Ultrasonic tracking of shear waves using a particle filter

PubMed Central

Ingle, Atul N.; Ma, Chi; Varghese, Tomy

2015-01-01

Purpose: This paper discusses an application of particle filtering for estimating shear wave velocity in tissue using ultrasound elastography data. Shear wave velocity estimates are of significant clinical value as they help differentiate stiffer areas from softer areas which is an indicator of potential pathology. Methods: Radio-frequency ultrasound echo signals are used for tracking axial displacements and obtaining the time-to-peak displacement at different lateral locations. These time-to-peak data are usually very noisy and cannot be used directly for computing velocity. In this paper, the denoising problem is tackled using a hidden Markov model with the hidden states being the unknown (noiseless) time-to-peak values. A particle filter is then used for smoothing out the time-to-peak curve to obtain a fit that is optimal in a minimum mean squared error sense. Results: Simulation results from synthetic data and finite element modeling suggest that the particle filter provides lower mean squared reconstruction error with smaller variance as compared to standard filtering methods, while preserving sharp boundary detail. Results from phantom experiments show that the shear wave velocity estimates in the stiff regions of the phantoms were within 20% of those obtained from a commercial ultrasound scanner and agree with estimates obtained using a standard method using least-squares fit. Estimates of area obtained from the particle filtered shear wave velocity maps were within 10% of those obtained from B-mode ultrasound images. Conclusions: The particle filtering approach can be used for producing visually appealing SWV reconstructions by effectively delineating various areas of the phantom with good image quality properties comparable to existing techniques. PMID:26520761

RADIO EMISSION FROM RED-GIANT HOT JUPITERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fujii, Yuka; Spiegel, David S.; Mroczkowski, Tony

2016-04-01

When planet-hosting stars evolve off the main sequence and go through the red-giant branch, the stars become orders of magnitudes more luminous and, at the same time, lose mass at much higher rates than their main-sequence counterparts. Accordingly, if planetary companions exist around these stars at orbital distances of a few au, they will be heated up to the level of canonical hot Jupiters and also be subjected to a dense stellar wind. Given that magnetized planets interacting with stellar winds emit radio waves, such “Red-Giant Hot Jupiters” (RGHJs) may also be candidate radio emitters. We estimate the spectral auroralmore » radio intensity of RGHJs based on the empirical relation with the stellar wind as well as a proposed scaling for planetary magnetic fields. RGHJs might be intrinsically as bright as or brighter than canonical hot Jupiters and about 100 times brighter than equivalent objects around main-sequence stars. We examine the capabilities of low-frequency radio observatories to detect this emission and find that the signal from an RGHJ may be detectable at distances up to a few hundred parsecs with the Square Kilometer Array.« less

A review of ionospheric effects on Earth-space propagation

NASA Technical Reports Server (NTRS)

Klobuchar, J. A.

1984-01-01

A short description is given of each ionospheric total electron content (TEC) effect upon radio waves, along with a representative value of the magnitude of each of these effects under normal ionospheric conditions. A discussion is given of the important characteristics of average ionospheric TEC behavior and the temporal and spatial variability of TEC. Radio waves undergo several effects when they pass through the Earth's ionosphere. One of the most important of these effects is a retardation, or group delay, on the modulation or information carried on the radio wave that is due to its encounter with the free, thermal electrons in the Earth's ionosphere. Other effects the ionosphere has on radio waves include: radio frequency (RF) carrier phase advance; Doppler shift of the RF carrier of the radio wave; Faraday rotation of the plane of polarization of linearly polarized waves; angular refraction or bending of the radio wave path as it travels through the ionosphere; and amplitude and phase scintillations.

Magnetospheric radio and plasma wave research - 1987-1990

NASA Technical Reports Server (NTRS)

Kurth, W. S.

1991-01-01

This review covers research performed in the area of magnetospheric plasma waves and wave-particle interactions as well as magnetospheric radio emissions. The report focuses on the near-completion of the discovery phase of radio and plasma wave phenomena in the planetary magnetospheres with the successful completion of the Voyager 2 encounters of Neptune and Uranus. Consideration is given to the advances made in detailed studies and theoretical investigations of radio and plasma wave phenomena in the terrestrial magnetosphere or in magnetospheric plasmas in general.

Full-Wave Radio Characterization of Ionospheric Modification at HAARP

DTIC Science & Technology

2015-07-26

Full-Wave Radio Characterization of Ionospheric Modification at HAARP We have studied electrostatic and electromagnetic turbulence stimulated by...radio receivers at HAARP in Alaska, and ground-based radio receivers, incoherent scatter radars, and in-situ measurements from Canadian, ESA, and Polish...363255 San Juan, PR 00936 -3255 31-May-2015 ABSTRACT Final Report: Full-Wave Radio Characterization of Ionospheric Modification at HAARP Report Title We

Characteristics of coronal shock waves and solar type 2 radio bursts

NASA Technical Reports Server (NTRS)

Mann, G.; Classen, H.-T.

1995-01-01

In the solar corona shock waves generated by flares and/or coronal mass ejections can be observed by radio astronomical methods in terms of solar type 2 radio bursts. In dynamic radio spectra they appear as emission stripes slowly drifting from high to low frequencies. A sample of 25 solar type 2 radio bursts observed in the range of 40 - 170 MHz with a time resolution of 0.1 s by the new radiospectrograph of the Astrophvsikalisches Institut Potsdam in Tremsdorf is statistically investigated concerning their spectral features, i.e, drift rate, instantaneous bandwidth, and fundamental harmonic ratio. In-situ plasma wave measurements at interplanetary shocks provide the assumption that type 2 radio radiation is emitted in the vicinity of the transition region of shock waves. Thus, the instantaneous bandwidth of a solar type 2 radio burst would reflect the density jump across the associated shock wave. Comparing the inspection of the Rankine-Hugoniot relations of shock waves under coronal circumstances with those obtained from the observational study, solar type 2 radio bursts should be regarded to be generated by weak supercritical, quasi-parallel, fast magnetosonic shock waves in the corona.

Grating formation by a high power radio wave in near-equator ionosphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Singh, Rohtash; Sharma, A. K.; Tripathi, V. K.

2011-11-15

The formation of a volume grating in the near-equator regions of ionosphere due to a high power radio wave is investigated. The radio wave, launched from a ground based transmitter, forms a standing wave pattern below the critical layer, heating the electrons in a space periodic manner. The thermal conduction along the magnetic lines of force inhibits the rise in electron temperature, limiting the efficacy of heating to within a latitude of few degrees around the equator. The space periodic electron partial pressure leads to ambipolar diffusion creating a space periodic density ripple with wave vector along the vertical. Suchmore » a volume grating is effective to cause strong reflection of radio waves at a frequency one order of magnitude higher than the maximum plasma frequency in the ionosphere. Linearly mode converted plasma wave could scatter even higher frequency radio waves.« less

Type II Radio Bursts Observed by STEREO/Waves and Wind/Waves instruments

NASA Astrophysics Data System (ADS)

Krupar, V.; Magdalenic, J.; Zhukov, A.; Rodriguez, L.; Mierla, M.; Maksimovic, M.; Cecconi, B.; Santolik, O.

2013-12-01

Type II radio bursts are slow-drift emissions triggered by suprathermal electrons accelerated on shock fronts of propagating CMEs. We present several events at kilometric wavelengths observed by radio instruments onboard the STEREO and Wind spacecraft. The STEREO/Waves and Wind/Waves have goniopolarimetric (GP, also referred to as direction finding) capabilities that allow us to triangulate radio sources when an emission is observed by two or more spacecraft. As the GP inversion has high requirements on the signal-to-noise ratio we only have a few type II radio bursts with sufficient intensity for this analysis. We have compared obtained radio sources with white-light observations of STEREO/COR and STEREO/HI instruments. Our preliminary results indicate that radio sources are located at flanks of propagating CMEs.

Imaging spectroscopy of solar radio burst fine structures.

PubMed

Kontar, E P; Yu, S; Kuznetsov, A A; Emslie, A G; Alcock, B; Jeffrey, N L S; Melnik, V N; Bian, N H; Subramanian, P

2017-11-15

Solar radio observations provide a unique diagnostic of the outer solar atmosphere. However, the inhomogeneous turbulent corona strongly affects the propagation of the emitted radio waves, so decoupling the intrinsic properties of the emitting source from the effects of radio wave propagation has long been a major challenge in solar physics. Here we report quantitative spatial and frequency characterization of solar radio burst fine structures observed with the Low Frequency Array, an instrument with high-time resolution that also permits imaging at scales much shorter than those corresponding to radio wave propagation in the corona. The observations demonstrate that radio wave propagation effects, and not the properties of the intrinsic emission source, dominate the observed spatial characteristics of radio burst images. These results permit more accurate estimates of source brightness temperatures, and open opportunities for quantitative study of the mechanisms that create the turbulent coronal medium through which the emitted radiation propagates.

Discovering the Invisible Universe.

ERIC Educational Resources Information Center

Friedman, Herbert

1991-01-01

The discovery of radio waves, infrared, and x-rays and their importance in describing the universe and its origins is discussed. Topics include radio waves from space, the radio pioneers of World War II, radio telescopes, infrared radiation, satellites, space missions, and x-ray telescopes. (KR)

A multidisciplinary study of planetary, solar and astrophysical radio emissions

NASA Technical Reports Server (NTRS)

Gurnett, D. A.; Calvert, W.; Fielder, R.; Goertz, C.; Grabbe, C.; Kurth, W.; Mutel, R.; Sheerin, J.; Mellott, M.; Spangler, S.

1986-01-01

Combination of the related fields of planetary, solar, and astrophysical radio emissions was attempted in order to more fully understand the radio emission processes. Topics addressed include: remote sensing of astrophysical plasma turbulence; Alfven waves; astrophysical shock waves; surface waves; very long base interferometry results; very large array observations; solar magnetic flux; and magnetohydrodynamic waves as a tool for solar corona diagnostics.

Mystery solved: discovery of extended radio emission in the merging galaxy cluster Abell 2146

NASA Astrophysics Data System (ADS)

Hlavacek-Larrondo, J.; Gendron-Marsolais, M.-L.; Fecteau-Beaucage, D.; van Weeren, R. J.; Russell, H. R.; Edge, A.; Olamaie, M.; Rumsey, C.; King, L.; Fabian, A. C.; McNamara, B.; Hogan, M.; Mezcua, M.; Taylor, G.

2018-04-01

Abell 2146 (z = 0.232) is a massive galaxy cluster currently undergoing a spectacular merger in the plane of the sky with a bullet-like morphology. It was the first system in which both the bow and upstream shock fronts were detected at X-ray wavelengths (Mach ˜2), yet deep Giant MetreWave Telescope 325 MHz observations failed to detect extended radio emission associated with the cluster as is typically seen in such systems. We present new, multiconfiguration 1-2 GHz Karl G. Jansky Very Large Array (VLA) observations of Abell 2146 totalling 16 h of observations. These data reveal for the first time the presence of an extended (≈850 kpc), faint radio structure associated with Abell 2146. The structure appears to harbour multiple components, one associated with the upstream shock that we classify as a radio relic and one associated with the subcluster core that is consisted as being a radio halo bounded by the bow shock. The newly detected structures have some of the lowest radio powers detected thus far in any cluster (P1.4 GHz, halo = 2.4 ± 0.2 × 1023 W Hz-1 and P1.4 GHz, relic = 2.2 ± 0.2 × 1023 W Hz-1). The flux measurement of the halo, as well as its morphology, also suggests that the halo was recently created (≈0.3 Gyr after core passage), consistent with the dynamical state of the cluster. These observations demonstrate the capacity of the upgraded VLA to detect extremely faint and extended radio structures. Based on these observations, we predict that many more radio relics and radio haloes in merging clusters should be detected by future radio facilities such as the Square Kilometre Array.

Prospects of using medium-wave band for radio communication with rescue mobile teams of EMERCOM of Russia

NASA Astrophysics Data System (ADS)

Bazhukov, I. F.; Dulkejt, I. V.; Zavyalov, S. A.; Lvova, Yu V.; Lyashuk, A. N.; Puzyrev, P. I.; Rekunov, S. G.; Chaschin, E. A.; Sharapov, S. V.

2018-01-01

The results of tests in-situ of the prototype of medium-wave mobile radio station «Noema-SV» in Western Siberia, Omsk region and Vorkuta Arctic Integrated Emergency and Rescue Center of EMERCOM of Russia are presented. Radio paths tests in-situ in the Far North show the possibility of radio communication with rescue mobile teams of EMERCOM of Russia in the medium-wave band within distances of several tens of kilometers of rugged topography. The radio range on a flat terrain increases to several hundreds of kilometers. Shortened medium-wave band antennas developed at OmSTU and employed by rescue mobile teams of EMERCOM of Russia were used in.

Source Regions of the Type II Radio Burst Observed During a CME-CME Interaction on 2013 May 22

NASA Technical Reports Server (NTRS)

Makela, P.; Gopalswamy, N.; Reiner, M. J.; Akiyama, S.; Krupar, V.

2016-01-01

We report on our study of radio source regions during the type II radio burst on 2013 May 22 based on direction finding analysis of the Wind/WAVES and STEREO/WAVES (SWAVES) radio observations at decameter-hectometric wavelengths. The type II emission showed an enhancement that coincided with the interaction of two coronal mass ejections (CMEs) launched in sequence along closely spaced trajectories. The triangulation of the SWAVES source directions posited the ecliptic projections of the radio sources near the line connecting the Sun and the STEREO-A spacecraft. The WAVES and SWAVES source directions revealed shifts in the latitude of the radio source, indicating that the spatial location of the dominant source of the type II emission varies during the CME-CME interaction. The WAVES source directions close to 1MHz frequencies matched the location of the leading edge of the primary CME seen in the images of the LASCO/C3 coronagraph. This correspondence of spatial locations at both wavelengths confirms that the CME-CME interaction region is the source of the type II enhancement. Comparison of radio and white-light observations also showed that at lower frequencies scattering significantly affects radio wave propagation.

The Hunt for a Counterpart to GW150914

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2016-07-01

On 14 September 2015, the Laser Interferometer Gravitational-wave Observatory (LIGO) in a pre-operative testing state at the time detected its first sign of gravitational-waves. The LIGO team sprang into action, performing data-quality checks on this unexpected signal. Within two days, they had sent a notification to 63 observing teams at observatories representing the entire electromagnetic spectrum, from radio to gamma-ray wavelengths.Illustration of a binary neutron star merger. The neutron stars 1) inspiral, 2) can produce a short gamma-ray burst, 3) can fling out hot, radioactive material in the form of a kilonova, and 4) form a massive neutron star or black hole with a possible remnant debris disk around it. [NASA/ESA/A. Feild (STScI)]Thus began the very first hunt for an electromagnetic counterpart to a detected gravitational wave signal.What were they looking for?As two compact objects in a binary system merge, the system is expected to emit energy in the form of gravitational waves. If both of the compact objects are black holes, were unlikely to see any electromagnetic radiation in the process, unless the merger is occurring in an (improbable) environment filled with gas and dust.But if one or both of the two compact objects is a neutron star, then there are a number of electromagnetic signatures that could occur due to energetic outflows. If a relativistic jet forms, we could see a short gamma-ray burst and X-ray, optical, and radio afterglows. Sub-relativistic outflows could produce optical and near-infrared signals, or a radio blast wave.Timeline of observations of GW150914, separated by wavelength band, and relative to the time of the gravitational-wave trigger. The top row shows LIGO information releases. The bottom four rows show high-energy, optical, near-infrared, and radio observations, respectively. Click for a closer look! [Abbott et al. 2016]Surprise SignalSince LIGO and Virgo (LIGOs European counterpart), wereprimarily expecting to detect binaries involving neutron stars, they set up a notification system to be able to quickly alert electromagnetic observatories of a gravitational-wave detection. Those observatories would then be able to follow up on the gravitational-wave detectorsrough localization, with the goal of detecting the source by its electromagnetic signature.Given that LIGO had only just come online for testing when GW150914 was detected, its impressive that the pipeline was ready and there were observatories able to follow up so quickly! When the alert went out, 25 teams responded, mobilizing satellites and ground-based telescopes spanning 19 orders of magnitude in electromagnetic wavelength.The Search PartyThe only information the teams were initially given was the localization of the signal to roughly 600 square degrees on the sky. With this starting point, over the next three months, these 25 facilities carefully observed the entirety of the estimated localization area.Footprints of observations in comparison with the initial LIGO localization of GW150914 (black contours). Shown are radio fields (red), optical/infrared fields (green), and X-ray fields (blue circles); not shown are the all-sky Fermi GBM, LAT, INTEGRAL SPI-ACS, and MAXI observations. [Abbott et al. 2016]Some high-energy observatories, like Fermi and INTEGRAL, covered the whole sky. Many optical facilities used a tiling strategy, together covering about 900 square degrees. Still other observatories used a targeted approach, specifically looking at fields that contained a high density of nearby galaxies, in the hopes of detecting signs of a neutron-star merger or a core-collapse supernova.For the transient sources that were found, follow-up spectroscopy and further photometry was performed, to determine if the transient could have been the source of the detected gravitational waves.What Was the Outcome?No electromagnetic counterpart to GW150914 was found. It turns out this isnt surprising; GW150914 was later determined to have been the merger of two black holes, which should not generate an electromagnetic signature.So why report on this? In the publication prepared jointly by LIGO, Virgo, and these 25 teams (with one of the longer author lists youre likely to encounter!), the authors emphasize not the conclusion, but the process leading to it.In spite of the fact that LIGO had not yet even begun its first observing run, the alert system worked, and the community mobilized to cover the entire 600 square degrees of sky with observations and follow-up characterization of candidate sources. If all this can be accomplished for an unexpected signal, imagine how well the system will work for future detections during actual science runs! With any luck, well be identifying the electromagnetic counterparts to gravitational-wave sources soon.CitationB. P. Abbott et al 2016 ApJ 826 L13. doi:10.3847/2041-8205/826/1/L13

Detection of acoustic-gravity waves in lower ionosphere by VLF radio waves

NASA Astrophysics Data System (ADS)

Nina, A.; Čadež, V. M.

2013-09-01

We present a new method to study harmonic waves in the low ionosphere (60 - 90 km) by detecting their effects on reflection of very low frequency (VLF) radio waves. Our procedure is based on amplitude analysis of reflected VLF radio waves recorded in real time, which yields an insight into the dynamics of the ionosphere at heights where VLF radio waves are being reflected. The method was applied to perturbations induced by the solar terminator motions at sunrises and sunsets. The obtained results show that typical perturbation frequencies found to exist in higher regions of the atmosphere are also present in the lower ionosphere, which indicates a global nature of the considered oscillations. In our model atmosphere, they turn out to be the acoustic and gravity waves with comparatively short and long periods, respectively.

Design, fabrication, and measurement of reflective metasurface for orbital angular momentum vortex wave in radio frequency domain

NASA Astrophysics Data System (ADS)

Yu, Shixing; Li, Long; Shi, Guangming; Zhu, Cheng; Zhou, Xiaoxiao; Shi, Yan

2016-03-01

In this paper, a reflective metasurface is designed, fabricated, and experimentally demonstrated to generate an orbital angular momentum (OAM) vortex wave in radio frequency domain. Theoretical formula of phase-shift distribution is deduced and used to design the metasurface producing vortex radio waves. The prototype of a practical configuration is designed, fabricated, and measured to validate the theoretical analysis at 5.8 GHz. The simulated and experimental results verify that the vortex waves with different OAM mode numbers can be flexibly generated by using sub-wavelength reflective metasurfaces. The proposed method and metasurface pave a way to generate the OAM vortex waves for radio and microwave wireless communication applications.

Juno Detects a Ham Radio HI from Earth

NASA Image and Video Library

2013-12-10

During its close flyby of Earth, NASA Jupiter-bound Juno spacecraft listened for a coordinated, global transmission from amateur radio operators using its radio and plasma wave science instrument, known as Waves.

Studying the evolution of a type III radio from the Sun up to 1 AU

NASA Astrophysics Data System (ADS)

Mann, Gottfried; Breitling, Frank; Vocks, Christian; Fallows, Richard; Melnik, Valentin; Konovalenko, Alexander

2017-04-01

On March 16, 2016, a type III burst was observed with the ground-based radio telescopes LOFAR and URAN-2 as well as with the radiospectrometer aboard the spacecraft WIND.It started at 80 MHz at 06:37 UT and reached 50 kHz after 23 minutes. A type III burst are considered as the radio signature of an electron beam travelling from the corona into the interplanetary space. The energetic electrons carrying the beam excites Langmuir waves, which convert into radio waves by wave-particle interaction. The relationship between the drift rate and the frequency as derived from the dynamic radio spectra reveals that the velocity of the electrons generating the radio waves of the type III burst is increasing with increasing distance from the center of the Sun.

INSPIRE

NASA Technical Reports Server (NTRS)

Taylor, Bill; Pine, Bill

2003-01-01

INSPIRE (Interactive NASA Space Physics Ionosphere Radio Experiment - http://image.gsfc.nasa.gov/poetry/inspire) is a non-profit scientific, educational organization whose objective is to bring the excitement of observing natural and manmade radio waves in the audio region to high school students and others. The project consists of building an audio frequency radio receiver kit, making observations of natural and manmade radio waves and analyzing the data. Students also learn about NASA and our natural environment through the study of lightning, the source of many of the audio frequency waves, the atmosphere, the ionosphere, and the magnetosphere where the waves travel.

Effectiveness of radio waves application in modern general dental procedures: An update.

PubMed

Qureshi, Arslan; Kellesarian, Sergio Varela; Pikos, Michael A; Javed, Fawad; Romanos, Georgios E

2017-01-01

The purpose of the present study was to review indexed literature and provide an update on the effectiveness of high-frequency radio waves (HRW) application in modern general dentistry procedures. Indexed databases were searched to identify articles that assessed the efficacy of radio waves in dental procedures. Radiosurgery is a refined form of electrosurgery that uses waves of electrons at a radiofrequency ranging between 2 and 4 MHz. Radio waves have also been reported to cause much less thermal damage to peripheral tissues compared with electrosurgery or carbon dioxide laser-assisted surgery. Formation of reparative dentin in direct pulp capping procedures is also significantly higher when HRW are used to achieve hemostasis in teeth with minimally exposed dental pulps compared with traditional techniques for achieving hemostasis. A few case reports have reported that radiosurgery is useful for procedures such as gingivectomy and gingivoplasty, stage-two surgery for implant exposure, operculectomy, oral biopsy, and frenectomy. Radiosurgery is a relatively modern therapeutic methodology for the treatment of trigeminal neuralgia; however, its long-term efficacy is unclear. Radio waves can also be used for periodontal procedures, such as gingivectomies, coronal flap advancement, harvesting palatal grafts for periodontal soft tissue grafting, and crown lengthening. Although there are a limited number of studies in indexed literature regarding the efficacy of radio waves in modern dentistry, the available evidence shows that use of radio waves is a modernization in clinical dentistry that might be a contemporary substitute for traditional clinical dental procedures.

Simple simulation training system for short-wave radio station

NASA Astrophysics Data System (ADS)

Tan, Xianglin; Shao, Zhichao; Tu, Jianhua; Qu, Fuqi

2018-04-01

The short-wave radio station is a most important transmission equipment of our signal corps, but in the actual teaching process, which exist the phenomenon of fewer equipment and more students, making the students' short-wave radio operation and practice time is very limited. In order to solve the above problems, to carry out shortwave radio simple simulation training system development is very necessary. This project is developed by combining hardware and software to simulate the voice communication operation and signal principle of shortwave radio station, and can test the signal flow of shortwave radio station. The test results indicate that this system is simple operation, human-machine interface friendly and can improve teaching more efficiency.

Wave Phenomena Associated with Interplanetary Shocks

NASA Astrophysics Data System (ADS)

Golla, T.; MacDowall, R. J.

2016-12-01

Although laboratory and space-based experiments were used for the last several decades to study the collisionless shocks, several questions remain less than fully understood. These include: (1) what type of wave-particle energy dissipation is responsible for the shock formation, (2) what type of in-situ waves occur in the upstream, transition and downstream regions, and (3) which physical processes are responsible for the excitation of the fundamental and second harmonic solar type II radio emissions. In this study, we will address these issues using (1) the in situ and radio wave data obtained by the WAVES experiments of the STEREO A and B, and WIND spacecraft, especially the high time resolution data from the time domain samplers (TDS) of these WAVES experiments and (2) the Fourier, wavelet and higher order spectral analysis techniques. Using the in situ wave data, especially the high time resolution data observed during the local type II bursts, we will identify the nonlinear processes associated with these solar radio emissions. Comparing the estimated radio intensities by the known emission mechanisms for the observed peak Langmuir wave intensities with the observed peak radio intensities of type II bursts, we will identify the emission mechanisms.

Electro-optic Q-switch

NASA Technical Reports Server (NTRS)

Zou, Yingyin (Inventor); Chen, Qiushui (Inventor); Zhang, Run (Inventor); Jiang, Hua (Inventor)

2006-01-01

An electro-optic Q-switch for generating sequence of laser pulses was disclosed. The Q-switch comprises a quadratic electro-optic material and is connected with an electronic unit generating a radio frequency wave with positive and negative pulses alternatively. The Q-switch is controlled by the radio frequency wave in such a way that laser pulse is generated when the radio frequency wave changes its polarity.

Walkie-Talkie Measurements for the Speed of Radio Waves in Air

ERIC Educational Resources Information Center

Dombi, Andra; Tunyagi, Arthur; Neda, Zoltan

2013-01-01

A handheld emitter-receiver device suitable for the direct estimation of the velocity of radio waves in air is presented. The velocity of radio waves is measured using the direct time-of-flight method, without the need for any tedious and precise settings. The results for two measurement series are reported. Both sets of results give an estimate…

Stationary Planetary Waves in the Mars Winter Atmosphere as seen by the Radio Science Experiment MaRS on Mars Express

NASA Astrophysics Data System (ADS)

Tellmann, Silvia; Pätzold, Martin; Häusler, Bernd; Tyler, Leonard G.; Hinson, David P.

2015-11-01

Stationary (Rossby) Waves are excited by the interaction of the zonally varying topography with the strong eastward winter jets. They lead to distinctive longitudinal temperature variations which contribute significantly to the asymmetry of the seasonal polar CO2 ice caps and are also important for the dust redistribution in the planetary atmosphere.Radio Science profiles from the Mars Express Radio Science Experiment MaRS at northern and southern high latitudes are used to gain insight into winter stationary wave structures on both hemispheres.Mars Global Surveyor (MGS) radio occultation measurements from the same season and year with their exceptionally good longitudinal and temporal coverage can be used to estimate the influence of transient eddies. Transient waves are especially important in the northern winter hemisphere.Wave number 2 stationary waves, driven by topography, are dominant in the northern winter latitudes while the wave number 1 wave is the most significant wave number during southern winter. The wave amplitudes peak around winter solstice on both hemispheres.Radio occultation measurements provide the unique opportunity to determine simultaneous measurements of temperature and geopotential height structures. Assuming geostrophic balance, these measurements can be used to determine meridional winds and eddy heat fluxes which provide further insight into the contribution of stationary waves to the heat exchange between the poles and the lower latitudes.

Hyperthermia for treating cancer

MedlinePlus

... forms of energy may be used, including: Radio waves Microwaves Ultrasound waves Heat may be delivered using: An external machine ... rectum. A needle-like probe to sends radio wave energy directly into the tumor to kill cancer ...

On the wavelength dependence of the effects of turbulence on average refraction angles in occultations by planetary atmospheres

NASA Technical Reports Server (NTRS)

Haugstad, B. S.; Eshleman, V. R.

1979-01-01

The dependence of the effects of planetary atmospheric turbulence on radio or optical wavelength in occultation experiments is discussed, and the analysis of Hubbard and Jokipii (1977) is criticized. It is argued that in deriving a necessary condition for the applicability of their method, Hubbard and Jokipii neglect a factor proportional to the square of the ratio of atmospheric or local Fresnel zone radius and the inner scale of turbulence, and fail to establish sufficient conditions, thereby omitting the square of the ratio of atmospheric scale height and the local Fresnel zone radius. The total discrepancy is said to mean that the results correspond to geometrical optics instead of wave optics, as claimed, thus being inapplicable in a dicussion of wavelength dependence. Calculations based on geometrical optics show that the bias in the average bending angle depends on the wavelength in the same way as does the bias in phase path caused by turbulence in a homogeneous atmosphere. Hubbard and Jokipii comment that the criterion of Haugstad and Eshleman is incorrect and show that there is a large wave optical domain where the results are independent of wavelength.

Search for transient gravitational waves in coincidence with short-duration radio transients during 2007-2013

NASA Astrophysics Data System (ADS)

Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L.; Ain, A.; Ajith, P.; Allen, B.; Allocca, A.; Altin, P. A.; Anderson, S. B.; Anderson, W. G.; Arai, K.; Araya, M. C.; Arceneaux, C. C.; Areeda, J. S.; Arnaud, N.; Arun, K. G.; Ascenzi, S.; Ashton, G.; Ast, M.; Aston, S. M.; Astone, P.; Aufmuth, P.; Aulbert, C.; Babak, S.; Bacon, P.; Bader, M. K. M.; Baker, P. T.; Baldaccini, F.; Ballardin, G.; Ballmer, S. W.; Barayoga, J. C.; Barclay, S. E.; Barish, B. C.; Barker, D.; Barone, F.; Barr, B.; Barsotti, L.; Barsuglia, M.; Barta, D.; Bartlett, J.; Bartos, I.; Bassiri, R.; Basti, A.; Batch, J. C.; Baune, C.; Bavigadda, V.; Bazzan, M.; Behnke, B.; Bejger, M.; Bell, A. S.; Bell, C. J.; Berger, B. K.; Bergman, J.; Bergmann, G.; Berry, C. P. L.; Bersanetti, D.; Bertolini, A.; Betzwieser, J.; Bhagwat, S.; Bhandare, R.; Bilenko, I. A.; Billingsley, G.; Birch, J.; Birney, R.; Biscans, S.; Bisht, A.; Bitossi, M.; Biwer, C.; Bizouard, M. A.; Blackburn, J. K.; Blair, C. D.; Blair, D. G.; Blair, R. M.; Bloemen, S.; Bock, O.; Bodiya, T. P.; Boer, M.; Bogaert, G.; Bogan, C.; Bohe, A.; Bojtos, P.; Bond, C.; Bondu, F.; Bonnand, R.; Boom, B. A.; Bork, R.; Boschi, V.; Bose, S.; Bouffanais, Y.; Bozzi, A.; Bradaschia, C.; Brady, P. R.; Braginsky, V. B.; Branchesi, M.; Brau, J. E.; Briant, T.; Brillet, A.; Brinkmann, M.; Brisson, V.; Brockill, P.; Brooks, A. F.; Brown, D. A.; Brown, D. D.; Brown, N. M.; Buchanan, C. C.; Buikema, A.; Bulik, T.; Bulten, H. J.; Buonanno, A.; Buskulic, D.; Buy, C.; Byer, R. L.; Cadonati, L.; Cagnoli, G.; Cahillane, C.; Calderón Bustillo, J.; Callister, T.; Calloni, E.; Camp, J. B.; Cannon, K. C.; Cao, J.; Capano, C. D.; Capocasa, E.; Carbognani, F.; Caride, S.; Casanueva Diaz, J.; Casentini, C.; Caudill, S.; Cavaglià, M.; Cavalier, F.; Cavalieri, R.; Cella, G.; Cepeda, C. B.; Cerboni Baiardi, L.; Cerretani, G.; Cesarini, E.; Chakraborty, R.; Chalermsongsak, T.; Chamberlin, S. J.; Chan, M.; Chao, S.; Charlton, P.; Chassande-Mottin, E.; Chen, H. Y.; Chen, Y.; Cheng, C.; Chincarini, A.; Chiummo, A.; Cho, H. S.; Cho, M.; Chow, J. H.; Christensen, N.; Chu, Q.; Chua, S.; Chung, S.; Ciani, G.; Clara, F.; Clark, J. A.; Cleva, F.; Coccia, E.; Cohadon, P.-F.; Colla, A.; Collette, C. G.; Cominsky, L.; Constancio, M.; Conte, A.; Conti, L.; Cook, D.; Corbitt, T. R.; Cornish, N.; Corsi, A.; Cortese, S.; Costa, C. A.; Coughlin, M. W.; Coughlin, S. B.; Coulon, J.-P.; Countryman, S. T.; Couvares, P.; Coward, D. M.; Cowart, M. J.; Coyne, D. C.; Coyne, R.; Craig, K.; Creighton, J. D. E.; Cripe, J.; Crowder, S. G.; Cumming, A.; Cunningham, L.; Cuoco, E.; Dal Canton, T.; Danilishin, S. L.; D'Antonio, S.; Danzmann, K.; Darman, N. S.; Dattilo, V.; Dave, I.; Daveloza, H. P.; Davier, M.; Davies, G. S.; Daw, E. J.; Day, R.; DeBra, D.; Debreczeni, G.; Degallaix, J.; De Laurentis, M.; Deléglise, S.; Del Pozzo, W.; Denker, T.; Dent, T.; Dergachev, V.; De Rosa, R.; DeRosa, R. T.; DeSalvo, R.; Dhurandhar, S.; Díaz, M. C.; Di Fiore, L.; Di Giovanni, M.; Di Girolamo, T.; Di Lieto, A.; Di Pace, S.; Di Palma, I.; Di Virgilio, A.; Dojcinoski, G.; Dolique, V.; Donovan, F.; Dooley, K. L.; Doravari, S.; Douglas, R.; Downes, T. P.; Drago, M.; Drever, R. W. P.; Driggers, J. C.; Du, Z.; Ducrot, M.; Dwyer, S. E.; Edo, T. B.; Edwards, M. C.; Effler, A.; Eggenstein, H.-B.; Ehrens, P.; Eichholz, J.; Eikenberry, S. S.; Engels, W.; Essick, R. C.; Etzel, T.; Evans, M.; Evans, T. M.; Everett, R.; Factourovich, M.; Fafone, V.; Fair, H.; Fairhurst, S.; Fan, X.; Fang, Q.; Farinon, S.; Farr, B.; Farr, W. M.; Favata, M.; Fays, M.; Fehrmann, H.; Fejer, M. M.; Ferrante, I.; Ferreira, E. C.; Ferrini, F.; Fidecaro, F.; Fiori, I.; Fiorucci, D.; Fisher, R. P.; Flaminio, R.; Fletcher, M.; Fournier, J.-D.; Frasca, S.; Frasconi, F.; Frei, Z.; Freise, A.; Frey, R.; Frey, V.; Fricke, T. T.; Fritschel, P.; Frolov, V. V.; Fulda, P.; Fyffe, M.; Gabbard, H. A. G.; Gair, J. R.; Gammaitoni, L.; Gaonkar, S. G.; Garufi, F.; Gaur, G.; Gehrels, N.; Gemme, G.; Genin, E.; Gennai, A.; George, J.; Gergely, L.; Germain, V.; Ghosh, Archisman; Ghosh, S.; Giaime, J. A.; Giardina, K. D.; Giazotto, A.; Gill, K.; Glaefke, A.; Goetz, E.; Goetz, R.; Gondan, L.; González, G.; Gonzalez Castro, J. M.; Gopakumar, A.; Gordon, N. A.; Gorodetsky, M. L.; Gossan, S. E.; Gosselin, M.; Gouaty, R.; Grado, A.; Graef, C.; Graff, P. B.; Granata, M.; Grant, A.; Gras, S.; Gray, C.; Greco, G.; Green, A. C.; Groot, P.; Grote, H.; Grunewald, S.; Guidi, G. M.; Guo, X.; Gupta, A.; Gupta, M. K.; Gushwa, K. E.; Gustafson, E. K.; Gustafson, R.; Hacker, J. J.; Hall, B. R.; Hall, E. D.; Hammond, G.; Haney, M.; Hanke, M. M.; Hanks, J.; Hanna, C.; Hannam, M. D.; Hanson, J.; Hardwick, T.; Harms, J.; Harry, G. M.; Harry, I. W.; Hart, M. J.; Hartman, M. T.; Haster, C.-J.; Haughian, K.; Heidmann, A.; Heintze, M. C.; Heitmann, H.; Hello, P.; Hemming, G.; Hendry, M.; Heng, I. S.; Hennig, J.; Heptonstall, A. W.; Heurs, M.; Hild, S.; Hoak, D.; Hodge, K. A.; Hofman, D.; Hollitt, S. E.; Holt, K.; Holz, D. E.; Hopkins, P.; Hosken, D. J.; Hough, J.; Houston, E. A.; Howell, E. J.; Hu, Y. M.; Huang, S.; Huerta, E. A.; Huet, D.; Hughey, B.; Husa, S.; Huttner, S. H.; Huynh-Dinh, T.; Idrisy, A.; Indik, N.; Ingram, D. R.; Inta, R.; Isa, H. N.; Isac, J.-M.; Isi, M.; Islas, G.; Isogai, T.; Iyer, B. R.; Izumi, K.; Jacqmin, T.; Jang, H.; Jani, K.; Jaranowski, P.; Jawahar, S.; Jiménez-Forteza, F.; Johnson, W. W.; Jones, D. I.; Jones, R.; Jonker, R. J. G.; Ju, L.; Haris, K.; Kalaghatgi, C. V.; Kalogera, V.; Kandhasamy, S.; Kang, G.; Kanner, J. B.; Karki, S.; Kasprzack, M.; Katsavounidis, E.; Katzman, W.; Kaufer, S.; Kaur, T.; Kawabe, K.; Kawazoe, F.; Kéfélian, F.; Kehl, M. S.; Keitel, D.; Kelley, D. B.; Kells, W.; Kennedy, R.; Key, J. S.; Khalaidovski, A.; Khalili, F. Y.; Khan, I.; Khan, S.; Khan, Z.; Khazanov, E. A.; Kijbunchoo, N.; Kim, Chunglee; Kim, J.; Kim, K.; Kim, Nam-Gyu; Kim, Namjun; Kim, Y.-M.; King, E. J.; King, P. J.; Kinzel, D. L.; Kissel, J. S.; Kleybolte, L.; Klimenko, S.; Koehlenbeck, S. M.; Kokeyama, K.; Koley, S.; Kondrashov, V.; Kontos, A.; Korobko, M.; Korth, W. Z.; Kowalska, I.; Kozak, D. B.; Kringel, V.; Królak, A.; Krueger, C.; Kuehn, G.; Kumar, P.; Kuo, L.; Kutynia, A.; Lackey, B. D.; Landry, M.; Lange, J.; Lantz, B.; Lasky, P. D.; Lazzarini, A.; Lazzaro, C.; Leaci, P.; Leavey, S.; Lebigot, E. O.; Lee, C. H.; Lee, H. K.; Lee, H. M.; Lee, K.; Lenon, A.; Leonardi, M.; Leong, J. R.; Leroy, N.; Letendre, N.; Levin, Y.; Levine, B. M.; Li, T. G. F.; Libson, A.; Littenberg, T. B.; Lockerbie, N. A.; Logue, J.; Lombardi, A. L.; Lord, J. E.; Lorenzini, M.; Loriette, V.; Lormand, M.; Losurdo, G.; Lough, J. D.; Lück, H.; Lundgren, A. P.; Luo, J.; Lynch, R.; Ma, Y.; MacDonald, T.; Machenschalk, B.; MacInnis, M.; Macleod, D. M.; Magaña-Sandoval, F.; Magee, R. M.; Mageswaran, M.; Majorana, E.; Maksimovic, I.; Malvezzi, V.; Man, N.; Mandic, V.; Mangano, V.; Mansell, G. L.; Manske, M.; Mantovani, M.; Marchesoni, F.; Marion, F.; Márka, S.; Márka, Z.; Markosyan, A. S.; Maros, E.; Martelli, F.; Martellini, L.; Martin, I. W.; Martin, R. M.; Martynov, D. V.; Marx, J. N.; Mason, K.; Masserot, A.; Massinger, T. J.; Masso-Reid, M.; Mastrogiovanni, S.; Matichard, F.; Matone, L.; Mavalvala, N.; Mazumder, N.; Mazzolo, G.; McCarthy, R.; McClelland, D. E.; McCormick, S.; McGuire, S. C.; McIntyre, G.; McIver, J.; McManus, D. J.; McWilliams, S. T.; Meacher, D.; Meadors, G. D.; Meidam, J.; Melatos, A.; Mendell, G.; Mendoza-Gandara, D.; Mercer, R. A.; Merilh, E. L.; Merzougui, M.; Meshkov, S.; Messenger, C.; Messick, C.; Metzdorff, R.; Meyers, P. M.; Mezzani, F.; Miao, H.; Michel, C.; Middleton, H.; Mikhailov, E. E.; Milano, L.; Miller, A. L.; Miller, J.; Millhouse, M.; Minenkov, Y.; Ming, J.; Mirshekari, S.; Mishra, C.; Mitra, S.; Mitrofanov, V. P.; Mitselmakher, G.; Mittleman, R.; Moggi, A.; Mohan, M.; Mohapatra, S. R. P.; Montani, M.; Moore, B. C.; Moore, C. J.; Moraru, D.; Moreno, G.; Morriss, S. R.; Mossavi, K.; Mours, B.; Mow-Lowry, C. M.; Mueller, C. L.; Mueller, G.; Muir, A. W.; Mukherjee, Arunava; Mukherjee, D.; Mukherjee, S.; Mukund, K. N.; Mullavey, A.; Munch, J.; Murphy, D. J.; Murray, P. G.; Mytidis, A.; Nardecchia, I.; Naticchioni, L.; Nayak, R. K.; Necula, V.; Nedkova, K.; Nelemans, G.; Neri, M.; Neunzert, A.; Newton, G.; Nguyen, T. T.; Nielsen, A. B.; Nissanke, S.; Nitz, A.; Nocera, F.; Nolting, D.; Normandin, M. E. N.; Nuttall, L. K.; Oberling, J.; Ochsner, E.; O'Dell, J.; Oelker, E.; Ogin, G. H.; Oh, J. J.; Oh, S. H.; Ohme, F.; Oliver, M.; Oppermann, P.; Oram, Richard J.; O'Reilly, B.; O'Shaughnessy, R.; Ott, C. D.; Ottaway, D. J.; Ottens, R. S.; Overmier, H.; Owen, B. J.; Pai, A.; Pai, S. A.; Palamos, J. R.; Palashov, O.; Palomba, C.; Pal-Singh, A.; Pan, H.; Pankow, C.; Pannarale, F.; Pant, B. C.; Paoletti, F.; Paoli, A.; Papa, M. A.; Paris, H. R.; Parker, W.; Pascucci, D.; Pasqualetti, A.; Passaquieti, R.; Passuello, D.; Patricelli, B.; Patrick, Z.; Pearlstone, B. L.; Pedraza, M.; Pedurand, R.; Pekowsky, L.; Pele, A.; Penn, S.; Pereira, R.; Perreca, A.; Phelps, M.; Piccinni, O. J.; Pichot, M.; Piergiovanni, F.; Pierro, V.; Pillant, G.; Pinard, L.; Pinto, I. M.; Pitkin, M.; Pletsch, H. J.; Poggiani, R.; Popolizio, P.; Post, A.; Powell, J.; Prasad, J.; Predoi, V.; Premachandra, S. S.; Prestegard, T.; Price, L. R.; Prijatelj, M.; Principe, M.; Privitera, S.; Prodi, G. A.; Prokhorov, L.; Puncken, O.; Punturo, M.; Puppo, P.; Pürrer, M.; Qi, H.; Qin, J.; Quetschke, V.; Quintero, E. A.; Quitzow-James, R.; Raab, F. J.; Rabeling, D. S.; Radkins, H.; Raffai, P.; Raja, S.; Rakhmanov, M.; Rapagnani, P.; Raymond, V.; Razzano, M.; Re, V.; Read, J.; Reed, C. M.; Regimbau, T.; Rei, L.; Reid, S.; Reitze, D. H.; Rew, H.; Ricci, F.; Riles, K.; Robertson, N. A.; Robie, R.; Robinet, F.; Rocchi, A.; Rolland, L.; Rollins, J. G.; Roma, V. J.; Romano, J. D.; Romano, R.; Romanov, G.; Romie, J. H.; Rosińska, D.; Rowan, S.; Rüdiger, A.; Ruggi, P.; Ryan, K.; Sachdev, S.; Sadecki, T.; Sadeghian, L.; Salconi, L.; Saleem, M.; Salemi, F.; Samajdar, A.; Sammut, L.; Sanchez, E. J.; Sandberg, V.; Sandeen, B.; Sanders, J. R.; Sassolas, B.; Sathyaprakash, B. S.; Saulson, P. R.; Sauter, O. E. S.; Savage, R. L.; Sawadsky, A.; Schale, P.; Schilling, R.; Schmidt, J.; Schmidt, P.; Schnabel, R.; Schofield, R. M. S.; Schönbeck, A.; Schreiber, E.; Schuette, D.; Schutz, B. F.; Scott, J.; Scott, S. M.; Sellers, D.; Sentenac, D.; Sequino, V.; Sergeev, A.; Serna, G.; Setyawati, Y.; Sevigny, A.; Shaddock, D. A.; Shahriar, M. S.; Shaltev, M.; Shao, Z.; Shapiro, B.; Shawhan, P.; Sheperd, A.; Shoemaker, D. H.; Shoemaker, D. M.; Siellez, K.; Siemens, X.; Sieniawska, M.; Sigg, D.; Silva, A. D.; Simakov, D.; Singer, A.; Singer, L. P.; Singh, A.; Singh, R.; Singhal, A.; Sintes, A. M.; Slagmolen, B. J. J.; Smith, J. R.; Smith, N. D.; Smith, R. J. E.; Son, E. J.; Sorazu, B.; Sorrentino, F.; Souradeep, T.; Srivastava, A. K.; Staley, A.; Steinke, M.; Steinlechner, J.; Steinlechner, S.; Steinmeyer, D.; Stephens, B. C.; Stiles, D.; Stone, R.; Strain, K. A.; Straniero, N.; Stratta, G.; Strauss, N. A.; Strigin, S.; Sturani, R.; Stuver, A. L.; Summerscales, T. Z.; Sun, L.; Sutton, P. J.; Swinkels, B. L.; Szczepańczyk, M. J.; Tacca, M.; Talukder, D.; Tanner, D. B.; Tápai, M.; Tarabrin, S. P.; Taracchini, A.; Taylor, R.; Theeg, T.; Thirugnanasambandam, M. P.; Thomas, E. G.; Thomas, M.; Thomas, P.; Thorne, K. A.; Thrane, E.; Tiwari, S.; Tiwari, V.; Tokmakov, K. V.; Tomlinson, C.; Tonelli, M.; Torres, C. V.; Torrie, C. I.; Töyrä, D.; Travasso, F.; Traylor, G.; Trifirò, D.; Tringali, M. C.; Trozzo, L.; Tse, M.; Turconi, M.; Tuyenbayev, D.; Ugolini, D.; Unnikrishnan, C. S.; Urban, A. L.; Usman, S. A.; Vahlbruch, H.; Vajente, G.; Valdes, G.; van Bakel, N.; van Beuzekom, M.; van den Brand, J. F. J.; Van Den Broeck, C.; Vander-Hyde, D. C.; van der Schaaf, L.; van Heijningen, J. V.; van Veggel, A. A.; Vardaro, M.; Vass, S.; Vasúth, M.; Vaulin, R.; Vecchio, A.; Vedovato, G.; Veitch, J.; Veitch, P. J.; Venkateswara, K.; Verkindt, D.; Vetrano, F.; Viceré, A.; Vinciguerra, S.; Vine, D. J.; Vinet, J.-Y.; Vitale, S.; Vo, T.; Vocca, H.; Vorvick, C.; Voss, D. V.; Vousden, W. D.; Vyatchanin, S. P.; Wade, A. R.; Wade, L. E.; Wade, M.; Walker, M.; Wallace, L.; Walsh, S.; Wang, G.; Wang, H.; Wang, M.; Wang, X.; Wang, Y.; Ward, R. L.; Warner, J.; Was, M.; Weaver, B.; Wei, L.-W.; Weinert, M.; Weinstein, A. J.; Weiss, R.; Welborn, T.; Wen, L.; Weßels, P.; Westphal, T.; Wette, K.; Whelan, J. T.; Whitcomb, S. E.; White, D. J.; Whiting, B. F.; Williams, R. D.; Williamson, A. R.; Willis, J. L.; Willke, B.; Wimmer, M. H.; Winkler, W.; Wipf, C. C.; Wittel, H.; Woan, G.; Worden, J.; Wright, J. L.; Wu, G.; Yablon, J.; Yam, W.; Yamamoto, H.; Yancey, C. C.; Yap, M. J.; Yu, H.; Yvert, M.; ZadroŻny, A.; Zangrando, L.; Zanolin, M.; Zendri, J.-P.; Zevin, M.; Zhang, F.; Zhang, L.; Zhang, M.; Zhang, Y.; Zhao, C.; Zhou, M.; Zhou, Z.; Zhu, X. J.; Zucker, M. E.; Zuraw, S. E.; Zweizig, J.; Archibald, A. M.; Banaszak, S.; Berndsen, A.; Boyles, J.; Cardoso, R. F.; Chawla, P.; Cherry, A.; Dartez, L. P.; Day, D.; Epstein, C. R.; Ford, A. J.; Flanigan, J.; Garcia, A.; Hessels, J. W. T.; Hinojosa, J.; Jenet, F. A.; Karako-Argaman, C.; Kaspi, V. M.; Keane, E. F.; Kondratiev, V. I.; Kramer, M.; Leake, S.; Lorimer, D.; Lunsford, G.; Lynch, R. S.; Martinez, J. G.; Mata, A.; McLaughlin, M. A.; McPhee, C. A.; Penucci, T.; Ransom, S.; Roberts, M. S. E.; Rohr, M. D. W.; Stairs, I. H.; Stovall, K.; van Leeuwen, J.; Walker, A. N.; Wells, B. L.; LIGO Scientific Collaboration; Virgo Collaboration

2016-06-01

We present an archival search for transient gravitational-wave bursts in coincidence with 27 single-pulse triggers from Green Bank Telescope pulsar surveys, using the LIGO, Virgo, and GEO interferometer network. We also discuss a check for gravitational-wave signals in coincidence with Parkes fast radio bursts using similar methods. Data analyzed in these searches were collected between 2007 and 2013. Possible sources of emission of both short-duration radio signals and transient gravitational-wave emission include starquakes on neutron stars, binary coalescence of neutron stars, and cosmic string cusps. While no evidence for gravitational-wave emission in coincidence with these radio transients was found, the current analysis serves as a prototype for similar future searches using more sensitive second-generation interferometers.

The theory of ionospheric focused heating

NASA Technical Reports Server (NTRS)

Bernhardt, P. A.; Duncan, L. M.

1987-01-01

Ionospheric modification by high power radio waves and by chemical releases are combined in a theoretical study of ionospheric focused heating. The release of materials which promote electron-ion recombination creates a hole in the bottomside ionosphere. The ionospheric hole focuses high power radio waves from a ground-based transmitter to give a 20 dB or greater enhancement in power density. The intense radio beam excites atomic oxygen by collisions with accelerated electrons. Airglow from the excited oxygen provides a visible trace of the focused beam. The large increase in the intensity of the radio beam stimulates new wave-plasma interactions. Numerical simulations show that the threshold for the two-plasmon decay instability is exceeded. The interaction of the pump electromagnetic wave with the backward plasmon produces a scattered electromagnetic wave at 3/2 the pump frequency. The scattered wave provides a unique signature of the two-plasmon decay process for ground-based detection.

Search for Transient Gravitational Waves in Coincidence with Short-Duration Radio Transients During 2007-2013

NASA Technical Reports Server (NTRS)

Abbott, B. P.; Hughey, Brennan; Zanolin, Michele; Szczepanczyk, Marek; Gill, Kiranjyot; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.;

The Unified Radio and Plasma wave investigation

NASA Technical Reports Server (NTRS)

Stone, R. G.; Bougeret, J. L.; Caldwell, J.; Canu, P.; De Conchy, Y.; Cornilleau-Wehrlin, N.; Desch, M. D.; Fainberg, J.; Goetz, K.; Goldstein, M. L.

1992-01-01

The scientific objectives of the Ulysses Unified Radio and Plasma wave (URAP) experiment are twofold: (1) the determination of the direction, angular size, and polarization of radio sources for remote sensing of the heliosphere and the Jovian magnetosphere and (2) the detailed study of local wave phenomena, which determine the transport coefficients of the ambient plasma. A brief discussion of the scientific goals of the experiment is followed by a comprehensive description of the instrument. The URAP sensors consist of a 72.5 m electric field antenna in the spin plane, a 7.5-m electric field monopole along the spin axis of a pair of orthogonal search coil magnetic antennas. The various receivers, designed to encompass specific needs of the investigation, cover the frequency range from dc to 1 MHz. A relaxation sounder provides very accurate electron density measurements. Radio and plasma wave observations are shown to demonstrate the capabilities and limitations of the URAP instruments: radio observations include solar bursts, auroral kilometric radiation, and Jovian bursts; plasma waves include Langmuir waves, ion acousticlike noise, and whistlers.

Sensory illusions: Common mistakes in physics regarding sound, light and radio waves

NASA Astrophysics Data System (ADS)

Briles, T. M.; Tabor-Morris, A. E.

2013-03-01

Optical illusions are well known as effects that we see that are not representative of reality. Sensory illusions are similar but can involve other senses than sight, such as hearing or touch. One mistake commonly noted among instructors is that students often mis-identify radio signals as sound waves and not as part of the electromagnetic spectrum. A survey of physics students from multiple high schools highlights the frequency of this common misconception, as well as other nuances on this misunderstanding. Many students appear to conclude that, since they experience radio broadcasts as sound, then sound waves are the actual transmission of radio signals and not, as is actually true, a representation of those waves as produced by the translator box, the radio. Steps to help students identify and correct sensory illusion misconceptions are discussed. School of Education

STEREO/Waves Education and Public Outreach

NASA Astrophysics Data System (ADS)

MacDowall, R. J.; Bougeret, J.; Bale, S. D.; Goetz, K.; Kaiser, M. L.

2005-05-01

We present the education and public outreach plan and activities of the STEREO Waves (aka SWAVES) investigation. SWAVES measures radio emissions from the solar corona, interplanetary medium, and terrestrial magnetosphere, as well as in situ waves in the solar wind. In addition to the web site components that display stereo/multi-spacecraft data in a graphical form and explain the science and instruments, we will focus on the following three areas of EPO: class-room demonstrations using models of the STEREO spacecraft with battery powered radio receivers (and speakers) to illustrate spacecraft radio direction finding, teacher developed and tested class-room activities using SWAVES solar radio observations to motivate geometry and trigonometry, and sound-based delivery of characteristic radio and plasma wave events from the SWAVES web site for accessibility and esthetic reasons. Examples of each element will be demonstrated.

Plasma and radio waves from Neptune: Source mechanisms and propagation

NASA Astrophysics Data System (ADS)

Wong, H. K.

1994-03-01

This report summarizes results obtained through the support of NASA Grant NAGW-2412. The objective of this project is to conduct a comprehensive investigation of the radio wave emission observed by the planetary radio astronomy (PRA) instrument on board Voyager 2 as if flew by Neptune. This study has included data analysis, theoretical and numerical calculations, ray tracing, and modeling to determine the possible source mechanism(s) and locations of the Neptune radio emissions. We have completed four papers, which are included in the appendix. The paper 'Modeling of Whistler Ray Paths in the Magnetosphere of Neptune' investigated the propagation and dispersion of lighting-generated whistler in the magnetosphere of Neptune by using three dimensional ray tracing. The two papers 'Numerical Simulations of Bursty Radio Emissions from Planetary Magnetospheres' and 'Numerical Simulations of Bursty Planetary Radio Emissions' employed numerical simulations to investigate an alternate source mechanism of bursty radio emissions in addition to the cyclotron maser instability. We have also studied the possible generation of Z and whistler mode waves by the temperature anisotropic beam instability and the result was published in 'Electron Cyclotron Wave Generation by Relativistic Electrons.' Besides the aforementioned studies, we have also collaborated with members of the PRA team to investigate various aspects of the radio wave data. Two papers have been submitted for publication and the abstracts of these papers are also listed in the appendix.

Plasma and radio waves from Neptune: Source mechanisms and propagation

NASA Technical Reports Server (NTRS)

Wong, H. K.

1994-01-01

This report summarizes results obtained through the support of NASA Grant NAGW-2412. The objective of this project is to conduct a comprehensive investigation of the radio wave emission observed by the planetary radio astronomy (PRA) instrument on board Voyager 2 as if flew by Neptune. This study has included data analysis, theoretical and numerical calculations, ray tracing, and modeling to determine the possible source mechanism(s) and locations of the Neptune radio emissions. We have completed four papers, which are included in the appendix. The paper 'Modeling of Whistler Ray Paths in the Magnetosphere of Neptune' investigated the propagation and dispersion of lighting-generated whistler in the magnetosphere of Neptune by using three dimensional ray tracing. The two papers 'Numerical Simulations of Bursty Radio Emissions from Planetary Magnetospheres' and 'Numerical Simulations of Bursty Planetary Radio Emissions' employed numerical simulations to investigate an alternate source mechanism of bursty radio emissions in addition to the cyclotron maser instability. We have also studied the possible generation of Z and whistler mode waves by the temperature anisotropic beam instability and the result was published in 'Electron Cyclotron Wave Generation by Relativistic Electrons.' Besides the aforementioned studies, we have also collaborated with members of the PRA team to investigate various aspects of the radio wave data. Two papers have been submitted for publication and the abstracts of these papers are also listed in the appendix.

SOURCE REGIONS OF THE TYPE II RADIO BURST OBSERVED DURING A CME–CME INTERACTION ON 2013 MAY 22

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mäkelä, P.; Reiner, M. J.; Akiyama, S.

2016-08-20

We report on our study of radio source regions during the type II radio burst on 2013 May 22 based on direction-finding analysis of the Wind /WAVES and STEREO /WAVES (SWAVES) radio observations at decameter–hectometric wavelengths. The type II emission showed an enhancement that coincided with the interaction of two coronal mass ejections (CMEs) launched in sequence along closely spaced trajectories. The triangulation of the SWAVES source directions posited the ecliptic projections of the radio sources near the line connecting the Sun and the STEREO-A spacecraft. The WAVES and SWAVES source directions revealed shifts in the latitude of the radiomore » source, indicating that the spatial location of the dominant source of the type II emission varies during the CME–CME interaction. The WAVES source directions close to 1 MHz frequencies matched the location of the leading edge of the primary CME seen in the images of the LASCO/C3 coronagraph. This correspondence of spatial locations at both wavelengths confirms that the CME–CME interaction region is the source of the type II enhancement. Comparison of radio and white-light observations also showed that at lower frequencies scattering significantly affects radio wave propagation.« less

Detection of fundamental and harmonic type III radio emission and the associated Langmuir waves at the source region

NASA Technical Reports Server (NTRS)

Reiner, M. J.; Stone, R. G.; Fainberg, J.

1992-01-01

Type III radio emission generated in the vicinity of the Ulysses spacecraft has been detected at both the fundamental and harmonic of the local plasma frequency. The observations represent the first clear evidence of locally generated type III radio emission. This local emission shows no evidence of frequency drift, exhibits a relatively short rise time, is less intense than the observed remotely generated radio emission, and is temporally correlated with observed in situ Langmuir waves. The observations were made with the unified radio astronomy and wave (URAP) experiment on the Ulysses spacecraft between 1990 November 4 and 1991 April 30, as it traveled from 1 to 3 AU from the sun. During this time period many thousands of bursts were observed. However, only three examples of local emission and associated Langmuir waves were identified. This supports previous suggestions that type III radio emission is generated in localized regions of the interplanetary medium, rather than uniformly along the extent of the electron exciter beam.

Influence of January 2009 stratospheric warming on HF radio wave propagation in the low-latitude ionosphere

NASA Astrophysics Data System (ADS)

Kotova, Darya; Klimenko, Maksim; Klimenko, Vladimir; Zaharov, Veniamin; Bessarab, Fedor; Korenkov, Yuriy

2016-12-01

We have considered the influence of the January 23-27, 2009 sudden stratospheric warming (SSW) event on HF radio wave propagation in the equatorial ionosphere. This event took place during extremely low solar and geomagnetic activity. We use the simulation results obtained with the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) for simulating environmental changes during the SSW event. We both qualitatively and quantitatively reproduced total electron content disturbances obtained from global ground network receiver observations of GPS navigation satellite signals, by setting an additional electric potential and TIME-GCM model output at a height of 80 km. In order to study the influence of this SSW event on HF radio wave propagation and attenuation, we used the numerical model of radio wave propagation based on geometrical optics approximation. It is shown that the sudden stratospheric warming leads to radio signal attenuation and deterioration of radio communication in the daytime equatorial ionosphere.

Radio crickets: chirping jets from black hole binaries entering their gravitational wave inspiral

NASA Astrophysics Data System (ADS)

Kulkarni, Girish; Loeb, Abraham

2016-03-01

We study a novel electromagnetic signature of supermassive black hole (BH) binaries whose inspiral starts being dominated by gravitational wave (GW) emission. Recent simulations suggest that the binary's member BHs can continue to accrete gas from the circumbinary accretion disc in this phase of the binary's evolution, all the way until coalescence. If one of the binary members produces a radio jet as a result of accretion, the jet precesses along a biconical surface due to the binary's orbital motion. When the binary enters the GW phase of its evolution, the opening angle widens, the jet exhibits milliarcsecond-scale wiggles, and the conical surface of jet precession is twisted due to apparent superluminal motion. The rapidly increasing orbital velocity of the binary gives the jet an appearance of a `chirp'. This helical chirping morphology of the jet can be used to infer the binary parameters. For binaries with mass 107-1010 M⊙ at redshifts z < 0.5, monitoring these features in current and archival data will place a lower limit on sources that could be detected by Evolved Laser Interferometer Space Antenna and Pulsar Timing Arrays. In the future, microarcsecond interferometry with the Square Kilometre Array will increase the potential usefulness of this technique.

Antenna Construction & Propagation of Radio Waves, 5-1. Military Curriculum Materials for Vocational and Technical Education.

ERIC Educational Resources Information Center

Marine Corps, Washington, DC.

These military-developed curriculum materials consist of five individualized, self-paced chapters dealing with antenna construction and propagation of radio waves. Covered in the individual lessons are the following topics: basic electricity; antenna transmission-line fundamentals; quarter-wave antennas, half-wave antennas, and associated radio…

Radio Follow-Up of Gravitational-Wave Triggers during Advanced LIGO 01

DOE PAGES

Palliyaguru, N. T.; Corsi, Alessandra; Kasliwal, M. M.; ...

2016-09-28

We present radio follow-up observations carried out with the Karl G. Jansky Very Large Array during the first observing run (O1) of the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO). A total of three gravitational-wave triggers were followed-up during the ≈4 months of O1, from 2015 September to 2016 January. Two of these triggers, GW150914 and GW151226, are binary black hole (BH) merger events of high significance. A third trigger, G194575, was subsequently declared as an event of no interest (i.e., a false alarm). Our observations targeted selected optical transients identified by the intermediate Palomar Transient Factory in the Advanced LIGOmore » error regions of the three triggers, and a limited region of the gravitational-wave localization area of G194575 not accessible to optical telescopes due to Sun constraints, where a possible high-energy transient was identified. No plausible radio counterparts to GW150914 and GW151226 were found, in agreement with expectations for binary BH mergers. We show that combining optical and radio observations is key to identifying contaminating radio sources that may be found in the follow-up of gravitational-wave triggers, such as emission associated with star formation and active galactic nuclei. We discuss our results in the context of the theoretical predictions for radio counterparts to gravitational-wave transients, and describe our future plans for the radio follow-up of Advanced LIGO (and Virgo) triggers.« less

Coronal Mass Ejections (CMEs) and Associated Phenomena

NASA Astrophysics Data System (ADS)

Manoharan, P. K.

2008-10-01

The Sun is the most powerful radio waves emitting object in the sky. The first documented recognition of the reception of radio waves from the Sun was made in 1942 by Hey.15 Since then solar radio observations, from ground-based and space-based instruments, have played a major role in understanding the physics of the Sun and fundamental physical processes of the solar radio emitting phenomena...

Speckles in interstellar radio-wave scattering

NASA Technical Reports Server (NTRS)

Desai, K. M.; Gwinn, C. R.; Reynolds, J.; King, E. A.; Jauncey, D.; Nicholson, G.; Flanagan, C.; Preston, R. A.; Jones, D. L.

1991-01-01

Observations of speckles in the scattering disk of the Vela pulsar are presented and speckle techniques for studying and circumventing scattering of radio waves by the turbulent interstellar plasma are discussed. The speckle pattern contains, in a hologrammatic fashion, complete information on the structure of the radio source as well as the distribution of the scattering material. Speckle observations of interstellar scattering of radio waves are difficult because of their characteristically short timescales and narrow bandwidths. Here, first observations are presented, taken at 13 cm wavelength with elements of the SHEVE VLBI network, of speckles in interstellar scattering.

The ISPM unified radio and plasma wave experiment

NASA Technical Reports Server (NTRS)

Stone, R. G.; Caldwell, J.; Deconchy, Y.; Deschanciaux, C.; Ebbett, R.; Epstein, G.; Groetz, K.; Harvey, C. C.; Hoang, S.; Howard, R.

1983-01-01

Hardware for the International Solar Polar Mission (ISPM) Unified Radio and Plasma (URAP) wave experiment is presented. The URAP determines direction and polarization of distant radio sources for remote sensing of the heliosphere, and studies local wave phenomena which determine the transport coefficients of the ambient plasma. Electric and magnetic field antennas and preamplifiers; the electromagnetic compatibility plan and grounding; radio astronomy and plasma frequency receivers; a fast Fourier transformation data processing unit waveform analyzer; dc voltage measurements; a fast envelope sampler for the solar wind, and plasmas near Jupiter; a sounder; and a power converter are described.

Antenna Construction and Propagation of Radio Waves.

ERIC Educational Resources Information Center

Marine Corps Inst., Washington, DC.

Developed as part of the Marine Corps Institute (MCI) correspondence training program, this course on antenna construction and propagation of radio waves is designed to provide communicators with instructions in the selection and/or construction of the proper antenna(s) for use with current field radio equipment. Introductory materials include…

Well-defined EUV wave associated with a CME-driven shock

NASA Astrophysics Data System (ADS)

Cunha-Silva, R. D.; Selhorst, C. L.; Fernandes, F. C. R.; Oliveira e Silva, A. J.

2018-05-01

Aims: We report on a well-defined EUV wave observed by the Extreme Ultraviolet Imager (EUVI) on board the Solar Terrestrial Relations Observatory (STEREO) and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). The event was accompanied by a shock wave driven by a halo CME observed by the Large Angle and Spectrometric Coronagraph (LASCO-C2/C3) on board the Solar and Heliospheric Observatory (SOHO), as evidenced by the occurrence of type II bursts in the metric and dekameter-hectometric wavelength ranges. We investigated the kinematics of the EUV wave front and the radio source with the purpose of verifying the association between the EUV wave and the shock wave. Methods: The EUV wave fronts were determined from the SDO/AIA images by means of two appropriate directions (slices). The heights (radial propagation) of the EUV wave observed by STEREO/EUVI and of the radio source associated with the shock wave were compared considering the whole bandwidth of the harmonic lane of the radio emission, whereas the speed of the shock was estimated using the lowest frequencies of the harmonic lane associated with the undisturbed corona, using an appropriate multiple of the Newkirk (1961, ApJ, 133, 983) density model and taking into account the H/F frequency ratio fH/fF = 2. The speed of the radio source associated with the interplanetary shock was determined using the Mann et al. (1999, A&A, 348, 614) density model. Results: The EUV wave fronts determined from the SDO/AIA images revealed the coexistence of two types of EUV waves, a fast one with a speed of 560 km s-1, and a slower one with a speed of 250 km s-1, which corresponds approximately to one-third of the average speed of the radio source ( 680 km s-1). The radio signature of the interplanetary shock revealed an almost constant speed of 930 km s-1, consistent with the linear speed of the halo CME (950 km s-1) and with the values found for the accelerating coronal shock ( 535-823 km s-1), taking into account the gap between the radio emissions.

[An encounter with extraterrestrial intelligence].

PubMed

Hisabayashi, Hisashi

2003-12-01

It is much easier to find extraterrestrial intelligence than to detect simple organisms living on other planets. However, it is hard to communicate with such intelligence without the mutual understanding of inter-stellar communication protocol. The radio SETI (The Search for Extra-Terrestrial Intelligence) was initiated with the pioneering work of F. Drake in 1960, one year after the historical SETI paper by Cocconi and Morrison. This talk explains that SETI evolves with two bases of science; the understanding of our universe and the development of technology. Since SETI has had strong connection with radio astronomy from its early beginning, the impacts of radio astronomical findings and technological breakthrough can be seen in many aspects of the SETI history. Topics of this talk include the detection of microwave 3 K background radiation in the universe. Interstellar atomic and molecular lines found in radio-wave spectra provide the evidence of pre-biotic chemical evolution in such region. Radio telescope imaging and spectral technique are closely associated with methodology of SETI. Topics of the talk extend to new Allen Telescope Array and projected Square Kilometer Array. Recent optical SETI and the discoveries of extra solar planets are also explained. In the end, the recent understanding of our universe is briefly introduced in terms of matter, dark matter and dark energy. Even our understanding of the universe has been evolutionarily revolved and accumulated after 1960, we must recognize that our universe is still poorly understood and that astronomy and SETI are required to proceed hand in hand.

Radio triangulation - mapping the 3D position of the solar radio emission

NASA Astrophysics Data System (ADS)

Magdalenic, Jasmina

2016-04-01

Understanding the relative position of the sources of the radio emission and the associated solar eruptive phenomena (CME and the associated shock wave) has always been a challenge. While ground-based radio interferometer observations provide us with the 2D position information for the radio emission originating from the low corona (up to 2.5 Ro), this is not the case for the radio emission originating at larger heights. The radio triangulation measurements (also referred to as direction-finding or goniopolarimetric measurements) from two or more widely separated spacecraft can provide information on the 3D positions of the sources of the radio emission. This type of interplanetary radio observations are currently performed by STEREO WAVES and WIND WAVES instruments, providing a unique possibility for up to three simultaneous radio triangulations (using up to three different pairs of spacecraft). The recent results of the radio triangulation studies bring new insight into the causal relationship of the solar radio emission and CMEs. In this presentation I will discuss some of the most intriguing results on the source positions of: a) type III radio bursts indicating propagation of the fast electrons accelerated along the open field lines, b) type II radio bursts indicating interaction of the CME-driven shocks and other coronal structures e.g. streamers and c) type IV-like radio bursts possibly associated with CME-CME interaction.

Note: A novel method for generating multichannel quasi-square-wave pulses.

PubMed

Mao, C; Zou, X; Wang, X

2015-08-01

A 21-channel quasi-square-wave nanosecond pulse generator was constructed. The generator consists of a high-voltage square-wave pulser and a channel divider. Using an electromagnetic relay as a switch and a 50-Ω polyethylene cable as a pulse forming line, the high-voltage pulser produces a 10-ns square-wave pulse of 1070 V. With a specially designed resistor-cable network, the channel divider divides the high-voltage square-wave pulse into 21 identical 10-ns quasi-square-wave pulses of 51 V, exactly equal to 1070 V/21. The generator can operate not only in a simultaneous mode but also in a delay mode if the cables in the channel divider are different in length.

From Radio to X-rays--Some 'Real' Electrical Applications.

ERIC Educational Resources Information Center

Freeman, J. C.

1986-01-01

Describes practical applications related to X-rays, ultra-violet radiation, light radiation, short-wave infra-red radiation, medium-wave infra-red radiation, long-wave infra-red radiation, microwave radiation, and radio frequency radiation. Suggests that these applications be used during instruction on electricity. (JN)

Plasma and radio waves from Neptune: Source mechamisms and propagation

NASA Technical Reports Server (NTRS)

Menietti, J. Douglas

1994-01-01

The purpose of this project was to conduct a comprehensive investigation of the radio wave emission observed by the planetary radio astronomy (PRA) instrument on board Voyager 2 as it flew by Neptune. The study has included data analysis, theoretical and numerical calculations, and ray tracing to determine the possible source mechanisms and locations of the radiation, including the narrowband bursty and smooth components of the Neptune radio emission.

Comparison of the effects induced by the ordinary (O-mode) and extraordinary (X-mode) polarized powerful HF radio waves in the high-latitude ionospheric F region

NASA Astrophysics Data System (ADS)

Blagoveshchenskaya, N. F.; Borisova, T. D.; Kalishin, A. S.; Kayatkin, V. N.; Yeoman, T. K.; Häggström, I.

2018-01-01

Using the results of coordinated experiments on the modification of the high-latitude ionosphere by powerful HF radio emission of the EISCAT/Heating facility, effects of the impact of powerful HF radio waves of the ordinary (O-mode) and extraordinary (X-mode) polarization on the high-latitude ionospheric F region have been compared. During the experiments, a powerful HF radio wave was emitted in the magnetic zenith direction at frequencies within the 4.5-7.9 MHz range. The effective power of the emission was 150-650 MW. The behavior and characteristics of small-scale artificial ionospheric irregularities (SAIIs) during O- and X-heating at low and high frequencies are considered in detail. A principal difference has been found in the development of the Langmuir and ion-acoustic turbulence (intensified by the heating of the plasma and ion-acoustic lines in the spectrum of the EISCAT radar of incoherent scatter of radio waves) in the O- and X-heating cycles after switching on the heating facility. It has been shown that, under the influence on the ionospheric plasma of a powerful HF radio wave of the X-polarization, intense spectral components in the spectrum of the narrow-band artificial ionospheric radio emission (ARI) were registered at distances on the order of 1200 km from the heating facility.

Simulation and Testing of a Linear Array of Modified Four-Square Feed Antennas for the Tianlai Cylindrical Radio Telescope

NASA Astrophysics Data System (ADS)

Cianciara, Aleksander J.; Anderson, Christopher J.; Chen, Xuelei; Chen, Zhiping; Geng, Jingchao; Li, Jixia; Liu, Chao; Liu, Tao; Lu, Wing; Peterson, Jeffrey B.; Shi, Huli; Steffel, Catherine N.; Stebbins, Albert; Stucky, Thomas; Sun, Shijie; Timbie, Peter T.; Wang, Yougang; Wu, Fengquan; Zhang, Juyong

A wide bandwidth, dual polarized, modified four-square antenna is presented as a feed antenna for radio astronomical measurements. A linear array of these antennas is used as a line-feed for cylindrical reflectors for Tianlai, a radio interferometer designed for 21cm intensity mapping. Simulations of the feed antenna beam patterns and scattering parameters are compared to experimental results at multiple frequencies across the 650-1420MHz range. Simulations of the beam patterns of the combined feed array/reflector are presented as well.

Extragalactic radio surveys in the pre-Square Kilometre Array era

PubMed Central

2017-01-01

The era of the Square Kilometre Array is almost upon us, and pathfinder telescopes are already in operation. This brief review summarizes our current knowledge of extragalactic radio sources, accumulated through six decades of continuum surveys at the low-frequency end of the electromagnetic spectrum and the extensive complementary observations at other wavelengths necessary to gain this understanding. The relationships between radio survey data and surveys at other wavelengths are discussed. Some of the outstanding questions are identified and prospects over the next few years are outlined. PMID:28791175

BioRadioTransmitter: a self-powered wireless glucose-sensing system.

PubMed

Hanashi, Takuya; Yamazaki, Tomohiko; Tsugawa, Wakako; Ikebukuro, Kazunori; Sode, Koji

2011-09-01

Although an enzyme fuel cell can be utilized as a glucose sensor, the output power generated is too low to power a device such as a currently available transmitter and operating system, and an external power source is required for operating an enzyme-fuel-cell-based biosensing system. We proposed a novel biosensor that we named BioCapacitor, in which a capacitor serves as a transducer. In this study, we constructed a new BioCapacitor-based system with an added radio-transmitter circuit and a miniaturized enzyme fuel cell. A miniaturized direct-electron-transfer-type compartmentless enzyme fuel cell was constructed with flavin adenine dinucleotide-dependent glucose dehydrogenase complex-based anode and a bilirubin-oxidase-based cathode. For construction of a BioRadioTransmitter wireless sensing system, a capacitor, an ultra-low-voltage charge-pump-integrated circuit, and Hartley oscillator circuit were connected to the miniaturized enzyme fuel cell. A radio-receiver circuit, comprising two field-effect transistors and a coil as an antenna, was used to amplify the signal generated from the biofuel cells. Radio wave signals generated by the BioRadioTransmitter were received, amplified, and converted from alternate to direct current by the radio receiver. When the capacitor discharges in the presence of glucose, the BioRadioTransmitter generates a radio wave, which is monitored by a radio receiver connected wirelessly to the sensing device. Magnitude of the radio wave transmission frequency change observed at the radio receiver was correlated to glucose concentration in the fuel cells. We constructed a stand-alone, self-powered, wireless glucose-sensing system called a BioRadioTransmitter by using a radio transmitter in which the radio wave transmission frequency changes with the glucose concentration in the fuel cell. The BioRadioTransmitter is a significant advance toward construction of an implantable continuous glucose monitor. © 2011 Diabetes Technology Society.

Generation of Artificial Ionospheric Irregularities in the Midlatitude Ionosphere Modified by High-Power High-Frequency X-Mode Radio Waves

NASA Astrophysics Data System (ADS)

Frolov, V. L.; Bolotin, I. A.; Komrakov, G. P.; Pershin, A. V.; Vertogradov, G. G.; Vertogradov, V. G.; Vertogradova, E. G.; Kunitsyn, V. E.; Padokhin, A. M.; Kurbatov, G. A.; Akchurin, A. D.; Zykov, E. Yu.

2014-11-01

We consider the properties of the artificial ionospheric irregularities excited in the ionospheric F 2 region modified by high-power high-frequency X-mode radio waves. It is shown that small-scale (decameter) irregularities are not generated in the midlatitude ionosphere. The intensity of irregularities with the scales l ⊥ ≈50 m to 3 km is severalfold weaker compared with the case where the irregularities are excited by high-power O-mode radio waves. The intensity of the larger-scale irregularities is even stronger attenuated. It is found that the generation of large-scale ( l ⊥ ≈5-10 km) artificial ionospheric irregularities is enhanced at the edge of the directivity pattern of a beam of high-power radio waves.

Strongly lensed neutral hydrogen emission: detection predictions with current and future radio interferometers

NASA Astrophysics Data System (ADS)

Deane, R. P.; Obreschkow, D.; Heywood, I.

2015-09-01

Strong gravitational lensing provides some of the deepest views of the Universe, enabling studies of high-redshift galaxies only possible with next-generation facilities without the lensing phenomenon. To date, 21-cm radio emission from neutral hydrogen has only been detected directly out to z ˜ 0.2, limited by the sensitivity and instantaneous bandwidth of current radio telescopes. We discuss how current and future radio interferometers such as the Square Kilometre Array (SKA) will detect lensed H I emission in individual galaxies at high redshift. Our calculations rely on a semi-analytic galaxy simulation with realistic H I discs (by size, density profile and rotation), in a cosmological context, combined with general relativistic ray tracing. Wide-field, blind H I surveys with the SKA are predicted to be efficient at discovering lensed H I systems, increasingly so at z ≳ 2. This will be enabled by the combination of the magnification boosts, the steepness of the H I luminosity function at the high-mass end, and the fact that the H I spectral line is relatively isolated in frequency. These surveys will simultaneously provide a new technique for foreground lens selection and yield the highest redshift H I emission detections. More near term (and existing) cm-wave facilities will push the high-redshift H I envelope through targeted surveys of known lenses.

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

Synopsis of Mid-latitude Radio Wave Absorption in Europe

NASA Technical Reports Server (NTRS)

Torkar, K. M.; Friedrich, M.

1984-01-01

Radio wave absorption data covering almost two years from Europe to Central Asia are presented. They are normalized by relating them to a reference absorption. Every day these normalized data are fitted to a mathematical function of geographical location in order to obtain a daily synopsis of radio wave absorption. A film of these absorption charts was made which is intended to reveal movements of absorption or absorption anomaly. In addition, radiance (temperature) data from the lower D-region are also plotted onto these charts.

Observation of radio-wave-induced red hydroxyl emission at low altitude in the ionosphere.

PubMed

Kagan, L M; Nicolls, M J; Kelley, M C; Carlson, H C; Belikovich, V V; Bakhmet'eva, N V; Komrakov, G P; Trondsen, T S; Donovan, E

2005-03-11

We report the discovery of radio-wave-induced red emission of OH Meinel rotation-vibrational bands at 629.79 nm. These are the first measurements of artificial aurora below 100 km. We believe that the 629.79-nm OH emission was due to radio-wave focusing by sporadic ionization clouds near 80-85 km altitude, thus giving a technique to visualize the low-altitude sporadic ionization and providing insight into ionospheric interactions at these low altitudes.

SQUARE WAVE AMPLIFIER

DOEpatents

Leavitt, M.A.; Lutz, I.C.

1958-08-01

An amplifier circuit is described for amplifying sigmals having an alternating current component superimposed upon a direct current component, without loss of any segnnent of the alternating current component. The general circuit arrangement includes a vibrator, two square wave amplifiers, and recombination means. The amplifier input is connected to the vibrating element of the vibrator and is thereby alternately applied to the input of each square wave amplifier. The detailed circuitry of the recombination means constitutes the novelty of the annplifier and consists of a separate, dual triode amplifier coupled to the output of each square wave amplifier with a recombination connection from the plate of one amplifier section to a grid of one section of the other amplifier. The recombination circuit has provisions for correcting distortion caused by overlapping of the two square wave voltages from the square wave amplifiers.

Put a Short-Wave Radio in Your Foreign Language Classroom

ERIC Educational Resources Information Center

Oksenholt, Svein

1977-01-01

Advantages of the short-wave radio as a supplement to foreign language instruction as well as practical hints on wavelength, antenna, and techniques for use are provided. Selective annotated bibliography. (STS)

Reconfigurable Wideband Circularly Polarized Stacked Square Patch Antenna for Cognitive Radios

NASA Technical Reports Server (NTRS)

Barbosa Kortright, Miguel A.; Waldstein, Seth W.; Simons, Rainee N.

2017-01-01

An almost square patch and a square patch with corner truncation for circularly polarized (CP) and a stacked CP square patch are researched and developed at X-band for cognitive devices. A draft set of presentation charts are attached.

Comet encke: radar detection of nucleus.

PubMed

Kamoun, P G; Campbell, D B; Ostro, S J; Pettengill, G H; Shapiro, I I

1982-04-16

The nucleus of the periodic comet Encke was detected in November 1980 with the Arecibo Observatory's radar system (wavelength, 12.6 centimeters). The echoes in the one sense of circular polarization received imply a radar cross section of 1.1 +/- 0.7 square kilometers. The estimated bandwidth of these echoes combined with an estimate of the rotation vector of Encke yields a radius for the nucleus of l.5(+2.3)(-1.0) kilometers. The uncertainties given are dependent primarily on the range of models considered for the comet and for the manner in which its nucleus backscatters radio waves. Should this range prove inadequate, the true value of the radius of the nucleus might lie outside the limits given.

Chaotic ultra-wideband radio generator based on an optoelectronic oscillator with a built-in microwave photonic filter.

PubMed

Wang, Li Xian; Zhu, Ning Hua; Zheng, Jian Yu; Liu, Jian Guo; Li, Wei

2012-05-20

We induce a microwave photonic bandpass filter into an optoelectronic oscillator to generate a chaotic ultra-wideband signal in both the optical and electrical domain. The theoretical analysis and numerical simulation indicate that this system is capable of generating band-limited high-dimensional chaos. Experimental results coincide well with the theoretical prediction and show that the power spectrum of the generated chaotic signal basically meets the Federal Communications Commission indoor mask. The generated chaotic carrier is further intensity modulated by a 10 MHz square wave, and the waveform of the output ultra-wideband signal is measured for demonstrating the chaotic on-off keying modulation.

Radio Wave Generation by a Collision or Contact between Various Materials

NASA Astrophysics Data System (ADS)

Takano, T.; Hanawa, R.; Saegusa, K.; Ikeda, H.

2014-12-01

In fracture of rock, radio wave emission was found experimentally [1]. This phenomenon could be used to detect a rock fracture during an earthquake or a volcanic activity [2]. The cause of the radio wave is expected to be micro-discharges, which are generated by an inhomogeneous potential distribution around micro-cracks. In order to better understand the phenomena and clarify the cause of radio wave emission, we carried out experiments to detect the emission in the cases of a collision or contact between various materials. We used receiving systems with great sensitivities and sufficient frequency bandwidths at 1 MHz-, 300 MHz-, 2 GHz-, and 18 GHz-bands. The specimen materials are as follows: Steel (2) Brass (3) Copper (4)Small coin (5)Celluloid. We obtained the following results: The signal was detected for the specimen of (1) to (4), but not for (5). The signal is composed of intermittent spikes which include waves with a frequency close to the center frequency of each frequency band. The power is strongest at the lower frequencies among all frequency bands. The more details will be given in the presentation. The origin of radio wave emission from the metal is supposed to be discharges between materials in these experiments. It is surprising that even a small coin can generate a significant amount of radio wave. Accordingly, it is inferred that all amount of charges are discharged through a conductive metal. On the other hand, celluloid did not generate radio wave, though the specimen was sufficiently charged by brushing. It is inferred that a quite localized charge was discharged but the remaining charges were blocked due to poor conductivity. Extending this hypothesis, large-scale contact should have occurred between broken fragments for the radio wave generation in the aforementioned rock fracture experiments. Turbulence of the fragments is a candidate for the explanation. [1] K. Maki et al., "An experimental study of microwave emission from compression failure of rocks" (in Japanese), Jour. of the Seismological Society of Japan, vol.58, no.4, pp.375-384, 2006.[2] T. Takano al., "Detection of microwave emission due to rock fracture as a new tool for geophysics: A field test at a volcano in Miyake Island, Japan", Journal of Applied Geophysics, 94, pp.1-14, 2013.

1.9 μm square-wave passively Q-witched mode-locked fiber laser.

PubMed

Ma, Wanzhuo; Wang, Tianshu; Su, Qingchao; Wang, Furen; Zhang, Jing; Wang, Chengbo; Jiang, Huilin

2018-05-14

We propose and demonstrate the operation of Q-switched mode-locked square-wave pulses in a thulium-holmium co-doped fiber laser. By using a nonlinear amplifying loop mirror, continuous square-wave dissipative soliton resonance pulse is obtained with 4.4 MHz repetition rate. With the increasing pump power, square-wave pulse duration can be broadened from 1.7 ns to 3.2 ns. On such basis Q-switched mode-locked operation is achieved by properly setting the pump power and the polarization controllers. The internal mode-locked pulses in Q-switched envelope still keep square-wave type. The Q-switched repetition rate can be varied from 41.6 kHz to 74 kHz by increasing pump power. The corresponding average single-pulse energy increases from 2.67 nJ to 5.2 nJ. The average peak power is also improved from 0.6 W to 1.1 W when continuous square-wave operation is changed into Q-switched mode-locked operation. It indicates that Q-switched mode-locked operation is an effective method to increase the square-wave pulse energy and peak power.

Kinetic Simulations of Type II Radio Burst Emission Processes

NASA Astrophysics Data System (ADS)

Ganse, U.; Spanier, F. A.; Vainio, R. O.

2011-12-01

The fundamental emission process of Type II Radio Bursts has been under discussion for many decades. While analytic deliberations point to three wave interaction as the source for fundamental and harmonic radio emissions, sparse in-situ observational data and high computational demands for kinetic simulations have not allowed for a definite conclusion to be reached. A popular model puts the radio emission into the foreshock region of a coronal mass ejection's shock front, where shock drift acceleration can create eletrcon beam populations in the otherwise quiescent foreshock plasma. Beam-driven instabilities are then assumed to create waves, forming the starting point of three wave interaction processes. Using our kinetic particle-in-cell code, we have studied a number of emission scenarios based on electron beam populations in a CME foreshock, with focus on wave-interaction microphysics on kinetic scales. The self-consistent, fully kinetic simulations with completely physical mass-ratio show fundamental and harmonic emission of transverse electromagnetic waves and allow for detailled statistical analysis of all contributing wavemodes and their couplings.

A Millimeter-Wave Digital Link for Wireless MRI

PubMed Central

Aggarwal, Kamal; Joshi, Kiran R.; Rajavi, Yashar; Taghivand, Mazhareddin; Pauly, John M.; Poon, Ada S. Y.; Scott, Greig

2017-01-01

A millimeter (mm) wave radio is presented in this work to support wireless MRI data transmission. High path loss and availability of wide bandwidth make mm-waves an ideal candidate for short range, high data rata communication required for wireless MRI. The proposed system uses a custom designed integrated chip (IC) mm-wave radio with 60 GHz as radio frequency carrier. In this work, we assess performance in a 1.5 T MRI field, with the addition of optical links between the console room and magnet. The system uses ON-OFF keying (OOK) modulation for data transmission and supports data rates from 200 Mb/s to 2.5 Gb/s for distances up-to 65 cm. The presence of highly directional, linearly polarized, on-chip dipole antennas on the mm-wave radio along with the time division multiplexing (TDM) circuitry allows multiple wireless links to be created simultaneously with minimal inter-channel interference. This leads to a highly scalable solution for wireless MRI. PMID:27810803

A Millimeter-Wave Digital Link for Wireless MRI.

PubMed

Aggarwal, Kamal; Joshi, Kiran R; Rajavi, Yashar; Taghivand, Mazhareddin; Pauly, John M; Poon, Ada S Y; Scott, Greig

2017-02-01

A millimeter (mm) wave radio is presented in this work to support wireless MRI data transmission. High path loss and availability of wide bandwidth make mm-waves an ideal candidate for short range, high data rata communication required for wireless MRI. The proposed system uses a custom designed integrated chip (IC) mm-wave radio with 60 GHz as radio frequency carrier. In this work, we assess performance in a 1.5 T MRI field, with the addition of optical links between the console room and magnet. The system uses ON-OFF keying (OOK) modulation for data transmission and supports data rates from 200 Mb/s to 2.5 Gb/s for distances up-to 65 cm. The presence of highly directional, linearly polarized, on-chip dipole antennas on the mm-wave radio along with the time division multiplexing (TDM) circuitry allows multiple wireless links to be created simultaneously with minimal inter-channel interference. This leads to a highly scalable solution for wireless MRI.

Digital Beamforming Interferometry

NASA Technical Reports Server (NTRS)

Rincon, Rafael F. (Inventor)

2016-01-01

Airborne or spaceborne Syntheic Aperture Radar (SAR) can be used in a variety of ways, and is often used to generate two dimensional images of a surface. SAR involves the use of radio waves to determine presence, properties, and features of extended areas. Specifically, radio waves are 10 transmitted in the presence of a ground surface. A portion of the radio wave's energy is reflected back to the radar system, which allows the radar system to detect and image the surface. Such radar systems may be used in science applications, military contexts, and other commercial applications.

Effect exerted by a radio wave electromagnetic field on the rheological properties of water and portland-cement systems

NASA Astrophysics Data System (ADS)

Azharonok, V. V.; Belous, N. Kh.; Rodtsevich, S. P.; Koshevar, V. D.; Shkadretsova, V. G.; Goncharik, S. V.; Chubrik, N. I.; Orlovich, A. I.

2013-09-01

We have studied the effect of the regimes of high-frequency (radio wave) electromagnetic treatment of gauging water on the process of structurization and on the technological characteristics of portland-cement systems. It has been established that the radio wave electromagnetic activation of water leads to a reduction in its surface tension, dynamic viscosity, and shear stress, as well as intensifies the formation of coagulation structures in a portlandcement slurry and aids in increasing the mobility of cement-sand mixtures.

47 CFR 2.1 - Terms and definitions.

Code of Federal Regulations, 2013 CFR

2013-10-01

... radiocommunication services or the radio astronomy service under specified conditions. This term shall also be... another surface. (RR) Radio Astronomy. Astronomy based on the reception of radio waves of cosmic origin. (RR) Radio Astronomy Service. A service involving the use of radio astronomy. (RR) Radio Astronomy...

47 CFR 2.1 - Terms and definitions.

Code of Federal Regulations, 2014 CFR

2014-10-01

... radiocommunication services or the radio astronomy service under specified conditions. This term shall also be... another surface. (RR) Radio Astronomy. Astronomy based on the reception of radio waves of cosmic origin. (RR) Radio Astronomy Service. A service involving the use of radio astronomy. (RR) Radio Astronomy...

Space Weather Research in the Equatorial Region: A Philosophical Reinforcement

NASA Astrophysics Data System (ADS)

Chukwuma, Victor; Odunaike, Rasaki; Laoye, John

Investigations using radio waves reflected from the ionosphere, at high-and mid-latitudes indicate that ionospheric absorption can strongly increase following geomagnetic storms; which appears to suggest some definite relationship between ionospheric radio wave absorption and geomagnetic storms at these latitudes. However, corresponding earlier studies in the equatorial region did not appear to show any explicit relationship between ionospheric radio wave absorption and geomagnetic storm activity. This position appeared acceptable to the existing scientific paradigm, until in an act of paradigm shift, by a change of storm selection criteria, some more recent space weather investigations in the low latitudes showed that ionospheric radio wave absorption in the equatorial region clearly increases after intense storms. Given that these results in the equatorial region stood against the earlier results, this paper presently attempts to highlight their philosophical underpinning and posit that they constitute a scientific statement.

Array analysis of electromagnetic radiation from radio transmitters for submarine communication

NASA Astrophysics Data System (ADS)

Füllekrug, Martin; Mezentsev, Andrew; Watson, Robert; Gaffet, Stéphane; Astin, Ivan; Evans, Adrian

2014-12-01

The array analyses used for seismic and infrasound research are adapted and applied here to the electromagnetic radiation from radio transmitters for submarine communication. It is found that the array analysis enables a determination of the slowness and the arrival azimuth of the wave number vectors associated with the electromagnetic radiation. The array analysis is applied to measurements of ˜20-24 kHz radio waves from transmitters for submarine communication with an array of 10 radio receivers distributed over an area of ˜1 km ×1 km. The observed slowness of the observed wave number vectors range from ˜2.7 ns/m to ˜4.1 ns/m, and the deviations between the expected arrival azimuths and the observed arrival azimuths range from ˜-9.7° to ˜14.5°. The experimental results suggest that it is possible to determine the locations of radio sources from transient luminous events above thunderclouds with an array of radio receivers toward detailed investigations of the electromagnetic radiation from sprites.

Multi-Band (K- Q- and E-Band) Multi-Tone Millimeter-Wave Frequency Synthesizer for Radio Wave Propagation Studies

NASA Technical Reports Server (NTRS)

Simons, Rainee N.; Wintucky, Edwin G.

2014-01-01

This paper presents the design and test results of a multi-band multi-tone millimeter-wave frequency synthesizer, based on a solid-state frequency comb generator. The intended application of the synthesizer is in a space-borne transmitter for radio wave atmospheric studies at K-band (18 to 26.5 GHz), Q-band (37 to 42 GHz), and E-band (71 to 76 GHz). These studies would enable the design of robust multi-Gbps data rate space-to-ground satellite communication links. Lastly, the architecture for a compact multi-tone beacon transmitter, which includes a high frequency synthesizer, a polarizer, and a conical horn antenna, has been investigated for a notional CubeSat based space-to-ground radio wave propagation experiment.

10 GHz Standing-Wave Coplanar Stripline on LiNbO3 Crystal for Radio to Optical-Wave Conversion

NASA Astrophysics Data System (ADS)

Darwis, F.; Wijayanto, Y. N.; Setiawan, A.; Mahmudin, D.; Rahman, A. N.; Daud, P.

2018-04-01

Recently, X-band radar systems are used widely for surveillance and navigation applications. Especially in archipelago or maritime country, the surveillance/navigation radar systems are required to monitoring critical areas and managing marine traffic. Accurate detection and fast analysis should be improved furthermore to provide security and safety condition. Therefore, several radar systems should be installed in many places to coverage the critical areas within radar networks. The radar network can be connected using optical fibers since it has extremely low propagation loss with optical-wave to carry-out the radar-wave. One important component in the scenario is a radio to optical-wave conversion component. In this paper, we report a 10 GHz radio to optical-wave conversion component using standing-wave coplanar stripline (CPS) on LiNbO3 optical crystal as the substrate. The standing-wave CPS electrodes with narrow slot are arranged in an array structure. An optical waveguide is located close to the narrow slot. The CPS electrodes were analysed using electromagnetic analysis software for 10 GHz operational frequency. Responses for slot width and electrode length variation are reported. As results, return loss of -14.580 dB and -19.517 dB are obtained for single and array CPS electrodes respectively. Optimization of the designed radio to optical-wave conversion devices was also done.

Information Content in Radio Waves: Student Investigations in Radio Science

NASA Astrophysics Data System (ADS)

Jacobs, K.; Scaduto, T.

2013-12-01

We describe an inquiry-based instructional unit on information content in radio waves, created in the summer of 2013 as part of a MIT Haystack Observatory (Westford, MA) NSF Research Experiences for Teachers (RET) program. This topic is current and highly relevant, addressing science and technical aspects from radio astronomy, geodesy, and atmospheric research areas as well as Next Generation Science Standards (NGSS). Projects and activities range from simple classroom demonstrations and group investigations, to long term research projects incorporating data acquisition from both student-built instrumentation as well as online databases. Each of the core lessons is applied to one of the primary research centers at Haystack through an inquiry project that builds on previously developed units through the MIT Haystack RET program. In radio astronomy, students investigate the application of a simple and inexpensive software defined radio chip (RTL-SDR) for use in systems implementing a small and very small radio telescope (SRT and VSRT). Both of these systems allow students to explore fundamental principles of radio waves and interferometry as applied to radio astronomy. In ionospheric research, students track solar storms from the initial coronal mass ejection (using Solar Dynamics Observatory images) to the resulting variability in total electron density concentrations using data from the community standard Madrigal distributed database system maintained by MIT Haystack. Finally, students get to explore very long-baseline interferometry as it is used in geodetic studies by measuring crustal plate displacements over time. Alignment to NextGen standards is provided for each lesson and activity with emphasis on HS-PS4 'Waves and Their Applications in Technologies for Information Transfer'.

Autonomous Warplanes: NASA Rovers Lead the Way

DTIC Science & Technology

2016-04-01

communications over long distances. Radio waves do not arrive instantaneously although they travel though space at the speed of light. While the...such as radio frequency interference, thunderstorms near the satellite ground station, solar flares and charged particle events in space, and poor...satellite communications but to an even greater ex- tent. While the speed of light, and thus radio waves, does not contribute significantly to the latency

Ulysses radio and plasma wave observations in the Jupiter environment

NASA Technical Reports Server (NTRS)

Stone, R. G.; Pedersen, B. M.; Harvey, C. C.; Canu, P.; Cornilleau-Wehrlin, N.; Desch, M. D.; De Villedary, C.; Fainberg, J.; Farrell, W. M.; Goetz, K.

1992-01-01

The Unified Radio and Plasma Wave (URAP) experiment has produced new observations of the Jupiter environment, owing to the unique capabilities of the instrument and the traversal of high Jovian latitudes. Broad-band continuum radio emission from Jupiter and in situ plasma waves have proved valuable in delineating the magnetospheric boundaries. Simultaneous measurements of electric and magnetic wave fields have yielded new evidence of whistler-mode radiation within the magnetosphere. Observations of auroral-like hiss provided evidence of a Jovian cusp. The source direction and polarization capabilities of URAP have demonstrated that the outer region of the Io plasma torus supported at least five separate radio sources that reoccurred during successive rotations with a measurable corotation lag. Thermal noise measurements of the Io torus densities yielded values in the densest portion that are similar to models suggested on the basis of Voyager observations of 13 years ago. The URAP measurements also suggest complex beaming and polarization characteristics of Jovian radio components. In addition, a new class of kilometer-wavelength striated Jovian bursts has been observed.

System and method for phase retrieval for radio telescope and antenna control

NASA Technical Reports Server (NTRS)

Dean, Bruce H. (Inventor)

2013-01-01

Disclosed herein are systems, methods, and non-transitory computer-readable storage media for radio phase retrieval. A system practicing the method gathers first data from radio waves associated with an object observed via a first aperture, gathers second data from radio waves associated with the object observed via an introduced second aperture associated with the first aperture, generates reduced noise data by incoherently subtracting the second data from the first data, and performs phase retrieval for the radio waves by modeling the reduced noise data using a single Fourier transform. The first and second apertures are at different positions, such as side by side. This approach can include determining a value Q which represents a ratio of wavelength times a focal ratio divided by pixel spacing. This information can be used to accurately measure and correct alignment errors or other optical system flaws in the apertures.

Searching for Fast Radio Bursts with the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO)

NASA Astrophysics Data System (ADS)

Fisher, Ryan Patrick; Hughey, Brennan; Howell, Eric; LIGO Collaboration

2018-01-01

Although Fast Radio Bursts (FRB) are being detected with increasing frequency, their progenitor systems are still mostly a mystery. We present the plan to conduct targeted searches for gravitational-wave counterparts to these FRB events in the data from the first and second observing runs of the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO).

Waves in Space Plasmas (WISP)

NASA Technical Reports Server (NTRS)

Calvert, Wynne

1994-01-01

Activities under this project have included participation in the Waves in Space Plasmas (WISP) program, a study of the data processing requirements for WISP, and theoretical studies of radio sounding, ducting, and magnetoionic theory. An analysis of radio sounding in the magnetosphere was prepared.

Unprecedentedly Strong and Narrow Electromagnetic Emissions Stimulated by High-Frequency Radio Waves in the Ionosphere

DOE Office of Scientific and Technical Information (OSTI.GOV)

Norin, L.; Leyser, T. B.; Nordblad, E.

2009-02-13

Experimental results of secondary electromagnetic radiation, stimulated by high-frequency radio waves irradiating the ionosphere, are reported. We have observed emission peaks, shifted in frequency up to a few tens of Hertz from radio waves transmitted at several megahertz. These emission peaks are by far the strongest spectral features of secondary radiation that have been reported. The emissions are attributed to stimulated Brillouin scattering, long predicted but hitherto never unambiguously identified in high-frequency ionospheric interaction experiments. The experiments were performed at the High-Frequency Active Auroral Research Program (HAARP), Alaska, USA.

Unprecedentedly strong and narrow electromagnetic emissions stimulated by high-frequency radio waves in the ionosphere.

PubMed

Norin, L; Leyser, T B; Nordblad, E; Thidé, B; McCarrick, M

2009-02-13

Experimental results of secondary electromagnetic radiation, stimulated by high-frequency radio waves irradiating the ionosphere, are reported. We have observed emission peaks, shifted in frequency up to a few tens of Hertz from radio waves transmitted at several megahertz. These emission peaks are by far the strongest spectral features of secondary radiation that have been reported. The emissions are attributed to stimulated Brillouin scattering, long predicted but hitherto never unambiguously identified in high-frequency ionospheric interaction experiments. The experiments were performed at the High-Frequency Active Auroral Research Program (HAARP), Alaska, USA.

Simple surgical approach with high-frequency radio-wave electrosurgery for conjunctivochalasis.

PubMed

Youm, Dong Ju; Kim, Joon Mo; Choi, Chul Young

2010-11-01

To introduce a new simple surgical approach with high-frequency radio-wave electrosurgery to reduce conjunctivochalasis (CCh). Prospective, noncomparative, interventional case series analysis. Twelve patients (20 eyes) with CCh were recruited from the outpatient service of the Department of Ophthalmology, Kangbuk Samsung Hospital, Seoul, Korea. On the inferior bulbar conjunctiva, subconjunctival coagulation was performed with a fine-needle electrode using a high-frequency radio-wave electrosurgical unit (Ellman Surgitron; Ellman International, Inc., Hewlett, NY) in coagulation mode. Conjunctivochalasis grade; epiphora and dry eye symptoms (the Ocular Surface Disease Index [OSDI]; Allergan Inc., Irvine, CA, holds the copyright); and intraoperative and postoperative complications. Eighteen eyes (90%) recovered a smooth, wet, and noninflamed conjunctival surface within 1 month and remained stable for a follow-up period of 3 months. At 3 months postoperatively, 18 eyes (90%) had grade 0 CCh. There was a statistically significant decrease of the OSDI score at 3 months postoperatively (P < 0.001). A surgical approach with high-frequency radio-wave electrosurgery produced a significant reduction in CCh and an improvement in symptoms. Radio-wave surgical techniques represent a favorable alternative to surgical treatment of CCh. The author(s) have no proprietary or commercial interest in any materials discussed in this article. Copyright © 2010 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.

Simulation-Based Approach to Determining Electron Transfer Rates Using Square-Wave Voltammetry.

PubMed

Dauphin-Ducharme, Philippe; Arroyo-Currás, Netzahualcóyotl; Kurnik, Martin; Ortega, Gabriel; Li, Hui; Plaxco, Kevin W

2017-05-09

The efficiency with which square-wave voltammetry differentiates faradic and charging currents makes it a particularly sensitive electroanalytical approach, as evidenced by its ability to measure nanomolar or even picomolar concentrations of electroactive analytes. Because of the relative complexity of the potential sweep it uses, however, the extraction of detailed kinetic and mechanistic information from square-wave data remains challenging. In response, we demonstrate here a numerical approach by which square-wave data can be used to determine electron transfer rates. Specifically, we have developed a numerical approach in which we model the height and the shape of voltammograms collected over a range of square-wave frequencies and amplitudes to simulated voltammograms as functions of the heterogeneous rate constant and the electron transfer coefficient. As validation of the approach, we have used it to determine electron transfer kinetics in both freely diffusing and diffusionless surface-tethered species, obtaining electron transfer kinetics in all cases in good agreement with values derived using non-square-wave methods.

Synchronization of tunable asymmetric square-wave pulses in delay-coupled optoelectronic oscillators.

PubMed

Martínez-Llinàs, Jade; Colet, Pere; Erneux, Thomas

2015-03-01

We consider a model for two delay-coupled optoelectronic oscillators under positive delayed feedback as prototypical to study the conditions for synchronization of asymmetric square-wave oscillations, for which the duty cycle is not half of the period. We show that the scenario arising for positive feedback is much richer than with negative feedback. First, it allows for the coexistence of multiple in- and out-of-phase asymmetric periodic square waves for the same parameter values. Second, it is tunable: The period of all the square-wave periodic pulses can be tuned with the ratio of the delays, and the duty cycle of the asymmetric square waves can be changed with the offset phase while the total period remains constant. Finally, in addition to the multiple in- and out-of-phase periodic square waves, low-frequency periodic asymmetric solutions oscillating in phase may coexist for the same values of the parameters. Our analytical results are in agreement with numerical simulations and bifurcation diagrams obtained by using continuation techniques.

Fast radio burst tied to distant dwarf galaxy (Image 2)

NSF Multimedia

2017-06-07

Radio telescope at Arecibo only localized the fast radio burst to the area inside the two circles in this image, but the Very Large Array was able to pinpoint it as a dwarf galaxy within the square (shown at intersection of cross hairs in enlarged box)

MeerLICHT and BlackGEM: custom-built telescopes to detect faint optical transients

NASA Astrophysics Data System (ADS)

Bloemen, Steven; Groot, Paul; Woudt, Patrick; Klein Wolt, Marc; McBride, Vanessa; Nelemans, Gijs; Körding, Elmar; Pretorius, Margaretha L.; Roelfsema, Ronald; Bettonvil, Felix; Balster, Harry; Bakker, Roy; Dolron, Peter; van Elteren, Arjen; Elswijk, Eddy; Engels, Arno; Fender, Rob; Fokker, Marc; de Haan, Menno; Hagoort, Klaas; de Hoog, Jasper; ter Horst, Rik; van der Kevie, Giel; Kozłowski, Stanisław; Kragt, Jan; Lech, Grzegorz; Le Poole, Rudolf; Lesman, Dirk; Morren, Johan; Navarro, Ramon; Paalberends, Willem-Jelle; Paterson, Kerry; Pawłaszek, Rafal; Pessemier, Wim; Raskin, Gert; Rutten, Harrie; Scheers, Bart; Schuil, Menno; Sybilski, Piotr W.

2016-07-01

We present the MeerLICHT and BlackGEM telescopes, which are wide-field optical telescopes that are currently being built to study transient phenomena, gravitational wave counterparts and variable stars. The telescopes have 65 cm primary mirrors and a 2.7 square degree field-of-view. The MeerLICHT and BlackGEM projects have different science goals, but will use identical telescopes. The first telescope, MeerLICHT, will be commissioned at Sutherland (South Africa) in the first quarter of 2017. It will co-point with MeerKAT to collect optical data commensurate with the radio observations. After careful analysis of MeerLICHT's performance, three telescopes of the same type will be commissioned in La Silla (Chile) in 2018 to form phase I of the BlackGEM array. BlackGEM aims at detecting and characterizing optical counterparts of gravitational wave events detected by Advanced LIGO and Virgo. In this contribution we present an overview of the science goals, the design and the status of the two projects.

Jupiter plasma wave observations: an initial voyager 1 overview.

PubMed

Scarf, F L; Gurnett, D A; Kurth, W S

1979-06-01

The Voyager I plasma wave instrument detected low-frequency radio emissions, ion acoustic waves, and electron plasma oscillations for a period of months before encountering Jupiter's bow shock. In the outer magnetosphere, measurements of trapped radio waves were used to derive an electron density profile. Near and within the Io plasma torus the instrument detected high-frequency electrostatic waves, strong whistler mode turbulence, and discrete whistlers, apparently associated with lightning. Some strong emissions in the tail region and some impulsive signals have not yet been positively identified.

Waves in the middle and upper atmosphere of Mars as seen by the Radio Science Experiment MaRS on Mars Express

NASA Astrophysics Data System (ADS)

Tellmann, S.; Paetzold, M.; Häusler, B.; Hinson, D. P.; Peter, K.; Tyler, G. L.

2017-12-01

Atmospheric waves play a crucial role in the Martian atmosphere. They are responsible for the redistribution of momentum, energy and dust and for the coupling of the different atmospheric regions on Mars. Almost all kinds of waves have been observed in the lower atmosphere (e.g. stationary and transient waves, baroclinic waves as well as migrating and non-migrating thermal tides, gravity waves, etc...). Atmospheric waves are also known to exist in the middle atmosphere of Mars ( 70-120 km, e.g. by the SPICAM instrument on Mars Express). In the thermosphere, thermal tides have been observed e.g. by radio occultation or accelerometer measurements on MGS. Recently, the NGIMS instrument on MAVEN reported gravity waves in the thermosphere of Mars. Radio Science profiles from the Mars Express Radio Science experiment MaRS on Mars Express can analyse the temperature, pressure and neutral number density profiles in the lower atmosphere (from a few hundred metres above the surface up to 40-50 km) and electron density profiles in the ionosphere of Mars. Wavelike structures have been detected below the main ionospheric layers (M1 & M2) and in the topside of the ionosphere. The two coherent frequencies of the MaRS experiment allow to discriminate between plasma density fluctuations in the ionosphere and Doppler related frequency shifts caused by spacecraft movement. A careful analysis of the observed electron density fluctuations in combination with sensitivity studies of the radio occultation technique will be used to classify the observed fluctuations. The MaRS experiment is funded by DLR under grant 50QM1401.

Waves in the middle and upper atmosphere of Mars as seen by the Radio Science Experiment MaRS on Mars Express

NASA Astrophysics Data System (ADS)

Tellmann, Silvia Anna; Paetzold, Martin; Häusler, Bernd; Hinson, David P.; Peter, Kerstin; Tyler, G. Leonard

2017-10-01

Atmospheric waves play a crucial role for the dynamics in the Martian atmosphere. They are responsible for the redistribution of momentum, energy and dust and the coupling of the different atmospheric regions on Mars.Almost all kinds of waves have been observed in the lower atmosphere (e.g. stationary and transient waves, baroclinic waves as well as migrating and non-migrating thermal tides, and gravity waves). Atmospheric waves are also known to exist in the middle atmosphere of Mars (~70-120 km, e.g. by the SPICAM instrument on Mars Express). In the thermosphere, thermal tides have been observed e.g. by radio occultation or accelerometer measurements on MGS. Recently, the NGIMS instrument on MAVEN reported gravity waves in the thermosphere of Mars.Radio Science profiles from the Mars Express Radio Science experiment MaRS on Mars Express can analyse the temperature, pressure and neutral number density profiles in the lower atmosphere (from a few hundred metres above the surface up to ~ 40-50 km) and electron density profiles in the ionosphere of Mars.Wavelike structures have been detected below the main ionospheric layers (M1 & M2) and in the topside of the ionosphere. The two coherent frequencies of the MaRS experiment allow to discriminate between plasma density fluctuations in the ionosphere and Doppler related frequency shifts caused by spacecraft movement.A careful analysis of the observed electron density fluctuations in combination with sensitivity studies of the radio occultation technique will be used to classify the observed fluctuations.The MaRS experiment is funded by DLR under grant 50QM1401.

Characteristics of worst hour rainfall rate for radio wave propagation modelling in Nigeria

NASA Astrophysics Data System (ADS)

Osita, Ibe; Nymphas, E. F.

2017-10-01

Radio waves especially at the millimeter-wave band are known to be attenuated by rain. Radio engineers and designers need to be able to predict the time of the day when radio signal will be attenuated so as to provide measures to mitigate this effect. This is achieved by characterizing the rainfall intensity for a particular region of interest into worst month and worst hour of the day. This paper characterized rainfall in Nigeria into worst year, worst month, and worst hour. It is shown that for the period of study, 2008 and 2009 are the worst years, while September is the most frequent worst month in most of the stations. The evening time (LT) is the worst hours of the day in virtually all the stations.

Jupiter radio bursts and particle acceleration

NASA Technical Reports Server (NTRS)

Desch, Michael D.

1994-01-01

Particle acceleration processes are important in understanding many of the Jovian radio and plasma wave emissions. However, except for the high-energy electrons that generate synchrotron emission following inward diffusion from the outer magnetosphere, acceleration processes in Jupiter's magnetosphere and between Jupiter and Io are poorly understood. We discuss very recent observations from the Ulysses spacecraft of two new Jovian radio and plamas wave emissions in which particle acceleration processes are important and have been addressed directly by complementary investigations. First, radio bursts known as quasi-periodic bursts have been observed in close association with a population of highly energetic electrons. Second, a population of much lower energy (keV range) electrons on auroral field lines can be shown to be responsible for the first observation of a Jovian plasma wave emission known as auroral hiss.

Design and Implementation of an Electronic Front-End Based on Square Wave Excitation for Ultrasonic Torsional Guided Wave Viscosity Sensor

PubMed Central

Rabani, Amir

2016-01-01

The market for process instruments generally requires low cost devices that are robust, small in size, portable, and usable in-plant. Ultrasonic torsional guided wave sensors have received much attention by researchers for measurement of viscosity and/or density of fluids in recent years. The supporting electronic systems for these sensors providing many different settings of sine-wave signals are bulky and expensive. In contrast, a system based on bursts of square waves instead of sine waves would have a considerable advantage in that respect and could be built using simple integrated circuits at a cost that is orders of magnitude lower than for a windowed sine wave device. This paper explores the possibility of using square wave bursts as the driving signal source for the ultrasonic torsional guided wave viscosity sensor. A simple design of a compact and fully automatic analogue square wave front-end for the sensor is also proposed. The successful operation of the system is demonstrated by using the sensor for measuring the viscosity in a representative fluid. This work provides the basis for design and manufacture of low cost compact standalone ultrasonic guided wave sensors and enlightens the possibility of using coded excitation techniques utilising square wave sequences in such applications. PMID:27754324

Design and Implementation of an Electronic Front-End Based on Square Wave Excitation for Ultrasonic Torsional Guided Wave Viscosity Sensor.

PubMed

Rabani, Amir

2016-10-12

The market for process instruments generally requires low cost devices that are robust, small in size, portable, and usable in-plant. Ultrasonic torsional guided wave sensors have received much attention by researchers for measurement of viscosity and/or density of fluids in recent years. The supporting electronic systems for these sensors providing many different settings of sine-wave signals are bulky and expensive. In contrast, a system based on bursts of square waves instead of sine waves would have a considerable advantage in that respect and could be built using simple integrated circuits at a cost that is orders of magnitude lower than for a windowed sine wave device. This paper explores the possibility of using square wave bursts as the driving signal source for the ultrasonic torsional guided wave viscosity sensor. A simple design of a compact and fully automatic analogue square wave front-end for the sensor is also proposed. The successful operation of the system is demonstrated by using the sensor for measuring the viscosity in a representative fluid. This work provides the basis for design and manufacture of low cost compact standalone ultrasonic guided wave sensors and enlightens the possibility of using coded excitation techniques utilising square wave sequences in such applications.

Radio Spectral Imaging of Reflective MHD Waves during the Impulsive Phase of a Solar Flare

NASA Astrophysics Data System (ADS)

Yu, S.; Chen, B.; Reeves, K.

2017-12-01

We report a new type of coherent radio bursts observed by the Karl G. Jansky Very Large Array (VLA) in 1-2 GHz during the impulsive phase of a two-ribbon flare on 2014 November 1, which we interpret as MHD waves reflected near the footpoint of flaring loops. In the dynamic spectrum, this burst starts with a positive frequency drift toward higher frequencies until it slows down near its highest-frequency boundary. Then it turns over and drifts toward lower frequencies. The frequency drift rate in its descending and ascending branch is between 50-150 MHz/s, which is much slower than type III radio bursts associated with fast electron beams but close to the well-known intermediate drift bursts, or fiber bursts, which are usually attributed to propagating whistler or Alfvenic waves. Thanks to VLA's unique capability of imaging with spectrometer-like temporal and spectral resolution (50 ms and 2 MHz), we are able to obtain an image of the radio source at every time and frequency in the dynamic spectrum where the burst is present and trace its spatial evolution. From the imaging results, we find that the radio source firstly moves downward toward one of the flaring ribbons before it "bounces off" at the lowest height (corresponding to the turnover frequency in the dynamic spectrum) and moves upward again. The measured speed in projection is at the order of 1-2 Mm/s, which is characteristic of Alfvenic or fast-mode MHD waves in the low corona. We conclude that the radio burst is emitted by trapped nonthermal electrons in the flaring loop carried along by a large-scale MHD wave. The waves are probably launched during the eruption of a magnetic flux rope in the flare impulsive phase.

Radio Receiver Instrument (RRI) ePOP transionospheric observations from an HF transmitter in Ottawa (45N, 75W)

NASA Astrophysics Data System (ADS)

Hussey, G. C.; Danskin, D. W.; Gillies, R. G.; James, H. G.; Yau, A. W.; Hird, F. C.; Fairbairn, D. T.

2016-12-01

A ground-based HF transmitter operating at 10.422 MHz in Ottawa, Canada (45.4N, 75.6W) was the radio source for reception by the satellite-based Radio Receiver Instrument (RRI) for 5 passes in late April, 2016. The RRI is one of eight instruments on the enhanced Polar Outflow Probe (ePOP) scientific payload portion of the CSA (Canadian Space Agency) CASSIOPE (Cascade Demonstrator Small-Sat and Ionospheric Polar Explorer) satellite mission launched in September, 2013. The crossed-dipole configuration of the RRI allows for complete polarization observations. Initial analysis of the passes indicates reception of a highly polarized signal. South of the transmitter the signal clearly exhibits Faraday rotation of an essentially linearly polarized radio wave in agreement with modeling by Gillies et al. [2007]. This propagation is characterized as quasi-longitudinal (QL) by the Appleton-Hartree equation (electromagnetic wave propagation in a cold magnetized plasma) as the radio waves travel in a direction more along the magnetic field of the Earth. When the satellite moves north of the Ottawa transmitter the radio wave propagation transitions into quasi-transverse (QT). The data indicates favoring circular polarization dependent on the geometry with respect to the transmitter. Surprisingly the Faraday rotation effect is still very pronounced reversing in direction roughly 1000 km north of the transmitter. The model of Gillies et al. [2007] has been extended to explain these observations. This is the first direct observation, by polarimetry, of HF radio wave propagation in near-Earth space plasmas.Gillies, R.G., G.C. Hussey, H.G. James, G.J. Sofko, and D. Andre, Modelling and observation of transionospheric propagation results from ISIS II in preparation for ePOP, Ann. Geophys. 25, 87-97, 2007.

In Situ Detection of Strong Langmuir Turbulence Processes in Solar Type III Radio Bursts

NASA Technical Reports Server (NTRS)

Golla, Thejappa; Macdowall, Robert J.; Bergamo, M.

2012-01-01

The high time resolution observations obtained by the WAVES experiment of the STEREO spacecraft in solar type III radio bursts show that Langmuir waves often occur as intense localized wave packets. These wave packets are characterized by short durations of only a few ms and peak intensities, which well exceed the supersonic modulational instability (MI) thresholds. These timescales and peak intensities satisfy the criterion of the solitons collapsed to spatial scales of a few hundred Debye lengths. The spectra of these wave packets consist of primary spectral peaks corresponding to beam-resonant Langmuir waves, two or more sidebands corresponding to down-shifted and up-shifted daughter Langmuir waves, and low frequency enhancements below a few hundred Hz corresponding to daughter ion sound waves. The frequencies and wave numbers of these spectral components satisfy the resonance conditions of the modulational instability (MI). Moreover, the tricoherences, computed using trispectral analysis techniques show that these spectral components are coupled to each other with a high degree of coherency as expected of the MI type of four wave interactions. The high intensities, short scale lengths, sideband spectral structures and low frequency spectral enhancements and, high levels of tricoherences amongst the spectral components of these wave packets provide unambiguous evidence for the supersonic MI and related strong turbulence processes in type III radio bursts. The implication of these observations include: (1) the MI and related strong turbulence processes often occur in type III source regions, (2) the strong turbulence processes probably play very important roles in beam stabilization as well as conversion of Langmuir waves into escaping radiation at the fundamental and second harmonic of the electron plasma frequency, fpe, and (3) the Langmuir collapse probably follows the route of MI in type III radio bursts.

Ionospheric Caustics in Solar Radio Observations

NASA Astrophysics Data System (ADS)

Koval, A.; Chen, Y.; Stanislavsky, A.

2016-12-01

The Earth ionosphere possesses by natural focusing and defocusing effects on radio waves due to presence of variable ionospheric irregularities which could act like convergent and divergent lenses on incident radiation. In particular, the focusing of emission from the Sun was firstly detected on the Nançay Decameter Array dynamic spectra in the 1980s. On time-frequency spectrograms the intensity variations form specific structures different from well-known solar radio bursts and clearly distinguishing on a background of solar radiation. Such structures have been identified as ionospheric caustics (ICs) and considered to be the result of radio waves refraction on medium scale travelling ionospheric disturbances (MSTIDs). Although nowadays the ICs are registered by different radio observatories due to augmentation of low-frequency radio telescopes, the most recent papers devoted to ICs in solar radio records date back to the 1980s. In this study, we revisit the ICs issue with some new results by conducting a statistical analysis of occurrence rate of ICs in solar dynamic spectra in meter-decameter wavelength range for long continuous period (15 years). The seasonal variations in ICs appearance have been found for the first time. Besides, we report the possible solar cycle dependence of ICs emergence. The radio waves propagation in the ionosphere comprising MSTIDs will be considered. The present research renews the subject of ICs in the low-frequency solar radio astronomy after about 35-year letup.

A dual-polarized and reconfigurable reflectarray for generation of vortex radio waves

NASA Astrophysics Data System (ADS)

Li, Chen-Chen; Wu, Lin-Sheng; Yin, Wen-Yan

2018-05-01

Electromagnetic (EM) waves with orbital angular momentum (OAM) provide a new degree of freedom for channel multiplexing to improve the capacity of wireless communication. For OAM-based systems, it is important to design specific configurations to generate vortex radios. In this paper, a reconfigurable reflectarray antenna is proposed with independent control of dual polarizations. A reflective cell is proposed by properly assigning the variable capacitances of four varactors, which are placed between metal square rings of each unit. The varactors of each unit are divided into two groups and the capacitance value of each group controls the reflection phase for a single linear polarization. By using the equivalent circuit model, the reflective units and array can be designed efficiently. Smooth phase variation and good reflection efficiency are achieved. Then, the reflectarray is set into sectors and a simple phase-shifting surface model is used to generate vortex beam. Each sector is realized with reflective units satisfying desired reflection phases for different modes. This kind of OAM-generating method can reduce the required variation range of reflection phase and provide more choices for a specific OAM mode combination with dual polarization, which is helpful to reduce mutual coupling between the two linear polarizations. Finally, full-wave simulations show that the 0, ±1, ±2 modes of vortex beam are successfully generated at 3.5 GHz with arbitrary combination in dual-polarization, which is also supported by OAM modes purity and reflection efficiency analysis. Therefore, in our design, the reconfigurable OAM and spin angular momentum (SAM), related with polarization, can be utilized simultaneously and independently for high-capacity wireless communication.

Radio and Plasma Wave Observations at Saturn from Cassini's Approach and First Orbit

NASA Technical Reports Server (NTRS)

Gurnett, D. A.; Kurth, W. S.; Haspodarsky, G. B.; Persoon, A. M.; Averkamp, T. F.; Cecconi, B.; Lecacheux, A.; Zarka, P.; Canu, P.; Cornilleau-Wehrlin, N.

2005-01-01

We report data from the Cassini radio and plasma wave instrument during the approach and first orbit at Saturn. During the approach, radio emissions from Saturn showed that the radio rotation period is now 10 hours 45 minutes 45 k 36 seconds, about 6 minutes longer than measured by Voyager in 1980 to 1981. In addition, many intense impulsive radio signals were detected from Saturn lightning during the approach and first orbit. Some of these have been linked to storm systems observed by the Cassini imaging instrument. Within the magnetosphere, whistler-mode auroral hiss emissions were observed near the rings, suggesting that a strong electrodynamic interaction is occurring in or near the rings.

Evaluation of quasi-square wave inverter as a power source for induction motors

NASA Technical Reports Server (NTRS)

Guynes, B. V.; Haggard, R. L.; Lanier, J. R., Jr.

1977-01-01

The relative merits of quasi-square wave inverter-motor technology versus a sine wave inverter-motor system were investigated. The empirical results of several tests on various sizes of wye-wound induction motors are presented with mathematical analysis to support the conclusions of the study. It was concluded that, within the limitations presented, the quasi-square wave inverter-motor system is superior to the more complex sine wave system for most induction motor applications in space.

Fluctuations of radio occultation signals in sounding the Earth's atmosphere

NASA Astrophysics Data System (ADS)

Kan, Valery; Gorbunov, Michael E.; Sofieva, Viktoria F.

2018-02-01

We discuss the relationships that link the observed fluctuation spectra of the amplitude and phase of signals used for the radio occultation sounding of the Earth's atmosphere, with the spectra of atmospheric inhomogeneities. Our analysis employs the approximation of the phase screen and of weak fluctuations. We make our estimates for the following characteristic inhomogeneity types: (1) the isotropic Kolmogorov turbulence and (2) the anisotropic saturated internal gravity waves. We obtain the expressions for the variances of the amplitude and phase fluctuations of radio occultation signals as well as their estimates for the typical parameters of inhomogeneity models. From the GPS/MET observations, we evaluate the spectra of the amplitude and phase fluctuations in the altitude interval from 4 to 25 km in the middle and polar latitudes. As indicated by theoretical and experimental estimates, the main contribution into the radio signal fluctuations comes from the internal gravity waves. The influence of the Kolmogorov turbulence is negligible. We derive simple relationships that link the parameters of internal gravity waves and the statistical characteristics of the radio signal fluctuations. These results may serve as the basis for the global monitoring of the wave activity in the stratosphere and upper troposphere.

Satellite radio occultation investigations of internal gravity waves in the planetary atmospheres

NASA Astrophysics Data System (ADS)

Kirillovich, Ivan; Gubenko, Vladimir; Pavelyev, Alexander

Internal gravity waves (IGWs) modulate the structure and circulation of the Earth’s atmosphere, producing quasi-periodic variations in the wind velocity, temperature and density. Similar effects are anticipated for the Venus and Mars since IGWs are a characteristic of stably stratified atmosphere. In this context, an original method for the determination of IGW parameters from a vertical temperature profile measurement in a planetary atmosphere has been developed [Gubenko et al., 2008, 2011, 2012]. This method does not require any additional information not contained in the profile and may be used for the analysis of profiles measured by various techniques. The criterion for the IGW identification has been formulated and argued. In the case when this criterion is satisfied, the analyzed temperature fluctuations can be considered as wave-induced. The method is based on the analysis of relative amplitudes of the wave field and on the linear IGW saturation theory in which these amplitudes are restricted by dynamical (shear) instability processes in the atmosphere. When the amplitude of an internal wave reaches the shear instability threshold, energy is assumed to be dissipated in such a way that the IGW amplitude is maintained at the instability threshold level as the wave propagates upwards. We have extended the developed technique [Gubenko et al., 2008] in order to reconstruct the complete set of wave characteristics including such important parameters as the wave kinetic and potential energy per unit mass and IGW fluxes of the energy and horizontal momentum [Gubenko et al., 2011]. We propose also an alternative method to estimate the relative amplitudes and to extract IGW parameters from an analysis of perturbations of the Brunt-Vaislala frequency squared [Gubenko et al., 2011]. An application of the developed method to the radio occultation (RO) temperature data has given the possibility to identify the IGWs in the Earth's, Martian and Venusian atmospheres and to determine the magnitudes of key wave parameters such as the intrinsic frequency, amplitudes of vertical and horizontal wind velocity perturbations, vertical and horizontal wavelengths, intrinsic vertical and horizontal phase (and group) speeds, kinetic and potential energy per unit mass, vertical fluxes of the wave energy and horizontal momentum. Vertical profiles of temperature retrieved from RO measurements of the CHAMP (Earth), Mars Global Surveyor (Mars), Magellan and Venus Express (Venus) missions are used and analyzed to identify discrete or “narrow spectral” wave events and to determine IGW characteristics in the Earth’s, Martian and Venusian atmospheres. This work was partially supported by the RFBR grant 13-02-00526-a and Program 22 of the RAS Presidium. References. Gubenko V.N., Pavelyev A.G., Andreev V.E. Determination of the intrinsic frequency and other wave parameters from a single vertical temperature or density profile measurement // J. Geophys. Res. 2008. V. 113. No.D08109, doi:10.1029/2007JD008920. Gubenko V.N., Pavelyev A.G., Salimzyanov R.R., Pavelyev A.A. Reconstruction of internal gravity wave parameters from radio occultation retrievals of vertical temperature profiles in the Earth’s atmosphere // Atmos. Meas. Tech. 2011. V. 4. No.10. P. 2153-2162, doi:10.5194/amt-4-2153-2011. Gubenko V.N., Pavelyev A.G., Salimzyanov R.R., Andreev V.E. A method for determination of internal gravity wave parameters from a vertical temperature or density profile measurement in the Earth’s atmosphere // Cosmic Res. 2012. V. 50. No.1. P. 21-31, doi: 10.1134/S0010952512010029.

Relations among low ionosphere parameters and high frequency radio wave absorption

NASA Technical Reports Server (NTRS)

Cipriano, J. P.

1973-01-01

Charged particle conductivities measured in the very low ionosphere at White Sands Missile Range, New Mexico, and Wallops Island, Virginia, are compared with atmospheric parameters and high frequency radio wave absorption measurements. Charged particle densities are derived from the conductivity data. Between 33 and 58 km, positive conductivity correlated well with neutral atmospheric temperature, with temperature coefficients as large as 4.6%/deg K. Good correlations were also found between HF radio wave absorption and negative conductivity at altitudes as low as 53 km, indicating that the day-to-day absorption variations were principally due to variations in electron loss rate.

Investigation of the small-scale structure and dynamics of Uranus' atmosphere

NASA Technical Reports Server (NTRS)

Eshleman, Von R.; Hinson, David P.

1991-01-01

This document constitutes the final technical report of the Uranus Analysis Program. Papers and/or abstracts resulting from this research are presented. The following topics are covered: (1) past and future of radio occultation studies of planetary atmospheres; (2) equatorial waves in the stratosphere of Uranus; (3) the atmosphere of Uranus- results of radio occultation measurements with Voyager 2; (4) Uranus' atmospheric dynamics and circulation; (5) small-scale structure and dynamics in the atmosphere of Uranus; (6) evidence for inertia-gravity waves in the stratosphere of Uranus derived from Voyager 2 radio occultation data; and (7) planetary waves in the equatorial stratosphere of Uranus.

Generation and evolution of mode-locked noise-like square-wave pulses in a large-anomalous-dispersion Er-doped ring fiber laser.

PubMed

Liu, Jun; Chen, Yu; Tang, Pinghua; Xu, Changwen; Zhao, Chujun; Zhang, Han; Wen, Shuangchun

2015-03-09

In a passively mode-locked Erbium-doped fiber laser with large anomalous-dispersion, we experimentally demonstrate the formation of noise-like square-wave pulse, which shows quite different features from conventional dissipative soliton resonance (DSR). The corresponding temporal and spectral characteristics of a variety of operation states, including Q-switched mode-locking, continuous-wave mode-locking and Raman-induced noise-like pulse near the lasing threshold, are also investigated. Stable noise-like square-wave mode-locked pulses can be obtained at a fundamental repetition frequency of 195 kHz, with pulse packet duration tunable from 15 ns to 306 ns and per-pulse energy up to 200 nJ. By reducing the linear cavity loss, stable higher-order harmonic mode-locking had also been observed, with pulse duration ranging from 37 ns at the 21st order harmonic wave to 320 ns at the fundamental order. After propagating along a piece of long telecom fiber, the generated square-wave pulses do not show any obvious change, indicating that the generated noise-like square-wave pulse can be considered as high-energy pulse packet for some promising applications. These experimental results should shed some light on the further understanding of the mechanism and characteristics of noise-like square-wave pulses.

Phase Coupling Between Spectral Components of Collapsing Langmuir Solitons in Solar Type III Radio Bursts

NASA Technical Reports Server (NTRS)

Thejappa, G.; MacDowall, R. J.; Bergamo, M.

2012-01-01

We present the high time resolution observations of one of the Langmuir wave packets obtained in the source region of a solar type III radio burst. This wave packet satisfies the threshold condition of the supersonic modulational instability, as well as the criterion of a collapsing Langmuir soliton, i.e., the spatial scale derived from its peak intensity is less than that derived from its short time scale. The spectrum of t his wave packet contains an intense spectral peak at local electron plasma frequency, f(sub pe) and relatively weaker peaks at 2f(sub pe) and 3f(sub pe). We apply the wavelet based bispectral analysis technique on this wave packet and compute the bicoherence between its spectral components. It is found that the bicoherence exhibits two peaks at (approximately f(sub pe), approximately f(sub pe)) and (approximately f(sub pe) approximately 2f(sub pe)), which strongly suggest that the spectral peak at 2f(sub pe) probably corresponds to the second harmonic radio emission, generated as a result of the merging of antiparallel propagating Langmuir waves trapped in the collapsing Langmuir soliton, and, the spectral peak at 3f(sub pe) probably corresponds to the third harmonic radio emission, generated as a result of merging of a trapped Langmuir wave and a second harmonic electromagnetic wave.

Salt Neutrino Detector for Ultrahigh-Energy Neutrinos

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chiba, M.; Yasuda, O.; Kamijo, T.

2004-11-01

Rock salt and limestone are studied to determine their suitability for use as a radio-wave transmission medium in an ultrahigh energy (UHE) cosmic neutrino detector. A sensible radio wave would be emitted by the coherent Cherenkov radiation from negative excess charges inside an electromagnetic shower upon interaction of a UHE neutrino in a high-density medium (Askar'yan effect). If the attenuation length for the radio wave in the material is large, a relatively small number of radio-wave sensors could detect the interaction occurring in the massive material. We measured the complex permittivity of the rock salt and limestone by the perturbedmore » cavity resonator method at 9.4 and 1 GHz to good precision. We obtained new results of measurements at the frequency at 1.0 GHz. The measured value of the radio-wave attenuation length of synthetic rock salt samples is 1080 m. The samples from the Hockley salt mine in the United States show attenuation length of 180 m at 1 GHz, and then we estimate it by extrapolation to be as long as 900 m at 200 MHz. The results show that there is a possibility of utilizing natural massive deposits of rock salt for a UHE neutrino detector. A salt neutrino detector with a size of 2 x 2 x 2 km would detect 10 UHE neutrino/yr generated through the GZK process.« less

The Atacama Cosmology Telescope: Extragalactic Sources at 148 GHz in the 2008 Survey

NASA Technical Reports Server (NTRS)

Marriage, T. A.; Juin, J. B.; Lin, Y. T.; Marsden, D.; Nolta, M. R.; Partridge, B.; Ade, P. A. R.; Aguirre, P.; Amiri, M.; Appel, J. W.;

Spacecraft Radio Scintillation and Solar System Exploration

NASA Technical Reports Server (NTRS)

Woo, Richard

1993-01-01

When a wave propagates through a turbulent medium, scattering by the random refractive index inhomogeneities can lead to a wide variety of phenomena that have been the subject of extensive study. The observed scattering effects include amplitude or intensity scintillation, phase scintillation, angular broadening, and spectral broadening, among others. In this paper, I will refer to these scattering effects collectively as scintillation. Although the most familiar example is probably the twinkling of stars (light wave intensity scintillation by turbulence in the Earth's atmosphere), scintillation has been encountered and investigated in such diverse fields as ionospheric physics, oceanography, radio astronomy, and radio and optical communications. Ever since planetary spacecraft began exploring the solar system, scintillation has appeared during the propagation of spacecraft radio signals through planetary atmospheres, planetary ionospheres, and the solar wind. Early studies of these phenomena were motivated by the potential adverse effects on communications and navigation, and on experiments that use the radio link to conduct scientific investigations. Examples of the latter are radio occultation measurements (described below) of planetary atmospheres to deduce temperature profiles, and the search for gravitational waves. However,these concerns soon gave way to the emergence of spacecraft radio scintillation as a new scientific tool for exploring small-scale dynamics in planetary atmospheres and structure in the solar wind, complementing in situ and other remote sensing spacecraft measurements, as well as scintillation measurements using natural (celestial) radio sources. The purpose of this paper is to briefly describe and review the solar system spacecraft radio scintillation observations, to summarize the salient features of wave propagation analyses employed in interpreting them, to underscore the unique remote sensing capabilities and scientific relevance of the scintillation measurements, and to highlight some of the scientific results obtained to date. Special emphasis is placed on comparing the remote sensing features of planetary and terrestrial scintillation measurements, and on contrasting spacecraft and natural radio source scintillation measurements. I will first discuss planetary atmospheres and ionospheres, and then the solar wind.

International Conference on Antennas and Propagation (ICAP 89), 6th, University of Warwick, Coventry, England, Apr. 4-7, 1989, Proceedings. Part 1 - Antennas. Part 2 - Propagation

NASA Astrophysics Data System (ADS)

Various papers on antennas and propagation are presented. The general topics addressed include: phased arrays; reflector antennas; slant path propagation; propagation data for HF radio systems performance; satellite and earth station antennas; radio propagation in the troposphere; propagation data for HF radio systems performance; microstrip antennas; rain radio meteorology; conformal antennas; horns and feed antennas; low elevation slant path propagation; radio millimeter wave propagation; array antennas; propagation effects on satellite mobile, satellite broadcast, and aeronautical systems; ionospheric irregularities and motions; adaptive antennas; transient response; measurement techniques; clear air radio meteorology; ionospheric and propagation modeling; millimeter wave and lens antennas; electromagnetic theory and numerical techniques; VHF propagation modeling, system planning methods; radio propagation theoretical techniques; scattering and diffraction; transhorizon rain scatter effects; ELF-VHF and broadcast antennas; clear air millimeter propagation; scattering and frequency-selective surfaces; antenna technology; clear air transhorizon propagation.

978-nm square-wave in an all-fiber single-mode ytterbium-doped fiber laser

NASA Astrophysics Data System (ADS)

Li, Shujie; Xu, Lixin; Gu, Chun

2018-01-01

A 978 nm single mode passively mode-locked all-fiber laser delivering square-wave pulses was demonstrated using a figure-8 cavity and a 75 cm commercial double-clad ytterbium-doped fiber. We found the three-level system near 978 nm was able to operate efficiently under clad pumping, simultaneously oscillation around 1030 nm well inhibited. The optimized nonlinear amplifying loop mirror made the mode locking stable and performed the square-pulses shaping. To the best of our knowledge, it is the first time to report the square-wave pulse fiber laser operating at 980 nm. The spectral width of the 978 mode-locked square pulses was about 4 nm, far greater than that of the mode-locked square pulses around 1060 nm reported before, which would be helpful to deeply understand the various square-wave pulses' natures and forming mechanisms. Compared with modulated single-mode or multimode 980 nm LDs, this kind of 980 nm square-wave sources having higher brightness, more steeper rising and falling edge and shorter pulse width, might have potential applications in pumping nanosecond ytterbium or erbium fiber lasers and amplifiers.

Optimization of one-way wave equations.

USGS Publications Warehouse

Lee, M.W.; Suh, S.Y.

1985-01-01

The theory of wave extrapolation is based on the square-root equation or one-way equation. The full wave equation represents waves which propagate in both directions. On the contrary, the square-root equation represents waves propagating in one direction only. A new optimization method presented here improves the dispersion relation of the one-way wave equation. -from Authors

Modeling of the Dynamics of Radio Wave Reflection and Absorption in a Smoothly Ionomogeneous Plasma with Electromagnetically Driven Strong Langmuir Turbulence

NASA Astrophysics Data System (ADS)

Kochetov, A. V.

2018-05-01

This work was initiated by experiments on studying the self-action of radio waves incident on the ionosphere from a ground-based transmitter at the stage of electromagnetic excitation of Langmuir turbulence (Langmuir effect). The emphasis is on the impact of "self-consistent" collisionless absorption of radio waves by the Langmuir turbulence, which develops when the incident-wave field swells in the resonant region of a smoothly inhomogeneous plasma, on the dynamics of the radio wave reflection. Electrodynamic characteristics of the nonlinear-plasma layer, which has a linear unperturbed profile of the plasma density, with different features of the absorption development are obtained for a high intensity of the incident radiation. Calculations of "soft" and "hard" regimes of the absorption occurrence, as well as hysteresis modes in which the damping switch-on and off thresholds differ several times, are carried out. The algorithms we devised and the results of the study can serve as the basis for a more adequate and more detailed numerical simulation for interpretation of the experimental data obtained at the stage of the Langmuir effect in the ionosphere.

Theory of Type 3 and Type 2 Solar Radio Emissions

NASA Technical Reports Server (NTRS)

Robinson, P. A.; Cairns, I. H.

2000-01-01

The main features of some current theories of type III and type II bursts are outlined. Among the most common solar radio bursts, type III bursts are produced at frequencies of 10 kHz to a few GHz when electron beams are ejected from solar active regions, entering the corona and solar wind at typical speeds of 0.1c. These beams provide energy to generate Langmuir waves via a streaming instability. In the current stochastic-growth theory, Langmuir waves grow in clumps associated with random low-frequency density fluctuations, leading to the observed spiky waves. Nonlinear wave-wave interactions then lead to secondary emission of observable radio waves near the fundamental and harmonic of the plasma frequency. Subsequent scattering processes modify the dynamic radio spectra, while back-reaction of Langmuir waves on the beam causes it to fluctuate about a state of marginal stability. Theories based on these ideas can account for the observed properties of type III bursts, including the in situ waves and the dynamic spectra of the radiation. Type 11 bursts are associated with shock waves propagating through the corona and interplanetary space and radiating from roughly 30 kHz to 1 GHz. Their basic emission mechanisms are believed to be similar to those of type III events and radiation from Earth's foreshock. However, several sub-classes of type II bursts may exist with different source regions and detailed characteristics. Theoretical models for type II bursts are briefly reviewed, focusing on a model with emission from a foreshock region upstream of the shock for which observational evidence has just been reported.

Potentials of the acousto-optical spectral data processing on a basis of a novel algorithm of the collinear wave heterodyning in a large-aperture KRS-5 crystalline cell

NASA Astrophysics Data System (ADS)

Shcherbakov, Alexandre S.; Maximov, Jewgemij; Sanchez Lucero, Daniel

2010-02-01

Recently proposed modern technique of a precise spectrum analysis within an algorithm of the collinear wave heterodyning implies a two-stage integrated processing, namely, the wave heterodyning of a signal in a square-law nonlinear medium and then the optical processing in the same cell. Technical advantage of this approach is in providing a direct processing of ultra-high-frequency radio-wave signals with essentially improved frequency resolution. This algorithm can be realized on a basis of various physical principles, and we consider an opportunity of involving the potentials of modern acousto-optics for these purposes. From this viewpoint, one needs a large-aperture effective acousto-optical cell, which operates in the Bragg regime and performs the ultra-high-frequency co-directional collinear acoustic wave heterodyning. The technique under consideration imposes specific requirements on the cell's material, namely, a high optical quality of large-size crystalline boules, high-efficient acousto-optical and acoustic interactions, and low group velocity of acoustic waves together with square-low dispersive acoustic losses. We focus our attention on the solid solutions of thallium chalcogenides and take the TlBr-TlI (thallium bromine - thallium iodine) solution, which forms KRS-5 cubic-symmetry crystals with the mass-ratio 58% of TlBr to 42% of TlI. Analysis shows that the acousto-optical cell made of a KRS-5 crystal oriented along the [111] -axis and the corresponding longitudinal elastic mode for producing the dynamic diffractive grating in that crystal can be exploited. With the acoustic velocity of about 1.92 mm/μs and attenuation of approximately 10 dB/(cm GHz2), similar cell is capable to provide an optical aperture of 50 mm and one of the highest figures of acousto-optical merit in solid states in the visible range. Such a cell is rather desirable for applications to direct parallel multi-channel optical spectrum analysis with substantially improved frequency resolution.

Numerical simulations of particle acceleration and low frequency radio emission in stellar environments

NASA Astrophysics Data System (ADS)

Paraskevi Moschou, Sofia; Sokolov, Igor; Cohen, Ofer; Drake, Jeremy J.; Borovikov, Dmitry; Alvarado-Gomez, Julian D.; Garraffo, Cecilia

2018-06-01

Due to their favorable atmospheric window radio waves are a useful tool for ground-based observations of astrophysical systems throughout a plethora of scales, from cosmological down to planetary ones. A wide range of physical mechanisms, from thermal processes to eruptive events linked to magnetic reconnection, can generate emission in radio frequencies. Radio waves have the distinct characteristic that they follow curved paths as they propagate in stratified environments, such as the solar corona, due to their dependence on the refraction index. Low frequency radio rays in particular are affected the most by refraction.Solar radio observations are of particular importance, since it is possible to spatially resolve the Sun and its corona and gain insights on highly dynamic and complex radio-emitting phenomena. The multi-scale problem of particle acceleration and energy partition between CMEs, flares and SEPs requires both MHD and kinetic considerations to account for the emission and mass propagation through the interplanetary space.Radio observations can play a significant role in the rapidly developing area of exoplanetary research and provide insights on the stellar environments of those systems. Even though a large number of flares has been observed for different stellar types, nevertheless there is a lack of stellar CME observations. Currently, the most promising method to incontrovertibly observe stellar CMEs is through Type II radio bursts. Low frequency radio emission can also be produced by the interaction of a magnetized planet with the stellar wind of the host star.The above mentioned characteristics of radio-waves make their integration into numerical simulations imperative for capturing and disentangling the complex radio emitting processes along the actual radio paths and provide the observers with detection limits for future Earth- and space-based missions. Radio synthetic imaging tools incorporated in realistic computational codes are already available for solar radio-emitting processes with different physical and observational characteristics.

47 CFR 2.1 - Terms and definitions.

Code of Federal Regulations, 2010 CFR

2010-10-01

... radiocommunication services or the radio astronomy service under specified conditions. This term shall also be... or the spacecraft above the Earth's surface or another surface. (RR) Radio Astronomy. Astronomy based on the reception of radio waves of cosmic origin. (RR) Radio Astronomy Service. A service involving...

47 CFR 2.1 - Terms and definitions.

Code of Federal Regulations, 2011 CFR

2011-10-01

... radiocommunication services or the radio astronomy service under specified conditions. This term shall also be... or the spacecraft above the Earth's surface or another surface. (RR) Radio Astronomy. Astronomy based on the reception of radio waves of cosmic origin. (RR) Radio Astronomy Service. A service involving...

47 CFR 2.1 - Terms and definitions.

Code of Federal Regulations, 2012 CFR

2012-10-01

... radiocommunication services or the radio astronomy service under specified conditions. This term shall also be... or the spacecraft above the Earth's surface or another surface. (RR) Radio Astronomy. Astronomy based on the reception of radio waves of cosmic origin. (RR) Radio Astronomy Service. A service involving...

Electric Field Strength Of Coherent Radio Emission In Rock Salt Concerning Ultra High-Energy Neutrino Detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watanabe, Y.; Chiba, M.; Yasuda, O.

2006-07-12

Detection possibility of ultra high-energy (UHE) neutrino (E >1015 eV) in natural huge rock salt formation has been studied. Collision between the UHE neutrino and the rock salt produces electromagnetic (EM) shower. Charge difference (excess electrons) between electrons and positrons in EM shower radiates radio wave coherently (Askar'yan effect). Angular distribution and frequency spectrum of electric field strength of radio wave radiated from 3-dimensional EM shower in rock salt are presented.

The influence of polarization on millimeter wave propagation through rain. [radio signals

NASA Technical Reports Server (NTRS)

Bostian, C. W.; Stutzman, W. L.; Wiley, P. H.; Marshall, R. E.

1973-01-01

The measurement and analysis of the depolarization and attenuation that occur when millimeter wave radio signals propagate through rain are described. Progress was made in three major areas: the processing of recorded 1972 data, acquisition and processing of a large amount of 1973 data, and the development of a new theoretical model to predict rain cross polarization and attenuation. Each of these topics is described in detail along with radio frequency system design for cross polarization measurements.

Radio Wave Propagation: A Handbook of Practical Techniques for Computing Basic Transmission Loss and Field Strength

DTIC Science & Technology

1982-09-01

MARK A. WEISSBEGU KALLE R. XONTSON Project Msnaqer, IUTRZ Assistant Director Contractor Operations Approved by CRARLES L. FLYNN, 001, us A. M. MESSE...34 BSTJ, 1946. 2-4priis, H.T., "Introduction to Radio and Antennas," IEEE Spectrum, April, 1971 . RADIO WAVE PROPAGATION: A HANDBOOK OF PRACTICAL...Propagation Tests, TR-0177-71.01, Gautney & Jones Communications, Inc., Falls Church, VA, June 1971 . 3 -7 Comparison of Predicted VLF/LF Signal

Shock Formation Height in the Solar Corona Estimated from SDO and Radio Observations

NASA Technical Reports Server (NTRS)

Gopalswamy, N.; Nitta, N.

2011-01-01

Wave transients at EUV wavelengths and type II radio bursts are good indicators of shock formation in the solar corona. We use recent EUV wave observations from SDO and combine them with metric type II radio data to estimate the height in the corona where the shocks form. We compare the results with those obtained from other methods. We also estimate the shock formation heights independently using white-light observations of coronal mass ejections that ultimately drive the shocks.

Dual-polarization and dual-mode orbital angular momentum radio vortex beam generated by using reflective metasurface

NASA Astrophysics Data System (ADS)

Yu, Shixing; Li, Long; Shi, Guangming

2016-08-01

A metasurface, which is composed of printed cross-dipole elements with different arm lengths, is designed, fabricated, and experimentally demonstrated to generate orbital angular momentum (OAM) vortex waves of dual polarizations and dual modes in the radio frequency domain simultaneously. The prototype of a practical metasurface is fabricated and measured to validate the results of theoretical analysis and design at 5.8 GHz. Numerical and experimental results verify that vortex waves with dual OAM modes and dual polarizations can be flexibly generated by using a reflective metasurface. The proposed method paves a way to generate diverse OAM vortex waves for radio frequency and microwave wireless communication applications.

Faraday rotation of Automatic Dependent Surveillance Broadcast (ADS-B) signals as a method of ionospheric characterization

NASA Astrophysics Data System (ADS)

Cushley, A. C.; Kabin, K.; Noel, J. M. A.

2017-12-01

Radio waves propagating through plasma in the Earth's ambient magnetic field experience Faraday rotation; the plane of the electric field of a linearly polarized wave changes as a function of the distance travelled through a plasma. Linearly polarized radio waves at 1090 MHz frequency are emitted by Automatic Dependent Surveillance Broadcast (ADS-B) devices which are installed on most commercial aircraft. These radio waves can be detected by satellites in low earth orbits, and the change of the polarization angle caused by propagation through the terrestrial ionosphere can be measured. In this work we discuss how these measurements can be used to characterize the ionospheric conditions. In the present study, we compute the amount of Faraday rotation from a prescribed total electron content value and two of the profile parameters of the NeQuick model.

Internal gravity waves in Titan's atmosphere observed by Voyager radio occultation

NASA Technical Reports Server (NTRS)

Hinson, D. P.; Tyler, G. L.

1983-01-01

The radio scintillations caused by scattering from small-scale irregularities in Titan's neutral atmosphere during a radio occultation of Voyager 1 by Titan are investigated. Intensity and frequency fluctuations occurred on time scales from about 0.1 to 1.0 sec at 3.6 and 13 cm wavelengths whenever the radio path passed within 90 km of the surface, indicating the presence of variations in refractivity on length scales from a few hundred meters to a few kilometers. Above 25 km, the altitude profile of intensity scintillations closely agrees with the predictions of a simple theory based on the characteristics of internal gravity waves propagating with little or no attenuation through the vertical stratification in Titan's atmosphere. These observations support a hypothesis of stratospheric gravity waves, possibly driven by a cloud-free convective region in the lowest few kilometers of the stratosphere.

Multifrequency synthesis and extraction using square wave projection patterns for quantitative tissue imaging.

PubMed

Nadeau, Kyle P; Rice, Tyler B; Durkin, Anthony J; Tromberg, Bruce J

2015-11-01

We present a method for spatial frequency domain data acquisition utilizing a multifrequency synthesis and extraction (MSE) method and binary square wave projection patterns. By illuminating a sample with square wave patterns, multiple spatial frequency components are simultaneously attenuated and can be extracted to determine optical property and depth information. Additionally, binary patterns are projected faster than sinusoids typically used in spatial frequency domain imaging (SFDI), allowing for short (millisecond or less) camera exposure times, and data acquisition speeds an order of magnitude or more greater than conventional SFDI. In cases where sensitivity to superficial layers or scattering is important, the fundamental component from higher frequency square wave patterns can be used. When probing deeper layers, the fundamental and harmonic components from lower frequency square wave patterns can be used. We compared optical property and depth penetration results extracted using square waves to those obtained using sinusoidal patterns on an in vivo human forearm and absorbing tube phantom, respectively. Absorption and reduced scattering coefficient values agree with conventional SFDI to within 1% using both high frequency (fundamental) and low frequency (fundamental and harmonic) spatial frequencies. Depth penetration reflectance values also agree to within 1% of conventional SFDI.

Multifrequency synthesis and extraction using square wave projection patterns for quantitative tissue imaging

PubMed Central

Nadeau, Kyle P.; Rice, Tyler B.; Durkin, Anthony J.; Tromberg, Bruce J.

2015-01-01

Abstract. We present a method for spatial frequency domain data acquisition utilizing a multifrequency synthesis and extraction (MSE) method and binary square wave projection patterns. By illuminating a sample with square wave patterns, multiple spatial frequency components are simultaneously attenuated and can be extracted to determine optical property and depth information. Additionally, binary patterns are projected faster than sinusoids typically used in spatial frequency domain imaging (SFDI), allowing for short (millisecond or less) camera exposure times, and data acquisition speeds an order of magnitude or more greater than conventional SFDI. In cases where sensitivity to superficial layers or scattering is important, the fundamental component from higher frequency square wave patterns can be used. When probing deeper layers, the fundamental and harmonic components from lower frequency square wave patterns can be used. We compared optical property and depth penetration results extracted using square waves to those obtained using sinusoidal patterns on an in vivo human forearm and absorbing tube phantom, respectively. Absorption and reduced scattering coefficient values agree with conventional SFDI to within 1% using both high frequency (fundamental) and low frequency (fundamental and harmonic) spatial frequencies. Depth penetration reflectance values also agree to within 1% of conventional SFDI. PMID:26524682

Features of HF Radio Wave Attenuation in the Midlatitude Ionosphere Near the Skip Zone Boundary

NASA Astrophysics Data System (ADS)

Denisenko, P. F.; Skazik, A. I.

2017-06-01

We briefly describe the history of studying the decameter radio wave attenuation by different methods in the midlatitude ionosphere. A new method of estimating the attenuation of HF radio waves in the ionospheric F region near the skip zone boundary is presented. This method is based on an analysis of the time structure of the interference field generated by highly stable monochromatic X-mode radio waves at the observation point. The main parameter is the effective electron collision frequency νeff, which allows for all energy losses in the form of equivalent heat loss. The frequency νeff is estimated by matching the assumed (model) and the experimentally observed structures. Model calculations are performed using the geometrical-optics approximation. The spatial attenuation caused by the influence of the medium-scale traveling ionospheric disturbances is taken into account. Spherical shape of the ionosphere and the Earth's magnetic field are roughly allowed for. The results of recording of the level of signals from the RWM (Moscow) station at a frequency of 9.996 MHz at point Rostov are used.

An Evaluation of a Numerical Prediction Method for Electric Field Strength of Low Frequency Radio Waves based on Wave-Hop Ionospheric Propagation

NASA Astrophysics Data System (ADS)

Kitauchi, H.; Nozaki, K.; Ito, H.; Kondo, T.; Tsuchiya, S.; Imamura, K.; Nagatsuma, T.; Ishii, M.

2014-12-01

We present our recent efforts on an evaluation of the numerical prediction method of electric field strength for ionospheric propagation of low frequency (LF) radio waves based on a wave-hop propagation theory described in Section 2.4 of Recommendation ITU-R P.684-6 (2012), "Prediction of field strength at frequencies below about 150 kHz," made by International Telecommunication Union Radiocommunication Sector (ITU-R). As part of the Japanese Antarctic Research Expedition (JARE), we conduct on-board measurements of the electric field strengths and phases of LF 40 kHz and 60 kHz of radio signals (call sign JJY) continuously along both the ways between Tokyo, Japan and Syowa Station, the Japanese Antarctic station, at 69° 00' S, 39° 35' E on East Ongul Island, Lützow-Holm Bay, East Antarctica. The measurements are made by a newly developed, highly sensitive receiving system installed on board the Japanese Antarctic research vessel (RV) Shirase. We obtained new data sets of the electric field strength up to approximately 13,000-14,000 km propagation of LF JJY 40 kHz and 60 kHz radio waves by utilizing a newly developed, highly sensitive receiving system, comprised of an orthogonally crossed double-loop antenna and digital-signal-processing lock-in amplifiers, on board RV Shirase during the 55th JARE from November 2013 to April 2014. We have made comparisons between those on-board measurements and the numerical predictions of field strength for long-range propagation of low frequency radio waves based on a wave-hop propagation theory described in Section 2.4 of Recommendation ITU-R P.684-6 (2012) to show that our results qualitatively support the recommended wave-hop theory for the great-circle paths approximately 7,000-8,000 km and 13,000-14,000 km propagations.

Generation and Upper Atmospheric Propagation of Acoustic Gravity Waves according to Numerical Modeling and Radio Tomography

NASA Astrophysics Data System (ADS)

Vorontsov, Artem; Andreeva, Elena; Nesterov, Ivan; Padokhin, Artem; Kurbatov, Grigory

2016-04-01

The acoustic-gravity waves (AGW) in the upper atmosphere and ionosphere can be generated by a variety of the phenomena in the near-Earth environment and atmosphere as well as by some perturbations of the Earth's ground or ocean surface. For instance, the role of the AGW sources can be played by the earthquakes, explosions, thermal heating, seisches, tsunami waves. We present the examples of AGWs excited by the tsunami waves traveling in the ocean, by seisches, and by ionospheric heating by the high-power radio wave. In the last case, the gravity waves are caused by the pulsed modulation of the heating wave. The AGW propagation in the upper atmosphere induces the variations and irregularities in the electron density distribution of the ionosphere, whose structure can be efficiently reconstructed by the method of the ionospheric radio tomography (RT) based on the data from the global navigational satellite systems (GNSS). The input data for RT diagnostics are composed of the 150/400 MHz radio signals from the low-orbiting (LO) satellites and 1.2-1.5 GHz radio signals from the high-orbiting (HO) satellites with their orbits at ~1000 and ~20000 km above the ground, respectively. These data enable ionospheric imaging on different spatiotemporal scales with different spatiotemporal resolution and coverage, which is suitable, inter alia, for tracking the waves and wave-like features in the ionosphere. In particular, we demonstrate the maps of the ionospheric responses to the tornado at Moore (Oklahoma, USA) of May 20, 2013, which are reconstructed from the HO data. We present the examples of LORT images containing the waves and wavelike disturbances associated with various sources (e.g., auroral precipitation and high-power heating of the ionosphere). We also discuss the results of modeling the AGW generation by the surface and volumetric sources. The millihertz AGW from these sources initiate the ionospheric perturbation with a typical scale of a few hundred km at the heights corresponding to the middle atmosphere and ionosphere. The results of numerical modeling based on the solution of the equation of geophysical hydrodynamics agree with the observations.

ATCA 16 cm observation of CIZA J1358.9-4750: Implication of merger stage and constraint on non-thermal properties

NASA Astrophysics Data System (ADS)

Akahori, Takuya; Kato, Yuichi; Nakazawa, Kazuhiro; Ozawa, Takeaki; Gu, Liyi; Takizawa, Motokazu; Fujita, Yutaka; Nakanishi, Hiroyuki; Okabe, Nobuhiro; Makishima, Kazuo

2018-06-01

We report the Australia Telescope Compact Array 16 cm observation of CIZA J1358.9-4750. Recent X-ray studies imply that this galaxy cluster is composed of merging, binary clusters. Using the EW367 configuration, we found no significant diffuse radio emission in and around the cluster. An upper limit of the total radio power at 1.4 GHz is ˜1.1 × 1022 W Hz-1 in 30 square arcminutes, which is a typical size for radio relics. It is known that an empirical relation holds between the total radio power and X-ray luminosity of the host cluster. The upper limit is about one order of magnitude lower than the power expected from the relation. Very young (˜70 Myr) shocks with low Mach numbers (˜1.3), which are often seen at an early stage of merger simulations, are suggested by the previous X-ray observation. The shocks may generate cosmic-ray electrons with a steep energy spectrum, which is consistent with non-detection of bright (>1023 W Hz-1) relic in this 16 cm band observation. Based on the assumption of energy equipartition, the upper limit gives a magnetic field strength of below 0.68f(Dlos/1 Mpc)-1(γmin/200)-1 μG, where f is the cosmic-ray total energy density over the cosmic-ray electron energy density, Dlos is the depth of the shock wave along the sightline, and γmin is the lower cutoff Lorentz factor of the cosmic-ray electron energy spectrum.

Pulsar discoveries by volunteer distributed computing and the strongest continuous gravitational wave signal

NASA Astrophysics Data System (ADS)

Knispel, Benjamin

2011-07-01

Neutron stars are the endpoints of stellar evolution and one of the most compact forms of matter in the universe. They can be observed as radio pulsars and are promising sources for the emission of continuous gravitational waves. Discovering new radio pulsars in tight binary orbits offers the opportunity to conduct very high precision tests of General Relativity and to further our understanding of neutron star structure and matter at super-nuclear densities. The direct detection of gravitational waves would validate Einstein's theory of Relativity and open a new window to the universe by offering a novel astronomical tool. This thesis addresses both of these scientific fields: the first fully coherent search for radio pulsars in tight, circular orbits has been planned, set up and conducted in the course of this thesis. Two unusual radio pulsars, one of them in a binary system, have been discovered. The other half of this thesis is concerned with the simulation of the Galactic neutron star population to predict their emission of continuous gravitational waves. First realistic statistical upper limits on the strongest continuous gravitational-wave signal and detection predictions for realistic all-sky blind searches have been obtained. The data from a large-scale pulsar survey with the 305-m Arecibo radio telescope were searched for signals from radio pulsars in binary orbits. The massive amount of computational work was done on hundreds of thousands of computers volunteered by members of the general public through the distributed computing project Einstein@Home. The newly developed analysis pipeline searched for pulsar spin frequencies below 250 Hz and for orbital periods as short as 11 min. The structure of the search pipeline consisting of data preparation, data analysis, result post-processing, and set-up of the pipeline components is presented in detail. The first radio pulsar, discovered with this search, PSR J2007+2722, is an isolated radio pulsar, likely from a double neutron star system disrupted by the second supernova. We present discovery and initial characterisation using observations from five of the largest radio telescopes worldwide. Only a dozen similar systems were previously known. The second discovered radio pulsar, PSR J1952+2630, is in a 9.4-hr orbit with most likely a massive white dwarf of at least 0.95 M⊙. We characterise its orbit by analysis of the apparent spin period changes. This pulsar most likely belongs to the very rare class of intermediate-mass binary pulsars, from which only five systems were previously known. It is a promising target for the future measurement of relativistic effects. In the second half of this thesis, the emission of continuous gravitational waves from a Galactic population of neutron stars is studied. For the first time, realistic estimates of the statistical upper limit of the expected gravitational wave signal are obtained, improving previous estimates by about a factor of six. The simulation is used to obtain for the first time detectability predictions for these objects with ground based gravitational wave detectors and realistic blind searches. It is also shown how to improve possible searches by maximising the number of detections for a fixed amount of computation cycles.

HIRAX: a probe of dark energy and radio transients

NASA Astrophysics Data System (ADS)

Newburgh, L. B.; Bandura, K.; Bucher, M. A.; Chang, T.-C.; Chiang, H. C.; Cliche, J. F.; Davé, R.; Dobbs, M.; Clarkson, C.; Ganga, K. M.; Gogo, T.; Gumba, A.; Gupta, N.; Hilton, M.; Johnstone, B.; Karastergiou, A.; Kunz, M.; Lokhorst, D.; Maartens, R.; Macpherson, S.; Mdlalose, M.; Moodley, K.; Ngwenya, L.; Parra, J. M.; Peterson, J.; Recnik, O.; Saliwanchik, B.; Santos, M. G.; Sievers, J. L.; Smirnov, O.; Stronkhorst, P.; Taylor, R.; Vanderlinde, K.; Van Vuuren, G.; Weltman, A.; Witzemann, A.

2016-08-01

The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a new 400{800MHz radio interferometer under development for deployment in South Africa. HIRAX will comprise 1024 six meter parabolic dishes on a compact grid and will map most of the southern sky over the course of four years. HIRAX has two primary science goals: to constrain Dark Energy and measure structure at high redshift, and to study radio transients and pulsars. HIRAX will observe unresolved sources of neutral hydrogen via their redshifted 21-cm emission line (`hydrogen intensity mapping'). The resulting maps of large-scale structure at redshifts 0.8{2.5 will be used to measure Baryon Acoustic Oscillations (BAO). BAO are a preferential length scale in the matter distribution that can be used to characterize the expansion history of the Universe and thus understand the properties of Dark Energy. HIRAX will improve upon current BAO measurements from galaxy surveys by observing a larger cosmological volume (larger in both survey area and redshift range) and by measuring BAO at higher redshift when the expansion of the universe transitioned to Dark Energy domination. HIRAX will complement CHIME, a hydrogen intensity mapping experiment in the Northern Hemisphere, by completing the sky coverage in the same redshift range. HIRAX's location in the Southern Hemisphere also allows a variety of cross-correlation measurements with large-scale structure surveys at many wavelengths. Daily maps of a few thousand square degrees of the Southern Hemisphere, encompassing much of the Milky Way galaxy, will also open new opportunities for discovering and monitoring radio transients. The HIRAX correlator will have the ability to rapidly and efficiently detect transient events. This new data will shed light on the poorly understood nature of fast radio bursts (FRBs), enable pulsar monitoring to enhance long-wavelength gravitational wave searches, and provide a rich data set for new radio transient phenomena searches. This paper discusses the HIRAX instrument, science goals, and current status.

Large scale atmospheric waves in the Venus mesosphere as seen by the VeRa Radio Science instrument on Venus Express

NASA Astrophysics Data System (ADS)

Tellmann, Silvia; Häusler, Bernd; Hinson, David P.; Tyler, G. Leonard; Andert, Thomas P.; Bird, Michael K.; Imamura, Takeshi; Pätzold, Martin; Remus, Stefan

2015-04-01

Atmospheric waves on all spatial scales play a crucial role in the redistribution of energy, momentum, and atmospheric constituent in planetary atmosphere and are thought to be involved in the development and maintenance of the atmospheric superrotation on Venus. The Venus Express Radio-Science Experiment VeRa sounded the Venus neutral atmosphere and ionosphere in Earth occultation geometry using the spacecraft radio subsystem at two coherent frequencies. Radial profiles of neutral number density, covering the altitude range 40-90 km, are then converted to vertical profiles of temperature and pressure, assuming hydrostatic equilibrium. The extensive VeRa data set enables us to study global scale atmospheric wave phenomena like thermal tides in the mesosphere and troposphere. A pronounced local time dependency of the temperature is found in the mesosphere at different altitude levels. Wave-2 structures dominate the low latitude range in the upper mesosphere while the higher latitudes show a strong wave-1 structure at the top of the cloud layer. The investigation of these wave structures provides valuable information about the energy transport in the atmosphere.

Ionospheric modification by radio waves: An overview and novel applications

NASA Astrophysics Data System (ADS)

Kosch, M. J.

2008-12-01

High-power high-frequency radio waves, when beamed into the Earth's ionosphere, can heat the plasma by particle collisions in the D-layer or generate wave-plasma resonances in the F-layer. These basic phenomena have been used in many research applications. In the D-layer, ionospheric currents can be modulated through conductance modification to produce artificial ULF and VLF waves, which propagate allowing magnetospheric research. In the mesopause, PMSE can be modified allowing dusty plasma research. In the F-layer, wave-plasma interactions generate a variety of artificially stimulated phenomena, such as (1) magnetic field-aligned plasma irregularities linked to anomalous radio wave absorption, (2) stimulated electromagnetic emissions linked to upper-hybrid resonance, (3) optical emissions linked to electron acceleration and collisions with neutrals, and (4) Langmuir turbulence linked to enhanced radar backscatter. These phenomena are reviewed. In addition, some novel applications of ionospheric heaters will be presented, including HF radar sounding of the magnetosphere, the production of E-region optical emissions, and measurements of D-region electron temperature for controlled PMSE research.

Roles Played by Electrostatic Waves in Producing Radio Emissions

NASA Technical Reports Server (NTRS)

Cairns, Iver H.

2000-01-01

Processes in which electromagnetic radiation is produced directly or indirectly via intermediate waves are reviewed. It is shown that strict theoretical constraints exist for electrons to produce nonthermal levels of radiation directly by the Cerenkov or cyclotron resonances. In contrast, indirect emission processes in which intermediary plasma waves are converted into radiation are often favored on general and specific grounds. Four classes of mechanisms involving the conversion of electrostatic waves into radiation are linear mode conversion, hybrid linear/nonlinear mechanisms, nonlinear wave-wave and wave-particle processes, and radiation from localized wave packets. These processes are reviewed theoretically and observational evidence summarized for their occurrence. Strong evidence exists that specific nonlinear wave processes and mode conversion can explain quantitatively phenomena involving type III solar radio bursts and ionospheric emissions. On the other hand, no convincing evidence exists that magnetospheric continuum radiation is produced by mode conversion instead of nonlinear wave processes. Further research on these processes is needed.

Location of acoustic radiators and inversion for energy density using radio-frequency sources and thunder recordings

NASA Astrophysics Data System (ADS)

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

2011-12-01

We use radio frequency (VHF) pulse locations mapped with the New Mexico Tech Lightning Mapping Array (LMA) to study the distribution of thunder sources in lightning channels. A least squares inversion is used to fit channel acoustic energy radiation with broadband (0.01 to 500 Hz) acoustic recordings using microphones deployed local (< 10 km) to the lightning. We model the thunder (acoustic) source as a superposition of line segments connecting the LMA VHF pulses. An optimum branching algorithm is used to reconstruct conductive channels delineated by VHF sources, which we discretize as a superposition of finely-spaced (0.25 m) acoustic point sources. We consider total radiated thunder as a weighted superposition of acoustic waves from individual channels, each with a constant current along its length that is presumed to be proportional to acoustic energy density radiated per unit length. Merged channels are considered as a linear sum of current-carrying branches and radiate proportionally greater acoustic energy. Synthetic energy time series for a given microphone location are calculated for each independent channel. We then use a non-negative least squares inversion to solve for channel energy densities to match the energy time series determined from broadband acoustic recordings across a 4-station microphone network. Events analyzed by this method have so far included 300-1000 VHF sources, and correlations as high as 0.5 between synthetic and recorded thunder energy were obtained, despite the presence of wind noise and 10-30 m uncertainty in VHF source locations.

The February 15 2011 CME-CME interaction and possibly associated radio emission

NASA Astrophysics Data System (ADS)

Magdalenic, Jasmina; Temmer, Manuela; Krupar, Vratislav; Marque, Christophe; Veronig, Astrid; Eastwood, Jonathan

2017-04-01

On February 15, 2011 a particular, continuum-like radio emission was observed by STEREO WAVES and WIND WAVES spacecraft. The radio event appeared to be associated with the complex interaction of two coronal mass ejections (CMEs) successively launched (February 14 and February 15) from the same active region. Although the CME-CME interaction was widely studied (e.g. Temmer et al., 2014, Maricic et al., 2014, Mishra & Srivastava, 2014) none of the analyses confirmed an association with the continuum-like radio emission. The usual method of establishing temporal coincidence of radio continuum and a CME-CME interaction is not applicable in this event due to a complex and long-lasting interaction of the CMEs. Therefore, we performed radio triangulation studies (see also Magdalenic et al., 2014) which provided us with the 3D source positions of the radio emission. Comparison of the positions of radio sources and the reconstructed positions of the interacting CMEs, shows that the source position of the continuum-like radio emission is about 0.5 AU away from the interacting CMEs. We can therefore concluded that, in this event, the continuum-like emission is not the radio signature of the CME-CME interaction.

Radio physics of the sun; Proceedings of the Symposium, University of Maryland, College Park, Md., August 7-10, 1979

NASA Technical Reports Server (NTRS)

Kundu, M. R. (Editor); Gergely, T. E.

1980-01-01

Papers are presented in the areas of the radio characteristics of the quiet sun and active regions, the centimeter, meter and decameter wavelength characteristics of solar bursts, space observations of low-frequency bursts, theoretical interpretations of solar active regions and bursts, joint radio, visual and X-ray observations of active regions and bursts, and the similarities of stellar radio characteristics to solar radio phenomena. Specific topics include the centimeter and millimeter wave characteristics of the quiet sun, radio fluctuations arising upon the transit of shock waves through the transition region, microwave, EUV and X-ray observations of active region loops and filaments, interferometric observations of 35-GHz radio bursts, emission mechanisms for radio bursts, the spatial structure of microwave bursts, observations of type III bursts, the statistics of type I bursts, and the numerical simulation of type III bursts. Attention is also given to the theory of type IV decimeter bursts, Voyager observations of type II and III bursts at kilometric wavelengths, radio and whitelight observations of coronal transients, and the possibility of obtaining radio observations of current sheets on the sun.

Optical Emissions Enhanced by O and X Mode Ionosphere HF Pumping: Similarities and Differences

NASA Astrophysics Data System (ADS)

Sergienko, T.; Brandstrom, U.; Gustavsson, B.; Blagoveshchenskaya, N. F.

2013-12-01

Strong enhancement of the optical emissions with excitation thresholds from 1.96 eV up to 18.75 eV have been observed during experiments of ionosphere modification by high power HF radio waves since the early 1970s. Up to now all these emissions were observed only during the interaction of the O-mode HF radio wave with the ionospheric plasma. On 19 October 2012, during an EISCAT heating experiment, strong optical emissions were observed by ALIS, in first time, for X-mode ionosphere pumping. While for O-mode heating the optical emission enhancements can be explained by the ionospheric electron heating and acceleration due to the nonlinear interaction of the powerful radio wave with ionosphere, the mechanism responsible for the emission enhancements during the X-mode heating is not known. In the experiment optical emissions have been measured in three different wave-lengths simultaneously from four ALIS stations. The emission intensity ratios as well as the characteristics of the spatial distribution of the enhanced optical emissions provide important information on the possible mechanisms of the radio wave - ionosphere interaction. In this report we present the results of comparison of the characteristics of the optical emissions caused by X-mode heating with the characteristics of the emissions enhanced by O-mode measured during same experiment.

Faraday Rotation of Automatic Dependent Surveillance-Broadcast (ADS-B) Signals as a Method of Ionospheric Characterization

NASA Astrophysics Data System (ADS)

Cushley, A. C.; Kabin, K.; Noël, J.-M.

2017-10-01

Radio waves propagating through plasma in the Earth's ambient magnetic field experience Faraday rotation; the plane of the electric field of a linearly polarized wave changes as a function of the distance travelled through a plasma. Linearly polarized radio waves at 1090 MHz frequency are emitted by Automatic Dependent Surveillance Broadcast (ADS-B) devices that are installed on most commercial aircraft. These radio waves can be detected by satellites in low Earth orbits, and the change of the polarization angle caused by propagation through the terrestrial ionosphere can be measured. In this manuscript we discuss how these measurements can be used to characterize the ionospheric conditions. In the present study, we compute the amount of Faraday rotation from a prescribed total electron content value and two of the profile parameters of the NeQuick ionospheric model.

Juno Listens to Jupiter Auroras Sing

NASA Image and Video Library

2016-09-02

During its close flyby of Jupiter on August 27, 2016, the Waves instrument on NASA's Juno spacecraft received radio signals associated with the giant planet's very intense auroras. This video displays these radio emissions in a format similar to a voiceprint, showing the intensity of radio waves as a function of frequency and time. The largest intensities are indicated in warmer colors. The frequency range of these signals is from 7 to 140 kilohertz. Radio astronomers call these "kilometric emissions" because their wavelengths are about a kilometer long. The time span of this data is 13 hours, beginning shortly after Juno's closest approach to Jupiter. Accompanying this data display is an audio rendition of the radio emissions, shifted into a lower register since the radio waves are well above the audio frequency range. In the video, a cursor moves from left to right to mark the time as the sounds are heard. These radio emissions were among the first observed by early radio astronomers in the 1950s. However, until now, they had not been observed from closely above the auroras themselves. From its polar orbit vantage point, Juno has -- for the first time -- enabled observations of these emissions from very close range. The Juno team believes that Juno flew directly through the source regions for some of these emissions during this flyby, which was Juno's first with its sensors actively collecting data. A movie is available at http://photojournal.jpl.nasa.gov/catalog/PIA21037

Reading Hertz's Own Dipole Theory

ERIC Educational Resources Information Center

Anicin, B. A.

2008-01-01

It is well known that the discoverer of radio waves, Heinrich Hertz, was the first man to apply Maxwell's electrodynamic theory to a problem in radio wave propagation. In this paper, we scrutinize his near-field lines of force using computers and his theory. In one of his four figures, a feature was found which was not to be obtained by…

PLASMA ENERGIZATION

DOEpatents

Furth, H.P.; Chambers, E.S.

1962-03-01

BS>A method is given for ion cyclotron resonance heatthg of a magnetically confined plasma by an applied radio-frequency field. In accordance with the invention, the radiofrequency energy is transferred to the plasma without the usual attendent self-shielding effect of plasma polarlzatlon, whereby the energy transfer is accomplished with superior efficiency. More explicitly, the invention includes means for applying a radio-frequency electric field radially to an end of a plasma column confined in a magnetic mirror field configuration. The radio-frequency field propagates hydromagnetic waves axially through the column with the waves diminishing in an intermediate region of the column at ion cyclotron resonance with the fleld frequency. In such region the wave energy is converted by viscous damping to rotational energy of the plasma ions. (AEC)

Solar--geophysical data. Prompt reports. [Number 405, May 1978. Data for A/pril 1978--March 1978

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coffey, H.E.

1978-05-01

This prompt report provides data for April 1978 on alert period, daily solar indices, solar flares, solar radio waves, solar x-ray radiation, coronal holes, inferred IP magnetic field polarities, mean solar magnetic field, solar wind measurements, geomagnetic substorms, and magnetograms of geomagnetic storm. It also provides data for March 1978 on daily solar activity center, sudden ionospheric disturbances, solar x-ray radiation, solar radio waves, cosmic rays, geomagnetic indices and radio propagation indices. A new data page lists the North American magnetometer network.

INSPIRE: A VLF Radio Project for High School Students

ERIC Educational Resources Information Center

Marshall, Jill A.; Pine, Bill; Taylor, William W. L.

2007-01-01

Since 1988 the Interactive NASA Space Physics Ionospheric Radio Experiment, or INSPIRE, has given students the opportunity to build research-quality VLF radio receivers and make observations of both natural and stimulated radio waves in the atmosphere. Any high school science class is eligible to join the INSPIRE volunteer observing network and…

Making Waves: Pirate Radio and Popular Music.

ERIC Educational Resources Information Center

Jones, Steve

The history of pirate radio--radio broadcasts offered by unlicensed broadcasters as alternatives to licensed, commercial radio programming--is difficult to trace, both in America and the United Kingdom (UK) since mention of pirate broadcasts of a less-then-thrilling nature are rarely found. Also, until 1927, the U.S. government did not formally…

Analytical study of nighttime scintillations using GPS at low latitude station Bhopal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maski, Kalpana, E-mail: k-maski@rediffmail.com; Vijay, S. K.

2015-07-31

Sporadically structured ionosphere (i.e. in-homogeneities in refractive index) can cause fluctuations (due to refraction effects) on the radio signal that is passing through it. These fluctuations are called ionospheric scintillations. Low latitude region is suitable for studying these scintillations. The influence of the ionosphere on the propagation of the radio wave becomes very marked with reference to communication or navigational radio system at very low frequency (VLF) to a high frequency (HF), which operate over the distances of 1000 km or more. Radio wave communication at different frequencies depends on structure of the ionosphere. With the advent of the artificialmore » satellites, they are used as a prime mode of radio wave communication. Some natural perturbation termed as irregularities, are present in the form of electron density of the ionosphere that cause disruption in the radio and satellite communications. Therefore the study of the ionospheric irregularities is of practical importance, if one wishes to understand the upper atmosphere completely. In order to make these communications uninterrupted the knowledge of irregularities, which are present in the ionosphere are very important. These irregularities can be located and estimated with the help of Ionospheric TEC and Scintillation. Scintillation is generally confined to nighttime hours, particularly around equatorial and low latitudes.« less

Vela X: A plerion or part of a shell?

NASA Astrophysics Data System (ADS)

Gvaramadze, V. V.

1998-03-01

An analysis of the radio, optical, and X-ray observations of the supernova remnant (SNR) in Vela has led us to conclude that the radio source Vela X is part of the SNR shell. The high brightness of this radio source is assumed to be a result of the interaction of dome-shaped deformations (bubbles) on the SNR shell, which gives rise to bright radio filaments. The deformations could be produced by Richtmaier-Meshkov's instability, which develops during the impulsive acceleration of a shell of gas (swept up from the interstellar medium by the wind from a presupernova) by a shock wave (generated by a supernova explosion). The brightest radio filament and the X-ray jet extending along it are shown to be located in the region of interaction of two prominent bubbles on the SNR shell. We conclude that the X-ray jet, like Vela X, is part of the shell, and that it has its origin in the Mach reflection of two semispherical shock waves. Our estimate of the plasma temperature behind the front of the Mach wave matches the jet temperature. We also show that the large spread in the estimates of the spectral index for Vela X could be caused by the instrumental effect which arises during observations of extended radio sources with a nonuniform surface-brightness distribution.

Reconfigurable Wideband Circularly Polarized Stacked Square Patch Antenna for Cognitive Radios

NASA Technical Reports Server (NTRS)

Barbosa Kortright, Miguel A.; Waldstein, Seth W.; Simons, Rainee N.

2017-01-01

An almost square patch, a square patch and a stacked square patch with corner truncation for circular polarization (CP) are researched and developed at X-band for cognitive radios. Experimental results indicate, first, that the impedance bandwidth of a CP almost square patch fed from the edge by a 50 ohm line is 1.70 percent and second, that of a CP square patch fed from the ground plane side by a surface launch connector is 1.87 percent. Third, the impedance bandwidth of a CP stacked square patch fed by a surface launch connector is 2.22 percent. The measured center frequency for the CP square patch fed by a surface launch connector without and with an identical stacked patch is 8.45 and 8.1017 GHz, respectively. By stacking a patch, separated by a fixed air gap of 0.254 mm, the center frequency is observed to shift by as much as 348.3 MHz. The shift in the center frequency can be exploited to reconfigure the operating frequency by mechanically increasing the air gap. The results indicate that a tuning bandwidth of about 100 MHz can be achieved when the distance of separation between the driven patch and the stacked patch is increased from its initial setting of 0.254 to 1.016 mm.

Reconfigurable Wideband Circularly Polarized Stacked Square Patch Antenna for Cognitive Radios

NASA Technical Reports Server (NTRS)

Barbosa Kortright, Miguel A.; Waldstein, Seth W.; Simons, Rainee N.

2017-01-01

An almost square patch, a square patch and a stacked square patch with corner truncation for circular polarization (CP) are researched and developed at X-band for cognitive radios. Experimental results indicate, first, that the impedance bandwidth of a CP almost square patch fed from the edge by a 50 ohm line is 1.70% and second, that of a CP square patch fed from the ground plane side by a surface launch connector is 1.87%. Third, the impedance bandwidth of a CP stacked square patch fed by a surface launch connector is 2.22%. The measured center frequency for the CP square patch fed by a surface launch connector without and with an identical stacked patch is 8.45 and 8.1017 GHz, respectively. By stacking a patch, separated by a fixed air gap of 0.254 mm, the center frequency is observed to shift by as much as 348.3 MHz. The shift in center frequency, brought about by the reconfiguring of the physical layer antenna, can be exploited in a cognitive system since it expands the usable frequency spectrum for software reconfiguration in the presence of interference. In addition, varying the fixed air gap in the stacked antenna geometry by increments of 0.254 mm further expands the usable frequency spectrum.

DEMONSTRATION BULLETIN: RADIO FREQUENCY HEATING - IIT RESEARCH INSTITUTE

EPA Science Inventory

Radio frequency heating (RFH) is a process that uses electromagnetic energy generated by radio waves to heat soil in situ, thereby potentially enhancing the performance of standard soil vapor extraction (SVE) technologies. An RFH system developed by the IIT Research Institute ...

Density Waves in Saturn's Rings from Cassini Radio Occultations

NASA Astrophysics Data System (ADS)

French, R. G.; Rappaport, N. J.; Marouf, E. A.; McGhee, C. A.

2005-12-01

The Cassini Radio Science Team conducted a set of optimized diametric occultations by Saturn and its rings from May to September 2005, providing 11 separate probes of Saturn's ionosphere and atmosphere, and 12 optical depth profiles of the complete ring system. Each event was observed by the stations of the Deep Space Net (DSN) at three radio frequencies (S, X, Ka bands, with corresponding wavelengths of ? = 13, 3.6, and 0.9 cm). Very accurate pointing by the spacecraft and ground antennas resulted in stable baseline signal levels, and the relatively large ring opening angle (B=19-25°) permitted us to probe even quite dense ring regions with excellent SNR. The RSS occultation technique enables us to recover very fine detailed radial structure by correcting for diffraction effects. Multiple occultation chords, covering a variety of ring longitudes and ring opening angles, reveal the structure of the rings in remarkable detail, including density and bending waves, satellite wakes, and subtle variations at the 100-m radius scale. Janus and Epimetheus are responsible for a particularly rich set of density waves, and their coorbital interactions result in a complex interplay of time-variable ring structure over the 8-year libration period of the two satellites. We compare the first-order 2:1, 4:3, 5:4, and 6:5 coorbital density waves from multiple occultation chords to linear density wave models based on a dynamical model of the orbital exchange between the moons. From the observed dispersion relation of the wave crests, we infer the surface mass density and eccentricity gradient of particle streamlines, and match the detailed shapes of the wave crests using a non-linear analysis. Second-order coorbital features are also evident, and there are even hints of third-order density waves in the high SNR radio occultation data.

Transient dynamics of secondary radiation from an HF pumped magnetized space plasma

NASA Astrophysics Data System (ADS)

Norin, L.; Grach, S. M.; Thidé, B.; Sergeev, E. N.; Leyser, T. B.

2007-09-01

In order to systematically analyze the transient wave and radiation processes that are excited when a high-frequency (HF) radio wave is injected into a magnetized space plasma, we have measured the secondary radiation, or stimulated electromagnetic emission (SEE), from the ionosphere, preconditioned such that geomagnetic field-aligned plasma irregularities are already present. The transient dynamics experiments were made using a duty cycle of the HF radio wave of 200 ms (180 ms on and 20 ms off) and 100 ms (80 ms on and 20 ms off) for various frequencies near the fifth harmonic of the local ionospheric electron cyclotron frequency. Within the first 10 ms after the radio pulse turn-on, frequency downshifted structures of the SEE exhibit an overshoot with a maximum at 3 ms < t < 8 ms, whereas the upshifted spectral components do not exhibit this feature. The relative magnitude of the overshoot is strongly dependent on the frequency offset of the pump from the harmonic of the electron cyclotron frequency. A transient blue-shifted frequency component is identified. This component is upshifted from the pump by 14 kHz < Δ f < 55 kHz and exists only within the first 10 ms after the radio pulse turn-on. On a longer time scale we analyze the amplitude modulation, or ``ringing,'' of the reflected radio wave, (also known as ``quasi-periodic oscillations'' or ``spikes''). The ringing has a frequency of the order 15-20 Hz and we show that this phenomenon is also present in the SEE sidebands and is synchronized with the ringing of the reflected HF wave itself.

A Simple Demonstration for Exploring the Radio Waves Generated by a Mobile Phone

ERIC Educational Resources Information Center

Hare, Jonathan

2010-01-01

Described is a simple low cost home-made device that converts the radio wave energy from a mobile phone signal into electricity for lighting an LED. No battery or complex circuitry is required. The device can form the basis of a range of interesting experiments on the physics and technology of mobile phones. (Contains 5 figures.)

EFFECTS OF ALFVEN WAVES ON ELECTRON CYCLOTRON MASER EMISSION IN CORONAL LOOPS AND SOLAR TYPE I RADIO STORMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, G. Q.; Chen, L.; Wu, D. J.

Solar type I radio storms are long-lived radio emissions from the solar atmosphere. It is believed that these type I storms are produced by energetic electrons trapped within a closed magnetic structure and are characterized by a high ordinary (O) mode polarization. However, the microphysical nature of these emissions is still an open problem. Recently, Wu et al. found that Alfven waves (AWs) can significantly influence the basic physics of wave-particle interactions by modifying the resonant condition. Taking the effects of AWs into account, this work investigates electron cyclotron maser emission driven by power-law energetic electrons with a low-energy cutoffmore » distribution, which are trapped in coronal loops by closed solar magnetic fields. The results show that the emission is dominated by the O mode. It is proposed that this O mode emission may possibly be responsible for solar type I radio storms.« less

Open-loop radio science with a suppressed-carrier signal

NASA Technical Reports Server (NTRS)

Greenhall, C. A.

1980-01-01

When a suppressed-carrier signal is squared, the carrier reappears in doubled form. An open-loop receiver can be used to deliver a recording of a band-limited waveform containing this carrier, whose amplitude and phase can be tracked by the radio science experimenter.

47 CFR 5.5 - Definition of terms.

Code of Federal Regulations, 2013 CFR

2013-10-01

... Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL EXPERIMENTAL RADIO SERVICE General § 5.5 Definition of... Commission and specified in the instrument of authorization. Experimental radio service. A service in which... communications. Experimental station. A station utilizing radio waves in experiments with a view to the...

47 CFR 5.5 - Definition of terms.

Code of Federal Regulations, 2014 CFR

2014-10-01

... Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL EXPERIMENTAL RADIO SERVICE General § 5.5 Definition of... Commission and specified in the instrument of authorization. Experimental radio service. A service in which... communications. Experimental station. A station utilizing radio waves in experiments with a view to the...

A Simple Radio Receiver Aids Understanding of Wireless Communication

ERIC Educational Resources Information Center

Straulino, S.; Orlando, A.

2012-01-01

The basic theory of radio broadcasting is discussed from an experimental point of view. First, concepts like wave modulation and tuning are explained with the use of instruments in the physics laboratory. Then, a very basic radio receiver is described and assembled, whose most important feature, like in the old "crystal radios", is the absence of…

Unconscious intelligence in the universe

NASA Astrophysics Data System (ADS)

Raup, David M.

1987-10-01

It is argued that animals on other planets may have evolved, by natural selection, the ability to communicate by radio waves. Radio communication in such non-intelligent organisms would persist much longer than radio communication developed by intelligent beings, which would be ephemeral due to cultural changes. The search for SETI should take the possibility of such radio communication into account.

Full PIC simulations of solar radio emission

NASA Astrophysics Data System (ADS)

Sgattoni, A.; Henri, P.; Briand, C.; Amiranoff, F.; Riconda, C.

2017-12-01

Solar radio emissions are electromagnetic (EM) waves emitted in the solar wind plasma as a consequence of electron beams accelerated during solar flares or interplanetary shocks such as ICMEs. To describe their origin, a multi-stage model has been proposed in the 60s which considers a succession of non-linear three-wave interaction processes. A good understanding of the process would allow to infer the kinetic energy transfered from the electron beam to EM waves, so that the radio waves recorded by spacecraft can be used as a diagnostic for the electron beam.Even if the electrostatic problem has been extensively studied, full electromagnetic simulations were attempted only recently. Our large scale 2D-3V electromagnetic PIC simulations allow to identify the generation of both electrostatic and EM waves originated by the succession of plasma instabilities. We tested several configurations varying the electron beam density and velocity considering a background plasma of uniform density. For all the tested configurations approximately 105 of the electron-beam kinetic energy is transfered into EM waves emitted in all direction nearly isotropically. With this work we aim to design experiments of laboratory astrophysics to reproduce the electromagnetic emission process and test its efficiency.

Refraction of Radio Waves on the Radio-Occultation Satellite-to-Satellite Paths as a Characteristic of the Atmospheric State

NASA Astrophysics Data System (ADS)

Matyugov, S. S.; Yakovlev, O. I.; Pavelyev, A. G.; Pavelyev, A. A.; Anufriev, V. A.

2017-10-01

We present the results of analyzing the radio-wave refractive characteristics measured on the radio-occultation paths between the GPS navigation satellites and the FORMOSAT-3 research satellites in the central region of the European territory of Russia in 2007-2013. The diurnal, seasonal, and annual variations in the refraction angle at altitudes of 2 to 25 km are discussed. It is shown that the refraction angle can be used as an independent characteristic of the atmospheric state and its long-term variation trends. Diurnal and nocturnal variations in the refraction angle in the winter and summer seasons are analyzed. Trends in the atmospheric refraction variations over seven years are discussed.

Detectable radio flares following gravitational waves from mergers of binary neutron stars.

PubMed

Nakar, Ehud; Piran, Tsvi

2011-09-28

Mergers of neutron-star/neutron-star binaries are strong sources of gravitational waves. They can also launch subrelativistic and mildly relativistic outflows and are often assumed to be the sources of short γ-ray bursts. An electromagnetic signature that persisted for weeks to months after the event would strengthen any future claim of a detection of gravitational waves. Here we present results of calculations showing that the interaction of mildly relativistic outflows with the surrounding medium produces radio flares with peak emission at 1.4 gigahertz that persist at detectable (submillijansky) levels for weeks, out to a redshift of 0.1. Slower subrelativistic outflows produce flares detectable for years at 150 megahertz, as well as at 1.4 gigahertz, from slightly shorter distances. The radio transient RT 19870422 (ref. 11) has the properties predicted by our model, and its most probable origin is the merger of a compact neutron-star/neutron-star binary. The lack of radio detections usually associated with short γ-ray bursts does not constrain the radio transients that we discuss here (from mildly relativistic and subrelativistic outflows) because short γ-ray burst redshifts are typically >0.1 and the appropriate timescales (longer than weeks) have not been sampled.

Moreton wave, "EIT wave", and type II radio burst as manifestations of a single wave front

NASA Astrophysics Data System (ADS)

Kuzmenko, I. V.; Grechnev, V. V.; Uralov, A. M.

2011-12-01

We show that a Moreton wave, an "EIT wave," and a type II radio burst observed during a solar flare of July 13, 2004, might have been a manifestation of a single front of a decelerating shock wave, which appeared in an active region (AR) during a filament eruption. We propose describing a quasi-spheroidal wave propagating upward and along the solar surface by using relations known from a theory of a point-like explosion in a gas whose density changes along the radius according to a power law. By applying this law to fit the drop in density of the coronal plasma enveloping the solar active region, we first managed to bring the measured positions and velocities of surface Moreton wave and "EIT wave" into correspondence with the observed frequency drift rate of the meter type II radio burst. The exponent of the vertical coronal density falloff is selected by fitting the power law to the Newkirk and Saito empirical distributions in the height range of interest. Formal use of such a dependence in the horizontal direction with a different exponent appears to be reasonable up to distances of less than 200 Mm around the eruption center. It is possible to assume that the near-surface shock wave weakens when leaving this radius and finally the active region, entering the region of the quiet Sun where the coronal plasma density and the fast-mode speed are almost constant along the horizontal.

Geospace ionosphere research with a MF/HF radio instrument on a cubesat

NASA Astrophysics Data System (ADS)

Kallio, E. J.; Aikio, A. T.; Alho, M.; Fontell, M.; van Gijlswijk, R.; Kauristie, K.; Kestilä, A.; Koskimaa, P.; Makela, J. S.; Mäkelä, M.; Turunen, E.; Vanhamäki, H.

2016-12-01

Modern technology provides new possibilities to study geospace and its ionosphere, using spacecraft and and computer simulations. A type of nanosatellites, CubeSats, provide a cost effective possibility to provide in-situ measurements in the ionosphere. Moreover, combined CubeSat observations with ground-based observations gives a new view on auroras and associated electromagnetic phenomena. Especially joint and active CubeSat - ground based observation campaigns enable the possibility of studying the 3D structure of the ionosphere. Furthermore using several CubeSats to form satellite constellations enables much higher temporal resolution. At the same time, increasing computation capacity has made it possible to perform simulations where properties of the ionosphere, such as propagation of the electromagnetic waves in the medium frequency, MF (0.3-3 MHz) and high frequency, HF (3-30 MHz), ranges is based on a 3D ionospheric model and on first-principles modelling. Electromagnetic waves at those frequencies are strongly affected by ionospheric electrons and, consequently, those frequencies can be used for studying the plasma. On the other hand, even if the ionosphere originally enables long-range telecommunication at MF and HF frequencies, the frequent occurrence of spatiotemporal variations in the ionosphere disturbs communication channels, especially at high latitudes. Therefore, study of the MF and HF waves in the ionosphere has both a strong science and technology interests. We present computational simulation results and measuring principles and techniques to investigate the arctic ionosphere by a polar orbiting CubeSat whose novel AM radio instrument measures HF and MF waves. The cubesat, which contains also a white light aurora camera, is planned to be launched in 2017 (http://www.suomi100satelliitti.fi/eng). We have modelled the propagation of the radio waves, both ground generated man-made waves and space formed space weather related waves, through the 3D arctic ionosphere with (1) a new 3D ray tracing model and (2) a new 3D full kinetic electromagnetic simulation. These simulations are used to analyse the origin of the radio waves observed by the MH/HF radio instrument and, consequently, to derive information about the 3D ionosphere and its spatial and temporal variations.

Ground and space observations of medium frequency auroral radio emissions

NASA Astrophysics Data System (ADS)

Broughton, Matthew C.

The auroral zone is a rich source of natural radio emissions that can be observed in space and at ground-level. By studying these waves, scientists can gain insight into the plasma processes that generate them and use the near-Earth space environment as a large-scale plasma physics laboratory. This thesis uses both ground-level and in situ observations to study two kinds of natural radio emissions. First, we report observations of a new kind of auroral radio emission. The waves have frequencies ranging from 1.3-2.2 MHz, bandwidths ranging from 90-272 kHz, and durations ranging from 16-355 s. Spectral analysis of the waveform data has revealed that the emission has a complex combination of at least three kinds of fine structures. For model auroral electron distributions, calculations indicate that Langmuir waves could be excited at frequencies consistent with observations. The remainder of the thesis discusses auroral medium frequency (MF) burst, an impulsive, broadband natural radio emission observed at ground-level within a few minutes of local substorm onset. LaBelle [2011] proposed that MF burst originates as Langmuir/Z-mode waves on the topside of the ionosphere that subsequently mode convert to L-mode waves and propagate to ground-level. Using continuous waveform measurements and combined observations with the Sondrestrom Incoherent Scatter Radar, we have performed two tests of this mechanism. The results of these tests are consistent with the mechanism described in LaBelle [2011]. A survey of 8,624 half-orbits of the DEMETER spacecraft has revealed 68 observations of bursty MF waves. We have compared the wave properties of these waves to those of MF burst and have found that although it is uncertain, the balance of the evidence suggests that the bursty MF waves observed with DEMETER are the same phenomenon as the ground-level MF burst. Finally, we have used numerical simulations to model both the fine structure of MF burst and to estimate the attenuation the waves would experience due to Landau damping on the topside ionosphere and mode conversion on the bottomside ionosphere. The amount of Landau damping is sensitive to the ratio of secondary to background electrons nse/ne0. Ignoring collisional damping in the lower ionosphere, these calculations suggest that for nse/n e0<0.4%, 0.01-45% of the initial Langmuir wave power would reach ground-level. The above experimental and numerical studies constrain the conditions under which MF burst could plausibly originate as Langmuir/Z-mode waves on the topside of the ionosphere.

Radio-wave detection of ultra-high-energy neutrinos and cosmic rays

NASA Astrophysics Data System (ADS)

Huege, Tim; Besson, Dave

2017-12-01

Radio waves, perhaps because our terrestrial atmosphere and the cosmos beyond are uniquely transparent to them, or perhaps because they are macroscopic, so the basic instruments of detection (antennas) are easily constructible, arguably occupy a privileged position within the electromagnetic spectrum, and, correspondingly, receive disproportionate attention experimentally. Detection of radio-frequency radiation, at macroscopic wavelengths, has blossomed within the last decade as a competitive method for the measurement of cosmic particles, particularly charged cosmic rays and neutrinos. Cosmic-ray detection via radio emission from extensive air showers has been demonstrated to be a reliable technique that has reached a reconstruction quality of the cosmic-ray parameters competitive with more traditional approaches. Radio detection of neutrinos in dense media seems to be the most promising technique to achieve the gigantic detection volumes required to measure neutrinos at energies beyond the PeV-scale flux established by IceCube. In this article, we review radio detection both of cosmic rays in the atmosphere, as well as neutrinos in dense media.

A Minimal Radio and Plasma Wave Investigation For a Mercury Orbiter Mission

NASA Technical Reports Server (NTRS)

Kurth, W. S.

2001-01-01

The primary thrust of the effort at The University of Iowa for the definition of an orbiter mission to Mercury is a minimum viable radio and plasma wave investigation. While it is simple to add sensors and capability to any payload, the challenge is to do reasonable science within limited resources; and viable missions to Mercury are especially limited in payload mass. For a wave investigation, this is a serious concern, as the sensor mass often makes up a significant fraction of the instrumentation mass.

Diffuse Interplanetary Radio Emission (DIRE) Accompanying Type II Radio Bursts

NASA Astrophysics Data System (ADS)

Teklu, T. B.; Gopalswamy, N.; Makela, P. A.; Yashiro, S.; Akiyama, S.; Xie, H.

2015-12-01

We report on an unusual drifting feature in the radio dynamic spectra at frequencies below 14 MHz observed by the Radio and Plasma Wave (WAVES) experiment on board the Wind spacecraft. We call this feature as "Diffuse Interplanetary Radio Emission (DIRE)". The DIRE events are generally associated with intense interplanetary type II radio bursts produced by shocks driven by coronal mass ejections (CMEs). DIREs drift like type II bursts in the dynamic spectra, but the drifting feature consist of a series of short-duration spikes (similar to a type I chain). DIREs occur at higher frequencies than the associated type II bursts, with no harmonic relationship with the type II burst. The onset of DIREs is delayed by several hours from the onset of the eruption. Comparing the radio dynamic spectra with white-light observations from the Solar and Heliospheric Observatory (SOHO) mission, we find that the CMEs are generally very energetic (fast and mostly halos). We suggest that the DIRE source is typically located at the flanks of the CME-driven shock that is still at lower heliocentric distances.

A study of electron density profiles in relation to ionization sources and ground-based radio wave absorption measurements, part 1

NASA Technical Reports Server (NTRS)

Gnanalingam, S.; Kane, J. A.

1973-01-01

An extensive set of ground-based measurements of the diurnal variation of medium frequency radio wave adsorption and virtual height is analyzed in terms of current understanding of the D- and lower E-region ion production and loss process. When this is done a gross discrepancy arises, the source of which is not known.

Two-Stage Design Method for Enhanced Inductive Energy Transmission with Q-Constrained Planar Square Loops.

PubMed

Eteng, Akaa Agbaeze; Abdul Rahim, Sharul Kamal; Leow, Chee Yen; Chew, Beng Wah; Vandenbosch, Guy A E

2016-01-01

Q-factor constraints are usually imposed on conductor loops employed as proximity range High Frequency Radio Frequency Identification (HF-RFID) reader antennas to ensure adequate data bandwidth. However, pairing such low Q-factor loops in inductive energy transmission links restricts the link transmission performance. The contribution of this paper is to assess the improvement that is reached with a two-stage design method, concerning the transmission performance of a planar square loop relative to an initial design, without compromise to a Q-factor constraint. The first stage of the synthesis flow is analytical in approach, and determines the number and spacing of turns by which coupling between similar paired square loops can be enhanced with low deviation from the Q-factor limit presented by an initial design. The second stage applies full-wave electromagnetic simulations to determine more appropriate turn spacing and widths to match the Q-factor constraint, and achieve improved coupling relative to the initial design. Evaluating the design method in a test scenario yielded a more than 5% increase in link transmission efficiency, as well as an improvement in the link fractional bandwidth by more than 3%, without violating the loop Q-factor limit. These transmission performance enhancements are indicative of a potential for modifying proximity HF-RFID reader antennas for efficient inductive energy transfer and data telemetry links.

Research in space physics at the University of Iowa. [energetic particles and electric, magnetic, and electromagnetic fields

NASA Technical Reports Server (NTRS)

Vanallen, J. A.

1978-01-01

Specific fields of current investigation by satellite observation and ground-based radio-astronomical and optical techniques are discussed. Topics include: aspects of energetic particles trapped in the earth's magnetic field and transiently present in the outer magnetosphere and the solar, interplanetary, and terrestrial phenomena associated with them; plasma flows in the magnetosphere and the ionospheric effects of particle precipitation, with corresponding studies of the magnetosphere of Jupiter, Saturn, and possibly Uranus; the origin and propagation of very low frequency radio waves in the earth's magnetosphere and ionosphere; solar particle emissions and their interplanetary propagation and acceleration; solar modulation and the heliocentric radial dependence of the intensity of galactic cosmic rays; radio frequency emissions from the quintescent and flaring sun; shock waves in the interplanetary medium; radio emissions from Jupiter; and radio astronomy of pulsars, flare stars, and other stellar sources.

World War II Radar and Early Radio Astronomy

NASA Astrophysics Data System (ADS)

Smith, G.

2005-08-01

The pattern of radio astronomy which developed in Europe and Australia followed closely the development of metre wave radar in World War II. The leading pioneers, Ryle, Lovell, Hey and Pawsey, were all in radar research establishments in the UK and Australia. They returned to universities, recruited their colleagues into research groups and immediately started on some basic observations of solar radio waves, meteor echoes, and the galactic background. There was at first little contact with conventional astronomers. This paper traces the influence of the radar scientists and of several types of radar equipment developed during WW II, notably the German Wurzburg, which was adapted for radio research in several countries. The techniques of phased arrays and antenna switching were used in radar and aircraft installations. The influence of WW II radar can be traced at least up to 10 years after the War, when radio astronomy became accepted as a natural discipline within astronomy.

Radio polarisation measurements of meteor trail echoes with BRAMS

NASA Astrophysics Data System (ADS)

Lamy, H.; Ranvier, S.; Anciaux, M.; Calders, S.; De Keyser, J.; Gamby, E.

2012-04-01

BRAMS, the Belgian RAdio Meteor Stations, is a network of radio receiving stations using forward scatter techniques to detect and characterize meteors. The transmitter is a dedicated beacon located in Dourbes in the south-west of Belgium. It emits towards the zenith a purely sinusoidal wave circularly polarised, at a frequency of 49.97 MHz and with a power of 150 watts. The main goals of the project are to compute meteoroid flux rates and trajectories. Most receiving stations are using a 3 element Yagi antenna and are therefore only sensitive to one polarisation. The station located in Uccle has also a crossed 3 element Yagi antenna and therefore allows measurements of horizontal and vertical polarisations. We present the preliminary radio polarisation measurements of meteor trail echoes and compare them with the theoretical predictions of Jones & Jones (1991) for oblique scattering of radio waves from meteor trails.

NONCOHERENT MECHANISMS OF SPORADIC SOLAR RADIO EMISSION IN THE CASE OF A MAGNETOACTIVE CORONAL PLASMA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ginzburg, V.L.; Zheleznyakov, V.V.

1961-07-01

Noncoherent mechanisms of sporadic solar radiofrequency emission are discussed, with the effect of magnetic field taken into account. The emission is designated conventionally as noncoherent emission when the intensities contributed by discrete particles may be combined additively with reabsorption taken into account, while intensification of waves in the system itself (e.g., in the stream of particles) is negligible. It is shown that noncoherent mechanisms may be held responsible for enhanced radio emission above sunspots, and for type IV and type V solar radio bursts. Solar radio bursts of types I, II, and III cannot be related to noncoherent radio emissionmore » of either the synchrotron radiation or the Cherehkov radiation variety. It is also shown that type II and type III bursts may not be related to the noncoherent emission of plasma waves in an isotropic plasma. (auth)« less

Genetic programming applied to RFI mitigation in radio astronomy

NASA Astrophysics Data System (ADS)

Staats, K.

2016-12-01

Genetic Programming is a type of machine learning that employs a stochastic search of a solutions space, genetic operators, a fitness function, and multiple generations of evolved programs to resolve a user-defined task, such as the classification of data. At the time of this research, the application of machine learning to radio astronomy was relatively new, with a limited number of publications on the subject. Genetic Programming had never been applied, and as such, was a novel approach to this challenging arena. Foundational to this body of research, the application Karoo GP was developed in the programming language Python following the fundamentals of tree-based Genetic Programming described in "A Field Guide to Genetic Programming" by Poli, et al. Karoo GP was tasked with the classification of data points as signal or radio frequency interference (RFI) generated by instruments and machinery which makes challenging astronomers' ability to discern the desired targets. The training data was derived from the output of an observation run of the KAT-7 radio telescope array built by the South African Square Kilometre Array (SKA-SA). Karoo GP, kNN, and SVM were comparatively employed, the outcome of which provided noteworthy correlations between input parameters, the complexity of the evolved hypotheses, and performance of raw data versus engineered features. This dissertation includes description of novel approaches to GP, such as upper and lower limits to the size of syntax trees, an auto-scaling multiclass classifier, and a Numpy array element manager. In addition to the research conducted at the SKA-SA, it is described how Karoo GP was applied to fine-tuning parameters of a weather prediction model at the South African Astronomical Observatory (SAAO), to glitch classification at the Laser Interferometer Gravitational-wave Observatory (LIGO), and to astro-particle physics at The Ohio State University.

ON HIGHLY CLUMPED MAGNETIC WIND MODELS FOR COOL EVOLVED STARS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harper, G. M.

2010-09-10

Recently, it has been proposed that the winds of non-pulsating and non-dusty K and M giants and supergiants may be driven by some form of magnetic pressure acting on highly clumped wind material. While many researchers believe that magnetic processes are responsible for cool evolved stellar winds, existing MHD and Alfven wave-driven wind models have magnetic fields that are essentially radial and tied to the photosphere. The clumped magnetic wind scenario is quite different in that the magnetic flux is also being carried away from the star with the wind. We test this clumped wind hypothesis by computing continuum radiomore » fluxes from the {zeta} Aur semiempirical model of Baade et al., which is based on wind-scattered line profiles. The radio continuum opacity is proportional to the electron density squared, while the line scattering opacity is proportional to the gas density. This difference in proportionality provides a test for the presence of large clumping factors. We derive the radial distribution of clump factors (CFs) for {zeta} Aur by comparing the nonthermal pressures required to produce the semiempirical velocity distribution with the expected thermal pressures. The CFs are {approx}5 throughout the sub-sonic inner wind region and then decline outward. These implied clumping factors lead to excess radio emission at 2.0 cm, while at 6.2 cm it improves agreement with the smooth unclumped model. Smaller clumping factors of {approx}2 lead to better overall agreement but also increase the discrepancy at 2 cm. These results do not support the magnetic clumped wind hypothesis and instead suggest that inherent uncertainties in the underlying semiempirical model probably dominate uncertainties in predicted radio fluxes. However, new ultraviolet line and radio continuum observations are needed to test the new generations of inhomogeneous magnetohydrodynamic wind models.« less

High-frequency matrix converter with square wave input

DOEpatents

Carr, Joseph Alexander; Balda, Juan Carlos

2015-03-31

A device for producing an alternating current output voltage from a high-frequency, square-wave input voltage comprising, high-frequency, square-wave input a matrix converter and a control system. The matrix converter comprises a plurality of electrical switches. The high-frequency input and the matrix converter are electrically connected to each other. The control system is connected to each switch of the matrix converter. The control system is electrically connected to the input of the matrix converter. The control system is configured to operate each electrical switch of the matrix converter converting a high-frequency, square-wave input voltage across the first input port of the matrix converter and the second input port of the matrix converter to an alternating current output voltage at the output of the matrix converter.

Robust sparse image reconstruction of radio interferometric observations with PURIFY

NASA Astrophysics Data System (ADS)

Pratley, Luke; McEwen, Jason D.; d'Avezac, Mayeul; Carrillo, Rafael E.; Onose, Alexandru; Wiaux, Yves

2018-01-01

Next-generation radio interferometers, such as the Square Kilometre Array, will revolutionize our understanding of the Universe through their unprecedented sensitivity and resolution. However, to realize these goals significant challenges in image and data processing need to be overcome. The standard methods in radio interferometry for reconstructing images, such as CLEAN, have served the community well over the last few decades and have survived largely because they are pragmatic. However, they produce reconstructed interferometric images that are limited in quality and scalability for big data. In this work, we apply and evaluate alternative interferometric reconstruction methods that make use of state-of-the-art sparse image reconstruction algorithms motivated by compressive sensing, which have been implemented in the PURIFY software package. In particular, we implement and apply the proximal alternating direction method of multipliers algorithm presented in a recent article. First, we assess the impact of the interpolation kernel used to perform gridding and degridding on sparse image reconstruction. We find that the Kaiser-Bessel interpolation kernel performs as well as prolate spheroidal wave functions while providing a computational saving and an analytic form. Secondly, we apply PURIFY to real interferometric observations from the Very Large Array and the Australia Telescope Compact Array and find that images recovered by PURIFY are of higher quality than those recovered by CLEAN. Thirdly, we discuss how PURIFY reconstructions exhibit additional advantages over those recovered by CLEAN. The latest version of PURIFY, with developments presented in this work, is made publicly available.

Study on THz wave generation from air plasma induced by quasi-square Airy beam

NASA Astrophysics Data System (ADS)

Zhang, Shijing; Zhang, Liangliang; Jiang, Guangtong; Zhang, Cunlin; Zhao, Yuejin

2018-01-01

Terahertz (THz) wave has attracted considerable attention in recent years because of its potential applications. The intense THz waves generated from air plasma induced by two-color femtosecond laser are widely used due to its high generation efficiency and broad frequency bandwidth. The parameters of the laser change the distribution of the air plasma, and then affect the generation of THz wave. In this research, we investigate the THz wave generation from air plasma induced by quasi-square Airy beam. Unlike the common Gauss beam, the quasi-square Airy beam has ability to autofocus and to increase the maximum intensity at the focus. By using the spatial light modulator (SLM), we can change the parameters of phase map to control the shape of the Airy beam. We obtain the two-color laser field by a 100-um-thick BBO crystal, then use a Golay detector to record THz wave energy. By comparing terahertz generation at different modulation depths, we find that terahertz energy produced by quasi-square Airy beam is up to 3.1 times stronger than that of Gauss beam with identical laser energy. In order to understand the influence of quasi-square Airy beam on the BBO crystal, we record THz wave energy by changing the azimuthal angle of BBO crystal with Gauss beam and Airy beam at different modulation depths. We find that the trend of terahertz energy with respect to the azimuthal angle of the BBO crystal keeps the same for different laser beams. We believe that the quasi-square Airy beam or other auto focusing beam can significantly improve the efficiency of terahertz wave generation and pave the way for its applications.

Ionospheric Impacts on UHF Space Surveillance

NASA Astrophysics Data System (ADS)

Jones, J. C.

2017-12-01

Earth's atmosphere contains regions of ionized plasma caused by the interaction of highly energetic solar radiation. This region of ionization is called the ionosphere and varies significantly with altitude, latitude, local solar time, season, and solar cycle. Significant ionization begins at about 100 km (E layer) with a peak in the ionization at about 300 km (F2 layer). Above the F2 layer, the atmosphere is mostly ionized but the ion and electron densities are low due to the unavailability of neutral molecules for ionization so the density decreases exponentially with height to well over 1000 km. The gradients of these variations in the ionosphere play a significant role in radio wave propagation. These gradients induce variations in the index of refraction and cause some radio waves to refract. The amount of refraction depends on the magnitude and direction of the electron density gradient and the frequency of the radio wave. The refraction is significant at HF frequencies (3-30 MHz) with decreasing effects toward the UHF (300-3000 MHz) range. UHF is commonly used for tracking of space objects in low Earth orbit (LEO). While ionospheric refraction is small for UHF frequencies, it can cause errors in range, azimuth angle, and elevation angle estimation by ground-based radars tracking space objects. These errors can cause significant errors in precise orbit determinations. For radio waves transiting the ionosphere, it is important to understand and account for these effects. Using a sophisticated radio wave propagation tool suite and an empirical ionospheric model, we calculate the errors induced by the ionosphere in a simulation of a notional space surveillance radar tracking objects in LEO. These errors are analyzed to determine daily, monthly, annual, and solar cycle trends. Corrections to surveillance radar measurements can be adapted from our simulation capability.

Properties of Langmuir wave bursts associated with magnetic holes

NASA Technical Reports Server (NTRS)

MacDowall, R. J.; Lin, N.; Kellogg, P. J.; Phillips, J. L.; Neugebauer, M.; Balogh, A.; Forsyth, R. J.

1995-01-01

The radio and plasma wave receivers on the Ulysses spacecraft have detected thousands of short-duration bursts of waves at approximately the electron plasma frequency. These wave events believed to be Langmuir waves are usually less than approximately 5 minutes in duration. They occur in or at the boundaries of depletions in the magnetic field amplitude known as magnetic holes. Using the 16 sec time resolution provided by the plasma frequency receiver, it is possible to examine the density structure inside of magnetic holes. Even higher time resolutions are sometimes available from the radio receiver data. The Ulysses observations show that these wave bursts occur more frequently at high heliographic latitudes; the occurrence rates depend on both latitude and distance from the Sun. We review the statistics for the wave events, compare them to magnetic and plasma parameters, and review the reasons for the more frequent occurrence at high heliographic latitudes.

Observation of beat oscillation generation by coupled waves associated with parametric decay during radio frequency wave heating of a spherical tokamak plasma.

PubMed

Nagashima, Yoshihiko; Oosako, Takuya; Takase, Yuichi; Ejiri, Akira; Watanabe, Osamu; Kobayashi, Hiroaki; Adachi, Yuuki; Tojo, Hiroshi; Yamaguchi, Takashi; Kurashina, Hiroki; Yamada, Kotaro; An, Byung Il; Kasahara, Hiroshi; Shimpo, Fujio; Kumazawa, Ryuhei; Hayashi, Hiroyuki; Matsuzawa, Haduki; Hiratsuka, Junichi; Hanashima, Kentaro; Kakuda, Hidetoshi; Sakamoto, Takuya; Wakatsuki, Takuma

2010-06-18

We present an observation of beat oscillation generation by coupled modes associated with parametric decay instability (PDI) during radio frequency (rf) wave heating experiments on the Tokyo Spherical Tokamak-2. Nearly identical PDI spectra, which are characterized by the coexistence of the rf pump wave, the lower-sideband wave, and the low-frequency oscillation in the ion-cyclotron range of frequency, are observed at various locations in the edge plasma. A bispectral power analysis was used to experimentally discriminate beat oscillation from the resonant mode for the first time. The pump and lower-sideband waves have resonant mode components, while the low-frequency oscillation is exclusively excited by nonlinear coupling of the pump and lower-sideband waves. Newly discovered nonlocal transport channels in spectral space and in real space via PDI are described.

Low frequency AC waveform generator

DOEpatents

Bilharz, Oscar W.

1986-01-01

Low frequency sine, cosine, triangle and square waves are synthesized in circuitry which allows variation in the waveform amplitude and frequency while exhibiting good stability and without requiring significant stabilization time. A triangle waveform is formed by a ramped integration process controlled by a saturation amplifier circuit which produces the necessary hysteresis for the triangle waveform. The output of the saturation circuit is tapped to produce the square waveform. The sine waveform is synthesized by taking the absolute value of the triangular waveform, raising this absolute value to a predetermined power, multiplying the raised absolute value of the triangle wave with the triangle wave itself and properly scaling the resultant waveform and subtracting it from the triangular waveform itself. The cosine is synthesized by squaring the triangular waveform, raising the triangular waveform to a predetermined power and adding the squared waveform raised to the predetermined power with a DC reference and subtracting the squared waveform therefrom, with all waveforms properly scaled. The resultant waveform is then multiplied with a square wave in order to correct the polarity and produce the resultant cosine waveform.

Characteristics of atmospheric gravity waves observed using the MU (Middle and Upper atmosphere) radar and GPS (Global Positioning System) radio occultation.

PubMed

Tsuda, Toshitaka

2014-01-01

The wind velocity and temperature profiles observed in the middle atmosphere (altitude: 10-100 km) show perturbations resulting from superposition of various atmospheric waves, including atmospheric gravity waves. Atmospheric gravity waves are known to play an important role in determining the general circulation in the middle atmosphere by dynamical stresses caused by gravity wave breaking. In this paper, we summarize the characteristics of atmospheric gravity waves observed using the middle and upper atmosphere (MU) radar in Japan, as well as novel satellite data obtained from global positioning system radio occultation (GPS RO) measurements. In particular, we focus on the behavior of gravity waves in the mesosphere (50-90 km), where considerable gravity wave attenuation occurs. We also report on the global distribution of gravity wave activity in the stratosphere (10-50 km), highlighting various excitation mechanisms such as orographic effects, convection in the tropics, meteorological disturbances, the subtropical jet and the polar night jet.

Characteristics of atmospheric gravity waves observed using the MU (Middle and Upper atmosphere) radar and GPS (Global Positioning System) radio occultation

PubMed Central

TSUDA, Toshitaka

2014-01-01

The wind velocity and temperature profiles observed in the middle atmosphere (altitude: 10–100 km) show perturbations resulting from superposition of various atmospheric waves, including atmospheric gravity waves. Atmospheric gravity waves are known to play an important role in determining the general circulation in the middle atmosphere by dynamical stresses caused by gravity wave breaking. In this paper, we summarize the characteristics of atmospheric gravity waves observed using the middle and upper atmosphere (MU) radar in Japan, as well as novel satellite data obtained from global positioning system radio occultation (GPS RO) measurements. In particular, we focus on the behavior of gravity waves in the mesosphere (50–90 km), where considerable gravity wave attenuation occurs. We also report on the global distribution of gravity wave activity in the stratosphere (10–50 km), highlighting various excitation mechanisms such as orographic effects, convection in the tropics, meteorological disturbances, the subtropical jet and the polar night jet. PMID:24492645

Big Data Challenges for Large Radio Arrays

NASA Technical Reports Server (NTRS)

Jones, Dayton L.; Wagstaff, Kiri; Thompson, David; D'Addario, Larry; Navarro, Robert; Mattmann, Chris; Majid, Walid; Lazio, Joseph; Preston, Robert; Rebbapragada, Umaa

2012-01-01

Future large radio astronomy arrays, particularly the Square Kilometre Array (SKA), will be able to generate data at rates far higher than can be analyzed or stored affordably with current practices. This is, by definition, a "big data" problem, and requires an end-to-end solution if future radio arrays are to reach their full scientific potential. Similar data processing, transport, storage, and management challenges face next-generation facilities in many other fields.

Peering through Jupiter’s clouds with radio spectral imaging

NASA Astrophysics Data System (ADS)

de Pater, Imke; Sault, R. J.; Butler, Bryan; DeBoer, David; Wong, Michael H.

2016-06-01

Radio wavelengths can probe altitudes in Jupiter’s atmosphere below its visible cloud layers. We used the Very Large Array to map this unexplored region down to ~8 bar, ~100 kilometers below the visible clouds. Our maps reveal a dynamically active planet at pressures less than 2 to 3 bar. A radio-hot belt exists, consisting of relatively transparent regions (a low ammonia concentration, NH3 being the dominant source of opacity) probing depths to over ~8 bar; these regions probably coincide with 5-micrometer hot spots. Just to the south we distinguish an equatorial wave, bringing up ammonia gas from Jupiter’s deep atmosphere. This wave has been theorized to produce the 5-micrometer hot spots; we observed the predicted radio counterpart of such hot spots.

ASKAP Joins the Hunt for Mysterious Bursts

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-05-01

A new telescope, the Australian Square Kilometre Array Pathfinder (ASKAP), has joined the search for energetic and elusive fast radio bursts. And in just a few days of looking, its already had success!Elusive TransientsThe Parkes radio telescope, which has detected all but five of the fast radio bursts published to date, has a very narrow field of view. [CSIRO]Fast radio bursts are mysterious millisecond-duration radio pulses that were first discovered around a decade ago. Since that time particularly in recent years weve made some progress toward the goal of localizing them. Were now fairly convinced that fast radio bursts come from outside of the galaxy, and yet theyre enormously bright orders of magnitude more luminous than any pulse seen from the Milky Way.Better identification of where these mysterious bursts come from would help us to determine what they are. But so far, weve discovered only around 30 such bursts, despite the fact that theyre estimated to occur at a rate of 3,000 events per day across the whole sky.Why are they so hard to find? Due to their short duration, effective detection would require instantaneous coverage of a very large fraction of the sky. The Parkes radio telescope which has detected all but five of the fast radio bursts published to date has a field of view spanning less than a square degree,significantly limiting our ability to rapidly survey for these transients.FRB 170107s band-averaged pulse (top) and dynamic spectrum (bottom). [Bannister et al. 2017]A New Array in TownA new player is now on the scene, however, and its already had huge success. ASKAP is a wide-field radio telescope made up of an array of 12-meter antennas. Using phased-array-feed technology, ASKAP is able to instantaneously observe an effective area of 160 square degrees an enormous field compared to Parkes 0.6 square degrees! This capability significantly increases our chances of being able to detect fast radio bursts.In a new study led by Keith Bannister (Australia Telescope National Facility, CSIRO Astronomy and Space Science), a team of scientists presents results from ASKAPs first 3.4-day pilot survey. Bannister and collaborators announce that in this brief time, ASKAP has already detected a fast radio burst: FRB 170107, an especially luminous, 2 millisecond burst that confirms the presence of an ultra-bright population of fast radio bursts.Looking to the FutureLocalization of FRB 170107. [Adapted from Bannister et al. 2017]Using the multiple bands of ASKAP, the authors were able to constrain the position of FRB 170107 to a region just 8 x 8 in size. No known field galaxies exist in that region, so were still not sure exactly where it came from, but this localization is already a significant achievement.The discovery and characterization of a burst already after such a short initial campaign suggests that ASKAP will become a very powerful tool for detecting fast radio bursts including some of the rarest bursts, ultra-bright ones like FRB 170107. We finally appear to be poised to resolve some of the mysteries of this population of transients.CitationK. W. Bannister et al 2017 ApJL 841 L12. doi:10.3847/2041-8213/aa71ff

Architectural Considerations of Fiber-Radio Millimeter-Wave Wireless Access Systems

NASA Astrophysics Data System (ADS)

Kitayama, Ken-Ichi

The architecture of fiber-radio mm-wave wireless access systems critically depends upon the optical mm-wave generation and transport techniques. Four optical mm-wave generation and transport techniques: 1) optical self-heterodyning, 2) external modulation, 3) up- and downconversion, and 4) optical transceiver, will be assessed. From the technical viewpoints, their advantages and disadvantages are discussed. The economical assessment, focusing on the cost of a base station BS ( ), will suggest that the optical transceiver looks the most promising in the long run, but in the near future, however, the external modulation will be cost-effective. The experimental results of 60 GHz testbeds using the external modulation will support the conclusion.

Physics of the Geospace Response to Powerful HF Radio Waves

DTIC Science & Technology

2012-10-31

studies of the response of the Earth’s space plasma to high-power HF radio waves from the High-frequency Active Auroral Research Program ( HAARP ...of HF heating and explored to simulate artificial ducts. DMSP- HAARP experiments revealed that HF-created ion outflows and artificial density ducts...in the topside ionosphere appeared faster than predicted by the models, pointing to kinetic (suprathermal) effects. CHAMP/GRACE- HAARP experiments

Conversion of Radio-Frequency Pulses to Continuous-Wave Sinusoids by Fast Switching and Narrowband Filtering

DTIC Science & Technology

2016-09-01

Switching and Narrowband Filtering by Gregory J Mazzaro, Andrew J Sherbondy, Kenneth I Ranney, and Kelly D Sherbondy...Switching and Narrowband Filtering by Gregory J Mazzaro, Andrew J Sherbondy, Kenneth I Ranney, and Kelly D Sherbondy Sensors and Electron Devices...08/2016 4. TITLE AND SUBTITLE Conversion of Radio-Frequency Pulses to Continuous-Wave Sinusoids by Fast Switching and Narrowband Filtering 5a

Application of the nudged elastic band method to the point-to-point radio wave ray tracing in IRI modeled ionosphere

NASA Astrophysics Data System (ADS)

Nosikov, I. A.; Klimenko, M. V.; Bessarab, P. F.; Zhbankov, G. A.

2017-07-01

Point-to-point ray tracing is an important problem in many fields of science. While direct variational methods where some trajectory is transformed to an optimal one are routinely used in calculations of pathways of seismic waves, chemical reactions, diffusion processes, etc., this approach is not widely known in ionospheric point-to-point ray tracing. We apply the Nudged Elastic Band (NEB) method to a radio wave propagation problem. In the NEB method, a chain of points which gives a discrete representation of the radio wave ray is adjusted iteratively to an optimal configuration satisfying the Fermat's principle, while the endpoints of the trajectory are kept fixed according to the boundary conditions. Transverse displacements define the radio ray trajectory, while springs between the points control their distribution along the ray. The method is applied to a study of point-to-point ionospheric ray tracing, where the propagation medium is obtained with the International Reference Ionosphere model taking into account traveling ionospheric disturbances. A 2-dimensional representation of the optical path functional is developed and used to gain insight into the fundamental difference between high and low rays. We conclude that high and low rays are minima and saddle points of the optical path functional, respectively.

Color Composite Image of the Supernova Remnant

NASA Technical Reports Server (NTRS)

2000-01-01

This image is a color composite of the supernova remnant E0102-72: x-ray (blue), optical (green), and radio (red). E0102-72 is the remnant of a star that exploded in a nearby galaxy known as the Small Magellanic Cloud. The star exploded outward at speeds in excess of 20 million kilometers per hour (12 million mph) and collided with surrounding gas. This collision produced two shock waves, or cosmic sonic booms, one traveling outward, and the other rebounding back into the material ejected by the explosion. The radio image, shown in red, was made using the Australia Telescope Compact Array. The radio waves are due to extremely high-energy electrons spiraling around magnetic field lines in the gas and trace the outward moving shock wave. The Chandra X-ray Observatory image, shown in blue, shows gas that has been heated to millions of degrees by the rebounding, or reverse shock wave. The x-ray data show that this gas is rich in oxygen and neon. These elements were created by nuclear reactions inside the star and hurled into space by the supernova. The Hubble Space Telescope optical image, shown in green, shows dense clumps of oxygen gas that have 'cooled' to about 30,000 degrees. Photo Credit: X-ray (NASA/CXC/SAO); optical (NASA/HST): radio: (ACTA)

History of Chandra X-Ray Observatory

NASA Image and Video Library

2000-11-01

This image is a color composite of the supernova remnant E0102-72: x-ray (blue), optical (green), and radio (red). E0102-72 is the remnant of a star that exploded in a nearby galaxy known as the Small Magellanic Cloud. The star exploded outward at speeds in excess of 20 million kilometers per hour (12 million mph) and collided with surrounding gas. This collision produced two shock waves, or cosmic sonic booms, one traveling outward, and the other rebounding back into the material ejected by the explosion. The radio image, shown in red, was made using the Australia Telescope Compact Array. The radio waves are due to extremely high-energy electrons spiraling around magnetic field lines in the gas and trace the outward moving shock wave. The Chandra X-ray Observatory image, shown in blue, shows gas that has been heated to millions of degrees by the rebounding, or reverse shock wave. The x-ray data show that this gas is rich in oxygen and neon. These elements were created by nuclear reactions inside the star and hurled into space by the supernova. The Hubble Space Telescope optical image, shown in green, shows dense clumps of oxygen gas that have "cooled" to about 30,000 degrees. Photo Credit: X-ray (NASA/CXC/SAO); optical (NASA/HST): radio: (ACTA)

Low frequency ac waveform generator

DOEpatents

Bilharz, O.W.

1983-11-22

Low frequency sine, cosine, triangle and square waves are synthesized in circuitry which allows variation in the waveform amplitude and frequency while exhibiting good stability and without requiring significant stablization time. A triangle waveform is formed by a ramped integration process controlled by a saturation amplifier circuit which produces the necessary hysteresis for the triangle waveform. The output of the saturation circuit is tapped to produce the square waveform. The sine waveform is synthesized by taking the absolute value of the triangular waveform, raising this absolute value to a predetermined power, multiplying the raised absolute value of the triangle wave with the triangle wave itself and properly scaling the resultant waveform and subtracting it from the triangular waveform to a predetermined power and adding the squared waveform raised to the predetermined power with a DC reference and subtracting the squared waveform therefrom, with all waveforms properly scaled. The resultant waveform is then multiplied with a square wave in order to correct the polarity and produce the resultant cosine waveform.

47 CFR 32.2231 - Radio systems.

Code of Federal Regulations, 2010 CFR

2010-10-01

... costs. This account shall also include the original cost of earth stations and spare parts, material or..., amplification, propagation, reception, modulation, and demodulation of radio waves in free space over which...

PNNL Expert Doug McMakin Discusses Millimeter Wave Technology

ScienceCinema

McMakin, Doug

2018-02-13

Electrical Engineer Doug McMakin discusses Millimeter Wave Holographic technology, which uses non-harmful, ultrahigh-frequency radio waves to penetrate clothing to detect and identify concealed objects, as well as obtain accurate body measurements.

Using IRI and GSM TIP model results as environment for HF radio wave propagation model during the geomagnetic storm occurred on September 26-29, 2011

NASA Astrophysics Data System (ADS)

Kotova, D. S.; Klimenko, M. V.; Klimenko, V. V.; Zakharov, V. E.; Ratovsky, K. G.; Nosikov, I. A.; Zhao, B.

2015-11-01

This paper analyses the geomagnetic storm on September 26-29, 2011. We compare the calculation results obtained using the Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere (GSM TIP) and IRI-2012 (Bilitza et al., 2014) model with ground-based ionosonde data of stations at different latitudes and longitudes. We examined physical mechanisms responsible for the formation of ionospheric effects during the main phase of geomagnetic storm that occurred at the rising phase of the 24th solar cycle. We used numerical results obtained from IRI-2012 and GSM TIP models as propagation environment for HF signals from an equatorial transmitter during quiet and disturbed conditions. We used the model of HF radio wave propagation developed in I. Kant Baltic Federal University (BFU) that is based on the geometrical optics approximation. We compared the obtained radio paths in quiet conditions and during the main and recovery storm phases and evaluated radio wave attenuation in different media models.

Interplanetary Radio Transmission Through Serial Ionospheric and Material Barriers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fields, David; Kennedy, Robert G; Roy, Kenneth I

2013-01-01

A usual first principle in planning radio astronomy observations from the earth is that monitoring must be carried out well above the ionospheric plasma cutoff frequency (~5 MHz). Before space probes existed, radio astronomy was almost entirely done above 6 MHz, and this value is considered a practical lower limit by most radio astronomers. Furthermore, daytime ionization (especially D-layer formation) places additional constraints on wave propagation, and waves of frequency below 10-20 MHz suffer significant attenuation. More careful calculations of wave propagation through the earth s ionosphere suggest that for certain conditions (primarily the presence of a magnetic field) theremore » may be a transmission window well below this assumed limit. Indeed, for receiving extraterrestrial radiation below the ionospheric plasma cutoff frequency, a choice of VLF frequency appears optimal to minimize loss. The calculation, experimental validation, and conclusions are presented here. This work demonstrates the possibility of VLF transmission through the ionosphere and various subsequent material barriers. Implications include development of a new robust communications channel, communications with submerged or subterranean receivers / instruments on or offworld, and a new approach to SETI.« less

The Least Mean Squares Adaptive FIR Filter for Narrow-Band RFI Suppression in Radio Detection of Cosmic Rays

NASA Astrophysics Data System (ADS)

Szadkowski, Zbigniew; Głas, Dariusz

2017-06-01

Radio emission from the extensive air showers (EASs), initiated by ultrahigh-energy cosmic rays, was theoretically suggested over 50 years ago. However, due to technical limitations, successful collection of sufficient statistics can take several years. Nowadays, this detection technique is used in many experiments consisting in studying EAS. One of them is the Auger Engineering Radio Array (AERA), located within the Pierre Auger Observatory. AERA focuses on the radio emission, generated by the electromagnetic part of the shower, mainly in geomagnetic and charge excess processes. The frequency band observed by AERA radio stations is 30-80 MHz. Thus, the frequency range is contaminated by human-made and narrow-band radio frequency interferences (RFIs). Suppression of contaminations is very important to lower the rate of spurious triggers. There are two kinds of digital filters used in AERA radio stations to suppress these contaminations: the fast Fourier transform median filter and four narrow-band IIR-notch filters. Both filters have worked successfully in the field for many years. An adaptive filter based on a least mean squares (LMS) algorithm is a relatively simple finite impulse response (FIR) filter, which can be an alternative for currently used filters. Simulations in MATLAB are very promising and show that the LMS filter can be very efficient in suppressing RFI and only slightly distorts radio signals. The LMS algorithm was implemented into a Cyclone V field programmable gate array for testing the stability, RFI suppression efficiency, and adaptation time to new conditions. First results show that the FIR filter based on the LMS algorithm can be successfully implemented and used in real AERA radio stations.

Square-Wave Ocular Oscillation and Ataxia in an Anti-GAD-Positive Individual With Hypothyroidism.

PubMed

Brokalaki, Chrysoula; Kararizou, Evangelia; Dimitrakopoulos, Antonis; Evdokimidis, Ioannis; Anagnostou, Evangelos

2015-12-01

Cerebellar ataxia is an uncommon manifestation of hypothyroidism with unknown pathomechanism. The few descriptions of the clinical phenotype range from limb, gait, and trunk ataxia to various ocular motor abnormalities. We evaluated a 62-year-old woman with previously undetected severe hypothyroidism who presented with prominent saccadic intrusions and gait ataxia. She had high titers of antithyroid autoantibodies and anti-glutamic acid decarboxylase (anti-GAD) antibodies. Horizontal eye movement recordings revealed a series of nearly continuous pseudoharmonic square wave jerks (SWJs) constituting a square wave oscillation. Amplitudes reached maximum values of about 4, and wave frequency approached 100 cycles per minute. Thyroxine substitution and corticosteroid administration had little effect on SWJ parameters. The square wave oscillation nearly completely resolved after a single treatment session with intravenous immunoglobulin suggesting a causal link between an autoimmune process and the cerebellar dysfunction. Current concepts of the genesis of saccadic intrusions favor a role for anti-GAD antibodies in the etiology of SWJs.

Potentials of acousto-optical spectrum analysis on a basis of a novel algorithm of the collinear wave heterodyning in a large-aperture KRS-5 crystalline cell

NASA Astrophysics Data System (ADS)

Shcherbakov, Alexandre S.; Maximov, Jewgenij; Bliznetsov, Alexej M.; Sanchez Perez, Karla J.

2011-03-01

The technique under proposal for a precise spectrum analysis within an algorithm of the collinear wave heterodyning implies a two-stage integrated processing, namely, the wave heterodyning of a signal in a square-law nonlinear medium and then the optical processing in the same solid state cell. The technical advantage of this approach lies in providing a direct multichannel parallel processing of ultra-high-frequency radio-wave signals with essentially improved frequency resolution. This technique imposes specific requirements on the cell's material. We focus our attention on the solid solutions of thallium chalcogenides and take the TlBr-TlI (thallium bromine-thallium iodine) solution, which forms KRS-5 cubic-symmetry crystals with the mass-ratio 58% of TlBr to 42% of TlI. Analysis shows that the acousto-optical cell made of a KRS-5 crystal oriented along the [111]-axis and the corresponding longitudinal elastic mode for producing the dynamic diffractive grating can be exploited. With the acoustic velocity of about 1.92 × 105 cm/s and attenuation of ~10 dB/(cm GHz2), a similar cell is capable of providing an optical aperture of ~5.0 cm and one of the highest figures of acousto-optical merit in solid states in the visible range. Such a cell is rather desirable for the application to direct 5000-channel parallel spectrum analysis with an improved up to 10-5 relative frequency resolution.

Continuum radiation in planetary magnetospheres

NASA Technical Reports Server (NTRS)

Kurth, W. S.

1991-01-01

With the completion of the Voyager tour of the outer planets, radio and plasma wave instruments have executed the first survey of the wave spectra of Earth, Jupiter, Saturn, Uranus, and Neptune. One of the most notable conclusions of this survey is that there is a great deal of qualitative similarity in both the plasma wave and radio wave spectra from one magnetosphere to the next. In particular, in spite of detailed differences, most of the radio emissions at each of the planets have been tentatively classified into two primary categories. First, the most intense emissions are generally associated with the cyclotron maser instability. Second, a class of weaker emissions can be found at each of the magnetospheres which appears to be the result of conversion from intense electrostatic emissions at the upper hybrid resonance frequency into (primarily) ordinary mode radio emission. It is this second category, often referred to as nonthermal continuum radiation, which we will discuss in this review. We review the characteristics of the continuum spectrum at each of the planets, discuss the source region and direct observations of the generation of the emissions where available, and briefly describe the theories for the generation of the emissions. Over the past few years evidence has increased that the linear mode conversion of electrostatic waves into the ordinary mode can account for at least some of the continuum radiation observed. There is no definitive evidence which precludes the possibility that a nonlinear mechanism may also be important.

Mean-square angle-of-arrival difference between two counter-propagating spherical waves in the presence of atmospheric turbulence.

PubMed

Chen, Chunyi; Yang, Huamin; Tong, Shoufeng; Lou, Yan

2015-09-21

The mean-square angle-of-arrival (AOA) difference between two counter-propagating spherical waves in atmospheric turbulence is theoretically formulated. Closed-form expressions for the path weighting functions are obtained. It is found that the diffraction and refraction effects of turbulent cells make negative and positive contributions to the mean-square AOA difference, respectively, and the turbulent cells located at the midpoint of the propagation path have no contributions to the mean-square AOA difference. If the mean-square AOA difference is separated into the refraction and diffraction parts, the refraction part always dominates the diffraction one, and the ratio of the diffraction part to the refraction one is never larger than 0.5 for any turbulence spectrum. Based on the expressions for the mean-square AOA difference, formulae for the correlation coefficient between the angles of arrival of two counter-propagating spherical waves in atmospheric turbulence are derived. Numerical calculations are carried out by considering that the turbulence spectrum has no path dependence. It is shown that the mean-square AOA difference always approximates to the variance of AOA fluctuations. It is found that the correlation coefficient between the angles of arrival in the x or y direction of two counter-propagating spherical waves ranges from 0.46 to 0.5, implying that the instantaneous angles of arrival of two counter-propagating spherical waves in atmospheric turbulence are far from being perfectly correlated even when the turbulence spectrum does not vary along the path.

Past and future of radio occultation studies of planetary atmospheres

NASA Technical Reports Server (NTRS)

Eshleman, Von R.; Hinson, David P.; Tyler, G. Leonard; Lindal, Gunnar F.

1987-01-01

Measurements of radio waves that have propagated through planetary atmospheres have provided exploratory results on atmospheric constituents, structure, dynamics, and ionization for Venus, Mars, Titan, Jupiter, Saturn, and Uranus. Highlights of past results are reviewed in order to define and illustrate the potential of occultation and related radio studies in future planetary missions.

Need a Classroom Stimulus? Introduce Radio Astronomy

ERIC Educational Resources Information Center

Derman, Samuel

2010-01-01

Silently, invisibly, ceaselessly, our planet Earth is showered by radio waves from every direction and from every region of space. This radio energy originates in our solar system, throughout the Milky Way galaxy, and far beyond, out to the remotest reaches of the universe. Detecting and unraveling the origins of these invisible signals is what…

A review of tropospheric refraction effects on Earth-to-satellite systems

NASA Technical Reports Server (NTRS)

Althsuler, E. E.

1983-01-01

Abnormal refractivity gradients may cause radio waves to be trapped within tropospheric layers, thus producing regions through which the waves do not pass called radio holes. For some locations and for many applications, refractive corrections based on the surface refractivity are adequate for elevation angles above a few degrees. However, new systems which operate at elevation angles near the horizon often require improved accuracies. Techniques for obtaining these improved corrections are reviewed.

Types of propagation of radio waves of the decameter range, according to observations by the OBS method on Cuba--Soviet Union paths

DOE Office of Scientific and Technical Information (OSTI.GOV)

Berdeyans, D.; Bocharov, V.I.; Lobachevskii, L.A.

Ionosphere observations by the OBS method were performed to study ionospheric conditions under which radio waves in the decameter range propagate on Cuba--Soviet Union paths. The results of observations in the summer of 1973 are reported. The distance--frequency and distance--time characteristics of back-scattered signals in the sounding direction for each day of observation are discussed. (JFP)

A study of electron density profiles in relation to ionization sources and ground-based radio wave absorption measurements, part 2

NASA Technical Reports Server (NTRS)

Gnanalingam, S.; Kane, J. A.

1975-01-01

The D-region ion production functions are used to calculate the relationship between radio wave absorption and the flux level of X-rays in the 1-8A wavelength band. In order to bring this calculation into agreement with the empirically established relationship, it was found necessary to reduce by, a factor of about 5, the Meira nitric oxide densities below 90 km.

THE ABUNDANCE OF X-SHAPED RADIO SOURCES: IMPLICATIONS FOR THE GRAVITATIONAL WAVE BACKGROUND

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roberts, David H.; Saripalli, Lakshmi; Subrahmanyan, Ravi, E-mail: roberts@brandeis.edu

Coalescence of supermassive black holes (SMBHs) in galaxy mergers is potentially the dominant contributor to the low frequency gravitational wave background (GWB). It was proposed by Merritt and Ekers that X-shaped radio galaxies are signposts of such coalescences and that their abundance might be used to predict the magnitude of the GWB. In Roberts et al. we presented radio images of all 52 X-shaped radio source candidates out of the sample of 100 selected by Cheung for which archival VLA data were available. These images indicate that at most 21% of the candidates might be genuine X-shaped radio sources thatmore » were formed by a restarting of beams in a new direction following a major merger. This suggests that fewer than 1.3% of extended radio sources appear to be candidates for genuine axis reorientations (“spin flips”), much smaller than the 7% suggested by Leahy and Parma. Thus, the associated GWB may be substantially smaller than previous estimates. These results can be used to normalize detailed calculations of the SMBH coalescence rate and the GWB.« less

Air shower measurements with the LOPES radio antenna array

NASA Astrophysics Data System (ADS)

Lopes Collaboration; Haungs, A.; Apel, W. D.; Arteaga, J. C.; Asch, T.; Auffenberg, J.; Badea, F.; Bähren, L.; Bekk, K.; Bertaina, M.; Biermann, P. L.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Brüggemann, M.; Buchholz, P.; Buitink, S.; Cantoni, E.; Chiavassa, A.; Cossavella, F.; Daumiller, K.; de Souza, V.; di Pierro, F.; Doll, P.; Engel, R.; Falcke, H.; Finger, M.; Fuhrmann, D.; Gemmeke, H.; Ghia, P. L.; Glasstetter, R.; Grupen, C.; Heck, D.; Hörandel, J. R.; Horneffer, A.; Huege, T.; Isar, P. G.; Kampert, K.-H.; Kang, D.; Kickelbick, D.; Kolotaev, Y.; Krömer, O.; Kuijpers, J.; Lafebre, S.; Łuczak, P.; Mathes, H. J.; Mayer, H. J.; Milke, J.; Mitrica, B.; Morello, C.; Navarra, G.; Nehls, S.; Nigl, A.; Oehlschläger, J.; Over, S.; Petcu, M.; Pierog, T.; Rautenberg, J.; Rebel, H.; Roth, M.; Saftoiu, A.; Schieler, H.; Schmidt, A.; Schröder, F.; Sima, O.; Singh, K.; Stümpert, M.; Toma, G.; Trinchero, G. C.; Ulrich, H.; Walkowiak, W.; Weindl, A.; Wochele, J.; Wommer, M.; Zabierowski, J.; Zensus, J. A.; LOPES Collaboration

2009-06-01

LOPES is set up at the location of the KASCADE-Grande extensive air shower experiment in Karlsruhe, Germany and aims to measure and investigate radio pulses from extensive air showers. Since radio waves suffer very little attenuation, radio measurements allow the detection of very distant or highly inclined showers. These waves can be recorded day and night, and provide a bolometric measure of the leptonic shower component. LOPES is designed as a digital radio interferometer using high bandwidths and fast data processing and profits from the reconstructed air shower observables of KASCADE-Grande. The LOPES antennas are absolutely amplitude calibrated allowing to reconstruct the electric field strength which can be compared with predictions from detailed Monte-Carlo simulations. We report about the analysis of correlations present in the radio signals measured by the LOPES 30 antenna array. Additionally, LOPES operates antennas of a different type (LOPESSTAR) which are optimized for an application at the Pierre Auger Observatory. Status, recent results of the data analysis and further perspectives of LOPES and the possible large scale application of this new detection technique are discussed.

High-speed millimeter communication through radio-over-free-space-optics network by mode-division multiplexing

NASA Astrophysics Data System (ADS)

Chaudhary, Sushank; Amphawan, Angela

2017-11-01

In an attempt to meet the goal of distributing millimeter-wave (mm-wave) signals, recent years have witnessed significant relevance being given to combining radio frequency with optical fiber technologies. The future of radio-over-free-space-optics technology aims to build a universal platform for distributing millimeter waves for wireless local area networks without using expensive optical fibers. This work is focused on simultaneous transmission of four independent OFDM-based channels, each carrying 20 Gbps to 40 GHz data, by mode-division multiplexing of Laguerre-Gaussian mode with vortex lens and Hermite-Gaussian mode to realize a total transmission of 80 Gbps to 160 GHz data over 50-km free-space optical link. Moreover, the performance of the proposed system is also evaluated under the influence of various atmospheric turbulences, such as light fog, thin fog, and thick fog.

Features of the Electromagnetic and Plasma Disturbances Induced at the Altitudes of the Earth's Outer Ionosphere by Modification of the Ionospheric F 2 Region Using High-Power Radio Waves Radiated by the SURA Heating Facility

NASA Astrophysics Data System (ADS)

Frolov, V. L.; Rapoport, V. O.; Schorokhova, E. A.; Belov, A. S.; Parrot, M.; Rauch, J.-L.

2016-08-01

In this paper we systematize the results of studying the characteristics of the plasma-density ducts, which was conducted in 2005-2010 during the DEMETER-satellite operation. The ducts are formed at altitudes of about 700 km as a result of the ionospheric F 2 region modification by high-power high-frequency radio waves radiated by the midlatitude SURA heating facility. All the performed measurements are used as the basis for determining the formation conditions for such ducts, the duct characteristics are studied, and the opportunities for the duct influence on the ionosphere-magnetosphere coupling and propagation of radio waves of various frequency ranges are demonstrated. The results of numerical simulation of the formation of such ducts are presented.

Amplitude and Phase Characteristics of Signals at the Output of Spatially Separated Antennas for Paths with Scattering

NASA Astrophysics Data System (ADS)

Anikin, A. S.

2018-06-01

Conditional statistical characteristics of the phase difference are considered depending on the ratio of instantaneous output signal amplitudes of spatially separated weakly directional antennas for the normal field model for paths with radio-wave scattering. The dependences obtained are related to the physical processes on the radio-wave propagation path. The normal model parameters are established at which the statistical characteristics of the phase difference depend on the ratio of the instantaneous amplitudes and hence can be used to measure the phase difference. Using Shannon's formula, the amount of information on the phase difference of signals contained in the ratio of their amplitudes is calculated depending on the parameters of the normal field model. Approaches are suggested to reduce the shift of phase difference measured for paths with radio-wave scattering. A comparison with results of computer simulation by the Monte Carlo method is performed.

Current drive at plasma densities required for thermonuclear reactors.

PubMed

Cesario, R; Amicucci, L; Cardinali, A; Castaldo, C; Marinucci, M; Panaccione, L; Santini, F; Tudisco, O; Apicella, M L; Calabrò, G; Cianfarani, C; Frigione, D; Galli, A; Mazzitelli, G; Mazzotta, C; Pericoli, V; Schettini, G; Tuccillo, A A

2010-08-10

Progress in thermonuclear fusion energy research based on deuterium plasmas magnetically confined in toroidal tokamak devices requires the development of efficient current drive methods. Previous experiments have shown that plasma current can be driven effectively by externally launched radio frequency power coupled to lower hybrid plasma waves. However, at the high plasma densities required for fusion power plants, the coupled radio frequency power does not penetrate into the plasma core, possibly because of strong wave interactions with the plasma edge. Here we show experiments performed on FTU (Frascati Tokamak Upgrade) based on theoretical predictions that nonlinear interactions diminish when the peripheral plasma electron temperature is high, allowing significant wave penetration at high density. The results show that the coupled radio frequency power can penetrate into high-density plasmas due to weaker plasma edge effects, thus extending the effective range of lower hybrid current drive towards the domain relevant for fusion reactors.

Interplanetary particle beams

NASA Technical Reports Server (NTRS)

Dulk, G. A.

1990-01-01

This paper reviews observations of interplanetary particle beams of the kind that frequently accompany a solar flare. It is shown that the most frequently observed beams are beams of electrons which are associated with radio bursts of type III, but occasionally with flares and X-ray bursts. Although the main features of these beams and their associated plasma waves and radio bursts are known, uncertainties remain in terms of the correlation between electron beams and filamentary structures, the relative importance of the quasi-linear and the nonlinear wave emissions as the dominant process, and the mechanism of conversion of some of the Langmuir wave energy into radio emissions. Other particle beams discussed are those composed of protons, neutrons, He ions, or heavy ions. While most of these beams originate from sun flares, the source of some of particle beams may be the earth, Jupiter, or other planets as well as comets.

Gas Clouds in Whirlpool Galaxy Yield Important Clues Supporting Theory on Spiral Arms

NASA Astrophysics Data System (ADS)

2004-06-01

Astronomers studying gas clouds in the famous Whirlpool Galaxy have found important clues supporting a theory that seeks to explain how the spectacular spiral arms of galaxies can persist for billions of years. The astronomers applied techniques used to study similar gas clouds in our own Milky Way to those in the spiral arms of a neighbor galaxy for the first time, and their results bolster a theory first proposed in 1964. M51 The spiral galaxy M51: Left, as seen with the Hubble Space Telescope; Right, radio image showing location of Carbon Monoxide gas. CREDIT: STScI, OVRO, IRAM (Click on image for larger version) Image Files Optical and Radio (CO) Views (above image) HST Optical Image with CO Contours Overlaid Radio/Optical Composite Image of M51 VLA/Effelsberg Radio Image of M51, With Panel Showing Magnetic Field Lines The Whirlpool Galaxy, about 31 million light-years distant, is a beautiful spiral in the constellation Canes Venatici. Also known as M51, it is seen nearly face-on from Earth and is familiar to amateur astronomers and has been featured in countless posters, books and magazine articles. "This galaxy made a great target for our study of spiral arms and how star formation works along them," said Eva Schinnerer, of the National Radio Astronomy Observatory in Socorro, NM. "It was ideal for us because it's one of the closest face-on spirals in the sky," she added. Schinnerer worked with Axel Weiss of the Institute for Millimeter Radio Astronomy (IRAM) in Spain, Susanne Aalto of the Onsala Space Observatory in Sweden, and Nick Scoville of Caltech. The astronomers presented their findings to the American Astronomical Society's meeting in Denver, Colorado. The scientists analyzed radio emission from Carbon Monoxide (CO) molecules in giant gas clouds along M51's spiral arms. Using telescopes at Caltech's Owens Valley Radio Observatory and the 30-meter radio telescope of IRAM, they were able to determine the temperatures and amounts of turbulence within the clouds. Their results provide strong support for a theory that "density waves" explain how spiral arms can persist in a galaxy without winding themselves so tightly that, in effect, they disappear. The density-wave theory, proposed by Frank Shu and C.C. Lin in 1964, says that a galaxy's spiral pattern is a wave of higher density, or compression, that revolves around the galaxy at a speed different from that of the galaxy's gas and stars. Schinnerer and her colleagues studied a region in one of M51's spiral arms that presumably has just overtaken and passed through the density wave. Their data indicate that gas on the trailing edge of the spiral arm, which has most recently passed through the density wave, is both warmer and more turbulent than gas in the forward edge of the arm, which would have passed through the density wave longer ago. "This is what we would expect from the density-wave theory," Schinnerer said. "The gas that passed through the density wave earlier has had time to cool and lose the turbulence caused by the passage," she added. "Our results show, for the first time, how the density wave operates on a cloud-cloud scale, and how it promotes and prevents star formation in spiral arms," Aalto said. The next step, the scientists say, is to look at other spiral galaxies to see if a similar pattern is present. That will have to wait, Schinnerer said, because the radio emission from CO molecules that provides the information on temperature and turbulence is very faint. "When the Atacama Large Millimeter Array (ALMA) comes on line, it will have the ability to extend this type of study to other galaxies. We look forward to using ALMA to test the density-wave model more thoroughly," Schinnerer said. ALMA is a millimeter-wave observatory that will use 64, 12-meter-diameter dish antennas on the Atacama Desert of northern Chile. Now under construction, ALMA will provide astronomers with an unprecedented capability to study the Universe at millimeter wavelengths. The Whirlpool Galaxy was discovered by the French comet-hunter Charles Messier on October 13, 1773. He included it as object number 51 in his now-famous catalog of astronomical objects that, in a small telescope, might be mistaken for a comet. In 1845, the British astronomer Lord Rosse discovered the spiral structure in the galaxy. For amateur astronomers using telescopes in dark-sky locations, M51 is a showpiece object. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Brown Dwarfs: A New Class of Stellar Lighthouse

NASA Astrophysics Data System (ADS)

2007-04-01

Brown dwarfs, thought just a few years ago to be incapable of emitting any significant amounts of radio waves, have been discovered putting out extremely bright "lighthouse beams" of radio waves, much like pulsars. A team of astronomers made the discovery using the National Science Foundation's Very Large Array (VLA) radio telescope. Artist's Conception of Brown Dwarf Artist's conception of "mini-aurorae" at poles of brown dwarf, producing beams of strong radio emission. CREDIT: Hallinan et al., NRAO/AUI/NSF Click on image for page of graphics and full information "These beams rotate with the brown dwarf, and we see them when the beam passes over the Earth. This is the same way we see pulses from pulsars," said Gregg Hallinan of the National University of Ireland Galway. "We now think brown dwarfs may be a missing link between pulsars and planets in our own Solar System, which also emit, but more weakly," he added. Brown dwarfs are enigmatic objects that are too small to be stars but too large to be planets. They are sometimes called "failed stars" because they have too little mass to trigger hydrogen fusion reactions at their cores, the source of the energy output in larger stars. With roughly 15 to 80 times the mass of Jupiter, the largest planet in our Solar System, brown dwarfs were long thought to exist. However, it was not until 1995 that astronomers were able to actually find one. A few dozen now are known. In 2001, a group of summer students at the National Radio Astronomy Observatory used the VLA to observe a brown dwarf, even though they had been told by seasoned astronomers that brown dwarfs are not observable at radio wavelengths. Their discovery of a strong flare of radio emission from the object surprised astronomers and the students' scientific paper on the discovery was published in the prestigous scientific journal Nature. Hallinan and his team observed a set of brown dwarfs with the VLA last year, and found that three of the objects emit extremely strong, repeating pulses of radio waves. They concluded that the pulses come from beams emitted from the magnetic poles of the brown dwarfs. This is similar to the beamed emission from pulsars, which are superdense neutron stars, and much more massive than brown dwarfs. The characteristics of the beamed radio emission from the brown dwarfs suggest to the scientists that it is produced by a mechanism also seen at work in planets, including Jupiter and Earth. This process involves electrons interacting with the planet's magnetic field to produce radio waves that then are amplified, or strengthened, by natural masers that amplify radio waves the same way a laser amplifies light waves. "The brown dwarfs we observed are between planets and pulsars in the strength of their radio emissions," said Aaron Golden, also of the National University of Ireland Galway. "While we don't think the mechanism that's producing the radio waves in brown dwarfs is exactly the same as that producing pulsar radio emissions, we think there may be enough similarities that further study of brown dwarfs may help unlock some of the mysteries about how pulsars work," he said. While pulsars were discovered 40 years ago, scientists still do not understand the details of how their strong radio emissions are produced. The brown dwarfs rotate at a much more leisurely pace than pulsars. While pulsars rotate -- and produce observed pulses -- typically several times a second to hundreds of times a second, the brown dwarfs observed with the VLA are showing pulses roughly once every two to three hours. Hallinan and Golden worked with Stephen Bourke and Caoilfhionn Lane, also of the National University of Ireland Galway; Tony Antonova and Gerry Doyle of Armagh Observatory in Northern Ireland; Robert Zavala and Fred Vrba of the U.S.Naval Observatory in Flagstaff, Arizona; Walter Brisken of the National Radio Astronomy Observatory in Socorro, New Mexico; and Richard Boyle of the Vatican Observatory Research Group at Steward Observatory in Arizona. The scientists presented their results to the Royal Astronomical Society's National Astronomy Meeting at the University of Central Lancashire in the United Kingdom. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc. This work was supported by Science Foundation Ireland under its Research Frontiers Programme, the Higher Education Authority's Programme for Research in Third Level Institutions, and the Irish Research Council for Science, Engineering and Technology.

Radio Counterparts of Compact Binary Mergers Detectable in Gravitational Waves: A Simulation for an Optimized Survey

NASA Astrophysics Data System (ADS)

Hotokezaka, K.; Nissanke, S.; Hallinan, G.; Lazio, T. J. W.; Nakar, E.; Piran, T.

2016-11-01

Mergers of binary neutron stars and black hole-neutron star binaries produce gravitational-wave (GW) emission and outflows with significant kinetic energies. These outflows result in radio emissions through synchrotron radiation. We explore the detectability of these synchrotron-generated radio signals by follow-up observations of GW merger events lacking a detection of electromagnetic counterparts in other wavelengths. We model radio light curves arising from (I) sub-relativistic merger ejecta and (II) ultra-relativistic jets. The former produce radio remnants on timescales of a few years and the latter produce γ-ray bursts in the direction of the jet and orphan-radio afterglows extending over wider angles on timescales of weeks. Based on the derived light curves, we suggest an optimized survey at 1.4 GHz with five epochs separated by a logarithmic time interval. We estimate the detectability of the radio counterparts of simulated GW-merger events to be detected by advanced LIGO and Virgo by current and future radio facilities. The detectable distances for these GW merger events could be as high as 1 Gpc. Around 20%-60% of the long-lasting radio remnants will be detectable in the case of the moderate kinetic energy of 3\\cdot {10}50 erg and a circum-merger density of 0.1 {{cm}}-3 or larger, while 5%-20% of the orphan-radio afterglows with kinetic energy of 1048 erg will be detectable. The detection likelihood increases if one focuses on the well-localizable GW events. We discuss the background noise due to radio fluxes of host galaxies and false positives arising from extragalactic radio transients and variable active galactic nuclei, and we show that the quiet radio transient sky is of great advantage when searching for the radio counterparts.

A theory for narrow-banded radio bursts at Uranus - MHD surface waves as an energy driver

NASA Technical Reports Server (NTRS)

Farrell, W. M.; Curtis, S. A.; Desch, M. D.; Lepping, R. P.

1992-01-01

A possible scenario for the generation of the narrow-banded radio bursts detected at Uranus by the Voyager 2 planetary radio astronomy experiment is described. In order to account for the emission burstiness which occurs on time scales of hundreds of milliseconds, it is proposed that ULF magnetic surface turbulence generated at the frontside magnetopause propagates down the open/closed field line boundary and mode-converts to kinetic Alfven waves (KAW) deep within the polar cusp. The oscillating KAW potentials then drive a transient electron stream that creates the bursty radio emission. To substantiate these ideas, Voyager 2 magnetometer measurements of enhanced ULF magnetic activity at the frontside magnetopause are shown. It is demonstrated analytically that such magnetic turbulence should mode-convert deep in the cusp at a radial distance of 3 RU.

3.6 cm signal attenuation in Venus' lower and middle atmosphere observed by the Radio Science experiment VeRa onboard Venus Express

NASA Astrophysics Data System (ADS)

Oschlisniok, J.; Tellmann, S.; Pätzold, M.; Häusler, B.; Andert, T.; Bird, M.; Remus, S.

2012-09-01

The planet Venus is shrouded within a roughly 20 km thick cloud layer, which extends from the lower to the middle atmosphere (ca. 50 - 70 km). While the clouds are mostly composed of sulfuric acid droplets, a haze layer of sulfuric acid vapor exists below the clouds. Within the cloud and the sub - cloud region Radio signal strength variations (intensity scintillations) caused by atmospheric waves and a decrease in the signal intensity caused by absorption by H2SO4 are observed by radio occultation experiments. The Venus Express spacecraft is orbiting Venus since 2006. The Radio Science Experiment VeRa probes the atmosphere with radio signals at 3.6 cm (XBand) and 13 cm (S-Band) wavelengths. The disturbance of the radio signal intensity is used to investigate the cloud region with respect to atmospheric waves. The absorption of the signal is used to determine the abundance of H2SO4 near the cloud base. This way a detailed study of the H2SO4 abundance within the cloud and sub - cloud region is possible. Results from the intensity scintillations within the cloud deck are presented and compared with gravity wave studies based on temperature variations inferred from VeRa soundings. Vertical absorptivity profiles and resulting sulfuric acid vapor profiles are presented and compared with previous missions. A distinct latitudinal dependence and a southern northern symmetry are clearly visible.

Radio emissions from pulsar companions: a refutable explanation for galactic transients and fast radio bursts

NASA Astrophysics Data System (ADS)

Mottez, F.; Zarka, P.

2014-09-01

Context. The six known highly dispersed fast radio bursts are attributed to extragalactic radio sources that are of unknown origin but extremely energetic. We propose here a new explanation that does not require an extreme release of energy and involves a body (planet, asteroid, white dwarf) orbiting an extragalactic pulsar. Aims: We investigate a theory of radio waves associated with such pulsar-orbiting bodies. We focus our analysis on the waves emitted from the magnetic wake of the body in the pulsar wind. After deriving their properties, we compare them with the observations of various transient radio signals to determine whether they could originate from pulsar-orbiting bodies. Methods: The analysis is based on the theory of Alfvén wings: for a body immersed in a pulsar wind, a system of two stationary Alfvén waves is attached to the body, provided that the wind is highly magnetised. When they are destabilised through plasma instabilities, Alfvén wings can be the locus of strong radio sources that are convected with the pulsar wind. By assuming a cyclotron maser instability operating in the Alfvén wings, we make predictions about the shape, frequencies, and brightness of the resulting radio emissions. Results: Because of the beaming by relativistic aberration, the signal is seen only when the companion is perfectly aligned between its parent pulsar and the observer, as is the case for occultations. For pulsar winds with a high Lorentz factor (≥104), the whole duration of the radio event does not exceed a few seconds, and it is composed of one to four peaks that last a few milliseconds each and are detectable up to distances of several Mpc. The Lorimer burst, the three isolated pulses of PSR J1928+15, and the recently detected fast radio bursts are all compatible with our model. According to it, these transient signals should repeat periodically with the companion's orbital period. Conclusions: The search of pulsar-orbiting bodies could be an exploration theme for new- or next-generation radio telescopes.

Phase-Sensitive Reflective Imaging Device in the mm-wave and Terahertz Regions

NASA Astrophysics Data System (ADS)

Gallerano, Gian Piero; Doria, Andrea; Germini, Marzia; Giovenale, Emilio; Messina, Giovanni; Spassovsky, Ivan P.

2009-12-01

Two Free Electron Laser sources have been developed at ENEA-Frascati for a variety of applications: A Compact Free Electron Laser (C-FEL) that provides coherent radiation in the frequency range between 90 and 150 GHz Gallerano et al. (Infrared Phys. and Techn. 40:161, 1999), and a second source, FEL-CATS, which utilizes a peculiar radio-frequency structure to generate coherent emission in the range 0.4 to 0.7 THz Doria et al. (Phys. Rev. Lett 93:264801, 2004). The high peak power of several kW in 15 to 50 ps pulses, makes these sources particularly suitable for the assessment of exposure limits in biological systems and for long range detection. In this paper we present a phase-sensitive reflective imaging device in the mm-wave and THz regions, which has proven to be a valuable tool in the biological Ramundo-Orlando et al. (Bioelectromagnetics 28:587-598, 2007), environmental Doria et al. (2005) and art conservation fields Gallerano et al. (2008). Different setups have been tested at different levels of spatial resolution to image objects from a few centimeter square to larger sizes. Images have been compared to identify and characterize the contrast mechanism.

New constraints on cosmic polarization rotation from B-mode polarization in the cosmic microwave background

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alighieri, Sperello di Serego; Ni, Wei-Tou; Pan, Wei-Ping, E-mail: sperello@arcetri.astro.it, E-mail: weitou@gmail.com, E-mail: d9722518@oz.nthu.edu.tw

2014-09-01

SPTpol, POLARBEAR, and BICEP2 have recently measured the cosmic microwave background (CMB) B-mode polarization in various sky regions of several tens of square degrees and obtained BB power spectra in the multipole range 20-3000, detecting the components due to gravitational lensing and to inflationary gravitational waves. We analyze jointly the results of these three experiments and propose modifications to their analyses of the spectra to include in the model, in addition to the gravitational lensing and the inflationary gravitational wave components, and also the effects induced by the cosmic polarization rotation (CPR), if it exists within current upper limits. Althoughmore » in principle our analysis would also lead to new constraints on CPR, in practice these can only be given on its fluctuations (δα{sup 2}), since constraints on its mean angle are inhibited by the derotation which is applied by current CMB polarization experiments, in order to cope with the insufficient calibration of the polarization angle. The combined data fits from all three experiments (with 29% CPR-SPTpol correlation, depending on the theoretical model) gives the constraint (δα{sup 2}){sup 1/2} < 27.3 mrad (1.°56), with r = 0.194 ± 0.033. These results show that the present data are consistent with no CPR detection and the constraint on CPR fluctuation is about 1.°5. This method of constraining the CPR is new, is complementary to previous tests, which use the radio and optical/UV polarization of radio galaxies and the CMB E-mode polarization, and adds a new constraint for the sky areas observed by SPTpol, POLARBEAR, and BICEP2.« less

Optimal threshold of error decision related to non-uniform phase distribution QAM signals generated from MZM based on OCS

NASA Astrophysics Data System (ADS)

Han, Xifeng; Zhou, Wen

2018-03-01

Optical vector radio-frequency (RF) signal generation based on optical carrier suppression (OCS) in one Mach-Zehnder modulator (MZM) can realize frequency-doubling. In order to match the phase or amplitude of the recovered quadrature amplitude modulation (QAM) signal, phase or amplitude pre-coding is necessary in the transmitter side. The detected QAM signals usually have one non-uniform phase distribution after square-law detection at the photodiode because of the imperfect characteristics of the optical and electrical devices. We propose to use optimal threshold of error decision for non-uniform phase contribution to reduce the bit error rate (BER). By employing this scheme, the BER of 16 Gbaud (32 Gbit/s) quadrature-phase-shift-keying (QPSK) millimeter wave signal at 36 GHz is improved from 1 × 10-3 to 1 × 10-4 at - 4 . 6 dBm input power into the photodiode.

Multi-messenger astronomy of gravitational-wave sources with flexible wide-area radio transient surveys

NASA Astrophysics Data System (ADS)

Kavic, Michael; Cregg C. Yancey, Brandon E. Bear, Bernadine Akukwe, Kevin Chen, Jayce Dowell, Jonathan D. Gough, Jonah Kanner, Kenneth Obenberger, Peter Shawhan, John H. Simonetti , Gregory B. Taylor , Jr-Wei Tsai

2016-01-01

We explore opportunities for multi-messenger astronomy using gravitational waves (GWs) and prompt, transient low-frequency radio emission to study highly energetic astrophysical events. We review the literature on possible sources of correlated emission of GWs and radio transients, highlighting proposed mechanisms that lead to a short-duration, high-flux radio pulse originating from the merger of two neutron stars or from a superconducting cosmic string cusp. We discuss the detection prospects for each of these mechanisms by low-frequency dipole array instruments such as LWA1, the Low Frequency Array and the Murchison Widefield Array. We find that a broad range of models may be tested by searching for radio pulses that, when de-dispersed, are temporally and spatially coincident with a LIGO/Virgo GW trigger within a ˜30 s time window and ˜200-500 deg(2) sky region. We consider various possible observing strategies and discuss their advantages and disadvantages. Uniquely, for low-frequency radio arrays, dispersion can delay the radio pulse until after low-latency GW data analysis has identified and reported an event candidate, enabling a prompt radio signal to be captured by a deliberately targeted beam. If neutron star mergers do have detectable prompt radio emissions, a coincident search with the GW detector network and low-frequency radio arrays could increase the LIGO/Virgo effective search volume by up to a factor of ˜2. For some models, we also map the parameter space that may be constrained by non-detections.

Multi-messenger Astronomy of Gravitational-wave Sources with Flexible Wide-area Radio Transient Surveys

NASA Astrophysics Data System (ADS)

Yancey, Cregg C.; Bear, Brandon E.; Akukwe, Bernadine; Chen, Kevin; Dowell, Jayce; Gough, Jonathan D.; Kanner, Jonah; Kavic, Michael; Obenberger, Kenneth; Shawhan, Peter; Simonetti, John H.; -Wei Tsai, Gregory B. Taylor, Jr.

2015-10-01

We explore opportunities for multi-messenger astronomy using gravitational waves (GWs) and prompt, transient low-frequency radio emission to study highly energetic astrophysical events. We review the literature on possible sources of correlated emission of GWs and radio transients, highlighting proposed mechanisms that lead to a short-duration, high-flux radio pulse originating from the merger of two neutron stars or from a superconducting cosmic string cusp. We discuss the detection prospects for each of these mechanisms by low-frequency dipole array instruments such as LWA1, the Low Frequency Array and the Murchison Widefield Array. We find that a broad range of models may be tested by searching for radio pulses that, when de-dispersed, are temporally and spatially coincident with a LIGO/Virgo GW trigger within a ˜30 s time window and ˜200-500 deg2 sky region. We consider various possible observing strategies and discuss their advantages and disadvantages. Uniquely, for low-frequency radio arrays, dispersion can delay the radio pulse until after low-latency GW data analysis has identified and reported an event candidate, enabling a prompt radio signal to be captured by a deliberately targeted beam. If neutron star mergers do have detectable prompt radio emissions, a coincident search with the GW detector network and low-frequency radio arrays could increase the LIGO/Virgo effective search volume by up to a factor of ˜2. For some models, we also map the parameter space that may be constrained by non-detections.

Pattern masking: the importance of remote spatial frequencies and their phase alignment.

PubMed

Huang, Pi-Chun; Maehara, Goro; May, Keith A; Hess, Robert F

2012-02-16

To assess the effects of spatial frequency and phase alignment of mask components in pattern masking, target threshold vs. mask contrast (TvC) functions for a sine-wave grating (S) target were measured for five types of mask: a sine-wave grating (S), a square-wave grating (Q), a missing fundamental square-wave grating (M), harmonic complexes consisting of phase-scrambled harmonics of a square wave (Qp), and harmonic complexes consisting of phase-scrambled harmonics of a missing fundamental square wave (Mp). Target and masks had the same fundamental frequency (0.46 cpd) and the target was added in phase with the fundamental frequency component of the mask. Under monocular viewing conditions, the strength of masking depends on phase relationships among mask spatial frequencies far removed from that of the target, at least 3 times the target frequency, only when there are common target and mask spatial frequencies. Under dichoptic viewing conditions, S and Q masks produced similar masking to each other and the phase-scrambled masks (Qp and Mp) produced less masking. The results suggest that pattern masking is spatial frequency broadband in nature and sensitive to the phase alignments of spatial components.

Modifying the ionosphere with intense radio waves.

PubMed

Utlaut, W F; Cohen, R

1971-10-15

The ionospheric modification experiments provide an opportunity to better understand the aeronomy of the natural ionosphere and also afford the control of a naturally occurring plasma, which will make possible further progress in plasma physics. The ionospheric modification by powerful radio waves is analogous to studies of laser and microwave heating of laboratory plasmas (20). " Anomalous" reflectivity effects similar to the observed ionospheric attenuation have already been noted in plasmas modulated by microwaves, and anomalous heating may have been observed in plasmas irradiated by lasers. Contacts have now been established between the workers in these diverse areas, which span a wide range of the electromagnetic spectrum. Perhaps ionospheric modification will also be a valuable technique in radio communications.

Second-Order Electromagnetic and Hydrodynamic Effects in High-Frequency Radio-Wave Scattering from the Sea

DTIC Science & Technology

1975-03-01

tions, are consistent with the available experimental data. ;;A4 - 4 -sc iii ~ C CONTENTS Page I. INTRODUCTION ................ o....... 1 A. Motivation ...the research presented here. A. Motivation Measurements at a single radio frequency [Tyler et al, 1973, 1974] have indicated that radar techniques can...where C is the wave phase velocity and 8 is the resonance angle (Fig. 24). Some motivation and justification for this assumption can be found in

Radio Waves and Curriculum Pathways: Jamaican "At Risk" Learners Construct Media

ERIC Educational Resources Information Center

Feraria, Paulette J.

2018-01-01

This paper explores radio play as an alternative space for learning language and literacy for Jamaican students labeled as 'at-risk' learners. Through the creation of a make-believe radio station in the classroom, students developed oral language skills as a necessary precursor for social literacy. They connected reading and writing activities and…

47 CFR Figure 2 to Subpart N of... - Typical Audio Wave

Code of Federal Regulations, 2011 CFR

2011-10-01

... 47 Telecommunication 1 2011-10-01 2011-10-01 false Typical Audio Wave 2 Figure 2 to Subpart N of Part 2 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL FREQUENCY ALLOCATIONS AND RADIO... Audio Wave EC03JN91.006 ...

Solar Phenomena Associated with "EIT Waves"

NASA Technical Reports Server (NTRS)

Biesecker, D. A.; Myers, D. C.; Thompson, B. J.; Hammer, D. M.; Vourlidas, A.

2002-01-01

In an effort to understand what an 'EIT wave' is and what its causes are, we have looked for correlations between the initiation of EIT waves and the occurrence of other solar phenomena. An EIT wave is a coronal disturbance, typically appearing as a diffuse brightening propagating across the Sun. A catalog of EIT waves, covering the period from 1997 March through 1998 June, was used in this study. For each EIT wave, the catalog gives the heliographic location and a rating for each wave, where the rating is determined by the reliability of the observations. Since EIT waves are transient, coronal phenomena, we have looked for correlations with other transient, coronal phenomena: X-ray flares, coronal mass ejections (CMEs), and metric type II radio bursts. An unambiguous correlation between EIT waves and CMEs has been found. The correlation of EIT waves with flares is significantly weaker, and EIT waves frequently are not accompanied by radio bursts. To search for trends in the data, proxies for each of these transient phenomena are examined. We also use the accumulated data to show the robustness of the catalog and to reveal biases that must be accounted for in this study.

Reconfigurable wave band structure of an artificial square ice

DOE PAGES

lacocca, Ezio; Gliga, Sebastian; Stamps, Robert L.; ...

2016-04-18

Artificial square ices are structures composed of magnetic nanoelements arranged on the sites of a twodimensional square lattice, such that there are four interacting magnetic elements at each vertex, leading to geometrical frustration. Using a semianalytical approach, we show that square ices exhibit a rich spin-wave band structure that is tunable both by external magnetic fields and the magnetization configuration of individual elements. Internal degrees of freedom can give rise to equilibrium states with bent magnetization at the element edges leading to characteristic excitations; in the presence of magnetostatic interactions these form separate bands analogous to impurity bands in semiconductors.more » Full-scale micromagnetic simulations corroborate our semianalytical approach. Our results show that artificial square ices can be viewed as reconfigurable and tunable magnonic crystals that can be used as metamaterials for spin-wave-based applications at the nanoscale.« less

Reconfigurable wave band structure of an artificial square ice

DOE Office of Scientific and Technical Information (OSTI.GOV)

lacocca, Ezio; Gliga, Sebastian; Stamps, Robert L.

Artificial square ices are structures composed of magnetic nanoelements arranged on the sites of a twodimensional square lattice, such that there are four interacting magnetic elements at each vertex, leading to geometrical frustration. Using a semianalytical approach, we show that square ices exhibit a rich spin-wave band structure that is tunable both by external magnetic fields and the magnetization configuration of individual elements. Internal degrees of freedom can give rise to equilibrium states with bent magnetization at the element edges leading to characteristic excitations; in the presence of magnetostatic interactions these form separate bands analogous to impurity bands in semiconductors.more » Full-scale micromagnetic simulations corroborate our semianalytical approach. Our results show that artificial square ices can be viewed as reconfigurable and tunable magnonic crystals that can be used as metamaterials for spin-wave-based applications at the nanoscale.« less

Square-Wave Model for a Pendulum with Oscillating Suspension

ERIC Educational Resources Information Center

Yorke, Ellen D.

1978-01-01

Demonstrates that if a sinusoidal oscillation of the point of support of a pendulum is approximated by a square wave, a matrix method may be used to discuss parametric resonance and the stability of the inverted pendulum. (Author/SL)

Research on spacecraft electrical power conversion

NASA Technical Reports Server (NTRS)

Wilson, T. G.

1974-01-01

The steady state characteristics and starting behavior of some widely used self-oscillating magnetically coupled square wave inverters were studied and the development of LC-tuned square wave inverters is reported. An analysis on high amplitude voltage spikes which occur in dc-to-square-wave parallel converters shows the importance of various circuit parameters for inverter design and for the suppression of spikes. A computerized simulation of an inductor energy storage dc-to-dc converter with closed loop regulators and of a preregulating current step-up converter are detailed. Work continued on the computer aided design of two-winding energy storage dc-to-dc converters.

Square wave voltammetry at the dropping mercury electrode: Experimental

USGS Publications Warehouse

Turner, J.A.; Christie, J.H.; Vukovic, M.; Osteryoung, R.A.

1977-01-01

Experimental verification of earlier theoretical work for square wave voltammetry at the dropping mercury electrode is given. Experiments using ferric oxalate and cadmium(II) in HCl confirm excellent agreement with theory. Experimental peak heights and peak widths are found to be within 2% of calculated results. An example of trace analysis using square wave voltammetry at the DME is presented. The technique is shown to have the same order of sensitivity as differential pulse polarography but is much faster to perform. A detection limit for cadmium in 0.1 M HCl for the system used here was 7 ?? 10-8 M.

Astronomers Win Protection for Key Part of Radio Spectrum

NASA Astrophysics Data System (ADS)

2000-06-01

Astronomers using the millimeter-wave region of the radio spectrum have won crucial protection for their science. Dedicated allocations for radio astronomy have been given final approval by the 2,500 delegates to the World Radiocommunication Conference (WRC-00), which recently concluded a month of deliberations in Istanbul, Turkey. Radio services can transmit in these parts of the spectrum as long as they don't hinder astronomers' attempts to catch faint signals from the cosmos. The new allocations represent the culmination of more than three years of cooperative planning by radio astronomers in many countries. Millimeter waves -- high-frequency radio waves -- have come of age as an astronomical tool in the last ten years. They are one of the last technological frontiers for astronomers. WRC-00 has protected for science all the frequencies between 71 and 275 Gigahertz (GHz) that radio astronomers currently use, adding more than 90 GHz of spectrum to the 44 GHz already set aside in this frequency range. As a result, radio astronomy is now allocated most of the frequencies between 71 and 275 GHz that can get through the Earth's atmosphere. "We have formal access to all three atmospheric 'windows', apart from their very edges," said Dr. Tom Gergely of the National Science Foundation, one of the U.S. delegates to WRC-00. The WRC also changed most of the frequencies allocated to satellite downlinks within the 71-275 GHz range to frequencies not used for science. Since no satellites yet operate at these high frequencies, no equipment needs to be altered. "Commercial technologies are just starting to develop above 50 GHz," said Dr. Klaus Ruf, Chairman of the Inter-Union Commission for the Allocation of Frequencies. "The WRC's actions mean that, when they are, radio astronomers should be able to share this part of the spectrum with most terrestrial services." The World Radiocommunication Conference is held every two or three years. Here member countries of the International Telecommunication Union meet to painstakingly parcel out the radio frequency spectrum between radio-based applications such as personal communications, satellite broadcasting, GPS and amateur radio, and the sciences of radio astronomy, earth exploration and deep space research. The WRC also coordinates sharing between services in the same radio bands. WRC decisions are incorporated into the Radio Regulations that govern radio services worldwide. The new spectrum allocations for radio astronomy are the first since 1979. Millimeter-wave astronomy was then in its infancy and many of its needs were not yet known. As astronomers began to explore this region of the spectrum they found spectral lines from many interesting molecules in space. Many of those lines had not fallen into the areas originally set aside for astronomy, but most will be under the new allocations. "It's a win for millimeter-wave science," said Dr. John Whiteoak of the Australia Telescope National Facility, Australian delegate to WRC-00. "This secures its future." The protection is a significant step for both existing millimeter-wave telescopes and new ones such as the Atacama Large Millimeter Array (ALMA) now being planned by a U.S.-European consortium. Even at its isolated site in Chile's Atacama desert, ALMA would be vulnerable to interference from satellite emissions. Sensitive radio astronomy receivers are blinded by these emissions, just as an optical telescope would be by a searchlight. "There is more energy at millimeter and sub-millimeter wavelengths washing through the Universe than there is of light or any other kind of radiation," said ALMA Project Scientist, Dr. Al Wootten of the National Radio Astronomy Observatory. "Imaging the sources of this energy can tell us a great deal about the formation of stars and galaxies, and even planets." "But the Earth's atmosphere isn't very kind to us - it has only a few windows at these frequencies, and not very transparent ones at that. They are easily clogged up. It's very important that we keep them as free as possible from interference." The new spectrum allocations were welcomed by Dr Johannes Andersen, General Secretary of the International Astronomical Union, which represents astronomers worldwide. "Protecting our ability to observe the Universe is the top priority for the International Astronomical Union," he said. "This action shows that international bodies accept the need for environmental emission standards in space as well as on Earth, for the benefit of all."

Excitation of small-scale waves in the F region of the ionosphere by powerful HF radio waves

NASA Astrophysics Data System (ADS)

Blagoveshchenskaya, N. F.; Chernyshev, M. Y.; Kornienko, V. A.

1998-01-01

Ionospheric small-scale waves in the F region, initiated by heating facilities in Nizhniy Novgorod, have been studied by the method of field-aligned scattering of diagnostic HF radio signals. Experimental data have been obtained on the radio path Kiev-N. Novgorod-St. Petersburg during heating campaigns with heater radiated power ERP = 20 MW and 100 MW. Observations of scattered HF signals have been made by a Doppler spectrum device with high temporal resolution. Analysis of the experimental data shows a relation between the heater power level and the parameters of ionospheric small-scale oscillations falling within the range of Pc 3-4 magnetic pulsations. It is found that the periods of wave processes in the F region of the ionosphere, induced by the heating facility, decrease with increasing heating power. The level of heating power also has an impact on the horizontal east-west component of the electric field E, the vertical component of the Doppler velocity Vd and the amplitude of the vertical displacements M of the heated region. Typical magnitudes of these parameters are the following: E = 1.25 mVm, Vd = 6 ms, M = 600-1500 m for ERP = 20 MW and E = 2.5-4.5 mVm, Vd = 11-25 ms, M = 1000-5000 m for ERP = 100 MW. The results obtained confirm the hypothesis of excitation of the Alfvén resonator by powerful HF radio waves which leads to the generation of magnetic field oscillations in the heated region giving rise to artificial Pc 3-4 magnetic pulsations and ionospheric small-scale wave processes. In this situation an increase of the heater power would lead to a growth of the electric field of hydromagnetic waves propagating in the ionosphere as well as the amplitude of the vertical displacements of the heated region.

The effect of plasma inhomogeneities on (i) radio emission generation by non-gyrotropic electron beams and (ii) particle acceleration by Langmuir waves

NASA Astrophysics Data System (ADS)

Tsiklauri, D.

2014-12-01

Extensive particle-in-cell simulations of fast electron beams injected in a background magnetised plasma with a decreasing density profile were carried out. These simulations were intended to further shed light on a newly proposed mechanism for the generation of electromagnetic waves in type III solar radio bursts [1]. Here recent progress in an alternative to the plasma emission model using Particle-In-Cell, self-consistent electromagnetic wave emission simulations of solar type III radio bursts will be presented. In particular, (i) Fourier space drift (refraction) of non-gyrotropic electron beam-generated wave packets, caused by the density gradient [1,2], (ii) parameter space investigation of numerical runs [3], (iii) concurrent generation of whistler waves [4] and a separate problem of (iv) electron acceleration by Langmuir waves in a background magnetised plasma with an increasing density profile [5] will be discussed. In all considered cases the density inhomogeneity-induced wave refraction plays a crucial role. In the case of non-gyrotropic electron beam, the wave refaction transforms the generated wave packets from standing into freely escaping EM radiation. In the case of electron acceleration by Langmuir waves, a positive density gradient in the direction of wave propagation causes a decrease in the wavenumber, and hence a higher phase velocity vph=ω/k. The k-shifted wave is then subject to absorption by a faster electron by wave-particle interaction. The overall effect is an increased number of high energy electrons in the energy spectrum. [1] D. Tsiklauri, Phys. Plasmas 18, 052903 (2011) [2] H. Schmitz, D. Tsiklauri, Phys. Plasmas 20, 062903 (2013) [3] R. Pechhacker, D. Tsiklauri, Phys. Plasmas 19, 112903 (2012) [4] M. Skender, D. Tsiklauri, Phys. Plasmas 21, 042904 (2014) [5] R. Pechhacker, D. Tsiklauri, Phys. Plasmas 21, 012903 (2014)

Atmospheric Waves and Dynamics Beneath Jupiters Clouds from Radio Wavelength Observations

NASA Technical Reports Server (NTRS)

Cosentino, Richard G.; Butler, Bryan; Sault, Bob; Morales-Juberias, Raul; Simon, Amy; De Pater, Imke

2017-01-01

We observed Jupiter at wavelengths near 2 cm with the Karl G. Jansky Very Large Array (VLA) in February 2015. These frequencies are mostly sensitive to variations in ammonia abundance and probe between approx. 0.5- 2.0 bars of pressure in Jupiters atmosphere; within and below the visible cloud deck which has its base near 0.7 bars. The resultant observed data were projected into a cylindrical map of the planet with spatial resolution of approx. 1500 km at the equator. We have examined the data for atmospheric waves and observed a prominent bright belt of radio hotspot features near 10 N, likely connected to the same equatorial wave associated with the 5-m hotspots. We conducted a passive tracer power spectral wave analysis for the entire map and latitude regions corresponding to eastward and westward jets and compare our results to previous studies. The power spectra analysis revealed that the atmosphere sampled in our observation (excluding the NEB region) is in a 2-D turbulent regime and its dynamics are predominately governed by the shallow water equations. The Great Red Spot (GRS) is also very prominent and has a noticeable meridional asymmetry and we compare it, and nearby storms, with optical images. We find that the meridional radio profile has a global north-south hemisphere distinction and find correlations of it to optical intensity banding and to shear zones of the zonal wind profile over select regions of latitude. Amateur optical images taken before and after our observation complemented the radio wave- length map to investigate dynamics of the equatorial region in Jupiters atmosphere. We find that two radio hotspots at 2 cm are well correlated with optical plumes in the NEB, additionally revealing they are not the same 5 m hotspot features correlated with optical dark patches between adjacent plumes. This analysis exploits the VLAs upgraded sensitivity and explores the opportunities now possible when studying gas giants, especially atmospheric dynamics of layers beneath upper level clouds.

Involuntary human hand movements due to FM radio waves in a moving van.

PubMed

Huttunen, P; Savinainen, A; Hänninen, Osmo; Myllylä, R

2011-06-01

Finland TRACT Involuntary movements of hands in a moving van on a public road were studied to clarify the possible role of frequency modulated radio waves on driving. The signals were measured in a direct 2 km test segment of an international road during repeated drives to both directions. Test subjects (n=4) had an ability to sense radio frequency field intensity variations of the environment. They were sitting in a minivan with arm movement detectors in their hands. A potentiometer was used to register the hand movements to a computer which simultaneously collected data on the amplitude of the RF signal of the local FM tower 30 km distance at a frequency of about 100 MHz. Involuntary hand movements of the test subjects correlated with electromagnetic field, i.e. FM radio wave intensity measured. They reacted also on the place of a geomagnetic anomaly crossing the road, which was found on the basis of these recordings and confirmed by the public geological maps of the area.In conclusion, RF irradiation seems to affect the human hand reflexes of sensitive persons in a moving van along a normal public road which may have significance in traffic safety.

N V Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation of the Russian Academy of Sciences (IZMIRAN) yesterday, today, tomorrow

NASA Astrophysics Data System (ADS)

Kuznetsov, V. D.

2015-06-01

This paper describes the basic and applied research rationale for the organization of IZMIRAN and provides insight into the 75 years of the Institute's activities and development. Historically, early magnetic measurements in Russia were developed largely to meet the Navy's navigation needs and were, more generally, stimulated by the Peter the Great decrees and by the foundation of the St. Petersburg Academy of Sciences in 1724. The paper examines the roles of the early Academicians in developing geomagnetism and making magnetic measurements a common practice in Russia. The need for stable radio communications prompted ionospheric and radio wave propagation research. The advent of the space era and the 1957-1958 International Geophysical Year Project greatly impacted the development of IZMIRAN and spurred the creation of a number of geophysical research institutes throughout the country. Currently, the research topics at IZMIRAN range widely from geomagnetism to solar-terrestrial physics to the ionosphere and radio wave propagation, and its primary application areas are the study and forecast of space weather, an increasingly important determining factor in ever-expanding ground- and space-based technologies (space navigation and communications, space activities, etc.).

Doppler-multipath tolerant voice communication

NASA Astrophysics Data System (ADS)

Harris, R. M.

Line of sight communication between high performance aircraft has been found to be subject to a peculiar form of multipath radio wave propagation - Doppler multipath. It degrades analogue voice reception on the standard fit ultrahigh frequency radio, producing low frequency random noise and warbling. Various modifications were carried out on the aircraft's communications system, but the problem remained. All the evidence points to a natural phenomenon. The reported observations are corroborated by theoretical studies and laboratory simulations of multipath radio wave propagation between two points moving relative to a diffusely scattering reflector. Theoretical predictions of Rician fading have explained the disruption of speech transmitted using conventional dsb(am) modulation. This also indicated suppressing the carrier as a radical cure. Double sideband suppressed carrier radios have been developed for airborne evaluation in comparison with standard dsb(am). The air to air flying trials proved the superior performance of the suppressed carrier system under conditions of Doppler multipath.

Modelling and mitigating refractive propagation effects in precision pulsar timing observations

NASA Astrophysics Data System (ADS)

Shannon, R. M.; Cordes, J. M.

2017-01-01

To obtain the most accurate pulse arrival times from radio pulsars, it is necessary to correct or mitigate the effects of the propagation of radio waves through the warm and ionized interstellar medium. We examine both the strength of propagation effects associated with large-scale electron-density variations and the methodology used to estimate infinite frequency arrival times. Using simulations of two-dimensional phase-varying screens, we assess the strength and non-stationarity of timing perturbations associated with large-scale density variations. We identify additional contributions to arrival times that are stochastic in both radio frequency and time and therefore not amenable to correction solely using times of arrival. We attribute this to the frequency dependence of the trajectories of the propagating radio waves. We find that this limits the efficacy of low-frequency (metre-wavelength) observations. Incorporating low-frequency pulsar observations into precision timing campaigns is increasingly problematic for pulsars with larger dispersion measures.

Radio Telescope Focal Container for the Russian VLBI Network of New Generation

NASA Technical Reports Server (NTRS)

Ipatov, Alexander; Mardyshkin, Vyacheslav; Cherepanov, Andrey; Chernov, Vitaly; Diky, Dmitry; Khvostov, Evgeny; Yevstigneyev, Alexander

2010-01-01

This article considers the development of the structure of receivers for Russian radio telescopes. The development of these radio telescopes is undertaken within the project for creating a Russian small-antenna-based radio interferometer of new generation. It is shown that for small antennas (10. 12 meter) the principal unit, which provides the best SNR, is the so-called focal container placed at primary focus. It includes the primary feed, HEMT LNA, and cryogenic cooling system down to 20. K. A new multi-band feed based on traveling wave resonators is used. It has small dimensions, low weight, and allows working with circular polarizations. Thus it can be placed into focal container and cooled with the LNA. A sketch of the focal container, with traveling-wave-resonator feed, and calculations of the expected parameters of the multi-band receiver are presented.

Electron acceleration to high energies at quasi-parallel shock waves in the solar corona

NASA Technical Reports Server (NTRS)

Mann, G.; Classen, H.-T.

1995-01-01

In the solar corona shock waves are generated by flares and/or coronal mass ejections. They manifest themselves in solar type 2 radio bursts appearing as emission stripes with a slow drift from high to low frequencies in dynamic radio spectra. Their nonthermal radio emission indicates that electrons are accelerated to suprathermal and/or relativistic velocities at these shocks. As well known by extraterrestrial in-situ measurements supercritical, quasi-parallel, collisionless shocks are accompanied by so-called SLAMS (short large amplitude magnetic field structures). These SLAMS can act as strong magnetic mirrors, at which charged particles can be reflected and accelerated. Thus, thermal electrons gain energy due to multiple reflections between two SLAMS and reach suprathermal and relativistic velocities. This mechanism of accelerating electrons is discussed for circumstances in the solar corona and may be responsible for the so-called 'herringbones' observed in solar type 2 radio bursts.

Pulse based sensor networking using mechanical waves through metal substrates

NASA Astrophysics Data System (ADS)

Lorenz, S.; Dong, B.; Huo, Q.; Tomlinson, W. J.; Biswas, S.

2013-05-01

This paper presents a novel wireless sensor networking technique using ultrasonic signal as the carrier wave for binary data exchange. Using the properties of lamb wave propagation through metal substrates, the proposed network structure can be used for runtime transport of structural fault information to ultrasound access points. Primary applications of the proposed sensor networking technique will include conveying fault information on an aircraft wing or on a bridge to an ultrasonic access point using ultrasonic wave through the structure itself (i.e. wing or bridge). Once a fault event has been detected, a mechanical pulse is forwarded to the access node using shortest path multi-hop ultrasonic pulse routing. The advantages of mechanical waves over traditional radio transmission using pulses are the following: First, unlike radio frequency, surface acoustic waves are not detectable outside the medium, which increases the inherent security for sensitive environments in respect to tapping. Second, event detection can be represented by the injection of a single mechanical pulse at a specific temporal position, whereas radio messages usually take several bits. The contributions of this paper are: 1) Development of a transceiver for transmitting/receiving ultrasound pulses with a pulse loss rate below 2·10-5 and false positive rate with an upper bound of 2·10-4. 2) A novel one-hop distance estimation based on the properties of lamb wave propagation with an accuracy of above 80%. 3) Implementation of a wireless sensor network using mechanical wave propagation for event detection on a 2024 aluminum alloy commonly used for aircraft skin construction.

Pulsed radio frequency energy in the treatment of complex diabetic foot wounds: two cases.

PubMed

Larsen, Jerrie A; Overstreet, Julia

2008-01-01

The use of radio waves (pulsed radio frequency energy) has become well accepted in the treatment of chronic wounds. We present 2 cases of complex diabetic foot wounds treated adjunctively with outpatient pulsed radio frequency energy using a solid-state, 27.12 MHz fixed power output radio frequency generator that transmits a fixed dose of nonionizing, nonthermal electromagnetic energy through an applicator pad. This therapy, in combination with offloading, debridement and advanced dressings, resulted in closure of both wounds in approximately 16 weeks.

Comparison of techniques for approximating ocean bottom topography in a wave-refraction computer model

NASA Technical Reports Server (NTRS)

Poole, L. R.

1975-01-01

A study of the effects of using different methods for approximating bottom topography in a wave-refraction computer model was conducted. Approximation techniques involving quadratic least squares, cubic least squares, and constrained bicubic polynomial interpolation were compared for computed wave patterns and parameters in the region of Saco Bay, Maine. Although substantial local differences can be attributed to use of the different approximation techniques, results indicated that overall computed wave patterns and parameter distributions were quite similar.

Atmospheric waves on Venus as seen by the Venus Express Radio Science Experiment VeRa

NASA Astrophysics Data System (ADS)

Tellmann, S.; Häusler, B.; Hinson, D. P.; Tyler, G. L.; Andert, T. P.; Bird, M. K.; Imamura, T.; Pätzold, M.; Remus, S.

2013-09-01

Next to quasi-horizontal waves and eddies on near planetary scales, diurnally forced eddies and thermal tides, small-scale gravity waves and turbulence play a significant role in the development and maintenance of atmospheric super rotation.

An extreme magneto-ionic environment associated with the fast radio burst source FRB 121102

NASA Astrophysics Data System (ADS)

Michilli, D.; Seymour, A.; Hessels, J. W. T.; Spitler, L. G.; Gajjar, V.; Archibald, A. M.; Bower, G. C.; Chatterjee, S.; Cordes, J. M.; Gourdji, K.; Heald, G. H.; Kaspi, V. M.; Law, C. J.; Sobey, C.; Adams, E. A. K.; Bassa, C. G.; Bogdanov, S.; Brinkman, C.; Demorest, P.; Fernandez, F.; Hellbourg, G.; Lazio, T. J. W.; Lynch, R. S.; Maddox, N.; Marcote, B.; McLaughlin, M. A.; Paragi, Z.; Ransom, S. M.; Scholz, P.; Siemion, A. P. V.; Tendulkar, S. P.; van Rooy, P.; Wharton, R. S.; Whitlow, D.

2018-01-01

Fast radio bursts are millisecond-duration, extragalactic radio flashes of unknown physical origin. The only known repeating fast radio burst source—FRB 121102—has been localized to a star-forming region in a dwarf galaxy at redshift 0.193 and is spatially coincident with a compact, persistent radio source. The origin of the bursts, the nature of the persistent source and the properties of the local environment are still unclear. Here we report observations of FRB 121102 that show almost 100 per cent linearly polarized emission at a very high and variable Faraday rotation measure in the source frame (varying from +1.46 × 105 radians per square metre to +1.33 × 105 radians per square metre at epochs separated by seven months) and narrow (below 30 microseconds) temporal structure. The large and variable rotation measure demonstrates that FRB 121102 is in an extreme and dynamic magneto-ionic environment, and the short durations of the bursts suggest a neutron star origin. Such large rotation measures have hitherto been observed only in the vicinities of massive black holes (larger than about 10,000 solar masses). Indeed, the properties of the persistent radio source are compatible with those of a low-luminosity, accreting massive black hole. The bursts may therefore come from a neutron star in such an environment or could be explained by other models, such as a highly magnetized wind nebula or supernova remnant surrounding a young neutron star.

An extreme magneto-ionic environment associated with the fast radio burst source FRB 121102.

PubMed

Michilli, D; Seymour, A; Hessels, J W T; Spitler, L G; Gajjar, V; Archibald, A M; Bower, G C; Chatterjee, S; Cordes, J M; Gourdji, K; Heald, G H; Kaspi, V M; Law, C J; Sobey, C; Adams, E A K; Bassa, C G; Bogdanov, S; Brinkman, C; Demorest, P; Fernandez, F; Hellbourg, G; Lazio, T J W; Lynch, R S; Maddox, N; Marcote, B; McLaughlin, M A; Paragi, Z; Ransom, S M; Scholz, P; Siemion, A P V; Tendulkar, S P; Van Rooy, P; Wharton, R S; Whitlow, D

2018-01-10

Fast radio bursts are millisecond-duration, extragalactic radio flashes of unknown physical origin. The only known repeating fast radio burst source-FRB 121102-has been localized to a star-forming region in a dwarf galaxy at redshift 0.193 and is spatially coincident with a compact, persistent radio source. The origin of the bursts, the nature of the persistent source and the properties of the local environment are still unclear. Here we report observations of FRB 121102 that show almost 100 per cent linearly polarized emission at a very high and variable Faraday rotation measure in the source frame (varying from +1.46 × 10 5 radians per square metre to +1.33 × 10 5 radians per square metre at epochs separated by seven months) and narrow (below 30 microseconds) temporal structure. The large and variable rotation measure demonstrates that FRB 121102 is in an extreme and dynamic magneto-ionic environment, and the short durations of the bursts suggest a neutron star origin. Such large rotation measures have hitherto been observed only in the vicinities of massive black holes (larger than about 10,000 solar masses). Indeed, the properties of the persistent radio source are compatible with those of a low-luminosity, accreting massive black hole. The bursts may therefore come from a neutron star in such an environment or could be explained by other models, such as a highly magnetized wind nebula or supernova remnant surrounding a young neutron star.

Radial distribution of compressive waves in the solar corona revealed by Akatsuki radio occultation observations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miyamoto, Mayu; Imamura, Takeshi; Ando, Hiroki

Radial variations of the amplitude and the energy flux of compressive waves in the solar corona were explored for the first time using a spacecraft radio occultation technique. By applying wavelet analysis to the frequency time series taken at heliocentric distances of 1.5-20.5 R{sub S} (solar radii), quasi-periodic density disturbances were detected at almost all distances. The period ranges from 100 to 2000 s. The amplitude of the fractional density fluctuation increases with distance and reaches ∼30% around 5 R{sub S} , implying that nonlinearity of the wave field is potentially important. We further estimate the wave energy flux onmore » the assumption that the observed periodical fluctuations are manifestations of acoustic waves. The energy flux increases with distance below ∼6 R{sub S} and seems to saturate above this height, suggesting that the acoustic waves do not propagate from the low corona but are generated in the extended corona, probably through nonlinear dissipation of Alfvén waves. The compressive waves should eventually dissipate through shock generation to heat the corona.« less

Laboratory evaluation and application of microwave absorption properties under simulated conditions for planetary atmospheres

NASA Technical Reports Server (NTRS)

Steffes, Paul G.

1989-01-01

Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments and earth-based radio astronomical observations can be used to infer abundances of microwave absorbing atmospheric constituents in those atmospheres, as long as reliable information regarding the microwave absorbing properties of potential constituents is available. Work performed has shown that laboratory measurements of the millimeter-wave opacity of ammonia between 7.5 mm and 9.3 mm and also at the 3.2 mm wavelength require a different lineshape to be used in the theoretical prediction for millimeter-wave ammonia opacity than was previously used. The recognition of the need to make such laboratory measurements of simulated planetary atmospheres over a range of temperatures and pressures which correspond to the altitudes probed by both radio occultation experiments and radio astronomical observations, and over a range of frequencies which correspond to those used in both radio occultation experiments and radio astronomical observations, has led to the development of a facility at Georgia Tech which is capable of making such measurements. It has been the goal of this investigation to conduct such measurements and to apply the results to a wide range of planetary observations, both spacecraft and earth-based, in order to determine the identity and abundance profiles of constituents in those planetary atmospheres.

Gravitational waves from binary supermassive black holes missing in pulsar observations.

PubMed

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

2015-09-25

Gravitational waves are expected to be radiated by supermassive black hole binaries formed during galaxy mergers. A stochastic superposition of gravitational waves from all such binary systems would modulate the arrival times of pulses from radio pulsars. Using observations of millisecond pulsars obtained with the Parkes radio telescope, we constrained the characteristic amplitude of this background, A(c,yr), to be <1.0 × 10(-15) with 95% confidence. This limit excludes predicted ranges for A(c,yr) from current models with 91 to 99.7% probability. We conclude that binary evolution is either stalled or dramatically accelerated by galactic-center environments and that higher-cadence and shorter-wavelength observations would be more sensitive to gravitational waves. Copyright © 2015, American Association for the Advancement of Science.

Multi-Band Multi-Tone Tunable Millimeter-Wave Frequency Synthesizer For Satellite Beacon Transmitter

NASA Technical Reports Server (NTRS)

Simons, Rainee N.; Wintucky, Edwin G.

2016-01-01

This paper presents the design and test results of a multi-band multi-tone tunable millimeter-wave frequency synthesizer, based on a solid-state frequency comb generator. The intended application of the synthesizer is in a satellite beacon transmitter for radio wave propagation studies at K-band (18 to 26.5 GHz), Q-band (37 to 42 GHz), and E-band (71 to 76 GHz). In addition, the architecture for a compact beacon transmitter, which includes the multi-tone synthesizer, polarizer, horn antenna, and power/control electronics, has been investigated for a notional space-to-ground radio wave propagation experiment payload on a small satellite. The above studies would enable the design of robust high throughput multi-Gbps data rate future space-to-ground satellite communication links.

High power water load for microwave and millimeter-wave radio frequency sources

DOEpatents

Ives, R. Lawrence; Mizuhara, Yosuke M.; Schumacher, Richard V.; Pendleton, Rand P.

1999-01-01

A high power water load for microwave and millimeter wave radio frequency sources has a front wall including an input port for the application of RF power, a cylindrical dissipation cavity lined with a dissipating material having a thickness which varies with depth, and a rear wall including a rotating reflector for the reflection of wave energy inside the cylindrical cavity. The dissipation cavity includes a water jacket for removal of heat generated by the absorptive material coating the dissipation cavity, and this absorptive material has a thickness which is greater near the front wall than near the rear wall. Waves entering the cavity reflect from the rotating reflector, impinging and reflecting multiple times on the absorptive coating of the dissipation cavity, dissipating equal amounts of power on each internal reflection.

Experimental demonstration of 24-Gb/s CAP-64QAM radio-over-fiber system over 40-GHz mm-wave fiber-wireless transmission.

PubMed

Zhang, Junwen; Yu, Jianjun; Chi, Nan; Li, Fan; Li, Xinying

2013-11-04

We propose and demonstrate a novel CAP-ROF system based on multi-level carrier-less amplitude and phase modulation (CAP) 64QAM with high spectrum efficiency for mm-wave fiber-wireless transmission. The performance of novel CAP modulation with high order QAM, for the first time, is investigated in the mm-wave fiber-wireless transmission system. One I/Q modulator is used for mm-wave generation and base-band signal modulation based on optical carrier suppression (OCS) and intensity modulation. Finally, we demonstrated a 24-Gb/s CAP-64QAM radio-over-fiber (ROF) system over 40-km stand single-mode-fiber (SMMF) and 1.5-m 38-GHz wireless transmission. The system operation factors are also experimentally investigated.

INSPIRE - Premission. [Interactive NASA Space Physics Ionosphere Radio Experiment

NASA Technical Reports Server (NTRS)

Taylor, William W. L.; Mideke, Michael; Pine, William E.; Ericson, James D.

1992-01-01

The Interactive NASA Space Physics Ionosphere Radio Experiment (INSPIRE) designed to assist in a Space Experiments with Particle Accelerators (SEPAC) project is discussed. INSPIRE is aimed at recording data from a large number of receivers on the ground to determine the exact propagation paths and absorption of radio waves at frequencies between 50 Hz and 7 kHz. It is indicated how to participate in the experiment that will involve high school classes, colleges, and amateur radio operators.

Division x: Radio Astronomy

NASA Astrophysics Data System (ADS)

Taylor, Russ; Chapman, Jessica; Rendong, Nan; Carilli, Christopher; Giovannini, Gabriele; Hills, Richard; Hirabayashi, Hisashi; Jonas, Justin; Lazio, Joseph; Morganti, Raffaella; Rubio, Monica; Shastri, Prajval

2012-04-01

This triennium has seen a phenomenal investment in development of observational radio astronomy facilities in all parts of the globe at a scale that significantly impacts the international community. This includes both major enhancements such as the transition from the VLA to the EVLA in North America, and the development of new facilities such as LOFAR, ALMA, FAST, and Square Kilometre Array precursor telescopes in Australia and South Africa. These developments are driven by advances in radio-frequency, digital and information technologies that tremendously enhance the capabilities in radio astronomy. These new developments foreshadow major scientific advances driven by radio observations in the next triennium. We highlight these facility developments in section 3 of this report. A selection of science highlight from this triennium are summarized in section 2.

Phenomena Associated with EIT Waves

NASA Technical Reports Server (NTRS)

Thompson, B. J.; Biesecker, D. A.; Gopalswamy, N.; Fisher, Richard R. (Technical Monitor)

2002-01-01

We discuss phenomena associated with 'EIT Wave' transients. These phenomena include coronal mass ejections, flares, EUV/SXR dimmings, chromospheric waves, Moreton waves, solar energetic particle events, energetic electron events, and radio signatures. Although the occurrence of many phenomena correlate with the appearance of EIT waves, it is difficult to infer which associations are causal. The presentation will include a discussion of correlation surveys of these phenomena.

Phenomena Associated With EIT Waves

NASA Technical Reports Server (NTRS)

Thompson, B. J.; Biesecker, D. A.; Gopalswamy, N.

2003-01-01

We discuss phenomena associated with "EIT Wave" transients. These phenomena include coronal mass ejections, flares, EUV/SXR dimmings, chromospheric waves, Moreton waves, solar energetic particle events, energetic electron events, and radio signatures. Although the occurrence of many phenomena correlate with the appearance of EIT waves, it is difficult to mfer which associations are causal. The presentation will include a discussion of correlation surveys of these phenomena.

Ionospheric electron heating, optical emissions, and striations induced by powerful HF radio waves at high latitudes: Aspect angle dependence

NASA Astrophysics Data System (ADS)

Rietveld, M. T.; Kosch, M. J.; Blagoveshchenskaya, N. F.; Kornienko, V. A.; Leyser, T. B.; Yeoman, T. K.

2003-04-01

In recent years, large electron temperature increases of 300% (3000 K above background) caused by powerful HF-radio wave injection have been observed during nighttime using the EISCAT incoherent scatter radar near Tromsø in northern Norway. In a case study we examine the spatial structure of the modified region. The electron heating is accompanied by ion heating of about 100 degrees and magnetic field-aligned measurements show ion outflows increasing with height up to 300 m s-1 at 582 km. The electron density decreases by up to 20%. When the radar antenna was scanned between three elevations from near field-aligned to vertical, the strongest heating effects were always obtained in the field-aligned position. When the HF-pump beam was scanned between the same three positions, the heating was still almost always strongest in the field-aligned direction. Simultaneous images of the 630 nm O(1D) line in the radio-induced aurora showed that the enhancement caused by the HF radio waves also remained localized near the field-aligned position. Coherent HF radar backscatter also appeared strongest when the pump beam was pointed field-aligned. These results are similar to some Langmuir turbulence phenomena which also show a strong preference for excitation by HF rays launched in the field-aligned direction. The correlation of the position of largest temperature enhancement with the position of the radio-induced aurora suggests that a common mechanism, upper-hybrid wave turbulence, is responsible for both effects. Why the strongest heating effects occur for HF rays directed along the magnetic field is still unclear, but self-focusing on field-aligned striations is a candidate mechanism, and possibly ionospheric tilts may be important.

The history of polarisation measurements: their role in studies of magnetic fields

NASA Astrophysics Data System (ADS)

Wielebinski, R.

2015-03-01

Radio astronomy gave us new methods to study magnetic fields. Synchrotron radiation, the main cause of comic radio waves, is highly linearly polarised with the `E' vector normal to the magnetic field. The Faraday Effect rotates the `E' vector in thermal regions by the magnetic field in the line of sight. Also the radio Zeeman Effect has been observed.

Interaction Between Two CMEs During 14 - 15 February 2011 and Their Unusual Radio Signature

NASA Astrophysics Data System (ADS)

Shanmugaraju, A.; Prasanna Subramanian, S.; Vrsnak, Bojan; Ibrahim, M. Syed

2014-12-01

We report a detailed analysis of an interaction between two coronal mass ejections (CMEs) that were observed on 14 - 15 February 2011 and the corresponding radio enhancement, which was similar to the "CME cannibalism" reported by Gopalswamy et al. ( Astrophys. J. 548, L91, 2001). A primary CME, with a mean field-of-view velocity of 669 km s-1 in the Solar and Heliospheric Observatory (SOHO)/ Large Angle Spectrometric Coronagraph (LASCO), was more than as twice as fast as the slow CME preceding it (326 km s-1), which indicates that the two CMEs interacted. A radio-enhancement signature (in the frequency range 1 MHz - 400 kHz) due to the CME interaction was analyzed and interpreted using the CME data from LASCO and from the Solar Terrestrial Relations Observatory (STEREO) HI-1, radio data from Wind/ Radio and Plasma Wave Experiment (WAVES), and employing known electron-density models and kinematic modeling. The following results are obtained: i) The CME interaction occurred around 05:00 - 10:00 UT in a height range 20 - 25 R⊙. An unusual radio signature is observed during the time of interaction in the Wind/WAVES dynamic radio spectrum. ii) The enhancement duration shows that the interaction segment might be wider than 5 R⊙. iii) The shock height estimated using density models for the radio enhancement region is 10 - 30 R⊙. iv) Using kinematic modeling and assuming a completely inelastic collision, the decrease of kinetic energy based on speeds from LASCO data is determined to be 0.77×1023 J, and 3.67×1023 J if speeds from STEREO data are considered. vi) The acceleration, momentum, and force are found to be a=-168 m s-2, I=6.1×1018 kg m s-1, and F=1.7×1015 N, respectively, using STEREO data.

The nightmare scenario: measuring the stochastic gravitational wave background from stalling massive black hole binaries with pulsar timing arrays

NASA Astrophysics Data System (ADS)

Dvorkin, Irina; Barausse, Enrico

2017-10-01

Massive black hole binaries, formed when galaxies merge, are among the primary sources of gravitational waves targeted by ongoing pulsar timing array (PTA) experiments and the upcoming space-based Laser Interferometer Space Antenna (LISA) interferometer. However, their formation and merger rates are still highly uncertain. Recent upper limits on the stochastic gravitational wave background obtained by PTAs are starting to be in marginal tension with theoretical models for the pairing and orbital evolution of these systems. This tension can be resolved by assuming that these binaries are more eccentric or interact more strongly with the environment (gas and stars) than expected, or by accounting for possible selection biases in the construction of the theoretical models. However, another (pessimistic) possibility is that these binaries do not merge at all, but stall at large (˜pc) separations. We explore this extreme scenario by using a semi-analytic galaxy formation model including massive black holes (isolated and in binaries), and show that future generations of PTAs will detect the stochastic gravitational wave background from the massive black hole binary population within 10-15 yr of observations, even in the `nightmare scenario' in which all binaries stall at the hardening radius. Moreover, we argue that this scenario is too pessimistic, because our model predicts the existence of a subpopulation of binaries with small mass ratios (q ≲ 10-3) that should merge within a Hubble time simply as a result of gravitational wave emission. This subpopulation will be observable with large signal-to-noise ratios by future PTAs thanks to next-generation radio telescopes such as Square Kilometre Array or Five-hundred-meter Aperture Spherical Telescope, and possibly by LISA.

Re-examination of radiofrequency mass spectrometers: Center Director's Discretionary Fund

NASA Technical Reports Server (NTRS)

Carruth, M. R., Jr.

1989-01-01

The three-stage, two-cycle, Bennett mass spectrometers in use in space and ground experiments today are of the same physical configuration as developed by Bennett in 1950. Sine-wave radiofrequency (RF) is also still used. The literature indicates that the electronics and physical manufacturing capabilities of 1950 technology may have limited the use of other improvements at that time. Therefore, a study, experimental and analytical, was undertaken to examine previously rejected RF approaches as well as new ones. The results of this study indicate there are other approaches which use fewer grids and square wave or a combination of square-wave and sine-wave RF. In regard to suppression of harmonics, none performed better than the three-stage, two-cycle, Bennett mass spectrometer. Use of square-wave RF in the Bennett approach can provide a slightly more compact configuration but no increase in throughput.

ULF radio monitoring network in a seismic area

NASA Astrophysics Data System (ADS)

Toader, Victorin; Moldovan, Iren-Adelina; Ionescu, Constantin; Marmureanu, Alexandru

2017-04-01

ULF monitoring is a part of a multidisciplinary network (AeroSolSys) located in Vrancea (Curvature Carpathian Mountains). Four radio receivers (100 kHz - microwave) placed on faults in a high seismic area characterized by deep earthquakes detect fairly weak radio waves. The radio power is recorded in correlation with many other parameters related to near surface low atmosphere phenomena (seismicity, solar radiation, air ionization, electromagnetic activity, radon, CO2 concentration, atmospheric pressure, telluric currents, infrasound, seismo-acoustic emission, meteorological information). We follow variations in the earth's surface propagate radio waves avoiding reflection on ionosphere. For this reason the distance between stations is less than 60 km and the main source of emission is near (Bod broadcasting transmitter for long- and medium-wave radio, next to Brasov city). In the same time tectonic stress affects the radio propagation in air and it could generates ULF waves in ground (LAI coupling). To reduce the uncertainty is necessary to monitor a location for extended periods of time to outline local and seasonal fluctuations. Solar flares do not affect seismic activity but they produce disturbances in telecommunications networks and power grids. Our ULF monitoring correlated with two local magnetometers does not indicate this so far with our receivers. Our analysis was made during magnetic storms with Kp 7 and 8 according to NOAA satellites. To correlate the results we implemented an application that monitors the satellite EUTELSAT latency compared to WiMAX land communication in the same place. ULF band radio monitoring showed that our receiver is dependent on temperature and that it is necessary to introduce a band pass filter in data analysis. ULF data acquisition is performed by Kinemetrics and National Instruments digitizers with a sampling rate of 100 Hz in Miniseed format and then converted into text files with 1 Hz rate for analysis in very low frequency. In both cases we use spectrum analysis in three bands of frequency with different filters. More results showed that tectonic stress generated by seismicity is more important than effects of solar flares. This work was partially supported by the Partnership in Priority Areas Program - PNII, under MEN-UEFISCDI, DARING Project no. 69/2014 and the Nucleu Program - PN 16-35, Project no. 03 01.

LANDSAT-D investigations in snow hydrology

NASA Technical Reports Server (NTRS)

Dozier, J. (Principal Investigator)

1982-01-01

Snow reflectance in all 6 TM reflective bands, i.e., 1, 2, 3, 4, 5, and 7 was simulated using a delta-Eddington model. Snow reflectance in bands 4, 5, and 7 appear sensitive to grain size. It appears that the TM filters resemble a ""square-wave'' closely enough that a square-wave can be assumed in calculations. Integrated band reflectance over the actual response functions was calculated using sensor data supplied by Santa Barbara Research Center. Differences between integrating over the actual response functions and the equivalent square wave were negligible. Tables are given which show (1) sensor saturation radiance as a percentage of the solar constant, integrated through the band response function; (2) comparisons of integrations through the sensor response function with integrations over the equivalent square wave; and (3) calculations of integrated reflectance for snow over all reflective TM bands, and water and ice clouds with thickness of 1 mm water equivalent over TM bands 5 and 7. These calculations look encouraging for snow/cloud discrimination with TM bands 5 and 7.

Lamb waves in phononic crystal slabs with square or rectangular symmetries

NASA Astrophysics Data System (ADS)

Brunet, Thomas; Vasseur, Jérôme; Bonello, Bernard; Djafari-Rouhani, Bahram; Hladky-Hennion, Anne-Christine

2008-08-01

We report on both numerical and experimental results showing the occurrence of band gaps for Lamb waves propagating in phononic crystal plates. The structures are made of centered rectangular and square arrays of holes drilled in a silicon plate. A supercell plane wave expansion method is used to calculate the band structures and to predict the position and the magnitude of the gaps. The band structures of phononic crystal slabs are then measured using a laser ultrasonic technique. Lamb waves in the megahertz range and with wave vectors ranging over more than the first two reduced Brillouin zones are investigated.

Dispersive Evolution of Nonlinear Fast Magnetoacoustic Wave Trains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pascoe, D. J.; Goddard, C. R.; Nakariakov, V. M., E-mail: D.J.Pascoe@warwick.ac.uk

2017-10-01

Quasi-periodic rapidly propagating wave trains are frequently observed in extreme ultraviolet observations of the solar corona, or are inferred by the quasi-periodic modulation of radio emission. The dispersive nature of fast magnetohydrodynamic waves in coronal structures provides a robust mechanism to explain the detected quasi-periodic patterns. We perform 2D numerical simulations of impulsively generated wave trains in coronal plasma slabs and investigate how the behavior of the trapped and leaky components depend on the properties of the initial perturbation. For large amplitude compressive perturbations, the geometrical dispersion associated with the waveguide suppresses the nonlinear steepening for the trapped wave train.more » The wave train formed by the leaky components does not experience dispersion once it leaves the waveguide and so can steepen and form shocks. The mechanism we consider can lead to the formation of multiple shock fronts by a single, large amplitude, impulsive event and so can account for quasi-periodic features observed in radio spectra.« less

Verification of nonlinear particle simulation of radio frequency waves in fusion plasmas

NASA Astrophysics Data System (ADS)

Kuley, Animesh; Bao, Jian; Lin, Zhihong

2015-11-01

Nonlinear global particle simulation model has been developed in GTC to study the nonlinear interactions of radio frequency (RF) waves with plasmas in tokamak. In this model, ions are considered as fully kinetic particles using the Vlasov equation and electrons are treated as guiding centers using the drift kinetic. Boris push scheme for the ion motion has been implemented in the toroidal geometry using magnetic coordinates and successfully verified for the ion cyclotron, ion Bernstein and lower hybrid waves. The nonlinear GTC simulation of the lower hybrid wave shows that the amplitude of the electrostatic potential is oscillatory due to the trapping of resonant electrons by the electric field of the lower hybrid wave. The nonresonant parametric decay is observed an IBW sideband and an ion cyclotron quasimode (ICQM). The ICQM induces an ion perpendicular heating with a heating rate proportional to the pump wave intensity. This work is supported by PPPL subcontract number S013849-F and US Department of Energy (DOE) SciDAC GSEP Program.

MULTI-MESSENGER ASTRONOMY OF GRAVITATIONAL-WAVE SOURCES WITH FLEXIBLE WIDE-AREA RADIO TRANSIENT SURVEYS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yancey, Cregg C.; Shawhan, Peter; Bear, Brandon E.

We explore opportunities for multi-messenger astronomy using gravitational waves (GWs) and prompt, transient low-frequency radio emission to study highly energetic astrophysical events. We review the literature on possible sources of correlated emission of GWs and radio transients, highlighting proposed mechanisms that lead to a short-duration, high-flux radio pulse originating from the merger of two neutron stars or from a superconducting cosmic string cusp. We discuss the detection prospects for each of these mechanisms by low-frequency dipole array instruments such as LWA1, the Low Frequency Array and the Murchison Widefield Array. We find that a broad range of models may bemore » tested by searching for radio pulses that, when de-dispersed, are temporally and spatially coincident with a LIGO/Virgo GW trigger within a ∼30 s time window and ∼200–500 deg{sup 2} sky region. We consider various possible observing strategies and discuss their advantages and disadvantages. Uniquely, for low-frequency radio arrays, dispersion can delay the radio pulse until after low-latency GW data analysis has identified and reported an event candidate, enabling a prompt radio signal to be captured by a deliberately targeted beam. If neutron star mergers do have detectable prompt radio emissions, a coincident search with the GW detector network and low-frequency radio arrays could increase the LIGO/Virgo effective search volume by up to a factor of ∼2. For some models, we also map the parameter space that may be constrained by non-detections.« less

A comparison of techniques for inversion of radio-ray phase data in presence of ray bending

NASA Technical Reports Server (NTRS)

Wallio, H. A.; Grossi, M. D.

1972-01-01

Derivations are presented of the straight-line Abel transform and the seismological Herglotz-Wiechert transform (which takes ray bending into account) that are used in the reconstruction of refractivity profiles from radio-wave phase data. Profile inversion utilizing these approaches, performed in computer-simulated experiments, are compared for cases of positive, zero, and negative ray bending. For thin atmospheres and ionospheres, such as the Martian atmosphere and ionosphere, radio wave signals are shown to be inverted accurately with both methods. For dense media, such as the solar corona or the lower Venus atmosphere, the refractive recovered by the seismological Herglotz-Wiechert transform provide a significant improvement compared with the straight-line Abel transform.

Design and construction of prototype radio antenna for shortest radio wavelengths

NASA Technical Reports Server (NTRS)

Leighton, R. B.

1975-01-01

A paraboloid radio antenna of 10.4 meters diameter, 0.41 meter focal length was constructed and its successful completion is described. The surface accuracy of the antenna is at least four times better than any existing antenna in its class size (50 micrometers rms). Antenna design specifications (i.e., for mounting, drive motors, honeycomb structures) are discussed and engineering drawings and photographs of antenna components are shown. The antenna will be used for millimeter-wave interferometry and sub-millimeter wave radiometry over a full frequency range (up to approximately 860 GHz). The antenna will also be moveable (for interferometric use) between reinforced concrete pads by rail. The effects of the weather and gravity on antenna performance are briefly discussed.

Effects of irregularity anisotropy on Faraday polarization fluctuations

NASA Technical Reports Server (NTRS)

Lee, M. C.; Nghiem, S. V.; Yoo, C.

1989-01-01

The previous model (Lee et al., 1982) of the Faraday polarization fluctuations (FPF) is extended after taking into account the anisotropic nature of the commonly observed, rodlike and sheetlike ionospheric irregularities. Striking effects of irregularity anisotropy are found in the longitudinal radio propagation. However, if the wave propagation angle is not small (say, greater than 5 deg), the effects of irregularity anisotropy on FPF introduced by rodlike irregularities weaken significantly, while those caused by sheetlike irregularities remain prominent. Therefore, under the same ionospheric propagation conditions, sheetlike ionospheric irregularities are more effective than rodlike ionospheric irregularities in causing the FPF of radio waves. It is expected that intense FPF of VHF radio signals can be observed not only near the equatorial anomaly but also in the auroral region.

The Soviet contributions towards MAP/WINE

NASA Technical Reports Server (NTRS)

Rapoport, Z. TA.; Kazimirovsky, E. S.

1989-01-01

In the winter of 1983 to 1984, the research institutes of the Soviet Union took an active part in the accomplishment of the project Winter in Northern Europe (MAP/WINE) of the Middle Atmosphere Program. Different methods were used to measure temperature, direction and velocity of wind, turbulence, electron concentration in the lower ionosphere, and radio wave absorption. The study of the stratopheric warmings and the related changes in the mesosphere and lower ionosphere was considered of special importance. The analysis of the obtained data has shown, in particular, that during the stratospheric warmings the western wind in winter time becomes weaker and even reverses. At the same time period the electron concentration and the radio wave absorption in the lower ionosphere are often reduced. It is also observed that the high absorption zones move from west to east. These results confirm the concept about the role of the cyclonic circumpolar vortex in the transport of the auroral air to temperate latitudes and about the appearance of conditions for the winter anomalous radio wave absorption.

Conference on the Ionosphere and Radio Wave Propagation, 3rd, University of Sydney, Australia, February 11-15, 1985, Proceedings

NASA Astrophysics Data System (ADS)

Cole, D. G.; McNamara, L. F.

1985-12-01

Various papers on the ionosphere and radio wave propagation are presented. The subjects discussed include: day-to-day variability in foF2 at low latitudes over a solar cycle; semiempirical, low-latitude ionospheric model; remote sensing with the Jindalee skywave radar; photographic approach to irregularities in the 80-100 km region; interference of radio waves in a CW system; study of the F-region characteristics at Waltair; recent developments in the international reference ionosphere; research-oriented ionosonde with directional capabilities; and ionospheric forecasting for specific applications. Also addressed are: experimental and theoretical techniques for the equatorial F region; empirical models of ionospheric electron concentration; the Jindalee ionospheric sounding system; a semiempirical midlatitude ionospheric model; Es structure using an HF radar; short-term variations in f0F2 and IEC; nonreciprocity in Omega propagation observed at middle latitudes; propagation management for no acknowledge HF links; new techniques in ionospheric sounding and studies; and lunar effects in the ionospheric F region.

About the Modeling of Radio Source Time Series as Linear Splines

NASA Astrophysics Data System (ADS)

Karbon, Maria; Heinkelmann, Robert; Mora-Diaz, Julian; Xu, Minghui; Nilsson, Tobias; Schuh, Harald

2016-12-01

Many of the time series of radio sources observed in geodetic VLBI show variations, caused mainly by changes in source structure. However, until now it has been common practice to consider source positions as invariant, or to exclude known misbehaving sources from the datum conditions. This may lead to a degradation of the estimated parameters, as unmodeled apparent source position variations can propagate to the other parameters through the least squares adjustment. In this paper we will introduce an automated algorithm capable of parameterizing the radio source coordinates as linear splines.

Baseline-dependent averaging in radio interferometry

NASA Astrophysics Data System (ADS)

Wijnholds, S. J.; Willis, A. G.; Salvini, S.

2018-05-01

This paper presents a detailed analysis of the applicability and benefits of baseline-dependent averaging (BDA) in modern radio interferometers and in particular the Square Kilometre Array. We demonstrate that BDA does not affect the information content of the data other than a well-defined decorrelation loss for which closed form expressions are readily available. We verify these theoretical findings using simulations. We therefore conclude that BDA can be used reliably in modern radio interferometry allowing a reduction of visibility data volume (and hence processing costs for handling visibility data) by more than 80 per cent.

High Power Radio Wave Interactions within the D-Region Ionosphere

NASA Astrophysics Data System (ADS)

Moore, R. C.

2014-12-01

This paper highlights the best results obtained during D-region modification experiments performed by the University of Florida at the High-frequency Active Auroral Research Program (HAARP) observatory between 2007 and 2014. Over this period, we have seen a tremendous improvement in ELF/VLF wave generation efficiency. We have identified methods to characterize ambient and modified ionospheric properties and to discern and quantify specific types of interactions. We have demonstrated several important implications of HF cross-modulation effects, including "Doppler Spoofing" on HF radio waves. Throughout this talk, observations are compared with the predictions of an ionospheric HF heating model to provide context and guidance for future D-region modification experiments.

Research in space physics at the University of Iowa, 1982

NASA Technical Reports Server (NTRS)

Vanallen, J. A.; Frank, L. A.; Gurnett, D. A.; Shawhan, S. D.; Robison, E. D.; Robertson, T. D.

1983-01-01

The energetic particles and the electric, magnetic, and electromagnetic fields associated with the Earth, the Sun, the Moon, the planets, comets, and the interplanetary medium are examined. Matters under current investigation are following: energetic particles trapped in the Earth's magnetic field, origin and propagation of very low frequency radio waves and electrostatic, the magnetospheres of Jupiter, Saturn and prospectively Uranus and Neptune, diffusion of energetic particles in Saturn's magnetosphere, radio emissions from Jupiter and Saturn, solar modulation and the heliocentric radial dependence of the intensity of galactic cosmic rays, interplanetary propagation and acceleration of energetic particles, the theory of wave phenomena in turbulent plasmas, and basic wave-particle-chemical processes in the ionospheric plasma.

Reading Hertz's own dipole theory

NASA Astrophysics Data System (ADS)

Aničin, B. A.

2008-01-01

It is well known that the discoverer of radio waves, Heinrich Hertz, was the first man to apply Maxwell's electrodynamic theory to a problem in radio wave propagation. In this paper, we scrutinize his near-field lines of force using computers and his theory. In one of his four figures, a feature was found which was not to be obtained by computation. This feature, a self-intersecting line of force, more or less a figure of eight, appears strange to the eye. The clarity of the original work by H Hertz on electromagnetic waves should be of great value in both physics and engineering courses. This holds in particular for his Q function, almost completely forgotten today.

RF to millimeter wave integration and module technologies

NASA Astrophysics Data System (ADS)

Vähä-Heikkilä, T.

2015-04-01

Radio Frequency (RF) consumer applications have boosted silicon integrated circuits (IC) and corresponding technologies. More and more functions are integrated to ICs and their performance is also increasing. However, RF front-end modules with filters and switches as well as antennas still need other way of integration. This paper focuses to RF front-end module and antenna developments as well as to the integration of millimeter wave radios. VTT Technical Research Centre of Finland has developed both Low Temperature Co-fired Ceramics (LTCC) and Integrated Passive Devices (IPD) integration platforms for RF and millimeter wave integrated modules. In addition to in-house technologies, VTT is using module and component technologies from other commercial sources.

Geotechnical sensing using electromagnetic attenuation between radio transceivers

NASA Astrophysics Data System (ADS)

Ghazanfari, Ehsan; Pamukcu, Sibel; Yoon, Suk-Un; Suleiman, Muhannad T.; Cheng, Liang

2012-12-01

Monitoring the onset of a geo-event such as the intrusion of a chemical plume or a slow progressive mass slide that results in marked changes in the physical properties of the host soil could be potentially accomplished using a distributed network of embedded radio transceivers. This paper introduces a new concept of subsurface geo-event monitoring, which takes advantage of the spatial and temporal variations in signal strength of electromagnetic (EM) waves transmitted within the net of distributed radios within a sensing area. Results of experiments in the laboratory and the field demonstrated that variations in EM signal strength could be used to detect physical changes in the subsurface. Changes in selected physical properties of host soil including water content, density, and formation of discontinuities could be discerned from the changes in the signal strength of the transmitted wave between embedded radio transceivers. Good agreement was observed between a theoretical model and the experimental results for inter-transceiver distances less than 55 cm. These results demonstrated a viable new approach for distributed sensing and monitoring of subsurface hazards for civil infrastructure within a networked domain of radio transceivers.

ON THE BRIGHTNESS AND WAITING-TIME DISTRIBUTIONS OF A TYPE III RADIO STORM OBSERVED BY STEREO/WAVES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eastwood, J. P.; Hudson, H. S.; Krucker, S.

2010-01-10

Type III solar radio storms, observed at frequencies below {approx}16 MHz by space-borne radio experiments, correspond to the quasi-continuous, bursty emission of electron beams onto open field lines above active regions. The mechanisms by which a storm can persist in some cases for more than a solar rotation whilst exhibiting considerable radio activity are poorly understood. To address this issue, the statistical properties of a type III storm observed by the STEREO/WAVES radio experiment are presented, examining both the brightness distribution and (for the first time) the waiting-time distribution (WTD). Single power-law behavior is observed in the number distribution asmore » a function of brightness; the power-law index is {approx}2.1 and is largely independent of frequency. The WTD is found to be consistent with a piecewise-constant Poisson process. This indicates that during the storm individual type III bursts occur independently and suggests that the storm dynamics are consistent with avalanche-type behavior in the underlying active region.« less

Nanotube resonator devices

DOEpatents

Jensen, Kenneth J; Zettl, Alexander K; Weldon, Jeffrey A

2014-05-06

A fully-functional radio receiver fabricated from a single nanotube is being disclosed. Simultaneously, a single nanotube can perform the functions of all major components of a radio: antenna, tunable band-pass filter, amplifier, and demodulator. A DC voltage source, as supplied by a battery, can power the radio. Using carrier waves in the commercially relevant 40-400 MHz range and both frequency and amplitude modulation techniques, successful music and voice reception has been demonstrated. Also disclosed are a radio transmitter and a mass sensor using a nanotube resonator device.

Instrument For Simulation Of Piezoelectric Transducers

NASA Technical Reports Server (NTRS)

Mcnichol, Randal S.

1996-01-01

Electronic instrument designed to simulate dynamic output of integrated-circuit piezoelectric acceleration or pressure transducer. Operates in conjunction with external signal-conditioning circuit, generating square-wave signal of known amplitude for use in calibrating signal-conditioning circuit. Instrument also useful as special-purpose square-wave generator in other applications.

Overview of Solar Radio Bursts and their Sources

NASA Astrophysics Data System (ADS)

Golla, Thejappa; MacDowall, Robert J.

2018-06-01

Properties of radio bursts emitted by the Sun at frequencies below tens of MHz are reviewed. In this frequency range, the most prominent radio emissions are those of solar type II, complex type III and solar type IV radio bursts, excited probably by the energetic electron populations accelerated in completely different environments: (1) type II bursts are due to non-relativistic electrons accelerated by the CME driven interplanetary shocks, (2) complex type III bursts are due to near-relativistic electrons accelerated either by the solar flare reconnection process or by the SEP shocks, and (3) type IV bursts are due to relativistic electrons, trapped in the post-eruption arcades behind CMEs; these relativistic electrons probably are accelerated by the continued reconnection processes occurring beneath the CME. These radio bursts, which can serve as the natural plasma probes traversing the heliosphere by providing information about various crucial space plasma parameters, are also an ideal instrument for investigating acceleration mechanisms responsible for the high energy particles. The rich collection of valuable high quality radio and high time resolution in situ wave data from the WAVES experiments of the STEREO A, STEREO B and WIND spacecraft has provided an unique opportunity to study these different radio phenomena and understand the complex physics behind their excitation. We have developed Monte Carlo simulation techniques to estimate the propagation effects on the observed characteristics of these low frequency radio bursts. We will present some of the new results and describe how one can use these radio burst observations for space weather studies. We will also describe some of the non-linear plasma processes detected in the source regions of both solar type III and type II radio bursts. The analysis and simulation techniques used in these studies will be of immense use for future space based radio observations.

47 CFR 5.51 - Eligibility of license.

Code of Federal Regulations, 2010 CFR

2010-10-01

... Radio Service will be issued only to persons qualified to conduct experimentation utilizing radio waves... rules; or for communications in connection with research projects when existing communications... service shall file applications and conduct such projects under the developmental rules of the established...

Electro-opto-mechanical radio-frequency oscillator driven by guided acoustic waves in standard single-mode fiber

NASA Astrophysics Data System (ADS)

London, Yosef; Diamandi, Hilel Hagai; Zadok, Avi

2017-04-01

An opto-electronic radio-frequency oscillator that is based on forward scattering by the guided acoustic modes of a standard single-mode optical fiber is proposed and demonstrated. An optical pump wave is used to stimulate narrowband, resonant guided acoustic modes, which introduce phase modulation to a co-propagating optical probe wave. The phase modulation is converted to an intensity signal at the output of a Sagnac interferometer loop. The intensity waveform is detected, amplified, and driven back to modulate the optical pump. Oscillations are achieved at a frequency of 319 MHz, which matches the resonance of the acoustic mode that provides the largest phase modulation of the probe wave. Oscillations at the frequencies of competing acoustic modes are suppressed by at least 40 dB. The linewidth of the acoustic resonance is sufficiently narrow to provide oscillations at a single longitudinal mode of the hybrid cavity. Competing longitudinal modes are suppressed by at least 38 dB as well. Unlike other opto-electronic oscillators, no radio-frequency filtering is required within the hybrid cavity. The frequency of oscillations is entirely determined by the fiber opto-mechanics.

Nonlinear, relativistic Langmuir waves in astrophysical magnetospheres

NASA Technical Reports Server (NTRS)

Chian, Abraham C.-L.

1987-01-01

Large amplitude, electrostatic plasma waves are relevant to physical processes occurring in the astrophysical magnetospheres wherein charged particles are accelerated to relativistic energies by strong waves emitted by pulsars, quasars, or radio galaxies. The nonlinear, relativistic theory of traveling Langmuir waves in a cold plasma is reviewed. The cases of streaming electron plasma, electronic plasma, and two-streams are discussed.

View of Soviet ionospheric modification research

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duncan, L.M.; Showen, R.L.

1990-10-01

We have reviewed and provided a technical assessment of Soviet research of the past five to ten years in ionospheric modification by high-power radio waves. This review includes a comprehensive survey of Soviet published literature, conference proceedings, and direct discussions with the involved Soviet researchers. The current state of the art for Soviet research in this field is evaluated, identifying areas of potential breakthrough discoveries, and discussing implications of this work for emerging technologies and future applications. This assessment is divided into the categories of basic research, advanced research, and applications. Basic research is further subdivided into studies of themore » modified natural geophysical environment, nonlinear plasma physics, and polar geophysical studies. Advanced research topics include the generation of artificial ionization mirrors and high-power oblique propagation effects. A separate comparative assessment of Soviet theoretical work also is included in this analysis. Our evaluation of practical and potential applications of this research discusses the utility of ionospheric modification in creating disturbed radio wave propagation environments, and its role in current and future remote-sensing and telecommunications systems. This technical assessment does not include consideration of ionospheric modification by means other than high-power radio waves. The Soviet effort in ionospheric modification sustains theoretical and experimental research at activity levels considerably greater than that found in comparable programs in the West. Notable strengths of the Soviet program are its breadth of coverage, large numbers of scientific participation, theoretical creativity and insight, and its powerful radio wave transmitting facilities.« less

Programming an Artificial Neural Network Tool for Spatial Interpolation in GIS - A Case Study for Indoor Radio Wave Propagation of WLAN.

PubMed

Sen, Alper; Gümüsay, M Umit; Kavas, Aktül; Bulucu, Umut

2008-09-25

Wireless communication networks offer subscribers the possibilities of free mobility and access to information anywhere at any time. Therefore, electromagnetic coverage calculations are important for wireless mobile communication systems, especially in Wireless Local Area Networks (WLANs). Before any propagation computation is performed, modeling of indoor radio wave propagation needs accurate geographical information in order to avoid the interruption of data transmissions. Geographic Information Systems (GIS) and spatial interpolation techniques are very efficient for performing indoor radio wave propagation modeling. This paper describes the spatial interpolation of electromagnetic field measurements using a feed-forward back-propagation neural network programmed as a tool in GIS. The accuracy of Artificial Neural Networks (ANN) and geostatistical Kriging were compared by adjusting procedures. The feedforward back-propagation ANN provides adequate accuracy for spatial interpolation, but the predictions of Kriging interpolation are more accurate than the selected ANN. The proposed GIS ensures indoor radio wave propagation model and electromagnetic coverage, the number, position and transmitter power of access points and electromagnetic radiation level. Pollution analysis in a given propagation environment was done and it was demonstrated that WLAN (2.4 GHz) electromagnetic coverage does not lead to any electromagnetic pollution due to the low power levels used. Example interpolated electromagnetic field values for WLAN system in a building of Yildiz Technical University, Turkey, were generated using the selected network architectures to illustrate the results with an ANN.

High-frequency (13.56-MHz) and ultrahigh-frequency (915-MHz) radio identification systems do not affect platelet activation and functions.

PubMed

Rogowska, Anna; Chabowska, Anna Małgorzata; Lipska, Alina; Boczkowska-Radziwon, Barbara; Bujno, Magdalena; Rusak, Tomasz; Dziemianczuk, Mateusz; Radziwon, Piotr

2016-05-01

In radiofrequency identification (RFID) systems used in labeling of blood components, blood cells are subjected to the direct influence of electromagnetic waves throughout the storage period. The aim of this study was to prove the safety of storage of platelet concentrates (PCs) in containers labeled with RFID tags. Ten pooled PCs obtained from 12 buffy coats each suspended in additive solution were divided into three separate containers that were assigned to three groups: control, PCs labeled with ultrahigh frequency (UHF) range tags and exposed to 915-MHz radio waves, and PCs labeled with high-frequency (HF) range tags and exposed to 13.56-MHz radio waves. PCs were stored at 20 to 24°C for 7 days. In vitro tests of platelet (PLT) function were performed on the first, fifth, and seventh days of storage. There were no significant differences in pH; hypotonic shock resistance; surface expression of CD62P, CD42a, or CD63; release of PLT-derived microparticles; PLT aggregation; and number of PLTs between PCs stored at a constant exposure to radio waves of two different frequencies and the control group on the first, fifth, and seventh days of storage. The results of the study indicate no impact of electromagnetic radiation generated in HF and UHF RFID systems and constant contact with the tags on the quality of stored PCs. © 2016 AABB.

Programming an Artificial Neural Network Tool for Spatial Interpolation in GIS - A Case Study for Indoor Radio Wave Propagation of WLAN

PubMed Central

Şen, Alper; Gümüşay, M. Ümit; Kavas, Aktül; Bulucu, Umut

2008-01-01

Wireless communication networks offer subscribers the possibilities of free mobility and access to information anywhere at any time. Therefore, electromagnetic coverage calculations are important for wireless mobile communication systems, especially in Wireless Local Area Networks (WLANs). Before any propagation computation is performed, modeling of indoor radio wave propagation needs accurate geographical information in order to avoid the interruption of data transmissions. Geographic Information Systems (GIS) and spatial interpolation techniques are very efficient for performing indoor radio wave propagation modeling. This paper describes the spatial interpolation of electromagnetic field measurements using a feed-forward back-propagation neural network programmed as a tool in GIS. The accuracy of Artificial Neural Networks (ANN) and geostatistical Kriging were compared by adjusting procedures. The feedforward back-propagation ANN provides adequate accuracy for spatial interpolation, but the predictions of Kriging interpolation are more accurate than the selected ANN. The proposed GIS ensures indoor radio wave propagation model and electromagnetic coverage, the number, position and transmitter power of access points and electromagnetic radiation level. Pollution analysis in a given propagation environment was done and it was demonstrated that WLAN (2.4 GHz) electromagnetic coverage does not lead to any electromagnetic pollution due to the low power levels used. Example interpolated electromagnetic field values for WLAN system in a building of Yildiz Technical University, Turkey, were generated using the selected network architectures to illustrate the results with an ANN. PMID:27873854

An Enhanced Method for Scheduling Observations of Large Sky Error Regions for Finding Optical Counterparts to Transients

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rana, Javed; Singhal, Akshat; Gadre, Bhooshan

2017-04-01

The discovery and subsequent study of optical counterparts to transient sources is crucial for their complete astrophysical understanding. Various gamma-ray burst (GRB) detectors, and more notably the ground-based gravitational wave detectors, typically have large uncertainties in the sky positions of detected sources. Searching these large sky regions spanning hundreds of square degrees is a formidable challenge for most ground-based optical telescopes, which can usually image less than tens of square degrees of the sky in a single night. We present algorithms for better scheduling of such follow-up observations in order to maximize the probability of imaging the optical counterpart, basedmore » on the all-sky probability distribution of the source position. We incorporate realistic observing constraints such as the diurnal cycle, telescope pointing limitations, available observing time, and the rising/setting of the target at the observatory’s location. We use simulations to demonstrate that our proposed algorithms outperform the default greedy observing schedule used by many observatories. Our algorithms are applicable for follow-up of other transient sources with large positional uncertainties, such as Fermi -detected GRBs, and can easily be adapted for scheduling radio or space-based X-ray follow-up.« less

The Australian SKA Pathfinder: project update and initial operations

NASA Astrophysics Data System (ADS)

Schinckel, Antony E. T.; Bock, Douglas C.-J.

2016-08-01

The Australian Square Kilometre Array Pathfinder (ASKAP) will be the fastest dedicated cm-wave survey telescope, and will consist of 36 12-meter 3-axis antennas, each with a large chequerboard phased array feed (PAF) receiver operating between 0.7 and 1.8 GHz, and digital beamforming prior to correlation. The large raw data rates involved ( 100 Tb/sec), and the need to do pipeline processing, has led to the antenna incorporating a third axis to fix the parallactic angle with respect to the entire optical system (blockages and phased array feed). It also results in innovative technical solutions to the data transport and processing issues. ASKAP is located at the Murchison Radio-astronomy Observatory (MRO), a new observatory developed for the Square Kilometre Array (SKA), 315 kilometres north-east of Geraldton, Western Australia. The MRO also hosts the SKA low frequency pathfinder instrument, the Murchison Widefield Array and will host the initial low frequency instrument of the SKA, SKA1-Low. Commissioning of ASKAP using six antennas equipped with first-generation PAFs is now complete and installation of second-generation PAFs and digital systems is underway. In this paper we review technical progress and commissioning to date, and refer the reader to relevant technical and scientific publications.

Investigation of Ionospheric Turbulence and Whistler Wave Interactions with Space Plasmas

DTIC Science & Technology

2012-11-21

an oscillating LOS velocity with the same periodicity as the heating modulation pattern. A set of Fourier periodogram from the MUIR LOS velocity...scale ionospheric turbulence are discussed separately, viz., (a) anomalous heat source-induced acoustic gravity waves (AGW), and (b) HF radio wave...ionospheric ducts, acoustic gravity waves (AGWs), anomalous heat sources, inner and outer radiation belts, L parameter, whistler wave interactions

On Spatial Structuring of the F2 Layer Studied by the Satellite Radio Sounding of the Ionosphere Disturbed by High-Power HF Radio Waves

NASA Astrophysics Data System (ADS)

Tereshchenko, E. D.; Turyansky, V. A.; Khudukon, B. Z.; Yurik, R. Yu.; Frolov, V. L.

2018-01-01

We present the results of studying the characteristics of the artificial plasma structures excited in the ionospheric F2 region modified by high-power HF radio waves. The experiments were carried out at the Sura heating facility using satellite radio sounding of the ionosphere. The plasma density profile was reconstructed with the highest possible spatial resolution for today, about 4 km. In a direction close to the magnetic zenith of the pump wave, the following phenomena were observed: the formation of a cavity with a 15% lower plasma density at the altitudes of the F2 layer and below; the formation of an area with plasma density increased by 12% at altitudes greater than 400 km. With a long-term quasiperiodic impact of the pump wave on the ionosphere, wavy large-scale electron-density perturbations (the meridional scale λx ≈ 130 km and the vertical scale λz ≈ 440 km) are also formed above the Sura facility. These perturbations can be due to the plasma density modulation by an artificial acoustic-gravity wave with a period of 10.6 m, which was formed by the heat source inside a large-scale cavity with low plasma density; there is generation of the electron density irregularities for the electrons with ΔNe/Ne ≈ 3% in the form of layers having the sizes 10-12 km along and about 24 km across the geomagnetic field, which are found both below and above the F2-layer maximum. The mechanisms of the formation of these plasma structures are discussed.

Frequency correlation of probe waves backscattered from small scale ionospheric irregularities generated by high power HF radio waves

NASA Astrophysics Data System (ADS)

Puchkov, V. A.

2016-09-01

Aspect sensitive scattering of multi-frequency probe signals by artificial, magnetic field aligned density irregularities (with transverse size ∼ 1- 10 m) generated in the ionosphere by powerful radio waves is considered. Fluctuations of received signals depending on stochastic properties of the irregularities are calculated. It is shown that in the case of HF probe waves two mechanisms may contribute to the scattered signal fluctuations. The first one is due to the propagation of probe waves in the ionospheric plasma as in a randomly inhomogeneous medium. The second one lies in non-stationary stochastic behavior of irregularities which satisfy the Bragg conditions for the scattering geometry and therefore constitute centers of scattering. In the probe wave frequency band of the order of 10-100 MHz the second mechanism dominates which delivers opportunity to recover some properties of artificial irregularities from received signals. Correlation function of backscattered probe waves with close frequencies is calculated, and it is shown that detailed spatial distribution of irregularities along the scattering vector can be found experimentally from observations of this correlation function.

Two-Way Radio in Schools (or, The Loneliness of the Long Distance Learner). An Evaluation of a High Frequency Short Wave, Two-Way Radio Trial.

ERIC Educational Resources Information Center

Conboy, Ian

The Country Education Project in Victoria, Australia, tested the use of two-way radios to bring educational resources to isolated children studying correspondence courses in small rural high schools and to increase interaction among rural schools. Eight rural Victoria schools and the Secondary Correspondence School in Melbourne used two-way…

The Role of the Goldstone Apple Valley Radio Telescope Project in Promoting Scientific Efficacy among Middle and High School Students.

ERIC Educational Resources Information Center

Ibe, Mary; Deutscher, Rebecca

This study investigated the effects on student scientific efficacy after participation in the Goldstone Apple Valley Radio Telescope (GAVRT) project. In the GAVRT program, students use computers to record extremely faint radio waves collected by the telescope and analyze real data. Scientific efficacy is a type of self-knowledge a person uses to…

Wave refraction diagrams for the Baltimore Canyon region of the mid-Atlantic continental shelf computed by using three bottom topography approximation techniques

NASA Technical Reports Server (NTRS)

Poole, L. R.

1976-01-01

The Langley Research Center and Virginia Institute of Marine Science wave refraction computer model was applied to the Baltimore Canyon region of the mid-Atlantic continental shelf. Wave refraction diagrams for a wide range of normally expected wave periods and directions were computed by using three bottom topography approximation techniques: quadratic least squares, cubic least squares, and constrained bicubic interpolation. Mathematical or physical interpretation of certain features appearing in the computed diagrams is discussed.

A passive low frequency instrument for radio wave sounding the subsurface oceans of the Jovian icy moons: An instrument concept

NASA Astrophysics Data System (ADS)

Hartogh, P.; Ilyushin, Ya. A.

2016-10-01

Exploration of subsurface oceans on Jovian icy moons is a key issue of the icy moons' geology. Electromagnetic wave propagation is the only way to probe their icy mantles from the orbit. In the present paper, a principal concept of a passive interferometric instrument for deep sounding of the icy moons' crust is proposed. Its working principle is measuring and correlating Jupiter's radio wave emissions with reflections from the deep sub-surface of the icy moons. A number of the functional aspects of the proposed experiment are studied, in particular, impact of the wave scattering on the surface terrain on the instrument performance and digital sampling of the noisy signal. Results of the test of the laboratory prototype of the instrument are also presented in the paper.

Measuring ionospheric movements using totally reflected radio waves

NASA Astrophysics Data System (ADS)

Sadler, Elaine M.; Whitehead, J. D.; From, W. R.

1988-02-01

It is shown that for radio waves of a particular frequency reflected totally from the ionosphere the effect of refraction as well as reflection can be simulated by an effective reflecting surface. This mirror-like surface will give the correct angle of arrival and Doppler shift for all radars operating at this frequency. It is theoretically possible for the effective reflecting surface to be folded back on itself, but this is unlikely except for F-region echoes refracted by sporadic E-clouds. If the surface is not folded and exists everywhere, it is always possible to describe its motion and change in terms of wave undulations. Experimental data for F-region echoes show that these wave undulations are very dispersive. However, the matching between the best fitting model and the experimental data is worse than expected for reasons we do not understand.

Measuring ionospheric movements using totally reflected radio waves

NASA Astrophysics Data System (ADS)

From, W. R.; Sadler, Elaine M.; Whitehead, J. D.

1988-02-01

It is shown that for radio waves of a particular frequency reflected totally from the ionosphere the effect of refraction as well as reflection can be simulated by an effective reflecting surface. This mirrorlike surface will give the correct angle of arrival and Doppler shift for all radars operating at this frequency. It is theoretically possible for the effective reflecting surface to be folded back on itself, but this is unlikely except for F-region echoes refracted by sporadic E-clouds. If the surface is not folded and exists everywhere, it is always possible to describe its motion and change in terms of wave undulations. Experimental data for F-region echoes show that these wave undulations are very dispersive. However, the matching between the best fitting model and the experimental data is worse than expected for reasons we do not understand.

MMS Observations of Langmuir Collapse and Emission?

NASA Astrophysics Data System (ADS)

Boardsen, S. A.; Che, H.; Wilder, F. D.; Ergun, R.; Le Contel, O.; Gershman, D. J.; Giles, B. L.; Moore, T. E.; Paterson, W.

2017-12-01

Through the two stream instability, electron beams accelerated by solar flares and nanoflares are believed to be responsible for several types of solar radio bursts observed in the corona and interplanetary medium, including flare-associated coronal Type J, U, and Type III radio bursts, and nanoflare-associated weak coronal type III bursts. However the duration of these radio bursts is several orders of magnitude longer than the linear saturation time of the electron two-stream instability. This discrepancy has been a long-standing puzzle. Recently Che et al. [2017, doi: 10.1073/pnas.1614055114] proposed a mechanism in which the plasma coherent emission is maintained by the cyclic Langmuir collapse. Wave coupling between Langmuir waves and electrostatic whistler waves is the key process necessary to close the feedback loop. In the magnetosphere, electron beams are commonly produced by acceleration processes such as magnetic reconnection, during which both whistlers and Langmuir waves are observed and thus provide possible in-situ observations to test and study the emission process near the acceleration source region. The high spatial and time resolution MMS fields and particle data are used to test aspects of this mechanism. In this presentation, we will present some preliminary results from MMS observations of electron beams near a reconnection region. We investigate, in the regions where the electron beams are observed, the coupling between high frequency Langmuir waves and low frequency electrostatic whistler waves, and the associated electromagnetic emissions, along with other possible specific features predicted by this model.

Phase modulation for reduced vibration sensitivity in laser-cooled clocks in space

NASA Technical Reports Server (NTRS)

Klipstein, W.; Dick, G.; Jefferts, S.; Walls, F.

2001-01-01

The standard interrogation technique in atomic beam clocks is square-wave frequency modulation (SWFM), which suffers a first order sensitivity to vibrations as changes in the transit time of the atoms translates to perceived frequency errors. Square-wave phase modulation (SWPM) interrogation eliminates sensitivity to this noise.

Milliwatt dc/dc Inverter

NASA Technical Reports Server (NTRS)

Mclyman, C. W.

1983-01-01

Compact dc/dc inverter uses single integrated-circuit package containing six inverter gates that generate and amplify 100-kHz square-wave switching signal. Square-wave switching inverts 10-volt local power to isolated voltage at another desired level. Relatively high operating frequency reduces size of filter capacitors required, resulting in small package unit.

Radio telescope search for the resonant conversion of cold dark matter axions from the magnetized astrophysical sources

NASA Astrophysics Data System (ADS)

Huang, Fa Peng; Kadota, Kenji; Sekiguchi, Toyokazu; Tashiro, Hiroyuki

2018-06-01

We study the conditions for the adiabatic resonant conversion of the cold dark matter (CDM) axions into photons in the astrophysically sourced strong magnetic fields such as those in the neutron star magnetosphere. We demonstrate the possibility that the forthcoming radio telescopes such as the SKA (Square Kilometre Array) can probe those photon signals from the CDM axions.

47 CFR 73.681 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-10-01

... in a given direction relative to an isotropic antenna. Field. Scanning through the picture area once... strength. The field strength that would exist at a point in the absence of waves reflected from the earth... Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES...

47 CFR 73.681 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-10-01

... in a given direction relative to an isotropic antenna. Field. Scanning through the picture area once... strength. The field strength that would exist at a point in the absence of waves reflected from the earth... Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES...

47 CFR 73.681 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-10-01

... in a given direction relative to an isotropic antenna. Field. Scanning through the picture area once... strength. The field strength that would exist at a point in the absence of waves reflected from the earth... Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES...

47 CFR 73.681 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-10-01

... in a given direction relative to an isotropic antenna. Field. Scanning through the picture area once... strength. The field strength that would exist at a point in the absence of waves reflected from the earth... Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES...

Clusters of Galaxies and the Cosmic Web with Square Kilometre Array

NASA Astrophysics Data System (ADS)

Kale, Ruta; Dwarakanath, K. S.; Vir Lal, Dharam; Bagchi, Joydeep; Paul, Surajit; Malu, Siddharth; Datta, Abhirup; Parekh, Viral; Sharma, Prateek; Pandey-Pommier, Mamta

2016-12-01

The intra-cluster and inter-galactic media that pervade the large scale structure of the Universe are known to be magnetized at sub-micro Gauss to micro Gauss levels and to contain cosmic rays. The acceleration of cosmic rays and their evolution along with that of magnetic fields in these media is still not well understood. Diffuse radio sources of synchrotron origin associated with the Intra-Cluster Medium (ICM) such as radio halos, relics and mini-halos are direct probes of the underlying mechanisms of cosmic ray acceleration. Observations with radio telescopes such as the Giant Metrewave Radio Telescope, the Very Large Array and the Westerbork Synthesis Radio Telescope have led to the discoveries of about 80 such sources and allowed detailed studies in the frequency range 0.15-1.4 GHz of a few. These studies have revealed scaling relations between the thermal and non-thermal properties of clusters and favour the role of shocks in the formation of radio relics and of turbulent re-acceleration in the formation of radio halos and mini-halos. The radio halos are known to occur in merging clusters and mini-halos are detected in about half of the cool-core clusters. Due to the limitations of current radio telescopes, low mass galaxy clusters and galaxy groups remain unexplored as they are expected to contain much weaker radio sources. Distinguishing between the primary and the secondary models of cosmic ray acceleration mechanisms requires spectral measurements over a wide range of radio frequencies and with high sensitivity. Simulations have also predicted weak diffuse radio sources associated with filaments connecting galaxy clusters. The Square Kilometre Array (SKA) is a next generation radio telescope that will operate in the frequency range of 0.05-20 GHz with unprecedented sensitivities and resolutions. The expected detection limits of SKA will reveal a few hundred to thousand new radio halos, relics and mini-halos providing the first large and comprehensive samples for their study. The wide frequency coverage along with sensitivity to extended structures will be able to constrain the cosmic ray acceleration mechanisms. The higher frequency (>5 GHz) observations will be able to use the Sunyaev-Zel'dovich effect to probe the ICM pressure in addition to tracers such as lobes of head-tail radio sources. The SKA also opens prospects to detect the `off-state' or the lowest level of radio emission from the ICM predicted by the hadronic models and the turbulent re-acceleration models.

Demonstration of a viable quantitative theory for interplanetary type II radio bursts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schmidt, J. M., E-mail: jschmidt@physics.usyd.edu.au; Cairns, Iver H.

Between 29 November and 1 December 2013 the two widely separated spacecraft STEREO A and B observed a long lasting, intermittent, type II radio burst for the extended frequency range ≈ 4 MHz to 30 kHz, including an intensification when the shock wave of the associated coronal mass ejection (CME) reached STEREO A. We demonstrate for the first time our ability to quantitatively and accurately simulate the fundamental (F) and harmonic (H) emission of type II bursts from the higher corona (near 11 solar radii) to 1 AU. Our modeling requires the combination of data-driven three-dimensional magnetohydrodynamic simulations for the CME andmore » plasma background, carried out with the BATS-R-US code, with an analytic quantitative kinetic model for both F and H radio emission, including the electron reflection at the shock, growth of Langmuir waves and radio waves, and the radiations propagation to an arbitrary observer. The intensities and frequencies of the observed radio emissions vary hugely by factors ≈ 10{sup 6} and ≈ 10{sup 3}, respectively; the theoretical predictions are impressively accurate, being typically in error by less than a factor of 10 and 20 %, for both STEREO A and B. We also obtain accurate predictions for the timing and characteristics of the shock and local radio onsets at STEREO A, the lack of such onsets at STEREO B, and the z-component of the magnetic field at STEREO A ahead of the shock, and in the sheath. Very strong support is provided by these multiple agreements for the theory, the efficacy of the BATS-R-US code, and the vision of using type IIs and associated data-theory iterations to predict whether a CME will impact Earth’s magnetosphere and drive space weather events.« less

Demonstration of a viable quantitative theory for interplanetary type II radio bursts

NASA Astrophysics Data System (ADS)

Schmidt, J. M.; Cairns, Iver H.

2016-03-01

Between 29 November and 1 December 2013 the two widely separated spacecraft STEREO A and B observed a long lasting, intermittent, type II radio burst for the extended frequency range ≈ 4 MHz to 30 kHz, including an intensification when the shock wave of the associated coronal mass ejection (CME) reached STEREO A. We demonstrate for the first time our ability to quantitatively and accurately simulate the fundamental (F) and harmonic (H) emission of type II bursts from the higher corona (near 11 solar radii) to 1 AU. Our modeling requires the combination of data-driven three-dimensional magnetohydrodynamic simulations for the CME and plasma background, carried out with the BATS-R-US code, with an analytic quantitative kinetic model for both F and H radio emission, including the electron reflection at the shock, growth of Langmuir waves and radio waves, and the radiations propagation to an arbitrary observer. The intensities and frequencies of the observed radio emissions vary hugely by factors ≈ 106 and ≈ 103, respectively; the theoretical predictions are impressively accurate, being typically in error by less than a factor of 10 and 20 %, for both STEREO A and B. We also obtain accurate predictions for the timing and characteristics of the shock and local radio onsets at STEREO A, the lack of such onsets at STEREO B, and the z-component of the magnetic field at STEREO A ahead of the shock, and in the sheath. Very strong support is provided by these multiple agreements for the theory, the efficacy of the BATS-R-US code, and the vision of using type IIs and associated data-theory iterations to predict whether a CME will impact Earth's magnetosphere and drive space weather events.

Science with a lunar low-frequency array: From the dark ages of the Universe to nearby exoplanets

NASA Astrophysics Data System (ADS)

Jester, Sebastian; Falcke, Heino

2009-05-01

Low-frequency radio astronomy is limited by severe ionospheric distortions below 50 MHz and complete reflection of radio waves below 10-30 MHz. Shielding of man-made interference from long-range radio broadcasts, strong natural radio emission from the Earth's aurora, and the opportunity to set up a large distributed antenna array make the lunar far side a supreme location for a low-frequency radio array. A number of new scientific drivers for such an array, such as the study of the dark ages and epoch of reionization, exoplanets, and ultra-high energy cosmic rays, have emerged and need to be studied in greater detail. Here we review the scientific potential and requirements of these new scientific drivers and discuss the constraints for various lunar surface arrays. In particular, we describe observability constraints imposed by the interstellar and interplanetary medium, calculate the achievable resolution, sensitivity, and confusion limit of a dipole array using general scaling laws, and apply them to various scientific questions. Of particular interest for a lunar array are studies of the earliest phase of the universe which are not easily accessible by other means. These are the epoch of reionization at redshifts z = 6-20, during which the very first stars and galaxies ionized most of the originally neutral intergalactic hydrogen, and the dark ages prior to that. For example, a global 21-cm wave absorption signature from primordial hydrogen in the dark ages at z = 30-50 could in principle be detected by a single dipole in an eternally dark crater on the moon, but foreground subtraction would be extremely difficult. Obtaining a high-quality power spectrum of density fluctuations in the epoch of reionization at z = 6-20, providing a wealth of cosmological data, would require about 103-105 antenna elements on the moon, which appears not unreasonable in the long term. Moreover, baryonic acoustic oscillations in the dark ages at z = 30-50 could similarly be detected, thereby providing pristine cosmological information, e.g., on the inflationary phase of the universe. With a large array also exoplanet magnetospheres could be detected through Jupiter-like coherent bursts. Smaller arrays of order 102 antennas over ˜100 km, which could already be erected robotically by a single mission with current technology and launchers, could tackle surveys of steep-spectrum large-scale radio structures from galaxy clusters and radio galaxies. Also, at very low frequencies the structure of the interstellar medium can be studied tomographically. Moreover, radio emission from neutrino interactions within the moon can potentially be used to create a neutrino detector with a volume of several cubic kilometers. An ultra-high energy cosmic ray detector with thousands of square kilometer area for cosmic ray energies >1020eV could in principle be realized with some hundred antennas. In any case, pathfinder arrays are needed to test the feasibility of these experiments in the not too distant future. Lunar low-frequency arrays are thus a timely option to consider, offering the potential for significant new insights into a wide range of today's crucial scientific topics. This would open up one of the last unexplored frequency domains in the electromagnetic spectrum.

State Switching of the X-Ray/Radio Transitional Millisecond Pulsar

NASA Astrophysics Data System (ADS)

Shang, Lun-Hua; Zhang, Cheng-Min; Li, Di; Wang, De-Hua; Wang, Shuang-Qiang; Wang, Pei; Pan, Yuan-Yue; Yang, Yi-Yan; Zhi, Qi-Jun

2017-11-01

PSR J1023+0038 is a known transitional pulsar, which switches between the accretion-powered X-ray pulsar state and the rotation-powered radio millisecond pulsar (MSP) state. Here, we study the conditions for its state transition by ascribing ˜GHz radio pulse emission to the plasma cutoff oscillation frequency at the magnetosphere, which depends on the plasma density or accretion rate. With the accretion X-ray luminosity declining fromhigh to low state (e.g., ˜ {10}35 erg s-1 to ˜ {10}32 erg s-1), the magnetosphere boundary expands to the light cylinder, where the plasma density is low enough to permit the emission of radio waves at the several-GHz frequency band. Thus, for a sufficiently low accretion-rate state (˜ {10}32 erg s-1), the radio emission at the several-GHz band is not blocked by the plasma, and the radio pulsar can be detected in the favored “observational windows,” I.e., the L band (1-2 GHz), S band (2-4 GHz), and C band (4-8 GHz). Furthermore, to evaluate the penetration characteristics of the outgoing radio wave of low frequency, we calculate its skin depth, which is found to be a couple of centimeters for the low X-ray luminosity of {10}34{--}{10}32 erg s-1, a scale that is much shorter than the light cylinder radius of about 100 km for MSPs.

Architecture in outer space. [multilayer shell systems filled with gas

NASA Technical Reports Server (NTRS)

Pokrovskiy, G. I.

1974-01-01

Mulilayer thin film structures consisting of systems of shells filled with gas at some pressure are recommended for outer space structures: Large mirrors to collect light and radio waves, protection against meteoric impact and damage, and for connectors between state space stations in the form of orbital rings. It is projected that individual orbital rings will multiply and completely seal a star trapping its high temperature radiation and transforming it into low temperature infrared and short wave radio emission; this radiation energy could be utilized for technological and biological processes.

An Initial Critical Summary of Models for Predicting the Attenuation of Radio Waves by Trees

DTIC Science & Technology

1982-07-01

International Telecommunication Union, Geneva, Switzerland, 1978. 1 1Krevsky, S., "HF and VHF Radio Wave Attenuation Through Jungle and Woods ," IEEE...see Reference 7) summarized groups of measurements taken by Saxton, Trevor,𔃻 3 and IHoPetrie 1 4 in nontropical deciduous woods . In TABLE 1, the subset...a 0. 26 F0.77 (5) I ŕ 3Trevor, B., "Ultra-High-Frequency Propagation Through Woods and Underbrush," RCA Review, July 1940. 14%cPstrie, J.S. and

Initial report of the High Frequency Analyzer (HFA) onboard the ARASE (ERG) Satellite: Observations of the plasmasphere evolution and auroral kilometric radiation from the both hemisphere

NASA Astrophysics Data System (ADS)

Kumamoto, A.; Tsuchiya, F.; Kasahara, Y.; Kasaba, Y.; Kojima, H.; Yagitani, S.; Ishisaka, K.; Imachi, T.; Ozaki, M.; Matsuda, S.; Shoji, M.; Matsuoka, A.; Katoh, Y.; Miyoshi, Y.; Shinohara, I.; Obara, T.

2017-12-01

High Frequency Analyzer (HFA) is a subsystem of the Plasma Wave Experiment (PWE) onboard the ARASE (ERG, Exploration of energization and Radiation in Geospace) spacecraft for observation of radio and plasma waves in a frequency range from 0.01 to 10 MHz. In ARASE mission, HFA is expected to perform the following observations: (1) Upper hybrid resonance (UHR) waves in order to determine the electron number density around the spacecraft. (2) Magnetic field component of the chorus waves in a frequency range from 20 kHz to 100 kHz. (3) Radio and plasma waves excited via wave particle interactions and mode conversion processes in storm-time magnetosphere.HFA is operated in the following three observation modes: EE-mode, EB-mode, and PP-mode. In far-Earth region, HFA is operated in EE-mode. Spectrogram of two orthogonal or right and left-handed components of electric field in perpendicular directions to the spin axis of the spacecraft are obtained. In the near-Earth region, HFA is operated in EB-mode. Spectrogram of one components of electric field in perpendicular direction to the spin plane, and one component of the magnetic field in parallel direction to the spin axis are obtained. In EE and EB-modes, the frequency range from 0.01 to 10 MHz are covered with 480 frequency steps. The time resolution is 8 sec. We also prepared PP mode to measure the locations and structures of the plasmapause at higher resolution. In PP-mode, spectrogram of one electric field component in a frequency range from 0.01-0.4 MHz (PP1) or 0.1-1 MHz (PP2) can be obtained at time resolution of 1 sec.After the successful deployment of the wire antenna and search coils mast and initial checks, we could start routine observations and detect various radio and plasma wave phenomena such as upper hybrid resonance (UHR) waves, electrostatic electron cyclotron harmonic (ESCH) waves, auroral kilometric radiation (AKR), kilometric continuum (KC) and Type-III solar radio bursts. In the presentation, we will report the initial results based on the datasets obtained since January 2017 focusing on the analyses of plasmasphere evolution by semi-automatic identification of UHR frequency, and AKR from the both hemisphere based on polarization measurement.

Long-Range Transhorizon Lunar Surface Radio Wave Propagation in the Presence of a Regolith and a Sparse Exospheric Plasma

NASA Technical Reports Server (NTRS)

Manning, Robert M.

2008-01-01

Long-range, over-the-horizon (transhorizon) radio wave propagation is considered for the case of the Moon. In the event that relay satellites are not available or otherwise unwarranted for use, transhorizon communication provides for a contingency or backup option for non line-of-sight lunar surface exploration scenarios. Two potential low-frequency propagation mechanisms characteristic of the lunar landscape are the lunar regolith and the photoelectron induced plasma exosphere enveloping the Moon. Although it was hoped that the regolith would provide for a spherical waveguide which could support a trapped surface wave phenomena, it is found that, in most cases, the regolith is deleterious to long range radio wave propagation. However, the presence of the plasma of the lunar exosphere supports wave propagation and, in fact, surpasses the attenuation of the regolith. Given the models of the regolith and exosphere adopted here, it is recommended that a frequency of 1 MHz be considered for low rate data transmission along the lunar surface. It is also recommended that further research be done to capture the descriptive physics of the regolith and the exospheric plasma so that a more complete model can be obtained. This comprehensive theoretical study is based entirely on first principles and the mathematical techniques needed are developed as required; it is self-contained and should not require the use of outside resources for its understanding.

How Do Health Care Providers Diagnose Endometriosis?

MedlinePlus

... NICHD Research Information Find a Study More Information Pharmacology Condition Information NICHD Research Information Find a Study ... uses sound waves to make the picture, and magnetic resonance imaging (MRI) , which uses magnets and radio waves to ...

Direction of Radio Finding via MUSIC (Multiple Signal Classification) Algorithm for Hardware Design System

NASA Astrophysics Data System (ADS)

Zhang, Zheng

2017-10-01

Concept of radio direction finding systems, which use radio direction finding is based on digital signal processing algorithms. Thus, the radio direction finding system becomes capable to locate and track signals by the both. Performance of radio direction finding significantly depends on effectiveness of digital signal processing algorithms. The algorithm uses the Direction of Arrival (DOA) algorithms to estimate the number of incidents plane waves on the antenna array and their angle of incidence. This manuscript investigates implementation of the DOA algorithms (MUSIC) on the uniform linear array in the presence of white noise. The experiment results exhibit that MUSIC algorithm changed well with the radio direction.

RF stabilization of plasma instabilities: a note on physical mechanism

NASA Astrophysics Data System (ADS)

Sen, S.; Martinell, J.; Imadera, K.; Kishimoto, Y.; Vahala, G.

2018-02-01

In a series of recent works, we have developed models including realistic spatial profiles of both flow and radio-frequency-induced ponderomotive force. With these inclusions, the picture of stability of various plasma and fluid instabilities is expected to be changed drastically with ground-breaking consequences. The inhomogeneous parallel flow and the radio-frequency waves can actually stabilize turbulence. This is different from the prevalent notion that both parallel flow shear and radio-frequency waves are responsible for the excitation (destabilization) of plasma turbulence. This model thus aims to open-up new channels and provide a major breakthrough in our knowledge of plasma and fluid turbulence and its consequent roles in energy, space and processing technology. In this short note, we elucidate the physical mechanism behind this novel observation.

First Joint Observations of Radio Aurora by the VHF and HF Radars of the ISTP SB RAS

NASA Astrophysics Data System (ADS)

Berngardt, O. I.; Lebedev, V. P.; Kutelev, K. A.; Kushnarev, D. S.; Grkovich, K. V.

2018-01-01

Two modern radars for diagnosis of the ionosphere by the radio-wave backscattering method, namely, the Irkutsk incoherent scatter radar at VHF (IISR, 154-162 MHz) and the Ekaterinburg coherent radar at HF (EKB, 8-20 MHz) are operated at the Institute of Solar-Terrestrial Physics, Siberian Branch of the Russian Academy of Sciences (ISTP SB RAS). The paper analyzes the results of joint observations of strong scattering (radio aurora) on June 8, 2015. To determine the geographical position of the radio aurora, we developed original methods that take into account both the features of the radio-wave propagation and the features of the radar antenna systems. It is shown that there are areas where the spatial position of the HF and VHF radio aurora can coincide. This permits using the radars as a single complex for diagnosis of the characteristics of small-scale high-latitude irregularities in the ionospheric E and F layers. A comparative analysis of the characteristics and temporal dynamics of the radio-aurora region in the HF and VHF ranges is performed. Using the DMSP satellite data, it has been shown that the radio aurora dynamics during this experiment with the EKB radar can be related with the spatial dynamics of the localized area with high electric field, which moves from high to equatorial latitudes. It is found that due to the broader field of view, radio aurora at the HF radar was stably observed 6-12 min earlier than at the VHF radar. This permits using the EKB radar data for prediction of the radio-aurora detection by the IISR radar.

VLA Discovers Giant Rings Around Galaxy Cluster

NASA Astrophysics Data System (ADS)

2006-11-01

Astronomers using the National Science Foundation's Very Large Array (VLA) radio telescope have discovered giant, ring-like structures around a cluster of galaxies. The discovery provides tantalizing new information about how such galaxy clusters are assembled, about magnetic fields in the vast spaces between galaxy clusters, and possibly about the origin of cosmic rays. Radio-Optical Image of Cluster Galaxy Cluster Abell 3376 (Radio/Optical) CREDIT: Joydeep Bagchi, IUCAA, NRAO/AUI/NSF Above, a combined radio/optical image shows the galaxy cluster Abell 3376 in visible light (blue) and radio (red) images. The giant radio arcs surrounding the cluster were discovered using the Very Large Array. The visible-light image is from the Digitized Sky survey. Below, an X-ray image of Abell 3376 made using the European Space Agency's XMM-Newton telescope shows a spectacular, bullet-shaped region of X-rays coming from gas heated to 60 million degrees Kelvin. The bullet shape results from the supersonic collision of a smaller smaller galaxy subcluster with the main body of the larger cluster. Click on images for larger version. X-Ray Image of Cluster Galaxy Cluster Abell 3376 (X-Ray) CREDIT: Joydeep Bagchi, IUCAA, ESA "These giant, radio-emitting rings probably are the result of shock waves caused by violent collisions of smaller groups of galaxies within the cluster," said Joydeep Bagchi, of the Inter-University Centre for Astronomy and Astrophysics in Pune, India, who led an international research team. The scientists reported their findings in the November 3 edition of the journal Science. The newly-discovered ring segments, some 6 million light-years across, surround a galaxy cluster called Abell 3376, more than 600 million light-years from Earth. They were revealed because fast-moving electrons emitted radio waves as they spiraled around magnetic field lines in intergalactic space. "Even from this large distance, the feeble radio waves were easily picked up by the VLA, thanks to its very high sensitivity and unique capability to make images of exceedingly faint radio-emitting objects," Bagchi said. The scientists also used the European Space Agency's XMM-Newton, the world's most sensitive X-ray observatory, to observe this extraordinary cluster of galaxies. "The advanced technical capabilities of the orbiting XMM-Newton revealed a spectacular bullet-like region of X-ray emission in this dynamically active cluster," said Gastao B. Lima Neto, of the Institute of Astronomy and Geophysics in Sao Paulo, Brazil, a co-author of the research paper. "Our X-ray observations strongly suggest a recent collision and merger of two or more smaller clusters. Such a phenomenon is among the most energetic events in the Universe after the Big Bang. Only a tiny fraction of the total energy of this collision, if transferred to electrons, would cause them to emit the radio waves observed by the VLA. However, the main question is, how this is achieved," said Florence Durret of the Astrophysical Institute of Paris, France, another of the researchers. The scientists calculated that the total energy of the colliding groups of galaxies would be enough to keep our Sun shining for more than 20 sextillion years (2 followed by 22 zeros)! "We think the shock waves that sped up these electrons came from the collision of a smaller group of galaxies with the main body of the larger cluster. When two such massive objects crash into each other at supersonic speed, gigantic ripple-like shock waves are created in the surrounding gas, which race out to the outer regions of the forming cluster at a speed of thousands of kilometers per second," Bagchi said. "You can imagine that each cluster is like a supersonic aircraft, moving faster than the speed of sound in the surrounding gas, and just as you hear a sonic boom when shock waves from an airplane pass by you, we believe that the situation in the Abell 3376 cluster is similar, with ringlike radio structures tracing out the shock waves," Bagchi explained. Such a scenario also is supported by images of the cluster made with the XMM-Newton and ROSAT X-ray satellites, as well as by computer simulations, Bagchi added. The exact mechanism for producing the shock waves is still open to question, the scientists said. "This is the first observational evidence for this type of shock wave around a massive galaxy cluster," Bagchi said. "This discovery will help us understand more about the thin gas between the galaxies, and also about the magnetic fields in the outskirts of such clusters -- magnetic fields whose origin still is unknown," he said. In addition, the scientists speculate that violent regions like those in Abell 3376 may be sites from which cosmic rays originate. Cosmic rays are protons or atomic nuclei accelerated to nearly the speed of light, and shocks such as those found in the collisions of galaxy groups may be energetic enough to provide the required amount of "kick." "Some of the most energetic cosmic ray particles detected on Earth may contain about 100 million times more energy than the highest energy achieved so far in any man-made particle accelerator. Where do these cosmic rays come from and exactly what process kicks them to such stupendous energy is still a fascinating unsolved problem of physics," said graduate student Surajit Paul of the Institute for Theoretical Physics and Astrophysisc at Wuerzburg University in Germany, who was on the research team. "A cosmic accelerator source containing powerful shock waves and magnetic fields extending over millions of light years in length is capable of accelerating a proton or nucleus to such enormous energies. Although our observations do not conclusively show the evidence for such particles, our VLA radio image does show clearly that such structures are indeed present in this galaxy cluster. Only future cosmic ray observations can tell if Abell 3376 is an ultra-high-energy cosmic ray source. We will continue to explore this fascinating cosmic laboratory in the future, employing some of the world's most sensitive radio, X-ray and gamma-ray telescopes to reveal its mysteries," Bagchi said. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Architecture Analysis of Wireless Power Transmission for Lunar Outposts

DTIC Science & Technology

2015-09-01

through his work on wireless communication using radio wave propagation for both transmitting and receiving high frequency electricity using a focusing...Administration nm nanometers NRC National Research Council PGT platform generic technologies PMAD power management and distribution RF radio frequency xiv...GHz (Marzwell 2008). While the slot antenna can handle frequencies between 70 GHz and 150 GHz, it has been optimized for 94 GHz and has a radio

Meteor astronomy using a forward scatter set-up

NASA Astrophysics Data System (ADS)

Wislez, Jean-Marc

2006-08-01

An overview of the classical theory of the reflection of radio waves off meteor trails is given: the reflection conditions and mechanisms are discussed, and typical (t,A)-profiles of radio meteors are derived. Various configurations of the receive station(s) are proposed. The goal is to give the radio observer more insight in the possibilities, limitations and relevant parameters of forward scattering, and on how to obtain these through observations.

Jovian Space Weather in the Juno Era: Remote Observations

NASA Astrophysics Data System (ADS)

MacDowall, R. J.; Reiner, M. J.; Farrell, W. M.; Connerney, J. E. P.

2017-12-01

Jupiter is a large and rapidly rotating planet with a strong magnetic field, its magnetospheric dynamics only minimally influenced by the solar wind and interplanetary magnetic field (IMF). Yet, there are a number of manifestations of the Jovian magnetospheric interaction with elements of the solar wind and IMF. Variations in Jovian radio emissions are a prime example (Reiner et al. 2000, Zarka et al. 2004, Bose et al. 2008, Panchenko et al. 2012), as are auroral variations monitored in the infrared and ultraviolet.We present a review of the many journal papers that have examined the relationship between solar wind and IMF conditions (at the Jovian magnetosphere) and the Jovian radio burst variations and other associated phenomena.We present recent results from the joint observations by STEREO WAVES and WIND WAVES of Jovian radio emissions in the band of 1 - 15 MHz. The goal is to add a remote radio observation component to the determination of Jovian space weather, of particular use for data analysis by spacecraft orbiting the planet within the magnetosphere.

Laboratory evaluation and application of microwave absorption properties under simulated conditions for planetary atmospheres

NASA Technical Reports Server (NTRS)

Steffes, Paul G.

1988-01-01

In the first half of this grant year, laboratory measurements were conducted on the millimeter-wave properties of atmospheric gases under simulated conditions for the outer planet. Significant improvements in the current system have made it possible to accurately characterize the opacity from gaseous NH3 at longer millimeter wavelengths (7 to 10 mm) under simulated Jovian conditions. In the second half of the grant year, it is hoped to extend such measurements to even shorter millimeter-wavelengths. Further analysis and application of the laboratory results to microwave and millimeter-wave absorption data for the outer planets, such as results from Voyager Radio Occultation experiments and earth-based radio astronomical observations will be continued. The analysis of available multispectral microwave opacity data from Venus, including data from the most recent radio astronomical ovservations in the 1.3 to 3.6 cm wavelength range and newly obtained Pioneer-Venus Radio Occulatation measurements at 13 cm, using the laboratory measurements as an interpretative tool will be pursued.

High β effects on cosmic ray streaming in galaxy clusters

NASA Astrophysics Data System (ADS)

Wiener, Joshua; Zweibel, Ellen G.; Oh, S. Peng

2018-01-01

Diffuse, extended radio emission in galaxy clusters, commonly referred to as radio haloes, indicate the presence of high energy cosmic ray (CR) electrons and cluster-wide magnetic fields. We can predict from theory the expected surface brightness of a radio halo, given magnetic field and CR density profiles. Previous studies have shown that the nature of CR transport can radically effect the expected radio halo emission from clusters (Wiener, Oh & Guo 2013). Reasonable levels of magnetohydrodynamic (MHD) wave damping can lead to significant CR streaming speeds. But a careful treatment of MHD waves in a high β plasma, as expected in cluster environments, reveals damping rates may be enhanced by a factor of β1/2. This leads to faster CR streaming and lower surface brightnesses than without this effect. In this work, we re-examine the simplified, 1D Coma cluster simulations (with radial magnetic fields) of Wiener et al. (2013) and discuss observable consequences of this high β damping. Future work is required to study this effect in more realistic simulations.

Solar radio bursts of spectral type II, coronal shocks, and optical coronal transients

NASA Technical Reports Server (NTRS)

Maxwell, A.; Dryer, M.

1981-01-01

An examination is presented of the association of solar radio bursts of spectral type II and coronal shocks with solar flare ejecta observed in H-alpha, the green coronal line, and white-light coronagraphs. It is suggested that fast-moving optical coronal transients should for the most part be identified with piston-type phenomena well behind the outward-traveling shock waves that generate type II radio bursts. A general model is presented which relates type II radio bursts and coronal shocks to optically observed ejecta and consists of three main velocity regimes: (1) a quasi-hemispherical shock wave moving outward from the flare at speeds of 1000-2000 km/sec and Alfven Mach number of about 1.5; (2) the velocity of the piston driving the shock, on the order of 0.8 that of the shock; and (3) the regime of the slower-moving H-alpha ejecta, with velocities of 300-500 km/sec.

Radio observations of atmospheric gravity waves with Callisto

NASA Astrophysics Data System (ADS)

Monstein, C.

2013-12-01

On December 12th 2013 NOAA reported between 08:04 and 12:08 only radio noise at 245 MHz observed in San Vito. But some European observatories of the e-Callisto network (Germany, UK and Ireland) observed very strange reverse drifting and v-type bursts which was never recognized by the author before. Private communication with P. Zucca from TCD showed that these strange structures are due to focusing effects in the ionosphere. Interestingly it is possible to observe complex ionospheric behavior with cheap and simple radio-telescopes like Callisto. People who are interested in such kind of observations to study ionospheric gravity waves should generate observing programs for frequencies below 100 MHz, ideally with an additional up-converter for frequencies from 15 MHz - 100 MHz. Callisto again proved to be a powerful tool for solar science and radio-monitoring. Below are shown recent observations from Bir castle in Ireland, Essen in Germany and Glasgow in Scotland. For comparison I added an observation from a LOFAR node from Chibolton in UK which was provided by Richard Fallows from Astron NL. And finally a plot from Nançay radio heliograph, provided by Karl-Heinz Gansel, Dingden Amateur Radio- Astronomy Observatory DARO, Germany. Although Callisto instruments are almost identical, the spectra look completely different, depending on their geographical longitude and latitude.

The effect of plasma inhomogeneities on (i) radio emission generation by non-gyrotropic electron beams and (ii) particle acceleration by Langmuir waves

NASA Astrophysics Data System (ADS)

Tsiklauri, David

2015-04-01

Extensive particle-in-cell simulations of fast electron beams injected in a background magnetised plasma with a decreasing density profile were carried out. These simulations were intended to further shed light on a newly proposed mechanism for the generation of electromagnetic waves in type III solar radio bursts [1]. Here recent progress in an alternative to the plasma emission model using Particle-In-Cell, self-consistent electromagnetic wave emission simulations of solar type III radio bursts will be presented. In particular, (i) Fourier space drift (refraction) of non-gyrotropic electron beam-generated wave packets, caused by the density gradient [1,2], (ii) parameter space investigation of numerical runs [3], (iii) concurrent generation of whistler waves [4] and a separate problem of (iv) electron acceleration by Langmuir waves in a background magnetised plasma with an increasing density profile [5] will be discussed. In all considered cases the density inhomogeneity-induced wave refraction plays a crucial role. In the case of non-gyrotropic electron beam, the wave refraction transforms the generated wave packets from standing into freely escaping EM radiation. In the case of electron acceleration by Langmuir waves, a positive density gradient in the direction of wave propagation causes a decrease in the wavenumber, and hence a higher phase velocity vph = ω/k. The k-shifted wave is then subject to absorption by a faster electron by wave-particle interaction. The overall effect is an increased number of high energy electrons in the energy spectrum. [1] D. Tsiklauri, Phys. Plasmas 18, 052903 (2011); http://dx.doi.org/10.1063/1.3590928 [2] H. Schmitz, D. Tsiklauri, Phys. Plasmas 20, 062903 (2013); http://dx.doi.org/10.1063/1.4812453 [3] R. Pechhacker, D. Tsiklauri, Phys. Plasmas 19, 112903 (2012); http://dx.doi.org/10.1063/1.4768429 [4] M. Skender, D. Tsiklauri, Phys. Plasmas 21, 042904 (2014); http://dx.doi.org/10.1063/1.4871723 [5] R. Pechhacker, D. Tsiklauri, Phys. Plasmas 21, 012903 (2014); http://dx.doi.org/10.1063/1.4863494 This research is funded by the Leverhulme Trust Research Project Grant RPG-311

Cross-Shore Exchange on Natural Beaches

DTIC Science & Technology

2014-09-01

87   Figure 2.   Wave conditions measured by the ADCP in 13 m water depth of (a) root- mean-square wave height Hrms...horizontal velocity, Umean, measured in the reference level, ∑Tsig,pulse T3−hour ∑Tsig,pulse T3−hour xi (e) local water depth, h, and (f) local root...mean-square wave height normalized by the local water depth, Hrms/h, measured by ADCPin (blue) and ADCPout (red) during the 3HRLTs. Colored lines

A Statistical Analysis of the Solar Phenomena Associated with Global EUV Waves

NASA Astrophysics Data System (ADS)

Long, D. M.; Murphy, P.; Graham, G.; Carley, E. P.; Pérez-Suárez, D.

2017-12-01

Solar eruptions are the most spectacular events in our solar system and are associated with many different signatures of energy release including solar flares, coronal mass ejections, global waves, radio emission and accelerated particles. Here, we apply the Coronal Pulse Identification and Tracking Algorithm (CorPITA) to the high-cadence synoptic data provided by the Solar Dynamics Observatory (SDO) to identify and track global waves observed by SDO. 164 of the 362 solar flare events studied (45%) were found to have associated global waves with no waves found for the remaining 198 (55%). A clear linear relationship was found between the median initial velocity and the acceleration of the waves, with faster waves exhibiting a stronger deceleration (consistent with previous results). No clear relationship was found between global waves and type II radio bursts, electrons or protons detected in situ near Earth. While no relationship was found between the wave properties and the associated flare size (with waves produced by flares from B to X-class), more than a quarter of the active regions studied were found to produce more than one wave event. These results suggest that the presence of a global wave in a solar eruption is most likely determined by the structure and connectivity of the erupting active region and the surrounding quiet solar corona rather than by the amount of free energy available within the active region.

An optical mm-wave generation scheme by frequency octupling using a nested MMI

NASA Astrophysics Data System (ADS)

Shang, Lei; Wen, Aijun; Li, Bo; Wang, Tonggang; Chen, Yang; Li, Ming'an

2011-12-01

A novel method of a filterless optical millimeter-wave (MMW) signal generation with frequency octupling via a nested multimode interference (MMI) coupler is proposed for Radio-over-fiber systems. By setting the DC bias voltage applied to the central arms of MMI-b and MMI-c accurately, the optical carrier can be completely suppressed. The OSSR can be as high as about 58 dB without optical filter and the radio frequency spurious suppression ratio (RFSSR) exceeds 32 dB, which is the best result as we know. Simulation results suggest that when the generated optical mm-wave signal is transmitted along the standard single-mode fiber, the eye diagram is still opened after being transmitted over a 50 km fiber.

Sensitivity of Pulsar Timing Arrays

NASA Astrophysics Data System (ADS)

Siemens, Xavier

2015-08-01

For the better part of the last decade, the North American Nanohertz Observatory for Gravitational Waves (NANOGrav) has been using the Green Bank and Arecibo radio telescopes to monitor millisecond pulsars. NANOGrav, along with similar international collaborations, the European Pulsar Timing Array and the Parkes Pulsar Timing Array in Australia, form a consortium of consortia: the International Pulsar Timing Array (IPTA). The goal of the IPTA is to directly detect low-frequency gravitational waves which cause small changes to the times of arrival of radio pulses from millisecond pulsars. In this talk I will discuss the work of NANOGrav and the IPTA as well as our sensitivity to gravitational waves from astrophysical sources. I will show that a detection is possible by the end of the decade.

Solar radio emissions: 2D full PIC simulations

NASA Astrophysics Data System (ADS)

Pierre, H.; Sgattoni, A.; Briand, C.; Amiranoff, F.; Riconda, C.

2016-12-01

Solar radio emissions are electromagnetic waves observed at the local plasma frequency and/or at twice the plasma frequency. To describe their origin a multi-stage model has been proposed by Ginzburg & Zhelezniakov (1958) and further developed by several authors, which consider a succession of non-linear three-wave interaction processes. Electron beams accelerated by solar flares travel in the interplanetary plasma and provide the free energy for the development of plasma instabilities. The model describes how part of the free energy of these beams can be transformed in a succession of plasma waves and eventually into electromagnetic waves. Following the work of Thurgood & Tsiklauri (2015) we performed several 2D Particle In Cell simulations. The simulations follow the entire set of processes from the electron beam propagation in the background plasma to the generation of the electromagnetic waves in particular the 2ωp emission, including the excitation of the low frequency waves. As suggested by Thurgood & Tsiklauri (2015) it is possible to identify regimes where the radiation emission can be directly linked to the electron beams. Our attention was devoted to estimate the conversion efficiency from electron kinetic energy to the em energy, and the growth rate of the several processes which can be identified. We studied the emission angles of the 2ωpradiation and compared them with the theoretical predictions of Willes et. al. (1995). We also show the role played by some numerical parameters i.e. the size and shape of the simulation box. This work is the first step to prepare laser-plasma experiments. V. L. Ginzburg, V. V. Zhelezniakov On the Possible Mechanisms of Sporadic Solar Radio Emission (Radiation in an Isotropic Plasma) Soviet Astronomy, Vol. 2, p.653 (1958) J. O. Thurgood and D. Tsiklauri Self-consistent particle-in-cell simulations of funda- mental and harmonic plasma radio emission mechanisms. Astronomy & Astrophysics 584, A83 (2015). A. Willes, P. Robinson and D. Melrose (1995). Second harmonic electromagnetic emis- sion via Langmuir wave coalescence. Physics of Plasmas, 3(1), 149-159 (1995).

Evaluation of Electromagnetic Near-Field Measurement Technique as Non-Destructive Testing for Composite Structures

NASA Astrophysics Data System (ADS)

Raad Hussein, Alaa; Badri Albarody, Thar M.; Megat Yusoff, Puteri Sri Melor Bt

2018-05-01

Nowadays there is no viable non-destructive method that could detect flaws in complex composite products. Such a method could provide unique tools to allow engineers to minimize time consumption and cost during the evaluation of various product parameters without disturbing production. The latest research and development on propagation waves introduce micro, radio and millimetre waves as new potential non-destructive test methods for evaluation of mechanical flaws and prediction of failure in a product during production. This paper focuses on recent developments, usage, classification of electromagnetic waves under the range of radio frequency, millimetre and micro-waves. In addition, this paper reviews the application of propagation wave and proposed a new health monitoring technique based on Doppler Effect for vibration measurement in complex composite structures. Doppler Effect is influenced by dynamic behaviour of the composite structures and both are effect by flaws occurred inside the structure. Composite manufacturers, especially Aerospace industry are demanding these methods comprehensively inspect and evaluate the damages and defects in their products.

Wave propagation and earth satellite radio emission studies

NASA Technical Reports Server (NTRS)

Yeh, K. C.; Liu, C. H.; Flaherty, B. J.

1974-01-01

Radio propagation studies of the ionosphere using satellite radio beacons are described. The ionosphere is known as a dispersive, inhomogeneous, irregular and sometimes even nonlinear medium. After traversing through the ionosphere the radio signal bears signatures of these characteristics. A study of these signatures will be helpful in two areas: (1) It will assist in learning the behavior of the medium, in this case the ionosphere. (2) It will provide information of the kind of signal characteristics and statistics to be expected for communication and navigational satellite systems that use the similar geometry.

A decametric wavelength radio telescope for interplanetary scintillation observations

NASA Technical Reports Server (NTRS)

Cronyn, W. M.; Shawhan, S. D.

1975-01-01

A phased array, electrically steerable radio telescope (with a total collecting area of 18 acres), constructed for the purpose of remotely sensing electron density irregularity structure in the solar wind, is presented. The radio telescope is able to locate, map, and track large scale features of the solar wind, such as streams and blast waves, by monitoring a large grid of natural radio sources subject to rapid intensity fluctuation (interplanetary scintillation) caused by the irregularity structure. Observations verify the performance of the array, the receiver, and the scintillation signal processing circuitry of the telescope.

Mechanically Reconfigurable Single-Arm Spiral Antenna Array for Generation of Broadband Circularly Polarized Orbital Angular Momentum Vortex Waves.

PubMed

Li, Long; Zhou, Xiaoxiao

2018-03-23

In this paper, a mechanically reconfigurable circular array with single-arm spiral antennas (SASAs) is designed, fabricated, and experimentally demonstrated to generate broadband circularly polarized orbital angular momentum (OAM) vortex waves in radio frequency domain. With the symmetrical and broadband properties of single-arm spiral antennas, the vortex waves with different OAM modes can be mechanically reconfigurable generated in a wide band from 3.4 GHz to 4.7 GHz. The prototype of the circular array is proposed, conducted, and fabricated to validate the theoretical analysis. The simulated and experimental results verify that different OAM modes can be effectively generated by rotating the spiral arms of single-arm spiral antennas with corresponding degrees, which greatly simplify the feeding network. The proposed method paves a reconfigurable way to generate multiple OAM vortex waves with spin angular momentum (SAM) in radio and microwave satellite communication applications.

Applications of surface acoustic and shallow bulk acoustic wave devices

NASA Astrophysics Data System (ADS)

Campbell, Colin K.

1989-10-01

Surface acoustic wave (SAW) device coverage includes delay lines and filters operating at selected frequencies in the range from about 10 MHz to 11 GHz; modeling with single-crystal piezoelectrics and layered structures; resonators and low-loss filters; comb filters and multiplexers; antenna duplexers; harmonic devices; chirp filters for pulse compression; coding with fixed and programmable transversal filters; Barker and quadraphase coding; adaptive filters; acoustic and acoustoelectric convolvers and correlators for radar, spread spectrum, and packet radio; acoustooptic processors for Bragg modulation and spectrum analysis; real-time Fourier-transform and cepstrum processors for radar and sonar; compressive receivers; Nyquist filters for microwave digital radio; clock-recovery filters for fiber communications; fixed-, tunable-, and multimode oscillators and frequency synthesizers; acoustic charge transport; and other SAW devices for signal processing on gallium arsenide. Shallow bulk acoustic wave device applications include gigahertz delay lines, surface-transverse-wave resonators employing energy-trapping gratings, and oscillators with enhanced performance and capability.

Detectability of electrostatic decay products in Ulysses and Galileo observations of type 3 solar radio sources

NASA Technical Reports Server (NTRS)

Cairns, Iver H.

1995-01-01

Recent in situ Ulysses and Galileo observations of the source regions of type 3 solar radio bursts appear to show an absence of ion acoustic waves S produced by nonlinear Langmuir wave processes such as the electrostatic (ES) decay, in contradiction with earlier ISEE 3 observations and analytic theory. This letter resolves these apparent contradictions. Refined analyses of the maximum S-wave electric fields produced by ES decay and of the characteristics of the Ulysses Wave Form Analyzer (WFA) instrument show that the bursty S waves observed by the ISEE 3 should be essentially undetectable by the Ulysses WFA. It is also shown that the maximum S-wave levels predicted for the Galileo event are approximately less than the instrumental noise level, thereby confirming an earlier suggestion. Thus, no contradictions exist between the ISEE 3 and Ulysses/Galileo observation, and no evidence exists against ES decay in the published Ulysses and Galileo data. All available data are consistent with, or at worst not inconsistent with, the ES decay proceeding and being the dominant nonlinear process in type 3 bursts.

Solar Type II Radio Bursts and IP Type II Events

NASA Technical Reports Server (NTRS)

Cane, H. V.; Erickson, W. C.

2005-01-01

We have examined radio data from the WAVES experiment on the Wind spacecraft in conjunction with ground-based data in order to investigate the relationship between the shocks responsible for metric type II radio bursts and the shocks in front of coronal mass ejections (CMEs). The bow shocks of fast, large CMEs are strong interplanetary (IP) shocks, and the associated radio emissions often consist of single broad bands starting below approx. 4 MHz; such emissions were previously called IP type II events. In contrast, metric type II bursts are usually narrowbanded and display two harmonically related bands. In addition to displaying complete dynamic spectra for a number of events, we also analyze the 135 WAVES 1 - 14 MHz slow-drift time periods in 2001-2003. We find that most of the periods contain multiple phenomena, which we divide into three groups: metric type II extensions, IP type II events, and blobs and bands. About half of the WAVES listings include probable extensions of metric type II radio bursts, but in more than half of these events, there were also other slow-drift features. In the 3 yr study period, there were 31 IP type II events; these were associated with the very fastest CMEs. The most common form of activity in the WAVES events, blobs and bands in the frequency range between 1 and 8 MHz, fall below an envelope consistent with the early signatures of an IP type II event. However, most of this activity lasts only a few tens of minutes, whereas IP type II events last for many hours. In this study we find many examples in the radio data of two shock-like phenomena with different characteristics that occur simultaneously in the metric and decametric/hectometric bands, and no clear example of a metric type II burst that extends continuously down in frequency to become an IP type II event. The simplest interpretation is that metric type II bursts, unlike IP type II events, are not caused by shocks driven in front of CMEs.

Cassini Radio and Plasma Wave Observations at Saturn

NASA Technical Reports Server (NTRS)

Gurnett, D. A.; Kurth, W. S.; Hospodarsky, G. B.; Persoon, A. M.; Averkamp, T. F.; Ceccni, B.; Lecacheux, A.; Zarka, P.; Canu, P.; Cornilleau-Wehrlin, N.

2005-01-01

Results are presented from the Cassini radio and plasma wave instrument during the approach and first few orbits around Saturn. During the approach the intensity modulation of Saturn Kilometric Radiation (SKR) showed that the radio rotation period of Saturn has increased to 10 hr 45 min plus or minus 36 sec, about 6 min longer than measured by Voyager in 1980-81. Also, many intense impulsive radio signals called Saturn Electrostatic Discharges (SEDs) were detected from saturnian lightning, starting as far as 1.08 AU from Saturn, much farther than terrestrial lightning can be detected from Earth. Some of the SED episodes have been linked to cloud systems observed in Saturn s atmosphere by the Cassini imaging system. Within the magnetosphere plasma wave emissions have been used to construct an electron density profile through the inner region of the magnetosphere. With decreasing radial distance the electron density increases gradually to a peak of about 100 per cubic centimeter near the outer edge of the A ring, and then drops precipitously to values as low as .03 per cubic centimeter over the rings. Numerous nearly monochromatic whistler-mode emissions were observed as the spacecraft passed over the rings that are believed to be produced by meteoroid impacts on the rings. Whistlermode emissions, similar to terrestrial auroral hiss were also observed over the rings, indicating that an electrodynamic interaction, similar to auroral particle acceleration, may be occurring in or near the rings. During the Titan flybys Langmuir probe and plasma wave measurements provided observations of the density and temperature in Titan's ionosphere.

Proceedings of the Twenty-First NASA Propagation Experiments Meeting (NAPEX XXI) and the Advanced Communications Technology Satellite (ACTS) Propagation Studies Miniworkshop

NASA Technical Reports Server (NTRS)

Golshan, Nasser (Editor)

1997-01-01

The NASA Propagation Experimenters (NAPEX) meeting is convened each year to discuss studies supported by the NASA Propagation Program. Representatives from the satellite communications industry, academia and government who have an interest in space-ground radio wave propagation are invited to NAPEX meetings for discussions and exchange of information. The reports delivered at this meeting by program managers and investigators present recent activities and future plans. This forum provides an opportunity for peer discussion of work in progress, timely dissemination of propagation results, and close interaction with the satellite communications industry. NAPEX XXI took place in El Segundo, California on June 11-12, 1997 and consisted of three sessions. Session 1, entitled "ACTS Propagation Study Results & Outcome " covered the results of 20 station-years of Ka-band radio-wave propagation experiments. Session 11, 'Ka-band Propagation Studies and Models,' provided the latest developments in modeling, and analysis of experimental results about radio wave propagation phenomena for design of Ka-band satellite communications systems. Session 111, 'Propagation Research Topics,' covered a diverse range of propagation topics of interest to the space community, including overviews of handbooks and databases on radio wave propagation. The ACTS Propagation Studies miniworkshop was held on June 13, 1997 and consisted of a technical session in the morning and a plenary session in the afternoon. The morning session covered updates on the status of the ACTS Project & Propagation Program, engineering support for ACTS Propagation Terminals, and the Data Center. The plenary session made specific recommendations for the future direction of the program.

Measurement of radio emission from extensive air showers with LOPES

NASA Astrophysics Data System (ADS)

Hörandel, J. R.; Apel, W. D.; Arteaga, J. C.; Asch, T.; Badea, F.; Bähren, L.; Bekk, K.; Bertaina, M.; Biermann, P. L.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Brüggemann, M.; Buchholz, P.; Buitink, S.; Cantoni, E.; Chiavassa, A.; Cossavella, F.; Daumiller, K.; de Souza, V.; di Pierro, F.; Doll, P.; Ender, M.; Engel, R.; Falcke, H.; Finger, M.; Fuhrmann, D.; Gemmeke, H.; Ghia, P. L.; Glasstetter, R.; Grupen, C.; Haungs, A.; Heck, D.; Horneffer, A.; Huege, T.; Isar, P. G.; Kampert, K.-H.; Kang, D.; Kickelbick, D.; Krömer, O.; Kuijpers, J.; Lafebre, S.; Link, K.; Łuczak, P.; Ludwig, M.; Mathes, H. J.; Mayer, H. J.; Melissas, M.; Mitrica, B.; Morello, C.; Navarra, G.; Nehls, S.; Nigl, A.; Oehlschläger, J.; Over, S.; Palmieri, N.; Petcu, M.; Pierog, T.; Rautenberg, J.; Rebel, H.; Roth, M.; Saftoiu, A.; Schieler, H.; Schmidt, A.; Schröder, F.; Sima, O.; Singh, K.; Toma, G.; Trinchero, G. C.; Ulrich, H.; Weindl, A.; Wochele, J.; Wommer, M.; Zabierowski, J.; Zensus, J. A.

2011-02-01

A new method is explored to detect extensive air showers: the measurement of radio waves emitted during the propagation of the electromagnetic shower component in the magnetic field of the Earth. Recent results of the pioneering experiment LOPES are discussed. It registers radio signals in the frequency range between 40 and 80 MHz. The intensity of the measured radio emission is investigated as a function of different shower parameters, such as shower energy, angle of incidence, and distance to shower axis. In addition, new antenna types are developed in the framework of LOPESstar and new methods are explored to realize a radio self-trigger algorithm in real time.

The Deep Space Network as an instrument for radio science research

NASA Technical Reports Server (NTRS)

Asmar, S. W.; Renzetti, N. A.

1993-01-01

Radio science experiments use radio links between spacecraft and sensor instrumentation that is implemented in the Deep Space Network. The deep space communication complexes along with the telecommunications subsystem on board the spacecraft constitute the major elements of the radio science instrumentation. Investigators examine small changes in the phase and/or amplitude of the radio signal propagating from a spacecraft to study the atmospheric and ionospheric structure of planets and satellites, planetary gravitational fields, shapes, masses, planetary rings, ephemerides of planets, solar corona, magnetic fields, cometary comae, and such aspects of the theory of general relativity as gravitational waves and gravitational redshift.

USE OF RFID TO TRACK HAZARDOUS WASTE SHIPMENTS ACROSS DOMESTIC AND INTERNATIONAL BORDERS

EPA Science Inventory

Radio-frequency identification system (RFID) is an emerging commodity tracking technology that is being tested and implemented in a large number of applications worldwide. RFID is a method of transmitting data using radio waves, usually through communication with a tag. Both ac...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pe’er, Asaf; Long, Killian; Casella, Piergiorgio

Internal shocks between propagating plasma shells, originally ejected at different times with different velocities, are believed to play a major role in dissipating the kinetic energy, thereby explaining the observed light curves and spectra in a large range of transient objects. Even if initially the colliding plasmas are cold, following the first collision, the plasma shells are substantially heated, implying that in a scenario of multiple collisions, most collisions take place between plasmas of non-zero temperatures. Here, we calculate the dynamical properties of plasmas resulting from a collision between arbitrarily hot plasma shells, moving at arbitrary speeds. We provide simplemore » analytical expressions valid for both ultrarelativistic and Newtonian velocities for both hot and cold plasmas. We derive the minimum criteria required for the formation of the two-shock wave system, and show that in the relativistic limit, the minimum Lorentz factor is proportional to the square root of the ratio of the initial plasmas enthalpies. We provide basic scaling laws of synchrotron emission from both the forward and reverse-shock waves, and show how these can be used to deduce the properties of the colliding shells. Finally, we discuss the implications of these results in the study of several astronomical transients, such as X-ray binaries, radio-loud quasars, and gamma-ray bursts.« less

Plasma wave phenomena at interplanetary shocks observed by the Ulysses URAP experiment. [Unified Radio and Plasma Waves

NASA Technical Reports Server (NTRS)

Lengyel-Frey, D.; Macdowall, R. J.; Stone, R. G.; Hoang, S.; Pantellini, F.; Harvey, C.; Mangeney, A.; Kellogg, P.; Thiessen, J.; Canu, P.

1992-01-01

We present Ulysses URAP observations of plasma waves at seven interplanetary shocks detected between approximately 1 and 3 AU. The URAP data allows ready correlation of wave phenomena from .1 Hz to 1 MHz. Wave phenomena observed in the shock vicinity include abrupt changes in the quasi-thermal noise continuum, Langmuir wave activity, ion acoustic noise, whistler waves and low frequency electrostatic waves. We focus on the forward/reverse shock pair of May 27, 1991 to demonstrate the characteristics of the URAP data.

STS-56 Pilot Oswald uses SAREX on forward flight deck of Discovery, OV-103

NASA Image and Video Library

1993-04-17

STS056-04-004 (8-17 April 1993) --- Aboard Discovery, Astronaut Stephen S. Oswald, Pilot, talks to amateur radio operators on Earth via the Shuttle Amateur Radio Experiment (SAREX). SAREX was established by NASA, the American Radio League/Amateur Radio Satellite Corporation and the Johnson Space Center Amateur Radio Club to encourage public participation in the space program through a program to demonstrate the effectiveness of conducting short-wave radio transmissions between the Shuttle and ground-based radio operators at low-cost ground stations with amateur and digital techniques. As on several previous missions, SAREX was used on this flight as an educational opportunity for students around the world to learn about space firsthand by speaking directly to astronauts aboard the Shuttle.

Radio Frequency Interference Detection using Machine Learning.

NASA Astrophysics Data System (ADS)

Mosiane, Olorato; Oozeer, Nadeem; Aniyan, Arun; Bassett, Bruce A.

2017-05-01

Radio frequency interference (RFI) has plagued radio astronomy which potentially might be as bad or worse by the time the Square Kilometre Array (SKA) comes up. RFI can be either internal (generated by instruments) or external that originates from intentional or unintentional radio emission generated by man. With the huge amount of data that will be available with up coming radio telescopes, an automated aproach will be required to detect RFI. In this paper to try automate this process we present the result of applying machine learning techniques to cross match RFI from the Karoo Array Telescope (KAT-7) data. We found that not all the features selected to characterise RFI are always important. We further investigated 3 machine learning techniques and conclude that the Random forest classifier performs with a 98% Area Under Curve and 91% recall in detecting RFI.

Orthogonality catastrophe and fractional exclusion statistics

NASA Astrophysics Data System (ADS)

Ares, Filiberto; Gupta, Kumar S.; de Queiroz, Amilcar R.

2018-02-01

We show that the N -particle Sutherland model with inverse-square and harmonic interactions exhibits orthogonality catastrophe. For a fixed value of the harmonic coupling, the overlap of the N -body ground state wave functions with two different values of the inverse-square interaction term goes to zero in the thermodynamic limit. When the two values of the inverse-square coupling differ by an infinitesimal amount, the wave function overlap shows an exponential suppression. This is qualitatively different from the usual power law suppression observed in the Anderson's orthogonality catastrophe. We also obtain an analytic expression for the wave function overlaps for an arbitrary set of couplings, whose properties are analyzed numerically. The quasiparticles constituting the ground state wave functions of the Sutherland model are known to obey fractional exclusion statistics. Our analysis indicates that the orthogonality catastrophe may be valid in systems with more general kinds of statistics than just the fermionic type.

Orthogonality catastrophe and fractional exclusion statistics.

PubMed

Ares, Filiberto; Gupta, Kumar S; de Queiroz, Amilcar R

2018-02-01

We show that the N-particle Sutherland model with inverse-square and harmonic interactions exhibits orthogonality catastrophe. For a fixed value of the harmonic coupling, the overlap of the N-body ground state wave functions with two different values of the inverse-square interaction term goes to zero in the thermodynamic limit. When the two values of the inverse-square coupling differ by an infinitesimal amount, the wave function overlap shows an exponential suppression. This is qualitatively different from the usual power law suppression observed in the Anderson's orthogonality catastrophe. We also obtain an analytic expression for the wave function overlaps for an arbitrary set of couplings, whose properties are analyzed numerically. The quasiparticles constituting the ground state wave functions of the Sutherland model are known to obey fractional exclusion statistics. Our analysis indicates that the orthogonality catastrophe may be valid in systems with more general kinds of statistics than just the fermionic type.

Plasma Pancakes and Deep Cavities Generated by High Power Radio Waves from the Arecibo Observatory

NASA Astrophysics Data System (ADS)

Bernhardt, P. A.; Briczinski, S. J., Jr.; Zawdie, K.; Huba, J.; Siefring, C. L.; Sulzer, M. P.; Nossa, E.; Aponte, N.; Perillat, P.; Jackson-Booth, N.

2017-12-01

Breakdown of the neutral atmosphere at ionospheric altitudes can be achieved with high power HF waves that reflect on the bottomside of the ionosphere. For overdense heating (i.e., wave frequency < maximum plasma frequency in the F-layer), the largest electric fields in the plasma are found just below the reflection altitude. There, electromagnetic waves are converted into electron plasma (Langmir) waves and ion acoustic waves. These waves are measured by scattering of the 430 MHz radar at Arecibo to from an enhanced plasma line. The photo-electron excitation of Langmuir waves yields a weaker plasma-line profile that shows the complete electron profile with the radar. Once HF enhanced Langmuir waves are formed, they can accelerate the photo-electron population to sufficient energies for neutral breakdown and enhanced ionization inside the HF Radio Beam. Plasma pancakes are produced because the breakdown process continues to build up plasma on bottom of the breakdown clouds and recombination occurs on the older breakdown plasma at the top of these clouds. Thus, the plasma pancake falls with altitude from the initial HF wave reflection altitude near 250 km to about 160 km where ion-electron recombination prevents the plasma cloud from being sustained by the high power HF. Experiments in March 2017 have produced plasma pancakes with about 100 Mega-Watts effective radiated power 5.1 MHz with the Arecibo HF Facility. Observations using the 430 MHz radar show falling plasma pancakes that disappear at low altitudes and reform at the F-layer critical reflection altitude. Sometimes the periodic and regular falling motion of the plasma pancakes is influenced by Acoustic Gravity Waves (AGW) propagating through the modified HF region. A rising AGW can cause the plasma pancake to reside at nearly constant altitude for 10 to 20 minutes. Dense cavities are also produced by high power radio waves interacting with the F-Layer. These structures are observed with the Arecibo 430 MHz radar as intense bight-outs in the plasma profile. Multiple cavities are seen simultaneously.

Radio Heating of Lunar Soil to Release Gases

NASA Technical Reports Server (NTRS)

Chui, Talso; Penanen, Konstantin

2006-01-01

A report proposes the development of a system to collect volatile elements and compounds from Lunar soil for use in supporting habitation and processing into rocket fuel. Prior exploratory missions revealed that H2, He, and N2 are present in Lunar soil and there are some indications that water ice may also be present. The proposed system would include a shroud that would be placed on the Lunar surface. Inside the shroud would be a radio antenna aimed downward. The antenna would be excited at a suitably high power and at a frequency chosen to optimize the depth of penetration of radio waves into the soil. The radio waves would heat the soil, thereby releasing volatiles bound to soil particles. The escaping volatiles would be retained by the shroud and collected by condensation in a radiatively cooled vessel connected to the shroud. It has been estimated that through radio-frequency heating at a power of 10 kW for one day, it should be possible to increase the temperature of a soil volume of about 1 cubic m by about 200 C -- an amount that should suffice for harvesting a significant quantity of volatile material.

Low-latency fiber-millimeter-wave system for future mobile fronthauling

NASA Astrophysics Data System (ADS)

Tien Dat, Pham; Kanno, Atsushi; Yamamoto, Naokatsu; Kawanishi, Tetsuya

2016-02-01

A seamless combination of fiber and millimeter-wave (MMW) systems can be very attractive for future heterogeneous mobile networks such as 5G because of its flexibility and high bandwidth. Analog mobile signal transmission over seamless fiber-MMW systems is very promising to reduce the latency and the required band-width, and to simplify the systems. However, stable and high-performance seamless systems are indispensable to conserve the quality of the analog signal transmission. In this paper, we present several technologies to develop such seamless fiber-MMW systems. In the downlink direction, a high-performance system can be realized using a high-quality optical MMW signal generator and a self-homodyne MMW signal detector. In the uplink direction, a cascade of radio-on-radio and radio-over-fiber systems using a burst-mode optical amplifier can support bursty radio signal transmission. A full-duplex transmission with negligible interference effects can be realized using frequency multiplexing in the radio link and wavelength-division multiplexing in the optical link. A high-spectral efficiency MMW-over-fiber system using an intermediate frequency-over-fiber system and a high-quality remote delivery of a local oscillator signal is highly desirable to reduce the costs.

Lunar Radio_phase Ranging in Chinese Lunar Lander Mission for Astrometry

NASA Astrophysics Data System (ADS)

Ping, Jinsong; Meng, Qiao; Li, Wenxiao; Wang, Mingyuan; Wang, Zhen; Zhang, Tianyi; Han, Songtao

2015-08-01

The radio tracking data in lunar and planetary missions can be directly applied for scientific investigation. The variations of phase and of amplitude of the radio carrier wave signal linked between the spacecraft and the ground tracking antenna are used to deduce the planetary atmospheric and ionospheric structure, planetary gravity field, mass, ring, ephemeris, and even to test the general relativity. In the Chinese lunar missions, we developed the lunar and planetary radio science receiver to measure the distance variation between the tracking station-lander by means of open loop radio phase tracking. Using this method in Chang’E-3 landing mission, a lunar radio_phase ranging (LRR) technique was realized at Chinese deep space tracking stations and astronomical VLBI stations with H-maser clocks installed. Radio transponder and transmitter had been installed on the Chang’E-3/4. Transponder will receive the uplink S/X band radio wave transmitted from the two newly constructed Chinese deep space stations, where the high quality hydrogen maser atomic clocks have been used as local time and frequency standard. The clocks between VLBI stations and deep space stations can be synchronized to UTC standard within 20 nanoseconds using satellite common view methods. In the near future there will be a plan to improve this accuracy to 5 nanoseconds or better, as the level of other deep space network around world. In the preliminary LRR experiments of Chang'E-3, the obtained 1sps phase ranging observables have a resolution of 0.2 millimeter or better, with a fitting RMS about 2~3 millimeter, after the atmospheric and ionospheric errors removed. This method can be a new astrometric technique to measure the Earth tide and rotation, lunar orbit, tides and liberation, by means of solo observation or of working together with Lunar Laser Ranging. After differencing the ranging, we even obtained 1sps doppler series of 2-way observables with resolution of 0.07mm/second, which can be used to check the uplimit for low frequency (0.001~1 Hz) gravitational wave detection between the Earth and the Moon.

Radio Wave Propagation Handbook for Communication on and Around Mars

NASA Technical Reports Server (NTRS)

Ho, Christian; Golshan, Nasser; Kliore, Arvydas

2002-01-01

This handbook examines the effects of the Martian environment on radio wave propagation on Mars and in the space near the planet. The environmental effects include these from the Martian atmosphere, ionosphere, global dust storms, aerosols, clouds, and geomorphologic features. Relevant Martian environmental parameters were extracted from the measurements of Mars missions during the past 30 years, especially from Mars Pathfinder and Mars Global Surveyor. The results derived from measurements and analyses have been reviewed through an extensive literature search. The updated parameters have been theoretically analyzed to study their effects on radio propagation. This handbook also provides basic information about the entire telecommunications environment on and around Mars for propagation researchers, system engineers, and link analysts. Based on these original analyses, some important recommendations have been made, including the use of the Martian ionosphere as a reflector for Mars global or trans-horizon communication between future Martian colonies, reducing dust storm scattering effects, etc. These results have extended our wave propagation knowledge to a planet other than Earth; and the tables, models, and graphics included in this handbook will benefit telecommunication system engineers and scientific researchers.

Atmospheric waves and dynamics beneath Jupiter's clouds from radio wavelength observations

NASA Astrophysics Data System (ADS)

Cosentino, Richard G.; Butler, Bryan; Sault, Bob; Morales-Juberías, Raúl; Simon, Amy; de Pater, Imke

2017-08-01

We observed Jupiter at wavelengths near 2 cm with the Karl G. Jansky Very Large Array (VLA) in February 2015. These frequencies are mostly sensitive to variations in ammonia abundance and probe between ∼ 0.5 - 2.0 bars of pressure in Jupiter's atmosphere; within and below the visible cloud deck which has its base near 0.7 bars. The resultant observed data were projected into a cylindrical map of the planet with spatial resolution of ∼1500 km at the equator. We have examined the data for atmospheric waves and observed a prominent bright belt of radio hotspot features near 10°N, likely connected to the same equatorial wave associated with the 5-μm hotspots. We conducted a passive tracer power spectral wave analysis for the entire map and latitude regions corresponding to eastward and westward jets and compare our results to previous studies. The power spectra analysis revealed that the atmosphere sampled in our observation (excluding the NEB region) is in a 2-D turbulent regime and its dynamics are predominately governed by the shallow water equations. The Great Red Spot (GRS) is also very prominent and has a noticeable meridional asymmetry and we compare it, and nearby storms, with optical images. We find that the meridional radio profile has a global north-south hemisphere distinction and find correlations of it to optical intensity banding and to shear zones of the zonal wind profile over select regions of latitude. Amateur optical images taken before and after our observation complemented the radio wavelength map to investigate dynamics of the equatorial region in Jupiter's atmosphere. We find that two radio hotspots at 2 cm are well correlated with optical plumes in the NEB, additionally revealing they are not the same 5 μm hotspot features correlated with optical dark patches between adjacent plumes. This analysis exploits the VLA's upgraded sensitivity and explores the opportunities now possible when studying gas giants, especially atmospheric dynamics of layers beneath upper level clouds.

Wave packet dynamics for a system with position and time-dependent effective mass in an infinite square well

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vubangsi, M.; Tchoffo, M.; Fai, L. C.

The problem of a particle with position and time-dependent effective mass in a one-dimensional infinite square well is treated by means of a quantum canonical formalism. The dynamics of a launched wave packet of the system reveals a peculiar revival pattern that is discussed. .

A Case Study of On-the-fly Wide-field Radio Imaging Applied to the Gravitational Wave Event GW151226

NASA Astrophysics Data System (ADS)

Mooley, K. P.; Frail, D. A.; Myers, S. T.; Kulkarni, S. R.; Hotokezaka, K.; Singer, L. P.; Horesh, A.; Kasliwal, M. M.; Cenko, S. B.; Hallinan, G.

2018-04-01

We apply a newly developed on-the-fly mosaicing technique on the Jansky Very Large Array (VLA) at 3 GHz in order to carry out a sensitive search for an afterglow from the Advanced LIGO binary black hole merger event GW151226. In three epochs between 1.5 and 6 months post-merger, we observed a 100 deg2 region, with more than 80% of the survey region having an rms sensitivity of better than 150 μJy/beam, in the northern hemisphere with a merger containment probability of 10%. The data were processed in near real time and analyzed to search for transients and variables. No transients were found but we have demonstrated the ability to conduct blind searches in a time-frequency phase space where the predicted afterglow signals are strongest. If the gravitational wave event is contained within our survey region, the upper limit on any late-time radio afterglow from the merger event at an assumed mean distance of 440 Mpc is about 1029 erg s‑1 Hz‑1. Approximately 1.5% of the radio sources in the field showed variability at a level of 30%, and can be attributed to normal activity from active galactic nuclei. The low rate of false positives in the radio sky suggests that wide-field imaging searches at a few Gigahertz can be an efficient and competitive search strategy. We discuss our search method in the context of the recent afterglow detection from GW170817 and radio follow-up in future gravitational wave observing runs.

Four Decades of Space-Borne Radio Sounding

NASA Technical Reports Server (NTRS)

Benson, Robert F.

2010-01-01

A review is given of the 38 rocket, satellite, and planetary payloads dedicated to ionospheric/magnetospheric radio sounding since 1961. Between 1961 and 1995, eleven sounding-rocket payloads from four countries evolved from proof-of-concept flights to sophisticated instruments. Some involved dual payloads, with the sounder transmitter on one and the sounder receiver on the other. The rocket sounders addressed specific space-plasma-wave questions, and provided improved measurements of ionospheric electron-density (N(sub e)) field-aligned irregularities (FAI). Four countries launched 12 ionospheric topside-sounder satellites between 1962 and 1994, and an ionospheric sounder was placed on the Mir Space Station in 1998. Eleven magnetospheric radio sounders, most of the relaxation type, were launched from 1977 to 2000. The relaxation sounders used low-power transmitters, designed to stimulate plasma resonances for accurate local Ne determinations. The latest magnetospheric sounder designed for remote sensing incorporated long antennas and digital signal processing techniques to overcome the challenges posed by low Ne values and large propagation distances. Three radio sounders from three countries were included on payloads to extraterrestrial destinations from 1990 to 2003. The scientific accomplishments of space-borne radio sounders included (1) a wealth of global N(sub e) information on the topside ionosphere and magnetosphere, based on vertical and magnetic-field-aligned N(sub e) profiles; (2) accurate in-situ N(sub e) values, even under low-density conditions; and (3) fundamental advances in our understanding of the excitation and propagation of plasma waves, which have even led to the prediction of a new plasma-wave mode.

Diagnostic criteria for the characterization of quasireversible electron transfer reactions by cyclic square wave voltammetry.

PubMed

Mann, Megan A; Helfrick, John C; Bottomley, Lawrence A

2014-08-19

Theory for cyclic square wave voltammetry of quasireversible electron transfer reactions is presented and experimentally verified. The impact of empirical parameters on the shape of the current-voltage curve is examined. From the trends, diagnostic criteria enabling the use of this waveform as a tool for mechanistic analysis of electrode reaction processes are presented. These criteria were experimentally confirmed using Eu(3+)/Eu(2+), a well-established quasireversible analyte. Using cyclic square wave voltammetry, both the electron transfer coefficient and rate were calculated for this analyte and found to be in excellent agreement with literature. When properly applied, these criteria will enable nonexperts in voltammetry to assign the electrode reaction mechanism and accurately measure electrode reaction kinetics.

Advanced capability RFID system

DOEpatents

Gilbert, Ronald W.; Steele, Kerry D.; Anderson, Gordon A.

2007-09-25

A radio-frequency transponder device having an antenna circuit configured to receive radio-frequency signals and to return modulated radio-frequency signals via continuous wave backscatter, a modulation circuit coupled to the antenna circuit for generating the modulated radio-frequency signals, and a microprocessor coupled to the antenna circuit and the modulation circuit and configured to receive and extract operating power from the received radio-frequency signals and to monitor inputs on at least one input pin and to generate responsive signals to the modulation circuit for modulating the radio-frequency signals. The microprocessor can be configured to generate output signals on output pins to associated devices for controlling the operation thereof. Electrical energy can be extracted and stored in an optional electrical power storage device.

77 FR 53159 - Passenger Use of Portable Electronic Devices on Board Aircraft

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-31

... to navigation systems such as very high frequency (VHF) Omni Range (VOR) navigation systems. \\1\\ 14... navigation, communication, and surveillance radio receivers that may be susceptible at certain frequencies to... space by electromagnetic waves on specific radio frequencies that are used to communicate information...

National Intelligence Survey. Spain. Section 23. Weather and Climate

DTIC Science & Technology

1963-07-01

on to successor organiza- tions. In 1934 the meteorological services were organized as the Servicio Meteorolögico Nacional (S.M.N.). Spain became a...service’s communications system for collecting data relies heavily on tele- phone, telegraph, and CW-radio broadcasts. A micro -wave radio teletype

47 CFR 27.4 - Terms and definitions.

Code of Federal Regulations, 2014 CFR

2014-10-01

... product of the power supplied to the antenna and its gain relative to a half-wave dipole in a given... and the antenna gain in a given direction relative to an isotropic antenna. Fixed service. A radio... functions that could be performed at the transmitter. Satellite Digital Audio Radio Service (satellite DARS...

This is NHK 1976-77.

ERIC Educational Resources Information Center

Japan Broadcasting Co., Tokyo

Nippon Hoso Kyokai (NHK), the Japanese Broadcasting Corporation, operates two public television, two medium wave radio and one VHF-FM public radio networks. NHK derives its support from receiver fees. Under the 1950 Broadcast Law which established NHK as a public broadcasting organization the Prime Minister appoints NHK's Board of Governors and…

The effect of solar radio bursts on the GNSS radio occultation signals

NASA Astrophysics Data System (ADS)

Yue, Xinan; Schreiner, William S.; Kuo, Ying-Hwa; Zhao, Biqiang; Wan, Weixing; Ren, Zhipeng; Liu, Libo; Wei, Yong; Lei, Jiuhou; Solomon, Stan; Rocken, Christian

2013-09-01

radio burst (SRB) is the radio wave emission after a solar flare, covering a broad frequency range, originated from the Sun's atmosphere. During the SRB occurrence, some specific frequency radio wave could interfere with the Global Navigation Satellite System (GNSS) signals and therefore disturb the received signals. In this study, the low Earth orbit- (LEO-) based high-resolution GNSS radio occultation (RO) signals from multiple satellites (COSMIC, CHAMP, GRACE, SAC-C, Metop-A, and TerraSAR-X) processed in University Corporation for Atmospheric Research (UCAR) were first used to evaluate the effect of SRB on the RO technique. The radio solar telescope network (RSTN) observed radio flux was used to represent SRB occurrence. An extreme case during 6 December 2006 and statistical analysis during April 2006 to September 2012 were studied. The LEO RO signals show frequent loss of lock (LOL), simultaneous decrease on L1 and L2 signal-to-noise ratio (SNR) globally during daytime, small-scale perturbations of SNR, and decreased successful retrieval percentage (SRP) for both ionospheric and atmospheric occultations during SRB occurrence. A potential harmonic band interference was identified. Either decreased data volume or data quality will influence weather prediction, climate study, and space weather monitoring by using RO data during SRB time. Statistically, the SRP of ionospheric and atmospheric occultation retrieval shows ~4% and ~13% decrease, respectively, while the SNR of L1 and L2 show ~5.7% and ~11.7% decrease, respectively. A threshold value of ~1807 SFU of 1415 MHz frequency, which can result in observable GNSS SNR decrease, was derived based on our statistical analysis.

Angle-resolved spin wave band diagrams of square antidot lattices studied by Brillouin light scattering

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gubbiotti, G.; Tacchi, S.; Montoncello, F.

2015-06-29

The Brillouin light scattering technique has been exploited to study the angle-resolved spin wave band diagrams of squared Permalloy antidot lattice. Frequency dispersion of spin waves has been measured for a set of fixed wave vector magnitudes, while varying the wave vector in-plane orientation with respect to the applied magnetic field. The magnonic band gap between the two most dispersive modes exhibits a minimum value at an angular position, which exclusively depends on the product between the selected wave vector magnitude and the lattice constant of the array. The experimental data are in very good agreement with predictions obtained bymore » dynamical matrix method calculations. The presented results are relevant for magnonic devices where the antidot lattice, acting as a diffraction grating, is exploited to achieve multidirectional spin wave emission.« less

A Jupiter Data Analysis Program (JDAP) research grant on wave accessibility and attributes

NASA Technical Reports Server (NTRS)

Calvert, Wynne

1987-01-01

For more than thirty years the intense decametric radio emissions from Jupiter (DAM) and the corresponding auroral kilometric radiation from the Earth (AKR) have remained major radio science mysteries. Part of the problem, aside from their inherent complexity, has been the difficulty of measuring their source location and emission properties from limited observations. Progress has been made on this problem by locating the source directly, i.e., by analysis of the faraday rotation observed with Voyager as the wave path crossed the Io plasma torus, and indirectly by comparing the peak frequencies of the decametric emission with that at the foot of the Io flux tube. Progress was also made on the general question of how the emissions originate by finding properties of both the AKR and DAM which would imply emission by natural radio lasing.

A radio counterpart to a neutron star merger

NASA Astrophysics Data System (ADS)

Hallinan, G.; Corsi, A.; Mooley, K. P.; Hotokezaka, K.; Nakar, E.; Kasliwal, M. M.; Kaplan, D. L.; Frail, D. A.; Myers, S. T.; Murphy, T.; De, K.; Dobie, D.; Allison, J. R.; Bannister, K. W.; Bhalerao, V.; Chandra, P.; Clarke, T. E.; Giacintucci, S.; Ho, A. Y. Q.; Horesh, A.; Kassim, N. E.; Kulkarni, S. R.; Lenc, E.; Lockman, F. J.; Lynch, C.; Nichols, D.; Nissanke, S.; Palliyaguru, N.; Peters, W. M.; Piran, T.; Rana, J.; Sadler, E. M.; Singer, L. P.

2017-12-01

The gravitational wave event GW170817 was caused by the merger of two neutron stars (see the Introduction by Smith). In three papers, teams associated with the GROWTH (Global Relay of Observatories Watching Transients Happen) project present their observations of the event at wavelengths from x-rays to radio waves. Evans et al. used space telescopes to detect GW170817 in the ultraviolet and place limits on its x-ray flux, showing that the merger generated a hot explosion known as a blue kilonova. Hallinan et al. describe radio emissions generated as the explosion slammed into the surrounding gas within the host galaxy. Kasliwal et al. present additional observations in the optical and infrared and formulate a model for the event involving a cocoon of material expanding at close to the speed of light, matching the data at all observed wavelengths.

Ionosphere/microwave beam interaction study. [satellite solar energy conversion

NASA Technical Reports Server (NTRS)

Duncan, L. M.; Gordon, W. E.

1977-01-01

A solar power satellite microwave power density of 20mw sq cm was confirmed as the level where nonlinear interactions may occur in the ionosphere, particularly at 100 km altitude. Radio wave heating at this altitude, produced at the Arecibo Observatory, yielded negative results for radio wave heating of an underdense ionosphere. Overdense heating produced striations in the ionosphere which may cause severe radio frequency interference problems under certain conditions. The effects of thermal self-focusing are shown to be limited severely geographically. The aspect sensitivity of field-aligned striations makes interference-free regions above magnetic latitude about 60 deg. A test program is proposed to simulate the interaction of the SPS beam with the ionosphere, to measure the effects of the interaction on the ionosphere and on communication and navigation systems, and to interpret the results.

Microwave Photonic Architecture for Direction Finding of LPI Emitters: Post-Processing for Angle of Arrival Estimation

DTIC Science & Technology

2016-09-01

mean- square (RMS) error of 0.29° at ə° resolution. For a P4 coded signal, the RMS error in estimating the AOA is 0.32° at 1° resolution. 14...FMCW signal, it was demonstrated that the system is capable of estimating the AOA with a root-mean- square (RMS) error of 0.29° at ə° resolution. For a...Modulator PCB printed circuit board PD photodetector RF radio frequency RMS root-mean- square xvi THIS PAGE INTENTIONALLY LEFT BLANK xvii

Global ionospheric effects of geomagnetic storm on May 2-3, 2010 and their influence on HF radio wave propagation

NASA Astrophysics Data System (ADS)

Kotova, Daria; Klimenko, Maxim; Klimenko, Vladimir; Zakharov, Veniamin

2013-04-01

In this work we have investigated the global ionospheric response to geomagnetic storm on May 2-3, 2010 using GSM TIP (Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere) simulation results. In the GSM TIP storm time model runs, several input parameters such as cross-polar cap potential difference and R2 FAC (Region 2 Field-Aligned Currents) varied as a function of the geomagnetic activity AE-index. Current simulation also uses the empirical model of high-energy particle precipitation by Zhang and Paxton. In this model, the energy and energy flux of precipitating electrons depend on a 3 hour Kp-index. We also have included the 30 min time delay of R2 FAC variations with respect to the variations of cross-polar cap potential difference. In addition, we use the ground-based ionosonde data for comparison our model results with observations. We present an analysis of the physical mechanisms responsible for the ionospheric effects of geomagnetic storms. The obtained simulation results are used by us as a medium for HF radio wave propagation at different latitudes in quiet conditions, and during main and recovery phase of a geomagnetic storm. To solve the problem of the radio wave propagation we used Zakharov's (I. Kant BFU) model based on geometric optics. In this model the solution of the eikonal equation for each of the two normal modes is reduced using the method of characteristics to the integration of the six ray equation system for the coordinates and momentum. All model equations of this system are solved in spherical geomagnetic coordinate system by the Runge-Kutta method. This model was tested for a plane wave in a parabolic layer. In this study, the complex refractive indices of the ordinary and extraordinary waves at ionospheric heights was calculated for the first time using the global first-principal model of the thermosphere-ionosphere system that describes the parameters of an inhomogeneous anisotropic medium during a geomagnetic storm. A comparison of the ordinary and extraordinary modes of HF radio ray paths in quiet and disturbed conditions has been done. We considered in more detail the features of the radio ray paths in the presence of F3 layer in the equatorial ionosphere, the main ionospheric trough and tongue of ionization at high latitudes. It is shown that the results obtained with use of radio propagation and GSM TIP models adequately describe HF radio ray paths in the Earth's ionosphere and can be used in applications. These investigations were carried out at financial support of Russian Foundation for Basic Research (RFBR) - Grant # 12-05-31217 and RAS Program 22.

The FIELDS Instrument Suite for Solar Probe Plus Measuring the Coronal Plasma and Magnetic Field, Plasma Waves and Turbulence, and Radio Signatures of Solar Transients

NASA Technical Reports Server (NTRS)

Bale, S. D.; Goetz, K.; Harvey, P. R.; Turin, P.; Bonnell, J. W.; Dudok de Wit, T.; Ergun, R. E.; MacDowall, R. J.; Pulupa, M.; Choi, M. K.;

The FIELDS Instrument Suite for Solar Probe Plus: Measuring the Coronal Plasma and Magnetic Field, Plasma Waves and Turbulence, and Radio Signatures of Solar Transients.

PubMed

Bale, S D; Goetz, K; Harvey, P R; Turin, P; Bonnell, J W; de Wit, T Dudok; Ergun, R E; MacDowall, R J; Pulupa, M; Andre, M; Bolton, M; Bougeret, J-L; Bowen, T A; Burgess, D; Cattell, C A; Chandran, B D G; Chaston, C C; Chen, C H K; Choi, M K; Connerney, J E; Cranmer, S; Diaz-Aguado, M; Donakowski, W; Drake, J F; Farrell, W M; Fergeau, P; Fermin, J; Fischer, J; Fox, N; Glaser, D; Goldstein, M; Gordon, D; Hanson, E; Harris, S E; Hayes, L M; Hinze, J J; Hollweg, J V; Horbury, T S; Howard, R A; Hoxie, V; Jannet, G; Karlsson, M; Kasper, J C; Kellogg, P J; Kien, M; Klimchuk, J A; Krasnoselskikh, V V; Krucker, S; Lynch, J J; Maksimovic, M; Malaspina, D M; Marker, S; Martin, P; Martinez-Oliveros, J; McCauley, J; McComas, D J; McDonald, T; Meyer-Vernet, N; Moncuquet, M; Monson, S J; Mozer, F S; Murphy, S D; Odom, J; Oliverson, R; Olson, J; Parker, E N; Pankow, D; Phan, T; Quataert, E; Quinn, T; Ruplin, S W; Salem, C; Seitz, D; Sheppard, D A; Siy, A; Stevens, K; Summers, D; Szabo, A; Timofeeva, M; Vaivads, A; Velli, M; Yehle, A; Werthimer, D; Wygant, J R

2016-12-01

NASA's Solar Probe Plus (SPP) mission will make the first in situ measurements of the solar corona and the birthplace of the solar wind. The FIELDS instrument suite on SPP will make direct measurements of electric and magnetic fields, the properties of in situ plasma waves, electron density and temperature profiles, and interplanetary radio emissions, amongst other things. Here, we describe the scientific objectives targeted by the SPP/FIELDS instrument, the instrument design itself, and the instrument concept of operations and planned data products.

The FIELDS Instrument Suite for Solar Probe Plus. Measuring the Coronal Plasma and Magnetic Field, Plasma Waves and Turbulence, and Radio Signatures of Solar Transients

NASA Astrophysics Data System (ADS)

Bale, S. D.; Goetz, K.; Harvey, P. R.; Turin, P.; Bonnell, J. W.; Dudok de Wit, T.; Ergun, R. E.; MacDowall, R. J.; Pulupa, M.; Andre, M.; Bolton, M.; Bougeret, J.-L.; Bowen, T. A.; Burgess, D.; Cattell, C. A.; Chandran, B. D. G.; Chaston, C. C.; Chen, C. H. K.; Choi, M. K.; Connerney, J. E.; Cranmer, S.; Diaz-Aguado, M.; Donakowski, W.; Drake, J. F.; Farrell, W. M.; Fergeau, P.; Fermin, J.; Fischer, J.; Fox, N.; Glaser, D.; Goldstein, M.; Gordon, D.; Hanson, E.; Harris, S. E.; Hayes, L. M.; Hinze, J. J.; Hollweg, J. V.; Horbury, T. S.; Howard, R. A.; Hoxie, V.; Jannet, G.; Karlsson, M.; Kasper, J. C.; Kellogg, P. J.; Kien, M.; Klimchuk, J. A.; Krasnoselskikh, V. V.; Krucker, S.; Lynch, J. J.; Maksimovic, M.; Malaspina, D. M.; Marker, S.; Martin, P.; Martinez-Oliveros, J.; McCauley, J.; McComas, D. J.; McDonald, T.; Meyer-Vernet, N.; Moncuquet, M.; Monson, S. J.; Mozer, F. S.; Murphy, S. D.; Odom, J.; Oliverson, R.; Olson, J.; Parker, E. N.; Pankow, D.; Phan, T.; Quataert, E.; Quinn, T.; Ruplin, S. W.; Salem, C.; Seitz, D.; Sheppard, D. A.; Siy, A.; Stevens, K.; Summers, D.; Szabo, A.; Timofeeva, M.; Vaivads, A.; Velli, M.; Yehle, A.; Werthimer, D.; Wygant, J. R.

2016-12-01

NASA's Solar Probe Plus (SPP) mission will make the first in situ measurements of the solar corona and the birthplace of the solar wind. The FIELDS instrument suite on SPP will make direct measurements of electric and magnetic fields, the properties of in situ plasma waves, electron density and temperature profiles, and interplanetary radio emissions, amongst other things. Here, we describe the scientific objectives targeted by the SPP/FIELDS instrument, the instrument design itself, and the instrument concept of operations and planned data products.

Equatorial Oscillations in Jupiter's and Saturn's Atmospheres

NASA Technical Reports Server (NTRS)

Flasar, F. Michael; Guerlet, S.; Fouchet, T.; Schinder, P. J.

2011-01-01

Equatorial oscillations in the zonal-mean temperatures and zonal winds have been well documented in Earth's middle atmosphere. A growing body of evidence from ground-based and Cassini spacecraft observations indicates that such phenomena also occur in the stratospheres of Jupiter and Saturn. Earth-based midinfrared measurements spanning several decades have established that the equatorial stratospheric temperatures on Jupiter vary with a cycle of 4-5 years and on Saturn with a cycle of approximately 15 years. Spectra obtained by the Composite Infrared Spectrometer (CIRS) during the Cassini swingby at the end of 2000, with much better vertical resolution than the ground-based data, indicated a series of vertically stacked warm and cold anomalics at Jupiter's equator; a similar structurc was seen at Saturn's equator in CIRS limb measurements made in 2005, in the early phase of Cassini's orbital tour. The thermal wind equation implied similar patterns of mean zonal winds increasing and decreasing with altitude. On Saturn the peak-to-pcak amplitude of this variation was nearly 200 meters per second. The alternating vertical pattern of wanner and colder cquatorial tcmperatures and easterly and westerly tendencies of the zonal winds is seen in Earth's equatorial oscillations, where the pattern descends with time, The Cassini Jupiter and early Saturn observations were snapshots within a limited time interval, and they did not show the temporal evolution of the spatial patterns. However, more recent Saturn observations by CIRS (2010) and Cassini radio-occultation soundings (2009-2010) have provided an opportunity to follow the change of the temperature-zonal wind pattern, and they suggest there is descent, at a rate of roughly one scale height over four years. On Earth, the observed descent in the zonal-mean structure is associated with the absorption of a combination of vertically propagating waves with easlerly and westerly phase velocities. The peak-to-peak zonal wind amplitude in the oscillation pattern and the rate of descent constrain the absorbed wave flux of zonal momentum. On Saturn this is approximately 0.05 square meters per square seconds, which is comparable to if not greater than that associated with the terrestrial oscillations. We discuss possible candidates for the absorbed waves on Saturn. On Earth the wave forcing of the equatorial oscillation generales secondary circulations that can affcct the temperature and wind structure at latitudes well away from the equator, and we discuss possible evidence of that on Saturn.

Reflected ray retrieval from radio occultation data using radio holographic filtering of wave fields in ray space

NASA Astrophysics Data System (ADS)

Gorbunov, Michael E.; Cardellach, Estel; Lauritsen, Kent B.

2018-03-01

Linear and non-linear representations of wave fields constitute the basis of modern algorithms for analysis of radio occultation (RO) data. Linear representations are implemented by Fourier Integral Operators, which allow for high-resolution retrieval of bending angles. Non-linear representations include Wigner Distribution Function (WDF), which equals the pseudo-density of energy in the ray space. Representations allow for filtering wave fields by suppressing some areas of the ray space and mapping the field back from the transformed space to the initial one. We apply this technique to the retrieval of reflected rays from RO observations. The use of reflected rays may increase the accuracy of the retrieval of the atmospheric refractivity. Reflected rays can be identified by the visual inspection of WDF or spectrogram plots. Numerous examples from COSMIC data indicate that reflections are mostly observed over oceans or snow, in particular over Antarctica. We introduce the reflection index that characterizes the relative intensity of the reflected ray with respect to the direct ray. The index allows for the automatic identification of events with reflections. We use the radio holographic estimate of the errors of the retrieved bending angle profiles of reflected rays. A comparison of indices evaluated for a large base of events including the visual identification of reflections indicated a good agreement with our definition of reflection index.

Space-atmospheric interactions of energetic cosmic rays

NASA Astrophysics Data System (ADS)

Isar, Paula Gina

2015-02-01

Ultra-high energy cosmic rays are the most energetic particles in the Universe of which origin still remain a mystery since a century from their descovery. They are unique messengers coming from far beyond our Milky Way Galaxy, which provides insights into the fundamental matter, energy, space and time. As subatomic particles flying through space to nearly light speed, the ultra-high energy cosmic rays are so rare that they strike the Earth's atmosphere at a rate of up to only one particle per square kilometer per year or century. While the atmosphere is used as a giant calorimeter where cosmic rays induced air showers are initiated and the medium through which Cherenkov or fluorescence light or radio waves propagate, all cosmic ray measurements (performed either from space or ground) rely on an accurate atmospheric monitoring and understanding of atmospheric effects. The interdisciplinary link between Astroparticle Physics and Atmospheric Environment through the ultra-high energy comic rays space - atmospheric interactions, based on the present ground- and future space-based cosmic ray observatories, will be presented.

Generation of complex motor patterns in american grasshopper via current-controlled thoracic electrical interfacing.

PubMed

Giampalmo, Susan L; Absher, Benjamin F; Bourne, W Tucker; Steves, Lida E; Vodenski, Vassil V; O'Donnell, Peter M; Erickson, Jonathan C

2011-01-01

Micro-air vehicles (MAVs) have attracted attention for their potential application to military applications, environmental sensing, and search and rescue missions. While progress is being made toward fabrication of a completely human-engineered MAV, another promising approach seeks to interface to, and take control of, an insect's nervous system. Cyborg insects take advantage of their innate exquisite loco-motor, navigation, and sensing abilities. Recently, several groups have demonstrated the feasibility of radio-controlled flight in the hawkmoth and beetle via electrical neural interfaces. Here, we report a method for eliciting the "jump" response in the American grasshopper (S. Americana). We found that stimulating the metathoracic T3 ganglion with constant-current square wave pulses with amplitude 186 ± 40 μA and frequency 190 ± 13 Hz reproducibly evoked (≥95% success rate) the desired motor activity in N=3 test subjects. To the best of our knowledge, this is the first report of an insect cyborg with a synchronous neuromuscular system.

How Expanded Ionospheres of Hot Jupiters Can Prevent Escape of Radio Emission Generated by the Cyclotron Maser Instability

NASA Astrophysics Data System (ADS)

Weber, Christof; Lammer, Helmut; Shaikhislamov, Ildar F.; Erkaev, Nikolai; Chadney, Joshua M.; Khodachenko, Maxim L.; Grießmeier, Jean-Mathias; Rucker, Helmut O.; Vocks, Christian; Macher, Wolfgang; Odert, Petra; Kislyakova, Kristina G.

2017-04-01

We present a study of the plasma conditions in the atmospheres of the Hot Jupiters HD 209458b and HD 189733b and for an HD 209458b-like planet at orbit locations between 0.2-1 AU around a Sun-like star. We discuss how these conditions influence the radio emission we expect from their planetary magnetospheres. We find that the environmental conditions for the cyclotron maser instability (CMI), the process which is responsible for the generation of radio waves at magnetic planets in the solar system, most likely will not operate at Hot Jupiters. The reason for that is that hydrodynamically expanding atmospheres possess extended ionospheres whose plasma densities within the magnetosphere are so large that the plasma frequency is much higher than the cyclotron frequency, which contradicts the necessary condition for the production of radio emission and prevents the escape of radio waves from close-in extrasolar planets at distances <0.05 AU from a Sun-like host star. The upper atmosphere structure of Hot Jupiters around stars similar to the Sun changes between 0.2 and 0.5 AU from the hydrodynamic to a hydrostatic regime and this results in conditions similar to solar system planets with a region of depleted plasma between the exobase and the magnetopause where the plasma frequency can be lower than the cyclotron frequency. In such an environment a beam of highly energetic electrons accelerated along the field lines towards the planet can produce radio emission. However, even if the CMI could operate the extended ionospheres of Hot Jupiters are too dense to let the radio emission escape from the planets. We also investigate the possible radio emission of the Hot Jupiter Tau Bootis b by placing it at different orbital distances from the host star, i.e. 0.1 and 0.2 AU. In particular we check if the atmosphere of Tau Bootis b at 0.046 AU is in the hydrostatic or in the hydrodynamic regime. If it is in the hydrodynamic regime it's ionosphere is extended and will constitute an obstacle for possibly generated radio waves or the generation via the Cyclotron Maser Instability (CMI) might even be prevented completely. Furthermore we investigate at which orbital location the atmosphere undergoes the transformation from hydrodynamic to hydrostatic, i.e. the transformation to more favourable conditions for the CMI.

Illuminating Gravitational Waves

NASA Astrophysics Data System (ADS)

Kasliwal, Mansi; GROWTH (Global Relay of Observatories Watching Transients Happen) Team

2018-01-01

On August 17 2017, for the first time, an electromagnetic counterpart to gravitational waves was detected. Two neutron stars merged and lit up the entire electromagnetic spectrum, from gamma-rays to the radio. The infrared signature vividly demonstrates that neutron star mergers are indeed the long-sought production sites that forge heavy elements by r-process nucleosynthesis. The weak gamma-rays are dissimilar to classical short gamma-ray bursts with ultra-relativistic jets. Instead, by synthesizing a panchromatic dataset, we suggest that break-out of a wide-angle, mildly-relativistic cocoon engulfing the jet elegantly explains the low-luminosity gamma-rays, the high-luminosity ultraviolet-optical-infrared and the delayed radio/X-ray emission. I conclude with the promise of a literally bright and loud future, thanks to even more sensitive survey telescopes and gravitational wave interferometers.

The Dynamic Radio Sky: Future Directions at cm/m-Wavelengths

NASA Astrophysics Data System (ADS)

Bower, Geoffrey C.; Cordes, J.; Croft, S.; Lazio, J.; Lorimer, D.; McLaughlin, M.

2009-01-01

The time domain of the radio wavelength sky has been only sparsely explored. Nevertheless, recent discoveries from limited surveys and serendipitous discoveries indicate that there is much to be found on timescales from nanoseconds to years and at wavelengths from meters to millimeters. These observations have revealed unexpected phenonmena such as rotating radio transients and coherent pulses from brown dwarfs. Additionally, archival studies have revealed an unknown class of radio transients without radio, optical, or high-energy hosts. The current generation of new meter- and centimeter-wave radio telescopes such as the MWA, LWA, PAPER, and ATA will exploit wide fields of view and flexible digital signal processing to systematically explore radio transient parameter space, as well as lay the scientific and technical foundation for the SKA. Known unknowns that will be the target of future transient surveys include orphan gamma-ray burst afterglows, radio supernovae, tidally-disrupted stars, flare stars, and magnetars.

Waves in the Mesosphere of Venus as seen by the Venus Express Radio Science Experiment VeRa

NASA Astrophysics Data System (ADS)

Tellmann, Silvia; Häusler, B.; Hinson, D. P.; Tyler, G.; Andert, T. P.; Bird, M. K.; Imamura, T.; Pätzold, M.; Remus, S.

2013-10-01

The Venus Express Radio Science Experiment (VeRa) has retrieved more than 700 profiles of the mesosphere and troposphere of Venus. These profiles cover a wide range of latitudes and local times, enabling study of atmospheric wave phenomena over a range spatial scales at altitudes of 40-90 km. In addition to quasi-horizontal waves and eddies on near planetary scales, diurnally forced eddies and thermal tides, small-scale gravity waves, and turbulence play a significant role in the development and maintenance of atmospheric super-rotation. Small-scale temperature variations with vertical wavelengths of 4 km or less have wave amplitudes reaching TBD km in the stable atmosphere above the tropopause, in contrast with much weaker temperature perturbations observed in the middle cloud layer below. The strength of gravity waves increases with latitude in both hemispheres. The results suggest that convection at low latitudes and topographical forcing at high northern latitudes—possibly in combination with convection and/or Kelvin-Helmholtz instabilities—play key roles in the genesis of gravity waves. Further, thermal tides also play an important role in the mesosphere. Diurnal and semi-diurnal wave modes are observed at different latitudes and altitudes. The latitudinal and height dependence of the thermal tide modes will be investigated.

Phase Coupling in Langmuir Wave Packets: Evidence for Four Wave Interactions in Solar Type III Radio Bursts

NASA Technical Reports Server (NTRS)

Thejappa, G.; MacDowall, R. J.; Bergamo, M.

2012-01-01

The four wave interaction process, known as the oscillating two stream instability (OTSI) is considered as one of the mechanisms responsible for stabilizing the electron beams associated with solar type III radio bursts. It has been reported that (1) an intense localized Langmuir wave packet associated with a type III burst contains the spectral characteristics of the OTSI: (a) a resonant peak at the local electron plasma frequency, f(sub pe), (b) a Stokes peak at a frequency slightly lower than f(sub pe), (c) anti-Stokes peak at a frequency slightly higher than f(sub pe), and (d) a low frequency enhancement below a few hundred Hz, (2) the frequencies and wave numbers of these spectral components satisfy the resonance conditions of the OTSI, and (3) the peak intensity of the wave packet is well above the thresholds for the OTSI as well as spatial collapse of envelope solitons. Here, for the first time, applying the trispectral analysis on this wave packet, we show that the tricoherence, which measures the degree of coherent four-wave coupling amongst the observed spectral components exhibits a peak. This provides an additional evidence for the OTSI and related spatial collapse of Langmuir envelope solitons in type III burst sources.

New Astrometric Limits on the Stochastic Gravitational Wave Background

NASA Astrophysics Data System (ADS)

Darling, Jeremiah K.; Truebenbach, Alexandra; Paine, Jennie

2018-06-01

We present new limits on the low frequency (f < 10-8 Hz) stochastic gravitational wave background using correlated extragalactic proper motions. The familiar methods for gravitational wave detection are ground- and space-based laser interferometry, pulsar timing, and polarization of the cosmic microwave background. Astrometry offers an additional path to gravitational wave detection because gravitational waves deflect the light rays of extragalactic objects, creating apparent proper motions in a quadrupolar (and higher order modes) pattern. Astrometry is sensitive to gravitational waves with frequencies between roughly 10-18 Hz and 10-8 Hz (between H0 and 1/3 yr-1), which overlaps and bridges the pulsar timing and CMB polarization regimes. We present the methods and results of two complementary approaches to astrometric gravitational wave detection: (1) a small ~500-object radio interferometric sample with low per-source proper motion uncertainty but large intrinsic proper motions caused by radio jets, and (2) a thousand-fold larger sample with large per-source uncertainties that has small intrinsic proper motions (Gaia active galactic nuclei). Both approaches produce limits on ΩGW, the energy density of gravitational waves as a fraction of the cosmological critical energy density.The authors acknowledge support from the NSF grant AST-1411605 and the NASA grant 14-ATP14-0086.

A Deep Space Network Portable Radio Science Receiver

NASA Technical Reports Server (NTRS)

Jongeling, Andre P.; Sigman, Elliott H.; Chandra, Kumar; Trinh, Joseph T.; Navarro, Robert; Rogstad, Stephen P.; Goodhart, Charles E.; Proctor, Robert C.; Finley, Susan G.; White, Leslie A.

2009-01-01

The Radio Science Receiver (RSR) is an open-loop receiver installed in NASA s Deep Space Network (DSN), which digitally filters and records intermediate-frequency (IF) analog signals. The RSR is an important tool for the Cassini Project, which uses it to measure perturbations of the radio-frequency wave as it travels between the spacecraft and the ground stations, allowing highly detailed study of the composition of the rings, atmosphere, and surface of Saturn and its satellites.

STS-56 MS1 Foale uses SAREX on forward flight deck of Discovery, OV-103

NASA Image and Video Library

1993-04-17

STS056-30-001 (8-17 April 1993) --- Aboard Discovery, astronaut C. Michael Foale, (call letters KB5UAC), talks to amateur radio operators on Earth via the Shuttle Amateur Radio Experiment (SAREX). SAREX was established by NASA, the American Radio League/Amateur Radio Satellite Corporation and the Johnson Space Center Amateur Radio Club to encourage public participation in the space program through an endeavor to demonstrate the effectiveness of conducting short-wave radio transmissions. These transmissions occur between the Shuttle and ground-based radio operators at low cost ground stations with amateur and digital techniques. As on several previous missions, SAREX was used on this flight as an educational opportunity for students around the world to learn about space firsthand by speaking directly to astronauts aboard the Shuttle.

Method and apparatus for radio frequency ceramic sintering

DOEpatents

Hoffman, Daniel J.; Kimrey, Jr., Harold D.

1993-01-01

Radio frequency energy is used to sinter ceramic materials. A coaxial waveguide resonator produces a TEM mode wave which generates a high field capacitive region in which a sample of the ceramic material is located. Frequency of the power source is kept in the range of radio frequency, and preferably between 60-80 MHz. An alternative embodiment provides a tunable radio frequency circuit which includes a series input capacitor and a parallel capacitor, with the sintered ceramic connected by an inductive lead. This arrangement permits matching of impedance over a wide range of dielectric constants, ceramic volumes, and loss tangents.

Method and apparatus for radio frequency ceramic sintering

DOEpatents

Hoffman, D.J.; Kimrey, H.D. Jr.

1993-11-30

Radio frequency energy is used to sinter ceramic materials. A coaxial waveguide resonator produces a TEM mode wave which generates a high field capacitive region in which a sample of the ceramic material is located. Frequency of the power source is kept in the range of radio frequency, and preferably between 60-80 MHz. An alternative embodiment provides a tunable radio frequency circuit which includes a series input capacitor and a parallel capacitor, with the sintered ceramic connected by an inductive lead. This arrangement permits matching of impedance over a wide range of dielectric constants, ceramic volumes, and loss tangents. 6 figures.

Voyager 1 Planetary Radio Astronomy Observations Near Jupiter

NASA Technical Reports Server (NTRS)

Warwick, J. W.; Pearce, J. B.; Riddle, A. C.; Alexander, J. K.; Desch, M. D.; Kaiser, M. L.; Thieman, J. R.; Carr, T. B.; Gulkis, S.; Boischot, A.

1979-01-01

Results are reported from the first low frequency radio receiver to be transported into the Jupiter magnetosphere. Dramatic new information was obtained both because Voyager was near or in Jupiter's radio emission sources and also because it was outside the relatively dense solar wind plasma of the inner solar system. Extensive radio arcs, from above 30 MHz to about 1 MHz, occurred in patterns correlated with planetary longitude. A newly discovered kilometric wavelength radio source may relate to the plasma torus near Io's orbit. In situ wave resonances near closest approach define an electron density profile along the Voyager trajectory and form the basis for a map of the torus. Studies in progress are outlined briefly.

Effect of current on spectrum of breaking waves in water of finite depth

NASA Technical Reports Server (NTRS)

Tung, C. C.; Huang, N. E.

1987-01-01

This paper presents an approximate method to compute the mean value, the mean square value and the spectrum of waves in water of finite depth taking into account the effect of wave breaking with or without the presence of current. It is assumed that there exists a linear and Gaussian ideal wave train whose spectrum is first obtained using the wave energy flux balance equation without considering wave breaking. The Miche wave breaking criterion for waves in finite water depth is used to limit the wave elevation and establish an expression for the breaking wave elevation in terms of the elevation and its second time derivative of the ideal waves. Simple expressions for the mean value, the mean square value and the spectrum are obtained. These results are applied to the case in which a deep water unidirectional wave train, propagating normally towards a straight shoreline over gently varying sea bottom of parallel and straight contours, encounters an adverse steady current whose velocity is assumed to be uniformly distributed with depth. Numerical results are obtained and presented in graphical form.

Transient Phenomena: Opportunities for New Discoveries

NASA Technical Reports Server (NTRS)

Lazio, T. Joseph W.

2010-01-01

Known classes of radio wavelength transients range from the nearby (stellar flares and radio pulsars) to the distant Universe (gamma-ray burst afterglows). Hypothesized classes of radio transients include analogs of known objects, such as extrasolar planets emitting Jovian-like radio bursts and giant-pulse emitting pulsars in other galaxies, to the exotic, such as prompt emission from gamma-ray bursts, evaporating black holes and transmitters from other civilizations. Time domain astronomy has been recognized internationally as a means of addressing key scientific questions in astronomy and physics, and pathfinders and Precursors to the Square Kilometre Array (SKA) are beginning to offer a combination of wider fields of view and more wavelength agility than has been possible in the past. These improvements will continue when the SKA itself becomes operational. I illustrate the range of transient phenomena and discuss how the detection and study of radio transients will improve immensely.

Facilitating Heliophysics Research by the Virtual Wave Observatory (VWO) Context Data Search Capability

NASA Technical Reports Server (NTRS)

Fung, Shing F.; Shao, Xi; Garcia, Leonard N.; Galkin, Ivan A.; Benson, Robert F.

2009-01-01

Wave phenomena, ranging from freely propagating electromagnetic radiation (e.g., solar radio bursts, AKR) to plasma wave modes trapped in various plasma regimes (e.g., whistlers, Langmuir and ULF waves) and atmospheric gravity waves, are ubiquitous in the heliosphere. Because waves can propagate, wave data obtained at a given observing location may pertain to wave oscillations generated locally or from afar. While wave data analysis requires knowledge of wave characteristics specific to different wave modes, the search for appropriate data for heliophysics wave studies also requires knowledge of wave phenomena. In addition to deciding whether the interested wave activity is electrostatic (i.e., locally trapped) or electromagnetic (with propagation over distances), considerations must be given to the dependence of the wave activity on observer's location or viewing geometry, propagating frequency range and whether the wave data were acquired by passive or active observations. Occurances of natural wave emissions i the magnetosphere (e.g, auroral kilometric radiation) are often dependent also on the state (e.e., context) of the magnetosphere that varies with the changing solar wind, IMF and geomagnetic conditions. Fung and Shao [2008] showed recently that magnetospheric state can be specified by a set of suitably time-shifted solar wind, IMF and the multi-scale geomagnetic response parameters. These parameters form a magnetospheric state vector that provides the basis for searching magnetospheric wave data by their context conditions. Using the IMAGE Radio Plasma Imager (RPI) data and the NASA Magnetospheric State Query System (MSOS) [Fung, 2004], this presentation demonstrates the VWO context data search capability under development and solicits feedback from the Heliophysics research community for improvements.

High frame rate imaging system for limited diffraction array beam imaging with square-wave aperture weightings.

PubMed

Lu, Jian-Yu; Cheng, Jiqi; Wang, Jing

2006-10-01

A general-purpose high frame rate (HFR) medical imaging system has been developed. This system has 128 independent linear transmitters, each of which is capable of producing an arbitrary broadband (about 0.05-10 MHz) waveform of up to +/- 144 V peak voltage on a 75-ohm resistive load using a 12-bit/40-MHz digital-to-analog converter. The system also has 128 independent, broadband (about 0.25-10 MHz), and time-variable-gain receiver channels, each of which has a 12-bit/40-MHz analog-to-digital converter and up to 512 MB of memory. The system is controlled by a personal computer (PC), and radio frequency echo data of each channel are transferred to the same PC via a standard USB 2.0 port for image reconstructions. Using the HFR imaging system, we have developed a new limited-diffraction array beam imaging method with square-wave aperture voltage weightings. With this method, in principle, only one or two transmitters are required to excite a fully populated two-dimensional (2-D) array transducer to achieve an equivalent dynamic focusing in both transmission and reception to reconstruct a high-quality three-dimensional image without the need of the time delays of traditional beam focusing and steering, potentially simplifying the transmitter subsystem of an imager. To validate the method, for simplicity, 2-D imaging experiments were performed using the system. In the in vitro experiment, a custom-made, 128-element, 0.32-mm pitch, 3.5-MHz center frequency linear array transducer with about 50% fractional bandwidth was used to reconstruct images of an ATS 539 tissue-mimicking phantom at an axial distance of 130 mm with a field of view of more than 90 degrees. In the in vivo experiment of a human heart, images with a field of view of more than 90 degrees at 120-mm axial distance were obtained with a 128-element, 2.5-MHz center frequency, 0.15-mm pitch Acuson V2 phased array. To ensure that the system was operated under the limits set by the U.S. Food and Drug Administration, the mechanical index, thermal index, and acoustic output were measured. Results show that higher-quality images can be reconstructed with the square-wave aperture weighting method due to an increased penetration depth as compared to the exact weighting method developed previously, and a frame rate of 486 per second was achieved at a pulse repetition frequency of about 5348 Hz for the human heart.

Multi-dynamic range compressional wave detection using optical-frequency comb

NASA Astrophysics Data System (ADS)

Minamikawa, Takeo; Masuoka, Takashi; Oe, Ryo; Nakajima, Yoshiaki; Yamaoka, Yoshihisa; Minoshima, Kaoru; Yasui, Takeshi

2018-02-01

Compressional wave detection is useful means for health monitoring of building, detection of abnormal vibration of moving objects, defect evaluation, and biomedical imaging such as echography and photoacoustic imaging. The frequency of the compressional wave is varied from quasi-static to a few tens of megahertz depending on applications. Since the dynamic range of general compressional wave detectors is limited, we need to choose a proper compressional wave detector depending on applications. For the compressional wave detection with wide dynamic range, two or more detectors with different detection ranges is required. However, these detectors with different detection ranges generally has different accuracy and precision, disabling the seamless detection over these detection ranges. In this study, we proposed a compressional wave detector employing optical frequency comb (OFC). The compressional wave was sensed with a part of an OFC cavity, being encoded into OFC. The spectrally encoded OFC was converted to radio-frequency by the frequency link nature of OFC. The compressional wave-encoded radio-frequency can therefore be directly measured with a high-speed photodetector. To enhance the dynamic range of the compressional wave detection, we developed a cavityfeedback-based system and a phase-sensitive detection system, both of which the accuracy and precision are coherently linked to these of the OFC. We provided a proof-of-principle demonstration of the detection of compressional wave from quasi-static to ultrasound wave by using the OFC-based compressional wave sensor. Our proposed approach will serve as a unique and powerful tool for detecting compressional wave versatile applications in the future.

(abstract) Dynamics of Meteor Trails Deposited in the Equatorial Electrojet

NASA Technical Reports Server (NTRS)

Chapin, Elaine; Kudeki, Erhan

1996-01-01

Previously we reported that the meteor echoes detected at the Jicamarca Radio Observatory exhibit some unusual properties. In summary, the echo durations are very long ..., radio wave scattering is non-specular ..., and the doppler spectra of the scattered signals contain components that are red-shifted ... immediately after the onset of the echoes.

A Depolarization and Attenuation Experiment Using the CTS and COMSTAR Satellites. Mathematical Formulations and Definitions for Dual Polarized Reception of a Wave Passing Through a Depolarizing Medium (A Polarization Primer)

NASA Technical Reports Server (NTRS)

Stutzman, W. L.

1977-01-01

The theoretical fundamentals and mathematical definitions for calculations involved with dual polarized radio links are given. Detailed derivations and results are discussed for several formulations applied to a general dual polarized radio link.

RFID: A Revolution in Automatic Data Recognition

ERIC Educational Resources Information Center

Deal, Walter F., III

2004-01-01

Radio frequency identification, or RFID, is a generic term for technologies that use radio waves to automatically identify people or objects. There are several methods of identification, but the most common is to store a serial number that identifies a person or object, and perhaps other information, on a microchip that is attached to an antenna…

Juno: Morse code "HI" received from Earth

NASA Image and Video Library

2017-03-22

During its close flyby of Earth in 2013, NASA's Jupiter-bound Juno spacecraft listened for -- and heard -- a coordinated, global transmission from amateur radio operators using its radio and plasma wave science instrument. The message said "HI" in Morse code. More details about this sound can be found here: photojournal.jpl.nasa.gov/catalog/PIA17744

The First Wave: The Beginnings of Radio in Canadian Distance Education

ERIC Educational Resources Information Center

Buck, George H.

2006-01-01

This article describes one of the first developments and deployment of radio for distance learning and education in Canada, beginning in the early 1920s. Anticipating a recent initiative of public-private partnerships, the impetus, infrastructure, and initial programs were provided by a large corporation. Description of the system, its purpose,…

A New Peak of Leonids observed by Radio Technics

NASA Astrophysics Data System (ADS)

Suzuki, K.; Maegawa, K.; Minagawa, Y.

Radio meteor observations with amateur ham radio wave have been carried out in Japan since August, 1996, by using forward-scattered meteor echoes of VHF radio waves (53.75MHz, 50W, CW) transmitted in Sabae, Fukui prefecture. A strong activity of Leonids was observed between 22h and 01h on November 16/17 (UT), 1996. The hourly rate of long duration echoes reached over 50 times larger than in non-shower period and 1.2 to 1.5 times larger than that at the normal maximum of Leonids, respectively. This enhanced activity occurred at a solar longitude (SL) of 234.95 plus or minus 0.05 degrees (2000.0 eq.), and is probably different from normal peak of Leonids at 235.45 plus or minus 0.05 degrees(2000.0 eq.) observed in 1990's. A corresponding peak in 1995 was also reported by visual meteor observation by many observers in Japan. The ascending node of Comet Tempel-Tuttle in 1966 was at 235.11 degrees in SL, and is closer to the new peak than the normal one (at 235.45 degrees in SL).

40-Hz square-wave stimulation requires less energy to produce muscle contraction: compared with the TASER® X26 conducted energy weapon.

PubMed

Comeaux, James A; Jauchem, James R; Cox, D Duane; Crane, Carrie C; D'Andrea, John A

2013-07-01

Conducted energy weapons (CEWs) (including the Advanced TASER(®) X26 model produced by TASER International, Inc.) incapacitate individuals by causing muscle contractions. In this study using anesthetized swine, the potential incapacitating effect of primarily monophasic, 19-Hz voltage imposed by the commercial CEW was compared with the effect of voltages imposed by a laboratory device that created 40-Hz square waves. Forces of muscle contraction were measured with the use of strain gauges. Stimulation with 40-Hz square waves required less pulse energy than stimulation with the commercial CEW to produce similar muscle contraction. The square-pulse stimulation, at the higher repetition rate, caused a more complete tetanus at a lower energy. Use of such a simple shape of waveform may be used to make future nonlethal weapon devices more efficient. © 2013 American Academy of Forensic Sciences Published 2013. This article is a U.S. Government work and is in the public domain in the U.S.A.

Radioastronomía: Una Mirada Más Amplia

NASA Astrophysics Data System (ADS)

Bianchi, Viviana

2004-12-01

The existence of the celestial bodies is known due to the light they emit. But light is a small part of a bigger phenomenon known as electromagnetic radiation. The representation of all kinds of electromagnetic radiation as a function of its frequency is called the electromagnetic spectrum. If we only studied the visible part of the spectrum, we would ignore a great deal of information. The celestial bodies emit radiation in all the regions of the electromagnetic spectrum, with very different intensity. To capture these data, astronomers design new types of telescopes that capture radiation at different wavelengths, among them the radiotelescopes that, as the name indicates, detect radio waves. The radiotelescope can be compared to a regular radio set. A radio station sends information by means of radio waves. The radio set captures these waves by means of its antenna, processes it and reproduces the information (music, etc.) in audible form. In the field of radioastronomy, interesting observations can be carried out: radio emission from stars, nebulas, pulsars, distant galaxies and stars, radiogalaxies, the Milky Way, the Sun, Jupiter, etc. La presencia de los cuerpos celestes se conoce gracias a que emiten luz. Pero la luz constituye solo una pequeña parte de un fenómeno mucho mas amplio conocido como radiación electromagnética. La representación de todas las clases de radiación como función de su frecuencia se denomina espectro electromagnético. Si solo estudiáramos la parte visual del espectro ignoraríamos una gran cantidad de información. Los cuerpos celestes emiten radiación en todas las regiones del espectro electromagnético, aunque con muy distinta intensidad. Para captar estos datos, los astrónomos deben diseñar nuevos tipos de telescopios que puedan captar la radiación de distintas longitudes de ondas, entre ellos los radiotelescopios, qué como su nombre lo indica detectan ondas de radio. El radiotelescopio puede compararse a un aparato de radio familiar. Una estación emisora está enviando información por medio de ondas de radio. El aparato de radio capta estas ondas mediante su antena, la procesa y el receptor reproduce la información (música, etc.) en forma audible. En el campo de la radioastronomía se pueden realizar observaciones interesantes: Radioestrellas, nebulosas, púlsares, galaxias y estrellas lejanas, radiogalaxias, la Vía Láctea, el Sol, Júpiter, etc.

STS-65 Commander Cabana with SAREX-II on Columbia's, OV-102's, flight deck

NASA Image and Video Library

1994-07-23

STS065-44-014 (8-23 July 1994) --- Astronaut Robert D. Cabana, mission commander, is seen on the Space Shuttle Columbia's flight deck with the Shuttle Amateur Radio Experiment (SAREX). SAREX was established by NASA, the American Radio League/Amateur Radio Satellite Corporation and the Johnson Space Center (JSC) Amateur Radio Club to encourage public participation in the space program through a project to demonstrate the effectiveness of conducting short-wave radio transmissions between the Shuttle and ground-based radio operators at low-cost ground stations with amateur and digital techniques. As on several previous missions, SAREX was used on this flight as an educational opportunity for students around the world to learn about space firsthand by speaking directly to astronauts aboard the Shuttle.

STS-56 Commander Cameron uses SAREX on OV-103's aft flight deck

NASA Image and Video Library

1993-04-17

STS056-30-022 (8-17 April 1993) --- Aboard Discovery, astronaut Kenneth D. Cameron (call letters N5AWP), talks to amateur radio operators on Earth via the Shuttle Amateur Radio Experiment (SAREX). SAREX was established by NASA, the American Radio League\\Amateur Satellite Corporation and the Johnson Space Center Amateur Radio Club to encourage public participation in the space program. It is part of an endeavor to demonstrate the effectiveness of conducting short-wave radio transmissions between the Shuttle and ground-based radio operators at low cost ground stations with amateur and digital techniques. As on several previous missions, SAREX was used on this flight as an educational opportunity for students around the world to learn about space firsthand by speaking directly to astronauts aboard the Shuttle.

VLA Detects Unexplained Radio Emission From Three Brown Dwarfs

NASA Astrophysics Data System (ADS)

2005-01-01

Astronomers have discovered three brown dwarfs -- enigmatic objects that are neither stars nor planets -- emitting radio waves that scientists cannot explain. The three newly-discovered radio-emitting brown dwarfs were found as part of a systematic study of nearby brown dwarfs using the National Science Foundation's Very Large Array (VLA) radio telescope. The VLA The Very Large Array CREDIT: NRAO/AUI/NSF (Click on image for VLA gallery) Until 2001, scientists believed that brown dwarfs, which are intermediate in mass between stars and planets, could not emit detectable amounts of radio waves. That year, summer students at the VLA made the first discovery of radio emission from a brown dwarf. Subsequently, as many as a half- dozen more radio-emitting brown dwarfs were discovered. "It clearly had become time to make a systematic study and try to find out just what percentage of brown dwarfs are emitting radio waves," said Rachel Osten, an astronomer at the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia. Osten was assisted in the project in the summer of 2004 by Lynnae Quick, a student at North Carolina Agricultural and Technical State University; Tim Bastian, also an astronomer at NRAO; and Suzanne Hawley, an astronomer at the University of Washington. The research team presented their results to the American Astronomical Society's meeting in San Diego, CA. The three new detections of radio-emitting brown dwarfs are just the first results from the systematic study, which aims to observe all the known brown dwarfs within about 45 light-years of Earth. "We want to be able to say definitively just how common radio emission is among brown dwarfs," Osten explained. The study involves observing 65 individual brown dwarfs, so these new detections represent just the beginning of the results expected from the study. Brown dwarfs are too big to be planets but too small to be true stars, as they have too little mass to trigger hydrogen fusion reactions at their cores, the source of the energy output in larger stars. With roughly 15 to 80 times the mass of Jupiter, the largest planet in our Solar System, brown dwarfs had long been thought to exist, but proved difficult to find. Astronomers found the first brown dwarf in 1995, and a few hundred now are known. The type of radio emission seen in the brown dwarfs arises in more-massive stars as a result of plasma interacting with the star's magnetic field. However, astronomers have noted that this type of activity declines in less-massive stars. This is why they expected brown dwarfs, with masses less than that of any star, to lack radio emission. Surprisingly, based on discoveries since 2001, it now appears that radio-emitting magnetic activity may actually become more common in these very low-mass objects. "We don't have an explanation for this," Osten said. The scientists hope that brown-dwarf radio emission may give them a new tool for analysis. "Since both stars and the planets in our Solar System produce radio emission, detailed study of the radio emission properties of these brown dwarfs may enable us to distinguish where the boundary between stellar and planetary behavior occurs in these not-quite-stars, not-quite-planets," Osten explained. The National Radio Astronomy Observatory is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.

Pulsar Timing Array Based Search for Supermassive Black Hole Binaries in the Square Kilometer Array Era

NASA Astrophysics Data System (ADS)

Wang, Yan; Mohanty, Soumya D.

2017-04-01

The advent of next generation radio telescope facilities, such as the Square Kilometer Array (SKA), will usher in an era where a pulsar timing array (PTA) based search for gravitational waves (GWs) will be able to use hundreds of well timed millisecond pulsars rather than the few dozens in existing PTAs. A realistic assessment of the performance of such an extremely large PTA must take into account the data analysis challenge posed by an exponential increase in the parameter space volume due to the large number of so-called pulsar phase parameters. We address this problem and present such an assessment for isolated supermassive black hole binary (SMBHB) searches using a SKA era PTA containing 1 03 pulsars. We find that an all-sky search will be able to confidently detect nonevolving sources with a redshifted chirp mass of 1 010 M⊙ out to a redshift of about 28 (corresponding to a rest-frame chirp mass of 3.4 ×1 08 M⊙). We discuss the important implications that the large distance reach of a SKA era PTA has on GW observations from optically identified SMBHB candidates. If no SMBHB detections occur, a highly unlikely scenario in the light of our results, the sky-averaged upper limit on strain amplitude will be improved by about 3 orders of magnitude over existing limits.

Pulsar Timing Array Based Search for Supermassive Black Hole Binaries in the Square Kilometer Array Era.

PubMed

Wang, Yan; Mohanty, Soumya D

2017-04-14

The advent of next generation radio telescope facilities, such as the Square Kilometer Array (SKA), will usher in an era where a pulsar timing array (PTA) based search for gravitational waves (GWs) will be able to use hundreds of well timed millisecond pulsars rather than the few dozens in existing PTAs. A realistic assessment of the performance of such an extremely large PTA must take into account the data analysis challenge posed by an exponential increase in the parameter space volume due to the large number of so-called pulsar phase parameters. We address this problem and present such an assessment for isolated supermassive black hole binary (SMBHB) searches using a SKA era PTA containing 10^{3} pulsars. We find that an all-sky search will be able to confidently detect nonevolving sources with a redshifted chirp mass of 10^{10}  M_{⊙} out to a redshift of about 28 (corresponding to a rest-frame chirp mass of 3.4×10^{8}  M_{⊙}). We discuss the important implications that the large distance reach of a SKA era PTA has on GW observations from optically identified SMBHB candidates. If no SMBHB detections occur, a highly unlikely scenario in the light of our results, the sky-averaged upper limit on strain amplitude will be improved by about 3 orders of magnitude over existing limits.

Long-Term Stability of Radio Sources in VLBI Analysis

NASA Technical Reports Server (NTRS)

Engelhardt, Gerald; Thorandt, Volkmar

2010-01-01

Positional stability of radio sources is an important requirement for modeling of only one source position for the complete length of VLBI data of presently more than 20 years. The stability of radio sources can be verified by analyzing time series of radio source coordinates. One approach is a statistical test for normal distribution of residuals to the weighted mean for each radio source component of the time series. Systematic phenomena in the time series can thus be detected. Nevertheless, an inspection of rate estimation and weighted root-mean-square (WRMS) variations about the mean is also necessary. On the basis of the time series computed by the BKG group in the frame of the ICRF2 working group, 226 stable radio sources with an axis stability of 10 as could be identified. They include 100 ICRF2 axes-defining sources which are determined independently of the method applied in the ICRF2 working group. 29 stable radio sources with a source structure index of less than 3.0 can also be used to increase the number of 295 ICRF2 defining sources.

Galaxy Evolution in the Radio Band: The Role of Star-forming Galaxies and Active Galactic Nuclei

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mancuso, C.; Prandoni, I.; Lapi, A.

We investigate the astrophysics of radio-emitting star-forming galaxies and active galactic nuclei (AGNs) and elucidate their statistical properties in the radio band, including luminosity functions, redshift distributions, and number counts at sub-mJy flux levels, which will be crucially probed by next-generation radio continuum surveys. Specifically, we exploit the model-independent approach by Mancuso et al. to compute the star formation rate functions, the AGN duty cycles, and the conditional probability of a star-forming galaxy to host an AGN with given bolometric luminosity. Coupling these ingredients with the radio emission properties associated with star formation and nuclear activity, we compute relevant statisticsmore » at different radio frequencies and disentangle the relative contribution of star-forming galaxies and AGNs in different radio luminosity, radio flux, and redshift ranges. Finally, we highlight that radio-emitting star-forming galaxies and AGNs are expected to host supermassive black holes accreting with different Eddington ratio distributions and to occupy different loci in the galaxy main-sequence diagrams. These specific predictions are consistent with current data sets but need to be tested with larger statistics via future radio data with multiband coverage on wide areas, as will become routinely achievable with the advent of the Square Kilometre Array and its precursors.« less

Solar radio continuum storms and a breathing magnetic field model

NASA Technical Reports Server (NTRS)

1975-01-01

Radio noise continuum emissions observed in metric and decametric wave frequencies are, in general, associated with actively varying sunspot groups accompanied by the S-component of microwave radio emissions. These continuum emission sources, often called type I storm sources, are often associated with type III burst storm activity from metric to hectometric wave frequencies. This storm activity is, therefore, closely connected with the development of these continuum emission sources. It is shown that the S-component emission in microwave frequencies generally precedes, by several days, the emission of these noise continuum storms of lower frequencies. In order for these storms to develop, the growth of sunspot groups into complex types is very important in addition to the increase of the average magnetic field intensity and area of these groups. After giving a review on the theory of these noise continuum storm emissions, a model is briefly considered to explain the relation of the emissions to the storms.

URSI and Nachrichtentechnische Gesellschaft, General Session, Kleinheubach, West Germany, Oct. 6-10, 1986, Reports

NASA Astrophysics Data System (ADS)

Factors affecting the atmospheric propagation of EM waves, research on the ionosphere, and advances in radar and communications technology are examined in reviews and reports. Topics discussed include refraction corrections for radio astronomy and geodesy, speckle masking, radar studies of atmospheric motion, EISCAT measurements in the polar electrojet, active experiments in the polar ionosphere, and dispersion relations for drift-Alfven and drift-acoustic waves. Consideration is given to a microcomputer prediction system for HF communications over Europe, frequency determination of a hyperfine line of CH4 at 88 THz, multipath propagation in digital mobile communication, a robust digital voice transmission technique for land mobile radio, CMOS LSI for digital signal processing in mobile radio equipment, the representation of EM fields by dyadic Green functions, scalarization of Maxwell's equations for anisotropic media, and satellite antennas for land vehicles and aircraft.

The Radio & Plasma Wave Investigation (RPWI) for JUICE

NASA Astrophysics Data System (ADS)

Wahlund, J.-E.

2013-09-01

We present the Radio & Plasma Waves Investigation (RPWI) selected for implementation on the JUICE mission. RPWI consists of a highly integrated instrument package that provides a whole set of plasma and fields measurements. The RPWI instrument has outstanding new capabilities not previously available to outer planet missions, and that would address many fundamental planetary science objectives. Specifically, RPWI would be able to study the electro-dynamic influence of the Jovian magnetosphere on the exospheres, surfaces and conducting oceans of Ganymede, Europa and Callisto. RPWI would also be able to monitor the sources of radio emissions from auroral regions of Ganymede and Jupiter, and possibly also from lightning activity in Jupiter's clouds. Moreover, RPWI will search for exhaust plumes from cracks on the icy moons, as well as μm-sized dust and related dust-plasmasurface interaction processes occurring near the icy moons of Jupiter.

A Review of Ionospheric Scintillation Models.

PubMed

Priyadarshi, S

This is a general review of the existing climatological models of ionospheric radio scintillation for high and equatorial latitudes. Trans-ionospheric communication of radio waves from transmitter to user is affected by the ionosphere which is highly variable and dynamic in both time and space. Scintillation is the term given to irregular amplitude and phase fluctuations of the received signals and related to the electron density irregularities in the ionosphere. Key sources of ionospheric irregularities are plasma instabilities; every irregularities model is based on the theory of radio wave propagation in random media. It is important to understand scintillation phenomena and the approach of different theories. Therefore, we have briefly discussed the theories that are used to interpret ionospheric scintillation data. The global morphology of ionospheric scintillation is also discussed briefly. The most important (in our opinion) analytical and physical models of scintillation are reviewed here.

Variability of Kelvin wave momentum flux from high-resolution radiosonde and radio occultation data

NASA Astrophysics Data System (ADS)

Sjoberg, J. P.; Zeng, Z.; Ho, S. P.; Birner, T.; Anthes, R. A.; Johnson, R. H.

2017-12-01

Direct measurement of momentum flux from Kelvin waves in the stratosphere remains challenging. Constraining this flux from observations is an important step towards constraining the flux from models. Here we present results from analyses using linear theory to estimate the Kelvin wave amplitudes and momentum fluxes from both high-resolution radiosondes and from radio occultation (RO) data. These radiosonde data are from a contiguous 11-year span of soundings performed at two Department of Energy Atmospheric Radiation Measurement sites, while the RO data span 14 years from multiple satellite missions. Daily time series of the flux from both sources are found to be in quantitative agreement with previous studies. Climatological analyses of these data reveal the expected seasonal cycle and variability associated with the quasi-biennial oscillation. Though both data sets provide measurements on distinct spatial and temporal scales, the estimated flux from each provides insight into separate but complimentary aspects of how the Kelvin waves affect the stratosphere. Namely, flux derived from radiosonde sites provide details on the regional Kelvin wave variability, while the flux from RO data are zonal mean estimates.

The mm-wave compact component of an AGN

NASA Astrophysics Data System (ADS)

Behar, Ehud; Vogel, Stuart; Baldi, Ranieri D.; Smith, Krista L.; Mushotzky, Richard F.

2018-07-01

mm-wave emission from active galactic nuclei (AGNs) may hold the key to understanding the physical origin of their radio cores. The correlation between radio/mm and X-ray luminosity may suggest a similar physical origin of the two sources. Since synchrotron self-absorption decreases with frequency, mm-waves probe smaller length-scales than cm-waves. We report on 100 GHz (3 mm) observations with the Combined Array for Research in Millimeter-wave Astronomy of 26 AGNs selected from the hard X-ray Swift/Burst Alert Telescope survey. 20/26 targets were detected at 100 GHz down to the 1 mJy (3σ) sensitivity, which corresponds to optically thick synchrotron source sizes of 10-4-10-3 pc. Most sources show a 100 GHz flux excess with respect to the spectral slope extrapolated from low frequencies. This mm spectral component likely originates from smaller scales than the few-GHz emission. The measured mm sources lie roughly around the Lmm (100 GHz) ˜10-4LX (2-10 keV) relation, similar to a few previously published X-ray selected sources, and hinting perhaps at a common coronal origin.

Quasi-periodic Radio Bursts Associated with Fast-mode Waves near a Magnetic Null Point

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Pankaj; Nakariakov, Valery M.; Cho, Kyung-Suk, E-mail: pankaj.kumar@nasa.gov

This paper presents an observation of quasi-periodic rapidly propagating waves observed in the Atmospheric Image Assembly (AIA) 171/193 Å channels during the impulsive phase of an M1.9 flare that occurred on 2012 May 7. The instant period was found to decrease from 240 to 120 s, and the speed of the wavefronts was in the range of ∼664–1416 km s{sup −1}. Almost simultaneously, quasi-periodic bursts with similar instant periods, ∼70 and ∼140 s, occur in the microwave emission and in decimetric type IV and type III radio bursts, and in the soft X-ray emission. The magnetic field configuration of themore » flare site was consistent with a breakout topology, i.e., a quadrupolar field along with a magnetic null point. The quasi-periodic rapidly propagating wavefronts of the EUV emission are interpreted as a fast magnetoacoustic wave train. The observations suggest that the fast-mode waves are generated during the quasi-periodic magnetic reconnection in the cusp region above the flare arcade loops. For the first time, we provide evidence of a tadpole wavelet signature at about 70–140 s in decimetric (245/610 MHz) radio bursts, along with the direct observation of a coronal fast-mode wave train in EUV. In addition, at AIA 131/193 Å we observed quasi-periodic EUV disturbances with periods of 95 and 240 s propagating downward at apparent speeds of 172–273 km s{sup −1}. The nature of these downward propagating disturbances is not revealed, but they could be connected to magnetoacoustic waves or periodically shrinking loops.« less

Self-modulational formation of pulsar microstructures

NASA Technical Reports Server (NTRS)

Kennel, C. F.; Chian, A. C.-L.

1987-01-01

A nonlinear plasma theory for self modulation of pulsar radio pulses is discussed. A nonlinear Schroedinger equation is derived for strong electromagnetic waves propagating in an electron positron plasma. The nonlinearities arising from wave intensity induced particle mass variation may excite the modulational instability of circularly and linearly polarized pulsar radiation. The resulting wave envelopes can take the form of periodic wave trains or solitons. These nonlinear stationary waveforms may account for the formation of pulsar microstructures.

Correlation of Windspeed and Antarctic Surface Roughness

NASA Astrophysics Data System (ADS)

Stockham, Mark; Anita Collaboration

2015-04-01

When electromagnetic waves interact with a media interface the transmitted and reflected portions of the incoming wave depend on the incident angle of the wave and wavelength (as well as the material properties of the media). The roughness of the surface of Antarctica affects the radio frequency signals received by airborne experiments, such as the balloon-borne experiment ANITA (ANtarctic Impulsive Transient Antenna) which observes the reflected radio waves from cosmic ray-induced extensive air showers (EAS). Roughness of a given scale can cause decoherence of the reflected signal and is an important effect to understand when estimating the amplitude of the incoming wave based on the reflected wave. It is challenging to get a survey of surface roughness over many of the areas that these experiments are likely to pass over. Correlating historical wind speed records with statistical roughness as observed by the backscatter of satellite [Rémy F, Parouty S. Remote Sensing. 2009] and airborne experiments operating at different frequencies can possibly be used to predict time-dependent surface roughness with surface wind speed as the input. These correlations will be presented for a variety of areas on the Antarctic ice shelf. NASA Grant NNX11AC47G.

Full-duplex radio-over-fiber system with tunable millimeter-wave signal generation and wavelength reuse for upstream signal.

PubMed

Wang, Yiqun; Pei, Li; Li, Jing; Li, Yueqin

2017-06-10

A full-duplex radio-over-fiber system is proposed, which provides both the generation of a millimeter-wave (mm-wave) signal with tunable frequency multiplication factors (FMFs) and wavelength reuse for uplink data. A dual-driving Mach-Zehnder modulator and a phase modulator are cascaded to form an optical frequency comb. An acousto-optic tunable filter based on a uniform fiber Bragg grating (FBG-AOTF) is employed to select three target optical sidebands. Two symmetrical sidebands are chosen to generate mm waves with tunable FMFs up to 16, which can be adjusted by changing the frequency of the applied acoustic wave. The optical carrier is reused at the base station for uplink connection. FBG-AOTFs driven by two acoustic wave signals are experimentally fabricated and further applied in the proposed scheme. Results of the research indicate that the 2-Gbit/s data can be successfully transmitted over a 25-km single-mode fiber for bidirectional full-duplex channels with power penalty of less than 2.6 dB. The feasibility of the proposed scheme is verified by detailed simulations and partial experiments.

The Sun Radio Imaging Space Experiment (SunRISE) Mission

NASA Astrophysics Data System (ADS)

Lazio, Joseph; Kasper, Justin; Maksimovic, Milan; Alibay, Farah; Amiri, Nikta; Bastian, Tim; Cohen, Christina; Landi, Enrico; Manchester, Ward; Reinard, Alysha; Schwadron, Nathan; Cecconi, Baptiste; Hallinan, Gregg; Hegedus, Alex; Krupar, Vratislav; Zaslavsky, Arnaud

2017-04-01

Radio emission from coronal mass ejections (CMEs) is a direct tracer of particle acceleration in the inner heliosphere and potential magnetic connections from the lower solar corona to the larger heliosphere. Energized electrons excite Langmuir waves, which then convert into intense radio emission at the local plasma frequency, with the most intense acceleration thought to occur within 20 RS. The radio emission from CMEs is quite strong such that only a relatively small number of antennas is required to detect and map it, but many aspects of this particle acceleration and transport remain poorly constrained. Ground-based arrays would be quite capable of tracking the radio emission associated with CMEs, but absorption by the Earth's ionosphere limits the frequency coverage of ground-based arrays (ν ≳ 15 MHz), which in turn limits the range of solar distances over which they can track the radio emission (≲ 3RS). The state-of-the-art for tracking such emission from space is defined by single antennas (Wind/WAVES, Stereo/SWAVES), in which the tracking is accomplished by assuming a frequency-to-density mapping; there has been some success in triangulating the emission between the spacecraft, but considerable uncertainties remain. We describe the Sun Radio Imaging Space Experiment (SunRISE) mission concept: A constellation of small spacecraft in a geostationary graveyard orbit designed to localize and track radio emissions in the inner heliosphere. Each spacecraft would carry a receiving system for observations below 25 MHz, and SunRISE would produce the first images of CMEs more than a few solar radii from the Sun. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

The Sun Radio Imaging Space Experiment (SunRISE) Mission

NASA Astrophysics Data System (ADS)

Kasper, J. C.; Lazio, J.; Alibay, F.; Amiri, N.; Bastian, T.; Cohen, C.; Landi, E.; Hegedus, A. M.; Maksimovic, M.; Manchester, W.; Reinard, A.; Schwadron, N.; Cecconi, B.; Hallinan, G.; Krupar, V.

2017-12-01

Radio emission from coronal mass ejections (CMEs) is a direct tracer of particle acceleration in the inner heliosphere and potential magnetic connections from the lower solar corona to the larger heliosphere. Energized electrons excite Langmuir waves, which then convert into intense radio emission at the local plasma frequency, with the most intense acceleration thought to occur within 20 R_S. The radio emission from CMEs is quite strong such that only a relatively small number of antennas is required to detect and map it, but many aspects of this particle acceleration and transport remain poorly constrained. Ground-based arrays would be quite capable of tracking the radio emission associated with CMEs, but absorption by the Earth's ionosphere limits the frequency coverage of ground-based arrays (nu > 15 MHz), which in turn limits the range of solar distances over which they can track the radio emission (< 3 R_S). The state-of-the-art for tracking such emission from space is defined by single antennas (Wind/WAVES, Stereo/SWAVES), in which the tracking is accomplished by assuming a frequency-to-density mapping; there has been some success in triangulating the emission between the spacecraft, but considerable uncertainties remain. We describe the Sun Radio Imaging Space Experiment (SunRISE) mission concept: A constellation of small spacecraft in a geostationary graveyard orbit designed to localize and track radio emissions in the inner heliosphere. Each spacecraft would carry a receiving system for observations below 25 MHz, and SunRISE would produce the first images of CMEs more than a few solar radii from the Sun. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

Automated detection of extended sources in radio maps: progress from the SCORPIO survey

NASA Astrophysics Data System (ADS)

Riggi, S.; Ingallinera, A.; Leto, P.; Cavallaro, F.; Bufano, F.; Schillirò, F.; Trigilio, C.; Umana, G.; Buemi, C. S.; Norris, R. P.

2016-08-01

Automated source extraction and parametrization represents a crucial challenge for the next-generation radio interferometer surveys, such as those performed with the Square Kilometre Array (SKA) and its precursors. In this paper, we present a new algorithm, called CAESAR (Compact And Extended Source Automated Recognition), to detect and parametrize extended sources in radio interferometric maps. It is based on a pre-filtering stage, allowing image denoising, compact source suppression and enhancement of diffuse emission, followed by an adaptive superpixel clustering stage for final source segmentation. A parametrization stage provides source flux information and a wide range of morphology estimators for post-processing analysis. We developed CAESAR in a modular software library, also including different methods for local background estimation and image filtering, along with alternative algorithms for both compact and diffuse source extraction. The method was applied to real radio continuum data collected at the Australian Telescope Compact Array (ATCA) within the SCORPIO project, a pathfinder of the Evolutionary Map of the Universe (EMU) survey at the Australian Square Kilometre Array Pathfinder (ASKAP). The source reconstruction capabilities were studied over different test fields in the presence of compact sources, imaging artefacts and diffuse emission from the Galactic plane and compared with existing algorithms. When compared to a human-driven analysis, the designed algorithm was found capable of detecting known target sources and regions of diffuse emission, outperforming alternative approaches over the considered fields.

Quantification of Rock Damage from Small Explosions and Its Effect on Shear-Wave Generation

DTIC Science & Technology

2009-06-15

close to a nearby cell /radio tower and the active quarry wall to detonate our planned 400 lb explosions. Core drilling at an alternative test site...Figure ) was conducted further away from the active quarry wall and a nearby cell /radio tower. The alternative site would be far enough away from...returned into the original location (Figure ). In order to reduce the projected ground vibrations at the cell /radio tower and high wall of the active

Advanced Transceivers for Firefighters

NASA Technical Reports Server (NTRS)

Blood, B. D.; Gandhi, O. P.; Radke, R. E.

1986-01-01

Report presents concept of improved portable radio transceiver for firefighters. Based in part on study of propagation of radio waves in such environments as high-rise buildings, ships, and tunnels. Study takes into account possible health hazard posed by personal tranceivers and needs and wishes expressed by firefighters in interviews. Conceptual radio attaches to clothing to allow hands-free use; voice-actuated with microphone worn at throat. Speaker placed near wearer's shoulder. Flexible antenna placed either horizontally across shoulders, vertically at one shoulder, or on transceiver itself.

Detection by Sardinia Radio Telescope of radio pulses at 7 GHz from the Magnetar PSR J1745-2900 in the Galactic center region

NASA Astrophysics Data System (ADS)

Buttu, Marco; D'Amico, Nichi; Egron, Elise; Iacolina, Maria Noemi; Marongiu, Pasqualino; Migoni, Carlo; Pellizzoni, Alberto; Poppi, Sergio; Possenti, Andrea; Trois, Alessio; Vargiu, Gian Paolo

2013-05-01

During the Sardinia Radio Telescope (SRT) science verification phase, we observed PSR J1745-2900, firstly detected as an X-ray flare from Sgr A* by Swift and then identified as a 3.76 s X-ray magnetar with NuSTAR telescope (ATels #5006, #5020, #5027, #5032, #5033, #5035), at a central frequency of 7.30 GHz. We used a Beam Wave Guide focus cryogenically cooled receiver (system temperature ~25 K).

Cosmic non-TEM radiation and synthetic feed array sensor system in ASIC mixed signal technology

NASA Astrophysics Data System (ADS)

Centureli, F.; Scotti, G.; Tommasino, P.; Trifiletti, A.; Romano, F.; Cimmino, R.; Saitto, A.

2014-08-01

The paper deals with the opportunity to introduce "Not strictly TEM waves" Synthetic detection Method (NTSM), consisting in a Three Axis Digital Beam Processing (3ADBP), to enhance the performances of radio telescope and sensor systems. Current Radio Telescopes generally use the classic 3D "TEM waves" approximation Detection Method, which consists in a linear tomography process (Single or Dual axis beam forming processing) neglecting the small z component. The Synthetic FEED ARRAY three axis Sensor SYSTEM is an innovative technique using a synthetic detection of the generic "NOT strictly TEM Waves radiation coming from the Cosmo, which processes longitudinal component of Angular Momentum too. Than the simultaneous extraction from radiation of both the linear and quadratic information component, may reduce the complexity to reconstruct the Early Universe in the different requested scales. This next order approximation detection of the observed cosmologic processes, may improve the efficacy of the statistical numerical model used to elaborate the same information acquired. The present work focuses on detection of such waves at carrier frequencies in the bands ranging from LF to MMW. The work shows in further detail the new generation of on line programmable and reconfigurable Mixed Signal ASIC technology that made possible the innovative Synthetic Sensor. Furthermore the paper shows the ability of such technique to increase the Radio Telescope Array Antenna performances.

Suzaku View of the Swift/BAT Active Galactic Nuclei. V. Torus Structure of Two Luminous Radio-Loud Active Galactic Nuclei (3C 206 and PKS 0707-35)

NASA Technical Reports Server (NTRS)

Tazaki, Fumie; Ueda, Yoshihiro; Terashima, Yuichi; Mushotzky, Richard F.; Tombesi, Francesco

2013-01-01

We present the results from broadband X-ray spectral analysis of 3C 206 and PKS 0707-35 with Suzaku and Swift/BAT, two of the most luminous unobscured and obscured radio-loud active galactic nuclei (AGNs) with hard X-ray luminosities of 10(sup 45.5) erg per second and 10(sup 44.9) erg per second (14-195 keV), respectively. Based on the radio core luminosity, we estimate that the X-ray spectrum of 3C 206 contains a significant (60% in the 14-195 keV band) contribution from the jet, while it is negligible in PKS 0707-35.We can successfully model the spectra with the jet component (for 3C 206), the transmitted emission, and two reflection components from the torus and the accretion disk. The reflection strengths from the torus are found to be R(sub torus)(=Omega/2pi) = 0.29 +/- 0.18 and 0.41 +/- 0.18 for 3C 206 and PKS 0707-35, respectively, which are smaller than those in typical Seyfert galaxies. Utilizing the torus model by Ikeda et al., we quantify the relation between the half-opening angle of a torus (theta(sub oa)) and the equivalent width of an iron-K line. The observed equivalent width of 3C 206, less than 71 eV, constrains the column density in the equatorial plane to N(sup eq)(sub H) lesst han 10(sup 23) per square centimeter, or the half-opening angle to theta(sub oa) greater than 80 deg. if N(sup eq)(sub H) = 10(sup 24) per square centimeter is assumed. That of PKS 0707-35, 72 +/- 36 eV, is consistent with N(sup eq)(sub H) 10(sup 23) per square centimeter. Our results suggest that the tori in luminous radio-loud AGNs are only poorly developed. The trend is similar to that seen in radio-quiet AGNs, implying that the torus structure is not different between AGNs with jets and without jets.

Investigation of fatigue behavior of Pb(Zr0.45Ti0.55)O3 thin films under asymmetric polarization switching

NASA Astrophysics Data System (ADS)

Zhu, Hui; Chen, Yueyuan; Chu, Daping; Feng, Shiwei; Zhang, Yingqiao; Wang, Pengfei

2016-09-01

The fatigue of lead zirconate titanate (PZT) thin films was measured under repetitive switching using asymmetric square waves. The remnant polarization and coercive voltage were found to present regular changes in the initial 10 s, independent of the asymmetry or frequency of switching waves. We attributed the change to the relaxation of stress in the film and identified a coercive voltage V 0 of 0.6 V for the stress-free film. By comparing the coercive voltage and V 0, we found that a built-in electric field was induced by asymmetric switching, where the direction and magnitude were dependent on the degree of waveform asymmetry. Furthermore, the fatigue speed was suggested to be closely related to the generation rate of oxygen vacancies. It was confirmed by our result that a faster decay of remnant polarization can be obtained by applying square waves with a higher degree of asymmetry or symmetry of square waves with a lower frequency.

Radio Wave Propagation for Communication on and around Mars. Part 1; Highlights: Propagation Through Mars Environment

NASA Technical Reports Server (NTRS)

Ho, Christian; Golshan, Nasser

1999-01-01

We recommend to use the dayside Martian ionosphere as a reflector for global communication, because the dayside ionosphere has stable density peak and usable critic frequency. This is very crucial for the future Mars ground to around communication. The dayside ionosphere has been well modeled as a Chapman layer. We suggest to perform the Martian nightside ionospheric modeling study. Because the nightside ionosphere has very little measurements available, we propose to drop a digital ionosond instrument into the Mars surface for data collection. Even though the Martian tropospheric radio refractivity has small value, it still can cause the ray bending and multipath effects. We recommend to perform an accurate calculation on excess phase and group delays (range and time delays). Other effects, such as range rate errors, appearance angle deviation, defocusing loss on Mars, etc. are also needed to be estimated. Ice depolarization effects due to Martian clouds on radio waves is unknown yet, which is expected to be small, because lower optical depth and thinner layer of cloud: Total Martian atmospheric gaseous attenuation is expected to be less than 1 dB on microwaves band, because the Martian atmosphere has very low concentration in uncondensed H2O and O2. An accurate calculation for zenith opacity requires the information about scale heights of H2O and O2 distribution. An accurate water vapor altitude profile at Mars is not available yet. Under the normal condition, CO2 and N2 gases do not have electric or magnetic dipoles and do not absorb electromagnetic energy from the waves. However, they may generate the dipoles through a collision and interact with waves under a high density condition and absorb electromagnetic waves in the infrared and visible band. Dust storm is most dominant factor to the radio wave attenuation. Large Martian dust storm can cause at least 3 dB or higher loss to Ka band wave. For a normal dust storm, the attenuation is about 1 dB. The attenuation much depends on dust mass loading, dust size distribution, etc. Most large dust storm occur in the southern hemisphere during later spring and early summer when the southern hemisphere become suddenly hot.

Depolarization of Pulsar Radio Emission.

PubMed

Lyutikov

1999-11-01

We show that intensity-dependent depolarization of single pulses may be due to the nonlinear decay of the "upper" ordinary (O) mode into an unpolarized extraordinary mode and a backward-propagating wave. The decay occurs in the innermost parts of the pulsar magnetosphere for obliquely propagating O waves.

Spatial transformation-enabled electromagnetic devices: from radio frequencies to optical wavelengths

PubMed Central

Jiang, Zhi Hao; Turpin, Jeremy P.; Morgan, Kennith; Lu, Bingqian; Werner, Douglas H.

2015-01-01

Transformation optics provides scientists and engineers with a new powerful design paradigm to manipulate the flow of electromagnetic waves in a user-defined manner and with unprecedented flexibility, by controlling the spatial distribution of the electromagnetic properties of a medium. Using this approach, over the past decade, various previously undiscovered physical wave phenomena have been revealed and novel electromagnetic devices have been demonstrated throughout the electromagnetic spectrum. In this paper, we present versatile theoretical and experimental investigations on designing transformation optics-enabled devices for shaping electromagnetic wave radiation and guidance, at both radio frequencies and optical wavelengths. Different from conventional coordinate transformations, more advanced and versatile coordinate transformations are exploited here to benefit diverse applications, thereby providing expanded design flexibility, enhanced device performance, as well as reduced implementation complexity. These design examples demonstrate the comprehensive capability of transformation optics in controlling electromagnetic waves, while the associated novel devices will open up new paths towards future integrated electromagnetic component synthesis and design, from microwave to optical spectral regimes. PMID:26217054

Non-contact radio frequency shielding and wave guiding by multi-folded transformation optics method

PubMed Central

Madni, Hamza Ahmad; Zheng, Bin; Yang, Yihao; Wang, Huaping; Zhang, Xianmin; Yin, Wenyan; Li, Erping; Chen, Hongsheng

2016-01-01

Compared with conventional radio frequency (RF) shielding methods in which the conductive coating material encloses the circuits design and the leakage problem occurs due to the gap in such conductive material, non-contact RF shielding at a distance is very promising but still impossible to achieve so far. In this paper, a multi-folded transformation optics method is proposed to design a non-contact device for RF shielding. This “open-shielded” device can shield any object at a distance from the electromagnetic waves at the operating frequency, while the object is still physically open to the outer space. Based on this, an open-carpet cloak is proposed and the functionality of the open-carpet cloak is demonstrated. Furthermore, we investigate a scheme of non-contact wave guiding to remotely control the propagation of surface waves over any obstacles. The flexibilities of such multi-folded transformation optics method demonstrate the powerfulness of the method in the design of novel remote devices with impressive new functionalities. PMID:27841358

Full-duplex radio over fiber link with colorless source-free base station based on single sideband optical mm-wave signal with polarization rotated optical carrier

NASA Astrophysics Data System (ADS)

Ma, Jianxin

2016-07-01

A full-duplex radio-over fiber (RoF) link scheme based on single sideband (SSB) optical millimeter (mm)-wave signal with polarization-rotated optical carrier is proposed to realize the source-free colorless base station (BS), in which a polarization beam splitter (PBS) is used to abstract part of the optical carrier for conveying the uplink data. Since the optical carrier for the uplink does not bear the downlink signal, no cross-talk from the downlink contaminates the uplink signal. The simulation results demonstrate that both down- and up-links maintain good performance. The mm-wave signal distribution network based on the proposed full duplex fiber link scheme can use the uniform source-free colorless BSs, which makes the access system very simpler.

Equatorial waves in the stratosphere of Uranus

NASA Technical Reports Server (NTRS)

Hinson, David P.; Magalhaes, Julio A.

1991-01-01

Analyses of radio occultation data from Voyager 2 have led to the discovery and characterization of an equatorial wave in the Uranus stratosphere. The observed quasi-periodic vertical atmospheric density variations are in close agreement with theoretical predictions for a wave that propagates vertically through the observed background structure of the stratosphere. Quantitative comparisons between measurements obtained at immersion and at emersion yielded constraints on the meridional and zonal structure of the wave; the fact that the two sets of measurements are correlated suggests a wave of planetary scale. Two equatorial wave models are proposed for the wave.

Nanosecond-level time synchronization of autonomous radio detector stations for extensive air showers

NASA Astrophysics Data System (ADS)

The Pierre Auger Collaboration

2016-01-01

To exploit the full potential of radio measurements of cosmic-ray air showers at MHz frequencies, a detector timing synchronization within 1 ns is needed. Large distributed radio detector arrays such as the Auger Engineering Radio Array (AERA) rely on timing via the Global Positioning System (GPS) for the synchronization of individual detector station clocks. Unfortunately, GPS timing is expected to have an accuracy no better than about 5 ns. In practice, in particular in AERA, the GPS clocks exhibit drifts on the order of tens of ns. We developed a technique to correct for the GPS drifts, and an independent method is used to cross-check that indeed we reach a nanosecond-scale timing accuracy by this correction. First, we operate a ``beacon transmitter'' which emits defined sine waves detected by AERA antennas recorded within the physics data. The relative phasing of these sine waves can be used to correct for GPS clock drifts. In addition to this, we observe radio pulses emitted by commercial airplanes, the position of which we determine in real time from Automatic Dependent Surveillance Broadcasts intercepted with a software-defined radio. From the known source location and the measured arrival times of the pulses we determine relative timing offsets between radio detector stations. We demonstrate with a combined analysis that the two methods give a consistent timing calibration with an accuracy of 2 ns or better. Consequently, the beacon method alone can be used in the future to continuously determine and correct for GPS clock drifts in each individual event measured by AERA.

Nanosecond-level time synchronization of autonomous radio detector stations for extensive air showers

DOE PAGES

Aab, Alexander

2016-01-29

To exploit the full potential of radio measurements of cosmic-ray air showers at MHz frequencies, a detector timing synchronization within 1 ns is needed. Large distributed radio detector arrays such as the Auger Engineering Radio Array (AERA) rely on timing via the Global Positioning System (GPS) for the synchronization of individual detector station clocks. Unfortunately, GPS timing is expected to have an accuracy no better than about 5 ns. In practice, in particular in AERA, the GPS clocks exhibit drifts on the order of tens of ns. We developed a technique to correct for the GPS drifts, and an independentmore » method used for cross-checks that indeed we reach nanosecond-scale timing accuracy by this correction. First, we operate a “beacon transmitter” which emits defined sine waves detected by AERA antennas recorded within the physics data. The relative phasing of these sine waves can be used to correct for GPS clock drifts. In addition to this, we observe radio pulses emitted by commercial airplanes, the position of which we determine in real time from Automatic Dependent Surveillance Broadcasts intercepted with a software-defined radio. From the known source location and the measured arrival times of the pulses we determine relative timing offsets between radio detector stations. We demonstrate with a combined analysis that the two methods give a consistent timing calibration with an accuracy of 2 ns or better. Consequently, the beacon method alone can be used in the future to continuously determine and correct for GPS clock drifts in each individual event measured by AERA.« less

Doppler radar flowmeter

DOEpatents

Petlevich, Walter J.; Sverdrup, Edward F.

1978-01-01

A Doppler radar flowmeter comprises a transceiver which produces an audio frequency output related to the Doppler shift in frequency between radio waves backscattered from particulate matter carried in a fluid and the radiated radio waves. A variable gain amplifier and low pass filter are provided for amplifying and filtering the transceiver output. A frequency counter having a variable triggering level is also provided to determine the magnitude of the Doppler shift. A calibration method is disclosed wherein the amplifier gain and frequency counter trigger level are adjusted to achieve plateaus in the output of the frequency counter and thereby allow calibration without the necessity of being able to visually observe the flow.

On Features of the Generation of Artificial Ionospheric Irregularities with Transverse Scales of 50-200 m

NASA Astrophysics Data System (ADS)

Bolotin, I. A.; Frolov, V. L.; Akchurin, A. D.; Zykov, E. Yu.

2017-05-01

We consider the features of generation of artificial ionospheric irregularities with transverse (to the geomagnetic field) scales l⊥ ≈ 50-200 m in the ionosphere modified by high-power HF radio waves. It was found that there are at least two mechanisms for generation of these irregularities in the ionospheric F region. The first mechanism is related to the resonant interaction between radio waves and the ionospheric plasma, while the second one takes place even in the absence of the resonant interaction. Different polarization of the high-power radiation was used to separate the mechanisms in the measurements.

Investigation of the spatial structure and developmental dynamics of near-Earth plasma perturbations under the action of powerful HF radio waves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Belov, A. S., E-mail: alexis-belov@yandex.ru

2015-10-15

Results of numerical simulations of the near-Earth plasma perturbations induced by powerful HF radio waves from the SURA heating facility are presented. The simulations were performed using a modified version of the SAMI2 ionospheric model for the input parameters corresponding to the series of in-situ SURA–DEMETER experiments. The spatial structure and developmental dynamics of large-scale plasma temperature and density perturbations have been investigated. The characteristic formation and relaxation times of the induced large-scale plasma perturbations at the altitudes of the Earth’s outer ionosphere have been determined.

Interaction of electromagnetic and acoustic waves in a stochastic atmosphere

NASA Technical Reports Server (NTRS)

Bhatnagar, N.; Frankel, M. S.; Peterson, A. M.

1977-01-01

This paper considers the interaction of electromagnetic and acoustic waves where a Radio Acoustic Sounding System (RASS) is operated in a stochastic environment characterized by turbulence, winds and mean-temperature gradients. It has been shown that for a RASS operating at acoustic frequencies below a few kilohertz propagating under typical atmospheric conditions, turbulence has little effect on the strength of the received radio signal scattered from the pulse at heights up to a few kilometers. This result implies that the received RF signal level (power) is primarily a function of sound intensity which decreases as x exp minus 2 where x is the altitude.

Reproducing continuous radio blackout using glow discharge plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Kai; Li, Xiaoping; Liu, Donglin

2013-10-15

A novel plasma generator is described that offers large-scale, continuous, non-magnetized plasma with a 30-cm-diameter hollow structure, which provides a path for an electromagnetic wave. The plasma is excited by a low-pressure glow discharge, with varying electron densities ranging from 10{sup 9} to 2.5 × 10{sup 11} cm{sup −3}. An electromagnetic wave propagation experiment reproduced a continuous radio blackout in UHF-, L-, and S-bands. The results are consistent with theoretical expectations. The proposed method is suitable in simulating a plasma sheath, and in researching communications, navigation, electromagnetic mitigations, and antenna compensation in plasma sheaths.

Programme of Indian Centre for Space Physics using Very Low Frequency Radio Waves

NASA Astrophysics Data System (ADS)

Chakrabarti, Sandip Kumar; Sasmal, Sudipta; Pal, Sujay; Kanta Maji, Surya; Ray, Suman

Indian Centre for Space Physics conducted two major VLF campaigns all over Indian Sub-continent to study the propagation effects of VLF radio waves. It made multi-receiver observations during solar eclipse. ICSP not only recorded multitudes of solar flares, it also reproduced VLF observation from ab initio calculation. ICSP extended its study to the field of earthquake predictions using signal anomalies and using case by case studies as well as statistical analysis, showed that anomalies are real and more studies are required to understand them. Using earth as a gigantic detector, it detected ionospheric perturbations due to soft gamma-ray repeaters and gamma-ray bursts.

Effective Algorithm for Detection and Correction of the Wave Reconstruction Errors Caused by the Tilt of Reference Wave in Phase-shifting Interferometry

NASA Astrophysics Data System (ADS)

Xu, Xianfeng; Cai, Luzhong; Li, Dailin; Mao, Jieying

2010-04-01

In phase-shifting interferometry (PSI) the reference wave is usually supposed to be an on-axis plane wave. But in practice a slight tilt of reference wave often occurs, and this tilt will introduce unexpected errors of the reconstructed object wave-front. Usually the least-square method with iterations, which is time consuming, is employed to analyze the phase errors caused by the tilt of reference wave. Here a simple effective algorithm is suggested to detect and then correct this kind of errors. In this method, only some simple mathematic operation is used, avoiding using least-square equations as needed in most methods reported before. It can be used for generalized phase-shifting interferometry with two or more frames for both smooth and diffusing objects, and the excellent performance has been verified by computer simulations. The numerical simulations show that the wave reconstruction errors can be reduced by 2 orders of magnitude.

Ionization tube simmer current circuit

DOEpatents

Steinkraus, R.F. Jr.

1994-12-13

A highly efficient flash lamp simmer current circuit utilizes a fifty percent duty cycle square wave pulse generator to pass a current over a current limiting inductor to a full wave rectifier. The DC output of the rectifier is then passed over a voltage smoothing capacitor through a reverse current blocking diode to a flash lamp tube to sustain ionization in the tube between discharges via a small simmer current. An alternate embodiment of the circuit combines the pulse generator and inductor in the form of an FET off line square wave generator with an impedance limited step up output transformer which is then applied to the full wave rectifier as before to yield a similar simmer current. 6 figures.

Ionization tube simmer current circuit

DOEpatents

Steinkraus, Jr., Robert F.

1994-01-01

A highly efficient flash lamp simmer current circuit utilizes a fifty percent duty cycle square wave pulse generator to pass a current over a current limiting inductor to a full wave rectifier. The DC output of the rectifier is then passed over a voltage smoothing capacitor through a reverse current blocking diode to a flash lamp tube to sustain ionization in the tube between discharges via a small simmer current. An alternate embodiment of the circuit combines the pulse generator and inductor in the form of an FET off line square wave generator with an impedance limited step up output transformer which is then applied to the full wave rectifier as before to yield a similar simmer current.

Spin-wave energy dispersion of a frustrated spin-½ Heisenberg antiferromagnet on a stacked square lattice.

PubMed

Majumdar, Kingshuk

2011-03-23

The effects of interlayer coupling and spatial anisotropy on the spin-wave excitation spectra of a three-dimensional spatially anisotropic, frustrated spin-½ Heisenberg antiferromagnet (HAFM) are investigated for the two ordered phases using second-order spin-wave expansion. We show that the second-order corrections to the spin-wave energies are significant and find that the energy spectra of the three-dimensional HAFM have similar qualitative features to the energy spectra of the two-dimensional HAFM on a square lattice. We also discuss the features that can provide experimental measures for the strength of the interlayer coupling, spatial anisotropy parameter, and magnetic frustration.

Deep Space Network Radiometric Remote Sensing Program

NASA Technical Reports Server (NTRS)

Walter, Steven J.

1994-01-01

Planetary spacecraft are viewed through a troposphere that absorbs and delays radio signals propagating through it. Tropospheric water, in the form of vapor, cloud liquid, and precipitation, emits radio noise which limits satellite telemetry communication link performance. Even at X-band, rain storms have severely affected several satellite experiments including a planetary encounter. The problem will worsen with DSN implementation of Ka-band because communication link budgets will be dominated by tropospheric conditions. Troposphere-induced propagation delays currently limit VLBI accuracy and are significant sources of error for Doppler tracking. Additionally, the success of radio science programs such as satellite gravity wave experiments and atmospheric occultation experiments depends on minimizing the effect of water vapor-induced propagation delays. In order to overcome limitations imposed by the troposphere, the Deep Space Network has supported a program of radiometric remote sensing. Currently, water vapor radiometers (WVRs) and microwave temperature profilers (MTPs) support many aspects of the Deep Space Network operations and research and development programs. Their capability to sense atmospheric water, microwave sky brightness, and atmospheric temperature is critical to development of Ka-band telemetry systems, communication link models, VLBI, satellite gravity wave experiments, and radio science missions. During 1993, WVRs provided data for propagation model development, supported planetary missions, and demonstrated advanced tracking capability. Collection of atmospheric statistics is necessary to model and predict performance of Ka-band telemetry links, antenna arrays, and radio science experiments. Since the spectrum of weather variations has power at very long time scales, atmospheric measurements have been requested for periods ranging from one year to a decade at each DSN site. The resulting database would provide reliable statistics on daily, monthly, and seasonal variations. Only long-term monitoring will prevent biases from being introduced by an exceptionally wet or dry year. Support for planetary missions included tropospheric calibration for the recent Mars Observer gravity wave experiments and Ka-band link experiment (KaBLE). Additionally, several proposed radio science experiments such as profiling planetary atmospheres using satellite occultations and Ka-band gravitational wave searches require advanced radiometer technology development. Finally, there has been a consistent advanced technology program to advance satellite navigational and tracking capabilities. This year that included an experiment with radiometer based tropospheric calibration for a series of VLBI catalog measurements.

Correlating Type II and III Radio Bursts with Solar Energetic Particle Events

NASA Astrophysics Data System (ADS)

Ledbetter, K.; Winter, L. M.; Quinn, R. A.

2013-12-01

Solar energetic particles (SEPs) are high-energy particles, such as protons, which are accelerated at the Sun and speed outward into the solar system. If they reach Earth, they can be harmful to satellites, ionospheric communications, and humans in space or on polar airline routes. NOAA defines an SEP event as an occasion when the flux of protons with energies higher than 10 MeV exceeds 10 pfu (particle flux units) as measured by the GOES satellites in geosynchronous orbit. The most intense SEP events are associated with shocks, driven by coronal mass ejections (CMEs), which accelerate particles as they move through the corona. However, very few CMEs result in SEP events. To determine what factors are most important in distinguishing the shock waves that will result in SEP acceleration toward Earth, we take into account several variables and perform a principal component analysis (PCA) to examine their correlations. First, we examine Type II radio bursts, which are caused by electrons accelerating in the same CME-driven shocks that can accelerate SEPs. Using data from the WAVES instrument on the WIND satellite, these Type II radio bursts, as well as the Type III bursts that often accompany them, can be characterized by slope in 1/f space and by intensity. In addition, local Langmuir waves detected by WIND, which are caused by electrons speeding through the plasma surrounding the satellite, can be an indicator of the magnetic connectivity between the active region and Earth. Finally, X-ray flares directly preceding the Type II burst are also taken into consideration in the PCA analysis. The accompanying figure illustrates an example of the WAVES solar radio bursts along with the GOES solar proton flux >= 10 MeV during the SEP event on April 11, 2013. Using PCA to determine which of these factors are most relevant to the onset, intensity, and duration of SEP events will be valuable in future work to predict such events. In total, we present the analysis of all type II radio bursts observed by WIND between January 2010 and May 2013. Future work will include the STEREO/SWAVES data with a focus on creating an operating real-time SEP forecaster relying on radio, X-ray, and proton flux observations.

Angry Birds in Space

NASA Astrophysics Data System (ADS)

Halford, A. J.

2017-12-01

When space computers first started listening into space radio, they noticed that there were radio noises that happened on the morning side of the Earth. Because these waves sounded like noises birds make in the morning, we named these waves after them. These bird sounding waves can move around the Earth, flying up and down, and sometimes move into an area where there is more stuff. This area is also much colder than where these bird noises are first made. When the waves move into this cold area where there is more stuff, they start to sound like angry birds instead of happy birds. Both of these waves, the happy and angry bird sounding waves, are very important to our understanding of how the tiny things in space move and change. Sometimes the waves which sound like birds can push these tiniest of things into the sky. The happy bird sounding waves can push the tiniest things quickly while the angry bird sounding waves push the tinest of things more slowly. When the tiny things fall into the sky, they create beautiful space lights and light that burns which can hurt people in up goers and not so up goers as well as our things like phones, and space computers. We study these waves that sound like birds to better understand when and where the tiny things will fall. That way we can be prepared and enjoy watching the pretty space lights at night with no worries.

Voyager 1 planetary radio astronomy observations near jupiter.

PubMed

Warwick, J W; Pearce, J B; Riddle, A C; Alexander, J K; Desch, M D; Kaiser, M L; Thieman, J R; Carr, T D; Gulkis, S; Boischot, A; Harvey, C C; Pedersen, B M

1979-06-01

We report results from the first low-frequency radio receiver to be transported into the Jupiter magnetosphere. We obtained dramatic new information, both because Voyager was near or in Jupiter's radio emission sources and also because it was outside the relatively dense solar wind plasma of the inner solar system. Extensive radio spectral arcs, from above 30 to about 1 megahertz, occurred in patterns correlated with planetary longitude. A newly discovered kilometric wavelength radio source may relate to the plasma torus near Io's orbit. In situ wave resonances near closest approach define an electron density profile along the Voyager trajectory and form the basis for a map of the torus. Detailed studies are in progress and are out-lined briefly.

Crowd-Sourced Radio Science at Marshall Space Flight Center

NASA Technical Reports Server (NTRS)

Fry, C. D.; McTernan, J. K.; Suggs, R. M.; Rawlins, L.; Krause, L. H.; Gallagher, D. L.; Adams, M. L.

2018-01-01

August 21, 2017 provided a unique opportunity to investigate the effects of the total solar eclipse on high frequency (HF) radio propagation and ionospheric variability. In Marshall Space Flight Center's partnership with the US Space and Rocket Center (USSRC) and Austin Peay State University (APSU), we engaged citizen scientists and students in an investigation of the effects of an eclipse on the mid-latitude ionosphere. Activities included fieldwork and station-based data collection of HF Amateur Radio frequency bands and VLF radio waves before, during, and after the eclipse to build a continuous record of changing propagation conditions as the moon's shadow marched across the United States. Post-eclipse radio propagation analysis provided insights into ionospheric variability due to the eclipse.

Radio evidence for shock acceleration of electrons in the solar corona

NASA Technical Reports Server (NTRS)

Cane, H. V.; Stone, R. G.; Fainberg, J.; Steinberg, J. L.; Hoang, S.; Stewart, R. T.

1981-01-01

It is pointed out that the new class of kilometer-wavelength solar radio bursts observed with the ISEE-3 Radio Astronomy Experiment occurs at the reported times of type II events, which are indicative of a shock wave. An examination of records from the Culgoora Radio Observatory reveals that the associated type II bursts have fast drift elements emanating from them; that is, a herringbone structure is formed. It is proposed that this new class of bursts is a long-wavelength continuation of the herringbone structure, and it is thought probable that the electrons producing the radio emission are accelerated by shocks. These new events are referred to as shock-accelerated events, and their characteristics are discussed.

Fast Radio Bursts

NASA Astrophysics Data System (ADS)

Kaspi, Victoria M.

2017-01-01

Fast Radio Bursts (FRBs) are a recently discovered phenomenon consisting of short (few ms) bursts of radio waves that have dispersion measures that strongly suggest an extragalactic and possibly cosmological origin. Current best estimates for the rate of FRBs is several thousand per sky per day at radio frequencies near 1.4 GHz. Even with so high a rate, to date, fewer than 20 FRBs have been reported, with one source showing repeated bursts. In this talk I will describe known FRB properties including what is known about the lone repeating source, as well as models for the origin of these mysterious events. I will also describe the CHIME radio telescope, currently under construction in Canada. Thanks to its great sensitivity and unprecedented field-of-view, CHIME promises major progress on FRBs.

Long-term determination of energetic electron precipitation into the atmosphere from AARDDVARK subionospheric VLF observations

NASA Astrophysics Data System (ADS)

Neal, Jason J.; Rodger, Craig J.; Clilverd, Mark A.; Thomson, Neil R.; Raita, Tero; Ulich, Thomas

2015-03-01

We analyze observations of subionospherically propagating very low frequency (VLF) radio waves to determine outer radiation belt energetic electron precipitation (EEP) flux magnitudes. The radio wave receiver in Sodankylä, Finland (Sodankylä Geophysical Observatory) observes signals from the transmitter with call sign NAA (Cutler, Maine). The receiver is part of the Antarctic-Arctic Radiation-belt Dynamic Deposition VLF Atmospheric Research Konsortia (AARDDVARK). We use a near-continuous data set spanning November 2004 until December 2013 to determine the long time period EEP variations. We determine quiet day curves over the entire period and use these to identify propagation disturbances caused by EEP. Long Wave Propagation Code radio wave propagation modeling is used to estimate the precipitating electron flux magnitudes from the observed amplitude disturbances, allowing for solar cycle changes in the ambient D region and dynamic variations in the EEP energy spectra. Our method performs well during the summer months when the daylit ionosphere is most stable but fails during the winter. From the summer observations, we have obtained 693 days worth of hourly EEP flux magnitudes over the 2004-2013 period. These AARDDVARK-based fluxes agree well with independent satellite precipitation measurements during high-intensity events. However, our method of EEP detection is 10-50 times more sensitive to low flux levels than the satellite measurements. Our EEP variations also show good agreement with the variation in lower band chorus wave powers, providing some confidence that chorus is the primary driver for the outer belt precipitation we are monitoring.

Energy mode distribution: An analysis of the ratio of anti-Stokes to Stokes amplitudes generated by a pair of counterpropagating Langmuir waves

NASA Astrophysics Data System (ADS)

Simões Júnior, F. J. R.; Alves, M. V.; Rizzato, F. B.

2005-12-01

Results from plasma wave experiments in spacecrafts give support to nonlinear interactions involving Langmuir, electromagnetic, and ion-acoustic waves in association with type III solar radio bursts. Starting from a general form of Zakharov equation (Zakharov, V.E., 1985. Collapse and self-focusing of Langmuir waves. Hand-book of Plasma Physics Cap.2, 81 121) the equations for electric fields and density fluctuations (density gratings) induced by a pair of counterpropagating Langmuir waves are obtained. We consider the coupling of four triplets. Each two triplets have in common the Langmuir pump wave (forward or backward wave) and a pair of independent density gratings. We numerically solve the dispersion relation for the system, extending the work of (Alves, M.V., Chian, A.C.L., Moraes, M.A.E., Abalde, J.R., Rizzato, F.B., 2002. A theory of the fundamental plasma emission of type- III solar radio bursts. Astronomy and Astrophysics 390, 351 357). The ratio of anti-Stokes (AS) (ω0+ω) to Stokes (S) (ω0-ω) electromagnetic mode amplitudes is obtained as a function of the pump wave frequency, wave number, and energy. We notice that the simultaneous excitation of AS and S distinguishable modes, i.e., with Re{ω}=ω≠0, only occurs when the ratio between the pump wave amplitudes, r is ≠1 and the pump wave vector k0 is <(13)W01/2, W0 being the forward pump wave energy. We also observe that the S mode always receives more energy.

Radio interferometry: Techniques for Geodesy. [conference

NASA Technical Reports Server (NTRS)

1980-01-01

Progress in the development and application of radio interferometry as a tool for geophysical research is reported and discussed. Among the topics reviewed are: Surveys of is the Seventies, Movements, Terrestrial and Celestial, Degrees Kelvin and Degrees of Phase, the Mark 3 VLBI System, Waves of the Future and other Emissions, and Adherence and Coherence in Networks, and Plans.

The Coherer: With Simple Demonstrations of the Generation, Propagation and Detection of Radio Waves

ERIC Educational Resources Information Center

Mills, Allan

2010-01-01

A coherer is a bistable device based on metal filings loosely confined between solid metal electrodes. This granular material normally exhibits a very high electrical resistance (tens of kilohms), but passage of the high-frequency current generated by reception of a radio signal causes it to "cohere" into a comparatively low resistance condition…

Low-Frequency VLA Observations of Abell 754: Evidence for a Cluster Radio Halo and Possible Radio Relics

DTIC Science & Technology

2001-10-01

core passage of the dark matter subcluster, was not violent enough to produce a shock wave in the dense main cluster core. The core was only...such as Chandra. At later merger stages, turbulent gas motion, which is stirred by violently relaxing dark matter cores, should have erased many of