the STA nominal magnetic footpoint and was separated by 48° from STB's footpoint. The intensity distribution and the relative onset timing behaved opposite to what is expected: STB measured a higher intensity and an earlier onset than the nominally better connected STA. We suggest that the spike electrons undergo a substantial nonradial injection into interplanetary (IP) space from the parent source, a flaring active region (AR), and propagate in a strong nonradial diverging magnetic field. In addition we show that because of the spike properties it is evident that, irrespective of how the electrons were injected into the IP medium, the en route particle scattering conditions along the paths to STA and STB were very similar. Evidently both s/c detected different parts of the same beam whose angular extension was at least 38° at 1 AU, comparable to the longitudinal separation between STA and STB.

  19. Transient Events in Archival Very Large Array Observations of the Galactic Center

    NASA Astrophysics Data System (ADS)

    Chiti, Anirudh; Chatterjee, Shami; Wharton, Robert; Cordes, James; Lazio, T. Joseph W.; Kaplan, David L.; Bower, Geoffrey C.; Croft, Steve

    2016-12-01

    The Galactic center has some of the highest stellar densities in the Galaxy and a range of interstellar scattering properties, which may aid in the detection of new radio-selected transient events. Here, we describe a search for radio transients in the Galactic center, using over 200 hr of archival data from the Very Large Array at 5 and 8.4 GHz. Every observation of Sgr A* from 1985 to 2005 has been searched using an automated processing and detection pipeline sensitive to transients with timescales between 30 s and 5 minutes with a typical detection threshold of ˜100 mJy. Eight possible candidates pass tests to filter false-positives from radio-frequency interference, calibration errors, and imaging artifacts. Two events are identified as promising candidates based on the smoothness of their light curves. Despite the high quality of their light curves, these detections remain suspect due to evidence of incomplete subtraction of the complex structure in the Galactic center, and apparent contingency of one detection on reduction routines. Events of this intensity (˜100 mJy) and duration (˜100 s) are not obviously associated with known astrophysical sources, and no counterparts are found in data at other wavelengths. We consider potential sources, including Galactic center pulsars, dwarf stars, sources like GCRT J1745-3009, and bursts from X-ray binaries. None can fully explain the observed transients, suggesting either a new astrophysical source or a subtle imaging artifact. More sensitive multiwavelength studies are necessary to characterize these events, which, if real, occur with a rate of {14}-12+32 {{hr}}-1 {\\deg }-2 in the Galactic center.

  20. Observation of new particle formation and growth events in Asian continental outflow

    NASA Astrophysics Data System (ADS)

    Kim, Yumi; Yoon, Soon-Chang; Kim, Sang-Woo; Kim, Kwang-Yul; Lim, Han-Cheol; Ryu, Jegyu

    2013-01-01

    This study is based on 3-year continuous measurements (January 2008-December 2010) of aerosol number size distributions recorded with a Scanning Mobility Particle Sizer (SMPS) at two regional background stations, Gosan Climate Observatory (GCO) and Korea Global Atmosphere Watch Center (KGAWC), in Korea. We identified new particle formation and growth (NPF) events by applying the Cyclostationary Empirical Orthogonal Function (CSEOF) technique to aerosol number size distributions. Based on the first mode loading vectors and the corresponding principle components in the CSEOF analysis, we classified strong, weak, and non NPF days. A strong NPF event was observed on 7.5% of days (60 days out of a total 800 days) at GCO and on 14.6% of days (140 days out of a total 958 days) at KGAWC. The maximum occurrence of strong NPF events was reported in spring at GCO, but in winter at KGAWC. Only 16 of these days were considered as simultaneous NPF events, and 7 days were identical NPF events. The airmass history analysis on simultaneous NPF days indicated the NPF events to be associated with a fast-moving cold and dry airmass from the Asian continent after the passage of a frontal system. The particle formation rate (FR) and growth rate (GR) were estimated to be 1.44 (1.20) cm-3 s-1 and 4.4 (4.7) nm h-1, respectively, at GCO and KGAWC (in parentheses). Almost identical values for the condensation sink were estimated in strong NPF (8.3 × 10-3 s-1) and non NPF (8.2 × 10-3 s-1) events at GCO, whereas the condensation sink for strong NPF days (8.5 × 10-5 s-1) was lower than that of non NPF days (1.1 × 10-2 s-1) at KGAWC. The FR, GR, condensation sink, and vapor source rate at both GCO and KGAWC were lower than those reported in polluted urban areas, but higher than those at clean sites.

  1. Calibration of Hipparcos Long Period Variable Start Fields Using Multi-Color CCD Observations

    NASA Astrophysics Data System (ADS)

    Howell, Steve B.; Mattei, Janet; Benson, Priscilla J.; Reyes, Adriana

    The first set of 4-color AAVSO CCD finder charts has been prepared using the 0.9-m telescope at Kitt peak national Observatory in Arizona. The stars selected were northern long period variable stars observed with the Hipparcos astrometric satellite, since multicolor photometry was needed on these stars to calibrate and reduce the photometric and astrometric data obtained by the satellite. We describe the criteria in choosing the stars for which to prepare CCD finder charts, the observation process, and the reduction of the CCD to obtain 4-color CCD magnitude sequences to use in the creation of AAVSO finder charts.

  2. Convective weather events in high-frequency Eulerian observations and model column outputs

    NASA Astrophysics Data System (ADS)

    Mapes, B.

    2006-05-01

    Convective cloud systems produce large fractions of the Earth's rainfall. High-frequency Eulerian time-height datasets containing such convective storm passages permit clean, objective comparisons between observations and model output. Lagged regressions of these datasets vs. surface rainfall are used to depict the characteristic structure of precipitating disturbances, mainly in the wet tropics. Both observations and models have organized convective rain events with time scales of many hours, even though convection parameterizations (and arguably cumulus cells in nature) operate column by column and typically have no long-time memory. However, different models have very different characteristic structures: very different from observations (which are fairly similar from place to place), and very different from other models. Experiments with single-column versions suggest that this characteristic structure stems largely from the physical parameterizations.

  3. First Ground-based Observation of Transient Luminous Events over Southern Africa

    NASA Astrophysics Data System (ADS)

    Nnadih, Ogechukwu; Kosch, Michael; Martinez, Peter

    2016-07-01

    We present the first ground-based observations in southern Africa of Transient Luminous Events (TLEs) in the summer of 2015/16 over convective thunderstorms. For the months of December to February, South Africa has one of the highest lightning stroke rates in the world. This was part of the AfriSprite campaign initiated by the South African National Space Agency. These observations show a variety of fine structures such as tree-like shaped, carrot, angel and jellyfish-shaped sprites. The South African Weather Service array of VLF receivers is used to locate and quantify the magnitude and polarity of the lightning strikes associated with TLEs. We plan to make bi-static as well as multi-wavelength observations in future.

  4. Observation of 13 mutual events of Jovian satellites performed at Lille Observatory

    NASA Astrophysics Data System (ADS)

    Vienne, A.; Noyelles, B.; Amossé, A.

    2003-10-01

    We have observed the four Galilean satellites of Jupiter during their mutual occultations and eclipses from February to April 2003 using a CCD camera attached to the 32.5 cm refractor of the observatory of Lille. We have recorded 13 lightcurves of these events. We have performed a first astrometric reduction based on the method developed in Noyelles et al. (2003). This analysis of the results and comparison with theory show that the observations are good; the residuals are about 0.03 arcsec. The observations are available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/410/343.

  5. Active Region Coronal Rain Event Observed by the Fast Imaging Solar Spectrograph on the NST

    NASA Astrophysics Data System (ADS)

    Ahn, Kwangsu; Chae, Jongchul; Cho, Kyung-Suk; Song, Donguk; Yang, Heesu; Goode, Philip R.; Cao, Wenda; Park, Hyungmin; Nah, Jakyung; Jang, Bi-Ho; Park, Young-Deuk

    2014-11-01

    The Fast Imaging Solar Spectrograph (FISS) is being operated on the New Solar Telescope of the Big Bear Solar Observatory. It simultaneously records spectra of Hα and Ca ii 8542 Å lines, and this dual-spectra measurement provides an estimate of the temperature and nonthermal speed components. We observed a loop structure in AR 11305 using the FISS, SDO/AIA, and STEREO/EUVI in 304 Å, and found plasma material falling along the loop from a coronal height into the umbra of a sunspot, which accelerated up to 80 km s-1. We also observed C2 and C7 flare events near the loop. The temperature of the downflows was in the range of 10 000 - 33 000 K, increasing toward the umbra. The temperature of the flow varied with time, and the temperature near the footpoint rose immediately after the C7 flare, but the temperature toward the umbra remained the same. There seemed to be a temporal correlation between the amount of downflow material and the observed C-class flares. The downflows decreased gradually soon after the flares and then increased after a few hours. These high-speed red-shift events occurred continuously during the observations. The flows observed on-disk in Hα and Ca ii 8542 Å appeared as fragmented, fuzzy condensed material falling from the coronal heights when seen off-limb with STEREO/EUVI at 304 Å. Based on these observations, we propose that these flows were an on-disk signature of coronal rain.

  6. Development of an event search and download system for analyzing waveform data observed at seafloor seismic network, DONET

    NASA Astrophysics Data System (ADS)

    Takaesu, M.; Horikawa, H.; Sueki, K.; Kamiya, S.; Nakamura, T.; Nakano, M.; Takahashi, N.; Sonoda, A.; Tsuboi, S.

    2014-12-01

    Mega-thrust earthquakes are anticipated to occur in the Nankai Trough in southwest Japan. In the source areas, we installed seafloor seismic network, DONET (Dense Ocean-floor Network System for Earthquake and Tsunamis), in 2010 in order to monitor seismicity, crustal deformations, and tsunamis. DONET system consists of totally 20 stations, which is composed of six kinds of sensors; strong-motion and broadband seismometers, quartz and differential pressure gauges, hydrophone, and thermometer. The stations are densely distributed with an average spatial interval of 15-20 km and cover near coastal areas to the trench axis. Observed data are transferred to a land station through a fiber-optical cable and then to JAMSTEC (Japan Agency for Marine-Earth Science and Technology) data management center through a private network in real time. The data are based on WIN32 format in the private network and finally archived in SEED format in the management center to combine waveform data with related metadata. We are developing a web-based application system to easily download seismic waveform data of DONET. In this system, users can select 20 Hz broadband (BH type) and 200 Hz strong-motion (EH type) data and download them in SEED. Users can also search events from the options of time periods, magnitude, source area and depth in a GUI platform. Event data are produced referring to event catalogues from USGS and JMA (Japan Meteorological Agency). The thresholds of magnitudes for the production are M6 for far-field and M4 for local events using the USGS and JMA lists, respectively. Available data lengths depend on magnitudes and epicentral distances. In this presentation, we briefly introduce DONET stations and then show our developed application system. We open DONET data through the system and want them to be widely recognized so that many users analyze. We also discuss next plans for further developments of the system.

  7. Unexpected spatial intensity distributions and onset timing of solar electron events observed by closely spaced STEREO spacecraft

    NASA Astrophysics Data System (ADS)

    Klassen, A.; Dresing, N.; Gómez-Herrero, R.; Heber, B.; Müller-Mellin, R.

    2016-09-01

    We present multi-spacecraft observations of four solar electron events using measurements from the Solar Electron Proton Telescope (SEPT) and the Electron Proton Helium INstrument (EPHIN) on board the STEREO and SOHO spacecraft, respectively, occurring between 11 October 2013 and 1 August 2014, during the approaching superior conjunction period of the two STEREO spacecraft. At this time the longitudinal separation angle between STEREO-A (STA) and STEREO-B (STB) was less than 72°. The parent particle sources (flares) of the four investigated events were situated close to, in between, or to the west of the STEREO's magnetic footpoints. The STEREO measurements revealed a strong difference in electron peak intensities (factor ≤12) showing unexpected intensity distributions at 1 AU, although the two spacecraft had nominally nearly the same angular magnetic footpoint separation from the flaring active region (AR) or their magnetic footpoints were both situated eastwards from the parent particle source. Furthermore, the events detected by the two STEREO imply a strongly unexpected onset timing with respect to each other: the spacecraft magnetically best connected to the flare detected a later arrival of electrons than the other one. This leads us to suggest the concept of a rippled peak intensity distribution at 1 AU formed by narrow peaks (fingers) superposed on a quasi-uniform Gaussian distribution. Additionally, two of the four investigated solar energetic particle (SEP) events show a so-called circumsolar distribution and their characteristics make it plausible to suggest a two-component particle injection scenario forming an unusual, non-uniform intensity distribution at 1 AU.

  8. Fluid dynamics beneath a wet volcano inferred from the complex frequencies of long-period (LP) events: An example from Papandayan volcano, West Java, Indonesia during the 2011 seismic unrest

    NASA Astrophysics Data System (ADS)

    Kamil Syahbana, Devy; Caudron, Corentin; Jousset, Philippe; Lecocq, Thomas; Camelbeeck, Thierry; Bernard, Alain; Surono, Surono

    2014-05-01

    We present results of our study aiming at understanding the dynamics of fluids beneath a wet volcano through the analysis of swarms of long-period (LP) events accompanying the 2011 seismic unrest at Papandayan volcano, West Java, Indonesia. Prior to this unrest, we measured a large amount (100%) of CO2 in the ground at the summit crater, however with very low value of SO2 (less than 10 tons/day). Increase in volcanic activity was also observed from the records of a tiltmeter. A long-term inflation was followed by an abrupt deflation which was concurrent with the swarms of LP events. Hereafter, swarms of volcano-tectonic (VT) and local-tectonic (LT) earthquakes started. We focus here on analyzing the LP events with the following manner. First, we estimate the source location of LP events by applying a non-linear hypocenter algorithm including topography. We then study the waveforms and spectral characteristics of LP events and investigate whether or not these events are due to source effect. We compute the complex frequencies (f and Q) for the coda of the LP events using the Sompi method and subsequently, we estimate the physical processes related to the observed temporal variations in the complex frequencies by following the fluid-filled crack model. We divide the swarms of LP events into two periods. The first period occurred between June and July 2011 (48 LP events) while the second period started from September to October 2011 (36 LP events). The dominant frequencies (f) of LP events observed during these periods range between 1.1 and 6.2 Hz while the attenuation factors (Q) are widely scattered between 20 and 400. We estimate the compositions of fluids inside the crack during both periods as either water foam (mixtures of water and H2O gas/steam) or misty gas (mixtures of water droplets and H2O gas/steam). We finally suggest that if an eruption would have taken place following the 2011 unrest, it would have been in phreatic style rather than magmatic style. The

  9. An observational study of the carrying capacity of suspended sediment during a storm event.

    PubMed

    Bian, Shuhua; Hu, Zejian; Xue, Zuo; Lv, Jingfu

    2012-10-01

    We measured the in situ suspended sediment concentration (SSC) and hydrodynamics (waves, currents, and sea level) concurrently during a storm event using self-recording instruments at offshore of the Shandong Peninsula in the Yellow Sea. We analyzed the temporal variation in suspended sediment carrying capacity and its correlation with wave, current, and water-level conditions. There was about 40% increase in SSC during the storm event. A 3-4-h lag was observed between the peak of wave height and SSC. The SSC increased in a fluctuating pattern up to the peak then decreased rapidly. This process was positively correlated with wave height and duration. The maximum SSC was 524.3 mg/l, which is about 10 times of that under normal weather conditions. This peak was observed after of a series of 1.8 m waves. The increased suspended sediments were the fine particles resuspended by the storm waves from seabed near the observation spot and transported by northward ebb currents from Shidao Bay.

  10. Three Dimensional Structure and Time Evolution of a Transition Region Explosive Event Observed in He II

    NASA Astrophysics Data System (ADS)

    Fox, J. L.; Kankelborg, C. C.; Thomas, R. J.; Longcope, D.

    2007-12-01

    Transition Region Explosive Events (TREEs) have been observed with slit spectrographs since at least 1975, most commonly in lines of C IV (1548A,1550A) and Si IV (1393A, 1402A). We report what we believe to be the first observation of a TREE in He II 304A. With the MOSES sounding rocket, a novel type of imaging spectrograph, we are able to see the spatial and spectral structure of the event. It consists of a bright core expelling two jets, oppositely directed but not collinear, which curve away from the axis of the core. The jets have both line-of-sight and sky-plane motion. The core is a region of high non-thermal doppler broadening, characteristic of TREEs. It is possible to resolve the core broadening into red and blue line-of-sight components. MOSES captured approximately 150 sec of time evolution before the rocket flight ended. We see the beginning (core activation) and middle (jet ejection), but not the end. It is clear from our data-set that TREEs in He II 304A are much less common than observed in other wavelengths.

  11. OBSERVATIONS AND ANALYSIS OF MUTUAL EVENTS BETWEEN THE URANUS MAIN SATELLITES

    SciTech Connect

    Assafin, M.; Vieira-Martins, R.; Braga-Ribas, F.; Camargo, J. I. B.; Da Silva Neto, D. N.; Andrei, A. H. E-mail: rvm@on.br

    2009-04-15

    Every 42 years, the Earth and the Sun pass through the plane of the orbits of the main satellites of Uranus. In these occasions, mutual occultations and eclipses between these bodies can be seen from the Earth. The current Uranus equinox from 2007 to 2009 offers a precious opportunity to observe these events. Here, we present the analysis of five occultations and two eclipses observed from Brazil during 2007. For the reduction of the CCD images, we developed a digital coronagraphic method that removed the planet's scattered light around the satellites. A simple geometric model of the occultation/eclipse was used to fit the observed light curves. Dynamical quantities such as the impact parameter, the relative speed, and the central time of the event were then obtained with precisions of 7.6 km, 0.18 km s{sup -1}, and 2.9 s, respectively. These results can be further used to improve the parameters of the dynamical theories of the main Uranus satellites.

  12. Compact object mergers: observations of supermassive binary black holes and stellar tidal disruption events

    NASA Astrophysics Data System (ADS)

    Komossa, S.; Zensus, J. A.

    2016-02-01

    The capture and disruption of stars by supermassive black holes (SMBHs), and the formation and coalescence of binaries, are inevitable consequences of the presence of SMBHs at the cores of galaxies. Pairs of active galactic nuclei (AGN) and binary SMBHs are important stages in the evolution of galaxy mergers, and an intense search for these systems is currently ongoing. In the early and advanced stages of galaxy merging, observations of the triggering of accretion onto one or both BHs inform us about feedback processes and BH growth. Identification of the compact binary SMBHs at parsec and sub-parsec scales provides us with important constraints on the interaction processes that govern the shrinkage of the binary beyond the ``final parsec''. Coalescing binary SMBHs are among the most powerful sources of gravitational waves (GWs) in the universe. Stellar tidal disruption events (TDEs) appear as luminous, transient, accretion flares when part of the stellar material is accreted by the SMBH. About 30 events have been identified by multi-wavelength observations by now, and they will be detected in the thousands in future ground-based or space-based transient surveys. The study of TDEs provides us with a variety of new astrophysical tools and applications, related to fundamental physics or astrophysics. Here, we provide a review of the current status of observations of SMBH pairs and binaries, and TDEs, and discuss astrophysical implications.

  13. Summer weather characteristics and periodicity observed over the period 1888-2013 in the region of Belgrade, Serbia

    NASA Astrophysics Data System (ADS)

    Vujović, Dragana; Todorović, Nedeljko; Paskota, Mira

    2017-02-01

    With the goal of finding summer climate patterns in the region of Belgrade (Serbia) over the period 1888-2013, different techniques of multivariate statistical analysis were used in order to analyze the simultaneous changes of a number of climatologic parameters. An increasing trend of the mean daily minimum temperature was detected. In the recent decades (1960-2013), this increase was much more pronounced. The number of days with the daily minimum temperature greater or equal to 20 °C also increased significantly. Precipitation had no statistically significant trend. Spectral analysis showed a repetitive nature of the climatologic parameters which had periods that roughly can be classified into three groups, with the durations of the following: (1) 6 to 7 years, (2) 10 to 18 years, and (3) 21, 31, and 41 years. The temperature variables mainly had one period of repetitiveness of 5 to 7 years. Among other variables, the correlations of regional fluctuations of the temperature and precipitation and atmospheric circulation indices were analyzed. The North Atlantic oscillation index had the same periodicity as that of the precipitation, and it was not correlated to the temperature variables. Atlantic multidecadal oscillation index correlated well to the summer mean daily minimum and summer mean temperatures. The underlying structure of the data was analyzed by principal component analysis, which detected the following four easily interpreted dimensions: More sunshine-Higher temperature, Precipitation, Extreme heats, and Changeable summer.

  14. Ground-based observations during the period between two strong November 2004 storms attributed to steady magnetospheric convection

    NASA Astrophysics Data System (ADS)

    Manninen, J.; Kleimenova, N. G.; Kozyreva, O. V.; Ranta, A.; Kauristie, K.; MäKinen, S.; Kornilova, T. A.

    2008-03-01

    Strong geomagnetic storms are of great scientific interest because they drive the magnetosphere to an extreme state and result in nontypical magnetosphere-ionosphere coupling. The present study examines the ground-based signatures of the magnetosphere-ionosphere disturbances during the recovery phase of the very intense storm on 7-8 November 2004. The recovery phase took place under steady and slightly negative (˜-5 nT) values of the IMF Bz. We compare this event with previously documented storm recovery phases occurring under positive IMF Bz and accompanied by morning Pc5 geomagnetic pulsations. During the period studied in this article the strongest pulsation activity was recorded in the evening and midnight sectors of the Earth. We analyze observations from the Scandinavian multipoint ground-based instrumentation: (1) geomagnetic variations and pulsations, (2) auroras in visual wavelengths, and (3) energetic particle precipitation (riometer data). We show that several enhancements in electrojet, auroral, and energetic precipitation activity were recorded at auroral latitudes. The activations lasted 0.5-2 hours, and the associated negative magnetic field deviations were often more than 1000 nT. Only one of these activations shows typical substorm behavior (poleward expansion and geostationary particle injection). We demonstrate remarkably good correlation between the magnetic variations and cosmic noise absorption variations (in pulsations and slower variations) as well as between the optical auroras and cosmic noise absorption (Imaging Riometer for Ionospheric Studies riometer system) both in time and in space. Thus the auroral precipitation revealed a very coherent behavior over a wide energy range (˜1-40 keV) during the analyzed period. The images acquired by the network of MIRACLE all-sky cameras show that the auroral distribution exhibited double oval configuration during our event. Double oval is often observed during so-called Steady Magnetospheric

  15. Ultraviolet Events Observed in Active Regions. 2; An Interpretation of Flaring Arches and Associated Small Flares

    NASA Technical Reports Server (NTRS)

    Fontenla, J.; Rovira, M.; Tandberg-Hanssen, E.

    1997-01-01

    We analyze Hz, UV, and X-ray emissions in and around the spectacular arch system seen in the corona on 1980 March 27 during the Solar Maximum Mission. The flaring of the arch plasma is studied, and its dependence on triggering mechanisms related to the observed small limb flare in the arch footpoint is analyzed. To drive these events, we propose a mechanism in which small electric current circuits and the localized magnetic free energy are continuously generated at a magnetic null by a pressure gradient, which then compress or expand the plasma. This free energy dissipates by Joule effect and upward transport.

  16. Observation of a significant excess of pi0pi0 events in B meson decays.

    PubMed

    Aubert, B; Barate, R; Boutigny, D; Gaillard, J-M; Hicheur, A; Karyotakis, Y; Lees, J P; Robbe, P; Tisserand, V; Zghiche, A; Palano, A; Pompili, A; Chen, J C; Qi, N D; Rong, G; Wang, P; Zhu, Y S; Eigen, G; Ofte, I; Stugu, B; Abrams, G S; Borgland, A W; Breon, A B; Brown, D N; Button-Shafer, J; Cahn, R N; Charles, E; Day, C T; Gill, M S; Gritsan, A V; Groysman, Y; Jacobsen, R G; Kadel, R W; Kadyk, J; Kerth, L T; Kolomensky, Yu G; Kral, J F; Kukartsev, G; LeClerc, C; Levi, M E; Lynch, G; Mir, L M; Oddone, P J; Orimoto, T J; Pripstein, M; Roe, N A; Romosan, A; Ronan, M T; Shelkov, V G; Telnov, A V; Wenzel, W A; Ford, K; Harrison, T J; Hawkes, C M; Knowles, D J; Morgan, S E; Penny, R C; Watson, A T; Watson, N K; Goetzen, K; Held, T; Koch, H; Lewandowski, B; Pelizaeus, M; Peters, K; Schmuecker, H; Steinke, M; Barlow, N R; Boyd, J T; Chevalier, N; Cottingham, W N; Kelly, M P; Latham, T E; Mackay, C; Wilson, F F; Abe, K; Cuhadar-Donszelmann, T; Hearty, C; Mattison, T S; McKenna, J A; Thiessen, D; Kyberd, P; McKemey, A K; Blinov, V E; Bukin, A D; Golubev, V B; Ivanchenko, V N; Kravchenko, E A; Onuchin, A P; Serednyakov, S I; Skovpen, Yu I; Solodov, E P; Yushkov, A N; Best, D; Bruinsma, M; Chao, M; Kirkby, D; Lankford, A J; Mandelkern, M; Mommsen, R K; Roethel, W; Stoker, D P; Buchanan, C; Hartfiel, B L; Shen, B C; Del Re, D; Hadavand, H K; Hill, E J; MacFarlane, D B; Paar, H P; Rahatlou, Sh; Sharma, V; Berryhill, J W; Campagnari, C; Dahmes, B; Kuznetsova, N; Levy, S L; Long, O; Lu, A; Mazur, M A; Richman, J D; Verkerke, W; Beck, T W; Beringer, J; Eisner, A M; Heusch, C A; Lockman, W S; Schalk, T; Schmitz, R E; Schumm, B A; Seiden, A; Turri, M; Walkowiak, W; Williams, D C; Wilson, M G; Albert, J; Chen, E; Dubois-Felsmann, G P; Dvoretskii, A; Hitlin, D G; Narsky, I; Porter, F C; Ryd, A; Samuel, A; Yang, S; Jayatilleke, S; Mancinelli, G; Meadows, B T; Sokoloff, M D; Abe, T; Blanc, F; Bloom, P; Chen, S; Clark, P J; Ford, W T; Nauenberg, U; Olivas, A; Rankin, P; Roy, J; Smith, J G; Van Hoek, W C; Zhang, L; Harton, J L; Hu, T; Soffer, A; Toki, W H; Wilson, R J; Zhang, J; Altenburg, D; Brandt, T; Brose, J; Colberg, T; Dickopp, M; Dubitzky, R S; Hauke, A; Lacker, H M; Maly, E; Müller-Pfefferkorn, R; Nogowski, R; Otto, S; Schubert, J; Schubert, K R; Schwierz, R; Spaan, B; Wilden, L; Bernard, D; Bonneaud, G R; Brochard, F; Cohen-Tanugi, J; Grenier, P; Thiebaux, Ch; Vasileiadis, G; Verderi, M; Khan, A; Lavin, D; Muheim, F; Playfer, S; Swain, J E; Andreotti, M; Azzolini, V; Bettoni, D; Bozzi, C; Calabrese, R; Cibinetto, G; Luppi, E; Negrini, M; Piemontese, L; Sarti, A; Treadwell, E; Anulli, F; Baldini-Ferroli, R; Biasini, M; Calcaterra, A; De Sangro, R; Falciai, D; Finocchiaro, G; Patteri, P; Peruzzi, I M; Piccolo, M; Pioppi, M; Zallo, A; Buzzo, A; Capra, R; Contri, R; Crosetti, G; Lo Vetere, M; Macri, M; Monge, M R; Passaggio, S; Patrignani, C; Robutti, E; Santroni, A; Tosi, S; Bailey, S; Morii, M; Won, E; Bhimji, W; Bowerman, D A; Dauncey, P D; Egede, U; Eschrich, I; Gaillard, J R; Morton, G W; Nash, J A; Sanders, P; Taylor, G P; Grenier, G J; Lee, S-J; Mallik, U; Cochran, J; Crawley, H B; Lamsa, J; Meyer, W T; Prell, S; Rosenberg, E I; Yi, J; Davier, M; Grosdidier, G; Höcker, A; Laplace, S; Le Diberder, F; Lepeltier, V; Lutz, A M; Petersen, T C; Plaszczynski, S; Schune, M H; Tantot, L; Wormser, G; Brigljević, V; Cheng, C H; Lange, D J; Wright, D M; Bevan, A J; Coleman, J P; Fry, J R; Gabathuler, E; Gamet, R; Kay, M; Parry, R J; Payne, D J; Sloane, R J; Touramanis, C; Back, J J; Harrison, P F; Shorthouse, H W; Strother, P; Vidal, P B; Brown, C L; Cowan, G; Flack, R L; Flaecher, H U; George, S; Green, M G; Kurup, A; Marker, C E; McMahon, T R; Ricciardi, S; Salvatore, F; Vaitsas, G; Winter, M A; Brown, D; Davis, C L; Allison, J; Barlow, R J; Forti, A C; Hart, P A; Hodgkinson, M C; Jackson, F; Lafferty, G D; Lyon, A J; Weatherall, J H; Williams, J C; Farbin, A; Jawahery, A; Kovalskyi, D; Lae, C K; Lillard, V; Roberts, D A; Blaylock, G; Dallapiccola, C; Flood, K T; Hertzbach, S S; Kofler, R; Koptchev, V B; Moore, T B; Saremi, S; Staengle, H; Willocq, S; Cowan, R; Sciolla, G; Taylor, F; Yamamoto, R K; Mangeol, D J J; Patel, P M; Lazzaro, A; Palombo, F; Bauer, J M; Cremaldi, L; Eschenburg, V; Godang, R; Kroeger, R; Reidy, J; Sanders, D A; Summers, D J; Zhao, H W; Brunet, S; Cote-Ahern, D; Hast, C; Taras, P; Nicholson, H; Cartaro, C; Cavallo, N; De Nardo, G; Fabozzi, F; Gatto, C; Lista, L; Paolucci, P; Piccolo, D; Sciacca, C; Baak, M A; Raven, G; LoSecco, J M; Gabriel, T A; Brau, B; Gan, K K; Honscheid, K; Hufnagel, D; Kagan, H; Kass, R; Pulliam, T; Wong, Q K; Brau, J; Frey, R; Potter, C T; Sinev, N B; Strom, D; Torrence, E; Colecchia, F; Dorigo, A; Galeazzi, F; Margoni, M; Morandin, M; Posocco, M; Rotondo, M; Simonetto, F; Stroili, R; Tiozzo, G; Voci, C; Benayoun, M; Briand, H; Chauveau, J; David, P; De La Vaissière, Ch; Del Buono, L; Hamon, O; John, M J J; Leruste, Ph; Ocariz, J; Pivk, M; Roos, L; Stark, J; T'Jampens, S; Therin, G; Manfredi, P F; Re, V; Behera, P K; Gladney, L; Guo, Q H; Panetta, J; Angelini, C; Batignani, G; Bettarini, S; Bondioli, M; Bucci, F; Calderini, G; Carpinelli, M; Del Gamba, V; Forti, F; Giorgi, M A; Lusiani, A; Marchiori, G; Martinez-Vidal, F; Morganti, M; Neri, N; Paoloni, E; Rama, M; Rizzo, G; Sandrelli, F; Walsh, J; Haire, M; Judd, D; Paick, K; Wagoner, D E; Danielson, N; Elmer, P; Lu, C; Miftakov, V; Olsen, J; Smith, A J S; Tanaka, H A; Varnes, E W; Bellini, F; Cavoto, G; Faccini, R; Ferrarotto, F; Ferroni, F; Gaspero, M; Mazzoni, M A; Morganti, S; Pierini, M; Piredda, G; Safai Tehrani, F; Voena, C; Christ, S; Wagner, G; Waldi, R; Adye, T; De Groot, N; Franek, B; Geddes, N I; Gopal, G P; Olaiya, E O; Xella, S M; Aleksan, R; Emery, S; Gaidot, A; Ganzhur, S F; Giraud, P-F; Hamel de Monchenault, G; Kozanecki, W; Langer, M; Legendre, M; London, G W; Mayer, B; Schott, G; Vasseur, G; Yeche, Ch; Zito, M; Purohit, M V; Weidemann, A W; Yumiceva, F X; Aston, D; Bartoldus, R; Berger, N; Boyarski, A M; Buchmueller, O L; Convery, M R; Coupal, D P; Dong, D; Dorfan, J; Dujmic, D; Dunwoodie, W; Field, R C; Glanzman, T; Gowdy, S J; Grauges-Pous, E; Hadig, T; Halyo, V; Hryn'ova, T; Innes, W R; Jessop, C P; Kelsey, M H; Kim, P; Kocian, M L; Langenegger, U; Leith, D W G S; Luitz, S; Luth, V; Lynch, H L; Marsiske, H; Messner, R; Muller, D R; O'Grady, C P; Ozcan, V E; Perazzo, A; Perl, M; Petrak, S; Ratcliff, B N; Robertson, S H; Roodman, A; Salnikov, A A; Schindler, R H; Schwiening, J; Simi, G; Snyder, A; Soha, A; Stelzer, J; Su, D; Sullivan, M K; Va'vra, J; Wagner, S R; Weaver, M; Weinstein, A J R; Wisniewski, W J; Wright, D H; Young, C C; Burchat, P R; Edwards, A J; Meyer, T I; Petersen, B A; Roat, C; Ahmed, S; Alam, M S; Ernst, J A; Saleem, M; Wappler, F R; Bugg, W; Krishnamurthy, M; Spanier, S M; Eckmann, R; Kim, H; Ritchie, J L; Schwitters, R F; Izen, J M; Kitayama, I; Lou, X C; Ye, S; Bianchi, F; Bona, M; Gallo, F; Gamba, D; Borean, C; Bosisio, L; Della Ricca, G; Dittongo, S; Grancagnolo, S; Lanceri, L; Poropat, P; Vitale, L; Vuagnin, G; Panvini, R S; Banerjee, Sw; Brown, C M; Fortin, D; Jackson, P D; Kowalewski, R; Roney, J M; Band, H R; Dasu, S; Datta, M; Eichenbaum, A M; Johnson, J R; Kutter, P E; Li, H; Liu, R; Di Lodovico, F; Mihalyi, A; Mohapatra, A K; Pan, Y; Prepost, R; Sekula, S J; von Wimmersperg-Toeller, J H; Wu, J; Wu, S L; Yu, Z; Neal, H

    2003-12-12

    We present a study of the decay B0-->pi(0)pi(0) based on a sample of 124 x 10(6) BB pairs recorded by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We observe 46+/-13+/-3 events, where the first error is statistical and the second is systematic, corresponding to a significance of 4.2 standard deviations including systematic uncertainties. We measure the branching fraction B(B0-->pi(0)pi(0))=(2.1+/-0.6+/-0.3)x10(-6), averaged over B0 and B(0) decays.

  17. Observation of a Significant Excess of π0π0 Events in B Meson Decays

    NASA Astrophysics Data System (ADS)

    Aubert, B.; Barate, R.; Boutigny, D.; Gaillard, J.-M.; Hicheur, A.; Karyotakis, Y.; Lees, J. P.; Robbe, P.; Tisserand, V.; Zghiche, A.; Palano, A.; Pompili, A.; Chen, J. C.; Qi, N. D.; Rong, G.; Wang, P.; Zhu, Y. S.; Eigen, G.; Ofte, I.; Stugu, B.; Abrams, G. S.; Borgland, A. W.; Breon, A. B.; Brown, D. N.; Button-Shafer, J.; Cahn, R. N.; Charles, E.; Day, C. T.; Gill, M. S.; Gritsan, A. V.; Groysman, Y.; Jacobsen, R. G.; Kadel, R. W.; Kadyk, J.; Kerth, L. T.; Kolomensky, Yu. G.; Kral, J. F.; Kukartsev, G.; Leclerc, C.; Levi, M. E.; Lynch, G.; Mir, L. M.; Oddone, P. J.; Orimoto, T. J.; Pripstein, M.; Roe, N. A.; Romosan, A.; Ronan, M. T.; Shelkov, V. G.; Telnov, A. V.; Wenzel, W. A.; Ford, K.; Harrison, T. J.; Hawkes, C. M.; Knowles, D. J.; Morgan, S. E.; Penny, R. C.; Watson, A. T.; Watson, N. K.; Goetzen, K.; Held, T.; Koch, H.; Lewandowski, B.; Pelizaeus, M.; Peters, K.; Schmuecker, H.; Steinke, M.; Barlow, N. R.; Boyd, J. T.; Chevalier, N.; Cottingham, W. N.; Kelly, M. P.; Latham, T. E.; Mackay, C.; Wilson, F. F.; Abe, K.; Cuhadar-Donszelmann, T.; Hearty, C.; Mattison, T. S.; McKenna, J. A.; Thiessen, D.; Kyberd, P.; McKemey, A. K.; Blinov, V. E.; Bukin, A. D.; Golubev, V. B.; Ivanchenko, V. N.; Kravchenko, E. A.; Onuchin, A. P.; Serednyakov, S. I.; Skovpen, Yu. I.; Solodov, E. P.; Yushkov, A. N.; Best, D.; Bruinsma, M.; Chao, M.; Kirkby, D.; Lankford, A. J.; Mandelkern, M.; Mommsen, R. K.; Roethel, W.; Stoker, D. P.; Buchanan, C.; Hartfiel, B. L.; Shen, B. C.; del Re, D.; Hadavand, H. K.; Hill, E. J.; Macfarlane, D. B.; Paar, H. P.; Rahatlou, Sh.; Sharma, V.; Berryhill, J. W.; Campagnari, C.; Dahmes, B.; Kuznetsova, N.; Levy, S. L.; Long, O.; Lu, A.; Mazur, M. A.; Richman, J. D.; Verkerke, W.; Beck, T. W.; Beringer, J.; Eisner, A. M.; Heusch, C. A.; Lockman, W. S.; Schalk, T.; Schmitz, R. E.; Schumm, B. A.; Seiden, A.; Turri, M.; Walkowiak, W.; Williams, D. C.; Wilson, M. G.; Albert, J.; Chen, E.; Dubois-Felsmann, G. P.; Dvoretskii, A.; Hitlin, D. G.; Narsky, I.; Porter, F. C.; Ryd, A.; Samuel, A.; Yang, S.; Jayatilleke, S.; Mancinelli, G.; Meadows, B. T.; Sokoloff, M. D.; Abe, T.; Blanc, F.; Bloom, P.; Chen, S.; Clark, P. J.; Ford, W. T.; Nauenberg, U.; Olivas, A.; Rankin, P.; Roy, J.; Smith, J. G.; van Hoek, W. C.; Zhang, L.; Harton, J. L.; Hu, T.; Soffer, A.; Toki, W. H.; Wilson, R. J.; Zhang, J.; Altenburg, D.; Brandt, T.; Brose, J.; Colberg, T.; Dickopp, M.; Dubitzky, R. S.; Hauke, A.; Lacker, H. M.; Maly, E.; Müller-Pfefferkorn, R.; Nogowski, R.; Otto, S.; Schubert, J.; Schubert, K. R.; Schwierz, R.; Spaan, B.; Wilden, L.; Bernard, D.; Bonneaud, G. R.; Brochard, F.; Cohen-Tanugi, J.; Grenier, P.; Thiebaux, Ch.; Vasileiadis, G.; Verderi, M.; Khan, A.; Lavin, D.; Muheim, F.; Playfer, S.; Swain, J. E.; Andreotti, M.; Azzolini, V.; Bettoni, D.; Bozzi, C.; Calabrese, R.; Cibinetto, G.; Luppi, E.; Negrini, M.; Piemontese, L.; Sarti, A.; Treadwell, E.; Anulli, F.; Baldini-Ferroli, R.; Biasini, M.; Calcaterra, A.; de Sangro, R.; Falciai, D.; Finocchiaro, G.; Patteri, P.; Peruzzi, I. M.; Piccolo, M.; Pioppi, M.; Zallo, A.; Buzzo, A.; Capra, R.; Contri, R.; Crosetti, G.; Vetere, M. Lo; Macri, M.; Monge, M. R.; Passaggio, S.; Patrignani, C.; Robutti, E.; Santroni, A.; Tosi, S.; Bailey, S.; Morii, M.; Won, E.; Bhimji, W.; Bowerman, D. A.; Dauncey, P. D.; Egede, U.; Eschrich, I.; Gaillard, J. R.; Morton, G. W.; Nash, J. A.; Sanders, P.; Taylor, G. P.; Grenier, G. J.; Lee, S.-J.; Mallik, U.; Cochran, J.; Crawley, H. B.; Lamsa, J.; Meyer, W. T.; Prell, S.; Rosenberg, E. I.; Yi, J.; Davier, M.; Grosdidier, G.; Höcker, A.; Laplace, S.; Le Diberder, F.; Lepeltier, V.; Lutz, A. M.; Petersen, T. C.; Plaszczynski, S.; Schune, M. H.; Tantot, L.; Wormser, G.; Brigljević, V.; Cheng, C. H.; Lange, D. J.; Wright, D. M.; Bevan, A. J.; Coleman, J. P.; Fry, J. R.; Gabathuler, E.; Gamet, R.; Kay, M.; Parry, R. J.; Payne, D. J.; Sloane, R. J.; Touramanis, C.; Back, J. J.; Harrison, P. F.; Shorthouse, H. W.; Strother, P.; Vidal, P. B.; Brown, C. L.; Cowan, G.; Flack, R. L.; Flaecher, H. U.; George, S.; Green, M. G.; Kurup, A.; Marker, C. E.; McMahon, T. R.; Ricciardi, S.; Salvatore, F.; Vaitsas, G.; Winter, M. A.; Brown, D.; Davis, C. L.; Allison, J.; Barlow, R. J.; Forti, A. C.; Hart, P. A.; Hodgkinson, M. C.; Jackson, F.; Lafferty, G. D.; Lyon, A. J.; Weatherall, J. H.; Williams, J. C.; Farbin, A.; Jawahery, A.; Kovalskyi, D.; Lae, C. K.; Lillard, V.; Roberts, D. A.; Blaylock, G.; Dallapiccola, C.; Flood, K. T.; Hertzbach, S. S.; Kofler, R.; Koptchev, V. B.; Moore, T. B.; Saremi, S.; Staengle, H.; Willocq, S.; Cowan, R.; Sciolla, G.; Taylor, F.; Yamamoto, R. K.; Mangeol, D. J.; Patel, P. M.; Lazzaro, A.; Palombo, F.; Bauer, J. M.; Cremaldi, L.; Eschenburg, V.; Godang, R.; Kroeger, R.; Reidy, J.; Sanders, D. A.; Summers, D. J.; Zhao, H. W.; Brunet, S.; Cote-Ahern, D.; Hast, C.; Taras, P.; Nicholson, H.; Cartaro, C.; Cavallo, N.; de Nardo, G.; Fabozzi, F.; Gatto, C.; Lista, L.; Paolucci, P.; Piccolo, D.; Sciacca, C.; Baak, M. A.; Raven, G.; Losecco, J. M.; Gabriel, T. A.; Brau, B.; Gan, K. K.; Honscheid, K.; Hufnagel, D.; Kagan, H.; Kass, R.; Pulliam, T.; Wong, Q. K.; Brau, J.; Frey, R.; Potter, C. T.; Sinev, N. B.; Strom, D.; Torrence, E.; Colecchia, F.; Dorigo, A.; Galeazzi, F.; Margoni, M.; Morandin, M.; Posocco, M.; Rotondo, M.; Simonetto, F.; Stroili, R.; Tiozzo, G.; Voci, C.; Benayoun, M.; Briand, H.; Chauveau, J.; David, P.; de La Vaissière, Ch.; del Buono, L.; Hamon, O.; John, M. J.; Leruste, Ph.; Ocariz, J.; Pivk, M.; Roos, L.; Stark, J.; T'jampens, S.; Therin, G.; Manfredi, P. F.; Re, V.; Behera, P. K.; Gladney, L.; Guo, Q. H.; Panetta, J.; Angelini, C.; Batignani, G.; Bettarini, S.; Bondioli, M.; Bucci, F.; Calderini, G.; Carpinelli, M.; del Gamba, V.; Forti, F.; Giorgi, M. A.; Lusiani, A.; Marchiori, G.; Martinez-Vidal, F.; Morganti, M.; Neri, N.; Paoloni, E.; Rama, M.; Rizzo, G.; Sandrelli, F.; Walsh, J.; Haire, M.; Judd, D.; Paick, K.; Wagoner, D. E.; Danielson, N.; Elmer, P.; Lu, C.; Miftakov, V.; Olsen, J.; Smith, A. J.; Tanaka, H. A.; Varnes, E. W.; Bellini, F.; Cavoto, G.; Faccini, R.; Ferrarotto, F.; Ferroni, F.; Gaspero, M.; Mazzoni, M. A.; Morganti, S.; Pierini, M.; Piredda, G.; Tehrani, F. Safai; Voena, C.; Christ, S.; Wagner, G.; Waldi, R.; Adye, T.; de Groot, N.; Franek, B.; Geddes, N. I.; Gopal, G. P.; Olaiya, E. O.; Xella, S. M.; Aleksan, R.; Emery, S.; Gaidot, A.; Ganzhur, S. F.; Giraud, P.-F.; de Monchenault, G. Hamel; Kozanecki, W.; Langer, M.; Legendre, M.; London, G. W.; Mayer, B.; Schott, G.; Vasseur, G.; Yeche, Ch.; Zito, M.; Purohit, M. V.; Weidemann, A. W.; Yumiceva, F. X.; Aston, D.; Bartoldus, R.; Berger, N.; Boyarski, A. M.; Buchmueller, O. L.; Convery, M. R.; Coupal, D. P.; Dong, D.; Dorfan, J.; Dujmic, D.; Dunwoodie, W.; Field, R. C.; Glanzman, T.; Gowdy, S. J.; Grauges-Pous, E.; Hadig, T.; Halyo, V.; Hryn'ova, T.; Innes, W. R.; Jessop, C. P.; Kelsey, M. H.; Kim, P.; Kocian, M. L.; Langenegger, U.; Leith, D. W.; Luitz, S.; Luth, V.; Lynch, H. L.; Marsiske, H.; Messner, R.; Muller, D. R.; O'Grady, C. P.; Ozcan, V. E.; Perazzo, A.; Perl, M.; Petrak, S.; Ratcliff, B. N.; Robertson, S. H.; Roodman, A.; Salnikov, A. A.; Schindler, R. H.; Schwiening, J.; Simi, G.; Snyder, A.; Soha, A.; Stelzer, J.; Su, D.; Sullivan, M. K.; Va'Vra, J.; Wagner, S. R.; Weaver, M.; Weinstein, A. J.; Wisniewski, W. J.; Wright, D. H.; Young, C. C.; Burchat, P. R.; Edwards, A. J.; Meyer, T. I.; Petersen, B. A.; Roat, C.; Ahmed, S.; Alam, M. S.; Ernst, J. A.; Saleem, M.; Wappler, F. R.; Bugg, W.; Krishnamurthy, M.; Spanier, S. M.; Eckmann, R.; Kim, H.; Ritchie, J. L.; Schwitters, R. F.; Izen, J. M.; Kitayama, I.; Lou, X. C.; Ye, S.; Bianchi, F.; Bona, M.; Gallo, F.; Gamba, D.; Borean, C.; Bosisio, L.; Della Ricca, G.; Dittongo, S.; Grancagnolo, S.; Lanceri, L.; Poropat, P.; Vitale, L.; Vuagnin, G.; Panvini, R. S.; Banerjee, Sw.; Brown, C. M.; Fortin, D.; Jackson, P. D.; Kowalewski, R.; Roney, J. M.; Band, H. R.; Dasu, S.; Datta, M.; Eichenbaum, A. M.; Johnson, J. R.; Kutter, P. E.; Li, H.; Liu, R.; di Lodovico, F.; Mihalyi, A.; Mohapatra, A. K.; Pan, Y.; Prepost, R.; Sekula, S. J.; von Wimmersperg-Toeller, J. H.; Wu, J.; Wu, S. L.; Yu, Z.; Neal, H.

    2003-12-01

    We present a study of the decay B0→π0π0 based on a sample of 124×106 BB¯ pairs recorded by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. We observe 46±13±3 events, where the first error is statistical and the second is systematic, corresponding to a significance of 4.2 standard deviations including systematic uncertainties. We measure the branching fraction B(B0→π0π0)=(2.1±0.6±0.3)×10-6, averaged over B0 and B¯0 decays.

  18. Long period (LP) events on Mt Etna volcano (Italy): the influence of velocity structures on moment tensor inversion

    NASA Astrophysics Data System (ADS)

    Trovato, C.; Lokmer, I.; De Martin, F.; Aochi, H.

    2016-11-01

    Since a few decades volcanic long period (LP) events have been recorded on many active volcanoes and their study has been recognized as an important tool to characterize volcanic activity. LP event analyses through moment tensor (MT) inversions have led to kinematic descriptions of various source mechanisms. The main challenge in these inversions is to `strip out' the propagation effect in order to isolate the source; hence the velocity model used controls the accuracy of the retrieved source mechanism. We first carry out several synthetic tests of inversions on Mt Etna volcano (Italy). Four geological models with topography are considered with increasing complexity: the most complex model is used to generate synthetic data, while the other three models are used to calculate the Green's functions for inversions. The retrieved solutions from the three velocity models are similar. The MT solutions for a deeper source are well retrieved, while a shallower source test suffers from high uncertainties and strong misinterpretation of the source orientation. The homogeneous model gives the lowest misfit value, but source location and mechanism decomposition are inaccurate. When a complex model different from the true one is used, a high misfit value and a wrong solution is obtained. We then incorporate our findings into the MT inversion of an LP event recorded on Mt Etna in 2008. We obtain very different solutions among the three models in terms of source location and mechanism decomposition. The overall shape of the retrieved source time functions are similar, but some amplitude differences arise, especially for the homogeneous model. Our work highlights the importance of including the unconsolidated surface materials in the computation of Green's functions especially when dealing with shallow sources.

  19. Observations of rapid-fire event tremor at Lascar volcano, Chile

    USGS Publications Warehouse

    Asch, Guenter; Wylegalla, K.; Hellweg, M.; Seidl, D.; Rademacher, H.

    1996-01-01

    During the Proyecto de Investigacio??n Sismolo??gica de la Cordillera Occidental (PISCO '94) in the Atacama desert of Northern Chile, a continuously recording broadband seismic station was installed to the NW of the currently active volcano, Lascar. For the month of April, 1994, an additional network of three, short period, three-component stations was deployed around the volcano to help discriminate its seismic signals from other local seismicity. During the deployment, the volcanic activity at Lascar appeared to be limited mainly to the emission of steam and SO2. Tremor from Lascar is a random, ??rapid-fire?? series of events with a wide range of amplitudes and a quasi-fractal structure. The tremor is generated by an ensemble of independent elementary sources clustered in the volcanic edifice. In the short-term, the excitation of the sources fluctuates strongly, while the long-term power spectrum is very stationary.

  20. Iodine observed in new particle formation events in the Arctic atmosphere during ACCACIA

    NASA Astrophysics Data System (ADS)

    Allan, J. D.; Williams, P. I.; Najera, J.; Whitehead, J. D.; Flynn, M. J.; Taylor, J. W.; Liu, D.; Darbyshire, E.; Carpenter, L. J.; Chance, R.; Andrews, S. J.; Hackenberg, S. C.; McFiggans, G.

    2015-05-01

    Accurately accounting for new particle formation (NPF) is crucial to our ability to predict aerosol number concentrations in many environments and thus cloud properties, which is in turn vital in simulating radiative transfer and climate. Here we present an analysis of NPF events observed in the Greenland Sea during the summertime as part of the Aerosol-Cloud Coupling And Climate Interactions in the Arctic (ACCACIA) project. While NPF events have been reported in the Arctic before, we were able, for the first time, to detect iodine in the growing particles using an Aerosol Mass Spectrometer (AMS) during a persistent event in the region of the coastal sea-ice near Greenland. Given the potency of iodine as a nucleation precursor, the results imply that iodine was responsible for the initial NPF, a phenomenon that has been reported at lower latitudes and associated with molecular iodine emissions from coastal macroalgae. The initial source of iodine in this instance is not clear, but it was associated with air originating approximately 1 day previously over melting coastal sea-ice. These results show that atmospheric models must consider iodine as a source of new particles in addition to established precursors such as sulfur compounds.

  1. Study of reconnection events through Global MHD simulation and observational data

    NASA Astrophysics Data System (ADS)

    Cardoso, F. R.; Gonzalez, W. D.; Sibeck, D. G.; Kuznetsova, M. M.; Alves, M. V.

    2011-12-01

    Magnetic reconnection is the dominant mechanism for solar wind energy and momentum transfer to the magnetosphere. It can be a continuous or a transient process. Time-varying reconnection produces flux transfer events (FTEs) which can be identified by bipolar signatures in the component of the magnetic field normal to the magnetopause, deflections in the component tangential, and variations in the magnetic field magnitude. Some events exhibit the mixed magnetospheric and magnetosheath plasma populations expected for reconnection. Global magnetohydrodynamics (MHD) simulations are important tools to understand the relevant magnetic reconnection mechanisms. We have identified magnetic reconnection events, especially FTEs, in global MHD simulations and observations. We study their spatial and temporal characteristics as a function of solar wind parameters, in particular the interplanetary magnetic field orientation. We determine the origin of FTEs as well as the properties that describe them such as their dimension, extent and motion as a function of time. In particular, we track the motion of FTEs in an attempt to determine their point of origin, their destination, and how fast they move.

  2. Characteristics of Electron Distributions Observed During Large Amplitude Whistler Wave Events in the Magnetosphere

    NASA Technical Reports Server (NTRS)

    Wilson, Lynn B., III

    2010-01-01

    We present a statistical study of the characteristics of electron distributions associated with large amplitude whistler waves inside the terrestrial magnetosphere using waveform capture data as an addition of the study by Kellogg et al., [2010b]. We identified three types of electron distributions observed simultaneously with the whistler waves including beam-like, beam/flattop, and anisotropic distributions. The whistlers exhibited different characteristics dependent upon the observed electron distributions. The majority of the waveforms observed in our study have f/fce < or = 0.5 and are observed primarily in the radiation belts outside the plasmapause simultaneously with anisotropic electron distributions. We also present an example waveform capture of the largest magnetic field amplitude (> or = 8 nT pk-pk) whistler wave measured in the radiation belts. The majority of the largest amplitude whistlers occur during magnetically active periods (AE > 200 nT).

  3. Management of Toxoplasmic Retinochoroiditis during Pregnancy, Postpartum Period and Lactation: Clinical Observations

    PubMed Central

    Brydak-Godowska, Joanna; Moneta-Wielgoś, Joanna; Kęcik, Dariusz; Borkowski, Piotr Karol

    2015-01-01

    Background During pregnancy and labor, the immune response is physiologically impaired and women are more susceptible to infections. Since many drugs may have potentially adverse effects on the fetus and newborn, less aggressive treatment regimens should be considered in pregnant and lactating patients. The aim of our study was to present the management of toxoplasmic retinochoroiditis during pregnancy, postpartum period, and lactation. Material/Methods A retrospective study was undertaken of the clinical records of 24 women during pregnancy, postpartum period, and lactation who were referred in the years 1994–2014 to the Department of Zoonoses and Tropical Diseases or the Department of Ophthalmology, Medical University of Warsaw for toxoplasmic retinochoroiditis. The diagnosis was based on the typical ophthalmoscopic picture, confirmed by serological testing using an ELISA method. Results A total of 28 attacks of toxoplasmic retinochoroiditis were observed in 24 patients during pregnancy, postpartum period, and lactation. The choice of treatment was guided by the character and location of the inflammatory lesion and the gestational age. Topical (steroidal/nonsteroidal eye drops) and systemic treatments with spiramycin or azithromycin, Fansidar (pyrimethamine 25 mg/sulfadoxine 500 mg), and prednisone were used. Conclusions Management of toxoplasmic retinochoroiditis during pregnancy, postpartum period, or lactation must be individualized and guided by the gestational age and location of the active lesion. Women of childbearing age with toxoplasma ocular lesions should be informed by their doctors about possible active recurrences during pregnancy and followed carefully by an ophthalmologist when pregnant. PMID:25711713

  4. Confrontation Between a Quantized Periods of Some Exo-planetary Systems and Observations

    NASA Astrophysics Data System (ADS)

    El Fady Morcos, Abd

    2012-07-01

    Confrontation Between a Quantized Periods of Some Exo-planetary Systems and Observations A.B. Morcos Corot and Kepler were designed to detect Earth-like extra solar planets. The orbital elements and periods of these planets will contain some uncertainties. Many theoretical treatments depend on the idea of quantization were done aiming to find orbital elements of these exoplenets. In the present work, as an extension of previous works, the periods of some extoplanetary systems are calculated by using a simple derived formula. The orbital velocities of some of them are predicted . A comparison between the calculated and observed data is done References 1-J.M. Barnothy , the stability of the Solar System and of small Stellar Systems . (Y.Kazai edn,IAU,1974). 2-L.Nottale,Fractal Space-Time and Microphysics,Towards a Theory of Scale Relativity,( World Scientific, London,1994). 3-L. Nottale, A&A Lett. 315, L9 (1996). 4-L. Nottale, G. Schumacher and J. Gay, A&A , 322, 1018 , (1997). 5-L. Nottale, A&A , 361, 379 (2000). 6-A.G. Agnese and R.Festa, arXiv:astro-ph/9807186v1, (1998). 7-A.G. Agnese and R.Festa, arXiv:astro-ph/9910534v2. (1999). 8- A.B.Morcos, MG 12 , France (2009). 9- A.B.Morcs, Cospar 38 , Bremen , Germany (2010)

  5. HST Observations of a Large-Amplitude, Long-Period Trojan: (11351) Leucus

    NASA Astrophysics Data System (ADS)

    Noll, Keith S.; Levison, Harold F.; Buie, Marc W.; Grundy, William M.

    2016-10-01

    (11351) Leucus (1997 TS25) is a Trojan that is notable for having one of the longest known rotation periods of any small body, T=514 h. A possible cause for this long period would be the existence of a tidally locked binary similar to the already-known long period binary Trojan, (617) Patroclus. If this were the case, the system would become tidally circularized in a time short compared to the age of the solar system. In such a case, the components would be separated by ~0.18 arcsec at lightcurve maximum, resolvable by WFC3. We carried out observations in June 2016, coordinated with groundbased observations to schedule near a maximum to test whether (11351) Leucus is binary. We describe the results of these observations.Observations of (11351) Leucus are of particular interest because it is a target of the Lucy mission, a Discovery mission currently in phase A and one of five that may be selected in early 2017. Searches for binary Trojans also offer multiple scientific benefits independent of mission status. Orbit-derived mass and density can be used to constrain planetary migration models. Low density is characteristic of bodies found in the dynamically cold Kuiper Belt, a remnant of the solar system's protoplanetary disk. Only one undisputed density has been measured in the Trojans, that of the binary (617) Patroclus, which has a low density of 0.8 g/cm3, similar to the low densities found in the Kuiper Belt. Slow rotators offer a set of targets that are tidally evolved systems and therefore are among the most attractive potential targets for an HST search.

  6. Explosive events in active region observed by IRIS and SST/CRISP

    NASA Astrophysics Data System (ADS)

    Huang, Z.; Madjarska, M. S.; Scullion, E. M.; Xia, L.-D.; Doyle, J. G.; Ray, T.

    2017-01-01

    Transition-region explosive events (EEs) are characterized by non-Gaussian line profiles with enhanced wings at Doppler velocities of 50-150 km s-1. They are believed to be the signature of solar phenomena that are one of the main contributors to coronal heating. The aim of this study is to investigate the link of EEs to dynamic phenomena in the transition region and chromosphere in an active region. We analyse observations simultaneously taken by the Interface Region Imaging Spectrograph (IRIS) in the Si IV 1394 Å line and the slit-jaw (SJ) 1400 Å images, and the Swedish 1-m Solar Telescope in the Hα line. In total 24 events were found. They are associated with small-scale loop brightenings in SJ 1400 Å images. Only four events show a counterpart in the Hα-35 km s-1 and Hα+35 km s-1 images. Two of them represent brightenings in the conjunction region of several loops that are also related to a bright region (granular lane) in the Hα-35 km s-1 and Hα+35 km s-1 images. 16 are general loop brightenings that do not show any discernible response in the Hα images. Six EEs appear as propagating loop brightenings, from which two are associated with dark jet-like features clearly seen in the Hα-35 km s-1 images. We found that chromospheric events with jet-like appearance seen in the wings of the Hα line can trigger EEs in the transition region and in this case the IRIS Si IV 1394 Å line profiles are seeded with absorption components resulting from Fe II and Ni II. Our study indicates that EEs occurring in active regions have mostly upper-chromosphere/transition-region origin. We suggest that magnetic reconnection resulting from the braidings of small-scale transition region loops is one of the possible mechanisms of energy release that are responsible for the EEs reported in this paper.

  7. Effects of amines on particle growth observed in new particle formation events

    NASA Astrophysics Data System (ADS)

    Tao, Ye; Ye, Xingnan; Jiang, Shuqing; Yang, Xin; Chen, Jianmin; Xie, Yuanyuan; Wang, Ruyu

    2016-01-01

    Particle size distributions in the range of 0.01-10 µm were measured in urban Shanghai in the summer of 2013 using a Wide-range Particle Spectrometer (WPS). Size-segregated aerosol samples were collected concurrently using a Micro-Orifice Uniform Deposit Impactor (MOUDI), which aided our in-depth understanding of the new particle formation (NPF) mechanism in the polluted Yangtze River Delta area. During the observations, 16 NPF events occurred at high temperatures (~34.7°C) on clear and sunny days. In the ammonium-poor PM1.0 (particulate matter less than 1.0 µm), sulfate and ammonium accounted for 92% of the total water-soluble inorganic species. Six aminiums were detected in these MOUDI samples, among which the group of diethylaminium and trimethylaminium (DEAH+ + TMAH+) was the most abundant. The very high level of aminiums (average concentration up to 86.4 ng m-3 in PM1.8), together with highly acidic aerosols, provided insight into the frequent NPF events. The high mass ratio of total aminiums to NH4+ (>0.2 for PM0.056) further highlighted the important role of amines in promoting NPF. The concentration of DEAH+ + TMAH+ in new particles below 180 nm was strongly correlated with aerosol phase acidity, indicating that acid-base reactions dominated the aminium formation in NPF events. The unexpected enhancement of DEAH+ + TMAH+ on a nonevent day was attributed to the transportation of an SO2 plume. Our results reveal that the heterogeneous uptake of amines is dominated by the acid-base reaction mechanism, which can effectively contribute to particle growth in NPF events.

  8. Seasonal and Interannual Variability of Short Period Lamb Waves Observed over South Pole

    NASA Astrophysics Data System (ADS)

    Palo, S.; Gerhardt, D.

    2009-12-01

    A meteor radar system was installed at Amundsen-Scott South Pole station in 2001 and became fully operational in 2002. This radar has operated nearly continuously since and is providing horizontal wind measurements in four separate azimuth directions. This feature provides the ability to determine the zonal wavenumber and direction of propagation for the observed perturbations. With multiple years of observations we have the opportunity to investigate the coherent seasonal structure of the large scale observations over South Pole. These include the migrating diurnal and semidiurnal oscillations which are large during the summer months as well as both eastward and westward propagating planetary waves. Throughout the year short period (8-14) hour oscillations are present and have been associated with Lamb Waves. In this paper we present a spatial and temporal analysis of these planetary waves.

  9. Observing and Modeling Long-Period Tidal Variations in Polar Motion

    NASA Technical Reports Server (NTRS)

    Gross, Richard S.; Dickman, S. R.

    2011-01-01

    By exchanging angular momentum with the solid Earth, ocean tides cause the Earth's rotation to change. While hydrodynamic tide models have been used to study the effect of ocean tides on polar motion, it is shown here that none of the published models can fully account for the observed variations. An empirical ocean tide model is therefore determined by fitting periodic terms at the tidal frequencies to polar motion excitation observations, from which atmospheric and non-tidal oceanic effects were removed. While the empirical ocean tide model does fully account for allof the observed tidal power, tests indicate that the model may not have completely converged. So better models of the effects of ocean tides on polar motion are still needed, both dynamical and empirical.

  10. Quasi-periodic mid-Cretaceous Oceanic Anoxic Events linked by oscillations of the phosphorus and oxygen cycles

    NASA Astrophysics Data System (ADS)

    Lenton, T.; Handoh, I.

    2003-04-01

    A series of oceanic anoxic events (OAEs) occurred in the mid-Cretaceous warm period (120-80 Ma) that have been linked with high rates of organic carbon burial, warm high- and low- latitude temperatures and sea-level changes. OAEs have been studied individually, but a causal mechanism that connects them has been lacking. We show that peaks in phosphorus accumulation in marine sediments broadly coincide with OAEs 1a, 1b, 1d, 2 and 3, and exhibit a 5-6 Myr quasi-periodicity, which for reactive-P is prominent over 100-80 Ma. Oxic-anoxic oscillations of this frequency are also found in a model of the coupled N, P, C and O2 biogeochemical cycles. These are maintained by a positive feedback between phosphate concentration, biological productivity and anoxia and a counteracting, but slower, negative feedback between atmospheric oxygen and anoxia. A step increase in phosphorus weathering rate can shift the system into self-sustaining oscillation. This could have been caused by tectonic and volcanic forcing increasing atmospheric CO2 and global warmth 120-80 Ma, augmented by the rise of flowering plants circa 100 Ma. With a plausible forcing scenario, we are able to reproduce the approximate timing of OAEs 1a, 1b, 1d, 2 and 3 in the model.

  11. Periodic mid-Cretaceous oceanic anoxic events linked by oscillations of the phosphorus and oxygen biogeochemical cycles

    NASA Astrophysics Data System (ADS)

    Handoh, Itsuki C.; Lenton, Timothy M.

    2003-12-01

    A series of oceanic anoxic events (OAEs) occurred in the mid-Cretaceous warm period (120-80 Ma) that have been linked with high rates of organic carbon burial, warm high- and low- latitude temperatures, and sea-level changes. OAEs have been studied individually, but a causal mechanism that connects them has been lacking. We show that peaks in phosphorus accumulation in marine sediments broadly coincide with OAEs 1a, 1b, 1d, 2, and 3, and exhibit a 5-6 Myr periodicity, which for reactive-P is prominent over 100-80 Ma. Oxic-anoxic oscillations of this frequency are also found in a model of the coupled N, P, C, and O2 biogeochemical cycles. These oscillations are maintained by positive feedbacks between phosphate concentration, biological productivity, and anoxia in the global ocean and counteracting, but slower, negative feedbacks involving changes in atmospheric oxygen. An increase in phosphorus weathering rate above a critical threshold can shift the system into self-sustaining oscillation. This could have been caused by tectonic and volcanic forcing increasing atmospheric CO2 and global warmth 120-80 Ma, augmented by the rise of flowering plants around 100 Ma. With a plausible forcing scenario, we are able to reproduce the approximate timing of OAEs 1a, 1b, 1d, 2, and 3 in the model.

  12. Observations of 20-day period meridional current oscillations in the upper ocean along the Pacific Equator

    NASA Technical Reports Server (NTRS)

    Halpern, David; Knox, Robert A.; Luther, Douglas S.

    1988-01-01

    Prominent oscillations of the meridional current, with a mean period of approximately 20 days, is observed in the upper ocean from May 1979 to October 1985 using moored current measurements along the Pacific equator at 95, 110, 124, 140, and 152 deg W, as well as off (but near) the equator at 110 and 140 deg W. The fluctuations are relatively narrowband in frequency. A 95 percent statistically significant peak in the power spectra of the meridional current occurs at 110, 124, and 140 deg W, but not at 95 and 152 deg W where the spectral peaks are smaller. The dominant wave period decreases by about 4 percent from 110 to 140 deg W. The wave amplitude decreases with depth, and the wave is essentially confined to the upper 80 m. The penetration depth of the oscillation is greatest at 110 deg W and least at 140 deg W.

  13. SOHO/SWAN OBSERVATIONS OF SHORT-PERIOD SPACECRAFT TARGET COMETS

    SciTech Connect

    Combi, M. R.; Lee, Y.; Patel, T. S.; Maekinen, J. T. T.; Bertaux, J.-L.; Quemerais, E.

    2011-04-15

    SWAN, the Solar Wind ANisotropies all-sky hydrogen Ly{alpha} camera on the Solar and Heliospheric Observatory spacecraft that makes all-sky images of interplanetary neutral hydrogen, has an ongoing campaign to make special observations of comets, both short- and long-period ones, in addition to the serendipitous observations of comets as part of the all-sky monitoring program. We report here on a study of several short-period comets that were detected by SWAN: 21P/Giacobini-Zinner (1998 and 2005 apparitions), 19P/Borrelly (2001 apparition), 81P/Wild 2 (1997 apparition), and 103P/Hartley 2 (1997 apparition). SWAN observes comets over long continuous stretches of their visible apparitions and therefore provides excellent temporal coverage of the water production. For some of the observations we are also able to analyze an entire sequence of images over many days to several weeks/months using our time-resolved model and extract daily average water production rates over continuous periods of several days to months. The short-term (outburst) and long-term behavior can be correlated with other observations. The overall long-term variation is examined in light of seasonal effects seen in the pre- to post-perihelion differences. For 21P/Giacobini-Zinner and 81P/Wild 2 the activity variations over each apparition were more continuously monitored but nonetheless consistent with previous observations. For 19P/Borrelly we found a very steep variation of water production rates, again consistent with some previous observations, and a variation over six months around perihelion that was reasonably consistent with the spin-axis model of Schleicher et al. and the illumination of the main active areas. During the 1997-1998 apparition of 103P/Hartley 2, the target comet of the EPOXI mission (the Deep Impact extended mission), we found a variation with heliocentric distance ({approx}r{sup -3.6}) that was almost as steep as 19P/Borrelly and, given the small measured radius near

  14. Follow-Up Chandra Observations of Three Candidate Tidal Disruption Events

    NASA Astrophysics Data System (ADS)

    Halpern, J. P.; Gezari, S.; Komossa, S.

    2004-04-01

    Large-amplitude, high-luminosity soft X-ray flares were detected by the ROSAT All-Sky Survey in several galaxies with no evidence of Seyfert activity in their ground-based optical spectra. These flares had the properties predicted for a tidal disruption of a star by a central supermassive black hole. We report Chandra observations of three of these galaxies taken a decade after their flares that reveal weak nuclear X-ray sources that are from 240 to 6000 times fainter than their luminosities at peak, supporting the theory that these were special events and not ongoing active galactic nucleus (AGN) variability. The decline of RX J1624.9+7554 by a factor of 6000 is consistent with the (t-tD)-5/3 decay predicted for the fallback phase of a tidal disruption event, but only if ROSAT was lucky enough to catch the event exactly at its peak in 1990 October. RX J1242.6-1119A has declined by a factor of 240, also consistent with (t-tD)-5/3. In the H II galaxy NGC 5905 we find only resolved, soft X-ray emission that is undoubtedly associated with starburst activity. When accounting for the starburst component, the ROSAT observations of NGC 5905, as well as the Chandra upper limit on its nuclear flux, are consistent with a (t-tD)-5/3 decay by at least a factor of 1000. Although we found weak Seyfert 2 emission lines in Hubble Space Telescope spectra of NGC 5905, indicating that a low-luminosity AGN was present prior to the X-ray flare, we favor a tidal disruption explanation for the flare itself.

  15. Vacuum oscillations and excess of high energy solar neutrino events observed in Superkamiokande

    NASA Astrophysics Data System (ADS)

    Berezinsky, V.; Fiorentini, G.; Lissia, M.

    2000-01-01

    The excess of solar-neutrino events above 13 MeV that has been recently observed by Superkamiokande can be explained by the vacuum oscillation solution to the Solar Neutrino Problem (SNP). If the boron neutrino flux is 20% smaller than the standard solar model (SSM) prediction and the chlorine signal is assumed 30% (or 3.4σ) higher than the measured one, there exists a vacuum oscillation solution to SNP that reproduces both the observed spectrum of the recoil electrons, including the high energy distortion, and the other measured neutrino rates. The most distinct signature of this solution is a semi-annual seasonal variation of the 7Be neutrino flux with maximal amplitude. While the temporal series of the GALLEX and Homestake signals suggest that such a seasonal variation could be present, future detectors (BOREXINO, LENS and probably GNO) will be able to test it.

  16. High Cadence Observations and Analysis of Spicular-type Events Using CRISP Onboard SST

    NASA Astrophysics Data System (ADS)

    Shetye, J.; Doyle, J. G.; Scullion, E.; Nelson, C. J.; Kuridze, D.

    2016-04-01

    We present spectroscopic and imaging observations of apparent ultra-fast spicule-like features observed with CRisp Imaging SpectroPolarimeter (CRISP) at the Swedish 1-m Solar Telescope (SST). The data shows spicules with an apparent velocity above 500 km s-1, very short lifetimes of up to 20 s and length/height around 3500 km. The spicules are seen as dark absorption structures in the Hα wings ±516 mÅ, ±774 mÅ and ±1032 mÅ which suddenly appear and disappear from the FOV. These features show a time delay in their appearance in the blue and red wings by 3-5 s. We suggest that their appearance/disappearance is due to their Doppler motion in and out of the 60 mÅ filter. See Fig. 1 for the evolution of the event at two line positions.

  17. Pioneer 9 and Pioneer 10 observations of the solar wind associated with the August 1972 events

    NASA Technical Reports Server (NTRS)

    Intriligator, D. S.

    1977-01-01

    Observations are presented of the changes in the solar wind proton parameters at 0.8 and 2.2 AU as a result of the solar flares in August 1972. These observations were obtained by the NASA Ames Research Center solar wind plasma analyzer experiments on Pioneer 9 and Pioneer 10. High time resolution measurements are presented of the solar wind proton speed associated with the arrival of the interplanetary shocks at Pioneer 9 and Pioneer 10. For these events, differential ion energy per unit charge spectra are shown which indicate the changes in the solar wind ion distribution function associated with the arrival of each of the interplanetary shocks. Four fast shocks are identified at Pioneer 9, and it is found that previously the time of arrival of the first interplanetary shock at Pioneer 9 was not correctly identified. Two fast shocks and one reverse shock are identified at Pioneer 10.

  18. The Connection between the Corona and Chromosphere during a Multiple Event Observation

    NASA Technical Reports Server (NTRS)

    Cirtain, Jonathan

    2008-01-01

    NOAA AR 10940 (Jan 25 2007 - Feb 09 2007) rotated into view producing a CME and EIT wave, and followed by at least 27 B and C class flares as rotated across the disk. As it reached the west limb it proceeded to produce a sequence of jets and filament eruptions that were observed in unprecedented detail. I present observations from TRACE, EIT, HINODE XRT / SOT / EIS, RHESSI, GOES 12 and STEREO-A COR 1 to investigate part of the sequence of events that lead to a filament eruption and sympathetic jet at 02:30 - 03:00 02/09/07. I concentrate on the topology changes and infer that external breakout reconnection was the mechanism that lead to the removal of overlying field and subsequent filament eruption I will also discuss the instrument development activities at MSFC.

  19. Observations of reverse polarity flux transfer events at the earth's dayside magnetopause

    NASA Technical Reports Server (NTRS)

    Rijnbeek, R. P.; Cowley, S. W. H.; Southwood, D. J.; Russell, C. T.

    1982-01-01

    High resolution plasma and magnetic field measurements made by the ISEE 1 and 2 spacecraft have provided the first definitive observations of magnetic reconnection at the dayside boundary, occurring either as a large-scale, quasisteady process enduring on time scales of at least tens of minutes or as a transient process localized in both temporal and spatial extent. Observations of flux transfer events (FTEs) at the earth's dayside magnetopause are presented which have plasma and magnetic field signatures reversed in sign from those previously reported. These FTEs are interpreted in terms of localized and transitory reconnection with the spacecraft located south of the reconnection site. They are associated with a previously reported interval of quasisteady reconnection which is similarly located, indicating that a close physical connection exists between the two processes.

  20. Saharan dust event over Bucharest observed by an elastic backscatter lidar

    NASA Astrophysics Data System (ADS)

    Talianu, Camelia; Nicolae, Doina; Nemuc, Anca; Belegante, Livio; Carstea, Emil

    2007-10-01

    A lidar measurements campaign took in Magurele Platform, southwestern part of Bucharest, during on June 25th, 26th and 28th of 2007 and was intended for aerosol loading characteristics over the urban area. An event of long-range Saharan dust transport to Eastern Europe, Romania) observed during this time is presented in here. We have used an elastic backscattering lidar, based on an Nd:YAG laser, at 1064nm sounding wavelength. It can detect in real time aerosols density profiles up to 10 Km high with a spatial resolution of 12 m. Origin of lidar sampled air masses arriving at various heights over Bucharest have been determined by the analytical back-trajectories from NOAA HYSPLIT model. Saharan dust layers reached the southern part of Romania predominantly by cyclonic circulation due to the strong through observed at all the levels from a cyclonic system located in northwestern part of Africa. Analysis of cloud cover and dust load was estimated by the Dust Regional Atmospheric Modeling (Dream model). The dust event presented highlights how the synergy of Lidar data together with 3-D back trajectories analysis and model calculations can improve our ability to determine accurately the source of high aerosol loading.

  1. Estimating observing locations for advancing beyond the winter predictability barrier of Indian Ocean dipole event predictions

    NASA Astrophysics Data System (ADS)

    Feng, Rong; Duan, Wansuo; Mu, Mu

    2017-02-01

    In this paper, we explored potential observing locations (i.e., the sensitive areas) of positive Indian Ocean dipole (IOD) events to advance beyond the winter predictability barrier (WPB) using the geophysical fluid dynamics laboratory climate model version 2p1 (GFDL CM2p1). The sensitivity analysis is conducted through perfect model predictability experiments, in which the model is assumed to be perfect and so any prediction errors are caused by initial errors. The results show that the initial errors with an east-west dipole pattern are more likely to result in a significant WPB than spatially correlated noises; the areas where the large values of the dipole pattern initial errors are located have great effects on prediction uncertainties in winter and provide useful information regarding the sensitive areas. Further, the prediction uncertainties in winter are more sensitive to the initial errors in the subsurface large value areas than to those in the surface large value areas. The results indicate that the subsurface large value areas are sensitive areas for advancing beyond the WPB of IOD predictions and if we carry out intensive observations across these areas, the prediction errors in winter may be largely reduced. This will lead to large improvements in the skill of wintertime IOD event forecasts.

  2. Fingerprints of a riming event on cloud radar Doppler spectra: observations and modeling

    NASA Astrophysics Data System (ADS)

    Kalesse, H.; Szyrmer, W.; Kneifel, S.; Kollias, P.; Luke, E.

    2015-10-01

    Radar Doppler spectra measurements are exploited to study a riming event when precipitating ice from a seeder cloud sediments through a supercooled liquid water (SLW) layer. The observations were collected during the deployment of the Atmospheric Radiation Measurement Program's (ARM) mobile facility AMF2 at Hyytiälä, Finland during the BAECC (Biogenic Aerosols - Effects on Clouds and Climate Snowfall Experiment) field campaign. The presented analysis of the height evolution of the radar Doppler spectra is a state-of-the-art retrieval with profiling cloud radars in SLW layers beyond the traditional use of spectral moments. Dynamical effects are taken into account by following the particle population evolution along slanted tracks that are caused by horizontal advection of the cloud under wind shear conditions. In the SLW layer, the identified liquid peak is used as an air motion tracer to correct the Doppler spectra for vertical air motion and the ice peak is used to study the radar profiles of rimed particles. A 1-D steady-state bin microphysical model is constrained using the SLW and air motion profiles and cloud top radar observations. The observed radar moment profiles of the rimed snow can be simulated reasonably well by the model, but not without making several assumptions about the ice particle concentration and the relative role of deposition and aggregation. This suggests that in-situ observations of key ice properties are needed to complement the profiling radar observations before process-oriented studies can effectively evaluate ice microphysical parameterizations.

  3. Unusual optical observations of OI greenline during a geospace event on 1 February 2008

    NASA Astrophysics Data System (ADS)

    Narayanan, V. Lakshmi; Gurubaran, S.; Emperumal, K.; Patil, P. T.

    2011-09-01

    We herein report the first observations of an unusual phenomenon recorded by an all-sky airglow imager from the low-latitude site Panhala (16.8°N, 74.1°E, geographic; 8.2°N geomagnetic), on the night of 1 February 2008, during the main phase of a moderate geomagnetic storm. The observations of OI 557.7 nm emission reveal discrete, transient, filamentary structures referred to as “streaks.” No such features were seen in the OI 630.0 nm emission and the mesospheric sodium and hydroxyl emissions. Here we speculate on possible mechanisms for generation of such structures, though we cannot conclude firmly that any one of them was responsible for the observed features. This is a puzzling observation made from very low geomagnetic latitude during the main phase of a moderate recurrent geomagnetic storm in the declining phase of solar cycle. In spite of the limitations in identifying the mechanism or mechanisms responsible for this striking observation, it is felt that understanding of processes driving such unusual and rare events will substantiate our knowledge on the mysterious coupling processes occurring in the equatorial upper atmosphere.

  4. 3D Evolution of a Filament Disappearance Event Observed by STEREO

    NASA Astrophysics Data System (ADS)

    Gosain, S.; Schmieder, B.; Venkatakrishnan, P.; Chandra, R.; Artzner, G.

    2009-10-01

    A filament disappearance event was observed on 22 May 2008 during our recent campaign JOP 178. The filament, situated in the Southern Hemisphere, showed sinistral chirality consistent with the hemispheric rule. The event was well observed by several observatories, in particular by THEMIS. One day, before the disappearance, Hα observations showed up- and down-flows in adjacent locations along the filament, which suggest plasma motions along twisted flux rope. THEMIS and GONG observations show shearing photospheric motions leading to magnetic flux canceling around barbs. STEREO A, B spacecraft with separation angle 52.4°, showed quite different views of this untwisting flux rope in He ii 304 Å images. Here, we reconstruct the three-dimensional geometry of the filament during its eruption phase using STEREO EUV He ii 304 Å images and find that the filament was highly inclined to the solar normal. The He ii 304 Å movies show individual threads, which oscillate and rise to an altitude of about 120 Mm with apparent velocities of about 100 km s-1 during the rapid evolution phase. Finally, as the flux rope expands into the corona, the filament disappears by becoming optically thin to undetectable levels. No CME was detected by STEREO, only a faint CME was recorded by LASCO at the beginning of the disappearance phase at 02:00 UT, which could be due to partial filament eruption. Further, STEREO Fe xii 195 Å images showed bright loops beneath the filament prior to the disappearance phase, suggesting magnetic reconnection below the flux rope.

  5. Observational survey of the puzzling star HD 179821: Photometric variations and period analysis

    NASA Astrophysics Data System (ADS)

    Le Coroller, H.; Lèbre, A.; Gillet, D.; Chapellier, E.

    2003-03-01

    From new photometric observations (UBVRI), we present the characteristic features of the light variations of the evolved star HD 179821 (= SAO 124414 = IRAS 19114+0002). Our data, collected through 1999 and 2000, have been combined together with previous photometric measurements available in the literature. Thus, a long term V-light curve (gathering more than 10 years of observations for HD 179821) has been composed. We have analysed it with the Fourier transform method. Two main frequencies are present in the resulting power spectrum, reflecting a dominant bimodal pulsator behavior. A long term phenomenon is also found, but it is not possible to decide whether it is periodic. The Fourier analysis has also been applied on two other filters (U and B) and confirms the detected frequencies. On the basis of our period analysis, we discuss the nature of HD 179821: low-mass post-AGB star or high-mass star. based on observations carried out at the Observatoire de Haute Provence, France, operated by the Centre National de la Recherche Scientifique (CNRS).

  6. Subarcsecond bright points and quasi-periodic upflows below a quiescent filament observed by IRIS

    NASA Astrophysics Data System (ADS)

    Li, T.; Zhang, J.

    2016-05-01

    Context. The new Interface Region Imaging Spectrograph (IRIS) mission provides high-resolution observations of UV spectra and slit-jaw images (SJIs). These data have become available for investigating the dynamic features in the transition region (TR) below the on-disk filaments. Aims: The driver of "counter-streaming" flows along the filament spine is still unknown yet. The magnetic structures and the upflows at the footpoints of the filaments and their relations with the filament mainbody have not been well understood. We study the dynamic evolution at the footpoints of filaments in order to find some clues for solving these questions. Methods: Using UV spectra and SJIs from the IRIS, along with coronal images and magnetograms from the Solar Dynamics Observatory (SDO), we present the new features in a quiescent filament channel: subarcsecond bright points (BPs) and quasi-periodic upflows. Results: The BPs in the TR have a spatial scale of about 350-580 km and lifetimes of more than several tens of minutes. They are located at stronger magnetic structures in the filament channel with a magnetic flux of about 1017-1018 Mx. Quasi-periodic brightenings and upflows are observed in the BPs, and the period is about 4-5 min. The BP and the associated jet-like upflow comprise a "tadpole-shaped" structure. The upflows move along bright filament threads, and their directions are almost parallel to the spine of the filament. The upflows initiated from the BPs with opposite polarity magnetic fields have opposite directions. The velocity of the upflows in the plane of sky is about 5-50 km s-1. The emission line of Si IV 1402.77 Å at the locations of upflows exhibits obvious blueshifts of about 5-30 km s-1, and the line profile is broadened with the width of more than 20 km s-1. Conclusions: The BPs seem to be the bases of filament threads, and the upflows are able to convey mass for the dynamic balance of the filament. The "counter-streaming" flows in previous observations

  7. Detection of Rain-on-Snow (ROS) Events Using the Advanced Microwave Scanning Radiometer-Earth Observing System (AMSR-E) and Weather Station Observations

    NASA Astrophysics Data System (ADS)

    Ryan, E. M.; Brucker, L.; Forman, B. A.

    2015-12-01

    During the winter months, the occurrence of rain-on-snow (ROS) events can impact snow stratigraphy via generation of large scale ice crusts, e.g., on or within the snowpack. The formation of such layers significantly alters the electromagnetic response of the snowpack, which can be witnessed using space-based microwave radiometers. In addition, ROS layers can hinder the ability of wildlife to burrow in the snow for vegetation, which limits their foraging capability. A prime example occurred on 23 October 2003 in Banks Island, Canada, where an ROS event is believed to have caused the deaths of over 20,000 musk oxen. Through the use of passive microwave remote sensing, ROS events can be detected by utilizing observed brightness temperatures (Tb) from AMSR-E. Tb observed at different microwave frequencies and polarizations depends on snow properties. A wet snowpack formed from an ROS event yields a larger Tb than a typical dry snowpack would. This phenomenon makes observed Tb useful when detecting ROS events. With the use of data retrieved from AMSR-E, in conjunction with observations from ground-based weather station networks, a database of estimated ROS events over the past twelve years was generated. Using this database, changes in measured Tb following the ROS events was also observed. This study adds to the growing knowledge of ROS events and has the potential to help inform passive microwave snow water equivalent (SWE) retrievals or snow cover properties in polar regions.

  8. AROME-WMED, a real-time mesoscale model designed for the HyMeX Special Observation Periods

    NASA Astrophysics Data System (ADS)

    Fourrié, N.; Bresson, É.; Nuret, M.; Jany, C.; Brousseau, P.; Doerenbecher, A.; Kreitz, M.; Nuissier, O.; Sevault, E.; Bénichou, H.; Amodei, M.; Pouponneau, F.

    2015-02-01

    During autumn 2012 and winter 2013, two Special Observation Periods (SOPs) of the Hydrological cycle in the Mediterranean Experiment (HyMeX) took place. For the preparatory studies and to support the instrument deployment during the field campaign, a dedicated version of the operational convective-scale AROME-France model was developed: the AROME-WMED model. It covers the western Mediterranean basin with a 48 h forecast range. It provided real time analyses and forecasts which were sent daily to the HyMeX operational centre to forecast high precipitation events and to help decision makers on the deployment of observation instruments. This paper presents the main features of this numerical weather prediction system in terms of data assimilation and forecast. Some specific data of the HyMeX SOP were assimilated in real time. The forecast skill of the AROME-WMED is then assessed with objective scores and compared to the operational AROME-France model, for both autumn 2012 (5 September to 6 November 2012) and winter 2013 (1 February to 15 March 2013) SOPs. The overall performance of AROME-WMED is good and similar to those of AROME-France for the 0 to 30 h common forecast range. The 24 to 48 h forecast range is of course less accurate but remains useful for scheduling observation deployment. The characteristics of parameters such as precipitation, temperature or humidity, are illustrated by one heavy precipitation case study that occurred over the south of Spain.

  9. Direct experimental observation of periodic intensity modulation along a straight hollow-core optical waveguide

    SciTech Connect

    Pfeifer, T.; Downer, M. C.

    2007-05-15

    We report the direct observation of periodic intensity modulation of a laser pulse propagating in a hollow-core waveguide. A series of equally spaced plasma sparks along the gas-filled capillary is produced. This effect can be explained by the beating of different fiber modes, which are excited by controlling the size of the focal spot at the capillary entrance. As compared with an artificial modulated waveguide structure, our presented approach represents an easier and more flexible quasi-phase-matching scheme for nonlinear-optical frequency conversion.

  10. Fog Induced Aerosol Modification Observed by AERONET, Including Occurrences During Major Air Pollution Events

    NASA Astrophysics Data System (ADS)

    Eck, T. F.; Holben, B. N.; Reid, J. S.; Giles, D. M.; Rivas, M.; Singh, R. P.; Tripathi, S. N.; Bruegge, C. J.; Li, Z.; Platnick, S. E.; Arnold, T.; Ferrare, R. A.; Hostetler, C. A.; Burton, S. P.; Kim, J.; Kim, Y. J.; Sinyuk, A.; Dubovik, O.; Arola, A. T.; Schafer, J.; Artaxo, P.; Smirnov, A.; Chen, H.; Goloub, P.

    2015-12-01

    The modification of aerosol optical properties due to interaction with fog is examined from measurements made by sun/sky radiometers at several AERONET sites. Retrieved total column volume size distributions for cases identified as aerosol modified by fog often show very a large 'middle mode' submicron radius (~0.4 to 0.5 microns), which is typically seen as a component of a bimodal sub-micron distribution. These middle mode sized particles are often called cloud-processed or residual aerosol. This bimodal accumulation mode distribution may be due to one mode (the larger one) from fog-processed aerosol and the other from interstitial aerosol, or possibly from two different aerosol species (differing chemical composition) with differing hygroscopic growth factors. The size of the fine mode particles from AERONET retrieved for these cases exceeds the size of sub-micron sized particles retrieved for nearly all other aerosol types, suggesting significant modification of aerosols within the fog or cloud environment. In-situ measured aerosol size distributions made during other fog events are compared to the AERONET retrievals, and show close agreement in the residual mode particle size. Almucantar retrievals are analyzed from the Kanpur site in the Indo-Gangetic Plain in India (fog in January), Beijing (fog in winter), Fresno, CA in the San Joaquin Valley (fog in winter), South Korea (Yellow Sea fog in spring), Arica on the northern coast of Chile (stratocumulus), and several other sites with aerosol observations made after fog dissipated. Additionally, several major air pollution events are discussed where extremely high aerosol concentrations were measured at the surface and during which fog also occurred, resulting in the detection very large fine mode aerosols (residual mode) from AERONET retrievals in some of these events. Low wind speeds that occurred during these events were conducive to both pollutant accumulation and also fog formation. The presence of fog then

  11. Source mechanism of small long-period events at Mount St. Helens in July 2005 using template matching, phase-weighted stacking, and full-waveform inversion

    USGS Publications Warehouse

    Matoza, Robin S.; Chouet, Bernard A.; Dawson, Phillip B.; Shearer, Peter M.; Haney, Matthew M.; Waite, Gregory P.; Moran, Seth C.; Mikesell, T. Dylan

    2015-01-01

    Long-period (LP, 0.5-5 Hz) seismicity, observed at volcanoes worldwide, is a recognized signature of unrest and eruption. Cyclic LP “drumbeating” was the characteristic seismicity accompanying the sustained dome-building phase of the 2004–2008 eruption of Mount St. Helens (MSH), WA. However, together with the LP drumbeating was a near-continuous, randomly occurring series of tiny LP seismic events (LP “subevents”), which may hold important additional information on the mechanism of seismogenesis at restless volcanoes. We employ template matching, phase-weighted stacking, and full-waveform inversion to image the source mechanism of one multiplet of these LP subevents at MSH in July 2005. The signal-to-noise ratios of the individual events are too low to produce reliable waveform-inversion results, but the events are repetitive and can be stacked. We apply network-based template matching to 8 days of continuous velocity waveform data from 29 June to 7 July 2005 using a master event to detect 822 network triggers. We stack waveforms for 359 high-quality triggers at each station and component, using a combination of linear and phase-weighted stacking to produce clean stacks for use in waveform inversion. The derived source mechanism pointsto the volumetric oscillation (~10 m3) of a subhorizontal crack located at shallow depth (~30 m) in an area to the south of Crater Glacier in the southern portion of the breached MSH crater. A possible excitation mechanism is the sudden condensation of metastable steam from a shallow pressurized hydrothermal system as it encounters cool meteoric water in the outer parts of the edifice, perhaps supplied from snow melt.

  12. Source mechanism of small long-period events at Mount St. Helens in July 2005 using template matching, phase-weighted stacking, and full-waveform inversion

    NASA Astrophysics Data System (ADS)

    Matoza, Robin S.; Chouet, Bernard A.; Dawson, Phillip B.; Shearer, Peter M.; Haney, Matthew M.; Waite, Gregory P.; Moran, Seth C.; Mikesell, T. Dylan

    2015-09-01

    Long-period (LP, 0.5-5 Hz) seismicity, observed at volcanoes worldwide, is a recognized signature of unrest and eruption. Cyclic LP "drumbeating" was the characteristic seismicity accompanying the sustained dome-building phase of the 2004-2008 eruption of Mount St. Helens (MSH), WA. However, together with the LP drumbeating was a near-continuous, randomly occurring series of tiny LP seismic events (LP "subevents"), which may hold important additional information on the mechanism of seismogenesis at restless volcanoes. We employ template matching, phase-weighted stacking, and full-waveform inversion to image the source mechanism of one multiplet of these LP subevents at MSH in July 2005. The signal-to-noise ratios of the individual events are too low to produce reliable waveform inversion results, but the events are repetitive and can be stacked. We apply network-based template matching to 8 days of continuous velocity waveform data from 29 June to 7 July 2005 using a master event to detect 822 network triggers. We stack waveforms for 359 high-quality triggers at each station and component, using a combination of linear and phase-weighted stacking to produce clean stacks for use in waveform inversion. The derived source mechanism points to the volumetric oscillation (˜10 m3) of a subhorizontal crack located at shallow depth (˜30 m) in an area to the south of Crater Glacier in the southern portion of the breached MSH crater. A possible excitation mechanism is the sudden condensation of metastable steam from a shallow pressurized hydrothermal system as it encounters cool meteoric water in the outer parts of the edifice, perhaps supplied from snow melt.

  13. Observation of gamma rays with a 4.8 hour periodicity from CYG X-3

    NASA Technical Reports Server (NTRS)

    Lamb, R. C.; Fichtel, C. E.; Hartman, R. C.; Kniffen, D. A.; Thompson, D. J.

    1976-01-01

    Energetic (E35 MeV) Gamma rays were observed from Cyg X-3 with the SAS-2 Gamma ray telescope. They are modulated at the 4.8 sup h period observed in the X-ray and infrared regions, and within the statistical error are in phase with this emission. The flux above 100 MeV has an average value of (4.4 + or - 1.1)x 10 to the -6 power/sq cm/sec. If the distance to Cyg X-3 is 10 kpcs, this flux implies a luminosity of more than 10 to the 37th power ergs/s if the radiation is isotropic and about 10 to the 36th power ergs/s if the radiation is restricted to a cone of one steradian, as it might be in a pulsar.

  14. Bringing Order to Life Events: Memory for the Temporal Order of Autobiographical Events over an Extended Period in School-Aged Children and Adults

    ERIC Educational Resources Information Center

    Pathman, Thanujeni; Doydum, Ayzit; Bauer, Patricia J.

    2013-01-01

    Remembering temporal information associated with personal past events is critical. Yet little is known about the development of temporal order memory for naturally occurring events. In the current research, 8- to 10-year-old children and adults took photographs daily for 4 weeks. Later, they participated in a primacy/recency task (were shown 2 of…

  15. Magnetic Upflow Events in the Quiet-Sun Photosphere. I. Observations

    NASA Astrophysics Data System (ADS)

    Jafarzadeh, S.; Rouppe van der Voort, L.; de la Cruz Rodríguez, J.

    2015-09-01

    Rapid magnetic upflows in the quiet-Sun photosphere were recently uncovered from both Sunrise/IMaX and Hinode/SOT observations. Here, we study magnetic upflow events (MUEs) from high-quality, high- (spatial, temporal, and spectral) resolution, and full Stokes observations in four photospheric magnetically sensitive Fe i lines centered at 5250.21, 6173.34, 6301.51, and 6302.50 Å acquired with the Swedish Solar Telescope (SST)/CRISP. We detect MUEs by subtracting in-line Stokes V signals from those in the far blue wing whose signal-to-noise ratio (S/N) ≥slant 7. We find a larger number of MUEs at any given time (2.0× {10}-2 arcsec-2), larger by one to two orders of magnitude, than previously reported. The MUEs appear to fall into four classes presenting different shapes of Stokes V profiles with (I) asymmetric double lobes, (II) single lobes, (III) double-humped (two same-polarity lobes), and (IV) three lobes (an extra blueshifted bump in addition to double lobes), of which less than half are single-lobed. We also find that MUEs are almost equally distributed in network and internetwork areas and they appear in the interior or at the edge of granules in both regions. Distributions of physical properties, except for horizontal velocity, of the MUEs (namely, Stokes V signal, size, line-of-sight velocity, and lifetime) are almost identical for the different spectral lines in our data. A bisector analysis of our spectrally resolved observations shows that these events host modest upflows and do not show a direct indication of the presence of supersonic upflows reported earlier. Our findings reveal that the numbers, types (classes), and properties determined for MUEs can strongly depend on the detection techniques used and the properties of the employed data, namely, S/Ns, resolutions, and wavelengths.

  16. Quasi-periodic frequency fluctuations observed during coronal radio sounding experiments 1991-2009

    NASA Astrophysics Data System (ADS)

    Efimov, Anatoli; Lukanina, L. A.; Samoznaev, Lev; Rudash, V. K.; Chashei, Igor; Bird, Michael; Paetzold, Martin

    Recent coronal radio sounding experiments with the ESA spacecraft Mars Express (MEX), Venus Express (VEX) and Rosetta (ROS) have provided a large volume of observational data supporting the presence of a quasi-periodic component (QPC) in frequency fluctuation spectra during solar conjunction. Further evidence for the QPC, first seen in data from the MEX conjunction in 2004, was found later in data from the MEX conjunctions in 2006 and 2008/09, as well as the VEX and ROS conjunctions in 2006. The QPC is detected with an occurrence frequency ≈ 18% (83.3 hours of the total 462.7 hours of data). In some cases the temporal spectra reveal two lines: the main QPC and its second harmonic. The average frequency of the spectral density maximum is νmax ≈ 5.5 mHz (corresponding QPC fluctuation period ≈ 3 min) at solar offset distances R < 8 Rs. The QPC spectral density maximum Gmax reaches an average factor of 2.88 above the background level G0 . The bandwidth of the spectral line ∆ν ≈ νmax . At larger solar distances (R > 8 Rs) the fluctuation frequency of the mean spectral density maximum is νmax ≈ 4.3 mHz (period ≈ 4 min). Both the fractional spectral line bandwidth ∆ν/νmax and the excess of spectral density Gmax above background are nearly unchanged from their values nearer the Sun. A reanalysis of earlier coronal sounding data obtained with the Ulysses (1991, 1995) and Galileo (1996/97) spacecraft has verified the existence of the QPC. Typical fluctuation periods lie between 4 and 5 min, but the QPC occurrence rate (12%) is smaller than that observed for MEX-VEX-ROS. This may be associated with the lower received signal level of Ulysses and Galileo compared to the ESA spacecraft. The Ulysses coronal sounding experiments in 1995 provided an interesting possibility to observe the QPC at high solar latitudes. Preliminary results show that the QPC frequency can reach νmax = 6-7 mHz at heliolatitudes 60° -80° .

  17. Stochastic generation of flood events to extend observed hydrological series by combining a copula model with hydrometeorological modelling

    NASA Astrophysics Data System (ADS)

    Requena, Ana; Flores, Isabel; Mediero, Luis; Garrote, Luis

    2013-04-01

    A multivariate flood frequency analysis is required for designing some structures like dams. Multivariate copula models are usually used to obtain joint return periods of the flood variables. There exist several families of copulas and a selection procedure is required to find the copula that best fits the observations. Moreover, observed hydrological series are usually short and the fit of the right tail of the copula remains highly uncertain. In this work, a procedure to extend short observed series is proposed by the use of both hydrometeorological modelling and a copula model to generate synthetic hydrographs. The procedure takes synthetic rainstorms events generated by the RainSim software as input. The RIBS rainfall-runoff model is used to simulate the hydrological processes in the basin. The procedure was tested in the Santillana reservoir in Spain, were both RainSim and RIBS models were calibrated prior to this study. A sensitivity analysis was conducted in order to find the minimum synthetic length that makes the copula selection process robust enough. As computational time of hydrometeorological modelling is not negligible, the extended record from modelling results could be re-extended by the fitted copula, reducing the computation time. This final extended hydrological series can be used to improve flood risk assessment studies. Key words: Stochastic generation, copulas, rainfall-runoff modelling Session: HS7.15 - Hydroclimatic stochastics Convener: S. Grimaldi Co-Conveners: A. A. Carsteanu, D. Koutsoyiannis, X. L. Wang and S. M. Papalexiou

  18. A mesoscale gravity wave event observed during CCOPE. I - Multiscale statistical analysis of wave characteristics

    NASA Technical Reports Server (NTRS)

    Koch, Steven E.; Golus, Robert E.

    1988-01-01

    This paper presents a statistical analysis of the characteristics of the wavelike activity that occurred over the north-central United States on July 11-12, 1981, using data from the Cooperative Convective Precipitation Experiment in Montana. In particular, two distinct wave episodes of about 8-h duration within a longer (33 h) period of wave activity were studied in detail. It is demonstrated that the observed phenomena display features consistent with those of mesoscale gravity waves. The principles of statistical methods used to detect and track mesoscale gravity waves are discussed together with their limitations.

  19. Observing a fictitious stressful event: haematological changes, including circulating leukocyte activation.

    PubMed

    Mian, Rubina; Shelton-Rayner, Graham; Harkin, Brendan; Williams, Paul

    2003-03-01

    The aim of this study was to assess the effect of watching a psychological stressful event on the activation of leukocytes in healthy human volunteers. Blood samples were obtained from 32 healthy male and female subjects aged between 20 and 26 years before, during and after either watching an 83-minute horror film that none of the subjects had previously seen (The Texas Chainsaw Massacre, 1974) or by sitting quietly in a room (control group). Total differential cell counts, leukocyte activation as measured by the nitroblue tetrazolium (NBT) test, heart rate and blood pressure (BP) measurements were taken at defined time points. There were significant increases in peripheral circulating leukocytes, the number of activated circulating leukocytes, haemoglobin (Hb) concentration and haematocrit (Hct) in response to the stressor. These were accompanied by significant increases in heart rate, systolic and diastolic BP (P<0.05 from baseline). This is the first reported study on the effects of observing a psychologically stressful, albeit fictitious event on circulating leukocyte numbers and the state of leukocyte activation as determined by the nitrotetrazolium test.

  20. Continuous ground-based aerosol Lidar observation during seasonal pollution events at Wuxi, China

    NASA Astrophysics Data System (ADS)

    Wong, Man Sing; Qin, Kai; Lian, Hong; Campbell, James R.; Lee, Kwon Ho; Sheng, Shijie

    2017-04-01

    Haze pollution has long been a significant research topic and challenge in China, with adverse effects on air quality, agricultural production, as well as human health. In coupling with ground-based Lidar measurements, air quality observation, meteorological data, and backward trajectories model, two typical haze events at Wuxi, China are analyzed respectively, depicting summer and winter scenarios. Results indicate that the winter haze pollution is a compound pollution process mainly affected by calm winds that induce pollution accumulation near the surface. In the summer case, with the exception of influence from PM2.5 concentrations, ozone is the main pollutant and regional transport is also a significant influencing factor. Both events are marked by enhanced PM2.5 concentrations, driven by anthropogenic emissions of pollutants such as vehicle exhaust and factory fumes. Meteorological factors such as wind speed/direction and relative humidity are also contributed. These results indicate how the vertical profile offered by routine regional Lidar monitoring helps aid in understanding local variability and trends, which may be adapted for developing abatement strategies that improve air quality.

  1. Underlying-event sensitive observables in Drell-Yan production using GENEVA

    NASA Astrophysics Data System (ADS)

    Alioli, Simone; Bauer, Christian W.; Guns, Sam; Tackmann, Frank J.

    2016-11-01

    We present an extension of the Geneva Monte Carlo framework to include multiple parton interactions (MPI) provided by Pythia8. This allows us to obtain predictions for underlying-event sensitive measurements in Drell-Yan production, in conjunction with Geneva 's fully differential NNLO calculation, NNLL' resummation for the 0-jet resolution variable (beam thrust), and NLL resummation for the 1-jet resolution variable. We describe the interface with the parton-shower algorithm and MPI model of Pythia8, which preserves both the precision of the partonic N-jet cross sections in Geneva as well as the shower accuracy and good description of soft hadronic physics of Pythia8. We present results for several underlying-event sensitive observables and compare to data from ATLAS and CMS as well as to standalone Pythia8 predictions. This includes a comparison with the recent ATLAS measurement of the beam thrust spectrum, which provides a potential avenue to fully disentangle the physical effects from the primary hard interaction, primary soft radiation, multiple parton interactions, and nonperturbative hadronization.

  2. Intermittent turbulence events observed with a sonic anemometer and minisodar during CASES99.

    SciTech Connect

    Coulter, R. L.; Doran, J. C.

    2000-05-12

    The Cooperative Air Surface Exchange Study 1999 (CASES99), designed to investigate in detail the nocturnal boundary layer (NBL) of the atmosphere with particular emphasis on turbulence and turbulence events, took place during October 1999, within the Atmospheric Boundary Layer Experiments (ABLE) region east of Wichita KS. The principal measurement site was a heavily instrumented 2-km square located near Leon (LE), KS, but additional sites at Smileyberg (SM) and Beaumont (BE) were also used. The authors augmented the normal ABLE measurements at Beaumont (radar wind profiler, minisodar, 10-m meteorological tower, precipitation gauge) with a sonic anemometer mounted on the tower, 7 m above the surface. For this campaign, the minisodar data were saved in single-pulse mode with no averaging. The Beaumont site is within gently rolling rangeland used primarily for grazing. The site is on a flat plain rising gradually to the east.The Flint Hills escarpment, located approximately 2 km to the east, marks the highest point in, and the eastern boundary of, the Walnut River watershed. Although most terrain features are subtle, terrain effects on atmospheric flows are still possible, particularly in stable conditions. The intent was to observe turbulence and, hopefully, turbulence events with the sonic anemometer and minisodar. The horizontal extent of these occurrences can be studied by including the Beaumont data with those obtained at the Leon site. In this report the authors are concerned with the occurrence of intermittent turbulence.

  3. OBSERVATIONAL EVIDENCE ON THE PRESENCE OF AN OUTER REFLECTING BOUNDARY IN SOLAR ENERGETIC PARTICLE EVENTS

    SciTech Connect

    Tan, Lun C.; Reames, Donald V.; Ng, Chee K.; Saloniemi, Oskari; Wang Linghua

    2009-08-20

    We have focused primarily on the 2001 September 24 solar energetic particle (SEP) event to verify previous indications of the presence of an outer reflecting boundary of SEPs. By using energetic electron and ion data obtained from multi-spacecraft observations, we have identified a collimated particle beam consisting of reflected particles returning from an outer boundary. The peak of reflected particles appears before the arrival of particles at 90 deg. pitch angle. In addition, an onset time analysis is carried out in order to determine parameters characterizing the boundary. Our analysis suggests that the presence of a counter-streaming particle beam with a deep depression at {approx}90 deg. pitch angle during the onset phase is evidence for a nearby reflecting boundary. We have compared this property in the SEP events of 2002 April 21 and August 24. A reflecting boundary that blocks a flux tube is important in space weather forecasting since it can cause the 'reservoir' effect that may enhance the intensity and duration of high-energy particles.

  4. An overview of the lightning and atmospheric electricity observations collected in Southern France during the HYdrological cycle in Mediterranean EXperiment (HyMeX), Special Observation Period 1

    NASA Astrophysics Data System (ADS)

    Defer, E.; Pinty, J.-P.; Coquillat, S.; Martin, J.-M.; Prieur, S.; Soula, S.; Richard, E.; Rison, W.; Krehbiel, P.; Thomas, R.; Rodeheffer, D.; Vergeiner, C.; Malaterre, F.; Pedeboy, S.; Schulz, W.; Farges, T.; Gallin, L.-J.; Ortéga, P.; Ribaud, J.-F.; Anderson, G.; Betz, H.-D.; Meneux, B.; Kotroni, V.; Lagouvardos, K.; Roos, S.; Ducrocq, V.; Roussot, O.; Labatut, L.; Molinié, G.

    2014-08-01

    The PEACH (Projet en Electricité Atmosphérique pour la Campagne HyMeX - the Atmospheric Electricity Project of HyMeX Program) project is the Atmospheric Electricity component of the HyMeX (Hydrology cycle in the Mediterranean Experiment) experiment and is dedicated to the observation of both lightning activity and electrical state of continental and maritime thunderstorms in the area of the Mediterranean Sea. During the HyMeX SOP1 (Special Observation Period; 5 September-6 November 2012), four European Operational Lightning Locating Systems (OLLSs) (ATDNET, EUCLID, LINET, ZEUS) and the HyMeX Lightning Mapping Array network (HyLMA) were used to locate and characterize the lightning activity over the Southeastern Mediterranean at flash, storm and regional scales. Additional research instruments like slow antennas, video cameras, micro-barometer and microphone arrays were also operated. All these observations in conjunction with operational/research ground-based and airborne radars, rain gauges and in situ microphysical records aimed at characterizing and understanding electrically active and highly precipitating events over Southeastern France that often lead to severe flash floods. Simulations performed with Cloud Resolving Models like Meso-NH and WRF are used to interpret the results and to investigate further the links between dynamics, microphysics, electrification and lightning occurrence. A description of the different instruments deployed during the field campaign as well as the available datasets is given first. Examples of concurrent observations from radio frequency to acoustic for regular and atypical lightning flashes are then presented showing a rather comprehensive description of lightning flashes available from the SOP1 records. Then examples of storms recorded during HyMeX SOP1 over Southeastern France are briefly described to highlight the unique and rich dataset collected. Finally the next steps of the work required for the delivery of reliable

  5. SDSS-IV MaNGA: A Serendipitous Observation of a Potential Gas Accretion Event

    NASA Astrophysics Data System (ADS)

    Cheung, Edmond; Stark, David V.; Huang, Song; Rubin, Kate H. R.; Lin, Lihwai; Tremonti, Christy; Zhang, Kai; Yan, Renbin; Bizyaev, Dmitry; Boquien, Médéric; Brownstein, Joel R.; Drory, Niv; Gelfand, Joseph D.; Knapen, Johan H.; Maiolino, Roberto; Malanushenko, Olena; Masters, Karen L.; Merrifield, Michael R.; Pace, Zach; Pan, Kaike; Riffel, Rogemar A.; Roman-Lopes, Alexandre; Rujopakarn, Wiphu; Schneider, Donald P.; Stott, John P.; Thomas, Daniel; Weijmans, Anne-Marie

    2016-12-01

    The nature of warm, ionized gas outside of galaxies may illuminate several key galaxy evolutionary processes. A serendipitous observation by the MaNGA survey has revealed a large, asymmetric Hα complex with no optical counterpart that extends ≈8″ (≈6.3 kpc) beyond the effective radius of a dusty, starbursting galaxy. This Hα extension is approximately three times the effective radius of the host galaxy and displays a tail-like morphology. We analyze its gas-phase metallicities, gaseous kinematics, and emission-line ratios and discuss whether this Hα extension could be diffuse ionized gas, a gas accretion event, or something else. We find that this warm, ionized gas structure is most consistent with gas accretion through recycled wind material, which could be an important process that regulates the low-mass end of the galaxy stellar mass function.

  6. A twenty-first century California observing network for monitoring extreme weather events

    USGS Publications Warehouse

    White, A.B.; Anderson, M.L.; Dettinger, M.D.; Ralph, F.M.; Hinojosa, A.; Cayan, D.R.; Hartman, R.K.; Reynolds, D.W.; Johnson, L.E.; Schneider, T.L.; Cifelli, R.; Toth, Z.; Gutman, S.I.; King, C.W.; Gehrke, F.; Johnston, P.E.; Walls, C.; Mann, Dorte; Gottas, D.J.; Coleman, T.

    2013-01-01

    During Northern Hemisphere winters, the West Coast of North America is battered by extratropical storms. The impact of these storms is of paramount concern to California, where aging water supply and flood protection infrastructures are challenged by increased standards for urban flood protection, an unusually variable weather regime, and projections of climate change. Additionally, there are inherent conflicts between releasing water to provide flood protection and storing water to meet requirements for water supply, water quality, hydropower generation, water temperature and flow for at-risk species, and recreation. In order to improve reservoir management and meet the increasing demands on water, improved forecasts of precipitation, especially during extreme events, is required. Here we describe how California is addressing their most important and costliest environmental issue – water management – in part, by installing a state-of-the-art observing system to better track the area’s most severe wintertime storms.

  7. Compton sources for the observation of elastic photon-photon scattering events

    NASA Astrophysics Data System (ADS)

    Micieli, D.; Drebot, I.; Bacci, A.; Milotti, E.; Petrillo, V.; Conti, M. Rossetti; Rossi, A. R.; Tassi, E.; Serafini, L.

    2016-09-01

    We present the design of a photon-photon collider based on conventional Compton gamma sources for the observation 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.

  8. An observer-based consensus tracking control and application to event-triggered tracking

    NASA Astrophysics Data System (ADS)

    Hu, Jiangping; Geng, Ji; Zhu, Hong

    2015-02-01

    Leader-follower mechanism provides an important framework for multi-agent consensus problems. In this paper, a consensus tracking problem is investigated for a second-order multi-agent system with a self-active leader. The input (acceleration) to the leader is assumed to be time-varying and unavailable to followers. An observer-based consensus tracking control is designed on the basis of a novel distributed velocity estimation technique. The ultimate boundedness and the stability of the tracking error system are analyzed by virtue of an Input-State-Stability (ISS) Lyapunov function approach. Then, the dynamic consensus tracking control is applied to solve an event-triggered tracking problem. Finally, some numerical simulation results are presented to demonstrate the effectiveness of the proposed consensus tracking control.

  9. Observation of Sudden Ionospheric Disturbances over Istanbul in Response to X-Ray Flare Events

    NASA Astrophysics Data System (ADS)

    Ceren Kalafatoglu Eyiguler, Emine; Kaymaz, Zerefsan; Ceren Moral, Aysegul

    2016-07-01

    Sudden ionospheric disturbances (SID) are the enhanced electron density structures in the D region ionosphere which occur in response to the increase in X-ray flares and EUV flux. SIDs can be monitored using Very Low Frequency (VLF) radio signals (3-30 kHz) which travel between the D-region and the surface of the Earth. In this study, we use SID monitors obtained from the Stanford University Solar Center and two antennas which were built at the Istanbul Technical University to track the ionospheric disturbances in the VLF range. Our antennas are capable of capturing signals from several VLF transmitting stations. In this work, we focus on the variations in the signal strength of the closest VLF transmitting station 'TBB' which is operating at 26.7 kHz frequency at BAFA, Turkey (37.43N, 27.15E). We present ITU SID observations from both antennas; show the daily variation, general structure and the typical patterns we observe as well as case studies of significant events. Our initial analysis shows close relationship between observed X-ray flares from geosynchronous GOES 13 and GOES 15 satellites and VLF station signal strength received by the monitors.

  10. Bayesian Techniques for Comparing Time-dependent GRMHD Simulations to Variable Event Horizon Telescope Observations

    NASA Astrophysics Data System (ADS)

    Kim, Junhan; Marrone, Daniel P.; Chan, Chi-Kwan; Medeiros, Lia; Özel, Feryal; Psaltis, Dimitrios

    2016-12-01

    The Event Horizon Telescope (EHT) is a millimeter-wavelength, very-long-baseline interferometry (VLBI) experiment that is capable of observing black holes with horizon-scale resolution. Early observations have revealed variable horizon-scale emission in the Galactic Center black hole, Sagittarius A* (Sgr A*). Comparing such observations to time-dependent general relativistic magnetohydrodynamic (GRMHD) simulations requires statistical tools that explicitly consider the variability in both the data and the models. We develop here a Bayesian method to compare time-resolved simulation images to variable VLBI data, in order to infer model parameters and perform model comparisons. We use mock EHT data based on GRMHD simulations to explore the robustness of this Bayesian method and contrast it to approaches that do not consider the effects of variability. We find that time-independent models lead to offset values of the inferred parameters with artificially reduced uncertainties. Moreover, neglecting the variability in the data and the models often leads to erroneous model selections. We finally apply our method to the early EHT data on Sgr A*.

  11. Fingerprints of a riming event on cloud radar Doppler spectra: observations and modeling

    SciTech Connect

    Kalesse, Heike; Szyrmer, Wanda; Kneifel, Stefan; Kollias, Pavlos; Luke, Edward

    2016-03-09

    In this paper, Radar Doppler spectra measurements are exploited to study a riming event when precipitating ice from a seeder cloud sediment through a supercooled liquid water (SLW) layer. The focus is on the "golden sample" case study for this type of analysis based on observations collected during the deployment of the Atmospheric Radiation Measurement Program's (ARM) mobile facility AMF2 at Hyytiälä, Finland, during the Biogenic Aerosols – Effects on Clouds and Climate (BAECC) field campaign. The presented analysis of the height evolution of the radar Doppler spectra is a state-of-the-art retrieval with profiling cloud radars in SLW layers beyond the traditional use of spectral moments. Dynamical effects are considered by following the particle population evolution along slanted tracks that are caused by horizontal advection of the cloud under wind shear conditions. In the SLW layer, the identified liquid peak is used as an air motion tracer to correct the Doppler spectra for vertical air motion and the ice peak is used to study the radar profiles of rimed particles. A 1-D steady-state bin microphysical model is constrained using the SLW and air motion profiles and cloud top radar observations. The observed radar moment profiles of the rimed snow can be simulated reasonably well by the model, but not without making several assumptions about the ice particle concentration and the relative role of deposition and aggregation. In conclusion, this suggests that in situ observations of key ice properties are needed to complement the profiling radar observations before process-oriented studies can effectively evaluate ice microphysical parameterizations.

  12. Fingerprints of a riming event on cloud radar Doppler spectra: observations and modeling

    NASA Astrophysics Data System (ADS)

    Kalesse, Heike; Szyrmer, Wanda; Kneifel, Stefan; Kollias, Pavlos; Luke, Edward

    2016-03-01

    Radar Doppler spectra measurements are exploited to study a riming event when precipitating ice from a seeder cloud sediment through a supercooled liquid water (SLW) layer. The focus is on the "golden sample" case study for this type of analysis based on observations collected during the deployment of the Atmospheric Radiation Measurement Program's (ARM) mobile facility AMF2 at Hyytiälä, Finland, during the Biogenic Aerosols - Effects on Clouds and Climate (BAECC) field campaign. The presented analysis of the height evolution of the radar Doppler spectra is a state-of-the-art retrieval with profiling cloud radars in SLW layers beyond the traditional use of spectral moments. Dynamical effects are considered by following the particle population evolution along slanted tracks that are caused by horizontal advection of the cloud under wind shear conditions. In the SLW layer, the identified liquid peak is used as an air motion tracer to correct the Doppler spectra for vertical air motion and the ice peak is used to study the radar profiles of rimed particles. A 1-D steady-state bin microphysical model is constrained using the SLW and air motion profiles and cloud top radar observations. The observed radar moment profiles of the rimed snow can be simulated reasonably well by the model, but not without making several assumptions about the ice particle concentration and the relative role of deposition and aggregation. This suggests that in situ observations of key ice properties are needed to complement the profiling radar observations before process-oriented studies can effectively evaluate ice microphysical parameterizations.

  13. Fingerprints of a riming event on cloud radar Doppler spectra: observations and modeling

    DOE PAGES

    Kalesse, Heike; Szyrmer, Wanda; Kneifel, Stefan; ...

    2016-03-09

    In this paper, Radar Doppler spectra measurements are exploited to study a riming event when precipitating ice from a seeder cloud sediment through a supercooled liquid water (SLW) layer. The focus is on the "golden sample" case study for this type of analysis based on observations collected during the deployment of the Atmospheric Radiation Measurement Program's (ARM) mobile facility AMF2 at Hyytiälä, Finland, during the Biogenic Aerosols – Effects on Clouds and Climate (BAECC) field campaign. The presented analysis of the height evolution of the radar Doppler spectra is a state-of-the-art retrieval with profiling cloud radars in SLW layers beyondmore » the traditional use of spectral moments. Dynamical effects are considered by following the particle population evolution along slanted tracks that are caused by horizontal advection of the cloud under wind shear conditions. In the SLW layer, the identified liquid peak is used as an air motion tracer to correct the Doppler spectra for vertical air motion and the ice peak is used to study the radar profiles of rimed particles. A 1-D steady-state bin microphysical model is constrained using the SLW and air motion profiles and cloud top radar observations. The observed radar moment profiles of the rimed snow can be simulated reasonably well by the model, but not without making several assumptions about the ice particle concentration and the relative role of deposition and aggregation. In conclusion, this suggests that in situ observations of key ice properties are needed to complement the profiling radar observations before process-oriented studies can effectively evaluate ice microphysical parameterizations.« less

  14. Plasma-wave observations at Uranus from Voyager 2. Progress report for period ending February 1986

    SciTech Connect

    Gurnett, D.A.; Kurth, W.S.; Scarf, F.L.; Poynter, R.L.

    1986-03-26

    Radio emissions from Uranus were detected by the Voyager 2 plasma-wave instrument about 5 days before closest approach at frequencies of 31.1 and 56.2 khz. The bow shock was identified by an abrupt broadband burst of electrostatic turbulence about 10 hours before closest approach at a radial distance of 23.5 ru. Once inside of the magnetosphere, strong whistler mode hiss and chorus emissions were observed at radial distances less than about 8 R/sub u/, in the same region where the energetic-particle instruments detected intense fluxes of energetic electrons. A variety of other plasma waves, such as (f sub c) electron-cyclotron waves, were also observed in this same region. At the ring plane crossing, the plasma wave instrument detected a large number of impulsive events that are interpreted as impacts of micron-sized dust particles on the spacecraft. The maximum impact rate was about 20 to 30 impacts/sec, and the north-south thickness of the impact region was about 4000 km. This paper presents an overview of the principal results from the plasma-wave instrument, starting with the first detection of radio emissions from Uranus, and ending a few days after closest approach.

  15. POLAR-UVI and other Coordinated Observations of a Traveling Convection Vortex Event Observed on 24 July 1996

    NASA Technical Reports Server (NTRS)

    Clauer, C. R.; Baker, J. B.; Ridley, A. J.; Sitar, R. J.; Papitashvili, V. O.; Cumnock, J.; Spann, J. F., Jr.; Brittnacher, M. J.; Parks, G. K.

    1997-01-01

    Coordinated analysis of data from the POLAR UVI instrument, ground magnetometers, incoherent scatter radar, solar wind monitors IMP-8 and WIND, and DMSP satellite is focused on a traveling convection vortex (TCV) event on 24 July 1966. Starting at 10:48 UT, ground magnetometers in Greenland and eastern Canada measure pulsations consistent with the passing overhead of a series of alternating TCV field-aligned current pairs. Sondrestrom incoherent scatter radar measures strong modulation of the strength and direction of ionospheric plasma flow, The magnetometer pulsations grow in magnitude over the next hour, peaking in intensity at 11:39 UT, at which time the UVI instrument measures a localized intensification of auroral emissions over central and western Greenland. Subsequent images show the intensification grow in strength and propagate westward (tailward) until approximately 11:58 UT at which time the emissions fade. These observations are consistent with the westward passage of two pairs of moderately intense TCVs over central Greenland followed by a third very intense TCV pair. The intensification of auroral emissions at 11:39 UT is associated with the trailing vortex of the third TCV pair, thought to be the result of an upward field-aligned current. Measurements of the solar wind suggest that a pressure change may be responsible for triggering the first two pairs of TCVS, and that a subsequent sudden change in orientation of the IMF may have produced the intensification of the third TCV pair and the associated aurora] brightening. DMSP particle data indicate that the TCVs occur on field lines which map to the boundary plasma sheet or outer edge of the low latitude boundary layer.

  16. Investigation of EMIC wave scattering as the cause for the BARREL 17 January 2013 relativistic electron precipitation event: A quantitative comparison of simulation with observations

    SciTech Connect

    Li, Zan; Millan, Robyn M.; Hudson, Mary K.; Woodger, Leslie A.; Smith, David M.; Chen, Yue; Friedel, Reiner; Rodriguez, Juan V.; Engebretson, Mark J.; Goldstein, Jerry; Fennell, Joseph F.; Spence, Harlan E.

    2014-12-23

    Electromagnetic ion cyclotron (EMIC) waves were observed at multiple observatory locations for several hours on 17 January 2013. During the wave activity period, a duskside relativistic electron precipitation (REP) event was observed by one of the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) balloons and was magnetically mapped close to Geostationary Operational Environmental Satellite (GOES) 13. We simulate the relativistic electron pitch angle diffusion caused by gyroresonant interactions with EMIC waves using wave and particle data measured by multiple instruments on board GOES 13 and the Van Allen Probes. We show that the count rate, the energy distribution, and the time variation of the simulated precipitation all agree very well with the balloon observations, suggesting that EMIC wave scattering was likely the cause for the precipitation event. The event reported here is the first balloon REP event with closely conjugate EMIC wave observations, and our study employs the most detailed quantitative analysis on the link of EMIC waves with observed REP to date.

  17. Investigation of EMIC wave scattering as the cause for the BARREL 17 January 2013 relativistic electron precipitation event: A quantitative comparison of simulation with observations

    DOE PAGES

    Li, Zan; Millan, Robyn M.; Hudson, Mary K.; ...

    2014-12-23

    Electromagnetic ion cyclotron (EMIC) waves were observed at multiple observatory locations for several hours on 17 January 2013. During the wave activity period, a duskside relativistic electron precipitation (REP) event was observed by one of the Balloon Array for Radiation belt Relativistic Electron Losses (BARREL) balloons and was magnetically mapped close to Geostationary Operational Environmental Satellite (GOES) 13. We simulate the relativistic electron pitch angle diffusion caused by gyroresonant interactions with EMIC waves using wave and particle data measured by multiple instruments on board GOES 13 and the Van Allen Probes. We show that the count rate, the energy distribution,more » and the time variation of the simulated precipitation all agree very well with the balloon observations, suggesting that EMIC wave scattering was likely the cause for the precipitation event. The event reported here is the first balloon REP event with closely conjugate EMIC wave observations, and our study employs the most detailed quantitative analysis on the link of EMIC waves with observed REP to date.« less

  18. Intercomparison of observations and model aerosol parameters during two Saharan dust events over the southern United Kingdom

    NASA Astrophysics Data System (ADS)

    Buxmann, Joelle; Adam, Mariana; Ordonez, Carlos; Tilbee, Marie; Smyth, Tim; Claxton, Bernard; Sugier, Jacqueline; Agnew, Paul

    2015-04-01

    Saharan desert dust lifted by convection over the hot desert surface can reach high altitudes and be transported over great distances. In the UK, Saharan dust episodes occur several times a year, usually during the spring. Dust lifted by cyclonic circulation is often blown into the Atlantic and transported to the UK. This can result in a rapid degradation of air quality due to the increase in the levels of particulate matter (PM). The ability to model the transport and deposition of dust remains an important challenge in order to characterize different pollution events. We present a comparison of observed Aerosol Optical Depth (AOD) with modelled AOD from the Met Office Air Quality Unified Model (AQUM), performed for two dust events in March 2014 (at 380nm, 440nm, 870nm and 1020nm). The observations are derived from five sun photometers located in the southern UK at Exeter, Cardington, Bayfordbury, Chilbolton, and Plymouth. Correlations are investigated between model column integrated PM2.5 and PM10, and observed fine and coarse mode AOD from AERONET. Vertical profiles of attenuated backscatter and extinction from the Jenoptik Nimbus ceilometers part of the Met Office Laser Cloud Base Recorder (LCBR) network are investigated as well (see also session AS3.17/GI2.2 Lidar and Applications). The Met Office air quality model AQUM is an on-line meteorology, chemistry and aerosol modelling system. It runs at a resolution of 12km over a domain covering the UK and north-western Europe. Atmospheric composition modelling employs two-way coupling between aerosol and chemistry evolution, with explicit modelling of sulphate, nitrate, black carbon, organic carbon, biomass burning and wind-blown mineral dust aerosol components. Both the model and observations show an increase in AOD during the first period from 12 -13 March 2014. For example AOD levels of up to 0.52 for the 380nm channel were recorded by the sun photometer in Exeter. This is relatively high compared to average

  19. High-cadence observations of spicular-type events on the Sun

    NASA Astrophysics Data System (ADS)

    Shetye, J.; Doyle, J. G.; Scullion, E.; Nelson, C. J.; Kuridze, D.; Henriques, V.; Woeger, F.; Ray, T.

    2016-05-01

    Context. Chromospheric observations taken at high-cadence and high-spatial resolution show a range of spicule-like features, including Type-I, Type-II (as well as rapid blue-shifted excursions (RBEs) and rapid red-shifted excursions (RREs) which are thought to be on-disk counterparts of Type-II spicules) and those which seem to appear within a few seconds, which if interpreted as flows would imply mass flow velocities in excess of 1000 km s-1. Aims: This article seeks to quantify and study rapidly appearing spicular-type events. We also compare the multi-object multi-frame blind deconvolution (MOMFBD) and speckle reconstruction techniques to understand if these spicules are more favourably observed using a particular technique. Methods: We use spectral imaging observations taken with the CRisp Imaging SpectroPolarimeter (CRISP) on the Swedish 1-m Solar Telescope. Data was sampled at multiple positions within the Hα line profile for both an on-disk and limb location. Results: The data is host to numerous rapidly appearing features which are observed at different locations within the Hα line profile. The feature's durations vary between 10-20 s and lengths around 3500 km. Sometimes, a time delay in their appearance between the blue and red wings of 3-5 s is evident, whereas, sometimes they are near simultaneous. In some instances, features are observed to fade and then re-emerge at the same location several tens of seconds later. Conclusions: We provide the first statistical analysis of these spicules and suggest that these observations can be interpreted as the line-of-sight (LOS) movement of highly dynamic spicules moving in and out of the narrow 60 mÅ transmission filter that is used to observe in different parts of the Hα line profile. The LOS velocity component of the observed fast chromospheric features, manifested as Doppler shifts, are responsible for their appearance in the red and blue wings of Hα line. Additional work involving data at other

  20. Computed and observed turbulent heat fluxes during an extreme Bora event in the Adriatic using atmosphere-ocean coupling

    NASA Astrophysics Data System (ADS)

    Ličer, Matjaž; Smerkol, Peter; Fettich, Anja; Ravdas, Michalis; Papapostolou, Alexandros; Mantziafou, Anneta; Strajnar, Benedikt; Cedilnik, Jure; Jeromel, Maja; Jerman, Jure; Petan, Sašo; Benetazzo, Alvise; Carniel, Sandro; Malačič, Vlado; Sofianos, Sarantis

    2016-04-01

    We have studied the performances of (a) a two-way coupled atmosphere-ocean modeling system and (b) one-way coupled ocean model (forced by the atmosphere model), as compared to the available in situ measurements during and after a strong Adriatic Bora wind event in February 2012, which led to extreme air-sea interactions. The simulations span the period between January and March 2012. The models used were ALADIN (4.4 km resolution) on the atmosphere side and Adriatic setup of POM (1°/30 × 1°/30 angular resolution) on the ocean side. The atmosphere-ocean coupling was implemented using the OASIS3-MCT model coupling toolkit. Two-way coupling ocean feedback to the atmosphere is limited to sea surface temperature. We have compared modeled atmosphere-ocean fluxes (computed using modified Louis scheme) and sea temperatures from both setups to platform and CTD measurements of fluxes (computed using COARE scheme) and temperatures from three observational platforms (Vida, Paloma, Acqua Alta) in the Northern Adriatic. We show that turbulent fluxes from both setups differ up to 20% during the Bora but not significantly before and after the event. The impact of the coupling on the ocean is significant while the impact on the atmosphere is less pronounced. When compared to observations, two way coupling ocean temperatures exhibit a four times lower RMSE than those from one-way coupled system. Two-way coupling improves sensible heat fluxes at all stations but does not improve latent heat loss.

  1. Deciphering IR Excess Observed by the Spitzer Space Telescope in Short Period Interacting Cataclysmic Binaries

    NASA Astrophysics Data System (ADS)

    Chun, Howard; Brinkworth, Carolyn; Ciardi, David; Hoard, Don; Howell, Steve; Stefaniak, Linda; Thomas, , Beth

    2006-03-01

    During the first year of the Spitzer Space Telescope Observing Program for Students and Teachers, our team observed a small sample of short orbital period interacting white dwarf binaries. Our scientific investigation was aimed at detection and characterization of the low mass, cool, brown dwarf-like mass donors in these systems. We used the Infrared Array Camera to obtain photometric observations of the polars EF Eri, GG Leo, V347 Pav, and RX J0154.0-5947 at 3.6, 4.5, 5.8, and 8.0 microns. In all our targets, we detected excess emission in the 3-8 micron region over that expected from a brown dwarf alone. One of the exciting discoveries we made with our IRAC observations is that the star EF Eri was found to be unexpectedly bright in the mid-IR (compared to its 2MASS magnitudes). This fact highlights an opportunity for us to observe EF Eri with the IRS as a follow-up proposal. EF Eri has a flux level of ~700 ?Jy at 8 microns. Thus, we are asking for time to obtain IRS data for only this star, our brightest source. We plan to obtain SL1 (7.4-14.5 microns) and SL2 (5.2-8.7 microns) spectroscopy only. We know the IRAC fluxes so our integration toies are well constrained and the spectral region covered by SL1, SL2 will yield sufficient S/N to differentiate between cool dust (rising BB like spectrum with PAH and other molecular features allowing us to determine dust size, temperature, and disk extent) and a T type dwarf showing characteristic spectral signatures and a falling Rayleigh-Jeans tail.

  2. Drivers of Alongshore Variable Dune Erosion During a Storm Event: Observations and Modelling

    NASA Astrophysics Data System (ADS)

    Switzer, A.; Gouramanis, C.; Bristow, C. S.; Jankaew, K.; Rubin, C. M.; Lee, Y.; Carson, S.; Pham, D. T.; Ildefonso, S.

    2014-12-01

    Do coastlines have memory? In this study we used a combination of remote sensing, field surveys and Ground Penetrating Radar (GPR) to reconstruct the recovery of beaches at Phra Thong Island, Thailand. The study site was severely impacted by the 2004 Indian Ocean Tsunami. Here we show that within a decade the beaches have completely recovered without any human intervention. We apply GPR to image periods of aggradation, progradation and washover sedimentation and match these with local events including a storm in 2007. At one location the beach has locally prograded at least 10m after partially blocking the mouth of a creek that was reamed out by the retreating tsunami. Here we also used GPR to image the scour and recovery of the coastal system (see figure). The rapid recovery of the barrier beach and local progradation indicate that sediment scoured by the tsunami was not transported far offshore but remained in the littoral zone within reach of fair-weather waves that returned to the beach naturally. In both cases coastal processes have reconstructed the beach-dune system to an almost identical pre-tsunami state in under a decade.

  3. A parameterization of dust emission (PM10) fluxes of dust events observed at Naiman in Inner Mongolia using the monitored tower data

    NASA Astrophysics Data System (ADS)

    Park, Soon-Ung; Ju, Jae-Won; Lee, In-Hye; Joo, Seung Jin

    2016-09-01

    The optimal regression equations for the dust emission flux parameterized with the friction velocity (u*) only, the friction velocity with the threshold friction velocity (u*t) and the friction velocity together with the flux Richardson number (Rf) in the dust source region are derived using the sonic anemometer measured momentum and kinematic heat fluxes at 8 m height and the two-level (3 m and 15 m height) measured PM10 concentrations from a 20-m monitoring tower located at Naiman in the Asian dust source region in China for the period from March 2013 to November 2014. The analysis period is divided into three sub-periods based on the Normalized Difference Vegetation Index (NDVI) to eliminate the effect of vegetation on the dust emission flux. The dust event is identified as a peak half hourly mean dust concentration (PM10) at 3 m height exceeding the sub-period mean dust concentration plus one standard deviation of the sub-period. The total of 317 dust events is identified with the highest number of dust event of 18.8 times a month in summer. The optimal regression equations of the dust emission flux (Fc) for dust events parameterized with u* and Rf are found to simulate quite well the dust emission flux estimated by the observed data at the site for all periods especially for the unstable stratification, suggesting the potential usefulness of these equations parameterized by u* with Rf rather than those by u* only and u* together with u*t for the estimation of the dust emission flux in the Asian dust source region.

  4. Latitudinal variation of perturbation electric fields during magnetically disturbed periods - 1986 Sundial observations and model results

    NASA Technical Reports Server (NTRS)

    Fejer, B. G.; Spiro, R. W.; Wolf, R. A.; Foster, J. C.

    1990-01-01

    F-region incoherent scatter radar drift observations from Millstone Hill and Jicamarca, h-prime F observations from Huancayo, and high latitude ground-magnetometer measurements taken during the Sundial 1986 campaign are used to study the relationship between plasmaspheric electric field perturbations and high latitude currents during disturbed periods. The observations are in good agreement with numerical results from a Rice Covection Model run that involved a sharp increase in the polar cap potential drop followed by a subsequent decrease. The zonal disturbance electric field pattern is latitude independent, and the corresponding amplitudes change approximately as L exp n (where n is about 1.5). The meridional electric field patterns and amplitudes have larger latitudinal variations. The mid-, low, and equatorial electric fields from the Rice Convection Model are in good agreement with previous results from the semianalytic, Senior-Blanc (1987) model. Also discussed are three physical mechanisms (over-shielding, fossil winds, and magnetic reconfiguration) that contribute to the long lasting (1-2 h) equatorial zonal electric field perturbations associated with a sudden northward turning of the IMF. It is predicted that the penetration of high latitude electric fields to low latitudes should, in general, be closely related to the rate of motion of the shielding layer and the equatorward edge of the diffuse aurora.

  5. Pro-Am observations of mutual events between the Galilean satellites during the PHEMU09 campaign from Greece

    NASA Astrophysics Data System (ADS)

    Christou, A. A.; Liakos, A.; Tsamis, V.; Tigani, K.; Farmakopoulos, A.; Douvris, A.

    2011-10-01

    The subject of this presentation is a pro-am collaboration to record a number of mutual events between the Galilean satellites of Jupiter from Greece during the PHEMU09 campaign [1]. It involved four amateur and two professional astronomers observing with both portable and fixed-site instruments equipped with CCD cameras at prime focus. The observations took place between May and August 2009. Observations of 21 events were attempted, resulting in usable lightcurves for 15. This contribution will summarise the scientific rationale for the observations, describe the observations themselves, identify lessons learned and outline plans for the next campaign in 2014-15.

  6. A study on the main periodicities in interplanetary magnetic field Bz component and geomagnetic AE index during HILDCAA events using wavelet analysis

    NASA Astrophysics Data System (ADS)

    Souza, A. M.; Echer, E.; Bolzan, M. J. A.; Hajra, R.

    2016-11-01

    The interplanetary and geomagnetic characteristics of High-Intensity Long-Duration Continuous AE Activity (HILDCAA) events are studied using wavelet analysis technique. The Morlet wavelet transform was applied to the 1 min interplanetary magnetic field (IMF) Bz component and the geomagnetic AE index during HILDCAA events. We have analyzed the AE data for the events occurring between 1975 and 2011, and the IMF Bz data (both in GSE and GSM) for the events between 1995 and 2011. We analyzed the scalograms and the global wavelet spectrum of the parameters. For 50% of all HILDCAA events, the main periodicities of the AE index are generally between 4 and 12 h. For the Bz component, the main periodicities were found to be less than 8 h for 56% of times in GSM system and for 54% of times in GSE system. It is conjectured that the periodicities might be associated with the Alfvén waves which have typical periods between 1 and 10 h. The results are discussed in the light of self organized criticality theory where the physical events have the capacity of releasing a considerable amount of energy in a short interval of time.

  7. Dynamics of the MAP IOP 15 severe Mistral event: Observations and high-resolution numerical simulations

    NASA Astrophysics Data System (ADS)

    Guénard, V.; Drobinski, P.; Caccia, J. L.; Tedeschi, G.; Currier, P.

    2006-04-01

    This paper investigates the fundamental processes involved in a severe Mistral event that occurred during the Mesoscale Alpine Program (from 6 to 9 November 1999). The Mistral refers to a violent north/north-westerly wind blowing in south-eastern France from the Rhône valley to the French Riviera. The study is based on measurements from radiosoundings launched from Lyon and Nîmes and from two UHF wind profilers located near Marseille and Toulon allowing a good description of the flow in the complex terrain formed by the south-western Alps. Observational results are compared with RAMS non-hydrostatic numerical simulations performed with 27 km, 9 km and 3 km nested grids. The numerical simulations capture the flow complexity both upstream of the Alps and in the coastal area affected by the Mistral. They correctly reproduce horizontal wind speeds and directions, vertical velocities, virtual potential temperature and relative humidity documented by the observational network. The simulations are used to point out the main dynamical processes generating the Mistral. It is found that flow splitting around the Alps and around the isolated peaks bordering the south-eastern part of the Rhône valley (Mont Ventoux 1909 m, Massif du Lubéron 1425 m) induces the low-level jet observed near Marseille that lasts for 36 hours. The high-resolution simulation indicates that the transient low-level jet lasting for only 9 hours observed at Toulon is due to a gravity wave breaking over local topography (the Sainte Baume 1147 m) where hydraulic jumps are involved. A mountain wake with two opposite-sign potential-vorticity banners is generated. The mesoscale wake explains the westward progression of the large-scale Alpine wake.

  8. Modeling Seven Years of Event Horizon Telescope Observations with Radiatively Inefficient Accretion Flow Models

    NASA Astrophysics Data System (ADS)

    Broderick, Avery E.; Fish, Vincent L.; Johnson, Michael D.; Rosenfeld, Katherine; Wang, Carlos; Doeleman, Sheperd S.; Akiyama, Kazunori; Johannsen, Tim; Roy, Alan L.

    2016-04-01

    An initial three-station version of the Event Horizon Telescope, a millimeter-wavelength very-long baseline interferometer, has observed Sagittarius A* (Sgr A*) repeatedly from 2007 to 2013, resulting in the measurement of a variety of interferometric quantities. Of particular importance is that there is now a large set of closure phases measured over a number of independent observing epochs. We analyze these observations within the context of a realization of semi-analytic radiatively inefficient disk models, implicated by the low luminosity of Sgr A*. We find a broad consistency among the various observing epochs and between different interferometric data types, with the latter providing significant support for this class of model of Sgr A*. The new data significantly tighten existing constraints on the spin magnitude and its orientation within this model context, finding a spin magnitude of a={0.10}-0.10-0.10+0.30+0.56, an inclination with respect to the line of sight of θ ={60^\\circ }-{8^\\circ -{13}^\\circ }+{5^\\circ +{10}^\\circ }, and a position angle of ξ ={156^\\circ }-{17^\\circ -{27}^\\circ }+{10^\\circ +{14}^\\circ } east of north. These are in good agreement with previous analyses. Notably, the previous 180° degeneracy in the position angle has now been conclusively broken by the inclusion of the closure-phase measurements. A reflection degeneracy in the inclination remains, permitting two localizations of the spin vector orientation, one of which is in agreement with the orbital angular momentum of the infrared gas cloud G2 and the clockwise disk of young stars. This may support a relationship between Sgr A*'s accretion flow and these larger-scale features.

  9. "Radiative Closure Studies for Clear Skies During the ARM 2003 Aerosol Intensive Observation Period"

    SciTech Connect

    J. J. Michalsky, G. P. Anderson, J. Barnard, J. Delamere, C. Gueymard, S. Kato, P. Kiedron, A. McComiskey, and P. Ricchiazzi

    2006-04-01

    The Department of Energy's Atmospheric Radiation Measurement (ARM) program sponsored a large intensive observation period (IOP) to study aerosol during the month of May 2003 around the Southern Great Plains (SGP) Climate Research Facility (CRF) in north central Oklahoma. Redundant measurements of aerosol optical properties were made using different techniques at the surface as well as in vertical profile with sensors aboard two aircraft. One of the principal motivations for this experiment was to resolve the disagreement between models and measurements of diffuse horizontal broadband shortwave irradiance at the surface, especially for modest aerosol loading. This paper focuses on using the redundant aerosol and radiation measurements during this IOP to compare direct beam and diffuse horizontal broadband shortwave irradiance measurements and models at the surface for a wide range of aerosol cases that occurred during 30 clear-sky periods on 13 days of May 2003. Models and measurements are compared over a large range of solar-zenith angles. Six different models are used to assess the relative agreement among them and the measurements. Better agreement than previously achieved appears to be the result of better specification of input parameters and better measurements of irradiances than in prior studies. Biases between modeled and measured direct irradiances are less than 1%, and biases between modeled and measured diffuse irradiances are less than 2%.

  10. Periodic behaviors in the observed vertical column abundances of atmospheric hydroxyl

    NASA Technical Reports Server (NTRS)

    Burnett, Elizabeth Beaver; Burnett, Clyde R.; Minschwaner, Kenneth R.

    1989-01-01

    The data base for the vertical column abundance of atmospheric hydroxyl (OH) for Fritz Peak Observatory, Colorado (40 N, 105 W), now extends from 1976 through 1988 and is composed of 8849 independent data sets, averaging about 15 percent uncertainty and 20-minute time resolution each. The dominant solar zenith angle (chi) dependence of the OH abundance is characterized by an empirical curve, N(88), which has been updated from N(82) to include all valid data from 1980 through 1988. The chi-dependence of the OH abundance has been, to a first order, removed from the data base by a normalization procedure in which each data point is divided by the N(88,AM) value for the corresponding solar zenith angle. The resulting normalized OH values may then be examined for other systematic effects, particularly for periodic variations. Observations have also been made at Boca Raton, Florida (26 N, 80 W) and at Truk, Federated States of Micronesia (7 N, 152 E). These data bases are much less extensive and, as such, are less amenable to analysis for periodic behaviors. Some comparisons with the Colorado data may be made, however.

  11. Observation of stimulated emission in an ultrashort-period nonsymmetric GaAs/AlAs superlattice

    SciTech Connect

    Litovchenko, V. G.; Korbutyak, D. V.; Bercha, A. I.; Kryuchenko, Yu. V.; Krylyuk, S. G.; Grahn, H. T.; Hey, R.; Ploog, K. H.

    2001-06-25

    Nonsymmetric short-period GaAs/AlAs superlattices, for which the well thickness is at least a factor of 2 larger than the barrier thickness, have been shown to exhibit a direct band gap for any well thickness. These superlattices are characterized by an enhanced intensity of the luminescence as compared to their symmetric indirect-gap counterparts with the same well width, and, thus, may be used as light-emitting devices, in particular, as low-threshold lasers in the red visible spectrum. This conjecture is supported by the observation of stimulated emission at T=80K for a GaAs/AlAs superlattice with six monolayers well and three monolayers barrier width. {copyright} 2001 American Institute of Physics.

  12. Cancer incidence among asbestos-exposed chemical industry workers: An extended observation period

    SciTech Connect

    Hilt, B.; Andersen, A.; Rosenberg, J.; Langard, S. )

    1991-01-01

    A previous study on the incidence of cancer in a cohort of 286 asbestos-exposed electrochemical industry workers observed from 1953 through 1980 has been extended with another 8 years of follow-up. The incidence of cancer was derived from the Cancer Registry of Norway, and the expected figures were calculated by a life table method. During the extended follow-up period from 1981 through 1988, among the cohort members there were 12 new cancer cases versus 14.2 expected (SIR 85, 95% CI 44-158). In a lightly exposed sub-cohort, the extended follow-up revealed 4 cases of lung cancer or pleural mesothelioma (ICD, 7th revision 162-163) versus 1.6 cases expected (SIR 256, 95% CI71-654). In a heavily exposed sub-cohort, the corresponding figures were 3 and 0.5 (SIR 588, 95% CI 118-1,725).

  13. Observation of Exchange Anisotropy in Single-Phase Layer-Structured Oxides with Long Periods

    PubMed Central

    Huang, Yan; Wang, Guopeng; Sun, Shujie; Wang, Jianlin; Peng, Ranran; Lin, Yue; Zhai, Xiaofang; Fu, Zhengping; Lu, Yalin

    2015-01-01

    A remarkable exchange bias effect arising from the temperature-dependent interaction among the ferromagnetic-like cluster glasses and antiferromagnetic regions was observed in a newly developed single-phase multiferroic compound of Bi10Fe6Ti3O30 which has a nine-layer Aurivillius structure. Inhomogeneous distribution of magnetic Fe ions inside this long-period layered structure was experimentally identified via the atomic level imaging. The results confirmed the presence of the short-range magnetic ordering (the cluster glassy state) and the canted antiferromagnetism, and then the direct interaction among them was further confirmed. Finding of this new single-phase material accompanying this remarkable exchange bias effect would be beneficial to both basic physics understanding and the potential device development. PMID:26487509

  14. Evaporation over land surfaces - First results from HAPEX-MOBILHY Special Observing Period

    NASA Technical Reports Server (NTRS)

    Andre, Jean-Claude; Goutorbe, Jean-Paul; Bessemoulin, Pierre; Perrier, Alain; Becker, Francois

    1988-01-01

    Preliminary results are presented from the May 7-July 15, 1986 Special Observing Period (SOP) of the HAPEX-MOBILHY program, which examines the hydrological budget and evaporation flux at the scale of a 10,000 sq km GCM grid square to determine soil moisture, surface-energy budgets, and surface hydrology. The SOP used two highly instrumented remote sensing aircraft to obtain detailed measurements of atmospheric fluxes and surface properties. It is noted that the measurements are reliable at spatially local and short time scales, as well as on the monthly time scale. The data base obtained may be used in parametrization schemes against which land-surface water budgets can be tested.

  15. Lidar observation of Asian dust events during the ACE-Asia 2001 IOP at Gosan, Jeju Island, Korea

    NASA Astrophysics Data System (ADS)

    Hong, Chun Sang; Lee, Kwon Ho; Kim, Young Joon; Kim, Sang Woo; Won, Jae Gwang; Yoon, Soon Chang; Iwasaka, Yasunobu

    2003-12-01

    In general Asian dust storms occurring during the spring season in the northeast Asia play an important role in radiative forcing and regional climate change. In order to investigate the characteristic of optical properties of Asian dust particles atmospheric aerosol vertical profile was measured with a multi-wavelength LIDAR system developed by ADEMRC, K-JIST and a collocated micro-pulse LIDAR (MPL) during the ACE-Asia intensive observation period, 11 March ~ 4 May 2001 at the Gosan super site (33°17'N, 126°10'E) in Jeju Island, Korea. Air mass backward trajectory analysis shows that air masses came from either the northwestern Chinese desert regions or northeastern Chinese sandy areas. It has been shown that combining the LIDAR data and back trajectory analysis can assess the transport characteristics of atmospheric aerosol during the Asian dust events. The LIDAR-derived aerosol optical depth values were compared with those measured by a collocated AERONET sun photometer. Relationship between the LIDAR data and chemical data of atmospheric particulate matters observed at the surface has been analyzed.

  16. Prior event rate ratio adjustment for hidden confounding in observational studies of treatment effectiveness: a pairwise Cox likelihood approach.

    PubMed

    Lin, Nan Xuan; Henley, William Edward

    2016-12-10

    Observational studies provide a rich source of information for assessing effectiveness of treatment interventions in many situations where it is not ethical or practical to perform randomized controlled trials. However, such studies are prone to bias from hidden (unmeasured) confounding. A promising approach to identifying and reducing the impact of unmeasured confounding is prior event rate ratio (PERR) adjustment, a quasi-experimental analytic method proposed in the context of electronic medical record database studies. In this paper, we present a statistical framework for using a pairwise approach to PERR adjustment that removes bias inherent in the original PERR method. A flexible pairwise Cox likelihood function is derived and used to demonstrate the consistency of the simple and convenient alternative PERR (PERR-ALT) estimator. We show how to estimate standard errors and confidence intervals for treatment effect estimates based on the observed information and provide R code to illustrate how to implement the method. Assumptions required for the pairwise approach (as well as PERR) are clarified, and the consequences of model misspecification are explored. Our results confirm the need for researchers to consider carefully the suitability of the method in the context of each problem. Extensions of the pairwise likelihood to more complex designs involving time-varying covariates or more than two periods are considered. We illustrate the application of the method using data from a longitudinal cohort study of enzyme replacement therapy for lysosomal storage disorders. © 2016 The Authors. Statistics in Medicine Published by John Wiley & Sons Ltd.

  17. Observing and Modeling the Optical Counterparts of Short-Period Binary Millisecond Pulsars

    NASA Astrophysics Data System (ADS)

    Schroeder, Joshua

    In this dissertation, I explore the subject of short-period binary millisecond pulsars discovered by the Fermi Gamma-ray Space Telescope and radio follow-up teams, and present observations of fields containing eight recently discovered short-period (Porb < 1 d) binary millisecond pulsars using the telescopes at MDM Observatory. The goal of these observations was to detect the optical counterparts of the binaries and, for the best-suited counterparts detected, to observe the photometric variation of the companion that happens over the course of the orbit in various filters. The hope was to then use the light curves to model the systems and obtain constraints on the mass of the neutron stars which are likely to be some of the most massive neutron stars in the galaxy. Optical counterparts to four of these systems are detected, one of which, PSR J2214+3000, is a novel detection. Additionally, I present the fully orbital phase-resolved B, V , and R light curves of the optical counterparts to two objects, PSR J1810+1744 and PSR J2215+5135, for which I employ the ELC model of Orosz & Hauschildt (2000) to measure the unknown system parameters. For PSR J1810+1744 I find that the system parameters cannot be fit even assuming that 100% of the spin-down luminosity of the pulsar is irradiating the secondary, and so radial velocity measurements of this object will be required for the complete solution. However, PSR J2215+5135 exhibits light curves that are extremely well constrained using the ELC model and we find that the mass of the neutron star is constrained by these and the radio observations to be MNS > 1.75 solar masses; at the 3-sigma level. I also find a discrepancy between the model temperature and the measured colors of this object which I interpret as possible evidence for an additional high-temperature source such as a quiescent disk. Given this and the fact that PSR J2215+5135 contains a relatively high mass companion (Mc > 0.1 solar masses), I propose that similar

  18. Global MHD predictions of observational signatures of subsolar Flux Transfer Events

    NASA Astrophysics Data System (ADS)

    Dorelli, J.; Glocer, A.

    2012-12-01

    Previous global MHD simulations of Flux Transfer Events demonstrate that they are topologically complex flux ropes that form at the subsolar magnetopause before being blown toward one of the polar cusps by the magnetosheath flow. However, different simulations -- run under different conditions -- seem to show evidence for qualitatively different generation mechanisms. For example, Raeder [2006] used the OpenGGCM code to argue that FTEs form as a result of a "sequential X line" mechanism in which non-vanishing dipole tilt causes the stagnation point to separate from a pre-existing X line. Numerical reconnection then caused a second X line to form, resulting in the creation of a simple "O-type" magnetic structure that Raeder identified as a Flux Transfer Event. FTEs were not observed under zero dipole tilt conditions. In contrast, Dorelli and Bhattacharjee [2009] ran higher resolution OpenGGCM simulations with constant but high Lundquist number (large enough to produce a resolved thin current sheet at the subsolar magnetopause) and demonstrated that dipole tilt is not required to generate FTEs. While the local magnetic field geometry (projected into a 2D plane) was simple, consisting of an O-type projected magnetic null bounded by two X-type nulls (consistent with what Raeder [2006] saw), new 3D X lines did not form until the FTE generation process was well underway. Further, the FTE topology was observed to be complex, with multiple (more than 2) 3D X lines forming at the subsolar magnetopause during the generation process. In this talk, we revisit the question of FTE generation using the BATS-R-US global MHD code. Our goals are: 1) to determine whether BATS-R-US can produce FTEs under conditions similar to those for which they were seen by OpenGGCM, 2) to explore the role of dipole tilt and the resistivity model in FTE generation, and 3) to generate a list of observable predictions of FTEs as they form near the subsolar magnetopause.

  19. An overview of the lightning and atmospheric electricity observations collected in southern France during the HYdrological cycle in Mediterranean EXperiment (HyMeX), Special Observation Period 1

    NASA Astrophysics Data System (ADS)

    Defer, E.; Pinty, J.-P.; Coquillat, S.; Martin, J.-M.; Prieur, S.; Soula, S.; Richard, E.; Rison, W.; Krehbiel, P.; Thomas, R.; Rodeheffer, D.; Vergeiner, C.; Malaterre, F.; Pedeboy, S.; Schulz, W.; Farges, T.; Gallin, L.-J.; Ortéga, P.; Ribaud, J.-F.; Anderson, G.; Betz, H.-D.; Meneux, B.; Kotroni, V.; Lagouvardos, K.; Roos, S.; Ducrocq, V.; Roussot, O.; Labatut, L.; Molinié, G.

    2015-02-01

    The PEACH project (Projet en Electricité Atmosphérique pour la Campagne HyMeX - the Atmospheric Electricity Project of the HyMeX Program) is the atmospheric electricity component of the Hydrology cycle in the Mediterranean Experiment (HyMeX) experiment and is dedicated to the observation of both lightning activity and electrical state of continental and maritime thunderstorms in the area of the Mediterranean Sea. During the HyMeX SOP1 (Special Observation Period) from 5 September to 6 November 2012, four European operational lightning locating systems (ATDnet, EUCLID, LINET, ZEUS) and the HyMeX lightning mapping array network (HyLMA) were used to locate and characterize the lightning activity over the northwestern Mediterranean at flash, storm and regional scales. Additional research instruments like slow antennas, video cameras, microbarometer and microphone arrays were also operated. All these observations in conjunction with operational/research ground-based and airborne radars, rain gauges and in situ microphysical records are aimed at characterizing and understanding electrically active and highly precipitating events over southeastern France that often lead to severe flash floods. Simulations performed with cloud resolving models like Meso-NH and Weather Research and Forecasting are used to interpret the results and to investigate further the links between dynamics, microphysics, electrification and lightning occurrence. Herein we present an overview of the PEACH project and its different instruments. Examples are discussed to illustrate the comprehensive and unique lightning data set, from radio frequency to acoustics, collected during the SOP1 for lightning phenomenology understanding, instrumentation validation, storm characterization and modeling.

  20. Changes in ENACW observed in the Bay of Biscay over the period 1975-2010

    NASA Astrophysics Data System (ADS)

    Gómez-Gesteira, M.; deCastro, M.; Santos, F.; Álvarez, I.; Costoya, X.

    2013-08-01

    Trends in Eastern North Atlantic Central Water (ENACW) were calculated in the Bay of Biscay over the period 1975-2010 using the Simple Ocean Data Assimilation (SODA) package. This approach, which reanalyzes data from different sources, allows obtaining information beneath the sea surface on a fine 0.5°×0.5° grid with 40 vertical layers, providing a complete view of the different hydrographic processes in the area. ENACW, which was associated to salinity and temperature values corresponding to the density interval 27.0-27.2 kg m-3, was observed to warm and salinificate in most of the area at a maximum rate of 0.11 °C per decade and 0.03 psu per decade, respectively. Trends are more intense in the middle part of the Bay and near the northeastern boundary. The origin of the changes in ENACW observed inside the Bay of Biscay is not due to local effects. Actually, trends seem to be related to changes in the subpolar mode of ENACW (ENACWsp), affecting a wider North Atlantic area. The highest trends (0.3 °C per decade in temperature and 0.05 psu per decade in salinity) were observed north of the bay, especially at the shallow area that stretches from Brest to Ireland, which is characterized by deep winter mixing. The dependence of changes in ENACW on the two main modes of variability over the North Atlantic (NAO and EA) was also analyzed. Trends in salinity and temperature showed to be consistent with changes observed in EA. In addition, air temperature and precipitation minus evaporation (P-E) balance showed to contribute to warming and salinification of ENACW.

  1. Sequential Window Diagnoser for Discrete-Event Systems Under Unreliable Observations

    SciTech Connect

    Wen-Chiao Lin; Humberto E. Garcia; David Thorsley; Tae-Sic Yoo

    2009-09-01

    This paper addresses the issue of counting the occurrence of special events in the framework of partiallyobserved discrete-event dynamical systems (DEDS). Developed diagnosers referred to as sequential window diagnosers (SWDs) utilize the stochastic diagnoser probability transition matrices developed in [9] along with a resetting mechanism that allows on-line monitoring of special event occurrences. To illustrate their performance, the SWDs are applied to detect and count the occurrence of special events in a particular DEDS. Results show that SWDs are able to accurately track the number of times special events occur.

  2. An integrated approach for identifying homogeneous regions of extreme rainfall events and estimating IDF curves in Southern Ontario, Canada: Incorporating radar observations

    NASA Astrophysics Data System (ADS)

    Paixao, Edson; Mirza, M. Monirul Qader; Shephard, Mark W.; Auld, Heather; Klaassen, Joan; Smith, Graham

    2015-09-01

    Reliable extreme rainfall information is required for many applications including infrastructure design, management of water resources, and planning for weather-related emergencies in urban and rural areas. In this study, in situ TBRG sub-daily rainfall rate observations have been supplemented with weather radar information to better capture the spatial and temporal variability of heavy rainfall events regionally. Comparison of extreme rainfall events show that the absolute differences between the rain gauge and radar generally increase with increasing rainfall. Better agreement between the two observations is found when comparing the collocated radar and TBRG annual maximum values. The median difference is <18% for the annual maximum rainfall values ⩽50 mm. The median of difference of IDF estimates obtained through the Gumbel distribution for 10-year return period values computed from TBRG and radar are also found to be 4%. The overall results of this analysis demonstrates the potential value of incorporating remotely sensed radar with traditional point source TBRG network observations to provide additional insight on extreme rainfall events regionally, especially in terms of identifying homogeneous regions of extreme rainfall. The radar observations are particularly useful in areas where there is insufficient TBRG station density to statistically capture the extreme rainfall events.

  3. Co-design of H∞ jump observers for event-based measurements over networks

    NASA Astrophysics Data System (ADS)

    Peñarrocha, Ignacio; Dolz, Daniel; Romero, Julio Ariel; Sanchis, Roberto

    2016-01-01

    This work presents a strategy to minimise the network usage and the energy consumption of wireless battery-powered sensors in the observer problem over networks. The sensor nodes implement a periodic send-on-delta approach, sending new measurements when a measure deviates considerably from the previous sent one. The estimator node implements a jump observer whose gains are computed offline and depend on the combination of available new measurements. We bound the estimator performance as a function of the sending policies and then state the design procedure of the observer under fixed sending thresholds as a semidefinite programming problem. We address this problem first in a deterministic way and, to reduce conservativeness, in a stochastic one after obtaining bounds on the probabilities of having new measurements and applying robust optimisation problem over the possible probabilities using sum of squares decomposition. We relate the network usage with the sending thresholds and propose an iterative procedure for the design of those thresholds, minimising the network usage while guaranteeing a prescribed estimation performance. Simulation results and experimental analysis show the validity of the proposal and the reduction of network resources that can be achieved with the stochastic approach.

  4. Suzaku And Multi-Wavelength Observations of OJ 287 During the Periodic Optical Outburst in 2007

    SciTech Connect

    Seta, Hiromi; Isobe, N.; Tashiro, Makoto S.; Yaji, Yuichi; Arai, Akira; Fukuhara, Masayuki; Kohno, Kotaro; Nakanishi, Koichiro; Sasada, Mahito; Shimajiri, Yoshito; Tosaki, Tomoka; Uemura, Makoto; Anderhub, Hans; Antonelli, L.A.; Antoranz, Pedro; Backes, Michael; Baixeras, Carmen; Balestra, Silvia; Barrio, Juan Abel; Bastieri, Denis; Becerra Gonzalez, Josefa; /IAC, La Laguna /Dortmund U. /Lodz U. /Lodz U. /DESY /Zurich, ETH /Munich, Max Planck Inst. /Padua U. /INFN, Padua /Siena U. /INFN, Siena /Barcelona, IEEC /Munich, Max Planck Inst. /Barcelona, IEEC /Madrid U. /Zurich, ETH /Wurzburg U. /Zurich, ETH /Madrid U. /Munich, Max Planck Inst. /Zurich, ETH /Madrid U. /Barcelona, IFAE /IAC, La Laguna /Laguna U., Tenerife /INFN, Rome /Dortmund U. /Udine U. /INFN, Udine /INFN, Padua /Udine U. /INFN, Udine /Barcelona, IEEC /Madrid U. /Udine U. /INFN, Udine /Udine U. /INFN, Udine /Udine U. /INFN, Udine /IAC, La Laguna /Madrid, CIEMAT /Sierra Nevada Observ. /Zurich, ETH /Padua U. /INFN, Padua /Wurzburg U. /Barcelona, IFAE /UC, Davis /Barcelona, IFAE /Barcelona, IFAE /Madrid U. /Barcelona, Autonoma U. /Munich, Max Planck Inst. /IAC, La Laguna /Laguna U., Tenerife /Barcelona, IFAE /IAC, La Laguna /Munich, Max Planck Inst. /Barcelona, Autonoma U. /Munich, Max Planck Inst. /SLAC /IAC, La Laguna /Laguna U., Tenerife /Zurich, ETH /Wurzburg U. /Munich, Max Planck Inst. /Munich, Max Planck Inst. /Munich, Max Planck Inst. /Zurich, ETH /INFN, Rome /UC, Davis /Siena U. /INFN, Siena /Turku U. /Padua U. /INFN, Padua /Udine U. /INFN, Udine /Padua U. /INFN, Padua /Zurich, ETH /Munich, Max Planck Inst. /DESY /Sofiya, Inst. Nucl. Res. /Udine U. /INFN, Udine /Wurzburg U. /INFN, Rome /Padua U. /INFN, Padua /Barcelona, IFAE /Barcelona, IFAE /Siena U. /INFN, Siena /Wurzburg U. /Madrid U. /Munich, Max Planck Inst. /Munich, Max Planck Inst. /Barcelona, IEEC /Sierra Nevada Observ. /Barcelona, IFAE /Madrid U. /Turku U. /Munich, Max Planck Inst. /Munich, Max Planck Inst. /UC, Santa Cruz /Madrid U. /Siena U. /INFN, Siena /Barcelona, IEEC /Turku U. /Padua U. /INFN, Padua /Zurich, ETH /Siena U. /INFN, Siena /Sierra Nevada Observ. /Udine U. /INFN, Udine /INFN, Trieste /Padua U. /INFN, Padua /Sierra Nevada Observ. /Padua U. /INFN, Padua /Barcelona, IFAE /Barcelona, IFAE /Dortmund U. /Barcelona, IEEC /ICREA, Barcelona /Barcelona, IFAE /Zurich, ETH /Barcelona, Autonoma U. /Wurzburg U. /Padua U. /INFN, Padua /Munich, Max Planck Inst. /INFN, Rome /Sierra Nevada Observ. /DESY /Padua U. /INFN, Padua /Udine U. /INFN, Udine /Munich, Max Planck Inst. /Munich, Max Planck Inst. /Pisa U. /INFN, Pisa /Barcelona, IFAE /Barcelona, IEEC /Turku U. /Munich, Max Planck Inst. /Lodz U. /Lodz U. /Wurzburg U. /Siena U. /INFN, Siena /Zurich, ETH /Turku U. /INFN, Rome /Sofiya, Inst. Nucl. Res. /Barcelona, IFAE /Munich, Max Planck Inst. /DESY /ICREA, Barcelona /Barcelona, IEEC /Siena U. /INFN, Siena /Sofiya, Inst. Nucl. Res. /Munich, Max Planck Inst. /Munich, Max Planck Inst. /Barcelona, IEEC /Sierra Nevada Observ. /Barcelona, IFAE /Barcelona, Autonoma U.

    2011-12-01

    Suzaku observations of the blazar OJ 287 were performed in 2007 April 10-13 and November 7-9. They correspond to a quiescent and a flaring state, respectively. The X-ray spectra of the source can be well described with single power-law models in both exposures. The derived X-ray photon index and the flux density at 1 keV were found to be {Lambda} = 1.65 {+-} 0.02 and S{sub 1keV} = 215 {+-} 5 nJy, in the quiescent state. In the flaring state, the source exhibited a harder X-ray spectrum ({Lambda} = 1.50 {+-} 0.01) with a nearly doubled X-ray flux density S{sub 1keV} = 404{sub -5}{sup +6} nJy. Moreover, significant hard X-ray signals were detected up to {approx} 27 keV. In cooperation with the Suzaku, simultaneous radio, optical, and very-high-energy {gamma}-ray observations of OJ 287 were performed with the Nobeyama Millimeter Array, the KANATA telescope, and the MAGIC telescope, respectively. The radio and optical fluxes in the flaring state (3.04 {+-} 0.46 Jy and 8.93 {+-} 0.05 mJy at 86.75 Hz and in the V-band, respectively) were found to be higher by a factor of 2-3 than those in the quiescent state (1.73 {+-} 0.26 Jy and 3.03 {+-} 0.01 mJy at 86.75 Hz and in the V-band, respectively). No notable {gamma}-ray events were detected in either observation. The spectral energy distribution of OJ 287 indicated that the X-ray spectrum was dominated by inverse Compton radiation in both observations, while synchrotron radiation exhibited a spectral cutoff around the optical frequency. Furthermore, no significant difference in the synchrotron cutoff frequency was found between the quiescent and flaring states. According to a simple synchrotron self-Compton model, the change of the spectral energy distribution is due to an increase in the energy density of electrons with small changes of both the magnetic field strength and the maximum Lorentz factor of electrons.

  5. Evolution and characterization of drought events from GRACE and other satellite and observation.

    NASA Astrophysics Data System (ADS)

    Zhao, M.; A, G.; Velicogna, I.; Kimball, J. S.

    2015-12-01

    We use GRACE Terrestrial Water Storage (TWS) changes to calculate a newly developed global drought severity index (GRACE-DSI) for monthly monitoring of water supply changes during 2002-2015. We compare GRACE-DSI with Palmer Drought Severity Index (PDSI) and other ancillary data to characterize drought timing, evolution and magnitude in the continental US since 2002. Overall GRACE-DSI and PDSI show an excellent correspondence in the US. However PDSI is very sensitive to atmospheric moisture stress, while GRACE-DSI only responds to changes in terrestrial water storage. We use the complementary nature of these two indices together with temperature and precipitation observations to characterize drought evolution and its nature. For instance, during the 2012 flash drought in the Great Plains, the PDSI decreases several months earlier than the GRACE-DSI in response to the enhanced atmosphere moisture demand caused by unusual early season warming. When the drought peaks later in the summer, the PDSI indicates exceptional drought, while the GRACE-DSI observes moderate drought conditions in the underlying total water supply, implying a meteorological drought in nature. GRACE-DSI is based solely on satellite observations; hence it has the advantage of not being affected by uncertainty associated with variable that are not well known at the global scale (e.g. precipitation estimates) and by biases associated to global climate model outputs. We find that GRACE-DSI captures major drought events in the globe occurring during 2002-2015, including those in sub-Sahara Africa, Australia, Amazon, Asia, North America and the Arctic.

  6. Airborne observations of new particle formation events in the boundary layer using a Zeppelin

    NASA Astrophysics Data System (ADS)

    Lampilahti, Janne; Manninen, Hanna E.; Nieminen, Tuomo; Mirme, Sander; Pullinen, Iida; Yli-Juuti, Taina; Schobesberger, Siegfried; Kangasluoma, Juha; Kontkanen, Jenni; Lehtipalo, Katrianne; Ehn, Mikael; Mentel, Thomas F.; Petäjä, Tuukka; Kulmala, Markku

    2014-05-01

    Atmospheric new particle formation (NPF) is a frequent and ubiquitous process in the atmosphere and a major source of newly formed aerosol particles [1]. However, it is still unclear how the aerosol particle distribution evolves in space and time during an NPF. We investigated where in the planetary boundary layer does NPF begin and how does the aerosol number size distribution develop in space and time during it. We measured in Hyytiälä, southern Finland using ground based and airborne measurements. The measurements were part of the PEGASOS project. NPF was studied on six scientific flights during spring 2013 using a Zeppelin NT class airship. Ground based measurements were simultaneously conducted at SMEAR II station located in Hyytiälä. The flight profiles over Hyytiälä were flown between sunrise and noon during the growth of the boundary layer. The profiles over Hyytiälä covered vertically a distance of 100-1000 meters reaching the mixed layer, stable (nocturnal) boundary layer and the residual layer. Horizontally the profiles covered approximately a circular area of four kilometers in diameter. The measurements include particle number size distribution by Neutral cluster and Air Ion Spectrometer (NAIS), Differential Mobility Particle Sizer (DMPS) and Particle Size Magnifier (PSM) [2], meteorological parameters and position (latitude, longitude and altitude) of the Zeppelin. Beginning of NPF was determined from an increase in 1.7-3 nm ion concentration. Height of the mixed layer was estimated from relative humidity measured on-board the Zeppelin. Particle growth rate during NPF was calculated. Spatial inhomogeneities in particle number size distribution during NPF were located and the birthplace of the particles was estimated using the growth rate and trajectories. We observed a regional NPF event that began simultaneously and evolved uniformly inside the mixed layer. In the horizontal direction we observed a long and narrow high concentration plume of

  7. Analysis of the observed and forecast rainfall intensity structure in a precipitation event

    NASA Astrophysics Data System (ADS)

    Bech, Joan; Molinié, Gilles; Karakasidis, Theodoros; Anquentin, Sandrine; Creutin, Jean Dominique; Pinty, Jean-Pierre; Escobar, Juan

    2014-05-01

    During the last decades a number of studies have been devoted to examine the precipitation field temporal and spatial structure, given the fact that rainfall exhibits large variability at all scales (see for example Ceresetti et al. 2011, 2012). The objective of this study is to examine the rainfall field structure at high temporal (15 minute) and spatial (1 km) resolution. We focus on rainfall properties such as the intermittency using the auto-correlation of precipitation time series to assess if it can be modelled assuming a fractal behaviour and considering different scales. Based on the results and methodology used in previous studies applied to observational precipitation data such as raingauge, weather radar and disdrometer observations (see for example Molinié et al., 2011, 2013), in this case we employ high resolution numerical forecast data. In particular our approach considers using a transitive covariogram, given the limited number of samples available in single precipitation events. Precipitation forecasts are derived at 15 minute intervals from 1-km grid length nested simulations of the non-hydrostatic mesoscale atmospheric model of the French research community Meso-NH, using AROME-WestMed model data as initial and boundary conditions. The analysis also considers existing data available in the Hymex (HYdrological cycle in the Mediterranean EXperiment) data base. Results are presented of a precipitation event that took place in the Rhône Valley (France) in November 2011. This case allows to study with the proposed methodology the effect of a number of factors (different orography along the Rhône Valley, turbulence, microphysical processes, etc.) on the observed and simulated precipitation field. References Ceresetti D., E. Ursu, J. Carreau, S. Anquetin, J. D. Creutin, L. Gardes, S. Girard, and G. Molinié, 2012: Evaluation of classical spatial-analysis schemes of extreme rainfall. Natural Hazards and Earth System Sciences, 12, 3229-3240, http

  8. Observation of Geometric Parametric Instability Induced by the Periodic Spatial Self-Imaging of Multimode Waves

    NASA Astrophysics Data System (ADS)

    Krupa, Katarzyna; Tonello, Alessandro; Barthélémy, Alain; Couderc, Vincent; Shalaby, Badr Mohamed; Bendahmane, Abdelkrim; Millot, Guy; Wabnitz, Stefan

    2016-05-01

    Spatiotemporal mode coupling in highly multimode physical systems permits new routes for exploring complex instabilities and forming coherent wave structures. We present here the first experimental demonstration of multiple geometric parametric instability sidebands, generated in the frequency domain through resonant space-time coupling, owing to the natural periodic spatial self-imaging of a multimode quasi-continuous-wave beam in a standard graded-index multimode fiber. The input beam was launched in the fiber by means of an amplified microchip laser emitting sub-ns pulses at 1064 nm. The experimentally observed frequency spacing among sidebands agrees well with analytical predictions and numerical simulations. The first-order peaks are located at the considerably large detuning of 123.5 THz from the pump. These results open the remarkable possibility to convert a near-infrared laser directly into a broad spectral range spanning visible and infrared wavelengths, by means of a single resonant parametric nonlinear effect occurring in the normal dispersion regime. As further evidence of our strong space-time coupling regime, we observed the striking effect that all of the different sideband peaks were carried by a well-defined and stable bell-shaped spatial profile.

  9. Quasi-periodic variations in x-ray emission and long-term radio observations: Evidence for a two-component jet in Sw J1644+57

    SciTech Connect

    Wang, Jiu-Zhou; Lei, Wei-Hua; Wang, Ding-Xiong; Zou, Yuan-Chuan; Huang, Chang-Yin; Zhang, Bing; Gao, He E-mail: dxwang@hust.edu.cn E-mail: zhang@physics.unlv.edu

    2014-06-10

    The continued observations of Sw J1644+57 in X-ray and radio bands accumulated a rich data set to study the relativistic jet launched in this tidal disruption event. The X-ray light curve of Sw J1644+57 from 5-30 days presents two kinds of quasi-periodic variations: a 200 s quasi-periodic oscillation (QPO) and a 2.7 day quasi-periodic variation. The latter has been interpreted by a precessing jet launched near the Bardeen-Petterson radius of a warped disk. Here we suggest that the ∼200 s QPO could be associated with a second, narrower jet sweeping the observer line-of-sight periodically, which is launched from a spinning black hole in the misaligned direction with respect to the black hole's angular momentum. In addition, we show that this two-component jet model can interpret the radio light curve of the event, especially the re-brightening feature starting ∼100 days after the trigger. From the data we infer that inner jet may have a Lorentz factor of Γ{sub j} ∼ 5.5 and a kinetic energy of E {sub k,} {sub iso} ∼ 3.0 × 10{sup 52} erg, while the outer jet may have a Lorentz factor of Γ{sub j} ∼ 2.5 and a kinetic energy of E{sub k,} {sub iso} ∼ 3.0 × 10{sup 53} erg.

  10. Jelly Quakes - Characteristics of periodic slip events in an analog model of strike slip seismotectonics using ballistic gelatin.

    NASA Astrophysics Data System (ADS)

    Rudolf, Michael; Rosenau, Matthias; Oncken, Onno

    2016-04-01

    Large lithospheric strike-slip faults, such as the San-Andreas Fault, North-Anatolian Fault, or the Tancheng-Lujiang Faultzone, are major sources of seismic hazard. The interplay of complex 3D-geometry and displacement style along the fault, coupled with a varying rheological layering makes it very difficult to model these faults on all relevant timescales. Here we present a novel experimental approach to model intra- and interplate strike-slip faults using a physical/ analog model. We model earthquakes as a stick-slip process, following a rate-and-state frictional law, with glass beads as granular material within a molded fault zone. Crustal elasticity is introduced by using ballistic gelatin (30 w%, pig skin) as analog material. Furthermore, the low-strength and viscous deep crust below 15 km depth, is modeled using a viscoelastic silicone oil (PDMS-G30M). The layered model crust floats on sugar syrup and is compressed in pure shear vice configuration. We monitor the compressive force along with surface kinematics from optical image correlation. The fault is oriented at 45° to the compression direction imposing ideal strike-slip kinematics onto it. After an initial loading phase the model shows periodic slip events occurring alongside with creep on the fault. Using digital image correlation, surface displacement maps are obtained which are similar to those of natural earthquakes. Coseismic displacement along strike is showing a similar bell-shaped distribution as for natural faults. Furthermore, the recurrence intervals and stress drops are scalable to the natural prototype. The modeling results are combined with numerical rate-and-state models using physical parameters from the experiment. This enables us to explore a wide range of parameters and to draw connections between the parameters that control the behavior of seismic and aseismic fault systems.

  11. The HyMeX Special Observation Period in Central Italy: Precipitation Measurements, Retrieval Techniques and Preliminary Results

    NASA Technical Reports Server (NTRS)

    Gatlin, Patrick; Wingo, Matt; Petersen, Walt; Marzano, Frank Silvio; Baldini, Luca; Picciotti, Errico; Colantonio, Matteo; Barbieri, Stefano; Di Fabio, Saverio; Montopoli, Mario; Roberto, Nicoletta; Adirosi, Elisa; Gorgucci, Eugenio; Anagnostou, Emmanoil N..; Ferretti, Rossella

    2013-01-01

    The Mediterranean area concentrates the major natural risks related to the water cycle, including heavy precipitation and flash-flooding during the fall season. The capability to predict such high-impact events remains weak because of the contribution of very fine-scale processes and their non-linear interactions with the larger scale processes. These societal and science issues motivate the HyMeX (Hydrological cycle in the Mediterranean Experiment, http://www.hymex.orgl) experimental programme. HyMeX aims at a better quantification and understanding of the water cycle in the Mediterranean with emphasis on intense events. The observation strategy of HyMEX is organized in a long-term (4 years) Enhanced Observation Periods (EOP) and short-term (2 months) Special Observation Periods (SOP). HyMEX has identified 3 main Mediterranean target areas: North-West (NW), Adriatic (A) and South-East (SE). Within each target area several hydrometeorological sites for heavy rainfall and flash flooding have been set up. The hydrometeorological sire in Central Italy (CI) is interested by both western and eastern fronts coming from the Atlantic Ocean and Siberia, respectively. Orographic precipitations play an important role due to the central Apennine range, which reaches nearly 3000 m (Gran Sasso peak). Moreover, convective systems commonly develop in CI during late summer and beginning of autumn, often causing localized hailstorms with cluster organized cells. Western fronts may heavily hit the Tiber basin crossing large urban areas (Rome), whereas eastern fronts can cause flash floods along the Adriatic coastline. Two major basins are involved within Cl region: Tiber basin (1000 km long) and its tributary Aniene and the Aterno-Pescara basin (300 km long). The first HyMeX SOP1.1 was carried out from Sept. till Nov. 2012 in the NW target area The Italian SOP1.1 was coordinated by the Centre of Excellence CETEMPS, University of L'Aquila, a city located in the CI heart. The CI area

  12. Coronal Fine Structure in Dynamic Events Observed by Hi-C

    NASA Technical Reports Server (NTRS)

    Winebarger, Amy; Schuler, Timothy

    2013-01-01

    The High-Resolution Coronal Imager (Hi-C) flew aboard a NASA sounding rocket on 2012 July 11 and captured roughly 345 s of high spatial and temporal resolution images of the solar corona in a narrowband 193 Angstrom channel. We have analyzed the fluctuations in intensity of Active Region 11520. We selected events based on a lifetime greater than 11 s (two Hi-C frames) and intensities greater than a threshold determined from the photon and readout noise. We compare the Hi-C events with those determined from AIA. We find that HI-C detects shorter and smaller events than AIA. We also find that the intensity increase in the Hi-C events is approx. 3 times greater than the intensity increase in the AIA events we conclude the events are related to linear sub-structure that is unresolved by AIA

  13. The Electron Density in Explosive Transition Region Events Observed by IRIS

    NASA Astrophysics Data System (ADS)

    Doschek, G. A.; Warren, H. P.; Young, P. R.

    2016-11-01

    We discuss the intensity ratio of the O iv line at 1401.16 Å to the Si iv line at 1402.77 Å in Interface Region Imaging Spectrograph (IRIS) spectra. This intensity ratio is important if it can be used to measure high electron densities that cannot be measured using line intensity ratios of two different O iv lines from the multiplet within the IRIS wavelength range. Our discussion is in terms of considerably earlier observations made from the Skylab manned space station and other spectrometers on orbiting spacecraft. The earlier data on the O iv and Si iv ratio and other intersystem line ratios not available to IRIS are complementary to IRIS data. In this paper, we adopt a simple interpretation based on electron density. We adopt a set of assumptions and calculate the electron density as a function of velocity in the Si iv line profiles of two explosive events. At zero velocity the densities are about 2-3 × 1011 cm-3, and near 200 km s-1 outflow speed the densities are about 1012 cm-3. The densities increase with outflow speed up to about 150 km s-1 after which they level off. Because of the difference in the temperature of formation of the two lines and other possible effects such as non-ionization equilibrium, these density measurements do not have the precision that would be available if there were some additional lines near the formation temperature of O iv.

  14. Observations of event-based streambed deformation in a gravel bed channel

    NASA Astrophysics Data System (ADS)

    Haschenburger, Judith K.

    2006-11-01

    The streambed is the major source of bed load sediment in gravel bed channels and is necessarily deformed during floods that mobilize sediment. This study uses observations of scour and fill from Carnation Creek, Canada, to articulate at-a-point relations of the occurrence and magnitude of bed deformation and the resulting adjustments in bed configuration over a series of flood events. The likelihood of local bed deformation by scour, fill, or both depends on flow magnitude. At most locations, there is an imbalance of scour and fill that leads to adjustments in bed elevation, and these imbalances increase with flow. Persistent deformation of locations in lower portions of the bed topography tend to produce larger total exchanges between bed and mobile sediment over the flood series but locations that experience similar frequencies of bed deformation do not produce unique depth distributions. These results underscore the importance of understanding the coupling of scour and fill that produces streambed adjustment when modeling streambed evolution and managing river habitat.

  15. Testing the no-hair theorem with event horizon telescope observations of Sagittarius A*

    SciTech Connect

    Broderick, Avery E.; Johannsen, Tim; Loeb, Abraham; Psaltis, Dimitrios

    2014-03-20

    The advent of the Event Horizon Telescope (EHT), a millimeter-wave very long baseline interferometric array, has enabled spatially resolved studies of the subhorizon-scale structure for a handful of supermassive black holes. Among these, the supermassive black hole at the center of the Milky Way, Sagittarius A* (Sgr A*), presents the largest angular cross section. Thus far, these studies have focused on measurements of the black hole spin and the validation of low-luminosity accretion models. However, a critical input in the analysis of EHT data is the structure of the black hole spacetime, and thus these observations provide the novel opportunity to test the applicability of the Kerr metric to astrophysical black holes. Here we present the first simulated images of a radiatively inefficient accretion flow (RIAF) around Sgr A* employing a quasi-Kerr metric that contains an independent quadrupole moment in addition to the mass and spin that fully characterize a black hole in general relativity. We show that these images can be significantly different from the images of an RIAF around a Kerr black hole with the same spin and demonstrate the feasibility of testing the no-hair theorem by constraining the quadrupolar deviation from the Kerr metric with existing EHT data. Equally important, we find that the disk inclination and spin orientation angles are robust to the inclusion of additional parameters, providing confidence in previous estimations assuming the Kerr metric based on EHT observations. However, at present, the limits on potential modifications of the Kerr metric remain weak.

  16. Location of EMIC Wave Events Relative to the Plasmapause: Van Allen Probes Observations

    NASA Astrophysics Data System (ADS)

    Tetrick, S.; Engebretson, M. J.; Posch, J. L.; Kletzing, C.; Smith, C. W.; Wygant, J. R.; Gkioulidou, M.; Reeves, G. D.; Fennell, J. F.

    2015-12-01

    Many early theoretical studies of electromagnetic ion cyclotron (EMIC) waves generated in Earth's magnetosphere predicted that the equatorial plasmapause (PP) would be a preferred location for their generation. However, several large statistical studies in the past two decades, most notably Fraser and Nguyen [2001], have provided little support for this location. In this study we present a survey of the most intense EMIC waves observed by the EMFISIS fluxgate magnetometer on the Van Allen Probes-A spacecraft (with apogee at 5.9 RE) from its launch through the end of 2014, and have compared their location with simultaneous electron density data obtained by the EFW electric field instrument and ring current ion flux data obtained by the HOPE and RBSPICE instruments. We show distributions of these waves as a function of distance inside or outside the PP as a function of local time sector, frequency band (H+, He+, or both), and timing relative to magnetic storms and substorms. Most EMIC waves in this data set occurred within 1 RE of the PP in all local time sectors, but very few were limited to ± 0.1 RE, and most of these occurred in the 06-12 MLT sector during non-storm conditions. The majority of storm main phase waves in the dusk sector occurred inside the PP. He+ band waves dominated at most local times inside the PP, and H+ band waves were never observed there. Although the presence of elevated fluxes of ring current protons was common to all events, the configuration of lower energy ion populations varied as a function of geomagnetic activity and storm phase.

  17. Testing the No-hair Theorem with Event Horizon Telescope Observations of Sagittarius A*

    NASA Astrophysics Data System (ADS)

    Broderick, Avery E.; Johannsen, Tim; Loeb, Abraham; Psaltis, Dimitrios

    2014-03-01

    The advent of the Event Horizon Telescope (EHT), a millimeter-wave very long baseline interferometric array, has enabled spatially resolved studies of the subhorizon-scale structure for a handful of supermassive black holes. Among these, the supermassive black hole at the center of the Milky Way, Sagittarius A* (Sgr A*), presents the largest angular cross section. Thus far, these studies have focused on measurements of the black hole spin and the validation of low-luminosity accretion models. However, a critical input in the analysis of EHT data is the structure of the black hole spacetime, and thus these observations provide the novel opportunity to test the applicability of the Kerr metric to astrophysical black holes. Here we present the first simulated images of a radiatively inefficient accretion flow (RIAF) around Sgr A* employing a quasi-Kerr metric that contains an independent quadrupole moment in addition to the mass and spin that fully characterize a black hole in general relativity. We show that these images can be significantly different from the images of an RIAF around a Kerr black hole with the same spin and demonstrate the feasibility of testing the no-hair theorem by constraining the quadrupolar deviation from the Kerr metric with existing EHT data. Equally important, we find that the disk inclination and spin orientation angles are robust to the inclusion of additional parameters, providing confidence in previous estimations assuming the Kerr metric based on EHT observations. However, at present, the limits on potential modifications of the Kerr metric remain weak.

  18. Families of Granules, Flows, and Acoustic Events in the Solar Atmosphere from Hinode Observations

    NASA Astrophysics Data System (ADS)

    Malherbe, J.-M.; Roudier, T.; Frank, Z.; Rieutord, M.

    2015-02-01

    We investigate the relationship between trees of fragmenting granules (TFG), horizontal and vertical flows, and acoustic events (AE) in the photospheric network. AE are spatially concentrated and short-duration locations of acoustic energy flux. We performed observations at disk center of a 2D field of view (FOV) with high spatial and temporal resolutions provided by the Solar Optical Telescope onboard Hinode. Line profiles of Fe i 557.6 nm were recorded by the Narrow-band Filter Imager on an 80″×36″ FOV during five hours with a cadence of 22 seconds and 0.08″ pixel size. Vertical velocities were derived at two atmospheric levels allowing the determination of the energy flux at the acoustic frequency of 3.3 mHz. Families of granules and horizontal velocities were obtained from local correlation tracking (LCT) after segmentation and labeling of either continuum intensities or granular Doppler shifts. AE exhibit durations in the range 0.25 to 1 hour compatible with the lifetime of families (80 % do not last more than two hours). High-energy AE have the shortest lifetimes. We found that most AE occur in intergranular lanes located in or close to the boundaries between different families (called inter families) in regions with predominantly downward vertical motions and horizontal converging flows. In contrast, diverging flows are observed inside families, with a few AE in the intergranules. At the beginning of the sequence, when families are not yet detected, the distribution of AE is not uniform and is already organized at spatial lengths related to the mesogranular scale, with maximum contribution in the range 5″ to 10″, fully compatible with the scale of the maximum contribution of families in the TFG space. Although all sizes and durations seem to exist for families, their number decreases with increasing size and lifetime.

  19. Radio Observations of the Tidal Disruption Event XMMSL1 J0740‑85

    NASA Astrophysics Data System (ADS)

    Alexander, K. D.; Wieringa, M. H.; Ber