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1

Ionospheric scintillations of geostationary satellite radio waves  

Microsoft Academic Search

Observations of the scintillations associated with the major geomagnetic storms occurring on July 14 and September 7, 1982 are described. On July 14, relatively weak and long-lasting scintillations were observed on 136-MHz radio wave from the geostationary satellite, ETS-II. These scintillations have features somewhat different from those under geomagnetically quiet conditions: (1) they appeared at local times between 0 h

H. Kumagai; T. Ogawa; T. Hori

1986-01-01

2

Radio wave scintillations at equatorial regions  

NASA Technical Reports Server (NTRS)

Radio waves, passing through the atmosphere, experience amplitude and phase fluctuations know as scintillations. A characterization of equatorial scintillation, which has resulted from studies of data recorded primarily in South America and equatorial Africa, is presented. Equatorial scintillation phenomena are complex because they appear to vary with time of day (pre-and postmidnight), season (equinoxes), and magnetic activity. A wider and more systematic geographical coverage is needed for both scientific and engineering purposes; therefore, it is recommended that more observations should be made at earth stations (at low-geomagnetic latitudes) to record equatorial scintillation phenomena.

Poularikas, A. D.

1972-01-01

3

Modeling radio scattering and scintillation observations of the inner solar wind using oblique Alfvén\\/ion cyclotron waves  

Microsoft Academic Search

Radio scattering and scintillation observations of the near-Sun solar wind are shown to be dominated by effects associated with obliquely propagating Alfvén\\/ion cyclotron waves. We base this on a modeling of structure functions from angular\\/spectral broadening observations and velocity measurements from interplanetary scintillation (IPS) observations. A simple damped-WKB model was found inadequate, as Landau damping erodes the spectrum faster than

John K. Harmon; William A. Coles

2005-01-01

4

Spacecraft Radio Scintillation and Solar System Exploration  

NASA Technical Reports Server (NTRS)

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.

Woo, Richard

1993-01-01

5

Gravitational wave scintillation by a stellar cluster  

E-print Network

The diffraction effects on gravitational waves propagating through a stellar cluster are analyzed in the relevant approximation of Fresnel diffraction limit. We find that a gravitational wave scintillation effect - similar to the radio source scintillation effect - comes out naturally, implying that the gravitational wave intensity changes in a characteristic way as the observer moves.

G. Congedo; F. De Paolis; P. Longo; A. A. Nucita; D. Vetrugno

2006-10-27

6

Some new results on the statistics of radio wave scintillation. I - Empirical evidence for Gaussian statistics  

NASA Technical Reports Server (NTRS)

This paper presents an analysis of ionospheric scintillation data which shows that the underlying statistical structure of the signal can be accurately modeled by the additive complex Gaussian perturbation predicted by the Born approximation in conjunction with an application of the central limit theorem. By making use of this fact, it is possible to estimate the in-phase, phase quadrature, and cophased scattered power by curve fitting to measured intensity histograms. By using this procedure, it is found that typically more than 80% of the scattered power is in phase quadrature with the undeviated signal component. Thus, the signal is modeled by a Gaussian, but highly non-Rician process. From simultaneous UHF and VHF data, only a weak dependence of this statistical structure on changes in the Fresnel radius is deduced. The signal variance is found to have a nonquadratic wavelength dependence. It is hypothesized that this latter effect is a subtle manifestation of locally homogeneous irregularity structures, a mathematical model proposed by Kolmogorov (1941) in his early studies of incompressible fluid turbulence.

Rino, C. L.; Livingston, R. C.; Whitney, H. E.

1976-01-01

7

A decametric wavelength radio telescope for interplanetary scintillation observations  

NASA Technical Reports Server (NTRS)

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.

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

1975-01-01

8

Radio Wave Propagation  

Microsoft Academic Search

Electromagnetic radio waves traveling within earth's atmosphere are called terrestrial waves, and communications between two or more points on earth is called terrestrial radio communications. Terrestrial waves are influenced by the atmosphere and earth itself. In terrestrial radio communications, waves can be propagated in several ways, depending on the type of system and the environment. Electromagnetic waves also travel in

S. Venkatesh

2007-01-01

9

Nocturnal disturbances of total electron content and their correlation with VHF radio wave scintillations in the Pacific-Asia region  

Microsoft Academic Search

We have collected 136-MHz Faraday rotation and scintillation data of signals transmitted by the satellite ETS-2 and received at 13 ground stations in the Pacific-Asia region. Using this data base, a statistical analysis has been carried out by correlating the nocturnal TEC disturbances with the amplitude scintillations. Also presented are several typical events observed simultaneously over this network. An important

J. S. Xu; K. C. Yeh

1993-01-01

10

Radio scintillations observed during atmospheric occultations of Voyager: Internal gravity waves at Titan and magnetic field orientations at Jupiter and Saturn. Ph.D. Thesis  

NASA Technical Reports Server (NTRS)

The refractive index of planetary atmospheres at microwave frequencies is discussed. Physical models proposed for the refractive irregularities in the ionosphere and neutral atmosphere serve to characterize the atmospheric scattering structures, and are used subsequently to compute theoretical scintillation spectra for comparison with the Voyager occultation measurements. A technique for systematically analyzing and interpreting the signal fluctuations observed during planetary occultations is presented and applied to process the dual-wavelength data from the Voyager radio occultations by Jupiter, Saturn, and Titan. Results concerning the plasma irregularities in the upper ionospheres of Jupiter and Saturn are reported. The measured orientation of the irregularities is used to infer the magnetic field direction at several locations in the ionospheres of these two planets; the occultation measurements conflict with the predictions of Jovian magnetic field models, but generally confirm current models of Saturn's field. Wave parameters, including the vertical fluxes of energy and momentum, are estimated, and the source of the internal gravity waves discovered in Titan's upper atmosphere is considered.

Hinson, D. P.

1983-01-01

11

Radio-wave propagation in space  

NASA Astrophysics Data System (ADS)

The characteristics of radio waves propagating in space are discussed, with attention given to their astronomical applications. Physical phenomena influencing the propagation of radio waves in the earth's atmospheres are considered, including atmospheric absorption, attenuation and refraction effects. The uses of radar interferometry in interstellar and interplanetary astronomy are described and radar data are presented concerning coronal scattering; interplanetary scintillations; relativistic time delay measurements; and gravitational lens effects. The effect of the gravitational field of interstellar space on the propagation of radio waves is also discussed.

Iakovlev, O. I.

12

Riding the Radio Waves  

NSDL National Science Digital Library

Students learn how AM radios work through basic concepts about waves and magnetic fields. Waves are first introduced by establishing the difference between transverse and longitudinal waves, as well as identifying the amplitude and frequency of given waveforms. Then students learn general concepts about magnetic fields, leading into how radio waves are created and transmitted. Several demonstrations are performed to help students better understand these concepts. This prepares students to be able to comprehend the functionig of the AM radios they will build during the associated activity.

Techtronics Program,

13

Interplanetary scintillation observations with the Cocoa Cross radio telescope  

NASA Technical Reports Server (NTRS)

Physical and electrical parameters for the 34.3-MHz Cocoa Cross radio telescope are given. The telescope is dedicated to the determination of solar-wind characteristics in and out of the ecliptic plane through measurement of electron-density irregularity structure as determined from IPS (interplanetary scintillation) of natural radio sources. The collecting area (72,000 sq m), angular resolution (0.4 deg EW by 0.6 deg NS), and spatial extent (1.3 km EW by 0.8 km NS) make the telescope well suited for measurements of IPS index and frequency scale for hundreds of weak radio sources without serious confusion effects.

Cronyn, W. M.; Shawhan, S. D.; Erskine, F. T.; Huneke, A. H.; Mitchell, D. G.

1976-01-01

14

Radio Waves and the Ionosphere  

NSDL National Science Digital Library

In this activity students will discover that when amplitude modulated (AM) radio waves travel from transmitter to a receiver far away, they have to bounce off the underside of the ionosphere and that the waves lose some of their energy each time they are reflected. Students will learn that although this is normally a small amount, it can be several times larger during a solar storm. They also learn that radio signals passing through this layer and bouncing off the ionosphere higher up, have some or all of their intensity absorbed. During this activity students will calculate the percent of change, determine the final percentage of radio wave strength at the receiving station, and will learn that solar flares can cause disruptions in radio waves.

Susan Higley

15

Radio wave propagation aspects for future digital mobile radio systems  

Microsoft Academic Search

The authors investigate the possibility of using frequencies around 1700 MHz for mobile radio communication, focusing on a comparison of the characteristics of 900 MHz and 1700 MHz radio wave propagation. Radio-wave propagation for mobile radio is broken down into large-scale and small-scale effects. The large-scale variations depend on the BS (base station) to MS (mobile station) distance and also

Mats Nilson; Sven Nordin; M. Mizuno

1988-01-01

16

Echoes of Radio Waves  

Microsoft Academic Search

Following the magneto-ionic theory of Appleton-Hartree, an explanation for the existence of echoes of long delay has been formulated. Realizing that the ordinary and extraordinary rays have opposite senses of polarization, it may be seen that one of these rays will penetrate the E layer while the other may not. The wave which penetrates the E layer will be reflected

N. Janco

1934-01-01

17

Solar wind interaction with the ionosphere of Venus inferred from radio scintillation measurements  

Microsoft Academic Search

This paper presents the first S-band (2.3 GHz) radio scintillations observed in the ionosphere of Venus and discovered when the Pioneer Venus Orbiter spacecraft traversed the ionosphere of Venus. In situ plasma measurements as well as propagation calculations confirm that the scintillations are caused by electron density irregularities in the topside ionosphere of Venus below the ionopause. While these topside

Richard Woo; William L. Sjogren; A. J. Kliore; J. G. Luhmann; Larry H. Brace

1989-01-01

18

Radio Wave Emission from the Outer Planets  

E-print Network

Radio Wave Emission from the Outer Planets P. Zarka LESIA, Observatoire de Paris, Meudon #12;All properties of Auroral Radio Emissions : · very intense #12;[Zarka, 2000] Earth's ionospheric cutoff #12

Demoulin, Pascal

19

Theory of thin screen scintillations for a spherical wave  

NASA Technical Reports Server (NTRS)

A thin screen scintillation theory for a spherical wave is presented under the 'quasi-optical' approximation. We calculate the 'scattering angle', the 'observed angle', the intensity correlation function and the temporal pulse broadening for the random wave. It is found that as the wave propagates outward away from the phase screen, the correlation scale of the intensity fluctuation increases linearly while the 'observed angle' decreases linearly. The calculations are carried out for both Gaussian and power-law spectra of the turbulent medium.

Lee, L. C.

1976-01-01

20

Solar wind interaction with the ionosphere of Venus inferred from radio scintillation measurements  

NASA Technical Reports Server (NTRS)

The observation of S-band (2.3 GHz) radio scintillations in the ionosphere of Venus by the Pioneer Venus Orbiter is reported. In situ plasma measurements and propagation calculations show that the scintillations are caused by electron density irregularities in the topside ionosphere of Venus below the ionopause. It is suggested that these topside plasma irregularities are associated with the penetration of large-scale magnetic fields in the ionosphere. It is found that the disturbed plasma and the scintillations are a manifestation of high-dynamic solar wind interaction with the ionosphere.

Woo, Richard; Sjogren, William L.; Kliore, Arvydas J.; Luhmann, Janet G.; Brace, Larry H.

1989-01-01

21

Solar wind interaction with the ionosphere of Venus inferred from radio scintillation measurements  

SciTech Connect

This paper presents the first S-band (2.3 GHz) radio scintillations observed in the ionosphere of Venus and discovered when the Pioneer Venus Orbiter spacecraft traversed the ionosphere of Venus. In situ plasma measurements as well as propagation calculations confirm that the scintillations are caused by electron density irregularities in the topside ionosphere of Venus below the ionopause. While these topside plasma irregularities have not been studied before, simultaneous magnetic field measurements presented here reveal that they are associated with the penetration of large-scale magnetic fields in the ionosphere. Previous studies based on extensive magnetic field measurements have shown that the presence of large-scale magnetic fields occurs in the subsolar region when the solar wind dynamic pressure exceeds the ionospheric plasma pressure. As with the large-scale magnetic fields, the disturbed plasma and resulting scintillations are therefore a manifestation of high-dynamic solar wind interaction with the ionosphere. Since the scintillations only occur in the subsolar region of Venus, the global morphology of ionospheric scintillations at Venus is different from that of the terrestrial ionosphere, where scintillations are observed in both polar and equatorial regions, with peaks occurring during nighttime. This difference apparently stems from the fact that Venus is not a magnetic planet. The authors also demonstrate that the disturbed plasma produced by the high-dynamic solar wind interaction can be remotely sensed by scintillations during radio occultation measurements, that is, when the spacecraft is outside the ionosphere.

Woo, R.; Sjogren, W.L.; Kliore, A.J. (California Institute of Technology, Pasadena (USA)); Luhmann, J.G. (Univ. of California, Los Angeles (USA)); Brace, L.H. (NASA Goddard Space Flight Center, Greenbelt, MD (USA))

1989-02-01

22

Antenna Construction and Propagation of Radio Waves.  

ERIC Educational Resources Information Center

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…

Marine Corps Inst., Washington, DC.

23

UHF Radio Wave Attenuation Factor Database  

Microsoft Academic Search

As is known each sea-going vessel is equipped with navigation, communication and other radio engineering facilities that serve to secure the safety of navigation and are chiefly operated at UHF-wave band. In developing these systems and calculating the energy potential for a necessary coverage range one should be well aware of the radio signal attenuation processes on a propagation path.

S. I. Khomenko; V. L. Kostina; I. M. Mytsenko; A. N. Roenko

2007-01-01

24

Amplitude fluctuations of decimeter and centimeter radio waves emmitted by the Venera-15 and Venera-16 space probes during propagation through the solar plasma  

Microsoft Academic Search

Results are presented of investigations into the fluctuations of centimeter and decimeter radio waves in the solar plasma. The experimental dependence of the scintillation index on distance of closest point of approach in the range 2.3-100 solar radii is given. Dependence of the scintillation index on wavelength and solar activity is discussed. The dependence of the variance of the fluctuations

O. I. Yakovlev; A. I. Efimov; E. P. Molotov; S. N. Rubtsov; V. P. Yakubov; A. I. Kucheryavenkov; A. S. Kaftonov

1988-01-01

25

Wave-wave interactions in solar type III radio bursts  

SciTech Connect

The high time resolution observations from the STEREO/WAVES experiment show that in type III radio bursts, the Langmuir waves often occur as localized magnetic field aligned coherent wave packets with durations of a few ms and with peak intensities well exceeding the strong turbulence thresholds. Some of these wave packets show spectral signatures of beam-resonant Langmuir waves, down- and up-shifted sidebands, and ion sound waves, with frequencies, wave numbers, and tricoherences satisfying the resonance conditions of the oscillating two stream instability (four wave interaction). The spectra of a few of these wave packets also contain peaks at f{sub pe}, 2f{sub pe} and 3 f{sub pe} (f{sub pe} is the electron plasma frequency), with frequencies, wave numbers and bicoherences (computed using the wavelet based bispectral analysis techniques) satisfying the resonance conditions of three wave interactions: (1) excitation of second harmonic electromagnetic waves as a result of coalescence of two oppositely propagating Langmuir waves, and (2) excitation of third harmonic electromagnetic waves as a result of coalescence of Langmuir waves with second harmonic electromagnetic waves. The implication of these findings is that the strong turbulence processes play major roles in beam stabilization as well as conversion of Langmuir waves into escaping radiation in type III radio bursts.

Thejappa, G. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); MacDowall, R. J. [NASA/Goddard Space Flight Center, Greenbelt MD 20771 (United States)

2014-02-11

26

Information Content in Radio Waves: Student Investigations in Radio Science  

NASA Astrophysics Data System (ADS)

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'.

Jacobs, K.; Scaduto, T.

2013-12-01

27

CONSTRAINING THE VELA PULSAR'S RADIO EMISSION REGION USING NYQUIST-LIMITED SCINTILLATION STATISTICS  

SciTech Connect

Using a novel technique, we achieve {approx}100 picoarcsec resolution and set an upper bound of less than 4 km for the characteristic size of the Vela pulsar's emission region. Specifically, we analyze flux-density statistics of the Vela pulsar at 760 MHz. Because the pulsar exhibits strong diffractive scintillation, these statistics convey information about the spatial extent of the radio emission region. We measure both a characteristic size of the emission region and the emission sizes for individual pulses. Our results imply that the radio emission altitude for the Vela pulsar at this frequency is less than 340 km.

Johnson, M. D.; Gwinn, C. R. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Demorest, P., E-mail: michaeltdh@physics.ucsb.edu, E-mail: cgwinn@physics.ucsb.edu, E-mail: pdemores@nrao.edu [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22093 (United States)

2012-10-10

28

Can You Hear Them Now?: Investigating Radio Waves  

Microsoft Academic Search

This article presents a description of a five-step (5E) learning cycle lesson designed to engage students in the study of electromagnetic radiation in the form of radio waves. Students collect data on the strength and distance of radio waves heard during the day and after sunset. They then compile and analyze these sets of data and relate radio wave travel

Kevin C. Wise

2006-01-01

29

Strong scintillations during atmospheric occultations Theoretical intensity spectra. [radio scattering during spacecraft occultations by planetary atmospheres  

NASA Technical Reports Server (NTRS)

Each of the two Voyager spacecraft launched in 1977 has completed a reconnaissance of the Jovian and Saturnian systems. In connection with occultation experiments, strong scintillations were observed. Further theoretical work is required before these scintillations can be interpreted. The present study is, therefore, concerned with the derivation of a theory for strong scattering during atmospheric occultation experiments, taking into account as fundamental quantity of interest the spatial spectrum (or spectral density) of intensity fluctuations. Attention is given to a theory for intensity spectra, and numerical calculations. The new formula derived for Phi-i accounts for strong scattering of electromagnetic waves during atmospheric occultations.

Hinson, D. P.

1986-01-01

30

Detection Of Cosmic Rays Air Showers Using Radio Antenna Arrays And Scintillation Counters  

NASA Astrophysics Data System (ADS)

In this progress report we describe a test bench developed in order to evaluate the performance of radio antennas and other gaseous detectors in detecting air showers initiating by cosmic rays. This test bench is based on an array of HELYCON scintillation counters and is used to operate a digital radio telescope. The results of this research and development activity will be applied in developing a sea top calibration array of an underwater neutrino telescope. We also describe the performance of a single HELYCON station in detecting and reconstructing showers as well as on the pilot operation of a single low frequency radio antenna in order to develop techniques to suppress the contribution of the anthropogenic RF background originated from human activities.

Papageorgiou, K.; Tzamarias, S.; Gkialas, I.; Tsirigotis, A.; Bourlis, G.; Manthos, I.; Avgitas, G.

2014-06-01

31

Eddy diffusion coefficient for the atmosphere of Venus from radio scintillation measurements  

NASA Technical Reports Server (NTRS)

Estimates are obtained of the vertical mass eddy diffusion coefficient of the Venus atmosphere in the region of turbulence near 60 km on the basis of radio scintillations observed during radio occultation by the atmosphere. The structure constant estimated from Pioneer Venus orbit 18 entrance radio occultation measurements is used, under the assumption that the turbulence is generated by wind-shear, to derive a value of 40,000 sq cm/sec for the vertical mass eddy diffusion coefficient, together with an energy dissipation rate of 20 sq cm/sec and a temperature fluctuation dissipation rate of 0.001 K-squared/sec. Results are noted to fall within the range measured for the earth's troposphere, however, indicate that small-scale turbulence is probably the dominant mechanism for vertical transport near the tropopause in the Venus atmosphere.

Woo, R.; Ishimaru, A.

1981-01-01

32

Near-Sun solar wind consequences of solar structure and dynamic phenomena observed by radio scintillation measurements  

NASA Technical Reports Server (NTRS)

Since radio propagation measurements using either natural or spacecraft radio signals are used for probing the solar wind in the vicinity of the sun, they represent a key tool for studying the interplanetary consequences of solar structure and dynamic phenomena. New information on the near sun consequences was obtained from radio scintillation observations of coherent spacecraft signals. The results covering density fluctuations, fractional density fluctuations, coronal streamers, heliospheric current sheets, coronal mass ejections and interplanetary shocks are reviewed. A joint ICE S-band (13 cm wavelength) Doppler scintillation measurement with the SOHO white-light coronograph (LASCO) is described.

Woo, Richard

1994-01-01

33

Radio-wave propagation in a statistically inhomogeneous medium  

Microsoft Academic Search

The Helmholtz equation describing the propagation of radio waves in an inhomogeneous atmosphere is solved in the framework of geometrical optics with consideration of the existence of traveling waves. The analysis has application to the scattering of radio waves in the ionosphere.

V. D. Gusev

1978-01-01

34

ULYSSES radio and plasma wave observations in the Jupiter environment  

Microsoft Academic Search

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

R. G. Stone; B. M. Pedersen; C. C. Harvey; P. Canu; N. Cornilleau-Wehrlin; M. D. Desch; C. de Villedary; J. Fainberg; W. M. Farrell; K. Goetz; R. A. Hess; S. Hoang; M. L. Kaiser; P. J. Kellogg; A. Lecacheux; N. Lin; R. J. MacDowall; R. Manning; C. A. Meetre; N. Meyer-Vernet; M. Moncuquet; V. Osherovich; M. J. Reiner; A. Tekle; J. Thiessen; P. Zarka

1992-01-01

35

Radio continua modulated by waves: Zebra patterns in solar and pulsar radio spectra?  

NASA Astrophysics Data System (ADS)

Aims: We aim to answer the question how waves with plasma density variations affect the radio continua generated by the plasma emission mechanism. Methods: We built a simple semi-empirical model of the radio continuum modulation. Assuming that the waves with density variations are in the source of this radio continuum, we modeled the artificial radio spectrum, which we compared with observed spectra. Results: We show that the waves with density variations modulate the radio continua generated by the plasma emission mechanism. Considering a single slow magnetoacoustic wave, we model the radio spectra, which resemble solar zebra patterns. We show that this modulation generates zebra effects even when the radio continuum is composed of many spiky bursts. Generalizing from one single wave to a wave turbulence we find that the computed radio spectrum is similar to so-called lace bursts. Finally, using the same procedure, but for fast magnetoacoustic waves, we modeled the radio spectrum similar to that observed during the interpulse phase of the radio emission of the Crab Nebula pulsar.

Karlický, M.

2013-04-01

36

Irregularities in ionospheric plasma clouds: Their evolution and effect on radio communication  

Microsoft Academic Search

Both satellite radio communications, which travel through the Earth's ionosphere, and high frequency (HF) sky wave circuits, which use the ionosphere as a refracting medium, can be strongly affected by radio wave scintillation. High altitude nuclear explosions cause scintillation (by strongly disturbing the ionosphere) and thus severely degrade satellite radio communications over a large region. Since further atmospheric nuclear tests

J. F. Vesecky; J. W. Chamberlain; J. M. Cornwall; D. A. Hammer; F. W. Perkins

1980-01-01

37

Irregularities in ionospheric plasma clouds: their evolution and effect on radio communication. Technical report  

Microsoft Academic Search

Both satellite radio communications, which travel through the Earth's ionosphere, and high frequency (HF) sky wave circuits, which use the ionosphere as a refracting medium, can be strongly affected by radio wave scintillation. High altitude nuclear explosions cause scintillation (by strongly disturbing the ionosphere) and thus severely degrade satellite radio communications over a large region. Since further atmospheric nuclear tests

J. F. Vesecky; J. W. Chamberlain; J. M. Cornwall; D. A. Hammer; F. W. Perkins

1980-01-01

38

Radio-wave propagation for space communications systems  

NASA Technical Reports Server (NTRS)

The most recent information on the effects of Earth's atmosphere on space communications systems is reviewed. The design and reliable operation of satellite systems that provide the many applications in space which rely on the transmission of radio waves for communications and scientific purposes are dependent on the propagation characteristics of the transmission path. The presence of atmospheric gases, clouds, fog, precipitation, and turbulence causes uncontrolled variations in the signal characteristics. These variations can result in a reduction of the quality and reliability of the transmitted information. Models and other techniques are used in the prediction of atmospheric effects as influenced by frequency, geography, elevation angle, and type of transmission. Recent data on performance characteristics obtained from direct measurements on satellite links operating to above 30 GHz have been reviewed. Particular emphasis has been placed on the effects of precipitation on the Earth/space path, including rain attenuation, and ice particle depolarization. Other factors are sky noise, antenna gain degradation, scintillations, and bandwidth coherence. Each of the various propagation factors has an effect on design criteria for communications systems. These criteria include link reliability, power margins, noise contribution, modulation and polarization factors, channel cross talk, error rate, and bandwidth limitations.

Ippolito, L. J.

1981-01-01

39

Magnetospheric radio and plasma wave research - 1987-1990  

SciTech Connect

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.

Kurth, W.S. (USAF, Geophysics Laboratory, Hanscom AFB, MA (United States))

1991-01-01

40

Analysis of Gravity Waves from Radio Occultation Measurements  

E-print Network

Analysis of Gravity Waves from Radio Occultation Measurements Martin Lange and Christoph Jacobi. In the height range 10-30 km atmospheric gravity waves lead to pe- riodic perturbations of the background gravity waves in the range 100-1000 km horizontal and 1-10 km vertical wavelength is investi- gated

41

Radio Waves for Space-Based Construction  

NASA Astrophysics Data System (ADS)

This paper follows up on the idea of using potential fields for automatic construction of massive objects of desired shape in Space. In STAIF03, we showed the commonality between the theories for acoustic and optical positioning/shaping methods. Using this theoretical framework, we developed a simple engineering estimation scheme to predict the acceleration per unit intensity. The radiation pressure is achieved by interaction of electromagnetic waves and particles of a given dielectric material and size. The theory was limited to the Rayleigh domain, where particle size is much less than the wavelength, and isotropic scattering could be assumed. With this theoretical framework in hand, we now consider how electromagnetic waves could be utilized in a Space-based construction project. In the test case project, the question of how to construct a safe radiation shelter for humans, in the Near-Earth Object (NEO) region is considered. NEO material, pulverized to an average particle size of 0.1m radius, is formed into desired shapes using the radiation pressure and gradient forces experienced by dielectric objects in a standing-wave field of radio waves. The force field is produced by solar-powered transmitter/antenna carrying spacecraft, which are positioned in formation around the particle cloud to set up a resonant field of the desired mode. As a test case, formation of cylindrical shells is considered. The field level is set to induce an average particle acceleration of a millionth of an Earth-surface gravitational acceleration. Once in position, the particles are fused by solar-powered energy beams through a sintering process. Results show that 50m diameter, 50m-tall cylinders can be formed in the course of 12 to 13 hours per cylinder. Order-of-magnitude arguments show that the selected acceleration level is adequate to overcome noise from all other forces in this region. The paper also begins the consideration of tradeoffs between solar collector area, number of resonators, and capacitive storage-discharge of energy in the fabrication process.

Komerath, Narayanan M.; Wanis, Sameh S.

2004-02-01

42

Plasma and radio waves from Neptune: Source mechamisms and propagation  

NASA Technical Reports Server (NTRS)

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.

Menietti, J. Douglas

1994-01-01

43

The Velocity of Radio Waves over Short Paths  

Microsoft Academic Search

The velocity of radio waves was measured directly in the following manner. Two radio stations were set up on frequencies of 3492.5 and 2398 kilocycles, respectively. One station was fixed while the other was portable. The fixed station sent out pulses which were received at the portable station. A thyratron control set off return pulses which came back to the

R. C. Colwell; H. Atwood; J. E. Bailey; C. O. Marsh

1942-01-01

44

BotEC: The Distance Radio Waves Have Traveled  

NSDL National Science Digital Library

Question We have been broadcasting radio waves in all directions since the development of radio and television stations. How far could you be from the Earth and detect the faint signals of an early Star Trek broadcast? Have signals from Star Trek reached the nearest star yet?

Barb Tewksbury

45

Spectral broadening and phase scintillation measurements using interplanetary spacecraft radio links during the peak of solar cycle 23  

Microsoft Academic Search

When an interplanetary spacecraft is in a solar superior conjunction configuration, the received radio signals are degraded by several effects that generally increase in magnitude as the angle between the spacecraft and the Sun (Sun-Earth-Probe or SEP angle) decreases as viewed by a terrestrial tracking station. During periods of quiescent solar activity, phase scintillation and spectral broadening follow well-defined trends

David D. Morabito

2009-01-01

46

High pressure gas scintillation drift chambers with wave-shifter fiber readout. II  

NASA Technical Reports Server (NTRS)

Results from a prototype high-pressure xenon gas scintillation drift chamber using a novel wave-shifter fiber readout scheme are presented. The primary scintillation light yield was measured to be one photon per 76 + or - 12 eV deposited energy. Initial results on the chamber are presented for two-interaction separation (less than 4 mm in the drift direction and about 7 mm orthogonal to the drift); for position resolution (less than 400 microns rms in the plane orthogonal to the drift direction); and for energy resolution (less than 6 percent FWHM at 122 keV).

Parsons, A.; Edberg, T. K.; Sadoulet, B.; Weiss, S.; Wilkerson, J.

1990-01-01

47

Plasma and radio waves from Neptune: Source mechanisms and propagation  

NASA Technical Reports Server (NTRS)

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.

Wong, H. K.

1994-01-01

48

Stimulated scattering of intense radio waves in partially ionized space dusty plasmas  

Microsoft Academic Search

The nonlinear interaction between intense ordinary mode (O-mode) radio waves and modified magnetoacoustic waves in partially ionized space dusty plasmas is considered, including the combined action of the radio wave pressure and the electron Joule heating caused by the O-mode electric field. A set of equations containing the wave equation for the radio waves and the electron density and temperature

P. K. Shukla; B. Eliasson; L. Stenflo

2004-01-01

49

A basic atlas of radio-wave propagation  

NASA Astrophysics Data System (ADS)

Basic concepts in radio-wave propagation and system design are brought together in this volume along with all of the essential design elements required for VHF, UHF, and SHF radio. The basic topics addressed include free-space propagation path, reflection interference propagation path, diffraction propagation path, troposcatter propagation path, absorption propagation path, passive-relay propagation path, noise and S/N, fading estimation and system evaluation, and astronomy and geography.

Shibuya, Shigekazu

50

Ionospheric wave and irregularity measurements using passive radio astronomy techniques  

NASA Technical Reports Server (NTRS)

The observation of midlatitude structures using passive radio astronomy techniques is discussed, with particular attention being given to the low-frequency radio telescope at the Clark Lake Radio Observatory. The present telescope operates in the 10-125-MHz frequency range. Observations of the ionosphere at separations of a few kilometers to a few hundreds of kilometers by the lines of sight to sources are possible, allowing the determination of the amplitude, wavelength, direction of propagation, and propagation speed of ionospheric waves. Data are considered on large-scale ionospheric gradients and the two-dimensional shapes and sizes of ionospheric irregularities.

Erickson, W. C.; Mahoney, M. J.; Jacobson, A. R.; Knowles, S. H.

1988-01-01

51

Synopsis of mid-latitude radio wave absorption in Europe  

NASA Astrophysics Data System (ADS)

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.

Torkar, K. M.; Friedrich, M.

1984-05-01

52

Synopsis of Mid-latitude Radio Wave Absorption in Europe  

NASA Technical Reports Server (NTRS)

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.

Torkar, K. M.; Friedrich, M.

1984-01-01

53

Excitation of parametric instabilities by radio waves in the ionosphere.  

NASA Technical Reports Server (NTRS)

The excitation of parametric instabilities by radio waves in a magnetoplasma is discussed. A uniform medium is assumed and linear approximations are used. Excitation by a pump wave of ordinary polarization is hardly affected by the magnetic field. Low or zero frequency ion waves and high frequency Langmuir waves are excited simultaneously. For an extraordinary pump wave, the excited high frequency electrostatic waves are in the Bernstein mode. The threshold is slightly higher and excitation can occur only within certain 'allowed' frequency bands. A new type of parametric instability in which the excited waves are electromagnetic in nature and which is more strongly affected by the inhomogeneous nature of the medium is discussed qualitatively.

Fejer, J. A.; Leer, E.

1972-01-01

54

Improved spacecraft radio science using an on-board atomic clock: Application to gravitational wave searches  

SciTech Connect

Recent advances in space-qualified atomic clocks (low-mass, low power-consumption, frequency stability comparable to that of ground-based clocks) can enable interplanetary spacecraft radio science experiments at unprecedented Doppler sensitivities. The addition of an on-board digital receiver would allow the up- and down-link Doppler frequencies to be measured separately. Such separate, high-quality measurements allow optimal data combinations that suppress the currently leading noise sources: phase scintillation noise from the Earth's atmosphere and Doppler noise caused by mechanical vibrations of the ground antenna. Here we provide a general expression for the optimal combination of ground and on-board Doppler data and compute the sensitivity such a system would have to low-frequency gravitational waves (GWs). Assuming a plasma scintillation noise calibration comparable to that already demonstrated with the multilink CASSINI radio system, the space-clock/digital-receiver instrumentation enhancements would give GW strain sensitivity of 3.7x10{sup -14} Hz{sup -1/2} for randomly polarized, monochromatic GW signals isotropically distributed over the celestial sphere, over a two-decade ({approx}0.0001-0.01 Hz) region of the low-frequency band. This is about an order of magnitude better than currently achieved with traditional two-way coherent Doppler experiments. The utility of optimally combining simultaneous up- and down-link observations is not limited to GW searches. The Doppler tracking technique discussed here could be performed at minimal incremental cost to improve also other radio science experiments (i.e., tests of relativistic gravity, planetary and satellite gravity field measurements, atmospheric and ring occultations) on future interplanetary missions.

Tinto, Massimo; Dick, George J.; Prestage, John D.; Armstrong, J. W. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109 (United States)

2009-05-15

55

Improved spacecraft radio science using an on-board atomic clock: application to gravitational wave searches  

E-print Network

Recent advances in space-qualified atomic clocks (low-mass, low power-consumption, frequency stability comparable to that of ground-based clocks) can enable interplanetary spacecraft radio science experiments at unprecedented Doppler sensitivities. The addition of an on-board digital receiver would allow the up- and down-link Doppler frequencies to be measured separately. Such separate, high-quality measurements allow optimal data combinations that suppress the currently-leading noise sources: phase scintillation noise from the Earth's atmosphere and Doppler noise caused by mechanical vibrations of the ground antenna. Here we provide a general expression for the optimal combination of ground and on-board Doppler data and compute the sensitivity such a system would have to low-frequency gravitational waves (GWs). Assuming a plasma scintillation noise calibration comparable to that already demonstrated with the multi-link CASSINI radio system, the space-clock/digital-receiver instrumentation enhancements would give GW strain sensitivity of $2.0 \\times 10^{-17}$ for randomly polarized, monochromatic GW signals over a two-decade ($\\sim0.0001-0.01$ Hz) region of the low-frequency band. This is about an order of magnitude better than currently achieved with traditional two-way coherent Doppler experiments. The utility of optimally combining simultaneous up- and down-link observations is not limited to GW searches. The Doppler tracking technique discussed here could be performed at minimal incremental cost to also improve other radio science experiments (i.e. tests of relativistic gravity, planetary and satellite gravity field measurements, atmospheric and ring occultations) on future interplanetary missions.

Massimo Tinto; George J. Dick; John D. Prestage; J. W. Armstrong

2008-12-13

56

Mitigation of Effects of the Atmosphere on Radio Wave Propagation  

Microsoft Academic Search

Radio waves traveling through free space have little or no external influence on them. But when such signals are traversed through the atmosphere, their effective propagation will be determined by atmospheric factors. Some of these atmospheric factors are variations in geographic height, differences in geographic locations, and changes in time (day, night, season, etc.). This paper has critically looked into

A. S. Adegoke

57

Millimeter wave radio telescopes: Gain and pointing characteristics  

Microsoft Academic Search

The basic gain and pointing characteristics of millimeter-wave radio telescopes are described in this paper. Formal definitions of relevant telescope parameters are given. Performance limits set by conventional technology are discussed and compared with measurements of existing telescopes. Methods are also suggested for minimizing pointing errors.

B. L. Ulich

1981-01-01

58

Millimeter wave radio telescopes - Gain and pointing characteristics  

Microsoft Academic Search

The basic gain and pointing characteristics of millimeter-wave radio telescopes are described in this paper. Formal definitions of relevant telescope parameters are given. Performance limits set by conventional technology are discussed and compared with measurements of existing telescopes. Methods are also suggested for minimizing pointing errors.

B. L. Ulich

1981-01-01

59

Passive chip-less millimeter wave Radio Frequency Identification  

Microsoft Academic Search

This article describe a passive, chip-less millimeter wave radio frequency identification (RFID) technology that uses an array of microscopic resonant elements implanted into the paper, cardboard, and plastic substrates typically used for an optical label, such as a barcode. When illuminated with RF energy, the resonant array provides a ldquoRF Fingerprintrdquo based on parameters including density, thickness, and orientation of

Andrew Wu; Kamran Mahbobi; Houman Ghajari; Yuriy Mykula; Brian Woods

2008-01-01

60

S\\/WAVES: The Radio and Plasma Wave Investigation on the STEREO Mission  

Microsoft Academic Search

This paper introduces and describes the radio and plasma wave investigation on the STEREO Mission: STEREO\\/WAVES or S\\/WAVES.\\u000a The S\\/WAVES instrument includes a suite of state-of-the-art experiments that provide comprehensive measurements of the three\\u000a components of the fluctuating electric field from a fraction of a hertz up to 16 MHz, plus a single frequency channel near\\u000a 30 MHz. The instrument has a

J. L. Bougeret; K. Goetz; M. L. Kaiser; S. D. Bale; P. J. Kellogg; M. Maksimovic; N. Monge; S. J. Monson; P. L. Astier; S. Davy; M. Dekkali; J. J. Hinze; R. E. Manning; E. Aguilar-Rodriguez; X. Bonnin; C. Briand; I. H. Cairns; C. A. Cattell; B. Cecconi; J. Eastwood; R. E. Ergun; J. Fainberg; S. Hoang; K. E. J. Huttunen; S. Krucker; A. Lecacheux; R. J. MacDowall; W. Macher; A. Mangeney; C. A. Meetre; X. Moussas; Q. N. Nguyen; T. H. Oswald; M. Pulupa; M. J. Reiner; P. A. Robinson; H. Rucker; C. Salem; O. Santolik; J. M. Silvis; R. Ullrich; P. Zarka; I. Zouganelis

2008-01-01

61

Extra Low-Frequency Terrestrial Radio-Wave Field Calculations with the Zonal Harmonics Series  

Microsoft Academic Search

Use of the zonal harmonics series for calculating the terrestrial wave guide fields directly is described. The analysis is extended to include radio waves propagating into sea water or below the earth's surface. A sample calculation of ELF radio waves is analyzed into a direct wave and a wave that has traveled the circumference of the earth. The location of

J. Ralph Johler; Richard L. Lewis

1969-01-01

62

Numerical studies of current generation by radio-frequency traveling waves  

E-print Network

Numerical studies of current generation by radio-frequency traveling waves Charles F. F. Karney January 1979; final manuscript received 7 May 1979) By injecting radio-frequency traveling waves of the fusion power output. Recently,' the damping of high-phase-velocity radio- frequency traveling waves has

Karney, Charles

63

Radio Wave Generation by Multistream Charge Interaction  

Microsoft Academic Search

The excitation of plasma oscillations in traveling beams is reviewed; analytic and graphical methods are employed to ascertain the ranges of parameters over which wave growth may exist and to determine contours of constant amplification factor. The effect of thermal velocities is taken into account by utilizing approximations to a maxwellian distribution. It is found that the possibility of growth

J. Feinstein; H. K. Sen

1951-01-01

64

Recovery of radioisotopes from nuclear waste for radio-scintillator-luminescence energy applications  

E-print Network

Extraction of the light weight radioisotopes (LWR) 89Sr/90Sr, from the expended nuclear bars in the Fukushima reactor, should have decreased the extent of contamination during the course of the accident. 89Sr applications could pay for the extraction of 89Sr/90Sr from nuclear residues. Added value could be obtained by using 89Sr for cancer treatments. Known technologies could be used to relate into innovative ways LWR, to obtain nuclear energy at battery scale. LWR interact by contact with scintillators converting \\beta-radiation into light-energy. This would lead to manufacturing scintillator lamps which operate independently of other source of energy. These lamps could be used to generate photoelectric energy. Engineering of radioisotopes scintillator photovoltaic cells, would lead to devices without moving parts.

Alfred Bennun

2012-08-16

65

WAVES: The radio and plasma wave investigation on the wind spacecraft  

Microsoft Academic Search

The WAVES investigation on the WIND spacecraft will provide comprehensive measurements of the radio and plasma wave phenomena which occur in Geospace. Analyses of these measurements, in coordination with the other onboard plasma, energetic particles, and field measurements will help us understand the kinetic processes that are important in the solar wind and in key boundary regions of the Geospace.

J.-L. Bougeret; M. L. Kaiser; P. J. Kellogg; R. Manning; K. Goetz; S. J. Monson; N. Monge; L. Friel; C. A. Meetre; C. Perche; L. Sitruk; S. Hoang

1995-01-01

66

Experimental observations of the spatial structure of wave-like disturbances generated in midlatitude ionosphere by high power radio waves  

NASA Astrophysics Data System (ADS)

We present the results of the experiments carried out in 2009-2012 on the Sura heating facility (Radio Physical Research Institute, N. Novgorod, Russia) on modification of the midlatitude ionosphere by powerful HF radiowaves. The experiments were conducted using O-mode radiowaves at frequencies lower than critical frequency of the ionospheric F2 layer both in daytime and nighttime ionosphere. Various schemes of the radiation of the heating wave were used including square wave modulation of the effective radiated power (ERP) at various frequencies and power stepping. Radio transmissions of the low- (Parus/Tsikada) and high-orbital (GPS/GLONASS) navigational satellites received at the mobile network of receiving sites were used for the remote sensing of the heated area of the ionosphere. The variations in the slant total electron content (TEC), which are proportional to the reduced phase of navigational signals, were studied for the satellite passes for which ionospheric penetration points crossed the disturbed area during HF heating. The variations in TEC caused by HF heating are identified in a number of examples. It is shown that the GNSS TEC spectra contain frequency components corresponding to the modulation periods of the ERP of the heating wave. The manifestations of the heating-induced variations in TEC are most prominent in the area of magnetic zenith of the pumping wave. Different behavior of TEC variations was observed during nighttime and daytime heating experiments. In daytime conditions the pump wave switched ON causes the increase of TEC while in the nighttime it causes a decrease in TEC. This can be explained by the different contribution of the processes responsible for the increase and decrease of TEC in daytime in nighttime conditions. In this work we also present the first time radiotomographic reconstructions of the spatial structure of the wave-like disturbances, generated in the ionosphere by high-power radio waves radiated by the Sura heater with a square wave modulation of the ERP at a frequency lower than or of the order of the Brunt-Vaisala frequency of the neutral atmosphere. The observed wavelike structures, which are possibly AGWs, diverge from the heated area of the ionosphere (observed like a narrow trough with dimensions corresponding to the diagram pattern of the Sura heater), the spatial period of these disturbances is 200-250 km and they are easily traced up to a distance of 700-800 km from the heated region. These observations are in good agreement with complimentary GPS/GLONASS data. We also present the examples of amplitude scintillations of the signals of low-orbital radio beacons corresponding to small-scale field-aligned irregularities in the heated area of ionosphere. The possibility of generation of electromagnetic waves by moving wave-like structures in ionosphere (like AGWs induced by HF-heating observed in our experiments) is also addressed in this work. The authors are grateful to the staff of the Sura facility for their help in conducting the experiments and acknowledge the support of the Russian Foundation for Basic Research (grants 10-05-01126, 11-02-00374, 11-05-01157, 12-02-31839, 12-05-33065, 12-05-10068), grant of the President of Russian Federation MK-2544.2012.5 and Lomonosov Moscow State University Program of Development.

Kunitsyn, V.; Andreeva, E.; Padokhin, A. M.; Nazarenko, M.; Frolov, V.; Komrakov, G.; Bolotin, I.

2012-12-01

67

Impact of tropospheric scintillation in the Ku\\/K bands on the communications between two LEO satellites in a radio occultation geometry  

Microsoft Academic Search

A theoretical analysis of the impact of clear-air tropospheric scintillation on a radio occultation link between two low Earth orbit satellites in K- and Ku-bands is presented, with particular reference to differential approaches for the measure of the total content of water vapor. The troposphere is described as a spherically symmetric turbulent medium satisfying Kolmogorov theory. Rytov's first iteration solution

Enrica Martini; Angelo Freni; Luca Facheris; Fabrizio Cuccoli

2006-01-01

68

Remote personal health monitoring with radio waves  

NASA Astrophysics Data System (ADS)

We present several techniques utilizing radio-frequency identification (RFID) technology for personal health monitoring. One technique involves using RFID sensors external to the human body, while another technique uses both internal and external RFID sensors. Simultaneous monitoring of many patients in a hospital setting can also be done using networks of RFID sensors. All the monitoring are done wirelessly, either continuously or periodically in any interval, in which the sensors collect information on human parts such as the lungs or heart and transmit this information to a router, PC or PDA device connected to the internet, from which patient's condition can be diagnosed and viewed by authorized medical professionals in remote locations. Instantaneous information allows medical professionals to intervene properly and timely to prevent possible catastrophic effects to patients. The continuously monitored information provides medical professionals more complete and long-term studies of patients. All of these result in not only enhancement of the health treatment quality but also significant reduction of medical expenditure. These techniques demonstrate that health monitoring of patients can be done wirelessly at any time and any place without interfering with the patients' normal activities. Implementing the RFID technology would not only help reduce the enormous and significantly growing medical costs in the U.S.A., but also help improve the health treatment capability as well as enhance the understanding of long-term personal health and illness.

Nguyen, Andrew

2008-03-01

69

PhET Simulation: Radio Waves & Electromagnetic Fields  

NSDL National Science Digital Library

Students gain understanding of electromagnetic radiation as they broadcast radio waves from a transmitter to receiver. They can manually control the transmitter electron or set automatic oscillation. The field can be displayed as a curve or vectors, with students controlling the frequency and amplitude. This item is part of a larger collection of simulations developed by the Physics Education Technology project (PhET). The simulations are animated, interactive, and game-like environments.

2006-10-06

70

Theories of radio emissions and plasma waves. [in Jupiter magnetosphere  

NASA Technical Reports Server (NTRS)

The complex region of Jupiter's radio emissions at decameter wavelengths, the so-called DAM, is considered, taking into account the basic theoretical ideas which underly both the older and newer theories and models. Linear theories are examined, giving attention to direct emission mechanisms, parallel propagation, perpendicular propagation, and indirect emission mechanisms. An investigation of nonlinear theories is also conducted. Three-wave interactions are discussed along with decay instabilities, and three-wave up-conversio. Aspects of the Io and plasma torus interaction are studied, and a mechanism by which Io can accelerate electrons is reviewed.

Goldstein, M. L.; Goertz, C. K.

1983-01-01

71

Upper limits on gravitational wave emission from 78 radio pulsars  

Microsoft Academic Search

We present upper limits on the gravitational wave\\u000a\\u0009\\u0009 emission from 78 radio pulsars based on data from the third\\u000a\\u0009\\u0009 and fourth science runs of the {LIGO} and GEO 600\\u000a\\u0009\\u0009 gravitational wave detectors. The data from both runs have\\u000a\\u0009\\u0009 been combined coherently to maximize sensitivity. For the\\u000a\\u0009\\u0009 first time, pulsars within binary (or multiple) systems\\u000a\\u0009\\u0009 have been included in the search

B. Abbott; R. Abbott; R. Adhikari; J. Agresti; P. Ajith; B. Allen; R. Amin; S. B. Anderson; W. G. Anderson; M. Arain; M. Araya; H. Armandula; M. Ashley; S. Aston; P. Aufmuth; C. Aulbert; S. Babak; S. Ballmer; H. Bantilan; B. C. Barish; C. Barker; D. Barker; B. Barr; P. Barriga; M. A. Barton; K. Bayer; K. Belczynski; J. Betzwieser; P. T. Beyersdorf; B. Bhawal; I. A. Bilenko; G. Billingsley; R. Biswas; E. Black; K. Blackburn; L. Blackburn; D. Blair; B. Bland; J. Bogenstahl; L. Bogue; R. Bork; V. B. Braginsky; S. Bose; P. R. Brady; J. E. Brau; M. Brinkmann; A. Bunkowski; D. A. Brown; A. Bullington; A. Buonanno; O. Burmeister; D. Busby; W. E. Butler; R. L. Byer; L. Cadonati; G. Cagnoli; J. B. Camp; J. Cannizzo; K. Cannon; C. A. Cantley; J. Cao; L. Cardenas; K. Carter; M. M. Casey; G. Castaldi; C. Cepeda; E. Chalkey; P. Charlton; S. Chatterji; S. Chelkowski; Y. Chen; F. Chiadini; D. Chin; E. Chin; J. Chow; N. Christensen; J. Clark; P. Cochrane; T. Cokelaer; C. N. Colacino; R. Coldwell; R. Conte; D. Cook; T. Corbitt; D. Coward; D. Coyne; J. D. E. Creighton; T. D. Creighton; R. P. Croce; D. R. M. Crooks; A. M. Cruise; A. Cumming; J. Dalrymple; E. D'Ambrosio; K. Danzmann; G. Davies; D. Debra; J. Degallaix; M. Degree; T. Demma; V. Dergachev; S. Desai; R. Desalvo; S. Dhurandhar; M. Díaz; J. Dickson; A. Di Credico; G. Diederichs; A. Dietz; E. E. Doomes; R. W. P. Drever; J.-C. Dumas; R. J. Dupuis; J. G. Dwyer; P. Ehrens; E. Espinoza; T. Etzel; M. Evans; T. Evans; S. Fairhurst; Y. Fan; D. Fazi; M. M. Fejer; Lee Samuel Finn; V. Fiumara; N. Fotopoulos; A. Franzen; K. Y. Franzen; A. Freise; R. Frey; T. Fricke; P. Fritschel; V. V. Frolov; M. Fyffe; V. Galdi; K. S. Ganezer; J. Garofoli; I. Gholami; J. A. Giaime; S. Giampanis; K. D. Giardina; K. Goda; E. Goetz; L. Goggin; G. González; S. Gossler; A. Grant; S. Grunewald; C. Gray; M. Gray; J. Greenhalgh; A. M. Gretarsson; R. Grosso; H. Grote; M. Guenther; R. Gustafson; B. Hage; D. Hammer; C. Hanna; J. Hanson; J. Harms; G. Harry; E. Harstad; T. Hayler; J. Heefner; I. S. Heng; A. Heptonstall; M. Heurs; M. Hewitson; S. H. Huttner; E. Hirose; D. Hoak; D. Hosken; J. Hough; E. Howell; D. Hoyland; D. Ingram; E. Innerhofer; M. Ito; Y. Itoh; A. Ivanov; D. Jackrel; B. Johnson; W. W. Johnson; D. I. Jones; G. Jones; R. Jones; L. Ju; P. Kalmus; V. Kalogera; D. Kasprzyk; E. Katsavounidis; K. Kawabe; S. Kawamura; F. Kawazoe; W. Kells; D. G. Keppel; F. Ya. Khalili; C. Kim; P. King; J. S. Kissel; S. Klimenko; K. Kokeyama; V. Kondrashov; R. K. Kopparapu; D. Kozak; B. Krishnan; P. Kwee; P. K. Lam; M. Landry; B. Lantz; A. Lazzarini; B. Lee; M. Lei; J. Leiner; V. Leonhardt; I. Leonor; K. Libbrecht; P. Lindquist; N. A. Lockerbie; M. Longo; M. Lormand; M. Lubinski; H. Lück; B. Machenschalk; M. Macinnis; M. Mageswaran; K. Mailand; M. Malec; V. Mandic; S. Marano; S. Márka; J. Markowitz; E. Maros; I. Martin; J. N. Marx; K. Mason; L. Matone; V. Matta; N. Mavalvala; R. McCarthy; D. E. McClelland; S. C. McGuire; M. McHugh; K. McKenzie; J. W. C. McNabb; S. McWilliams; T. Meier; A. Melissinos; G. Mendell; R. A. Mercer; S. Meshkov; E. Messaritaki; C. J. Messenger; D. Meyers; E. Mikhailov; S. Mitra; V. P. Mitrofanov; G. Mitselmakher; R. Mittleman; O. Miyakawa; S. Mohanty; G. Moreno; K. Mossavi; C. Mowlowry; A. Moylan; D. Mudge; G. Mueller; S. Mukherjee; H. Müller-Ebhardt; J. Munch; P. Murray; E. Myers; J. Myers; T. Nash; G. Newton; A. Nishizawa; F. Nocera; K. Numata; B. O’Reilly; R. O’Shaughnessy; D. J. Ottaway; H. Overmier; B. J. Owen; Y. Pan; M. A. Papa; V. Parameshwaraiah; C. Parameswariah; P. Patel; M. Pedraza; S. Penn; V. Pierro; I. M. Pinto; M. Pitkin; H. Pletsch; M. V. Plissi; F. Postiglione; R. Prix; V. Quetschke; F. Raab; D. Rabeling; H. Radkins; R. Rahkola; N. Rainer; M. Rakhmanov; K. Rawlins; S. Ray-Majumder; V. Re; T. Regimbau; H. Rehbein; S. Reid; D. H. Reitze; L. Ribichini; R. Riesen; K. Riles; B. Rivera; N. A. Robertson; C. Robinson; E. L. Robinson; S. Roddy; A. Rodriguez; A. M. Rogan; S. Rowan; J. Rollins; J. D. Romano; J. Romie; R. Route; A. Ruediger; L. Ruet; P. Russell; K. Ryan; S. Sakata; M. Samidi; L. Sancho de la Jordana; V. Sandberg; G. H. Sanders; V. Sannibale; S. Saraf; P. Sarin; B. S. Sathyaprakash; S. Sato; P. R. Saulson; R. Savage; P. Schwinberg; A. Sazonov; S. Schediwy; R. Schilling; R. Schnabel; R. Schofield; B. F. Schutz; S. M. Scott; A. C. Searle; B. Sears; F. Seifert; D. Sellers; A. S. Sengupta; P. Shawhan; D. H. Shoemaker; A. Sibley; J. A. Sidles; X. Siemens; D. Sigg; S. Sinha; A. M. Sintes; B. J. J. Slagmolen; J. Slutsky; J. R. Smith; M. R. Smith; K. Somiya; K. A. Strain; D. M. Strom; A. Stuver; T. Z. Summerscales; K.-X. Sun; M. Sung; P. J. Sutton; H. Takahashi; D. B. Tanner; M. Tarallo; R. Taylor; J. Thacker; K. A. Thorne; K. S. Thorne; A. Thuering; V. Tokmakov; C. Torres; C. Torrie; G. Traylor; M. Trias; W. Tyler; D. Ugolini; C. Ungarelli

2007-01-01

72

Radio observations of atmospheric gravity waves with Callisto  

NASA Astrophysics Data System (ADS)

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.

Monstein, C.

2013-12-01

73

S/WAVES: The Radio and Plasma Wave Investigation on the STEREO Mission  

NASA Astrophysics Data System (ADS)

This paper introduces and describes the radio and plasma wave investigation on the STEREO Mission: STEREO/WAVES or S/WAVES. The S/WAVES instrument includes a suite of state-of-the-art experiments that provide comprehensive measurements of the three components of the fluctuating electric field from a fraction of a hertz up to 16 MHz, plus a single frequency channel near 30 MHz. The instrument has a direction finding or goniopolarimetry capability to perform 3D localization and tracking of radio emissions associated with streams of energetic electrons and shock waves associated with Coronal Mass Ejections (CMEs). The scientific objectives include: (i) remote observation and measurement of radio waves excited by energetic particles throughout the 3D heliosphere that are associated with the CMEs and with solar flare phenomena, and (ii) in-situ measurement of the properties of CMEs and interplanetary shocks, such as their electron density and temperature and the associated plasma waves near 1 Astronomical Unit (AU). Two companion papers provide details on specific aspects of the S/WAVES instrument, namely the electric antenna system (Bale et al., Space Sci. Rev., 2007) and the direction finding technique (Cecconi et al., Space Sci. Rev., 2007).

Bougeret, J. L.; Goetz, K.; Kaiser, M. L.; Bale, S. D.; Kellogg, P. J.; Maksimovic, M.; Monge, N.; Monson, S. J.; Astier, P. L.; Davy, S.; Dekkali, M.; Hinze, J. J.; Manning, R. E.; Aguilar-Rodriguez, E.; Bonnin, X.; Briand, C.; Cairns, I. H.; Cattell, C. A.; Cecconi, B.; Eastwood, J.; Ergun, R. E.; Fainberg, J.; Hoang, S.; Huttunen, K. E. J.; Krucker, S.; Lecacheux, A.; MacDowall, R. J.; Macher, W.; Mangeney, A.; Meetre, C. A.; Moussas, X.; Nguyen, Q. N.; Oswald, T. H.; Pulupa, M.; Reiner, M. J.; Robinson, P. A.; Rucker, H.; Salem, C.; Santolik, O.; Silvis, J. M.; Ullrich, R.; Zarka, P.; Zouganelis, I.

2008-04-01

74

Ulysses Radio and Plasma Wave Observations at High Southern Heliographic Latitudes  

E-print Network

Ulysses Radio and Plasma Wave Observations at High Southern Heliographic Latitudes R. G. Stone, R-Frey, R. Manning, M. J. Reiner, J. L. Steinberg, G. Thejappa Ulysses spacecraft radio and plasma wave Investigation (URAP) on Ulysses, provide remote diagnostics of solar and planetary radio emissions

California at Berkeley, University of

75

Ionospheric modification by high-power radio waves  

SciTech Connect

Powerful, high-frequency radio waves have been used to temporarily modify the ionosphere. Thermal and parametric interactions have led to a diverse range of observed phenomena, including generation of density striations and artificial spread-F, enhancements of electron plasma waves, production of extrathermal electron fluxes and enhanced airglow, modification of the D-region temperature and densities, wideband signal attenuation, and self-focusing and scattering of the electromagnetic waves. The physics of ionospheric modification by high-power radio waves is reviewed in the context of our current theoretical understanding; disturbance generation mechanisms are qualitatively described. In addition, results of recent experiments are summarized in which ionospheric irregularities are generated and their evolution and decay processes investigated in detail. The effects and potential controlled applications of these HF ionospheric modifications for various RF systems studies are discussed. The C/sup 3/I scientific community provides an important motivation for these ionospheric modification studies; their increased interaction and active participation in experimental design and interpretation are encouraged.

Duncan, L.M.

1981-04-01

76

Ion species mix and ion density measurements using radio frequency waves  

Microsoft Academic Search

Radio frequency wave applications have demonstrated great versatility in tokamak plasmas. Two applications, using the same diagnostic design, can make use of a fast Alfven wave to make ion species mix and ion density measurements. A discussion and derivation, using the cold plasma approximation, is given for a fast Alfven radio wave used for making an interferometry density measurement, a

George Wilder Watson III

2003-01-01

77

The Physical Reality of Space and Surface Waves in the Radiation Field of Radio Antennas  

Microsoft Academic Search

Evidence is presented which indicates that, notwithstanding the change in sign made by Sommerfeld in his 1926 paper on radio wave propagation, the radiation field of a vertical electric dipole may be separated into space and surface wave components. Sommerfeld's original concepts as to the characteristics of two such waves in radio transmission are largely substantiated. It is shown that

K. A. Norton

1937-01-01

78

Irradiance scintillation for Gaussian-beam wave propagating through weak non-Kolmogorov turbulence.  

PubMed

Kolmogorov turbulence theory based models cannot be directly applied in non-Kolmogorov turbulence case, which has been reported recently by increasing experimental evidence and theoretical investigation. In this study, based on the generalized von Karman spectral model, the theoretical expression of the irradiance scintillation index is derived for Gaussian-beam wave propagating through weak non-Kolmogorov turbulence with horizontal path. In the derivation, the expression is divided into two parts for physical analysis purpose and mathematical analysis convenience. This expression considers the influences of finite turbulence inner and outer scales and has a general spectral power law value in the range 3 to 4 instead of standard power law value of 11/3 (for Kolmogorov turbulence). Numerical simulations are conducted to investigate the influences. PMID:21935048

Cui, Linyan; Xue, Bindang; Cao, Lei; Zheng, Shiling; Xue, Wenfang; Bai, Xiangzhi; Cao, Xiaoguang; Zhou, Fugen

2011-08-29

79

Radio Wave Path in the Ionosphere Adaptive Ray Tracing Model  

NASA Astrophysics Data System (ADS)

The process of determining the radio wave path in the ionosphere is called ray tracing. Because of the irregularities in the ionosphere the ray paths of HF waves, which are strongly affected by the ionosphere, are calculated for different elevation angles and different frequencies of the radio wave. In HF communication forecasting it is often convenient to use simplified ionosphere models (like CHIU and IRI model) to determine the geographical distribution of ionosphere contents, so the relationship between the electron density and the ionosphere refractive index could be determined. It was seen that for a fixed elevation angle the apogee height decreases as the transmitted frequency became lower. For a different elevation angle values (20, 30 and 40 degree) and transmitted frequency varying from 4 to 18 MHz, there is no difference between the curves which is drown between the altitude (0 to 250 km) and the ground range (0 to 3500 km) because the refraction in all cases occurred in F region only.

Al-Ubaidi, Najat

80

Cassini Radio and Plasma Wave Observations at Saturn  

NASA Technical Reports Server (NTRS)

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.

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

81

General Theory on the Propagation of Radio Waves in the Ionized Layer of the Upper Atmosphere  

Microsoft Academic Search

1. Theories on the propagation of radio waves in the entire range of frequencies used in communications are treated together with discussions on the applicable limit of the theory of geometrical optics to wave propagation. 2. Definitions of the \\

S. Namba

1933-01-01

82

Radio Wave Propagation Handbook for Communication on and Around Mars  

NASA Technical Reports Server (NTRS)

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.

Ho, Christian; Golshan, Nasser; Kliore, Arvydas

2002-01-01

83

Comparison of LaBr 3:Ce and NAI(Tl) scintillators for radio-isotope identification devices  

NASA Astrophysics Data System (ADS)

Lanthanum bromide (LaBr 3:Ce) scintillators offer significantly better resolution (<3 percent at 662 keV) relative to sodium iodide (NaI(Tl)) but contain internal radioactivity that contributes to spectral counts. LaBr 3:Ce has recently become available commercially in sizes large enough for the hand-held radio-isotope identification device (RIID) market. To study its potential for RIIDs, a series of measurements were performed comparing a 1.5×1.5-in. LaBr 3:Ce detector with an Exploranium GR-135 RIID, which contains a 1.5×2.2-in. NaI(Tl) detector. Measurements were taken for short time frames and included examples of naturally occurring radioactive material (NORM), typically found in cargo, and special nuclear materials. To facilitate direct comparison, spectra from the different detectors were analyzed with the same isotope identification software (ORTEC ScintiVision™). In general, the LaBr 3:Ce detector was able to find more peaks and find them faster than the NaI(Tl) detector. To the same level of significance, the LaBr 3:Ce detector was usually two to three times faster. The notable exception was for 40K-containing NORM where interfering internal activity due to 138La in the LaBr 3:Ce detector exists and NaI(Tl) consistently outperformed LaBr 3:Ce.

Milbrath, B. D.; Choate, B. J.; Fast, J. E.; Hensley, W. K.; Kouzes, R. T.; Schweppe, J. E.

2007-03-01

84

The Speed of Radio Waves and Its Importance in Some Applications  

Microsoft Academic Search

This paper comprises a review of the present state of knowledge of the speed of transmission of radio waves under the practical conditions of certain applications in which such knowledge is important. It is shown first that, for radio waves in a vacuum, their speed of transmission is equal to the velocity of light (299,775 km\\/s), to within the limits

R. L. Smith-Rose

1950-01-01

85

Z mode waves as the source of Saturn narrowband radio emissions  

E-print Network

Z mode waves as the source of Saturn narrowband radio emissions ShengYi Ye,1 J. D. Menietti,1 G present the first magnetic field measurements of Saturn narrowband emissions validating. S. Kurth (2010), Z mode waves as the source of Saturn narrowband radio emissions, J. Geophys. Res

Gurnett, Donald A.

86

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

ERIC Educational Resources Information Center

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…

Dombi, Andra; Tunyagi, Arthur; Neda, Zoltan

2013-01-01

87

Radio Wave Scattering in the Outer Heliosphere: Preliminary Calculations  

NASA Technical Reports Server (NTRS)

Detailed first estimates are presented of angular broadening in the outer heliosphere due to scattering of radio waves by density irregularities. The application is to the 2-3 kHz radiation observed by Voyager. Two plausible turbulence models, which account very well for scattering within 1 AU, are extrapolated beyond 10 AU. Both models predict significant angular broadening in the outer heliosphere, accounting semi- quantitatively alone for the source sizes inferred from roll modulation data. Predictions are presented for radial variations in the apparent source size if scattering is important. Comparisons with available data argue that scattering is important (and indeed is the dominant contributor to the apparent source size) and that the radiation source is located in the outer heliosphere. Other evidence that scattering is important, such as the fluctuations in apparent source direction and intensity, are also identified. The effects of scattering should be included in future analyses of the 2-3 kHz emissions.

Cairns, Iver H.

1995-01-01

88

Scintillating plate calorimeter mechanical design  

Microsoft Academic Search

Progress on designs for compensating scintillator plate calorimeters will be presented. One design includes a lead composite absorber, fiber readout, and radiation hardened scintillator plates, and the second design has depleted uranium absorbers, wave length shifter plate readout, and scintillator plates. The lead absorber is cast with slots to accept the scintillator in the first design, while the depleted uranium

A. Buehring; N. Hill; T. Kirk; J. Nasiatka; E. Petereit; L. Price; J. Proudfoot; H. Spinka; D. Underwood; M. Burke; D. Hackworth; T. Hordubay; D. Marshik; D. Scherbarth; R. Swensrud

1990-01-01

89

Jupiter's low-frequency radio spectrum from Cassini\\/Radio and Plasma Wave Science (RPWS) absolute flux density measurements  

Microsoft Academic Search

We apply the calibration method developed by Dulk et al. [2001] to the data from the Cassini\\/Radio and Plasma Wave Science (RPWS) High-Frequency Receiver in order to derive flux density measurements of six components of the Jovian low-frequency radio spectrum over the full frequency range of the instrument (3.5 kHz to 16.1 MHz). The estimated accuracy is better than 50%,

P. Zarka; B. Cecconi; W. S. Kurth

2004-01-01

90

MULTIFREQUENCY RECORDINGS OF RADIO-WAVE POLAR IZATION NEAR THE GEOMAGNETIC EQUATOR  

Microsoft Academic Search

Theory of radio-wave propagation predicts that in the special case of propagation of a wave in the ionosphere with its wave-normal perpendicular to the Earth's magnetic field at all points along the wave-path, the two wave-components returned should be plane-polarized in mutually perpendicular planes. The Huancayo Magnetic Observatory (Peru) of the Department of Terrestrial Magnetism of the Carnegie Institution of

H. W. WELLS

91

Scattering of Radio Frequency Waves by Edge Density Blobs in Tokamak Plasmas  

SciTech Connect

The density blobs and fluctuations present in the edge region of magnetic fusion devices can scatter radio frequency (RF) waves through refraction and diffraction. The scattering can diffuse the rays in space and in wave-vector space. The diffusion in space can make the rays miss their intended target region, while the diffusion in wave-vector space can broaden the wave spectrum and modify the wave damping and current profile.

Ram, A. K. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Hizanidis, K.; Kominis, Y. [National Technical University of Athens, Association EURATOM-Hellenic Republic, Zografou, Athens 15773 (Greece)

2011-12-23

92

The theory of the guiding of radio waves in the upper ionosphere  

Microsoft Academic Search

In a horizontally stratified magneto-ionic medium in which the electron density varies monotonically with height, tracks exist in which radio waves may be guided to great distances. This kind of propagation is studied using wave-guide mode theory. When one of the component waves in a guided signal gives rise to another by reflection, the phase is sometimes advanced and sometimes

A. D. M. Walker

1966-01-01

93

Observations of atmospheric gravity waves by radio interferometry: are results biased by the observational technique?  

E-print Network

Observations of atmospheric gravity waves by radio interferometry: are results biased present a quantitative comparison between a large data base of medium-scale atmospheric gravity waves predictions. 1 Introduction Atmospheric gravity waves (AGWs) are a neutral-air phenomenon, but most techniques

Boyer, Edmond

94

Characteristics of coronal shock waves and solar type 2 radio bursts  

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

95

Characteristics of coronal shock waves and solar type 2 radio bursts  

NASA Astrophysics Data System (ADS)

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.

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

1995-06-01

96

GPS phase scintillation correlated with auroral forms  

NASA Astrophysics Data System (ADS)

The disruption of radio wave propagation due to rapid changes in electron density caused by auroral precipitation has been observed for several decades. In a few cases the disruption of GPS signals has been attributed to distinct auroral arcs [Kintner, 2007; Garner, 2011], but surprisingly there has been no systematic study of the characteristics of the auroral forms that cause GPS scintillation. In the Fall of 2012 ASTRA deployed four CASES GPS receivers at UAF observatories in Alaska (Kaktovik, Fort Yukon, Poker Flat and Gakona) specifically to address the effects of auroral activity on the high latitude ionosphere. We have initiated an analysis that compares the phase scintillation, recorded at high cadence, with filtered digital all-sky camera data to determine the auroral morphology and electron precipitation parameters that cause scintillation. From correlation studies from a single site (Poker Flat), we find that scintillation is well correlated with discrete arcs that have high particle energy flux (power per unit area), and not as well correlated with pulsating forms which typically have high characteristic energy, but lower energy flux . This indicates that the scintillation is correlated with the magnitude of the change in total electron density as expected. We will also report on ongoing work where we correlate the scintillation from the Fort Yukon receiver with the all-sky images at Poker Flat to determine the altitude that produces the greatest disturbance. These studies are aimed at a model that can predict the expected local disturbance to navigation due to auroral activity.

Hampton, D. L.; Azeem, S. I.; Crowley, G.; Santana, J.; Reynolds, A.

2013-12-01

97

Put a Short-Wave Radio in Your Foreign Language Classroom  

ERIC Educational Resources Information Center

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)

Oksenholt, Svein

1977-01-01

98

Some Measurements of High-Latitude Ionospheric Absorption Using Extraterrestrial Radio Waves  

Microsoft Academic Search

This paper describes the manner im which 30-mc extraterrestrial radio waves have been used to study the radio absorption characteristics of the arctic ionosphere. It opens with a brief discussion of the theory of ionospheric absorption, followed by a description of the basic principles involved in the technique. Two different types of equipment which have been used in these absorption

C. G. Little; H. Leinbach

1958-01-01

99

Characterizations of supercontinuum light source for WDM millimeter-wave-band radio-on-fiber systems  

Microsoft Academic Search

We qualitatively evaluate for the first time phase-noise characteristics of radio-frequency carriers of a supercontinuum generator and prove to be promising as the multiwavelength light source for wavelength-division-multiplexed millimeter-wave-band radio-on-fiber systems.

Toshiaki Kuri; Teppei Nakasyotani; Hiroyuki Toda; Ken-Ichi Kitayama

2005-01-01

100

A high-temperature superconducting receiver for low-frequency radio waves  

Microsoft Academic Search

We have developed a receiver for low-frequency radio waves using high-temperature superconducting quantum interference devices (SQUIDs). The primary application of such a receiver is to communicate in underground areas where the overburden results in significant losses at the usual radio frequencies. The receiver constructed consists of a SQUID, a small dewar, control electronics, and a battery pack. The SQUID was

D. Reagor; Yan Fan; C. Mombourquette; Quanxi Jia; L. Stolarczyk

1997-01-01

101

Multi-spacecraft Observations of type III radio bursts and their associated Langmuir waves  

Microsoft Academic Search

The radio signatures of flare accelerated electron beams in the corona and interplanetary medium are the fast drifting emission features called type III radio bursts. The production of these bursts involves the generation of high levels of Langmuir waves excited by the flare accelerated electron beams propagating along open field lines, and their subsequent conver-sion into electromagnetic radiation at the

Thejappa Golla; Robert MacDowall

2010-01-01

102

Efficient Computation of Prolate Spheroidal Wave Functions in Radio Astronomical Source Modeling  

Microsoft Academic Search

The application of orthonormal basis functions such as Prolate Spheroidal Wave Functions (PSWF) for accurate source modeling in radio astronomy has been comprehensively studied. They are of great importance for high fidelity, high dynamic range imaging with new radio telescopes as well as conventional ones. But the construction of PSWF is computationally expensive compared to other closed form basis functions.

Parisa Noorishad; Sarod Yatawatta

2011-01-01

103

Reflection and transmission coefficients for radio waves incident obliquely on N identical plane plasma layers and zebra patterns in the spectrum of solar radio emission  

NASA Astrophysics Data System (ADS)

The reflection and transmission coefficients for quasi-monochromatic radio waves incident at an arbitrary angle on an arbitrary number of identical piecewise-homogeneous plane plasma layers are calculated analytically and numerically. It is shown that alternating transparency and opacity stripes in the spectrum of radio waves passing through such a plasma structure (the zebra pattern effect) can be observed at any angle of incidence. The opacity stripes for ordinary waves are wider than those for extraordinary waves. For the zebra pattern to be well pronounced, the radio wave flux in the Sun's atmosphere should be narrowly directed, which is possible during bursts.

Laptukhov, A. I.; Chernov, G. P.

2012-07-01

104

Comparison of LaBr3:Ce and NaI(Tl) Scintillators for Radio-Isotope Identification Devices  

SciTech Connect

Lanthanum halide (LaBr3:Ce) scintillators offer significantly better resolution (<3 percent at 662 kilo-electron volt [keV]) relative to sodium iodide (NaI(Tl)) and have recently become commercially available in sizes large enough for the hand-held radio-isotope identification device (RIID) market. There are drawbacks to lanthanum halide detectors, however. These include internal radioactivity that contributes to spectral counts and a low-energy response that can cause detector resolution to be lower than that of NaI(Tl) below 100 keV. To study the potential of this new material for RIIDs, we performed a series of measurements comparing a 1.5?1.5 inch LaBr?3:Ce detector with an Exploranium GR 135 RIID, which contains a 1.5-2.2 inch NaI(Tl) detector. Measurements were taken for short time frames, as typifies RIID usage. Measurements included examples of naturally occurring radioactive material (NORM), typically found in cargo, and special nuclear materials. Some measurements were noncontact, involving short distances or cargo shielding scenarios. To facilitate direct comparison, spectra from the different detectors were analyzed with the same isotope identification software (ORTEC ScintiVision TM). In general, the LaBr3:Ce detector was able to find more peaks and find them faster than the NaI(Tl) detector. To the same level of significance, the LaBr3:Ce detector was usually two to three times faster. The notable exception was for 40K containing NORM where interfering internal contamination in the LaBr3:Ce detector exist. NaI(Tl) consistently outperformed LaBr3:Ce for this important isotope. LaBr3:Ce currently costs much more than NaI(Tl), though this cost-difference is expected to diminish (but not completely) with time. As is true of all detectors, LaBr3:Ce will need to be gain-stabilized for RIID applications. This could possibly be done using the internal contaminants themselves. It is the experience of the authors that peak finding software in RIIDs needs to be improved, regardless of the detector material.

Milbrath, Brian D.; Choate, Bethany J.; Fast, Jim E.; Hensley, Walter K.; Kouzes, Richard T.; Schweppe, John E.

2006-07-31

105

38 GHz wideband point-to-multipoint radio wave propagation study for a campus environment  

Microsoft Academic Search

This article presents the results of a fixed millimeter-wave short-hop radio wave propagation study at 38 GHz. A wideband measurement campaign was performed using three cross-campus radio links from April to August 1998 at Virginia Tech. 73,963 power delay profiles (PDPs) were recorded during different weather events such as clear sky, rain, and hail. Rain\\/hail attenuation, short-term signal variation, and

Hao Xut; T. S. Rappaport; R. J. Boyle; J. H. Schaffner

1999-01-01

106

Millimeter radio wave scattering on laser-induced discharges in a dusty atmosphere  

NASA Astrophysics Data System (ADS)

The integral absorption of millimeter radio waves in atmospheric gases on the near-ground and oblique paths with a scatterer is compared. The scattering properties of millimeter-radio waves of the plasma nimbus of the laser-induced air discharge in atmospheric aerosol are studied experimentally. It is shown that laser-induced breakdown can be used as a repeater for mm-band communication lines up to 40 km.

Kisliakov, A. G.; Kanakov, V. A.; Sorokin, Iu. M.; Finkel'Shtein, S. E.

1992-01-01

107

Radio-wave attenuation and sulfuric-acid vapor content in the Venus atmosphere  

NASA Astrophysics Data System (ADS)

Radio-wave absorption in the Venus atmosphere is investigated using radio probing data on variations of the field strengths of 5-cm and 32-cm signals. It is shown that the most probable cause of cm-wave attenuation at altitudes below 50 km is absorption by sulfuric-acid vapor. Sulfuric-acid vapor contents equal to 15 ppm at 48 km and 19 ppm at 47 km were determined, which agree well with Pioneer-Venus measurements at 13 cm.

Gubenko, V. N.; Iakovlev, O. I.; Matiugov, S. S.; Kucheriavenkov, A. I.; Vaganov, I. R.

1989-11-01

108

Wave optics simulation of Gaussian Schell-model vortex beam propagation in turbulence: intensity and scintillation analysis  

NASA Astrophysics Data System (ADS)

The propagation of partially coherent vortex beams through atmospheric turbulence in weak-to-strong fluctuation regimes is investigated. Irradiance profiles from wave optics simulations and analytical theory compare favorably for a variety of link parameters. Simulation results indicate that partially coherent vortex beams can reduce scintillation index values relative to comparable classic Gaussian Schell model beams when turbulence conditions are mediate to strong. However, the overall propagation performance of partially coherent vortex beams, as measured by the metric ?, tends to be poorer than classic Gaussian Schell model beams because of larger inherent beam spread.

Xiao, Xifeng; Voelz, David

2010-02-01

109

Energetic electrons and plasma waves associated with a solar type III radio burst  

NASA Technical Reports Server (NTRS)

Detailed in situ observations from the ISEE 3 spacecraft of energetic electrons, plasma waves, and radio emission for the type II solar radio burst of February 17, 1979, are presented. The reduced, one-dimensional electron distribution function is constructed as a function of time. Since the faster electrons arrive before the slower ones, a bump on tail distribution forms which is unstable to the growth of Langmuir waves. The plasma wave growth computed from the distribution function agrees well with the observed onset of the Langmuir waves, and there is qualitative agreement between variations in the plasma wave levels and in the development of regions of positive slope in the function. The evolution of the function, however, predicts far higher plasma wave levels than those observed. The maximum levels observed are approximately equal to the threshold for nonlinear wave processes, such as oscillation two-stream instability and soliton collapse.

Lin, R. P.; Potter, D. W.; Gurnett, D. A.; Scarf, F. L.

1981-01-01

110

Ulysses observations of wave activity at interplanetary shocks and implications for type II radio bursts  

SciTech Connect

We present the first quantitative investigation of interplanetary type II radio emission in which in situ waves measured at interplanetary shocks are used to compute radio wave intensities for comparison with type II observations. This study is based on in situ measurements of 42 in-ecliptic forward shocks as well as 10 intervals of type II emission observed by the Ulysses spacecraft between 1 AU and 5 AU. The analysis involves comparisons of statistical properties of type II bursts and in situ waves. Most of the 42 shocks are associated with the occurrence of electrostatic waves near the time of shock passage at Ulysses. These waves, which are identified as electron plasma waves and ion acoustic-like waves, are typically most intense several minutes before shock passage. This suggests that wave-wave interactions might be of importance in electromagnetic wave generation and that type II source regions are located immediately upstream of the shocks. We use the in situ wave measurements to compute type II brightness temperatures, assuming that emission at the fundamental of the electron plasma frequency is generated by the merging of electron plasma waves and ion acoustic waves or the decay of electron plasma waves into ion acoustic and transverse waves. Second harmonic emission is assumed to be produced by the merging of electron plasma waves. The latter mechanism requires that a portion of the electron plasma wave distribution is backscattered, presumably by density inhomogeneities in regions of observed ion acoustic wave activity. The computed type II brightness temperatures are found to be consistent with observed values for both fundamental and second harmonic emission, assuming that strong ({approx_equal}10{sup {minus}4}V/m) electron plasma waves and ion acoustic waves are coincident and that the electron plasma waves have phase velocities less than about 10 times the electron thermal velocity. (Abstract Truncated)

Lengyel-Frey, D. [Department of Astronomy, University of Maryland, College Park, Maryland (United States)] [Department of Astronomy, University of Maryland, College Park, Maryland (United States); [Computer Sciences Corporation, Suitland, Maryland (United States); Thejappa, G. [Department of Astronomy, University of Maryland, College Park, Maryland (United States)] [Department of Astronomy, University of Maryland, College Park, Maryland (United States); MacDowall, R.J.; Stone, R.G. [NASA Goddard Space Flight Center, Greenbelt, Maryland (United States)] [NASA Goddard Space Flight Center, Greenbelt, Maryland (United States); Phillips, J.L. [Los Alamos National Laboratory, Los Alamos, New Mexico (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico (United States); [NASA Johnson Space Flight Center, Houston, Texas (United States)

1997-02-01

111

The dispersion of radio waves in the solar corona  

Microsoft Academic Search

Different arrival times of the two magnetoionic modes in solar radio bursts have been detected. The bursts are from four decimetric radio events showing narrowband millisecond spikes. They have been observed with 2ms and 0.5ms time resolution, respectively, by the Ikarus and Phoenix spectrometers of ETH Zurich. The four events have been selected because of their low polarization. The arrival

A. O. Benz; P. Pianezzi

1997-01-01

112

Wave Normal and Poynting Vector Calculations using the Cassini Radio and Plasma Wave Instrument  

NASA Technical Reports Server (NTRS)

Wave normal and Poynting vector measurements from the Cassini radio and plasma wave instrument (RPWS) are used to examine the propagation characteristics of various plasma waves during the Earth flyby on August 18, 1999. Using the five-channel waveform receiver (WFR), the wave normal vector is determined using the Means method for a lightning-induced whistler, equatorial chorus, and a series of low-frequency emissions observed while Cassini was in the magnetosheath. The Poynting vector for these emissions is also calculated from the five components measured by the WFR. The propagation characteristics of the lightning-induced whistler were found to be consistent with the whistler wave mode of propagation, with propagation antiparallel to the magnetic field (southward) at Cassini. The sferic associated with this whistler was observed by both Cassini and the Stanford VLF group at the Palmer Station in Antarctica. Analysis of the arrival direction of the sferic at the Palmer Station suggests that the lightning stroke is in the same sector as Cassini. Chorus was observed very close (within a few degrees) to the magnetic equator during the flyby. The chorus was found to propagate primarily away from the magnetic equator and was observed to change direction as Cassini crossed the magnetic equator. This suggests that the source region of the chorus is very near the magnetic equator. The low-frequency emission in the magnetosheath has many of the characteristics of lion roars. The average value of the angle between the wave normal vector and the local magnetic field was found to be 16 degrees, and the emissions ranged in frequency from 0. 19 to 0.75 f(sub ce), where f(sub ce) is the electron cyclotron frequency. The wave normal vectors of these waves were primarily in one direction for each individual burst (either parallel or antiparallel to the local field) but varied in direction throughout the magnetosheath. This suggests that the sources of the emissions are far from the spacecraft and that there are multiple source regions.

Hospodarsky, G. B.; Averkamp, T. F.; Kurth, W. S.; Gurnett, D. A.; Dougherty, M.; Inan, Umran; Wood, Troy

2001-01-01

113

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

ERIC Educational Resources Information Center

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

Marine Corps, Washington, DC.

114

Modeling radio-wave scattering by a traveling spherical disturbance in the ionosphere  

Microsoft Academic Search

A numerical analysis is made of signal effects on short-wave paths more than 260 km long, due to radio scattering by a traveling spherical disturbance generated by a shock wave caused by an industrial surface explosion. It is shown that the Doppler frequency shift of the scattered signal takes a positive value and decreases montonically with time. Ray trajectories of

V. G. Spitsyn

1987-01-01

115

December 23, 2004 High Cadence Radio Observations of an EIT Wave  

E-print Network

site at the peak of the impulsive phase. The radio spectrum appears to be consistent with optically. We use the term "EIT wave" here for brevity. 1Astronomy Department, University of Maryland, College question is whether the wave is launched by the impulsive phase of the flare, or does it arise

White, Stephen

116

Polarization characteristics of VHF radio waves reflected by the E\\/sub s\\/-layer  

Microsoft Academic Search

Interference in VHF-TVs caused by the radio waves reflected from the ionosphere is a very serious problem in the area around Japan. The polarization rotation of the waves reflected by an Es-layer are clarified by the measurement of a VHF television signal. Two types of polarization rotation are observed. In one case, the more common of the two, the polarization

Masaru Ichinose; Syoji Kainuma

1996-01-01

117

Wave propagation and earth satellite radio emission studies  

NASA Technical Reports Server (NTRS)

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.

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

1974-01-01

118

Double layers and plasma-wave resistivity in extragalactic jets: Cavity formation and radio-wave emission  

NASA Technical Reports Server (NTRS)

For estimated values of the currents carried by extragalactic jets, current-driven electrostatic-wave- and electromagnetic-wave-produced resistivities do not occur. Strong plasma double layers, however, may exist within self-maintained density cavities, the relativistic double-layer-emitted electron, and ion beams driving plasma-wave resistivities in the low- and high-potential plasma adjacent to the double layers. The double-layer-emitted electron beams may also emit polarized radio waves via a collective bremsstrahlung process mediated by electrostatic two-stream instabilities.

Borovsky, Joseph E.

1987-01-01

119

Double layers and plasma-wave resistivity in extragalactic jets - Cavity formation and radio-wave emission  

NASA Technical Reports Server (NTRS)

Current driven electrostatic-wave- and electromagnetic-wave-produced resistivities do not occur in extragalactic jets for estimated values of the carried currents. Strong plasma double layers, however, may exist within self-maintained density cavities. The relativistic double-layer-emitted electron and ion beams drive plasma-wave resistivities in the low- and high-potential plasma adjacent to the double layers. The double-layer-emitted electron beams may also emit polarized radio waves via a collective bremsstrahlung process mediated by electrostatic two-stream instabilities.

Borovsky, Joseph E.

1987-01-01

120

Calculation of ionospheric plasma density irregularities parameters by using EISCAT measurements for strong scintillation modelling  

NASA Astrophysics Data System (ADS)

Ionospheric plasma density irregularities may cause rapid fluctuations in the intensity and phase of radio waves propagating through. Usually, scintillation events are modelled in the diffractive scattering approach which is valid for weak scattering conditions. Some mathematical tricks help then in reproducing high levels of scintillation, lacking of full physical meaning. Strong scintillation events are better modelled in the refractive scattering approach, which includes weak scattering conditions. A few parameters (e.g., spatial correlation length and drift velocity) are of key importance in understanding which approach may be correct. Last year, two EISCAT measurement campaigns have been set up in the framework of the Trans-National Access programme, in order to infer and calculate all those parameters useful for numerical modelling of scintillation events. The radar measurement results are compared with transionospheric radio signals at VHF, UHF, and L band in order to understand the feasibility and appropriateness of the two approaches.

Forte, Biagio; Häggström, Ingemar; Turunen, Esa

2010-05-01

121

High-frequency radio-wave ablation of osteoid osteoma in the lumbar spine  

Microsoft Academic Search

The authors report on the first known application in the spine of percutaneous ablation of osteoid osteoma using radio-frequency\\u000a waves. The technique involves a CT-guided biopsy of the lesion followed by introduction of a 1-mm probe connected to a radio-frequency\\u000a lesion generator. The procedure was performed on an outpatient basis and the patient experienced immediate relief of his symptoms.\\u000a No

O. L. Osti; R. Sebben

1998-01-01

122

Analysis of the Temporal Structural Function of Tropospheric Delay of Radio Waves Using Radio Measurements of the Signals from Global Navigation Satellite Systems  

NASA Astrophysics Data System (ADS)

We present the results of a three-year experimental study of propagation of decimeter radio waves in the troposphere. The time analysis of the structural function of tropospheric delay of the decimeter radio waves for the three-year measurements of the GLONASS and GPS signals in a city of Kazan is given. The tropospheric contribution to the variance of the decimeter radio-wave delay is for the first time observed to significantly differ for the variations with time scales 1 to 24 h.

Khutorov, V. E.; Teptin, G. M.

2014-11-01

123

Variation of Langmuir wave polarization with electron beam speed in type III radio bursts  

SciTech Connect

Observations by the twin STEREO spacecraft of in-situ electric field waveforms and radio signatures associated with type III radio bursts have demonstrated that the polarization of electron beam-driven waves near the local plasma frequency depends strongly on the speed of the driving electron beam. We expand upon a previous study by including all radio bursts with in-situ waveforms observed by STEREO in 2011. The expanded data set contains five times more radio bursts (35 up from 7) and three times as many Langmuir waves (663 up from 168). While this expanded study supports the results of the original study, that faster (slower) beam electrons drive waves with strong (weak) electric fields perpendicular to the local magnetic field, the larger data set emphasizes that the observation of strong perpendicular electric fields at high electron beam speeds is probabilistic rather than definite. This property supports the interpretation of wave polarization dependence on beam speed as Langmuir/z-mode waves shifted to small wave number through interaction with turbulent solar wind density fluctuations.

Malaspina, David M. [Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303 (United States); Cairns, Iver H. [School of Physics, University of Sydney, New South Wales 2006 (Australia); Ergun, Robert E. [Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303 (United States) and Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80303 (United States)

2013-06-13

124

Tropospheric scintillation prediction models for a high elevation angle based on measured data from a tropical region  

NASA Astrophysics Data System (ADS)

The recent rapid evolution of new satellite services, including VSAT for internet access, LAN interconnection and multimedia applications, has triggered an increasing demand for bandwidth usage by satellite communications. However, these systems are susceptible to propagation effects that become significant as the frequency increases. Scintillation is the rapid signal fluctuation of the amplitude and phase of a radio wave, which is significant in tropical climates. This paper presents the analysis of the tropospheric scintillation data for satellite to Earth links at the Ku-band. Twelve months of data (January-December 2011) were collected and analyzed to evaluate the effect of tropospheric scintillation. Statistics were then further analyzed to inspect the seasonal, worst-month, diurnal and rain-induced scintillation effects. By employing the measured scintillation data, a modification of the Karasawa model for scintillation fades and enhancements is proposed based on data measured in Malaysia.

Abdul Rahim, Nadirah Binti; Islam, Md. Rafiqul; J. S., Mandeep; Dao, Hassan; Bashir, Saad Osman

2013-12-01

125

Wind-Ulysses Simultaneous Observations of Interplanetary Radio and Plasma Waves : a Pot- pourri  

NASA Astrophysics Data System (ADS)

The radio receivers on the Wind spacecraft (4-13825 kHz) and Ulysses spacecraft (1.25-940 kHz) have continuously observed radio and plasma waves in the interplanetary medium. In the present paper, we shall focus on the solar radio emissions that are generated by flare suprathermal electrons (type III bursts) and by Interplanetary Coronal Mass Ejection (ICME) related shocks (type II bursts), and on the plasma quasi-thermal noise which constitutes the limit background of all radio observations in space. We shall present some examples of simultaneous observations by Ulysses and Wind of type II emissions (radio tracking of ICME driven shocks), of type III bursts (emission mode, localization, directivity), and of plasma thermal noise (solar wind diagnostics).

Hoang, S.; Bonnin, X.; Bougeret, J.; Issautier, K.; Maksimovic, M.

2007-12-01

126

Higher order moments used in ionospheric scintillation description  

NASA Astrophysics Data System (ADS)

Ionospheric scintillations, caused by small scale fluctuations in the electron density structure, presents one of the most influential factor in transionospheric radio wave propagation and important topic for the mitigation of its effects. Initiating disturbances and distortion in phase and amplitude of the propagating signal, scintillation can significantly affect the GNSS accuracy and cause serious problems to commercial navigation systems. Decades of investigations of the probability distribution of the scintillating signals brought a lot of possible solutions, several of them are widely adopted and are in use this days. Solutions like joint Gaussian distribution of complex signal and Rytov solution seems to work for weak scintillating signals, but still there is not an easy way to derive satisfactory results, leading to need for further investigations [Yeh and Liu, 1982]. The focus of this paper is on the statistical analysis of ionospheric scintillation. We analyze various probability distribution functions of scintillating signals using simulated and real data. The analysis results are presented through higher order moments, dependent on various parameters (scintillation index, phase variance, season, time of the day and solar/magnetic activity). Implementation of higher order moments, skewness and kurtosis, could give more information about the ionospheric irregularities influence on the propagating signal and relation to the time delay of the signal.

Stevanovic, D.; Wernik, A. W.

2013-12-01

127

The peculiarities of long-wave radio bursts during the proton events observed on Interball-1  

NASA Astrophysics Data System (ADS)

We analyzed the radio bursts at frequency range 1980 - 100 kHz which were registered by AKR-X (Interball-1) during proton events (SEP). As a rule, we observed radio bursts of III type with large amplitude. The onset of the burst coincided with the explosive (flash) phase of power flare, as we may judge from the comparison of the maximum of the microwave and HXR burst with temporal profile of long-wave radio burst. Accelerated protons escape from the flare without delay and arrived to the Earth during 20-40 min.

Valentina, Prokudina

128

Study of the Radio-Wave Absorbing Properties of a Lithium-Zinc Ferrite Based Composite  

NASA Astrophysics Data System (ADS)

Results are presented of a study of the radio-wave absorbing properties of a composite material based on lithium-zinc ferrite with composition Li0.4Fe2.4Zn0.2O4, synthesized by heating a mechanically activated mixture of the initial reagents Li2CO3-ZnO-Fe2O3 in a high-energy electron beam. It has been shown that a composite based on this material is promising as a radio-wave absorbing coating in the frequency range up to 12 GHz.

Surzhikov, A. P.; Lysenko, E. N.; Malyshev, A. V.; Vlasov, V. A.; Suslyaev, V. I.; Zhuravlev, V. A.; Korovin, E. Yu.; Dotsenko, O. A.

2014-09-01

129

Relations among low ionosphere parameters and high frequency radio wave absorption  

NASA Technical Reports Server (NTRS)

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.

Cipriano, J. P.

1973-01-01

130

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

PubMed

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. PMID:19257596

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

2009-02-13

131

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

PubMed

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. PMID:15783973

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

132

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

SciTech Connect

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.

Norin, L.; Leyser, T. B.; Nordblad, E.; Thide, B.; McCarrick, M. [Swedish Institute of Space Physics, Uppsala (Sweden); BAE Systems Advanced Technologies, Washington, D.C. (United States)

2009-02-13

133

A magnetohydrodynamic mechanism for generating radio waves by bright fireballs  

Microsoft Academic Search

The generation of radio emission and secondary electrophonic phenomena by bright meteor fireballs is investigated theoretically. A mechanism is presented which is based on the qualitative analysis of Keay (1980): twisting of geomagnetic field lines results from turbulent motion in the ion trail and causes amplification of the field to values as high as 1000 Oe. Quantitative calculations show that

V. A. Bronshten

1983-01-01

134

Amplitude distributions of vertically reflected radio waves at Waltair  

Microsoft Academic Search

Amplitude probability distributions of vertically reflected radio pulses from different regions of the ionosphere are presented. The nature of the reflecting surface is found to vary even during short intervals of time. M-type distributions are observed when there is an apparent vertical motion and also during the passage of a traveling ionospheric disturbance. Possible interpretations are given for the observed

B. S. N. Murthy; B. R. Rao

1973-01-01

135

Goniopolarimetric study of the revolution 29 perikrone using the Cassini Radio and Plasma Wave Science instrument high-frequency radio receiver  

Microsoft Academic Search

We present goniopolarimetric (also known as direction finding) results of the Saturn kilometric radiation (SKR), using the Cassini Radio and Plasma Wave Science instrument high-frequency radio receiver data. Tools to retrieve the characteristics of the SKR sources have been developed that allow us to measure their 3-D location and beaming angle relative to the magnetic field in the source and,

B. Cecconi; L. Lamy; P. Zarka; R. Prangé; W. S. Kurth; P. Louarn

2009-01-01

136

Circular Polarization Induced by Scintillation in a Magnetized Medium  

E-print Network

A new theory is presented for the development of circular polarization as radio waves propagate through the turbulent, birefringent interstellar medium. The fourth order moments of the wavefield are calculated and it is shown that unpolarized incident radiation develops a nonzero variance in circular polarization. A magnetized turbulent medium causes the Stokes parameters to scintillate in a non-identical manner. A specific model for this effect is developed for the case of density fluctuations in a uniform magnetic field.

J. -P. Macquart; D. B. Melrose

2000-06-30

137

Monitoring the solar-terrestrial environment using interplanetary scintillation  

NASA Astrophysics Data System (ADS)

Before being detected on Earth, radio waves from a celestial source pass through the interplanetary medium, where they undergo diffraction by plasma density variations in the solar wind, making them appear to scintillate. The amount of scintillation observed can be used to infer the electron density along the line-of-sight to the source. Therefore, when observing many sources across the sky, the solar wind can be mapped out daily. Observations taken over a 5 year period (1990-94) with the Cambridge IPS array are now being analysed at Glasgow. Man-made interference, from sources such as domestic appliances and car engines, is a significant problem in much of these data. Obviously, to get the most out of the data, this noise must be dealt with properly. Another problem is caused by scintillation in the ionosphere. We must be able to distinguish between scintillation caused by the ionosphere, and that caused by the interplanetary medium. Using a model for the expected scintillation profile and timescale for each radio source, it is possible to cut out noise, and to identify periods of ionospheric scintillation in the data. The fitting procedure returns an estimate of both the scintillating power of the source, and the scintillation frequency, which can in turn be used to measure both the density and speed of the solar wind over the whole sky. From this, it's possible to track transient events in the interplanetary medium, such as Coronal Mass Ejections. This whole-sky picture has several advantages over a localised measurement given by an in-situ spacecraft.

Daly, N.

138

Application of surface acoustic wave devices to radio telemetry  

NASA Technical Reports Server (NTRS)

Three experimental Surface Acoustic Wave Resonators (SAWR) are developed and evaluated. A desired center frequency is obtained by correct spacing of the Inter-Digital Transducers (IDT). Transmitting and receiving IDT's must be close for adequate coupling and a sufficient number of reflectors are required to create a high quality standing wave. A review of oscillator theory is given and current technology evaluated.

Strasilla, U.

1983-01-01

139

The effect of radio-wave propagation conditions in the solar corona on the properties of observed type III radio bursts  

Microsoft Academic Search

Geometrical optics is used to perform a ray-tracing analysis of radio waves in the solar corona in the presence of large-scale ducts. It is shown that some of the characteristic features of type III bursts can be explained by taking into account the effects of radio-wave propagation in the inhomomgenous coronal plasma. In particular, it is possible to explain the

M. A. Itkina; V. A. Yashnov

1989-01-01

140

Scintillation Monitoring Using Asymmetry Index  

NASA Astrophysics Data System (ADS)

Variation in electron density can have significant effect on GNSS signals in terms of propagation delay. Ionospheric scintillation can be caused by rapid change of such delay, specifically, when they last for a longer period of time. Ionospheric irregularities that account for scintillation may vary significantly in spatial range and drift with the background plasma at speeds of 45 to 130 m/sec. These patchy irregularities may occur several times during night, e.g. in equatorial region, with the patches move through the ray paths of the GNSS satellite signals. These irregularities are often characterized as either ‘large scale’ (which can be as large as several hundred km in East-West direction and many times that in the North-South direction) or ‘small scale’ (which can be as small as 1m). These small scale irregularities are regarded as the main cause of scintillation [1,2]. In normal solar activity conditions, the mid-latitude ionosphere is not much disturbed. However, during severe magnetic storms, the aurora oval extends towards the equator and the equator anomaly region may stretched towards poles extending the scintillation phenomena more typically associated with those regions into mid-latitudes. In such stormy conditions, the predicted TEC may deviate largely from the true value of the TEC both at low and mid-latitudes due to which GNSS applications may be strongly degraded. This work is an attempt to analyze ionospheric scintillation (S4 index) using ionospheric asymmetry index [3]. The asymmetry index is based on trans-ionospheric propagation between GPS and LEO satellites in a radio occultation (RO) scenario, using background ionospheric data provided by MIDAS [4]. We attempted to simulate one of the recent geomagnetic storms (NOAA scale G4) occurred over low/mid-latitudes. The storm started on 26 September 2011 at UT 18:00 and lasted until early hours of 27 September 2011. The scintillation data for the storm was taken from an ionospheric station in Cairo, Egypt (lat= 29.8641 °, long= 31.3172 °). It was observed that the level of asymmetry was significantly increased during the main phase of the geomagnetic storm. This was due to the changes in ionization, which in turn produced large gradients along occulted ray path in the ionosphere. A very good correlation was found between the evaluated ionospheric asymmetry index and the S4 scintillation index. Additionally, the correlation between evaluated ionospheric asymmetry and errors related to the RO inversion products such as peak electron density (delta NmF2) and Vertical TEC (delta VTEC) estimates also showed promising results. This work is carried out under the framework of the TRANSMIT project (Training Research and Applications Network to Support the Mitigation of Ionospheric Threats - www.transmit-ionosphere.net). [1]Basu Sa. and Basu Su., (1981), ‘Equatorial Scintillation - A Review’, Journal of Atmospheric and Solar-Terrestrial Physics, 43, p. 473. [2]Davies K., (1990), ‘Ionospheric Radio’, IEEE Electromagnetic Waves Series 31, Peter Peregrinus Ltd. [3]Spencer, P., Mitchell, C.N., (2007) ‘Imaging of fast moving electron-density structures in the polar cap’, Annals of Geophysics, vol. 50, no. 3, pp. 427-434. [4]Shaikh, M.M., Notarpietro, R., Nava, B., (2013) ‘The Impact of Spherical Symmetry Assumption on Radio Occultation Data Inversion in the Ionosphere: An Assessment Study’, Advances in Space Research, doi: http://dx.doi.org/10.1016/j.asr.2013.10.025.

Shaikh, Muhammad Mubasshir; Mahrous, Ayman; Abdallah, Amr; Notarpietro, Riccardo

141

Inner- and outer-scale effects on the scintillation index of an optical wave propagating through moderate-to-strong non-Kolmogorov turbulence.  

PubMed

By use of the generalized von Kármán spectrum model that features both inner scale and outer scale parameters for non-Kolmogorov turbulence and the extended Rytov method that incorporates a modified amplitude spatial-frequency filter function under strong-fluctuation conditions, theoretical expressions are developed for the scintillation index of a horizontally propagating plane wave and spherical wave that are valid under moderate-to-strong irradiance fluctuations. Numerical results show that the obtained expressions also compare well with previous results in weak-fluctuation regimes. Based on these general models, the impacts of finite inner and outer scales on the scintillation index of an optical wave are examined under various non-Kolmogorov fluctuation conditions. PMID:22418182

Yi, Xiang; Liu, Zengji; Yue, Peng

2012-02-13

142

Numerical studies of current generation by radio-frequency traveling waves  

Microsoft Academic Search

By injecting radio-frequency traveling waves into a tokamak, continuous toroidal electron currents may be generated. This process is studied by numerically solving the two-dimensional Fokker–Planck equation with an added quasi-linear term. The results are compared with the one-dimensional analytic treatment of Fisch, which predicted a reduced plasma resistivity when high-phase-velocity waves are employed. It is shown that two-dimensional velocity space

Charles F. F. Karney; Nathaniel J. Fisch

1979-01-01

143

Numerical studies of current generation by radio-frequency traveling waves  

Microsoft Academic Search

By injecting radio-frequency traveling waves into a Tokamak, continouous toroidal electron currents may be generated. This process is studied by numerically solving the two-dimensional Fokker-Planck equation with an added quasilinear term. The results are compared with the one-dimensional analytic treatment of Fisch, which predicted a reduced plasma resistivity when high-phase-velocity waves are employed. It is shown that two-dimensional velocity space

C. F. F. Karney; N. J. Fisch

1979-01-01

144

Numerical studies of current generation by radio-frequency traveling waves  

Microsoft Academic Search

By injecting radio-frequency traveling waves into a tokamak, continuous toroidal electron currents may be generated. This process is studied by numerically solving the two-dimensional Fokker-Planck equation with an added quasi-linear term. The results are compared with the one-dimensional analytic treatment of Fisch, which predicted a reduced plasma resistivity when high-phase-velocity waves are employed. It is shown that two-dimensional velocity space

C. F. F. Karney; N. J. Fisch

1979-01-01

145

Radio-wave oscillations of molecular-chain resonators.  

PubMed

We report a new type of nanomechanical resonator system based on one-dimensional chains of only 4 to 7 weakly coupled small molecules. Experimental characterization of the truly nanoscopic resonators is achieved by means of a novel radio-frequency scanning tunneling microscopy detection technique at cryogenic temperatures. Above 20 K we observe concerted oscillations of the individual molecules in chains, reminiscent of the first and second eigenmodes of a one-dimensional harmonic resonator. Radio-frequency scanning tunneling microscopy based frequency measurement reveals a characteristic length dependence of the oscillation frequency (between 51 and 127 MHz) in reasonable agreement with one-dimensional oscillator models. Our study demonstrates a new strategy for investigating and controlling the resonance properties of nanomechanical oscillators. PMID:24702407

Müllegger, Stefan; Rashidi, Mohammad; Mayr, Karlheinz; Fattinger, Michael; Ney, Andreas; Koch, Reinhold

2014-03-21

146

Radio Wave Characterization and Modeling in Underground Mine Tunnels  

Microsoft Academic Search

Results are presented on wideband radio propagation measurements and statistical modeling at 2.4 GHz and 5.8 GHz in real underground mine tunnels. This peculiar type of confined environment is characterized by very rough surfaces and a frequent absence of a line-of-sight between transmitting and receiving antennas. The resulting propagation characteristics differ from those frequently encountered in more typical indoor environments

Mathieu Boutin; Ahmed Benzakour; Charles L. Despins; Sofiène Affes

2008-01-01

147

EFFECTS OF RADIO WAVE PROPAGATION IN URBANIZED AREAS ON UAV-GCS COMMAND AND CONTROL  

E-print Network

EFFECTS OF RADIO WAVE PROPAGATION IN URBANIZED AREAS ON UAV-GCS COMMAND AND CONTROL Lock Wai Lek In an urban environment, the linkage between UAVs and ground control stations are subjected to multipath multipath can result in a nearly complete loss of command signals, which can limit the UAV's operational

Jenn, David C.

148

ENERGY EFFICIENT MILLIMETER WAVE RADIO LINK ESTABLISHMENT WITH SMART ARRAY ANTENNAS  

E-print Network

1 ENERGY EFFICIENT MILLIMETER WAVE RADIO LINK ESTABLISHMENT WITH SMART ARRAY ANTENNAS Behnam unnecessary directions. The collection of all these benefits, points to using smart array antennas as a tool array antenna that has beamforming capability. We are interested in using the beamforming capability

Baras, John S.

149

Radio-Wave Propagation in the Non-Gaussian Interstellar Medium  

Microsoft Academic Search

Radio waves propagating from distant pulsars in the interstellar medium (ISM) are refracted by electron density inhomogeneities, so the intensity of observed pulses fluctuates with time. The observed pulse shapes are used to diagnose electron density distribution in the ISM. The theory relating the observed pulse time shapes to the electron density correlation function has developed for 30 years; however,

Stanislav Boldyrev; Carl R. Gwinn

2005-01-01

150

Generation of stimulated emission by a traveling ionization front during breakdown in intersecting radio wave beams  

Microsoft Academic Search

The possibility of obtaining atmospheric pressure laser action at the second positive system of nitrogen in the case of pulsed breakdown in intersecting radio wave beams is discussed. The intensity of stimulated emission is calculated, and numerical estimates of the effect are presented.

N. D. Borisov; A. V. Gurevich

1991-01-01

151

Method of Studying Travel Time Anomalies of High Frequency Radio Waves  

Microsoft Academic Search

A device utilizing pulse techniques has been built for automatic measurement of changes in radio wave travel times. The equipment uses a combination of amplitude, time, and frequency selection for discrimination against unwanted signals. The received signals from U. S. time standard station WWV are sampled at 1-sec intervals to measure changes in the time of reception of the 1-sec

Gordon Lerfald; Paul Scheibe

1960-01-01

152

Incoherent Scattering of Radio Waves by Free Electrons with Applications to Space Exploration by Radar  

Microsoft Academic Search

Free electrons in an ionized medium scatter radio waves weakly. Under certain conditions only incoherent scattering exists. A powerful radar can detect the incoherent backscatter from the free electrons in and above the earth's ionosphere. The received signal is spread in frequency by the Doppler shifts associated with the thermal motion of the electrons. On the basis of incoherent backscatter

W. E. Gordon

1958-01-01

153

An overview of observations by the Cassini radio and plasma wave investigation at earth  

Microsoft Academic Search

On August 18, 1999, the Cassini spacecraft flew by Earth at an altitude of 1186 km on its way to Saturn. Although the flyby was performed exclusively to provide the spacecraft with sufficient velocity to get to Saturn, the radio and plasma wave science (RPWS) instrument, along with several others, was operated to gain valuable calibration data and to validate

W. S. Kurth; G. B. Hospodarsky; D. A. Gurnett; M. L. Kaiser; J.-E. Wahlund; A. Roux; P. Canu; P. Zarka; Y. Tokarev

2001-01-01

154

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

ERIC Educational Resources Information Center

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.)

Hare, Jonathan

2010-01-01

155

MEETING REPORT: SRP Meeting: Radio Wave Exposures - A Cause for Concern? (Preston, June 2002)  

Microsoft Academic Search

The purpose of the meeting was to explore issues raised concerning exposures to radio waves arising from radiofrequency and microwave communication technologies. The meeting was held at Ribby Hall Conference Centre, near Preston, on 27 June 2002 and was attended by 72 delegates. After an introduction by Ian MacDiarmid (BAE SYSTEMS), Tim Cooper (NRPB) gave the first presentation of the

Raj Bunger

2002-01-01

156

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

NASA Technical Reports Server (NTRS)

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.

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

157

Radio and plasma wave observations at Saturn from Cassini's approach and first orbit.  

PubMed

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 +/- 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. PMID:15604362

Gurnett, D A; Kurth, W S; Hospodarsky, G B; Persoon, A M; Averkamp, T F; Cecconi, B; Lecacheux, A; Zarka, P; Canu, P; Cornilleau-Wehrlin, N; Galopeau, P; Roux, A; Harvey, C; Louarn, P; Bostrom, R; Gustafsson, G; Wahlund, J-E; Desch, M D; Farrell, W M; Kaiser, M L; Goetz, K; Kellogg, P J; Fischer, G; Ladreiter, H-P; Rucker, H; Alleyne, H; Pedersen, A

2005-02-25

158

A Forecasting Ionospheric Real-time Scintillation Tool (FIRST)  

NASA Astrophysics Data System (ADS)

Transionospheric radio waves propagating through an irregular ionosphere with plasma depletions, or "bubbles," are subject to sporadic enhancement and fading commonly referred to as scintillation. Knowledge of the current ionospheric condition allows system operators to distinguish between compromises due to the radio environment and system induced failures, while a forecast of the same provides the opportunity for operators to take appropriate actions to mitigate the effects and optimize service. This paper describes a technique that uses the readily accessible ionospheric characteristic h'F from ground-based ionospheric sounder data near the geomagnetic equator to forecast the occurrence or nonoccurrence of low-latitude scintillation activity in VHF/UHF bands. We illustrate the development of the Forecasting Ionospheric Real-time Scintillation Tool and its real-time capability for forecasting scintillation activity. Finally, we have found that there exists a threshold in the h'F value at 1930 LT that corresponds to the onset of scintillation activity in the Peruvian longitude sector, which is found to decrease with decreasing F10.7 cm fluxes in a linear manner.

Redmon, Robert J.; Anderson, David; Caton, Ron; Bullett, Terence

2010-12-01

159

Enhanced scintillations associated with high speed streams in the solar winds  

NASA Astrophysics Data System (ADS)

The long wavelength (lambda greater than the ion-gyro radius) density homogeneities in the solar wind that raise the stellar radio scintillation index during the onset of a high-velocity stream, may be generated by a low-frequency compressional electromagnetic mode such as the magnetosonic (MS) wave. The present investigation shows that obliquely propagating MS waves are driven unstable by the double-peaked proton distributions observed in the solar wind. This is proposed as a reason for the correlation of high speed streams with enhanced scintillation. The stability at 1 AU of the observed nonequilibrium, double-peaked particle distributions emerges as a natural consequence of the suggested mechanism.

Basu, A.; Das, A. C.

1982-03-01

160

Combined evidence for four- and three-wave interactions in solar type III radio bursts  

NASA Astrophysics Data System (ADS)

The high time resolution observations obtained by the STEREO/WAVES experiment show that in solar type III radio bursts, Langmuir waves often occur as intense one-dimensional or three-dimensional wave packets. We present the observations of one of the 1d wave packets as well as one of the 3d wave packets, whose short durations and peak intensities satisfy the threshold conditions for the oscillating two-stream instability (OTSI) and formation of collapsing envelope solitons. The depths, widths and temporal coincidences of the density cavities, observed during these wave packets indicate that they probably correspond to cavitons, generated by the ponderomotive force of the collapsing wave packets. The spectrum of each of the parallel and perpendicular components of the 3d wave packet as well as the spectrum of the parallel component of the 1d wave packet show similar characteristics, namely, each of them contains a primary peak at fpe, two secondary peaks at fpe×fS and a low-frequency enhancement below fS, which, as indicated by the frequency and wave number resonance conditions, and the fast Fourier transform (FFT)-based tricoherence spectral peak at (fpe, fpe, fpe+fS, fpe- fS) are coupled to each other by the OTSI type of four-wave interaction (fpe is the local electron plasma frequency and fS is the frequency of ion sound waves). In addition to the primary peak at fpe, each of these spectra also contains a peak at 2fpe, which as indicated by the frequency and wave number resonance conditions, and the waveletbased bicoherence spectral peak at (fpe, fpe), appears to correspond to the second harmonic electromagnetic waves generated as a result of coalescence of oppositely propagating sidebands excited by the OTSI. Additionally, the spectrum of the 1d wave packet also contains a peak at 3fpe, which as indicated by the bispectral analysis probably corresponds to electromagnetic waves excited as a result of merging of Langmuir waves with second harmonic electromagnetic waves. Thus, these observations for the first time provide combined evidence that (1) the OTSI and related strong turbulence processes play a significant role in the stabilization of the electron beam, (2) the coalescence of the oppositely propagating up- and down-shifted daughter Langmuir waves excited by the OTSI probably is the emission mechanism of the second harmonic radiation, and (3) the Langmuir collapse follows the route of OTSI in some of the type III radio bursts.

Golla, T.; MacDowall, R. J.

2013-12-01

161

Stratospheric warmings, atmospheric circulation, and radio wave absorption in the lower ionosphere  

NASA Astrophysics Data System (ADS)

The relationship between stratospheric warmings and radio wave absorption in the lower ionosphere is examined with reference to results of the program Winter in Northern Europe. The results of the program support the conclusion that warmings in the stratosphere are accompanied by an increase in the activity of planetary waves, a weakening and reversal of the western zonal wind in the lower atmosphere (height, about 95 km), a decrease in electron concentration at heights of 75-95 km, and radio wave absorption. The results are consistent with the concept of the role of the cyclonic circumpolar wind in the transfer of NO-enriched auroral air to midlatitudes and creation of anomalous winter conditions at midlatitudes.

Rapoport, Z. Ts.

162

Nonlinear Wave Interactions as Emission Process of Type II Radio Bursts  

NASA Astrophysics Data System (ADS)

The emission of fundamental and harmonic frequency radio waves of type II radio bursts are assumed to be products of three-wave interaction processes of beam-excited Langmuir waves. Using a particle-in-cell code, we have performed simulations of the assumed emission region, a coronal mass ejection foreshock with two counterstreaming electron beams. Analysis of wavemodes within the simulation shows self-consistent excitation of beam-driven modes, which yield interaction products at both fundamental and harmonic emission frequencies. Through variation of the beam strength, we have investigated the dependence of energy transfer into electrostatic and electromagnetic modes, confirming the quadratic dependence of electromagnetic emission on electron beam strength.

Ganse, Urs; Kilian, Patrick; Spanier, Felix; Vainio, Rami

2012-06-01

163

Mapping Natural and Man-made Radio Interference at the Moon: Wind Waves RAD2 Data  

NASA Astrophysics Data System (ADS)

The lunar surface is frequently identified as a preferred site for large, low-frequency (<50-100 MHz) interferometric radio observatories. Compared to ground-based facilities limited to above 10 MHz by ionospheric absorption, the Moon has essentially no ionosphere. Observations of radio sources at frequencies below 100 kHz would be possible. Compared to a free-flying spacecraft constellation, the lunar surface provides a surface for deploying antennas, after which the antenna metrology is not an issue. Also compared to the spacecraft constellation, the moon offers a “backstop” that can block unwanted radio emissions from the sun or, for a far-side array, from man-made transmitters on Earth as well as terrestrial auroral radio emissions. We present an analysis of the Wind Waves RAD2 radio data set for the frequency range 1-14 MHz. These data, acquired from November 1994 through the present, document the radio bursts and terrestrial emissions observed by Wind along a complex trajectory that included passes very close to the Moon. Thus, we can build a statistical “map” of terrestrial radio emissions as a function of local time of the Moon relative to earth, the inclination of the moon’s orbit, and frequency. These data demonstrate that successful radio observations of cosmological sources from anywhere near Earth will be best accomplished by an observatory on the far-side of the Moon. The data also provide statistics regarding interference from solar radio emissions, including variations as a function of the solar cycle, with any observations requiring high sensitivity.

MacDowall, R. J.; Hess, R. A.; Kaiser, M. L.; Farrell, W. M.

2009-12-01

164

The seasonal variation of the D region as inferred from propagation characteristics of LF radio waves  

NASA Technical Reports Server (NTRS)

The propagation data of JG2AS 40 kHz (Japanese Standard Frequency), Loran C 100 kHz radio waves, and meteorological data were analyzed to study the association of propagation characteristics of LF radio waves with the atmospheric circulation in the mesosphere. The monthly averaged electric fields were depicted on the complex plane for typical summer and winter months, June and November. The locus traced out by the electric field vector during daytime is nearly circular. This is because during daytime the amplitude of the sky wave remains nearly constant while its phase changes in accord with the height change of the reflection layer, and thus the electric field vector traces out a circular locus with its center at the tip of the supposed ground wave vector. The locus has a loop during the sunrise or sunset period, which seems to arise from interference of two waves reflected by two different layers. In June the amplitude of the sky wave decreases rapidly before the dawn or increases after the dusk. In November such rapid change is not observed. During nighttime, the sky wave phase changes in such a way as to suggest that the reflection height moves upwards with time before midnight or lowers after midnight in November. In June it changes similarly before midnight, but after midnight it varies erratically. These characteristics are closely related to the structure of the D region, which is clearly shown by simulating the loci traced out by electric fields.

Ishimine, T.; Ishii, T.; Echizenya, Y.

1985-01-01

165

Radio Frequency Wave Experiment on the MST Reversed Field Pinch  

Microsoft Academic Search

Experiment, theory and simulation all indicate that fluctuation responsible for the poor confinement in reversed field pinch (RFP) plasma can be controlled by altering the radial current density profile. Ray tracing and Fokker-Plank calculations indicate the lower hybrid slow wave is feasible for current profile control and heating in the RFP. LH experiment in MST aims to: (1) demonstrate coupling

P. K. Chattopadhyay; C. B. Forest; M. A. Thomas; M. D. Nornberg; S. C. Prager; E. Uchimoto

1999-01-01

166

Fast electron generation on MST via radio-frequency waves  

Microsoft Academic Search

Lower hybrid current drive has been proposed as a means of improving confinement in the reversed field pinch by reducing tearing fluctuations. The particular constraints of the Madison Symmetric Torus have led to the use of a novel interdigital-line traveling wave antenna structure rather than the traditional waveguide grill antenna. Since hard x-ray (HXR) flux from bremsstrahlung is a standard

M. C. Kaufman; D. R. Burke; J. A. Goetz; C. B. Forest

2010-01-01

167

Review of Ionospheric Scintillation Models and proposing a Novel Model for Characterizing High Latitude Irregularities  

NASA Astrophysics Data System (ADS)

The study of ionospheric scintillations of radio signal involves a problem of electromagnetic (EM) wave propagation in random media and has been a subject of interest for more than last 5 decades. Some of the representative works are by Booker et. al (1950), Ratcliffe (1956), Wernik and Liu (1975), Yeh and Liu (1982), Secan et. al (1995), Costa and Basu (2002), Rino and Carrano (2011). Many of the scintillation models employ a phase screen model introduced by Rino (1979). Beniguel and Hamel (2011) implemented a global ionospheric scintillation model for equatorial regions showing a good agreement of the model with measurements. Implementing these models in the study of ionospheric scintillations of radio signals at high latitudes could be challenging since the path of satellite signal to ground has a variable angle of incidence, in addition to the complicated geometry of magnetic field lines at high latitude and polar regions, and complex magnetosphere-ionosphere coupling mechanisms creating the irregularities. We have developed a high fidelity 3-dimensional Global Positioning System Ionospheric Scintillation Model (3D-GPSISM) which is a full 3D EM wave propagation model to simulate GPS scintillations in high latitude ionosphere. The results from this model can form a basic framework on the use of inverse method to understand the physics of high latitude irregularities using GPS scintillations. We are using our model and an inverse method for selected scintillation observations during 2010 - 2013 from GPS receivers at South Pole, McMurdo and remote stations on Antarctica in conjunction with ancillary observations from SuperDARN, magnetometers, All Sky Imagers etc. We believe that such inverse method can be used to derive certain characteristics of the irregularity causing the scintillations and further achieve an improved understanding of the physics of high latitude irregularities.

Deshpande, K.; Bust, G. S.; Clauer, C. R.

2013-12-01

168

Observational evidence for the collapsing Langmuir wave packet in a solar type III radio burst  

NASA Astrophysics Data System (ADS)

High time resolution observations from the STEREO spacecraft show that in solar type III radio bursts, Langmuir waves often occur as very intense one-dimensional magnetic field aligned field structures. One of these events represents the most intense Langmuir wave packet with WLneTe~7.2×10-3 ever detected in a type III radio burst until now (WL is the peak energy density, and ne and Te are the electron density and temperature, respectively). The detailed analysis of this wave packet indicates that (1) its peak intensity is well above the threshold for the oscillating two-stream instability (OTSI) and supersonic collapse; (2) its peak intensity and spatial scale satisfy the criterion for it to be a collapsing envelope soliton; (3) its low-frequency components provide evidence for a density cavity, whose depth, width, and temporal coincidence indicate that probably it is the ponderomotive force generated density cavity; and (4) its spectrum contains harmonic peaks at 2fpe and 3fpe (in addition to the main Langmuir wave peak at the electron plasma frequency, fpe), which, as indicated by the bispectral analysis, probably are of the electromagnetic waves generated as a result of coalescence of two oppositely propagating Langmuir waves, and a Langmuir wave and a second harmonic electromagnetic wave, respectively. These characteristics strongly suggest that this wave packet and its associated density cavity represent the collapsing envelope soliton-caviton pair formed as a result of OTSI, and in the present case, the strong turbulence processes probably play key roles in the beam stabilization as well as conversion of Langmuir waves into escaping radiation at 2fpe and 3fpe.

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

2013-07-01

169

Detection of collapsing Langmuir wave packets in solar type III radio bursts  

NASA Astrophysics Data System (ADS)

We report the STEREO/WAVES high time resolution observations of an intense Langmuir wave packet associated with a solar type III radio burst. The transformation of the electric field measurements from the spacecraft into magnetic field aligned coordinate system indicates that this is a field aligned one-dimensional structure. The peak intensity and short duration of this wave packet well satisfy the criterion for it to be the collapsing envelope soliton trapped in a self-generated density cavity. The spectrum of this 1D wave packet consists of an intense peak and two sidebands, corresponding to beam-resonant Langmuir waves, and down- and up-shifted daughter Langmuir waves, respectively, and an ion sound associated low-frequency enhancement. The frequencies and wave numbers of these spectral components satisfy the resonance conditions of the four wave interaction, called the oscillating two stream instability (OTSI). Furthermore, trispectral analysis indicates that these spectral components are coupled to each other with a high degree of phase coherency (high tricoherence). These findings provide a strong indication that the observed wave packet is a collapsing Langmuir envelope soliton formed as a result of OTSI.

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

2013-06-01

170

Efficient Computation of Prolate Spheroidal Wave Functions in Radio Astronomical Source Modeling  

E-print Network

The application of orthonormal basis functions such as Prolate Spheroidal Wave Functions (PSWF) for accurate source modeling in radio astronomy has been comprehensively studied. They are of great importance for high fidelity, high dynamic range imaging with new radio telescopes as well as conventional ones. But the construction of PSWF is computationally expensive compared to other closed form basis functions. In this paper, we suggest a solution to reduce its computational cost by more efficient construction of the matrix kernel which relates the image domain to visibility (or Fourier) domain. Radio astronomical images are mostly represented using a regular grid of rectangular pixels. This is required for efficient storage and display purposes and moreover, comes naturally as a by product of the Fast Fourier Transform (FFT) in imaging. We propose the use of Delaunay triangulation as opposed to regular gridding of an image for a finer selection of the region of interest (signal support) during the PSWF kernel...

Noorishad, Parisa

2011-01-01

171

The TIR system - A two-frequency interferometer for the investigation of transionospheric radio-wave propagation  

Microsoft Academic Search

The design and characteristics of a radio interferometer (the TIR system) for investigating transionospheric radio-wave propagation at frequencies of 136 and 714 MHz are described. Measured radio-signal field parameters will be used to determine the characteristics of the space-time variability of the ionosphere, from traveling ionospheric disturbances that are responsible for signal refraction to the spectrum of small-scale irregularities that

E. L. Afraimovich; V. N. Zvezdin; N. P. Min'ko; A. N. Shapovalov

1989-01-01

172

An Overview of Observations by the Cassini Radio and Plasma Wave Investigation at Earth  

NASA Technical Reports Server (NTRS)

On August 18, 1999, the Cassini spacecraft flew by Earth at an altitude of 1186 km on its way to Saturn. Although the flyby was performed exclusively to provide the spacecraft with sufficient velocity to get to Saturn, the radio and plasma wave science (RPWS) instrument, along with several others, was operated to gain valuable calibration data and to validate the operation of a number of capabilities. In addition, an opportunity to study the terrestrial radio and plasma wave environment with a highly capable instrument on a swift fly-through of the magnetosphere was afforded by the encounter. This paper provides an overview of the RPWS observations, at Earth, including the identification of a number of magnetospheric plasma wave modes, an accurate measurement of the plasma density over a significant portion of the trajectory using the natural wave spectrum in addition to a relaxation sounder and Langmuir probe, the detection of natural and human-produced radio emissions, and the validation of the capability to measure the wave normal angle and Poynting flux of whistler-mode chorus emissions. The results include the observation of a double-banded structure at closest' approach including a band of Cerenkov emission bounded by electron plasma and upper hybrid frequencies and an electron cyclotron harmonic band just above the second harmonic of the electron cyclotron frequency. In the near-Earth plasma sheet, evidence for electron phase space holes is observed, similar to those first reported by Geotail in the magnetotail. The wave normal analysis confirms the Polar result that chorus is generated very close to the magnetic equator and propagates to higher latitudes. The integrated power flux of auroral kilometric radiation is also used to identify a series of substorms observed during the outbound passage through the magnetotail.

Kurth, W. S.; Hospodarsky, G. B.; Gurnett, D. A.; Kaiser, M. L.; Wahlund, J.-E.; Roux, A.; Canu, P.; Zarka, P.; Tokarev, Y.

2001-01-01

173

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

PubMed

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 ?-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 ?-ray bursts does not constrain the radio transients that we discuss here (from mildly relativistic and subrelativistic outflows) because short ?-ray burst redshifts are typically >0.1 and the appropriate timescales (longer than weeks) have not been sampled. PMID:21964342

Nakar, Ehud; Piran, Tsvi

2011-10-01

174

Evidence for four- and three-wave interactions in solar type III radio emissions  

NASA Astrophysics Data System (ADS)

The high time resolution observations obtained by the STEREO/WAVES experiment show that in the source regions of solar type III radio bursts, Langmuir waves often occur as intense localized wave packets with short durations of only few ms. One of these wave packets shows that it is a three-dimensional field structure with WLneTe ~ 10-3, where WL is the peak energy density, and ne and Te are the electron density and temperature, respectively. For this wave packet, the conditions of the oscillating two-stream instability (OTSI) and supersonic collapse are satisfied within the error range of determination of main parameters. The density cavity, observed during this wave packet indicates that its depth, width and temporal coincidence are consistent with those of a caviton, generated by the ponderomotive force of the collapsing wave packet. The spectrum of each of the parallel and perpendicular components of the wave packet contains a primary peak at fpe, two secondary peaks at fpe ± fS and a low-frequency enhancement below fS, which, as indicated by the frequency and wave number resonance conditions, and the fast Fourier transform (FFT)-based tricoherence spectral peak at (fpe, fpe, fpe + fS, fpe - fS), are coupled to each other by the OTSI type of four-wave interaction (fpe is the local electron plasma frequency and fS is the frequency of ion sound waves). In addition to the primary peak at fpe, each of these spectra also contains a peak at 2fpe, which as indicated by the frequency and wave number resonance conditions, and the wavelet-based bicoherence spectral peak at (fpe, fpe), appears to correspond to the second harmonic electromagnetic waves generated as a result of coalescence of oppositely propagating sidebands excited by the OTSI. Thus, these observations for the first time provide combined evidence that (1) the OTSI and related strong turbulence processes play a significant role in the stabilization of the electron beam, (2) the coalescence of the oppositely propagating up- and down-shifted daughter Langmuir waves excited by the OTSI probably is the emission mechanism of the second harmonic radiation, and (3) the Langmuir collapse follows the route of OTSI in some of the type III radio bursts.

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

2013-08-01

175

The Doppler frequency of reflected radio waves from a travelling ionospheric disturbance in the mode of a sinusoidal surface  

Microsoft Academic Search

In the geometrical optics approximation, the Doppler frequency of radio waves reflected from a traveling ionospheric disturbance (TID) in the mode of a sinusoidal perfectly reflecting surface is determined

O. L. Ivantyshyn; V. V. Koshevoj; O. E. Levitski

1997-01-01

176

Experimental comparison between centimeter- and millimeter-wave ultrawideband radio channels  

NASA Astrophysics Data System (ADS)

paper analyzes radio wave propagation phenomena at two very different frequency bands: 2-10 GHz (centimeter wave) and 57-66 GHz (millimeter wave (mm-W)). The two frequency bands have been measured using the same equipment and under similar propagation conditions, such as path loss, root-mean-square delay spread, maximum excess delay, and Rician K factor, and their respective correlations compared. Obstructed line of sight situations have also been considered by using metal and cardboard obstructions. The statistical distributions, main specular reflections, and decay factors have been found similar for the two bands. However, the measured path loss, correlation in terms of electrical distances, and the K factor are higher for the millimeter-wave frequency band. Indeed, the importance of propagation mechanism changes from one band to the other, which must be considered in the design of future mm-W systems.

Martinez-Ingles, Maria-Teresa; Molina-Garcia-Pardo, Jose-Maria; Rodríguez, José-Víctor; Pascual-García, Juan; Juan-Llácer, Leandro

2014-06-01

177

Model of Inductive Plasma Production Assisted by Radio-Frequency Wave in Tokamaks  

Microsoft Academic Search

For initial plasma production, an induction electric field generated by applying voltage to a poloidal field (PF) coil system is used to produce a Townsend avalanche breakdown. When the avalanche margins are small, as for the International Thermonuclear Experimental Reactor (ITER) in which the induction electric field is about 0.3 V\\/m, the assistance of radio-frequency waves (RF) is provided to

Makoto Hasegawa; Kazuaki Hanada; Kohnosuke Sato; Kazuo Nakamura; Hideki Zushi; Mizuki Sakamoto; Hiroshi Idei; Shoji Kawasaki; Hisatoshi Nakashima; Aki Higashijima

2007-01-01

178

Simultaneous measurements of the frequency and bearing of h.f. radio waves  

Microsoft Academic Search

The presence of traveling ionospheric disturbances (t.i.d.s) at the reflection point of h.f. radio waves, propagated at oblique incidence, has been monitored by means of a Doppler-frequency sounder. The bearing error measured by a direction finder at one end of the oblique path is shown to be correlated with the t.i.d. activity at the path mid-point. The magnitudes of the

T. B. Jones; E. Kantarizis; A. D. Morgan

1975-01-01

179

A New Approach Towards Large Scale Soil Moisture Mapping by Radio Waves  

Microsoft Academic Search

A new approach for obtaining integrated estimates of soil moisture content over larger regions of typically 10–50 km is described.\\u000a It is based on a known correlation between propagation characteristics of low frequency radio surface waves and surface soil\\u000a moisture, and provides valuable new benefits especially for meteorological prognostic models and for soil water estimation\\u000a in agriculture. The paper consists of

Christof Huebner; Christoph Kottmeier; Alexander Brandelik

2011-01-01

180

The effect of radio-wave propagation conditions in the solar corona on the properties of observed type III radio bursts  

NASA Astrophysics Data System (ADS)

Geometrical optics is used to perform a ray-tracing analysis of radio waves in the solar corona in the presence of large-scale ducts. It is shown that some of the characteristic features of type III bursts can be explained by taking into account the effects of radio-wave propagation in the inhomomgenous coronal plasma. In particular, it is possible to explain the fact that the radial coordinates of the point of radio-wave emergence from the corona exceed the level of the fundamental plasma frequency, and the fact that the bursts of decametric storms are observed at the fundamental frequency near the central meridian and at the second harmonic near the solar limb.

Itkina, M. A.; Yashnov, V. A.

1989-10-01

181

Thunderstorms, lightning, sprites and magnetospheric whistler-mode radio waves  

E-print Network

Thunderstorms and the lightning that they produce are inherently interesting phenomena that have intrigued scientists and mankind in general for many years. The study of thunderstorms has rapidly advanced during the past century and many efforts have been made towards understanding lightning, thunderstorms and their consequences. Recent observations of optical phenomena above an active lightning discharge along with the availability of modern technology both for data collection and data analysis have renewed interest in the field of thunderstorms and their consequences in the biosphere. In this paper, we review the electrification processes of a thunderstorm, lightning processes and their association with global electric circuit and climate. The upward lightning discharge can cause sprites, elves, jets, etc. which are together called transient luminous events. Their morphological features and effects in the mesosphere are reviewed. The wide spectrum of electromagnetic waves generated during lightning discharg...

Siingh, Devendraa; Patel, R P; Singh, Rajesh; Singh, R P; Veenadhari, B; Mukherjee, M

2009-01-01

182

Phase Coupling in Langmuir Wave Packets: Evidence for Four Wave Interactions in Solar Type III Radio Bursts  

NASA Technical Reports Server (NTRS)

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.

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

2012-01-01

183

FURTHER STUDY OF RAINFALL EFFECT ON VHF FORESTED RADIO-WAVE PROPAGATION WITH FOUR-LAYERED MODEL  

Microsoft Academic Search

In this paper, rainfall efiect on the VHF radio-wave propagation in a tropical forest is further studied in details. Theoretical study and experimental investigations are performed with the help of a four-layered model for forested environment. It is found that the lateral wave traveling along the air-canopy interface, the direct waves, and the ground re?ected waves are the main modes

Yu Song Meng; Yee Hui Lee; Boon Chong Ng

2009-01-01

184

On seeding, large-scale wave structure, equatorial spread F, and scintillations over Vietnam  

NASA Astrophysics Data System (ADS)

Understanding the day-to-day variability in occurrence of equatorial spread F (ESF) remains as a high-priority objective in space weather research. A major difficulty has been an inability to resolve the roles being played by large-scale wave structure (LSWS) and the post-sunset rise (PSSR) of the equatorial F layer, in the production of ESF. In this paper, we show conclusively that total electron content (TEC), measured as a function of latitude and longitude, provides clear, routine descriptions of LSWS. Then, together with ionosonde data, we show, for the first time, that while a seed for LSWS can occur in the late afternoon, its amplification takes place mostly during the PSSR. Implications of these findings are discussed in light of existing theories.

Tsunoda, Roland T.; Yamamoto, Mamoru; Tsugawa, Takuya; Hoang, Thai Lan; Tulasi Ram, S.; Thampi, Smitha V.; Chau, Ha Duyen; Nagatsuma, Tsutomu

2011-10-01

185

Radial Distribution of Compressive Waves in the Solar Corona Revealed by Akatsuki Radio Occultation Observations  

NASA Astrophysics Data System (ADS)

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 RS (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 RS , implying that nonlinearity of the wave field is potentially important. We further estimate the wave energy flux on the assumption that the observed periodical fluctuations are manifestations of acoustic waves. The energy flux increases with distance below ~6 RS 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.

Miyamoto, Mayu; Imamura, Takeshi; Tokumaru, Munetoshi; Ando, Hiroki; Isobe, Hiroaki; Asai, Ayumi; Shiota, Daikou; Toda, Tomoaki; Häusler, Bernd; Pätzold, Martin; Nabatov, Alexander; Nakamura, Masato

2014-12-01

186

Computational strategy for modeling radio wave propagation in lossy circular waveguides  

SciTech Connect

The propagation of radio waves in lossy waveguides and tunnels has been researched extensively for many years as can be seen in the detailed book by Wait. The mathematics used to model waveguides for communications is essentially the same as that needed to model radio frequency (RF) propagation in simple tunnels. The presence or lack of conductors inside a waveguide or tunnel is a key driver in the nature of the solutions one will find for a particular application, Delogne. When there are conductors passing through a waveguide or tunnel, the simplest modes of propagation are surface-guided waves following the conductor and typically enabling long-range transmission. A tunnel containing a core conductor can act rather like a coaxial cable, propagating waves at a nearly constant speed, regardless of frequency. Conversely, a tunnel or waveguide without internal conductors is subject to very different wave patterns, resulting in a much more complex propagation analysis. Holloway et al. presented an exhaustive study of RF propagation in circular structures embedded in lossy surroundings. The work of Holloway et al. is the basis for this paper, where we discuss application of their computational techniques and present refinements gleaned from our work on similar problems.

Moses, Ronald [Los Alamos National Laboratory; Cai, D Michael [Los Alamos National Laboratory

2008-01-01

187

An Experiment Study of the Propagation of Radio Waves in a Scaled Model of Long-Wall Coal Mining Tunnels  

SciTech Connect

A long-wall coal mining tunnel is the most important working area in a coal mine. It has long been realized that radio communications can improve both productivity and safety in this dangerous area. Hence, many attempts to use radio communications in such an environment have been made. Unfortunately, no radio system has satisfactorily provided communication services there, which, we believe, is partially due to poor understanding of the propagation characteristics of radio waves in the long-wall mining tunnel. To have deeper physical insight into the propagation problem, a scaled model of the long-wall mining tunnel was built, and the propagation characteristics of UHF radio waves were measured. The experiment and the measured results are presented and discussed.

Han, G.R.; Zhang, W.M.; Zhang, Y.P. [Shanxi University, Taiyuan (China)

2009-07-01

188

Verification of particle simulation of radio frequency waves in fusion plasmas  

SciTech Connect

Radio frequency (RF) waves can provide heating, current and flow drive, as well as instability control for steady state operations of fusion experiments. A particle simulation model has been developed in this work to provide a first-principles tool for studying the RF nonlinear interactions with plasmas. 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 equation. This model has been implemented in a global gyrokinetic toroidal code using real electron-to-ion mass ratio. To verify the model, linear simulations of ion plasma oscillation, ion Bernstein wave, and lower hybrid wave are carried out in cylindrical geometry and found to agree well with analytic predictions.

Kuley, Animesh; Lin, Z. [Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States) [Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States); Fusion Simulation Center, Peking University, Beijing 100871 (China); Wang, Z. X. [Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States)] [Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States); Wessel, F. [Tri Alpha Energy, Inc., Post Office Box 7010, Rancho Santa Margarita, California 92688 (United States)] [Tri Alpha Energy, Inc., Post Office Box 7010, Rancho Santa Margarita, California 92688 (United States)

2013-10-15

189

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

DOEpatents

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.

Ives, R. Lawrence (Saratoga, CA); Mizuhara, Yosuke M. (Palo Alto, CA); Schumacher, Richard V. (Sunnyvale, CA); Pendleton, Rand P. (Saratoga, CA)

1999-01-01

190

Creation of visible artificial optical emissions in the aurora by high-power radio waves.  

PubMed

Generation of artificial light in the sky by means of high-power radio waves interacting with the ionospheric plasma has been envisaged since the early days of radio exploration of the upper atmosphere, with proposed applications ranging from regional night-time street lighting to atmospheric measurements. Weak optical emissions have been produced for decades in such ionospheric 'heating' experiments, where they serve as key indicators of electron acceleration, thermal heating, and other effects of incompletely understood wave-particle interactions in the plasma under conditions difficult to replicate in the laboratory. The extremely low intensities produced previously have, however, required sensitive instrumentation for detection, preventing applications beyond scientific research. Here we report observations of radio-induced optical emissions bright enough to be seen by the naked eye, and produced not in the quiet mid-latitude ionosphere, but in the midst of a pulsating natural aurora. This may open the door to visual applications of ionospheric heating technology or provide a way to probe the dynamics of the natural aurora and magnetosphere. PMID:15690034

Pedersen, Todd R; Gerken, Elizabeth A

2005-02-01

191

Peculiarities of long-wave radio bursts from solar flares preceding strong geomagnetic storms  

NASA Astrophysics Data System (ADS)

Radio bursts in the frequency range of 100-1500 kHz, recorded in 1997-2000 on the INTERBALL-1 satellite during the solar flares preceding the strong geomagnetic storms with D st < -100 nT, are analyzed in this paper. The observed long-wave III-type radio bursts of solar origin at frequencies of 1460 and 780 kHz were characterized by large values of the flux S f = 10-15 -10-17 W/m2 Hz and duration longer than 10 min. The rapid frequency drift of a modulated radio burst continued up to a frequency of 250 kHz, which testified that the exciting agent (a beam of energetic electrons) propagated from the Sun to the Earth. All such flares were characterized by the appearance of halo coronal mass ejections, observed by the LASCO/ SOHO, and by the presence of a southward Bz-component of the IMF, measured on the ACE and WIND spacecraft. In addition, shortly after radio bursts, the INTERBALL-1 satellite has recorded the fluxes of energetic electrons with E > 40 keV.

Prokudina, V. S.; Kuril'Chik, V. N.; Yermolaev, Yu. I.; Kudela, K.; Slivka, M.

2009-02-01

192

Beat-type Langmuir wave emissions associated with a type III solar radio burst: Evidence of parametric decay  

NASA Technical Reports Server (NTRS)

Recent measurements from the plasma wave instrument on the Galileo spacecraft have shown that Langmuir waves observed in conjunction with a type III solar radio burst contain many beat-type waveforms, with beat frequencies ranging from about 150 to 650 Hz. Strong evidence exists that the beat pattern is produced by two closely spaced narrowband components. The most likely candidates for these two waves are a beam-generated Langmuir wave and an oppositely propagating Langmuir wave produced by parametric decay. In the parametric decay process, nonlinear interactions cause the beam-driven Langmuir wave to decay into a Langmuir wave and a low-frequency ion sound wave. Comparisons of the observed beat frequency are in good agreement with theoretical predictions for a three-wave parametric decay process. Weak low-frequency emissions are also sometimes observed at the predicted frequency of the ion sound wave.

Hospodarsky, G. B.; Gurnett, D. A.

1995-01-01

193

The role of the atmosphere in satellite geodesy, radio astronomy and other applications of trans-atmospheric propagation of radio waves  

Microsoft Academic Search

The influence of the atmosphere on radio waves relevant to technological applications is investigated theoretically, and the associated errors are classified and defined. Range errors are defined as the length of the phase path minus the geometric distance, and range errors are divided into those related to the troposphere and those related to the ionosphere. Ground-path error and group delay

R. Leitinger

1990-01-01

194

GPS scintillation effects associated with polar cap patches, auroral arcs and blobs in European Arctic sector  

NASA Astrophysics Data System (ADS)

Both polar cap patches and auroral arcs are associated with irregularities that can affect the propagation of radio waves and thus disrupt the navigation system in the high latitudes. But which is the worst case remains unanswered. This study focuses on the direct comparison of the relative scintillation effects associated with different phenomena in high latitudes. The All Sky Camera located at Ny-Alesund, Svalbard observed six polar cap patches on January 13, 2013. The patches exited into the nightside auroral region in response to the ongoing substorms and then they are termed blobs. The collocated GPS scintillation monitor is used to study the scintillations produced by these different phenomena which are frequently observed at high latitudes. The amplitude scintillation index (S_4) was very low during this period, while the phase scintillation index (sigma_phi) indicated a disturbed ionospheric condition but responded differently to these three types of phenomena. Comparisons of the associated scintillation effects indicate that the blobs are the most violent scintillation source. Moreover, polar cap patches produce scintillation more effectively than auroral arcs do. Five of the six polar cap patches were observed to produce significant scintillations either on the edges or on the center of the patches, which imply most of the polar cap patches are associated with strong small scale irregularities. All of the scintillations produced by the pure auroral arcs were below 0.2 rad in this period. This study highlights the compound effects of the particle precipitations (auroral arcs) and high density plasma islands (patches) in developing the small scale irregularities. From the space weather forecasting perspective, particular attention is to be paid to polar cap patches exiting the polar cap at night in the European sector.

Jin, Yaqi; Moen, Jøran; Miloch, Wojciech

2014-05-01

195

Multi-spacecraft Observations of type III radio bursts and their associated Langmuir waves  

NASA Astrophysics Data System (ADS)

The radio signatures of flare accelerated electron beams in the corona and interplanetary medium are the fast drifting emission features called type III radio bursts. The production of these bursts involves the generation of high levels of Langmuir waves excited by the flare accelerated electron beams propagating along open field lines, and their subsequent conver-sion into electromagnetic radiation at the fundamental and second harmonic of the electron plasma frequency. Although the emission mechanism, namely, the plasma mechanism predicts that these bursts should be very directive and should be visible only along specific directions, they are observed over a wide range of angles. The outstanding question is what causes the wide-spread visibility of these bursts, is it due to propagation effects, such as the scattering by random density fluctuations or due to different electron beams propagating along different diverging magnetic field lines. The twin spacecraft of the STEREO mission and the WIND spacecraft separated from each other over a wide range of angles are providing excellent si-multaneous observations of type III radio bursts as well as high time resolution observations of associated Langmuir waves. We present the analysis of these observations and show that the type III associated Langmuir waves are detected simultaneously by two or more spacecraft only when they are separated from each other by very narrow angles and probably the wide spread visibility is due to scattering by density fluctuations. By using statistical ray tracing of a distribution of rays, we show that the mode of emission of the widely visible type III bursts is most probably the second harmonic of the electron plasma frequency.

Golla, Thejappa; MacDowall, Robert

196

Radio Wave Propagation for Communication on and around Mars. Part 1; Highlights: Propagation Through Mars Environment  

NASA Technical Reports Server (NTRS)

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.

Ho, Christian; Golshan, Nasser

1999-01-01

197

The effect of solar-flare X-rays on radio-wave propagation  

NASA Astrophysics Data System (ADS)

Model calculations of variations of ionospheric electron density profiles in relation to variations of the solar X-ray spectrum are analyzed. It is shown that the season, the time of day, the geographic latitude, and the solar-flare spectrum all have an effect on the type of field-strength variations of long-wave radio signals, determined by variations of electron density profile. The strength of each of these factors is determined by the magnitude of the difference between the actual vertical profile of electron density and the summer midday level.

Turkeeva, B. A.

198

Wave mode conversion and mode transition in very high radio frequency helicon plasma  

SciTech Connect

In a very high radio frequency helicon plasma, experimental evidences for a wave mode conversion between the helicon mode and the Trivelpiece-Gould mode (TG mode) are presented. The helicon mode generation was detected when {omega}<{omega}{sub ce}/2 was satisfied, and the helicon mode was converted to the TG mode at the plasma periphery below 140 G. As no more mode conversion to the TG mode occurs above 140 G, the plasma was directly heated by the helicon mode and a subsequent abrupt mode transition occurred.

Eom, G. S.; Kim, Junghee; Choe, W. [Department of Physics, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)

2006-07-15

199

Radio Astronomy  

NSDL National Science Digital Library

This article is a Why Files short piece on how astronomers use information from radio astronomy. Contrary to popular belief, large radio telescopes are not looking for signs of life outside our solar system, but are making images of black holes, centers of galaxies, and gamma ray bursts. These phenomena cannot be seen in visible light, but emit radio waves which can be translated into images. The article discusses how this process works, and the information gathered from radio waves.

Tenenbaum, David

200

Waveguide radio-wave propagation in the equatorial ionosphere according to the Interkosmos-19 data  

NASA Astrophysics Data System (ADS)

Additional strongly remote (up to 2000 km) radio-signal reflection traces on Intercosmos-19 ionograms obtained in the equatorial ionosphere have been considered. These traces, as a rule, begin at frequencies slightly lower than the main trace cutoff frequencies, which indicates that an irregularity with a decreased plasma density exists here. The waveguide stretched along the magnetic-field line is such an inhomogeneity in the equatorial ionosphere. The ray tracing confirm that radio waves propagate in a waveguide and make it possible to determine the typical waveguide parameters: -? N e ? 10%, with a diameter of 15-20 km. Since the waveguide walls are smooth, an additional trace is always recorded distinctly even in the case in which main traces were completely eroded by strong diffusivity. Only one additional trace (of the radio signal X mode) is usually observed one more multiple trace is rarely recorded. Waveguides can be observed at all altitudes of the equatorial ionosphere at geomagnetic latitudes of ±40°. The formation of waveguides is usually related to the formation of different-scale irregularities in the nighttime equatorial ionosphere, which result in the appearance of other additional traces and spread F.

Karpachev, A. T.; Zhbankov, G. A.; Telegin, V. A.

2014-03-01

201

A millimeter-wave full-duplex fiber-radio star-tree architecture incorporating WDM and SCM  

Microsoft Academic Search

We propose a full-duplex millimeter-wave fiber-radio network for providing wireless customer access to broadband services. It consists of a hybrid star-tree architecture connecting remote antenna base stations to a central control office (CO) by incorporating wavelength-division multiplexing (WDM) of the optical signals and subcarrier multiplexing (SCM) of the radio signals. These multiplexing schemes allow the sharing of equipment at the

G. H. Smith; D. Novak; C. Lim

1998-01-01

202

Detection of layering in the upper cloud layer of Venus northern polar atmosphere observed from radio occultation data  

NASA Astrophysics Data System (ADS)

Observations of radio wave scintillations represent an important tool for measuring of small-scale irregularities in the atmosphere of Venus. Prominent features of enhanced scintillation located in the 60-km region were observed in Mariners 5 and 10, Venera 9, and Pioneer Venus occultations. It is possible that the enhanced scintillations are due to the random turbulence in the upper region which is caused by trapped small-scale gravity waves. However, other interpretations are possible. Thin stable layers, which are commonly observed in the Earth stratosphere under cloud-free conditions, could also contribute to scattering in the Venus stratosphere. If scintillations observed in different occultations are correlated, then these scintillations may be attributed to the persistent layers. Cross correlations of 32-cm radio wave amplitude fluctuations have been determined for seven radio occultation measurements of Venus's northern polar atmosphere using Venera 15 and 16. Significant cross correlations were found between 59.0 and 61.5 km in four different radio occultations. Layering is revealed in the upper layer of the Venus clouds at altitudes of 59.0-61.5 km, which is specified by enhanced turbulence of the atmosphere. It is found that the lifetime of the small-scale layered irregularities is 2 d or more and that their horizontal extension in the meridional direction can exceed 180 km. A possible cause of emergence of the layered structures inside the upper layer of polar clouds of Venus is discussed.

Gubenko, Vladimir N.; Andreev, Vitali E.; Pavelyev, Alexander G.

203

Hydromagnetic wave heating of low density interstellar gas  

NASA Technical Reports Server (NTRS)

The origin of the observed wave spectrum for hot gas in the ISM is considered theoretically. The governing equations for the generation, propagation, and dissipation of compressive waves are reviewed, and particular attention is given to the heating of warm neutral gas and the implications for radio-wave scattering. It is shown that little power from interactions between SN shocks and hot coronal gas reaches short wavelengths, and that scintillation probably does not originate in a warm weakly ionized gas.

Zweibel, Ellen G.; Ferriere, Katia M.; Shull, J. Michael

1988-01-01

204

An equatorial scintillation model  

NASA Astrophysics Data System (ADS)

Radiowave scintillation in the presence of natural and/or high altitude nuclear disturbances has the potential to disrupt numerous transionospheric radio and radar systems. This report develops a model characterizing the plasma density irregularities that produce scintillation in the naturally disturbed equatorial F layer. The model has been incorporated into Program WBMOD along with subroutines for computing both link geometry and scintillation indices, the latter by means of phase screen diffraction theory. The model is based on similarly extensive analysis of Wideband data from two equatorial stations. It describes irregularities at an effective height of 350 km that are isotropic across the geomagnetic field and elongated by a factor of 50 along the field and whose one dimensional spatial power spectrum obeys a single regime power law with a (negative) spectral index of 1.5. The height-integrated spectral strength of the irregularities is modeled as a function of solar epoch (sunspot number), the angle between the sunset terminator and the geomagnetic field line through the equatorial F layer point in question (a measure of seasonal and longitudinal variation), time after E-layer sunset on that field line, and the F-layer magnetic apex latitude of the point. The report also highlights a factor missing from complete characterization of the joint seasonal/longitudinal variation of scintillation, thought to depend upon thermospheric neutral winds.

Fremouw, E. J.; Robins, R. E.

1985-09-01

205

Form and energy of the shock waves from the solar flares of August 2, 4, and 7, 1972  

Microsoft Academic Search

The shape of the shock waves associated with the August 1972 solar flares was determined by comparing the plasma measurement data from the Prognoz, Prognoz 2, Pioneer 9, and Pioneer 10 space probes with observations of radio source scintillations and comet brightness. A nearly spherical shock wave form was obtained for two flares on August 2, and essentially nonspherical shock

G. N. Zastenker; V. V. Temny; C. dUston; J. M. Bosqued

1978-01-01

206

On the merging of millimeter-wave fiber-radio backbone with 25GHz WDM ring networks  

Microsoft Academic Search

We present an optical modulation and distribution scheme that incorporates subcarrier-multiplexed (SCM) transport with remote local oscillator (LO) delivery for a millimeter-wave (mm-wave) fiber-radio backbone driving a sectorized antenna interface. The proposed method is compatible with a standard wavelength-division multiplexing infrastructure with a 25-GHz channel spacing. We also characterize the profiles and bandwidths of the optical filters, which are essential

Christina Lim; Ampalavanapillai Nirmalathas; Manik Attygalle; Dalma Novak; Rod Waterhouse

2003-01-01

207

Variations in the parameters of scattered signals and the ionosphere connected with plasma modification by high-power radio waves  

Microsoft Academic Search

We describe the results of using the incoherent scatter technique to observe time-altitude variations in regular parameters\\u000a of the ionospheric plasma and wave disturbances, which accompanied periodic modification of the near-Earth plasma by radio\\u000a waves emitted by the “Sura” facility. A distinctive feature of the experiments was that the processes in the ionosphere were\\u000a diagnosed at a distance of about

V. P. Burmaka; I. F. Domnin; V. P. Uryadov; L. F. Chernogor

2009-01-01

208

The Long Wavelength Array (LWA) and Interplanetary Scintillation (IPS)  

E-print Network

The Long Wavelength Array (LWA) and Interplanetary Scintillation (IPS) Patrick C. Crane 12 January scintillation (IPS) is the random fluctuation in the intensity and phase of electromagnetic waves passing

Ellingson, Steven W.

209

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

SciTech Connect

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 cutoff 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.

Zhao, G. Q.; Chen, L.; Wu, D. J. [Purple Mountain Observatory, CAS, Nanjing 210008 (China); Yan, Y. H., E-mail: djwu@pmo.ac.cn [Key Laboratory of Solar Activity, National Astronomical Observatories, CAS, Beijing 100012 (China)

2013-06-10

210

ASSESSMENT OF THE IMMUNE RESPONSIVENESS OF MICE IRRADIATED WITH CONTINUOUS WAVE OR PULSE-MODULATED 425-MHZ RADIO FREQUENCY RADIATION  

EPA Science Inventory

Groups of female BALB/C mice were irradiated with 425-MHz radio frequency (RF) radiation either continuous wave (CW) or pulse modulated (PM, 1-ms pulse width, 250 pulses/s). Mice were irradiated in a rectangular strip-transmission line at average forward powers of 78, 17.7, or 5 ...

211

Long-term integrated radiophysical studies of the ionosphere, near space, and the propagation of radio waves from space objects  

NASA Technical Reports Server (NTRS)

The radiophysical studies reported consist of direct measurements of certain effects induced in the propagation of radio waves from space objects. From measured effects and from data on the motion and position of space objects, physical parameters of the medium and bodies are determined.

Misyura, V. A.

1974-01-01

212

Generation of low-frequency electromagnetic oscillations by the field of a powerful radio wave in the ionosphere  

Microsoft Academic Search

The problem of the generation of long-peried geomagnetic variations in the field of a modulated radio wave is examined in detail. It is shown that the maximum effect is achieved through the disruption of the ionization-recom bination balance of the ionospheric plasma. Calculations are made for two models of the ionosphere: day and night. It is found that at a

L. S. Al'perovich; E. N. Fedorov

1981-01-01

213

Spatial separation of mixed states of atoms and molecules in the field of a traveling radio wave  

Microsoft Academic Search

The effects of a propagating RF field on populations of atoms or molecules in a gaseous medium are investigated theoretically. The macroscopic transverse magnetic flux observed by Agap'ev and Matisov (1986) is found to be the result of the spatial transfer of coherence in the direction of radio-wave propagation, demonstrating the feasibility of separating an incoherent mixture of quantum states

B. D. Agapev; B. G. Matisov

1986-01-01

214

Long-term statistics related to evaporation duct propagation of 2 GHz radio waves in the English Channel  

Microsoft Academic Search

This paper presents long-term statistics additional to those previously published pertaining to evaporation duct propagation of UHF radio waves in the British Channel Islands, with particular focus on a completely over-sea 50 km transhorizon path. The importance of the evaporation duct as an anomalous propagation mechanism in marine and coastal regions is highlighted. In particular, the influence of various atmospheric

S. D. Gunashekar; E. M. Warrington; D. R. Siddle

2010-01-01

215

Investigation of ionospheric irregularities and scintillation using TEC at high latitude  

NASA Astrophysics Data System (ADS)

The occurrence of ionospheric irregularities at high latitudes, with dimensions of several kms down to decameter scale size shows strong correlation with geomagnetic disturbance, season and solar activity. Transionospheric radio waves propagating through these irregularities experience rapid random fluctuations in phase and/or amplitude of the signal at the receiver, termed scintillation, which can degrade GNSS services. Thus, investigation and prediction of this scintillation effect is very important. To investigate such scintillation effects, a GISTM (GPS Ionospheric Scintillation and TEC Monitoring) NovAtel dual frequency (L1/L2) GPS receiver has been installed at Trondheim, Norway (63.41° N, 10.4° E), capable of collecting scintillation indices at a 1 min rate as well as the raw data (phase and intensity) of the satellite signals at a 50 Hz sampling rate and TEC (Total Electron Content) at a 1 Hz rate. Many researchers have reported that both phase and amplitude scintillation is closely associated with TEC fluctuations or associated with a significant developing enhancement or depletion in the TEC. In this study, a novel analogous phase index is developed which provides samples at a 1 min rate. Generally the scintillation indices can help in estimating the irregularity scintillation effect at a one minute rate, but such procedures are time consuming if DFTs of the phase and/or amplitude at a 50 Hz data are required. In this study, instead, this analogous phase index is estimated from 1 Hz rate TEC values obtained from the raw signals and is then compared for weak, moderate and strong scintillation at Trondheim for one year of data collected from the installed GPS receiver. The spectral index of the irregularities (that is the inverse power law of their spatial spectrum) is determined from the resultant phase scintillation psd. The correlations of the scintillation indices and spectral indices with the analogous phase index have been investigated under different geomagnetic conditions (represented by the Kp index) and an approximate linear correlation of phase scintillation with the analogous phase index was found. Then a principal advantage of this index is that it achieves this correlation without requiring a high sampling data rate and the need for DFTs. Thus, the index seems a good candidate for developing a simple means of ionospheric scintillation prediction which could also be utilized in the development of alerts using regional mappings.

Tiwari, R.; Strangeways, H. J.; Tiwari, S.; Ahmed, A.

2013-09-01

216

Investigation of Total Absorption of Radio Waves in High Latitude Ionosphere  

NASA Astrophysics Data System (ADS)

Using the digisonde data observed at ionospheric station Norilsk (Dip lat. 60°N) in 2006, a statistical study on the characteristics of the ionospheric plasma total absorption of radio waves (IPTAR) was performed. In the winter and some months of equinox, the IPTAR mainly occurred in the nighttime and the highest occurrence rate could be up to 90%. In the summer, the occurrence was relatively low and the differences between nighttime and daytime occurrence reduced. The total duration of IPTAR seemed longer around the winter than that around the summer. The occurrence of IPTAR events ascended as the Kp index increased. The frequent precipitation of energetic particles into the ionospheric plasma in the auroral belt may be the main cause of the IPTAR events.

Shi, Jiankui; Wang, Zheng; Tao, Wei; A. Zherebtsov, G.; B. Romanova, E.; G. Ratovsky, K.

2014-09-01

217

Investigating raindrop shapes, oscillation modes, and implications for radio wave propagation  

NASA Astrophysics Data System (ADS)

of raindrop shapes, oscillation modes, and implications for radio wave propagation are presented. Drop shape measurements in natural rain using 2-D video disdrometers (2DVDs) are discussed. As a representative exception to vast majority of the cases where the "most probable" shapes conform to the axisymmetric (2,0) oscillation mode, an event with a highly organized line convection embedded within a larger rain system is studied. Measurements using two collocated 2DVD instruments and a C-band polarimetric radar clearly show the occurrence of mixed-mode drop oscillations within the line, which in turn is attributed to sustained drop collisions. Moreover, the fraction of asymmetric drops determined from the 2DVD camera data increases with the calculated collision probability when examined as time series. Recent wind-tunnel experiments of drop collisions are also discussed. They show mixed-mode oscillations, with (2,1) and (2,2) modes dramatically increasing in oscillation amplitudes, in addition to the (2,0) mode, immediately upon collision. The damping time constant of the perturbation caused by the collision is comparable to the inverse of the collision frequency within the line convection. Scattering calculations using an advanced method of moments numerical technique are performed to accurately and efficiently determine the pertinent parameters of electrically large oscillating raindrops with asymmetric shapes needed for radio wave propagation. The simulations show that the scattering matrix and differential reflectivity of drops are dependent on the particular oscillation modes and different time instants within the oscillation cycle. The technique can be utilized in conjunction with 3-D reconstruction of drop shapes from 2DVD data.

Thurai, M.; Bringi, V. N.; Mani?, A. B.; Å ekelji?, N. J.; Notaroš, B. M.

2014-10-01

218

Developments in photonic and mm-wave component technology for fiber radio  

NASA Astrophysics Data System (ADS)

A review of photonic component technology for fiber radio applications at 60 GHz will be given. We will focus on two architectures: (i) baseband-over-fiber and (ii) RF-over-fiber. In the first approach, up-conversion to 60 GHz is performed at the picocell base stations, with data being transported over fiber, while in the second both the data and rum­ wave carrier are transported over fiber. For the baseband-over-fiber scheme, we examine techniques to improve the modulation efficiency of directly­ modulated fiber links. These are based on traveling-wave structures applied to series cascades of lasers. This approach combines the improvement in differential quantum efficiency with the ability to tailor impedance matching as required. In addition, we report on various base station transceiver architectures based on optically-controlled :tvfMIC self­ oscillating mixers, and their application to 60 GHz fiber radio. This approach allows low cost optoelectronic transceivers to be used for the baseband fiber link, whilst minimizing the impact of dispersion. For the RF-over-fiber scheme, we report on schemes for optical generation of 100 GHz. These use modulation of a Mach-Zehnder modulator at V? bias in cascade with a Mach-Zehnder driven by 1.25 Gb/s data. One of the issues in RF-over-fiber is dispersion, while reduced modulation efficiency due to the presence of the optical carrier is also problematic. We examine the use of silicon nitride micro-ring resonators for the production of optical single sideband modulation in order to combat dispersion, and for the reduction of optical carrier power in order to improve link modulation efficiency.

Iezekiel, Stavros

2013-01-01

219

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

NASA Technical Reports Server (NTRS)

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.

Simons, Rainee N.; Wintucky, Edwin G.

2014-01-01

220

A millimeter-wave radio-over-fiber system for overcoming fiber dispersion-induced signal cancellation effect  

NASA Astrophysics Data System (ADS)

Millimeter-wave (mm-wave) radio over fiber (ROF) using dispersive single-mode fiber is susceptible to signal cancellation effect at the output of the uni-travelling carrier photodiode at the base station (BS). The fiber dispersion effect produces different phase shifts of the sidebands of the intensity-modulated lightwave which can produce a cancellation of the output signal when mixed with the optical carrier. In this paper, we propose and analyze a novel scheme of mm-wave ROF which uses microwave modulation at the central station (CS) and frequency upconversion before the BSs. This scheme can overcome fiber dispersion-induced signal cancellation effect.

Chattopadhyay, Taraprasad

2012-07-01

221

The winter anomaly as seen in the propagation of low frequency 40 kHz radio waves  

NASA Astrophysics Data System (ADS)

An analysis of propagation data for LF 40 kHz radio waves shows that the field strength of the sky wave is enhanced during day-time on winter anomaly days (WAD), in striking contrast to the severe attenuation of HF radio waves. This peculiar enhancement of the field strength may be ascribed to an increase in the reflection coefficient. The analysis also demonstrates that the reflection height is lower on WAD, which seems to be associated with enhancements of ionization in the D-region. Moreover, it was found that WAD are characterized by an earlier occurrence in the morning and a delayed occurrence in the evening of pronounced interference maxima and minima, respectively.

Ishimine, T.; Echizenya, Y.

1986-12-01

222

Real-time dual-band wireless videos in millimeter-wave radio-over-fiber system  

NASA Astrophysics Data System (ADS)

A dual-band converged radio-over-fiber (RoF) access system at 60-GHz and 100-GHz millimeter-wave (mm-wave) is proposed. Real-time end-to-end delivery of two channels of independent high-definition (HD) video services simultaneously carried on 60-GHz and 100-GHz radios is demonstrated for the first time. PRBS data transmission with equivalent data rate and format is also tested to characterize the system performance. The analysis of the spectrum from the beating signal indicates the entire 60-GHz band and the W-band can be retrieved without interference. The real-time HD video display and error-free (BER < 10-9) data transmission demonstrate the feasibility of the proposed wireless access system using converged fiber-optic and mm-wave RoF techniques.

Cheng, Lin; Liu, Cheng; Dong, Ze; Wang, Jing; Zhu, Ming; Chang, Gee-Kung

2013-12-01

223

Continous-wave He-Kr+ laser oscillations in a transverse radio-frequency discharge  

NASA Astrophysics Data System (ADS)

A continuous-wave He-Kr+ laser with capacitively coupled transverse radio- frequency excitation is presented for the first time. The laser oscillations were obtained in a simple alumina oxide discharge tube (40 cm active length, 4.9 mm inner diameter) closed in a fused silica tube envelope. The laser discharge tube was filled with a He-Kr mixture at optimum He:Kr ratio 1000:1. The operating gas pressure ranged from 4 kPa to 16 kPa. The rf power was capacitively coupled into the discharge with 40 cm long and 4 mm wide transverse nickel electrodes mounted along the discharge tube. The discharge was maintained by an rf generator operating at 13.56 MHz with an output power up to 400 W. Transformation of the laser discharge tube impedance to the 50 ohms output resistance of the rf source and symmetrization of the rf voltage were performed by a special matching network. Continuous- wave laser oscillations were obtained at 469.4 nm, 438.7 nm, and 431.8 nm lines of Kr+ ion. The laser output powers were 6.2 mW, 0.14 mW, and 1.27 mW, respectively. The laser action at the 438.7 nm line occurred only when the other laser lines were suppressed with a birefringent filter. The rms noise to signal ratio of the laser output power did not exceed 0.8%.

Reich, N.; Mentel, Juergen A.; Jakob, Gerhard; Mizeraczyk, Jerzy

1995-03-01

224

Quasi-Harmonic Faraday-Rotation Fluctuations of Radio Waves When Sounding the Outer Solar Corona  

NASA Astrophysics Data System (ADS)

A statistical analysis of the Faraday-rotation fluctuations (FRFs) of linearly polarized radio signals from the Helios 1 and Helios 2 spacecraft shows that the FRF time power spectra can be of three types. Spectra of the first type are well fitted by a single power law in the range of fluctuation frequencies 1-10 mHz. Spectra of the second type are a superposition of a power law and two quasi-harmonic components with fluctuation frequencies of about nu_1 = 4 mHz (fundamental frequency) and nu_2 = 8 mHz (second harmonic). Spectra of the third type exhibit only one of the two quasi-harmonic components against the background of a power law. The spectral density of the quasi-harmonic components can be represented by a resonance curve with a fairly broad [Delta nu =(0.5-1.3) nu_{1,2}] distribution relative to the nu = nu_{1,2} peak. The intensity of the quasi-harmonic FRF has a radial dependence that roughly matches the radial dependence for the background FRF, while their period at the fundamental frequency is approximately equal to the period of the well-known 5-min oscillations observed in the lower solar atmosphere. The fluctuations with 5-min periods in FRF records can be explained by the presence in the outer corona of isolated trains of Alfven waves generated at the base of the chromosphere-corona transition layer and by acoustic waves coming from deeper layers.

Efimov, A. I.; Samoznaev, L. N.; Andreev, V. E.; Chashei, I. V.; Bird, M. K.

2000-08-01

225

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

PubMed

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. PMID:20867308

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

226

Imaging the Radio Universe  

E-print Network

-rays, and microwaves, etc). · Sound waves are pressure waves. Require a medium (air, water, etc.) to travel through. · Sound is created by a pressure wave moving a membrane in your ear. Your brain turns the vibration of this membrane into "sound". MediumEar Sound Radio Waves are not Sound Waves #12;You do not listen to radio waves

Groppi, Christopher

227

Scintillating Stars  

NSDL National Science Digital Library

Often, a bright planet that is visible over the horizon will be mistaken for a star. Some believe they can tell the difference between a star and a planet because stars twinkle, or scintillate , and planets do not. In actuality however, both will twinkle because any light that passes through our atmosphere, whether it be reflected from a planet or generated by a star, will be interfered with by the atmospheric elements. This month's column sheds light on this "scintillating" subject and engages students in a research activity that revolves around the question: Is Pluto a planet?

Riddle, Bob

2003-02-01

228

Time-resolved photo and radio-luminescence studies demonstrate the possibility of using InGaN/GaN quantum wells as fast scintillators.  

PubMed

In the recent publication by Hospodková et al, the authors investigate III-N quantum well structures as potential fast scintillators (Hospodková et al 2014 Nanotechnology 25 455501). The InGaN/GaN quantum well structures are grown using metal organic vapour phase epitaxy on a sapphire substrate and the fast carrier decay times are characterized by time resolved photo and radioluminescence. PMID:25670071

Balakrishnan, G

2015-03-01

229

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

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

230

High Latitude Scintillation Monitoring at UHF with the COMMX Experiment on TACSat4  

NASA Astrophysics Data System (ADS)

UHF Beacon Transmissions at 253 MHz have provided high latitude scintillation monitoring from Gakona Alaska using the COMMX instrument on TACSat4. TACSat4 was constructed by the Naval Research Laboratory and was launched in September 2011 as an experimental communications satellite. Ground UHF transmissions are uplinked to TACSat4 using the 4 meter diameter antenna deployed to view the earth. These signals are coherently translated to other UHF frequency to be rebroadcast to the ground. Scintillation monitoring is achieved by taking the 401.25 MHz signals from ground DORIS beacons located in Cold Bay, Alaska; Yellowknife, Canada; Kauai, Hawaii; and Soccoro Island, Mexico. These signals are translated to 253 MHz and broadcast with the 4 meter antenna pointed to the UHF receiver located at Gakona, Alaska. The satellite antenna gain is 18 dB in this UHF band and the transmitter power is 2 Watts. The satellite is in an elliptical orbit with an inclination of 63 degrees and a perigee of 12,000 km. Doppler frequency shifts allow separation of each uplink from the ground DORIS beacons. This new scintillation monitoring system has been used to detect natural and artificial field aligned irregularity effects on the amplitude and phase of UHF carriers where typical scintillation amplitudes are 2dB or less. Using the HAARP transmitter in Alaska, TACSat4 was used to discover the artificial ionization clouds produce scintillation with as much as 16 dB and amplitude indices S4 greater than unity. This is the first demonstration of significant effects on radio scintillations using high power HF radio waves to disturb the ionosphere.

Bernhardt, P. A.; Siefring, C. L.; Akins, K.; Nurnberger, M.

2013-12-01

231

Methods for calculating probability distributions of radio-wave attenuation on ground paths due to anomalies of the air refractive index  

NASA Astrophysics Data System (ADS)

The paper analyzes and compares existing methods for calculating radio-wave attenuation statistics at frequencies above 10 GHz associated with anomalies of the air refractive index. An algorithm is proposed for calculating the sum distributions.

Pozhidaev, V. N.; Sviatogor, V. V.

1992-07-01

232

Density fluctuations measured by ISEE 1-2 in the Earth's magnetosheath and the resultant scattering of radio waves  

E-print Network

of radio waves C. Lacombe, J.-L. Steinberg, C. C. Harvey, D. Hubert, A. Mangeney, M. Moncuquet URA 264 dufp source upstream of the Earth's bow shock (Lacombe et al., 1988) and of the outer heliospheric scattering coefficient b2fp 2 to 4 2 10ÿ10 rad2=m in the solar wind at 1 AU (Lacombe et al., 1988). In situ

Paris-Sud XI, Université de

233

Coherent optical processing of UHF radio-wave electronic pulses via collinear acousto-optical interaction in a crystalline cell  

Microsoft Academic Search

An attempt is made to use the phenomenon of colinear acousto-optical interaction in birefringent single crystals for purposes of a coherent optical processing of UHF radio-wave electronic pulses in anti-radar system. The exact and closed analytical model for describing this phenomenon in uniaxial crystalline materials is developed if both the acoustic attenuation and spreading the acoustic beam are allowed for.

Alexandre S. Shcherbakov; Eduardo Tepichin Rodriguez; Mauro Sanchez Sanchez

2003-01-01

234

The Cassini Radio & Plasma Wave Science (RPWS) view of the Enceladus Space Environment  

NASA Astrophysics Data System (ADS)

A physical picture of the interaction between Saturn's magnetosphere and the moon Enceladus space environment is presented based on Radio and Plasma Wave Science (RPWS) observations. The space environment around Enceladus consists of several different regions with a diversity of active physical processes. Foremost, the southward exhaust plume reveals a cold, dense, conductive and dusty plasma environment where the magnetic field is piled-up. Plasma acceleration processes are active at the plume edges, and constitute an important part of the electrodynamic MHD dynamo, giving rise to Auroral hiss emissions as well as a magnetic footprint pattern in the high-latitude atmosphere of Saturn. The Enceladus wake is filled with negatively charged dust that depletes the region from electrons by water grain attachment. The grains around Enceladus can be picked-up by the magnetospheric co-rotation electric field. The charged water grains then populate the region in Enceladus orbit around Saturn and create the E-ring. Depending on the size of the grains, different grain evolutions occur and different dynamics of the grains are expected. The Enceladus plume as well as the plasma disc surrounding the E-ring constitutes complex natural laboratories for dust-plasma interaction, which has important implications also for the newly discovered Europa plume and associated plasma disk material around Jupiter to be investigated by the ESA JUICE and the NASA Europa Clipper missions. We present a detailed account of the Cassini RPWS observations around Enceladus with associated physical interpretations.

Wahlund, Jan-Erik; Gurnett, Donald; Kurth, William; Andrews, David; Engelhardt, Ilka; Eriksson, Anders; Farrell, William; Holmberg, Mika; Hospodarsky, George; Morooka, Michiko; Sheng-Yi, Ye; Vigren, Erik

2014-05-01

235

Radio-electronic equipment  

NASA Astrophysics Data System (ADS)

The fundamentals of radio electronics are first elaborated, with attention given to the principles of circuits and signals, semiconductor devices, computing techniques, radio transmitters and receivers, and wave propagation. The principles of operation of onboard radio-electronic devices are then described, with emphasis on radio communication systems, radar systems, radio navigation systems, radio control systems, and electronic countermeasures. The maintenance of radio-electronic devices is also discussed.

Boldin, Viktor A.; Gorgonov, Gennadii I.; Konovalov, Viktor D.; Kurilov, N. N.; Levonchuk, V. V.

236

Formation of stationary irregularities in the lower part of the E-region of the high-latitude ionosphere under the effect of high-power radio waves  

Microsoft Academic Search

Nonlinear equations describing the generation of irregularities in the lower part of the high-latitude E-region under the effect of high-power radio waves due to the Joule heating of electrons are derived and studied in the framework of the three-wave approximation. Stationary spectra of short-wave two-stream and long-wave gradient-drift disturbances are obtained. It is shown that the stationary periodic nonlinear structures

A. K. Nekrasov

1992-01-01

237

Generation of Acoustic Gravity Waves by Periodic Radio Transmissions from a High-Power Ionospheric Heater  

NASA Astrophysics Data System (ADS)

The Radiophysical Research Institute (Nizhny Novgorod, Russia) and Kharkiv V. N. Karazin National University (Kharkiv, Ukraine) have studied opportunities for the effective generation of acoustic gravity waves (AGWs) in 3 - 180-min period range. The excitation of such waves was conducted for the last several years using the SURA heating facility (Nizhny Novgorod). The detection of the HF-induced AGWs was carried out in the Radiophysical Observatory located near Kharkiv City at a distance of about 960 km from the SURA. A coherent radar for vertical sounding, an ionosonde, and magnetometer chains were used in our measurements. The main results are the following (see [1-5]): 1. Infrasound oscillation trains with a period of 6 min are detected during periodic SURA heater turn-on and -off. Similar oscillation trains are detected after long time pumping, during periodic transmissions with a period of 20 s, as well as after pumping turn-off. The train recordings begin 28 - 54 min after the heater turn-on or -off, and the train propagation speeds are about 300 - 570 m/s, the value of which is close to the sound speed at upper atmospheric altitudes. The amplitude of the Doppler shift frequency is of 10 - 40 mHz, which fits to the 0.1 - 0.3% electron density disturbances at ionospheric altitudes. The amplitude of the infrasound oscillations depends on the SURA mode of operation and the state of the upper atmosphere and ionosphere. 2. High-power radio transmissions stimulate the generation (or enhancement) of waves at ionospheric altitudes in the range of internal gravity wave periods. The HF-induced waves propagate with speeds of 360 - 460 m/s and produce changes in electron density with amplitudes of 2 - 3%. The generation of such periodic perturbations is more preferable with periods of 10 - 60 minutes. Their features depend significantly on the heater mode of operation. It should be stressed that perturbation intensity increases when a pumping wave frequency approaches the F _{_2} layer critical frequency. High-power periodic radio transmissions are capable of enhancing/damping natural wave perturbations generated by the solar terminator. 3. The study has demonstrated that the generation and propagation of AGWs with periods close to the natural oscillation periods of the atmosphere is possible. The duration of AGW oscillation trains does not dependent on the duration of turn-on/-off trains, but it is determined by changes in the current state of the atmosphere-ionosphere-magnetosphere system in general. The period of the AGW oscillation trains is determined by the period or semi-period of the pumping. It means that the mechanism of AGW generation in this case is distinct from the agreed-upon mechanism developed earlier. The AGWs, whose periods are 5 - 10% greater than the Brunt-Vaisala period, exhibit group velocities less than the speed of sound that is of about 80 - 160 m/s. They induce electron density perturbations of about 1.1 - 1.5%. The AGW generation has the following features. When the effective radiated power (ERP) is 50 MW or less, AGWs are not detected; they are reliably observed when the ERP is equal or larger than about 100 MW. Geomagnetic storms play a dual role in the AGW generation because they: (i) increase amplitudes of AGWs with 4 - 6-min and 8 - 12-min periods and (ii) yet enhance background oscillations. The latter hampers the identification of the HF-induced oscillations. Moderate magnetic storms do not markedly exert an influence on the amplitudes of oscillations with 13 - 17-min periods. 4. The quasi-periodic variations in the horizontal components of the geomagnetic field with 8 - 12-min periods become observable near Kharkiv 35 - 45 min after the beginning of pumping. Their speeds are 355 - 460 m/s, and they form trains 40 - 90 min in duration when the [5-min on, 5-min off] or [10-min on, 10-min off] heater timing is used. The 12 - 18-min period variations become observable 35 - 45 min after the beginning of pumping. Their speeds are 355 - 460 m/s, and they form trains 55 - 90 min in duration when the

Frolov, Vladimir; Chernogor, Leonid; Rozumenko, Victor

238

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

NASA Technical Reports Server (NTRS)

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.

Manning, Robert M.

2008-01-01

239

International Symposium on Millimeter and Submillimeter Wave Radio Astronomy, Granada, Spain, September 11-14, 1984, Proceedings  

NASA Astrophysics Data System (ADS)

Various papers on millimeter and submillimeter wave radio astronomy are presented. The topics discussed include: the Nobeyama 45 m telescope, analysis of the time constants in the thermal model for the UK-NL millimeter wave telescope, new generation CFRP sub-mm telescope, the UA/MPIfR submillimeter telescope, telescope testing by radio holography, millimeter and submillimeter interferometry, the Caltech millimeter wave interferometer, the Nobeyama millimeter-wave interferometer, the IRAM interferometer, the SAO submillimeter telescope array project, at VLBI at 90 GHz. Also addressed are: superconducting and Schottky mixers, Caltech SIS receivers, IRAM SIS receivers, SIS mixer development at NRAO, a 2K closed cycle cryogenerator, phase-locked 65-115 GHz Gunn oscillator, bolometer systems developed at MPIfR, current far-infrared spectrometers, acoustooptical spectrometers, far-infrared heterodyne spectroscopy, spiral arm structure of molecular gas in M51, millimeter-wavelength interferometry of Orion-KL, density structure of molecular cloud cores, star formation in dense cores in nearby dark clouds, and extragalactic hot spots at mm wavelengths.

240

Formation of zebra patterns of solar microwave bursts as a result of propagation of radio waves through the inhomogeneous corona  

NASA Astrophysics Data System (ADS)

The geoefficiency of solar bursts is diagnosed using the dynamic radio emission spectrum. At certain time intervals, the spectrum exhibits nearly parallel narrow-band emission strips termed the zebra pattern. Although there are many hypotheses of its origin, all of them do not take into account changes in the signal parameters upon signal propagation through the solar corona. Our analysis shows that the propagation effects form a dynamic spectrum that contains a zebra pattern. The properties of the modeled spectrum are shown to coincide with the basic properties of the observed spectrum. It is clarified that the spike structure of strips is a natural consequence of the interference of radio waves, and the occurrence of this structure is considered to be evidence in favor of the interference nature of the zebra pattern formation. Consequently, the zebra pattern can be formed not in the radiation source itself, but rather can arise as a result of propagation of radio waves through an inhomogeneous refracting medium of the solar corona.

Yurovsky, Yu. F.

2008-06-01

241

On the radio wave group delay in the solar corona for the case of decameter type III bursts  

NASA Astrophysics Data System (ADS)

The excess time delay of the radio waves during their propagation through inhomogeneous plasma is due to two main reasons: (1) the electromagnetic wave group velocity differs from its vacuum value; (2) the ray path is lengthened by refraction. The group delay of type IIIb-III burst emission is estimated by analyzing observations made with the UTR-2 array (Abranin et al. 1984). Owing to the harmonic origin of the type IIIb-III events it is possible to probe one and the same coronal region at two largely different frequencies. The group delay effect has to be more significant for the fundamental emission (type IIIb burst) than for the second harmonic (type III burst). For the observed type IIIb-III pairs this difference is found smaller than the uncertainties in the data. The group delay time for the fundamental emission in the frequency range 12.5-6.25 MHz does not exceed 1 s and the differential group delay is less than 0.3-0.5 s with a degree of confidence of approximately 70%. Radio wave propagation through the coronal plasma is simulated numerically choosing the scale height of the coronal density which fits the mean frequency drift rate of the observed type IIIb-III bursts. The calculated group delay times are found considerably larger than the observed ones if the mean velocity vs of the burst source is assumed equal to 0.3 c. It is possible to reconcile the experimental and calculated group delay times choosing vs less than or equal to 0.1 c. Another possibility is to assume that the fundamental type III emission is produced by the coalescence of plasma (Langmuir) waves with low frequency waves instead of plasma wave Rayleigh scattering by thermal ions.

Itkina, M. A.; Levin, B. N.; Tsybko, Ya. G.

1993-11-01

242

Theory of the propagation of UHF radio waves in coal mine tunnels  

Microsoft Academic Search

The theoretical study of UHF radio communication in coal mines, with particular reference to the rate of loss of signal strength along a tunnel, and from one tunnel to another around a corner is the concern of this paper. Of prime interest are the nature of the propagation mechanism and the prediction of the radio frequency that propagates with the

ALFRED G. EMSLIE; ROBERT L. LAGACE; PETER F. STRONG

1975-01-01

243

Potential Spacecraft-to-Spacecraft Radio Observations with EJSM: Wave of the Future? (Invited)  

Microsoft Academic Search

Future active radio observations of planetary and satellite atmospheres and surfaces could significantly benefit form the presence of two or more spacecraft in orbit around a target object. Traditionally, radio occultation and bistatic surface scattering experiments have been conducted using a single spacecraft operating in the Downlink (DL) configuration, with the spacecraft transmitting and at least one Earth-based station receiving.

E. A. Marouf; P. Tortora; S. W. Asmar; W. M. Folkner; D. Hinson; L. Iess; I. R. Linscott; R. D. Lorenz; I. C. Mueller-Wodarg

2010-01-01

244

A newsletter for non-scientists (and scientists) interested in MAGIC Radars transmit pulses of radio waves of a given frequency and receive signals that are  

E-print Network

pulses of radio waves of a given frequency and receive signals that are reflected, or scattered, from of the returned signal, the distance to the objects and information about their properties can be determined sizes of raindrops. The Doppler effect pertains to the change in frequency of a wave emitted

245

Measurement of radio wave reflection due to temperature rising from rock salt and ice irradiated by an electron beam for an ultra-high-energy neutrino detector  

SciTech Connect

An ultra-high-energy neutrino (UHE{nu}) gives temperature rise along the hadronic and electromagnetic shower when it enters into rock salt or ice. Permittivities of them arise with respect the temperatures at ionization processes of the UHE{nu} shower. It is expected by Fresnel's formula that radio wave reflects at the irregularity of the permittivity in the medium. We had found the radio wave reflection effect in rock salt. The reflection effect and long attenuation length of radio wave in rock salt and ice would yield a new UHE{nu} detection method. An experiment for ice was performed to study the reflection effect. A coaxial tube was filled with rock salt powder or ice. Open end of the coaxial tube was irradiated by a 2 MeV electron beam. Radio wave of 435 MHz was introduced to the coaxial tube. We measured the reflection wave from the open end. We found the radio wave reflection effect due to electron beam irradiation in ice as well as in rock salt.

Tanikawa, Takahiro; Chiba, Masami; Kamijo, Toshio; Yabuki, Fumiaki; Yasuda, Osamu; Akiyama, Hidetoshi; Chikashige, Yuichi; Kon, Tadashi; Shimizu, Yutaka; Utsumi, Michiaki; Fujii, Masatoshi [Graduate School of Science and Engineering, Tokyo Metropolitan University, 1-1 Minami-Ohsawa, Hachioji-shi, Tokyo 192-0397 (Japan); Faculty of Science and Technology, Seikei University, Musashino-shi, Tokyo 180-8633 (Japan); Department of Applied Science and Energy Engineering, School of Engineering, Tokai University, Hiratsuka-shi, Kanagawa 259-1292 (Japan); School of Medicine, Shimane University, Izumo-shi, Shimane 693-8501 (Japan)

2012-11-12

246

High Time Resolution Observations of Langmuir Waves Associated with Type III Radio Bursts and Implications for Beam Stabilization and Emission Mechanisms  

NASA Astrophysics Data System (ADS)

Type III radio bursts are produced by energetic electron beams accelerated in the solar active regions. As the electron beams propagate out of solar atmosphere, they interact with the ambient plasma, which results in the beam-plasma instability. The growth of this instability leads to intense Langmuir turbulence, which is suspected to be responsible for the stabilization of electron beams, so that they can travel from the inner corona to 1 AU and beyond, as well as for generating the electromagnetic waves at the fundamental and harmonic of the electron plasma frequency, fpe via nonlinear wave-wave interactions. We report the STEREO and WIND observations of local type III radio bursts and associated Langmuir waves generated in the vicinity of the spacecraft. By analyzing the high time resolution observations of Langmuir waves, we attempt to identify the non-linear wave-wave interactions in the source regions of type III radio bursts. We also examine whether the observed Langmuir wave packets satisfy the characteristics of Langmuir Eigen modes and critically examine the role of these Langmuir Eigen modes in the beam stabilization and conversion of Langmuir waves into escaping radiation at the fundamental and harmonic of the electron plasma frequency.

Golla, T.; MacDowall, R. J.

2010-12-01

247

Estimating channel fading statistics based on radio wave propagation predicted with deterministic MRFDPF method  

Microsoft Academic Search

The MR-FDPF (Multi-Resolution Frequency-Domain Partial Flow) method has proved to be an efficient tool for the indoor radio coverage prediction (1). In this paper, a new approach is proposed allowing extracting the fading statistics for indoor radio channels based on the electric field strength predicted with the MR-FDPF method. The performance of the proposed approach is verified both by simulations

Meiling Luo; Dmitry Umansky; Guillaume Villemaud; Marc Lafort; Jean-Marie Gorce

2011-01-01

248

Ceramic-like scintillators  

Microsoft Academic Search

Scintillator bodies comprising fluorescent materials and having high optical translucency with low light absorption and methods of making the scintillator bodies are disclosed. In accordance with one embodiment of the invention, the scintillator bodies are formed by a hot-pressing process. In another embodiment, coldpressing followed by sintering is employed. Another embodiment employs controlled cooling. Another embodiment employs hotforging. The scintillator

D. A. Cusano; F. F. Holub; S. Prochazka

1980-01-01

249

Study of zonal large scale wave structure (LSWS) and equatorial scintillation with low-latitude GRBR network over Southeast Asia and African sectors  

NASA Astrophysics Data System (ADS)

The day-to-day variability of Equatorial Spread-F, when and where the equatorial plasma bubbles (EPBs) may initiate, were the challenging problems that puzzling the space weather researchers for several decades. The zonal large scale wave structure (LSWS) at the base of F-layer is the earliest manifestation of seed perturbation for the evolution of EPBs by R-T instability processes, hence, found to play deterministic role on the development of ESF. Yet, only a little is known about LSWS with lack of sufficient observations, primarily because of inability to detect the LSWS with the currently existing instruments except with steerable incoherent scatter radar such as ALTAIR radar. This situation, however, was recently changed with launch of C/NOFS in a unique low-inclination (13 ^{o}) orbit. With the availability of CERTO beacon transmissions from C/NOFS in a near equatorial orbit, it is now possible to detect and resolve the roles by LSWS on a regular basis. A ground based low-latitude GNU Radio Beacon Receiver (GRBR) Network has been recently established that provide coverage of Southeast Asia, Pacific and African low-latitude regions. Recent observations suggest that these wave structures with zonal wave lengths varying between 200 and 800 km can be earliest detected even before E-region sunset and found to grow significantly after sunset, probably, aided by the polarization electric fields. Further, these zonal structures consistently found to be aligned with field lines for several hundreds of kilometers and EPBs were found to grow from the westward walls of upwellings. The characteristic differences on the strength of LSWS between the Asian and African longitudes were identified during the recent increasing solar activity and discussed in this paper.

Ram Sudarsanam, Tulasi; Yamamoto, Mamoru; Gurubaran, Subramanian; Tsunoda, Roland

2012-07-01

250

Results of Experimental and Theoretical Studies of the Atmospheric Turbulence, Internal Gravity Waves and Sporadic-E Layers by Resonant Scattering of Radio Waves on Artificial Periodic Irregularities  

NASA Astrophysics Data System (ADS)

Artificial periodic irregularities (API) formed by the powerful standing radio waves in the ionospheric plasma give the good chance for the lower ionosphere comprehensive studies. In this paper we present some applications of the API technique for experimental studies of sporadic E-layers (E _{s}), internal gravity waves and turbulent events in the lower ionosphere. API are formed in the field of the standing radio wave produced by interference of the incident wave and reflected one from the ionosphere (in more details about the API technique one can see in the book Belikovich et al., Ionospheric Research by Means of Artificial Periodic Irregularities - Katlenburg-Lindau, Germany. 2002. Copernicus GmbH. ISBN 3-936586-03-9). The spatial period of the irregular structure is equal to the standing wavelength Lambda or one-half the powerful wavelength lambda/2. API diagnostics are carried out at the API relaxation or decay stage by their sounding of probing radio pulses. Based on the measurement of an amplitude and a phase of the API scattered signal their relaxation time and regular vertical plasma velocity are measured. In the E-region of the ionosphere API are formed as a result of the diffusion redistribution of the non-uniformly heated plasma. The relaxation of the periodic structure is specified by the ambipolar diffusion process. The diffusion time is tau=(K (2) D _{a}) (-1) where K=2pi/Lambda and D _{a} is the ambipolar diffusion rate. The atmospheric turbulence causes reduction of the API relaxation time in comparison the diffusion time. Determination of the turbulent velocity is based on this fact. The vertical plasma velocity is determined by measuring the phase of the scattered signal. Atmospheric waves having the periods from 5-10 minutes to 5-6 hours give the contribution to temporal variations of the velocity. Parameters and effects of atmospheric waves and the turbulence on the API relaxation process are presented. Determination of the masses of the predominant metallic ions at the E _{s}-layer height is one of the API applications (Bakhmetieva N.V. and Belikovich V.V. Radiophys. Quantum Electron., 2008, Vol. 51, No 11, pp. 956-969). It is based on the observed fact of the local maximum of the API relaxation time at the sporadic E-layer location. The long-lived metallic ions cause the growth of the API relaxation time tau? at the E _{s}-layer height. It is shown by API technique the sporadic E-layers contain Mg (+) , Ca (+) and Fe (+) ions predominantly at heights of 95-110 km. The new applications are based on the so-called two-frequency method of the API creation and their diagnostics. The method allows one to define the neutral atmosphere and the ionosphere parameters with high accuracy. The main results of the lower ionosphere studies carried out in 2006-2012 by the API technique using the SURA heating facility (56,1 N; 46,15 E) are presented and discussed. We aslo discuss the studies of the HF pumping effects on the formation and parameters of the sporadic E-layers and the modification of the semitransparent E _{s}-layer by the powerful radio wave and diagnostics by the API technique. The work was supported by Russian Foundation for Basic Research under project No 13-02-97067, 13-02-12074 and 13-05-00511.

Bakhmetieva, Nataliya V.; Grigoriev; Tolmacheva, Ariadna V.

251

Analysis of strong ionospheric scintillation events measured by means of GPS signals at low latitudes during disturbed conditions  

NASA Astrophysics Data System (ADS)

Drifting structures characterized by inhomogeneities in the spatial electron density distribution at ionospheric heights cause the scintillation of radio waves propagating through. The fractional electron density fluctuations and the corresponding scintillation levels may reach extreme values at low latitudes during high solar activity. Different levels of scintillation were observed on experimental data collected in the Asian sector at low latitudes by means of a GPS dual frequency receiver under moderate solar activity (2005). The GPS receiver used in these campaigns was particularly modified in firmware in order to record power estimates on the C/A code as well as on the carriers L1 and L2. Strong scintillation activity was recorded in the post-sunset period (saturatingS4 and SI as high as 20 dB). Spectral modifications and broadening was observed during high levels of scintillation possibly indicating refractive scattering taking place instead of diffractive scattering. A possible interpretation of those events was attempted on the basis of the refractive scattering theory developed by Uscinski (1968) and Booker and MajidiAhi (1981).

Forte, B.

2012-08-01

252

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

NASA Astrophysics Data System (ADS)

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.

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

253

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

PubMed Central

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

TSUDA, Toshitaka

2014-01-01

254

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

PubMed

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

Tsuda, Toshitaka

2014-01-01

255

Prospects for GMRT to Observe Radio Waves from UHE Particles Interacting with the Moon  

E-print Network

Ultra high energy (UHE) particles of cosmic origin impact the lunar regolith and produce radio signals through Askaryan effect, signals that can be detected by Earth based radio telescopes. We calculate the expected sensitivity for observation of such events at the Giant Metrewave Radio Telescope (GMRT), both for UHE cosmic rays (CR) and UHE neutrino interactions. We find that for 30 days of observation time a significant number of detectable events is expected above $10^{20}$ eV for UHECR or neutrino fluxes close to the current limits. Null detection over a period of 30 days will lower the experimental bounds on UHE particle fluxes by magnitudes competitive to both present and future experiments at the very highest energies.

Sukanta Panda; Subhendra Mohanty; Padmanabhan Janardhan; Oscar Stål

2007-08-13

256

Decameter-wave radio observations of Jupiter during the 1977 apparition  

NASA Technical Reports Server (NTRS)

A catalog of observations of Jupiter's sporadic decameter wavelength radio emissions obtained with the Goddard Space Flight Center Jupiter Monitor Network between June 1977 and May 1978 is presented. Data were collected using the Goddard Space Flight Center station in Greenbelt, MD. and at facilities installed at Orroral Valley (Canberra), Australia and the Nancay Radio Observatory in France. Observations were obtained daily at frequencies of 16.7 and 22.2 MHz using five-element Yagi antennas at each end of a two-element interferometer. Plots of the two dimensional emission occurrence probability distribution are given.

Alexander, J. K.; Kaiser, M. L.; Thieman, J. R.; Vaughan, S. S.

1978-01-01

257

Space-Borne Radio-Sounding Investigations Facilitated by the Virtual Wave Observatory (VWO)  

NASA Technical Reports Server (NTRS)

The goal of the Virtual Wave Observatory (VWO) is to provide userfriendly access to heliophysics wave data. While the VWO initially emphasized the vast quantity of wave data obtained from passive receivers, the VWO infrastructure can also be used to access active sounder data sets. Here we use examples from some half-million Alouette-2, ISIS-1, and ISIS-2 digital topside-sounder ionograms to demonstrate the desirability of such access to the actual ionograms for investigations of both natural and sounder-stimulated plasma-wave phenomena. By this demonstration, we wish to encourage investigators to make other valuable space-borne sounder data sets accessible via the VWO.

Benson, Robert F.; Fung, Shing F.; Bilitza,Dieter; Garcia, Leonard N.; Shao, Xi; Galkin, Ivan A.

2011-01-01

258

The standing wave phenomenon in radio telescopes. Frequency modulation of the WSRT primary beam  

Microsoft Academic Search

Context: Inadequacies in the knowledge of the primary beam response of current interferometric arrays often form a limitation to the image fidelity, particularly when ``mosaicing'' over multiple telescope pointings. Aims: We hope to overcome these limitations by constructing a frequency-resolved, full-polarization empirical model for the primary beam of the Westerbork Synthesis Radio Telescope (WSRT). Methods: Holographic observations, sampling angular scales

Attila Popping; Robert Braun

2008-01-01

259

Revealing the Hidden Wave: Using the Very Small Radio Telescope to Teach High School Physics  

ERIC Educational Resources Information Center

Scientists and teachers have worked together to produce teaching materials for the Very Small Radio Telescope (VSRT), an easy-to-use, low-cost apparatus that can be used in multiple laboratory experiments in high school and university physics and astronomy classes. In this article, we describe the motivation for the VSRT and several of the…

Doherty, Michael; Fish, Vincent L.; Needles, Madeleine

2011-01-01

260

The First Wave: The Beginnings of Radio in Canadian Distance Education  

ERIC Educational Resources Information Center

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,…

Buck, George H.

2006-01-01

261

Radio-wave propagation for emerging wireless personal-communication systems  

Microsoft Academic Search

The present survey paper summarizes radio-propagation measurements and models for emerging wireless personal-communication systems. Both indoor and microcell-propagation environments are considered, and the problem of RF penetration into buildings is identified as an important area of research for emerging wireless-communication systems

Theodore S. Rappaport; S. Sandhu

1994-01-01

262

The Coherer: With Simple Demonstrations of the Generation, Propagation and Detection of Radio Waves  

ERIC Educational Resources Information Center

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…

Mills, Allan

2010-01-01

263

Measurement of a phase of a radio wave reflected from rock salt and ice irradiated by an electron beam for detection of ultra-high-energy neutrinos  

NASA Astrophysics Data System (ADS)

We have found a radio-wave-reflection effect in rock salt for the detection of ultra-high energy neutrinos (UHE?'s) which are expected to be generated in Greisen, Zatsepin, and Kuzmin (GZK) processes in the universe. When an UHE? interacts with rock salt or ice as a detection medium, a shower is generated. That shower is formed by hadronic and electromagnetic avalanche processes. The energy of the UHE? shower converts to thermal energy through ionization processes. Consequently, the temperature rises along the shower produced by the UHE?. The refractive index of the medium rises with temperature. The irregularity of the refractive index in the medium leads to a reflection of radio waves. This reflection effect combined with the long attenuation length of radio waves in rock salt and ice would yield a new method to detect UHE?'s. We measured the phase of the reflected radio wave under irradiation with an electron beam on ice and rock salt powder. The measured phase showed excellent consistence with the power reflection fraction which was measured directly. A model taking into account the temperature change explained the phase and the amplitude of the reflected wave. Therefore the reflection mechanism was confirmed. The power reflection fraction was compared with that calculated with the Fresnel equations, the ratio between the measured result and that obtained with the Fresnel equations in ice was larger than that of rock salt.

Chiba, Masami; Kamijo, Toshio; Tanikawa, Takahiro; Yano, Hiroyuki; Yabuki, Fumiaki; Yasuda, Osamu; Chikashige, Yuichi; Kon, Tadashi; Shimizu, Yutaka; Watanabe, Souichirou; Utsumi, Michiaki; Fujii, Masatoshi

2013-05-01

264

Dynamic of Langmuir and Ion-Sound Waves in Type 3 Solar Radio Sources  

NASA Technical Reports Server (NTRS)

The evolution of Langmuir and ion-sound waves in type 3 sources is investigated, incorporating linear growth, linear damping, and nonlinear electrostatic decay. Improved estimates are obtained for the wavenumber range of growing waves and the nonlinear coupling coefficient for the decay process. The resulting prediction for the electrostatic decay threshold is consistent with the observed high-field cutoff in the Langmuir field distribution. It is shown that the conditions in the solar wind do not allow a steady state to be attained; rather, bursty linear and nonlinear interactions take place, consistent with the highly inhomogeneous and impulsive waves actually observed. Nonlinear growth is found to be fast enough to saturate the growth of the parent Langmuir waves in the available interaction time. The resulting levels of product Langmuir and ion-sound waves are estimated theoretically and shown to be consistent with in situ ISEE 3 observations of type 3 events at 1 AU. Nonlinear interactions slave the growth and decay of product sound waves to that of the product Langmuir waves. The resulting probability distribution of ion-sound field strengths is predicted to have a flat tail extending to a high-field cutoff. This prediction is consistent with statistics derived here from ISEE 3 observations. Agreement is also found between the frequencies of the observed waves and predictions for the product S waves. The competing processes of nonlinear wave collapse and quasilinear relaxation are discussed, and it is concluded that neither is responsible for the saturation of Langmuir growth. When wave and beam inhomogeneities are accounted for, arguments from quasi-linear relaxation yield an upper bound on the Langmuir fields that is too high to be relevant. Nor are the criteria for direct wave collapse of the beam-driven waves met, consistent with earlier simulation results that imply that this process is not responsible for saturation of the beam instability. Indeed, even if the highest observed Langmuir fields are assumed to he part of a long-wavelength 'condensate' produced via electrostatic decay, they still fall short of the relevant requirements for wave collapse. The most stringent requirement for collapse is that collapsing wave packets not be disrupted by ambient density fluctuations in the solar wind. Fields of several mV m(exp -1) extending over several hundred km would be needed to satisfy this requirement; at 1 AU such fields are rare at best.

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

1993-01-01

265

Vertically Propagating Waves in the Upper Atmosphere of Saturn From Cassini Radio Occultations  

NASA Astrophysics Data System (ADS)

We present results from 12 ingress and egress soundings done within 10 degrees of Saturn's equator. Above the 100-mbar level, near the tropopause, the vertical profiles of temperature are marked by undulatory structure that may be associated with vertically propagating waves. We determine the properties and spectra of these waves, and speculate on their origins and their dynamical effects on the upper atmosphere.

Schinder, P. J.; Flasar, F. M.; Kliore, A. J.; French, R. G.; Marouf, E. A.; Nagy, A.; Rappaport, N.; Anabtawi, A.; Asmar, S.; Barbinis, E.; Fleischman, D. U.; Goltz, G. L.; Johnston, D. V.; Rochblatt, D.; McGhee, C. A.

2005-12-01

266

The Limiting Polarization of Downcoming Radio Waves Traveling Obliquely to the Earth's Magnetic Field  

Microsoft Academic Search

The paper is a theoretical discussion of the limiting polarization of downcoming electromagnetic waves propagated at oblique angles to the earth's magnetic field. The main conclusions arrived at are: (a). The polarization of the downcoming wave tends to a definite limit on leaving the Kennelly-Heaviside layer. The limiting polarization has been shown to be very nearly independent, for conditions that

W. G. Baker; A. L. Green

1933-01-01

267

Multiscale simulations of type III solar radio emission via beam-driven Langmuir waves  

Microsoft Academic Search

For most type III bursts, it is usual to invoke plasma emission mechanism to generate the observed levels of emission near the plasma frequency and its second harmonic. This mechanism consists of a sequence of steps: (i) the energetic electron beam generates primary Langmuir waves by a beam instability; (ii) the primary Langmuir waves undergo electrostatic decays and generate product

B. Li; P. Robinson; I. Cairns

2005-01-01

268

Analysis of wave fields by Fourier integral operators and their application for radio occultations  

Microsoft Academic Search

Fourier integral operators (FIOs) are used for constructing asymptotic solutions of wave problems and for the generalization of the geometrical optics. Geometric optical rays are described by the canonical Hamilton system, which can be written in different canonical coordinates in the phase space. The theory of FIOs generalizes the formalism of canonical transforms for solving wave problems. The FIO associated

M. E. Gorbunov; K. B. Lauritsen

2004-01-01

269

Dynamics of Langmuir and ion-sound waves in type III solar radio sources  

NASA Technical Reports Server (NTRS)

The study traces the evolution of Langmuir and ion-sound waves in type III sources, incorporating linear growth, linear damping, and nonlinear electrostatic decay. Improved estimates are obtained for the wavenumber range of growing waves and the nonlinear coupling coefficient for the decay process. It is shown that the conditions in the solar wind do not allow a steady state to be attained; instead, bursty linear and nonlinear interactions take place, consistent with the highly inhomogeneous and impulsive waves actually observed. Nonlinear growth is found to be rapid enough to saturate the growth of the parent Langmuir waves in the available interaction time. The competing processes of nonlinear wave collapse and quasi-linear relaxation are discussed, and it is concluded that neither is responsible for the saturation of Langmuir growth.

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

1993-01-01

270

Coordinated Radio, Electron, and Waves Experiment (CREWE) for the NASA Comet Rendezvous and Asteroid Flyby (CRAF) instrument  

NASA Technical Reports Server (NTRS)

The Coordinated Radio, Electron, and Waves Experiment (CREWE) was designed to determine density, bulk velocity and temperature of the electrons for the NASA Comet Rendezvous and Asteroid Flyby Spacecraft, to define the MHD-SW IMF flow configuration; to clarify the role of impact ionization processes, to comment on the importance of anomalous ionization phenomena (via wave particle processes), to quantify the importance of wave turbulence in the cometary interaction, to establish the importance of photoionization via the presence of characteristic lines in a structured energy spectrum, to infer the presence and grain size of significant ambient dust column density, to search for the theoretically suggested 'impenetrable' contact surface, and to quantify the flow of heat (in the likelihood that no surface exists) that will penetrate very deep into the atmosphere supplying a good deal of heat via impact and charge exchange ionization. This final report provides an instrument description, instrument test plans, list of deliverables/schedule, flight and support equipment and software schedule, CREWE accommodation issues, resource requirements, status of major contracts, an explanation of the non-NASA funded efforts, status of EIP and IM plan, descope options, and Brinton questions.

Scudder, Jack D.

1992-01-01

271

Analysis of Quasar Radio Wave Flux Density Fluctuations and its Cosmological Meanings  

NASA Astrophysics Data System (ADS)

The time series of microwave flux density variations (2.7 and 8.1 GHz) from 24 quasars was analyzed in the methods of power spectral index, Higuchi's fractal dimension, Hurst exponent, Correlation dimension and Kolmogorov entropy. The aim of study is to find cosmological meanings of analyzed results by mutually referring the indices varing with red shift of quasars. A systematic change was found among them, while yet unknown of discrimination between noise and dynamics of radio source systems.

Tanizuka, Noboru

2009-04-01

272

Quasi-harmonic faraday-rotation fluctuations of radio waves when sounding the outer solar corona  

Microsoft Academic Search

A statistical analysis of the Faraday-rotation fluctuations (FRFs) of linearly polarized radio signals from the Helios 1 and\\u000a Helios 2 spacecraft shows that the FRF time power spectra can be of three types. Spectra of the first type are well fitted\\u000a by a single power law in the range of fluctuation frequencies 1–10 mHz. Spectra of the second type are

A. I. Efimov; L. N. Samoznaev; V. E. Andreev; I. V. Chashei; M. K. Bird

2000-01-01

273

Quasi-Harmonic Faraday-Rotation Fluctuations of Radio Waves When Sounding the Outer Solar Corona  

Microsoft Academic Search

A statistical analysis of the Faraday-rotation fluctuations (FRFs) of linearly polarized radio signals from the Helios 1 and Helios 2 spacecraft shows that the FRF time power spectra can be of three types. Spectra of the first type are well fitted by a single power law in the range of fluctuation frequencies 1-10 mHz. Spectra of the second type are

A. I. Efimov; L. N. Samoznaev; V. E. Andreev; I. V. Chashei; M. K. Bird

2000-01-01

274

Surfing Long Waves of the Universe... ...The National Radio Astronomy Observatory in the 21st Century  

Microsoft Academic Search

IN 2006, the National Radio Astronomy Observatory (NRAO) passed the 50-year point in its service to the astronomical community\\u000a and now looks forward to an exciting future as one of the world’s premier resources for answering the key questions that challenge\\u000a 21st-century astronomy and physics. Today’s world-class suite of NRAO telescopes provides unique and powerful capabilities\\u000a for frontier research. Combined

David Finley

275

Scintillators and applications thereof  

DOEpatents

Scintillators of various constructions and methods of making and using the same are provided. In some embodiments, a scintillator comprises at least one radiation absorption region and at least one spatially discrete radiative exciton recombination region.

Williams, Richard T.

2014-07-15

276

Field strength variations of LF radio waves prior to earthquakes in central Italy  

NASA Astrophysics Data System (ADS)

The electric field strength of the LF radio broadcasting RMC (Principality of Monaco) which operates at 216 kHz has been recorded since January 1991 by two receivers in central Italy. During the monitoring period we observed two evident attenuations of the field strength in one receiver, with durations of 6-10 days. The geomagnetic and ionospheric observations carried out in the same time interval do not seem able to explain the attenuation of the radio signal. An analysis of the seismic activity occurring in the area between transmitter and receiver has revealed that some days after the attenuations the energy released by earthquakes reaches a maximum. The observed attenuation might therefore be precursors of earthquakes. We also checked meteorological conditions and found that advections of warm air occurred during both the two anomalous periods. It seems possible that these conditions can help the action of preseismic effects in generating irregularities in the vertical gradient of the tropospheric radio refractivity able to produce defocusing of LF radiobroadcast propagation.

Bella, F.; Biagi, P. F.; Caputo, M.; Cozzi, E.; Della Monica, G.; Ermini, A.; Plastino, W.; Sgrigna, V.

277

External heating of stents by radio waves Pilot studies in rabbit aorta  

SciTech Connect

Purpose: This experiment was designed to assess the feasibility of radio frequency energy delivered by a prototype radio frequency generator inductive heating device (REVAX) positioned external to the body, for transient heating of stents after arterial implant. Methods and Materials: Twenty-one New Zealand White rabbits underwent stenting of their infrarenal aorta. Nine rabbits were stented and immediately placed in the REVAX for external stent heating with internal temperature probes in place. Twelve rabbits were stented and 3 days later either heated or placed in the generator as a sham for 20 min. The animals were terminated 28 days later. Results: The REVAX was able to heat the aortic stents in a controlled fashion; in Phase II experiments, the stent temperature was raised to 42 deg. C for 20 min. In Phase I mild necrosis was noted at the stent struts. In Phase II, necrosis and mineralization of the media was seen at the stent struts, and evidence of neointimal suppression was observed. Conclusion: This study demonstrated that external heating of stents in a blood vessel in a live animal via radio frequency energy is feasible. Further studies will be needed to assess whether any specific heating regimen might inhibit fibrocellular neointimal hyperplasia.

Levitt, Adam B.; Robinson, Keith; Chronos, Nicolas A.F.; Daum, Wolfgang

2003-09-01

278

Measurement of a Phase of a Radio Wave Reflected from Rock Salt and Ice Irradiated by an Electron Beam for Detection of Ultra-High-Energy Neutrinos  

E-print Network

We have found a radio-wave-reflection effect in rock salt for the detection of ultra-high energy neutrinos which are expected to be generated in Greisen, Zatsepin, and Kuzmin (GZK) processes in the universe. When an UHE neutrino interacts with rock salt or ice as a detection medium, a shower is generated. That shower is formed by hadronic and electromagnetic avalanche processes. The energy of the UHE neutrino shower converts to thermal energy through ionization processes. Consequently, the temperature rises along the shower produced by the UHE neutrino. The refractive index of the medium rises with temperature. The irregularity of the refractive index in the medium leads to a reflection of radio waves. This reflection effect combined with the long attenuation length of radio waves in rock salt and ice would yield a new method to detect UHE neutrinos. We measured the phase of the reflected radio wave under irradiation with an electron beam on ice and rock salt powder. The measured phase showed excellent consis...

Chiba, Masami; Tanikawa, Takahiro; Yano, Hiroyuki; Yabuki, Fumiaki; Yasuda, Osamu; Chikashige, Yuichi; Kon, Tadashi; Shimizu, Yutaka; Watanabe, Souichirou; Utsumi, Michiaki; Fujii, Masatoshi

2013-01-01

279

Estimation of the probability distribution of the molecular distribution of radio waves with frequencies greater than 10 GHz in the atmosphere  

NASA Astrophysics Data System (ADS)

The parameters of the probability distribution of the molecular absorption of radio waves with frequencies greater than 10 GHz in the atmosphere are estimated on the basis of measurements of air temperature, pressure, and moisture. The parameters of the monthly probability distributions of the meteorological parameters and the molecular absorption coefficients at 15 frequencies are presented.

Pozhidaev, V. N.

1990-11-01

280

Growth of electric space-charge and radio waves in moving ion streams  

Microsoft Academic Search

The following conclusions are reached:(i) In a medium comprising two identical interpenetrating ion streams, four electric space-charge phenomena may occur. The 'fast' and 'slow' travelling waves do not concern us; the two effects of interest are non-travelling in a system in which the medium as a whole is at rest.(ii) The first is most probably a set of evanescent waves.

J. H. Piddington

1958-01-01

281

Internal, nonperturbing, radio frequency wave monitor reflectometer system on the DIII-D tokamaka)  

NASA Astrophysics Data System (ADS)

A new reflectometer system designed to monitor density fluctuations associated with rf waves has been successfully demonstrated on the DIII-D tokamak. It is a direct, internal, and nonperturbing diagnostic with access into the plasma core. This new diagnostic is motivated by a desire to improve understanding of rf wave physics issues, such as wave trajectory, heating mechanisms, rf wave deposition profile, and wave number, and is highly relevant to planned tokamaks such as ITER and TPX. This work is the first application of reflectometry to rf wave studies in a tokamak. Feedforward tracking receiver techniques are employed to remove frequency instabilities due to inherent drifts in the microwave sources and frequency pulling. In order to minimize spurious pickup of the rf pulse (˜60 MHz), heterodyne detection techniques are utilized, and all components are installed inside an rf shielding box. The system operates in the extraordinary mode (X-mode) at 70 GHz. In this paper, a detailed description of the system, and data illustrating its successful operation will be presented.

Lee, J. H.; Doyle, E. J.; Luhmann, N. C., Jr.; Peebles, W. A.; Petty, C. C.; Pinsker, R. I.; Rettig, C. L.; Rhodes, T. L.

1995-02-01

282

Scintillator materials for calorimetry  

SciTech Connect

Requirements for fast, dense scintillator materials for calorimetry in high energy physics and approaches to satisfying these requirements are reviewed with respect to possible hosts and luminescent species. Special attention is given to cerium-activated crystals, core-valence luminescence, and glass scintillators. The present state of the art, limitations, and suggestions for possible new scintillator materials are presented.

Weber, M.J. [Lawrence Berkeley Lab., CA (United States). Life Sciences Div.

1994-09-01

283

Scintillator reflective layer coextrusion  

DOEpatents

A polymeric scintillator has a reflective layer adhered to the exterior surface thereof. The reflective layer comprises a reflective pigment and an adhesive binder. The adhesive binder includes polymeric material from which the scintillator is formed. A method of forming the polymeric scintillator having a reflective layer adhered to the exterior surface thereof is also provided. The method includes the steps of (a) extruding an inner core member from a first amount of polymeric scintillator material, and (b) coextruding an outer reflective layer on the exterior surface of the inner core member. The outer reflective layer comprises a reflective pigment and a second amount of the polymeric scintillator material.

Yun, Jae-Chul (Naperville, IL); Para, Adam (St. Charles, IL)

2001-01-01

284

Effect of local inhomogeneity of the ionosphere on the propagation of ULF radio waves  

Microsoft Academic Search

The Stratton-Chu integral equation is used to solve the electrodynamic problem concerning the propagation of ULF waves in an inhomogeneous spherical earth-ionosphere cavity. The effect of the local inhomogeneity of the ionosphere is taken into account in the framework of the Born approximation of perturbation theory. An analysis is made of perturbation variations of the vertical electric component of the

A. P. Nikolaenko

1984-01-01

285

Time variations in millimeter-wave radio recombination lines from the Be star MWC 349A  

NASA Astrophysics Data System (ADS)

Observations of the 1-mm radio recombination lines (RRLs) MWC 349 from December 1989 through May 1991 are reported. A model proposed for MWC 349A by Hamann and Simon (1986, 1988) from optical emission and IR emission lines is used to advance the hypothesis that the time-varying RRLs come from the outer region of a circumstellar disk in Keplerian rotation embedded in the much larger, expanding, ionized region that encloses the entire star and disk system. The variable velocities then result from changes in radial position within the Keplerian disk. As wavelength increases from 1 mm, the masing RRLs from the inner disk weaken, and the free-free opacity of the outer region increases. The composite RRL line profiles become increasingly dominated by contributions from the expanding region enclosing the MWC 349A circumstellar disk.

Gordon, M. A.

1992-03-01

286

Disks, Young Stars, and Radio Waves: The Quest for Forming Planetary Systems  

NASA Astrophysics Data System (ADS)

Kant and Laplace suggested the Solar System formed from a rotating gaseous disk in the 18th century, but convincing evidence that young stars are indeed surrounded by such disks was not presented for another 200 years. As we move into the 21st century the emphasis is now on disk formation, the role of disks in star formation, and on how planets form in those disks. Radio wavelengths play a key role in these studies, currently providing some of the highest-spatial-resolution images of disks, along with evidence of the growth of dust grains into planetesimals. The future capabilities of EVLA and ALMA provide extremely exciting prospects for resolving disk structure and kinematics, studying disk chemistry, directly detecting protoplanets, and imaging disks in formation.

Chandler, C. J.; Shepherd, D. S.

2008-08-01

287

Li-containing scintillating bolometers for low background physics  

NASA Astrophysics Data System (ADS)

We present the performances of Li-based compounds used as scintillating bolometer for rare decay studies such as double-beta decay and direct dark matter investigations. The compounds are tested in a dilution refrigerator installed in the underground laboratory of Laboratori Nazionali del Gran Sasso (Italy). Low temperature scintillating properties are investigated by means of different radioactive sources, and the radio-purity level for internal contaminations are estimated for possible employment for next generation experiments.

Pattavina, L.

2014-01-01

288

Effects of large-scale irregularities of the ionosphere in the propagation of decametric radio waves  

Microsoft Academic Search

A numerical experiment is used to study the simultaneous influence of regular space-time gradients and large-scale traveling ionospheric disturbances (TIDs) as manifested in the angular and Doppler characteristics of decametric-wave propagation. Conditions typical for middle latitudes are chosen as the ionospheric models: conditions under which large-scale TIDs in the F2-layer evolve on the background of winter or equinox structures of

T. S. Kerblai; E. M. Kovalevskaia

1985-01-01

289

Simulation of Self-consistent Radio Wave Artificial Ionospheric Turbulence Pumping and Damping  

NASA Astrophysics Data System (ADS)

The numerical simulations of the action of self-consistent incident powerful electromagnetic wave absorption arising in the regions of artificial plasma turbulence excitation at formation, saturation and relaxation stages of turbulent structures (Kochetov, A.V., Mironov, V.A., Te-rina, G.I., Bubukina V. N, Physica D, Nonlinear phenomena, 2001, 152-153, 723) to reflection index dynamics are carried out. The nonlinear Schrüdinger equation in inhomogeneous plasma layer with incident electromagnetic wave pumping and backscattered radiation damping (Ko-chetov, et al, Adv. Space Res., 2002, 29, 1369 and 2006, 38, 2490) is extended with the imagi-nary part of plasma dielectric constant (volume damping), which is should be taken into account in strong electromagnetic field plasma regions and results the energy transformation from elec-tromagnetic waves to plasma ones at resonance interaction (D.V. Shapiro, V.I. Shevchenko, in Handbook of Plasma Physics 2, eds. A.A Galeev, R.N. Sudan. Elsevier, Amsterdam, 1984). The volume damping reproduces the basic energy transformation peculiarities: hard excitation, nonlinearity, hysteresis (A.V. Kochetov, E. Mjoelhus, Proc. of IV Intern. Workshop "SMP", Ed. A.G. Litvak, Vol.2, N. Novgorod, 2000, 491). Computer modeling demonstrates that the amplitude and period of reflection index oscillations at the formation stage slowly depend on damping parameters of turbulent plasma regions. The transformation from complicated: quasi-periodic and chaotic dynamics, to quasi-stationary regimes is shown at the saturation stage. Transient processes time becomes longer if the incident wave amplitude and nonlinear plasma response increase, but damping decreases. It is obtained that the calculated reflection and absorption index dynamics at the beginning of the saturation stage agrees qualitatively to the experimental results for ionosphere plasma modification study (Thide B., E.N. Sergeev, S.M. Grach, et. al., Phys. Rev. Lett., 2005, 95, 255002). The work was supported in part by RFBR grant 09-02-01150-a.

Kochetov, Andrey

290

Self-consistent Powerful Radio-wave Absorption by Artificial Ionosphere Turbulence  

NASA Astrophysics Data System (ADS)

The numerical simulations of non-linear Schrodinger equation in inhomogeneous plasma layer with pumping and damping are carried out to investigate the influence of self-consistent incident powerful electromagnetic wave absorption in the regions of plasma turbulence excitation to reflection index dynamics. The damping of electromagnetic wave is taking into account by including in the set of equations (Kochetov A.V., Mironov V. A., Terina G.I., Strong Turbulence Effects in Artificially Disturbed Ionosphere, Adv. Space.Res. 2002,vol.29, No.9, p.1369) imaginary part of plasma dielectric permitivity in the vicinity of wave reflection point in the regions with strong electromagnetic field. The large range of damping parameters: threshold, decrement; different amplitude dependence, including hysteretic one, is studied, in particular, in correlation to (V. D. Shapiro, V. I. Shevchenko, Handbook of Plasma Physics, Eds. A. A. Galeev, R N. Sudan, Elsevier, 1984, vol.2, p.119). It is obtained for some regimes that the calculated reflection index dynamics agrees qualitatively to the experimental results (B. Thide, E. N. Sergeev, S. M. Grach,T. B. Leyser, T. D. Carrozi, Competition between Langmuir and upper hybrid turbulence in an HF pumped ionosphere, Phys. Rev. Lett., 2005, vol. 95, no.25, p. 255002). The work is supported in part by Russian Foundation for Basic Research by the grant No. 06-02-17334.

Kochetov, Andrey; Menkova, Uliya; Grach, Savely

291

Small Scale Wave Structures in the Martian Atmosphere as seen by the Radio Science Experiment MaRS on Mars Express  

NASA Astrophysics Data System (ADS)

The Radio Science Experiment MaRS on Mars Express is sounding the Martian atmosphere and ionosphere using the spacecraft radio subsystem. A simultaneous and coherent dual-frequency downlink at X- and S-band via the Spacecraft's High Gain Antenna (HGA) is required to separate effects of dispersive media from the classical Doppler shift. Vertical profiles of pressure, temperature and density in the neutral atmosphere can be derived with an altitude resolution of only a few hundred metres. The high vertical resolution of the MaRS temperature profiles provides the unique opportunity to study small scale vertical wave structures in the Martian lower atmosphere between the surface and about 40 km. Several of these small scale temperature perturbations are caused by gravity waves (buoyancy waves) induced by atmospheric processes like topographical forcing, convection, or wind shear. Gravity waves play a significant role in the energy and momentum budget of the Earth and comparable important effects are also predicted for Mars. Observations of vertical small scale gravity waves on Mars are still sparse on the other hand. The small scale temperature perturbations with vertical wavelengths smaller than 10 kilometres are examined to investigate the global distribution and seasonal variability of gravity wave energy on Mars. Comparisons with other independent measurements and model predictions will be shown.

Tellmann, S.; Paetzold, M.; Haeusler, B.; Tyler, G. L.; Hinson, D. P.

2011-12-01

292

Recent development in organic scintillators  

NASA Technical Reports Server (NTRS)

Discussion on recent developments of organic scintillators includes studies of organic compounds that form glass-like masses which scintillate and are stable at room temperature, correlations between molecular structure of organic scintillators and self-quenching, recently developed fast scintillators, and applications of liquid-scintillation counters.

Horrocks, D. L.; Wirth, H. O.

1969-01-01

293

Potential Spacecraft-to-Spacecraft Radio Observations with EJSM: Wave of the Future? (Invited)  

NASA Astrophysics Data System (ADS)

Future active radio observations of planetary and satellite atmospheres and surfaces could significantly benefit form the presence of two or more spacecraft in orbit around a target object. Traditionally, radio occultation and bistatic surface scattering experiments have been conducted using a single spacecraft operating in the Downlink (DL) configuration, with the spacecraft transmitting and at least one Earth-based station receiving. The configuration has the advantage of using powerful ground-based receivers for down-conversion, digitization, and digital recording of large bandwidth data for later off-line processing and analysis. It has the disadvantage of an available free-space signal-to-noise ratio (SNR) limited by the relatively small carrier power (10-20 W) a spacecraft can practically transmit. Recent technological advances in designing small-mass and small-power spacecraft-based digital receivers capable of on-board signal processing could open the door for significant performance improvement compared with the DL configuration. For example, with two spacecraft in orbit instead of one, the smaller distance D between the two spacecraft compared with the distance to Earth can boost achievable free-space SNR by one to three orders of magnitude, depending on D. In addition, richer variability in observation geometry can be captured using spacecraft-to-spacecraft (SC-to-SC) radio occultations and surface scattering. By their nature, traditional DL occultations are confined to the morning and evening terminators. Availability of on-board processing capability also opens the door for conducting Uplink (UL) occultation and bistatic observations, where very large power (> 20 kW) can be transmitted from an Earth-based station, potentially boasting achievable free-space SNR by orders of magnitude, comparable to the SC-to-SC case and much higher than the DL case. The Europa Jupiter System Mission (EJSM) will likely be the first planetary mission to benefit from the unprecedented opportunity of having two highly capable spacecraft orbiting Jupiter in concert and during the same time window. The strawman payload of the American Jupiter Europa Orbiter (JEO) and the European Jupiter Ganymede Orbiter (JGO) envisions at least one spacecraft (JGO) hosting an on-board digital receiving and processing capability. The receiver is specifically designed to allow for synergistic SC-to-SC observations, as well as Earth-to-JGO UL observations. In principle, each spacecraft can host an on-board digital receiver for rich combinations of high-performance synergistic or individual observations, depending on the opportunity. For the envisioned EJSM strawman payload and example tour, we examine achievable performance for potential observations that include SC-to-SC, UL, and DL occultations of Jupiter’s ionosphere and neutral atmosphere, the ionospheres and thin atmospheres of the large Jovian satellites, and of the tenuous Jovian Rings. We also consider potential bistatic scattering (bistatic-radar) observation opportunities of the surfaces of Europa and Ganymede.

Marouf, E. A.; Tortora, P.; Asmar, S. W.; Folkner, W. M.; Hinson, D.; Iess, L.; Linscott, I. R.; Lorenz, R. D.; Mueller-Wodarg, I. C.

2010-12-01

294

Shifting scintillator neutron detector  

DOEpatents

Provided are sensors and methods for detecting thermal neutrons. Provided is an apparatus having a scintillator for absorbing a neutron, the scintillator having a back side for discharging a scintillation light of a first wavelength in response to the absorbed neutron, an array of wavelength-shifting fibers proximate to the back side of the scintillator for shifting the scintillation light of the first wavelength to light of a second wavelength, the wavelength-shifting fibers being disposed in a two-dimensional pattern and defining a plurality of scattering plane pixels where the wavelength-shifting fibers overlap, a plurality of photomultiplier tubes, in coded optical communication with the wavelength-shifting fibers, for converting the light of the second wavelength to an electronic signal, and a processor for processing the electronic signal to identify one of the plurality of scattering plane pixels as indicative of a position within the scintillator where the neutron was absorbed.

Clonts, Lloyd G; Cooper, Ronald G; Crow, Jr., Morris Lowell; Hannah, Bruce W; Hodges, Jason P; Richards, John D; Riedel, Richard A

2014-03-04

295

Radiation hazards of radio frequency waves on the early embryonic development of Zebrafish  

NASA Astrophysics Data System (ADS)

With the growing use of wireless devices in almost all day-to-day activities, exposure to radio-frequency radiation has become an immediate health concern. It is imperative that the effects of such radiation not only on humans, but also on other organisms be well understood. In particular, it is critical to understand if RF radiation has any bearing on the gene expression during embryonic development, as this is a crucial and delicate phase for any organism. Owing to possible effects that RF radiation may have on gene expression, it is essential to explore the carcinogenic or teratogenic properties that it may show. This study observed the effects of RF radiation emitted from a cellular telephone on the embryonic development of zebra fish. The expression of the gene shha plays a key role in the early development of the fish. This gene has homologs in humans as well as in other model organisms. Additionally, several biomarkers indicative of cell stress were examined: including lactate dehydrogenase (LDH), superoxide dismutase (SOD), and lipid peroxidation (LPO). Results show a significant decrease in the expression of shha, a significant decrease in LDH activity. There was no significant increase in SOD and LPO activity. No morphological abnormalities were observed in the developing embryos. At present, these results indicate that exposure to cell phone radiation may have a suppressive effect on expression of shha in D. rerio, though such exposure does not appear to cause morphological detriments. More trials are underway to corroborate these results.

Harkless, Ryan; Al-Quraishi, Muntather; Vagula, Mary C.

2014-06-01

296

Lead carbonate scintillator materials  

DOEpatents

Improved radiation detectors containing lead carbonate or basic lead carbonate as the scintillator element are disclosed. Both of these scintillators have been found to provide a balance of good stopping power, high light yield and short decay constant that is superior to other known scintillator materials. The radiation detectors disclosed are favorably suited for use in general purpose detection and in medical uses. 3 figures.

Derenzo, S.E.; Moses, W.W.

1991-05-14

297

The large adaptive reflector: a 200-m diameter wideband centimeter- to meter-wave radio telescope  

NASA Astrophysics Data System (ADS)

The Large Adaptive Reflector (LAR) is a concept for a low- cost, large aperture, wideband, radio telescope, designed to operate over the wavelength range from 2 m to 1.4 cm. It consists of a 200-m diameter actuated-surface parabolic reflector with a focal length of 500 m, mounted flat on the ground. The feed is held in place by a tension-structure, consisting of three or more tethers tensioned by the lift of a large, helium-filled aerostat -- a stiff structure that effectively resists wind forces. The telescope is steered by simultaneously changing the lengths of the tethers with winches (thus the position of the feed) and by modifying the shape of the reflector. At all times the reflector configuration is that of an offset parabolic antenna, with the capability to point anywhere in the sky above approximately 15 degree Elevation Angle. At mid-range wavelengths, the feed is a multi-beam prime-focus phased array, about 5 m diameter; at meter wavelengths, it is a single-beam phased array of up to 10 m diameter. Simulations have shown that in operating wind conditions (10 m/s average speed with 2.5 m/s gusts), the position of the feed platform can be stabilized to within a few cm over time scales of approximately 20 s. Research indicates that the telescope concept is feasible and that an order of magnitude improvement in cost per m2 of collecting area over traditional designs of large parabolic antennas can be achieved.

Carlson, Brent; Bauwens, Luc; Belostotski, Leonid; Cannon, Elizabeth; Chang, Ya-Ying; Deng, Xiaohui; Dewdney, Peter E.; Fitzsimmons, Joeleff T.; Halliday, David; Kuerschner, Kai; Lachapelle, Gerard; Lo, David; Mousavi, Pedram; Nahon, Meyer; Shafai, Lot; Stiemer, Sigfried F.; Taylor, Russell; Veidt, Bruce

2000-07-01

298

Full-Duplex 25GHz Spacing DWDM MM-Wave-Band Radio-on-Fiber System Using a Supercontinuum Light Source and Arrayed-Waveguide-Grating Filters  

Microsoft Academic Search

We demonstrate for the first time the full-duplex transmission of 25-GHz spacing dense wavelength-division multiplexing (DWDM) millimeter-wave-band radio-on-fiber (RoF) system using a supercontinuum (SC) light source and optical frequency interleaving technique. In the proposed scheme, filtering response of the arrayed waveguide gratings for demultiplexer and multiplexer is used for suppression of undesired optical sidebands. All the 25-GHz spacing SC modes

Takahiro Sono; Yoshitomo Takahashi; Teppei Nakasyotani; Hiroyuki Toda; Toshiaki Kuri; K. Kitayama

2006-01-01

299

Radio-wave exposure of the human head: analytical study based on a versatile eccentric spheres model including a brain core and a pair of eyeballs  

Microsoft Academic Search

A versatile eccentric-spheres model of the human head is used to investigate radio-wave absorption. Numerical results, obtained by use of an exact analytical solution, are presented for the total, percentage, and gram-specific absorption. Interest is mainly in the brain and in the eyes of an adult or an infant head. Our model comprises a host sphere and several spherical inclusions,

Angela P. Moneda; Melina P. Ioannidou; Dimitris P. Chrissoulidis

2003-01-01

300

A hybrid technique based on combining ray tracing and FDTD methods for site-specific modeling of indoor radio wave propagation  

Microsoft Academic Search

The paper presents a hybrid technique based on combining ray tracing and finite-difference time-domain (FDTD) methods for site-specific modeling of indoor radio wave propagation. Ray tracing is used to analyze the wide area and FDTD is used to study areas close to complex discontinuities where ray-based solutions are not sufficiently accurate. The hybrid technique ensures improved accuracy and practicality in

Ying Wang; Safieddin Safavi-Naeini; Sujeet K. Chaudhuri

2000-01-01

301

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)

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.

Gnanalingam, S.; Kane, J. A.

1975-01-01

302

Low-frequency radio wave propagation in the earth-ionosphere waveguide disturbed by a large-scale three-dimensional irregularity  

Microsoft Academic Search

In this paper, we develop further the analytical and numerical method of solving three-dimensional problems in the theory\\u000a of radio wave propagation, including three-dimensional local inhomogeneities (ionospheric disturbances or Earth’s surface\\u000a irregularities). To model the Earth-ionosphere waveguide, we use the surface impedance concept, by which the irregularity\\u000a extending beyond one waveguide wall has an arbitrary smooth shape, and its surface

O. V. Soloviev

1998-01-01

303

Simultaneous Multiplexing and Demultiplexing of Wavelength-Interleaved Channels in DWDM Millimeter-Wave Fiber-Radio Networks  

NASA Astrophysics Data System (ADS)

A simultaneous multiplexing and demultiplexing (MUX/DEMUX) scheme for wavelength-interleaved millimeter-wave 37.5-GHz-band fiber-radio channels spaced at 25 GHz has been proposed. The proposed MUX/DEMUX technique potentially realizes simple, compact, and low-cost central office and remote nodes by avoiding the use of wavelength-selective pre-and postprocessing hardware. The novel scheme incorporates an arrayed-waveguide grating with multiple loop-backs between the input and the output ports, in addition to multiple optical circulators and optical isolators. The multiplexing functionality of the proposed technology enables a carrier subtraction technique and consequently reduces the carrier-to-sideband ratios of the multiplexed channels. Multiplexing of the uplink channels generated via several methods is demonstrated experimentally. These techniques include generation of the channels by using the optical carriers that correspond to wavelengths spaced at the free spectral range (FSR) or multiples of the FSR from the downlink (DL) optical carriers and reuse of the DL optical carriers that are recovered by applying a wavelength reuse technique (?UL = ?DL pm n × FSR, where n = 0, 1, 2, 3, ldots). The demultiplexing functionality of the proposed scheme that separates the 37.5-GHz-band wavelength-interleaved DL channels spaced at 25 GHz is also demonstrated. In addition, the effect of optical crosstalk on the transmission performance of the demultiplexed channels is also characterized experimentally.

Bakaul, Masuduzzaman; Nirmalathas, Ampalavanapillai Thas; Lim, Christina; Novak, Dalma; Waterhouse, Rod B.

2006-09-01

304

Electron-ion temperature ratio estimations in the summer polar mesosphere when subject to HF radio wave heating  

NASA Astrophysics Data System (ADS)

We have inferred the electron temperature enhancements above mesospheric altitudes under Polar Mesospheric Summer Echoes (PMSE) conditions when the ionosphere is exposed to artificial HF radio wave heating. The proposed method uses the dependence of the radar cross section on the electron-to-ion temperature ratio to infer the heating factor from incoherent scatter radar (ISR) power measurements above 90 km. Model heating temperatures match our ISR estimations between 90 and 130 km with 0.94 Pearson correlation index. The PMSE strength measured by the MORRO MST radar is about 50% weaker during the heater-on period when the modeled electron-to-ion mesospheric temperature is approximately 10 times greater than the unperturbed value. No PMSE weakening is found when the mesospheric temperature enhancement is by a factor of three or less. The PMSE weakening and its absence are consistent with the modeled mesospheric electron temperatures. This consistency supports to the proposed method for estimating mesospheric electron temperatures achieved by independent MST and ISR radar measurements.

Pinedo, H.; La Hoz, C.; Havnes, O.; Rietveld, M.

2014-10-01

305

Study of effects of radio-wave frequency radiation emitted from cellular telephones on embryonic development of danio rerio  

NASA Astrophysics Data System (ADS)

Radio wave frequency (RF) radiation emitted from cellular telephones has become increasingly ubiquitous as a result of the popularity of these phones. With the increasing and unavoidable exposure to RF radiation a reality, it is imperative that the effects of such radiation on living tissue be well understood. In particular, it is critical to understand any effects that RF radiation may have as a carcinogen and on embryonic development, as pregnant women are not exempt from such exposure. As a model organism, zebrafish (Danio rerio) have been studied extensively, and their value in studies of gene expression cannot be overstated. This study observed the effects of RF radiation on the embryonic development of zebrafish. The expression of two genes, shha and hoxb9a, that are key to the early development of the fish was examined. Both genes have homologs in humans as well as in other model organisms. Preliminary results suggest that exposure to cell phone radiation might have an effect on the expression of shha in zebrafish embryos, causing under expression. More trials are necessary to validate these results.

Vagula, Mary; Harkless, Ryan

2013-05-01

306

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

PubMed Central

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.

?en, Alper; Gümü?ay, M. Ümit; Kavas, Aktül; Bulucu, Umut

2008-01-01

307

Statistics of ionospheric scintillation occurrence over European high latitudes  

NASA Astrophysics Data System (ADS)

Rapid fluctuation in the amplitude and phase of transionospheric radio signals caused by small scale ionospheric plasma density irregularities is known as scintillation. Over the high latitudes, irregularities causing scintillation are associated with large scale plasma structures and scintillation occurrence is mainly enhanced during geomagnetic storms. This paper presents a statistical analysis of scintillation occurrence on GPS L1C/A signal at a high latitude station located in Bronnoysund (geographic latitude 65.5°N, geographic longitude 12.2°E; corrected geomagnetic (CGM) latitude 62.77°N), Norway, during the periods around the peaks of solar cycles 23 (2002-2003) and 24 (2011-2013). The analysis revealed that the scintillation occurrence at Bronnoysund during both the solar maximum periods maximises close to the midnight magnetic local time (MLT) sector. A higher occurrence of scintillation is observed on geomagnetically active days during both the solar maximum periods. The seasonal pattern of scintillation occurrence indicated peaks during the summer and equinoctial months. A comparison with the interplanetary magnetic field (IMF) components By and Bz showed an association of scintillation occurrence with the southward IMF Bz conditions.

Sreeja, V.; Aquino, M.

2014-12-01

308

Design and multiphysics analysis of a 176Â MHz continuous-wave radio-frequency quadrupole  

NASA Astrophysics Data System (ADS)

We have developed a new design for a 176 MHz cw radio-frequency quadrupole (RFQ) for the SARAF upgrade project. At this frequency, the proposed design is a conventional four-vane structure. The main design goals are to provide the highest possible shunt impedance while limiting the required rf power to about 120 kW for reliable cw operation, and the length to about 4 meters. If built as designed, the proposed RFQ will be the first four-vane cw RFQ built as a single cavity (no resonant coupling required) that does not require ?-mode stabilizing loops or dipole rods. For this, we rely on very detailed 3D simulations of all aspects of the structure and the level of machining precision achieved on the recently developed ATLAS upgrade RFQ. A full 3D model of the structure including vane modulation was developed. The design was optimized using electromagnetic and multiphysics simulations. Following the choice of the vane type and geometry, the vane undercuts were optimized to produce a flat field along the structure. The final design has good mode separation and should not need dipole rods if built as designed, but their effect was studied in the case of manufacturing errors. The tuners were also designed and optimized to tune the main mode without affecting the field flatness. Following the electromagnetic (EM) design optimization, a multiphysics engineering analysis of the structure was performed. The multiphysics analysis is a coupled electromagnetic, thermal and mechanical analysis. The cooling channels, including their paths and sizes, were optimized based on the limiting temperature and deformation requirements. The frequency sensitivity to the RFQ body and vane cooling water temperatures was carefully studied in order to use it for frequency fine-tuning. Finally, an inductive rf power coupler design based on the ATLAS RFQ coupler was developed and simulated. The EM design optimization was performed using cst Microwave Studio and the results were verified using both hfss and ansys. The engineering analysis was performed using hfss and ansys and most of the results were verified using the newly developed cst Multiphysics package.

Kutsaev, S. V.; Mustapha, B.; Ostroumov, P. N.; Barcikowski, A.; Schrage, D.; Rodnizki, J.; Berkovits, D.

2014-07-01

309

A mathematical analysis of the theory of interplanetary scintillation in the weak scattering approximation  

Microsoft Academic Search

We present a simplified analytic technique for modeling the interplanetary scintillation of radio sources of finite angular size with a power law electron density fluctuation power spectrum. The simplification results from the representation of the scintillation spectrum in confluent hypergeometric functions. The approximations presented allow fast numerical evaluation of a spectrum for a weak scattering but extended medium with <10%

D. G. Mitchell; E. C. Roelof

1976-01-01

310

Ionizations scintillation detectors  

NASA Astrophysics Data System (ADS)

A few references are made to factors which affect the energy resolution of proportional scintillation. The coupling of proportional or primary scintillation devices to photoionization detectors (PIPS chamber) is considered, both in the gas and liquid phases, and using the data available some information is given concerning its expected characteristics of energy, position and time resolution.

Policarpo, A. J. P. L.

311

European low-noise MMIC technologies for cryogenic millimetre wave radio astronomical applications  

NASA Astrophysics Data System (ADS)

The Low Noise technology has a paramount relevance on radiotelescopes and radiometers performances. Its influence on sensitivity and temporal stability has a deep impact on obtainable scientific results. As well known, front end active part of scientific instruments are cryocooled in order to drastically reduce the intrinsic thermal noise generated by its electronic parts and consequently increase the sensitivity. In this paper we will describe the obtained results by an Italian Space Agency funded activity. The aim is to validate European MMIC Low Noise technologies and designs for cryogenic environments in the range of millimetre wave. As active device, HEMT (High Electron Mobility Transistor) are considered the best device for high frequency and low noise cryo applications. But not all the semiconductor foundry process are suitable for applications in such environment. Two European Foundries has been selected and two different HEMT based Low Noise Amplifiers have been designed and produced. The main goal of this activity is identify an European technology basement for space and ground based low noise cryogenic applications. Designs, layout, architectures, foundry processes and results will be compared.

Cremonini, Andrea; Mariotti, Sergio; Valenziano, Luca

2012-09-01

312

Systematic forward scatter radar observations of radio waves from meteoroid streams  

NASA Astrophysics Data System (ADS)

Forward scatter (FS) continuous wave (CW) meteor radar observations carried out during 1992-95 over the long baseline Bologna-Lecce in Italy, enabled us to determine the mass distribution versus duration of particles in main meteoroid streams (Lyrids, eta Aquarids, delta Aquarids, Perseids, Orionids, Leonids, Geminids) and the sporadic background. The unexpected high proportion of short-lived echoes with duration T < 0.2s suggests that the missing mass of meteor particles observed so far by backscatter radars in the 1E-6 - 1E-4 g mass range, is present in the form of faint high-velocity meteors, which ablate above the echo ceiling of conventional radars. The trends of the mass distribution of particles for the quoted meteor complexes are discussed in terms of variation of the mass index s and of steady-state conditions for each meteor population. The combined cumulative distributions of meteor trails vs peak signal amplitudes and vs durations represent a more reliable indicator of the meteoroid stream activity and, consequently, of the mass index variation. The mass index values of the sporadic background are generally higher than for meteor showers in the duration range of 0.1

Cevolani, G.; Bortolotti, G.; Foschini, L.; Franceschi, C.; Gabucci, M. F.; Trivellone, G.

1996-07-01

313

Waves  

NSDL National Science Digital Library

We will review some basic properties of waves and then further explore sound and light. For a quick overview of some properties of all waves, click on this first site. Make sure you fill out your hand out as you work! Waves and Wave Motion : Describing Waves Practice what you've already learned about waves with this site: Waves This site will let you play around some more with transverse waves: Wave on a String Sound waves are mechanical waves, ...

Petersen, Mrs.

2014-05-27

314

a Study on the Radio Propagation in the Korean Ionosphere  

Microsoft Academic Search

The effects of the ionosphere on the radio wave propagation are scattering of radio waves, attenuation, angle error, ranging error, and time delay. If ionospheric conditions are suitable, the charged particles can remove energy from radio waves and thus attenuate the signal. Also, a radio wave traveling a path along which the electron density is not constant undergoes changes in

Seok-Hee Bae; Kyu-Hong Choi; Jai-Rim Yuk; Hong-Ik Kim; Kyoung W. Min

1992-01-01

315

Fine Structure of Solar Radio Bursts Observed at Decametric and Hectometric Waves  

NASA Astrophysics Data System (ADS)

The analysis of WIND/WAVES RAD2 spectra with fine structure in the form of different fibers in 14 events covering 1997 2005 is carried out. A splitting of broad bands of the interplanetary (IP) type II bursts into narrow band fibers of different duration is observed. The instantaneous-frequency bandwidth of fibers is stable: 200 300 kHz for slow-drifting fibers in type II bursts, and 700 1000 kHz for fast-drifting fibers in type II + IV (continuum). Intermediate drift bursts (IDB or fiber bursts) and zebra patterns with variable frequency drift of stripes, typical for the metric range, were not found. Comparison of spectra with the Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph (SOHO/LASCO C2) images shows a connection of the generation of the fiber structures with the passage of shock fronts through narrow jets in the wake of Coronal Mass Ejections (CME). Therefore the most probable emission mechanism of fibers in IP type II bursts appears to be resonance transition radiation (RTR) of fast particles at the boundary of two media with different refractive indices. The same mechanism is also valid for striae in the type III bursts. Taking into account a high-density contrast in the CME wake and the actually observed small-scale inhomogeneities, the effectiveness of the RTR mechanism in IP space must be considerably higher than in the meter or decimeter wavelengths. For the most part the fibers in the type IV continuum at frequencies of 14 8 MHz were seen as the direct expansion of similar fine structure (as fibers or “herringbone” structure) in the decametric range observed with the Nançay and IZMIRAN spectrographs.

Chernov, G. P.; Kaiser, M. L.; Bougeret, J.-L.; Fomichev, V. V.; Gorgutsa, R. V.

2007-03-01

316

Broadband meter-wavelength observations of ionospheric scintillation  

NASA Astrophysics Data System (ADS)

Intensity scintillations of cosmic radio sources are used to study astrophysical plasmas like the ionosphere, the solar wind, and the interstellar medium. Normally, these observations are relatively narrow band. With Low-Frequency Array (LOFAR) technology at the Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) station in northern Finland we have observed scintillations over a three-octave bandwidth. "Parabolic arcs," which were discovered in interstellar scintillations of pulsars, can provide precise estimates of the distance and velocity of the scattering plasma. Here we report the first observations of such arcs in the ionosphere and the first broadband observations of arcs anywhere, raising hopes that study of the phenomenon may similarly improve the analysis of ionospheric scintillations. These observations were made of the strong natural radio source Cygnus-A and covered the entire 30-250 MHz band of KAIRA. Well-defined parabolic arcs were seen early in the observations, before transit, and disappeared after transit although scintillations continued to be obvious during the entire observation. We show that this can be attributed to the structure of Cygnus-A. Initial results from modeling these scintillation arcs are consistent with simultaneous ionospheric soundings taken with other instruments and indicate that scattering is most likely to be associated more with the topside ionosphere than the F region peak altitude. Further modeling and possible extension to interferometric observations, using international LOFAR stations, are discussed.

Fallows, R. A.; Coles, W. A.; McKay-Bukowski, D.; Vierinen, J.; Virtanen, I. I.; Postila, M.; Ulich, Th.; Enell, C.-F.; Kero, A.; Iinatti, T.; Lehtinen, M.; Orispää, M.; Raita, T.; Roininen, L.; Turunen, E.; Brentjens, M.; Ebbendorf, N.; Gerbers, M.; Grit, T.; Gruppen, P.; Meulman, H.; Norden, M. J.; de Reijer, J.-P.; Schoenmakers, A.; Stuurwold, K.

2014-12-01

317

Radio Astronomy Radio astronomy  

E-print Network

Effelsberg 100m telescope (Germany) Green Bank 100m telescope (National Radio Astronomy ObservatoryExperiment -10m (Chile, Europe) #12;Submillimeter radio astronomy #12;Size of telescope Snow sweep at Nobeyama 45;#12;Arecibo 300m telescope #12;Radio interferometer #12;Radio interferometer Very Large Array (VLA) (New

Metchev, Stanimir

318

Unusual stripes in emission and absorption in solar radio bursts: Ropes of fibers in the meter wave band  

NASA Astrophysics Data System (ADS)

Based on data from the spectrographs of IZMIRAN and Tremsdorf station (Astronomical Institute, Potsdam), we analyze the ropes of narrow-band fibers in the spectra of solar radio bursts in the meter wave band by invoking events of satellite data (SOHO/LASCO, EIT, MDI) for the analysis. We consider in detail basic properties of the ropes in four events in comparison with previously known data. The fibers in ropes are more commonly observed with an overlap in time and frequency, but occasionally (more often at the end of the ropes) they can follow with a separation in time. The fiber duration and recurrence period seldom remain stable and, in general, increase from 0.3 0.5 s at the beginning to several seconds at the end of the rope. The relative values of the instantaneous and total fiber frequency bandwidths change only slightly in different events; ? f / f ? 0.003 0.005 and ? f / f ? 0.02 0.03. Most of the ropes exhibit a low-frequency absorption. The fibers in ropes are similar to ordinary intermediate drift bursts (fiber bursts), but they drift in a narrow frequency band and have a more frequent recurrence in some events. The ropes of fibers are usually observed in the time interval when the shock front catches up with the leading edge of a coronal mass ejection. Under the condition of a unified approach to interpreting the ropes of fibers in all events, their basic properties can be explained in terms of the model of fiber bursts. The connection of fibers with the developed zebra pattern is shown within the framework of a unified approach to the formation theory of stripes in emission and absorption in the model on whistlers.

Chernov, G. P.

2008-07-01

319

A Challenging Solar Eruptive Event of 18 November 2003 and the Causes of the 20 November Geomagnetic Superstorm. II. CMEs, Shock Waves, and Drifting Radio Bursts  

NASA Astrophysics Data System (ADS)

We continue our study (Grechnev et al., 2013, doi:10.1007/s11207-013-0316-6; Paper I) on the 18 November 2003 geoffective event. To understand possible impact on geospace of coronal transients observed on that day, we investigated their properties from solar near-surface manifestations in extreme ultraviolet, LASCO white-light images, and dynamic radio spectra. We reconcile near-surface activity with the expansion of coronal mass ejections (CMEs) and determine their orientation relative to the earthward direction. The kinematic measurements, dynamic radio spectra, and microwave and X-ray light curves all contribute to the overall picture of the complex event and confirm an additional eruption at 08:07 - 08:20 UT close to the solar disk center presumed in Paper I. Unusual characteristics of the ejection appear to match those expected for a source of the 20 November superstorm but make its detection in LASCO images hopeless. On the other hand, none of the CMEs observed by LASCO seem to be a promising candidate for a source of the superstorm being able to produce, at most, a glancing blow on the Earth's magnetosphere. Our analysis confirms free propagation of shock waves revealed in the event and reconciles their kinematics with "EUV waves" and dynamic radio spectra up to decameters.

Grechnev, V. V.; Uralov, A. M.; Chertok, I. M.; Slemzin, V. A.; Filippov, B. P.; Egorov, Y. I.; Fainshtein, V. G.; Afanasyev, A. N.; Prestage, N. P.; Temmer, M.

2014-04-01

320

A mid-latitude scintillation model  

NASA Astrophysics Data System (ADS)

Radiowave scintillation in the presence of ionospheric disturbances has the potential to disrupt numerous transionospheric radio and radar systems. This report describes development of a model characterizing the plasma density irregularities that produce scintillation in the naturally disturbed mid latitude F layer. The model will be incorporated into Program WBMOD, which includes subroutines for computing both link geometry and scintillation indices, the latter by means of phase screen diffraction theory. Earlier versions of WBMOD, were based on extensive analysis of scintillation data collected in the auroral and equatorial zones in Wideband Satellite Mission. The model described herein is based on similarly extensive analysis of Wideband data from one mid latitude station and of data collected from HiLat satellite at another mid latitude station. The model describes irregularities at an effective height of 350 km that are isotropic across the geomagnetic field and elongated by a factor of 10 along the field and whose one-dimensional spatial power spectrum obeys a single regime power law with a (negative) spectral index of 1.5. The height-integrated spectral strength of the irregularities is modeled as a function apex latitude of the point. The report highlights a disagreement by a factor of approximately three between irregularity strength inferred from the two satellites in a region of overlap between the two mid-latitude stations.

Robins, Robert E.; Secan, James A.; Fremouw, E. J.

1986-10-01

321

Method for calculating certain characteristics of radio-wave propagation using inclination angles of plasma-frequency isolines  

Microsoft Academic Search

The paper describes a method for calculating azimuthal deviations and Doppler frequency shifts in the ionosphere on the basis of inclination angles of plasma-frequency isolines. The method is applicable to ionospheric radio lines under the effect of traveling ionospheric disturbances moving at an angle of 90 deg to the radio-line direction.

G. N. Nosova

1985-01-01

322

Gravitational Interstellar Scintillation  

E-print Network

Gravitation could modulate the interstellar scintillation of pulsars in a way that is analogous to refractive interstellar scintillation (RISS). While RISS occurs when a large ionized cloud crosses the pulsar line-of-sight, gravitational interstellar scintillation (GISS) occurs when a compact gravitational deflector lies very near to that line-of-sight. However, GISS differs from RISS in at least two important respects: It has a very distinctive and highly predictible time signature, and it is non-dispersive. We find two very different astronomical contexts where GISS could cause observable diffraction-pattern distortions: Highly inclined binary pulsars, and the kind of compact interstellar clouds suspected of causing extreme scattering events.

Redouane Al Fakir

2008-05-23

323

Wavelength reuse for uplink on dense wave-division multiplexing single-fiber ring for radio over fiber broadband systems with downlink signal generation in optical domain  

NASA Astrophysics Data System (ADS)

We have presented a single-fiber dense wave-division multiplexing (DWDM) ring scheme with wavelength reuse for uplink and optical signal generation for downlink. Instead of using a new laser for uplink, the wavelength already used for wavelength beating to generate the downlink signal in optical domain is reused for uplink. Algorithms for power optimization using Erbium-doped fiber amplifier, wavelength routing, and wavelength assignment are developed and simulated. The DWDM-radio over fiber scheme reusing the wavelength can support the data rate in the range of 1 Gbps. Fifteen remote antenna units (RAUs) are simulated in this scheme; however, these can be increased by adding more wavelengths. The proposed scheme simplifies the architecture or RAUs, decreases the overall cost while enhancing the bandwidth and operational flexibility of radio over fiber systems.

Mumtaz, Ateeq; Khawar Islam, Muhammad; Zafrullah, Muhammad

2011-10-01

324

Characterization of ionospheric amplitude scintillations using wavelet entropy detrended GNSS data  

NASA Astrophysics Data System (ADS)

The extensive monitoring networks of Global Navigation Satellite System (GNSS) ionospheric scintillation have been established to continuously log observation data. Further, the amplitude scintillation index and the phase scintillation index, which are derived from scintillation observations, are anticipated to accommodate the accuracy requirement of both the user level and the monitoring station level. However, raw scintillation observations essentially measure superposed waveform impairments of GNSS signals propagating through ionosphere and troposphere. It implies that fluctuations of raw scintillation observations are caused by multiple factors from the entire radio propagation environment. Hence, it is crucial to characterize ionospheric scintillations from GNSS observation data. And the characterization is implemented through extracting fluctuations of raw observations merely induced by ionospheric scintillations. Designed to address this problem by means of Fourier filtering detrending, the present work investigates the influence of varying detrending cutoff frequencies on wavelet statistical energy and wavelet entropy distributions of scintillation data. It consequently derives criteria on the optimum detrending cutoff frequency for three types of raw amplitude scintillation data, which are classified by their wavelet energy distributions. Results of the present work verify that detrending with specific optimum cutoff frequencies rather than the fixed and universally applicable one renders the validity and credibility of characterizing ionospheric scintillations as the part of GNSS observation fluctuations purely induced by ionosphere electron density irregularities whose scale sizes are comparable with or smaller than the Fresnel scale.

Su, Yongqing; Liu, Hao; Yue, Jiguang; Yang, Yunfan

2014-12-01

325

Radio Galaxies.  

ERIC Educational Resources Information Center

Provides background information on radio galaxies. Topic areas addressed include: what produces the radio emission; radio telescopes; locating radio galaxies; how distances to radio galaxies are found; physics of radio galaxies; computer simulations of radio galaxies; and the evolution of radio galaxies with cosmic time. (JN)

Downes, Ann

1986-01-01

326

The detection of the ionospheric irregularities by GNSS signal and the incoherent scatter radio measurements  

NASA Astrophysics Data System (ADS)

The high-latitude ionosphere has a very complicated structure and high dynamics. The ionospheric irregularities can produce scintillations of radio waves that occur predominantly in the ionosphere F-layer. The strong fluctuations can influence on the performance of the different space communication and navigation radio systems. The fluctuations of GPS/GLONASS signals are caused by the ionospheric irregularities with spatial dimensions more than 10 km. These structures can be detected by high potential incoherent scatter radars. It was proposed and carried out at the beginning of June 2012 experiment for a detailed study of the nature of the ionospheric irregularities, influencing on GPS/GLONASS signals parameters, by incoherent scatter and trans-ionospheric radio measurements simultaneously. The EISCAT facilities position provides the unique opportunity to study the ionospheric irregularities' parameters associated with TEC fluctuations and GPS/GLONASS signals scintillations. The EISCAT heating facility provides unique possibility to generate the artificial ionospheric irregularities and to estimate the impact factor of these irregularities on GPS/GLONASS signals transionospheric propagation. In order to detect the ionosphere irregularities it is used the IS radar measurements (electron density and plasma temperatures profiles) and simultaneously registered on EISCAT site amplitude and phase fluctuations in GPS/GLONASS signals by use of the Javad multi-constellation GPS/GLONASS receiver with high samples rate (100 Hz) and special scintillation GPS receiver PolaRxS PRO that dedicated to ionospheric monitoring and space weather applications and provides TEC and S4 scintillation index measurements. The low frequency fluctuations can be directly measured due to the electron density changes along the radio ray path between a GPS/GLONASS satellite and a ground-based receiver on EISCAT site. The raw data (under scintillating conditions) obtained by use of the high samples rate GPS/GLONASS receiver are processed in order to derive the scintillation parameters. The practical aspect of this investigation is a detailed study of nature and impact level of the ionospheric irregularities that can influence on the GPS/GLONASS performance especially at high latitudes and during geomagnetically disturbed period and to obtain new knowledge that may improve the reliability of the global navigation systems in Arctic and Antarctic regions. The authors are grateful to the EISCAT Scientific Association for observing time on the EISCAT facilities within the framework of Peer-reviewed Program.

Cherniak, Iurii; Shagimuratov, Irk; Krankowski, Andrzej; Sieradsky, Rafal; Zakharenkova, Irina; Rietveld, Michael; Kapcia, Jacek

2013-04-01

327

Radio waves detect anomalies  

Microsoft Academic Search

A recent development in medium frequency electromagnetic tomography has been successful in plotting changes in seam heights in mines in eastern and western coalfields. Tomography is the technique of making radiographs of plane sections of a body or object; its purpose is to show detail of a predetermined plane of the body, while blurring the images of structures in other

1986-01-01

328

A statistical study of inertia gravity waves in the troposphere based on the measurements of Wuhan Atmosphere Radio Exploration (WARE) radar  

NASA Astrophysics Data System (ADS)

atmosphere radio exploration (WARE) radar is the first mesosphere-stratosphere-troposphere radar to have become operative in the mainland of China and is dedicated to real-time atmospheric observations. Based on the WARE radar data collected for the period from September 2011 to February 2013, 2666 downward and 1735 upward inertia gravity waves (IGWs) are identified from three-dimensional (3-D) wind fields observed in the troposphere and subsequently analyzed in a statistical manner. Wave characteristics including intrinsic frequencies, vertical wavelengths, horizontal wavelengths, vertical wave number spectra, energy density spectra, and wave sources are investigated using a combination of the Lomb-Scargle spectral analysis, the quasi-monochromatic gravity waves model, and the hodograph method. Our results demonstrate that the characteristic parameters of upward and downward tropospheric IGWs are not significantly different. These results indicate that the tropospheric IGWs parameters are not directly correlated with propagation directions. Combining with the information of statistical 3-D wind field and some climatic characteristics of Hubei Province, atmospheric moist convection will contribute most in summer, whereas jet/front systems will contribute most in winter. One may expect seasonal variations to be tied to the varying importance of these sources.

Qing, Haiyin; Zhou, Chen; Zhao, Zhengyu; Chen, Gang; Ni, Binbin; Gu, Xudong; Yang, Guobin; Zhang, Yuannong

2014-04-01

329

Study of Compact Radio Galaxies in the 7C II Field  

NASA Astrophysics Data System (ADS)

26 radio galaxies in field II of the Cambridge 7C list which scintillate at 102 MHz are studied in detail to clarify the major physical and structural features of these extragalactic radio sources. The results are compared with data for scintillating quasars in the same field.

Abrahamyan, H. V.; Andreasyan, R. R.; Hovhannisyan, M. A.; Paronyan, G. M.

2014-09-01

330

Radio frequency pressure transducer  

Microsoft Academic Search

A novel system is reported here for the pressure measurement at microwave and millimetre-wave frequencies. This method consists in using a radio frequency transducer based on RF resonator. Accurate determination of the pressure is expected.

M. M. Jatlaoui; P. Pons; H. Aubert

2007-01-01

331

The Radio Universe  

NSDL National Science Digital Library

The Radio Universe website provides a brief introduction the electromagnetic radiation, HII regions, the structure of the Milky Way galaxy, and quasars as seen by radio wave observations. The site also contains an expliantion of the doppler effect and 21 cm line.

2005-06-07

332

Radio Transmission Measurements  

Microsoft Academic Search

The paper divides naturally into three sections. The first section briefly analyses the radio transmission circuit into (a) the sending or radiating portion, (b) the transmitting portion consisting of the ether path thru which the radiated waves travel, and (c) the receiving portion. The relation of these from the standpoint of the radio transmission engineer is discussed, pointing out the

R. Bown; C. R. Englund; H. T. Friis

1923-01-01

333

A refracting radio telescope  

Microsoft Academic Search

Observations of extraterrestrial radio sources at the lower end of the radio frequency spectrum are limited by reflection of waves from the topside ionosphere and by the large size of antenna apertures necessary for the realization of narrow beamwidths. The use of the ionosphere as a lens is considered. The lens is formed by the release of chemicals such as

Paul Bernhardt; A. V. da Rosa

1977-01-01

334

A full-duplex multiband access radio-over-fiber link with frequency multiplying millimeter-wave generation and wavelength reuse for upstream signal  

NASA Astrophysics Data System (ADS)

A full-duplex radio-over-fiber (RoF) link providing multiband wireless accesses including 20 GHz, 40 GHz and 60 GHz millimeter (mm)-wave signal using a 10 GHz RF signal source is proposed. According to our theoretical analysis and simulation of the transmission performance of the signal along the single mode fiber, the code form distortion caused by the sideband walk-off effect due to the fiber chromatic dispersion can be eliminated, and the degradation caused by the fading effect on the down-stream signal is removed by adjusting the relative phase shift between the two sidebands. The upstream signal carried by the optical carrier abstracted from the downlink signal is also immune to the code outline distortion. The numerical simulation results show that the 20 km full-duplex RoF link with our generated optical mm-wave signal maintains good performance.

Ma, Jianxin; Li, Yanjie

2015-01-01

335

Laboratory studies on the removal of radon-born lead from KamLAND's organic liquid scintillator  

NASA Astrophysics Data System (ADS)

The removal of radioactivity from liquid scintillator has been studied in preparation of a low background phase of KamLAND. This paper describes the methods and techniques developed to measure and efficiently extract radon decay products from liquid scintillator. We report the radio-isotope reduction factors obtained when applying various extraction methods. During this study, distillation was identified as the most efficient method for removing radon-born lead from liquid scintillator.

Keefer, G.; Grant, C.; Piepke, A.; Ebihara, T.; Ikeda, H.; Kishimoto, Y.; Kibe, Y.; Koseki, Y.; Ogawa, M.; Shirai, J.; Takeuchi, S.; Mauger, C.; Zhang, C.; Schweitzer, G.; Berger, B. E.; Dazeley, S.; Decowski, M. P.; Detwiler, J. A.; Djurcic, Z.; Dwyer, D. A.; Efremenko, Y.; Enomoto, S.; Freedman, S. J.; Fujikawa, B. K.; Furuno, K.; Gando, A.; Gando, Y.; Gratta, G.; Hatakeyama, S.; Heeger, K. M.; Hsu, L.; Ichimura, K.; Inoue, K.; Iwamoto, T.; Kamyshkov, Y.; Karwowski, H. J.; Koga, M.; Kozlov, A.; Lane, C. E.; Learned, J. G.; Maricic, J.; Markoff, D. M.; Matsuno, S.; McKee, D.; McKeown, R. D.; Miletic, T.; Mitsui, T.; Motoki, M.; Nakajima, Kyo; Nakajima, Kyohei; Nakamura, K.; O`Donnell, T.; Ogawa, H.; Piquemal, F.; Ricol, J.-S.; Shimizu, I.; Suekane, F.; Suzuki, A.; Svoboda, R.; Tajima, O.; Takemoto, Y.; Tamae, K.; Tolich, K.; Tornow, W.; Watanabe, Hideki; Watanabe, Hiroko; Winslow, L. A.; Yoshida, S.

2015-01-01

336

Signatures and Characteristics of Internal Gravity Waves in the Venus' and Mars' Atmospheres as Revealed by the Radio Occultation Temperature Data Analysis  

NASA Astrophysics Data System (ADS)

It is well known that internal gravity waves (IGWs) affect the structure and mean circulation of the Earth' middle and upper atmosphere by transporting energy and horizontal momentum upward from the lower atmosphere. The IGWs modulate the background atmospheric structure, producing a periodic pattern of spatial and temporal 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. For instance, Yakovlev et al. (1991) and Gubenko et al. (2008a) used the radio occultation (RO) data from Venera 15 and 16 missions to investigate the thermal structure and layering of the Venus' middle atmosphere. They noted that a wavelike periodic structure commonly appears in retrieved vertical profiles at altitudes above 60 km in the atmosphere where the static stability is large. Through comparisons between Magellan RO observations in the Venus' atmosphere, Hinson and Jenkins (1995) have demonstrated that small scale variations in retrieved temperature profiles at altitudes from 60 to 90 km are caused by a spectrum of vertical propagating IGWs. Temperature profiles from the Mars Global Surveyor (MGS) measurements reveal vertical wavelike structures assumed to be atmospheric IGWs in the Mars' lower atmosphere (Creasey et al., 2006). The very large IGW amplitudes inferred from MGS RO data imply a very significant role for IGWs in the atmospheric dynamics of Mars as well. There is one general problem inherent to all measurements of IGWs. Observed wavelike variations may alternatively be caused by the IGWs, turbulence or persistent layers in the atmosphere, and it is necessary to have an IGW identification criterion for the correct interpretation of obtained results. In this context, we have developed an original method for the determination of internal gravity wave parameters from a single vertical temperature profile measurement in a planetary atmosphere (Gubenko et al., 2008b, 2011). 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 amplitude thresholds of the wave temperature field and on the linear IGW saturation theory in which amplitude thresholds are restricted by dynamical (shear) instability processes in the atmosphere. When the amplitude of an internal wave reaches the shear instability limit, energy is assumed to be dissipated in such a way that the amplitude is maintained at the instability limit as the wave propagates upwards. An application of the developed method to the RO temperature data has given the possibility to identify the IGWs in the Venus' and Mars' atmospheres and to determine the magnitudes of key wave parameters such as the intrinsic frequency, amplitudes of vertical and horizontal perturbations of the wind velocity, vertical and horizontal wavelengths, intrinsic vertical and horizontal phase (and group) speeds, kinetic and potential energy, vertical fluxes of the wave energy and horizontal momentum. The obtained results of internal wave studies in the Venus' and Mars' atmospheres deduced from the Magellan and MGS RO temperature profiles are presented and discussed. This work was partially supported by the RFBR Grant (No. 10-02-01015-a) and program OFN-15 of the Russian Academy of Sciences. References Creasey, J. E., Forbes, J. M., and Hinson, D. P.: Global and seasonal distribution of gravity wave activity in Mars' lower atmosphere derived from MGS radio occultation data, Geophys. Res. Lett., 33, L01803, doi: 10.1029/2005GL024037, 2006. Gubenko, V.N., Andreev, V.E., and Pavelyev, A.G.: Detection of layering in the upper cloud layer of Venus northern polar atmosphere observed from radio occultation data, J. Geophys. Res., 113, E03001, doi:10.1029/2007

Gubenko, Vladimir; Pavelyev, Alexander; Andreev, Vitali; Salimzyanov, Rishat; Pavelyev, Alexey

2012-07-01

337

Equatorial scintillations - A review  

NASA Technical Reports Server (NTRS)

Scintillation observations of equatorial irregularities by techniques such as in situ, radar backscatter, airglow, and total electron content are reviewed, with an emphasis on GHz measurements. New aspects of the spread-F analysis from ionograms are mentioned, followed by a discussion of scintillation morphology, and the longitudinal control of the equatorial scintillations is emphasized. A coordinated multitechnique observation of the equatorial irregularities is described in detail, the study being divided into two parts: (1) an examination of the large field-aligned irregularity structures and their association with discrete patches of scintillation activity, and (2) an investigation of the coexistence of km-scale-irregularities with meter scales and a description of the evolution of the irregularity and scintillation spectra during the various phases of irregularity generation and decay. Unsolved problems are also reviewed, e.g., it is stated that the effects of steep spatial gradients in the electron density structures and their subsequent erosion on both CW and pulse propagation need to be evaluated both from the point of view of theory and experiments.

Basu, S.; Basu, S.

1981-01-01

338

CME Propagation Characteristics from Radio Observations  

E-print Network

We explore the relationship among three coronal mass ejections (CMEs), observed on 28 October 2003, 7 November 2004, and 20 January 2005, the type II burst-associated shock waves in the corona and solar wind, as well as the arrival of their related shock waves and magnetic clouds at 1 AU. Using six different coronal/interplanetary density models, we calculate the speeds of shocks from the frequency drifts observed in metric and decametric radio wave data. We compare these speeds with the velocity of the CMEs as observed in the plane-of-the-sky white-light observations and calculated with a cone model for the 7 November 2004 event. We then follow the propagation of the ejecta using Interplanetary Scintillation (IPS) measurements, which were available for the 7 November 2004 and 20 January 2005 events. Finally, we calculate the travel time of the interplanetary (IP) shocks between the Sun and Earth and discuss the velocities obtained from the different data. This study highlights the difficulties in making velo...

Pohjolainen, S; Culhane, J L; Manoharan, P K; Elliott, H A

2007-01-01

339

CME Propagation Characteristics from Radio Observations  

E-print Network

We explore the relationship among three coronal mass ejections (CMEs), observed on 28 October 2003, 7 November 2004, and 20 January 2005, the type II burst-associated shock waves in the corona and solar wind, as well as the arrival of their related shock waves and magnetic clouds at 1 AU. Using six different coronal/interplanetary density models, we calculate the speeds of shocks from the frequency drifts observed in metric and decametric radio wave data. We compare these speeds with the velocity of the CMEs as observed in the plane-of-the-sky white-light observations and calculated with a cone model for the 7 November 2004 event. We then follow the propagation of the ejecta using Interplanetary Scintillation (IPS) measurements, which were available for the 7 November 2004 and 20 January 2005 events. Finally, we calculate the travel time of the interplanetary (IP) shocks between the Sun and Earth and discuss the velocities obtained from the different data. This study highlights the difficulties in making velocity estimates that cover the full CME propagation time.

S. Pohjolainen; L. van Driel-Gesztelyi; J. L. Culhane; P. K. Manoharan; H. A. Elliott

2007-11-20

340

Millisecond Pulsar Scintillation Studies with LOFAR: Initial Results  

NASA Astrophysics Data System (ADS)

High-precision timing of millisecond pulsars (MSPs) over years to decades is a promising technique for direct detection of gravitational waves at nanohertz frequencies. Time-variable, multi-path scattering in the interstellar medium is a significant source of noise for this detector, particularly as timing precision approaches 10 ns or better for MSPs in the pulsar timing array. For many MSPs, the scattering delay above 1 GHz is at the limit of detectability; therefore, we study it at lower frequencies. Using the LOw-Frequency ARray (LOFAR) radio telescope, we have analyzed short (5-20 minutes) observations of 3 MSPs in order to estimate the scattering delay at 110-190 MHz, where the number of scintles is large and, hence, the statistical uncertainty in the scattering delay is small. We used cyclic spectroscopy, still relatively novel in radio astronomy, on baseband-sampled data to achieve unprecedented frequency resolution while retaining adequate pulse-phase resolution. We detected scintillation structure in the spectra of the MSPs PSR B1257+12, PSR J1810+1744, and PSR J2317+1439 with diffractive bandwidths of 6 ± 3, 2.0 ± 0.3, and ~7 kHz, respectively, where the estimate for PSR J2317+1439 is reliable to about a factor of two. For the brightest of the three pulsars, PSR J1810+1744, we found that the diffractive bandwidth has a power-law behavior ??dvprop??, where ? is the observing frequency and ? = 4.5 ± 0.5, consistent with a Kolmogorov inhomogeneity spectrum. We conclude that this technique holds promise for monitoring the scattering delay of MSPs with LOFAR and other high-sensitivity, low-frequency arrays like the low-frequency component of the Square Kilometre Array.

Archibald, Anne M.; Kondratiev, Vladislav I.; Hessels, Jason W. T.; Stinebring, Daniel R.

2014-08-01

341

Wave represents displacement Wave represents pressure Source -Sound Waves  

E-print Network

Wave represents displacement Wave represents pressure Source - Sound Waves Distance between crests students connect physics to the real world. The representation of sound in the Sound Waves simulation. The Sound Waves simulation becomes the source of an analogical mapping to Radio Waves. Concepts

Colorado at Boulder, University of

342

Kinematics of ICMEs Deduced From Remote Radio Observations  

NASA Astrophysics Data System (ADS)

Low-frequency radio emissions, generated at the driven shock wave at the fundamental and harmonic of the plasma frequency, can directly reveal the kinematics of ICMEs as they propagate through the inner heliosphere. The reason is that the frequency of the radio emissions varies in a predictable way as a function of heliocentric distance. Hence, the observed frequency drift of these radio emissions is essentially a plot of the height above the Sun as a function of time. The derivative of the observed frequency-time curve at each point then gives the instantaneous speed of the propagating interplanetary shock. We have used these remote radio observations to determine the speed profiles for some 40 fast CMEs observed during solar cycle 23. The speed profiles for these fast ICMEs were found to imply an initial rapid deceleration at a constant rate, followed by a constant propagation speed to 1 AU (Reiner et al. ApJ 663, 1369, 2007), consistent with some earlier Doppler scintillation measurements (Woo et al., JGR 90, 154, 1985). Because of the large number of CME events for which this analysis was carried out, we were further able to study the correlations of the deceleration parameters of the ICME speed profiles. For most of those remote radio observations, there were no corresponding white-light observations beyond the 32 Rs (0.15 AU) limit of the LASCO coronagraph. After 2003, the all-sky camera SMEI permitted the first direct comparison between the remote radio and the white-light observations in interplanetary space (Reiner et al. JGR 110, A09S14, 2005). The STEREO spacecraft, launched in October of 2006, provide a new and unique opportunity to make direct comparisons between the radio and white-light observations of the ICME kinematics. The STEREO observations also allow the locations of the radio sources along the shock front to be directly deduced from two or three spacecraft triangulation measurement from STEREO and Wind (Reiner et al. Solar Physics 10.1007/s11207-009-9404-z, 2009). However, due to solar minimum, to date no CMEs observed by STEREO were fast enough to produce measurable radio emissions. As we approach solar maximum that situation will surely change. Nevertheless, some height-time data for fast CMEs that were observed in the Heliospheric Imagers on STEREO do seem to confirm the general characteristics of the speed profile previously deduced from radio tracking (Wood et al., ApJ 694, 707, 2009). In this talk, we will summarize our previous remote radio results, and show how they can be used to provide improved algorithms for space weather predictions.

Reiner, M. J.; MacDowall, R. J.

2009-12-01

343

Experimental investigation of ULF/VLF radio wave generation and propagation in the upper atmosphere and ionosphere during EISCAT heating experiment in 2012  

NASA Astrophysics Data System (ADS)

Powerful high frequency radio waves transmitted from high-power HF heating facilities modify the ionospheric plasma. The X-mode HF pump wave generates strong small-scale artificial field aligned irregularities in the F region of the ionosphere when the heater frequency is near or above the critical frequency of F2 layer [Blagoveshchenskaya et al]. One of the tasks of the Russian EISCAT heating campaign in February 2012 was an investigation of the generation and propagation of ULF/VLF signals generated as the result of HF radiation modulation. Despite the numerous attempts of long-range detection of such signals, there are a few successful results. The most reliable and important results were obtained by [Barr et al.] more than 20 years ago. They measured the VLF radio waves in Lindau, Germany at the distance of about 2000 km from EISCAT Heater. We present the results of the ULF/VLF registrations at the same distance during heating campaign of February 2012. The measurements were conducted at Mikhnevo Geohysical Observatory located in 80 km to the south of Moscow and at the distance of about 1900 km from Tromsø. For measurements were used a sensitive receivers with crossed air-coil loop antennas in the frequency range from 800 Hz to 30 kHz in the femtotesla amplitude range. We recorded the radial and azimuthal magnetic component of the signals and from their ratio obtained the mode polarization. The radiated heater frequency was modulated by 517, 1017, 2017, 3017, 4017 and 6017 Hz. It was shown the signals with frequency less than 2 kHz propagate in the QTEM mode, and signals at the frequency from 2 to 4 kHz are in the QTE mode. Observed magnetic field strengths and waveguide polarizations are found to be in line with the predictions of simple waveguide models. Qualitative coincidence of the signals polarization character and its dependence on the frequency specifies adequacy of numerical models and reliability of the data received in campaign 2012. Blagoveshchenskaya N. F., M. T. Rietveld et al. Artificial field-aligned irregularities in the high-latitude F region of the ionosphere induced by an X-mode HF heater wave. // Geophys. Res. Lett. - 2011. V. 38, doi: 10.1029/2011GL046724. Barr, R., P. Stubbe, and H. Kopka, 1991, Long-range detection of VLF radiation produced by heating the auroral electrojet. Radio Science, Volume 26, Number 4, Pages 871-879, July-August 1991

Ryakhovskiy, Iliya; Gavrilov, Boris; Zetzer, Julius; Rietveld, Michael; Poklad, Yuriy; Blagoveshchenskaya, Nataly

344

Scintillator Strip ECAL Optimization  

E-print Network

The CALICE collaboration is developing a granular electromagnetic calorimeter using small scintillator strips for a future linear collider experiment. On developing of ~ 10^7 channel-ECAL in particle flow approach, CALICE is developing a technological prototype with 144 of 5 x 45 x (1 - 2) mm^3 strips on each 180 x 180 mm^2 base board unit in tandem with developing the design of scintillator strip and pixelated photon detector and their coupling after established the physics prototype which has required performance. A method of event reconstruction in such ECAL is also developed.

Katsushige Kotera

2014-04-07

345

An alternative to the plasma emission model: Particle-in-cell, self-consistent electromagnetic wave emission simulations of solar type III radio bursts  

SciTech Connect

High-resolution (sub-Debye length grid size and 10 000 particle species per cell), 1.5D particle-in-cell, relativistic, fully electromagnetic simulations are used to model electromagnetic wave emission generation in the context of solar type III radio bursts. The model studies generation of electromagnetic waves by a super-thermal, hot beam of electrons injected into a plasma thread that contains uniform longitudinal magnetic field and a parabolic density gradient. In effect, a single magnetic line connecting Sun to Earth is considered, for which five cases are studied. (i) We find that the physical system without a beam is stable and only low amplitude level electromagnetic drift waves (noise) are excited. (ii) The beam injection direction is controlled by setting either longitudinal or oblique electron initial drift speed, i.e., by setting the beam pitch angle (the angle between the beam velocity vector and the direction of background magnetic field). In the case of zero pitch angle, i.e., when v-vector{sub b{center_dot}}E-vector{sub perpendicular}=0, the beam excites only electrostatic, standing waves, oscillating at local plasma frequency, in the beam injection spatial location, and only low level electromagnetic drift wave noise is also generated. (iii) In the case of oblique beam pitch angles, i.e., when v-vector{sub b{center_dot}}E-vector{sub perpendicular}=0, again electrostatic waves with same properties are excited. However, now the beam also generates the electromagnetic waves with the properties commensurate to type III radio bursts. The latter is evidenced by the wavelet analysis of transverse electric field component, which shows that as the beam moves to the regions of lower density and hence lower plasma frequency, frequency of the electromagnetic waves drops accordingly. (iv) When the density gradient is removed, an electron beam with an oblique pitch angle still generates the electromagnetic radiation. However, in the latter case no frequency decrease is seen. (v) Since in most of the presented results, the ratio of electron plasma and cyclotron frequencies is close to unity near the beam injection location, in order to prove that the electromagnetic emission, generated by the non-zero pitch angle beam, oscillates at the plasma frequency, we also consider a case when the magnetic field (and the cyclotron frequency) is ten times smaller. Within the limitations of the model, the study presents the first attempt to produce synthetic (simulated) dynamical spectrum of the type III radio bursts in the fully kinetic plasma model. The latter is based on 1.5D non-zero pitch angle (non-gyrotropic) electron beam that is an alternative to the plasma emission classical mechanism for which two spatial dimensions are needed.

Tsiklauri, David [Astronomy Unit, School of Mathematical Sciences, Queen Mary University of London, Mile End Road, London E1 4NS (United Kingdom)

2011-05-15

346

An Introduction to Radio Astronomy  

NASA Astrophysics Data System (ADS)

Preface; 1. Introduction; 2. The nature of the radio signal; 3. Signals, noise, radiometers and spectrometers; 4. Single-aperture radio telescopes; 5. The two-element interferometer; 6. Aperture synthesis; 7. Radiation, propagation and absorption of radio waves; 8. The local universe; 9. The interstellar medium; 10. Galactic dynamics; 11. Stars; 12. Pulsars; 13. Radio galaxies and quasars; 14. Cosmology fundamentals; 15. The angular structure of the CMB; 16. Cosmology: discrete radio sources and gravitational lensing; 17. The future of radio astronomy; Appendixes; References; Index.

Burke, Bernard F.; Graham-Smith, Francis

2014-02-01

347

Polysiloxane scintillator composition  

DOEpatents

A plastic scintillator useful for detecting ionizing radiation comprising a matrix which comprises an optically transparent polysiloxane having incorporated therein at least one ionizing radiation-hard fluor capable of converting electromagnetic energy produced in the polysiloxane upon absorption of ionizing radiation to detectable light.

Walker, James K. (Gainesville, FL)

1992-01-01

348

Polysiloxane scintillator composition  

DOEpatents

A plastic scintillator useful for detecting ionizing radiation comprising a matrix which comprises an optically transparent polysiloxane having incorporated therein at least one ionizing radiation-hard fluor capable of converting electromagnetic energy produced in the polysiloxane upon absorption of ionizing radiation to detectable light.

Walker, J.K.

1992-05-05

349

Scanning type scintillation camera  

SciTech Connect

The effective area of observation of a scanning-type scintillation camera is expanded relative to the actual area scanned by shifting the position of a spatial window back and forth in the direction of scanning so that the sum of the window velocity and the velocity of actual scanning represents a predetermined scanning velocity.

Nagasawa, Y.

1981-06-16

350

Scintillator requirements for medical imaging  

SciTech Connect

Scintillating materials are used in a variety of medical imaging devices. This paper presents a description of four medical imaging modalities that make extensive use of scintillators: planar x-ray imaging, x-ray computed tomography (x-ray CT), SPECT (single photon emission computed tomography) and PET (positron emission tomography). The discussion concentrates on a description of the underlying physical principles by which the four modalities operate. The scintillator requirements for these systems are enumerated and the compromises that are made in order to maximize imaging performance utilizing existing scintillating materials are discussed, as is the potential for improving imaging performance by improving scintillator properties.

Moses, William W.

1999-09-01

351

Trends in the characteristics of the annual and semiannual variations observed in the radio wave absorption in the lower ionosphere  

E-print Network

to the MLT region heights. Data from central and southeastern Europe are used. A consistent tendency tendency in the amplitude of the annual wave is questionable in the sense that the trend in the amplitude of both the annual and semiannual waves display a forward tendency, i.e. shift to an earlier time

Paris-Sud XI, Université de

352

Frequency characteristics of modification effects of high-power radio waves on the ionospheric F-layer  

Microsoft Academic Search

The paper presents experimental results concerning the effect of artificial ionospheric irregularities on the characteristics of linear-FM signals for vertical and oblique sounding of the ionosphere. The radio-transmitting facility operated at a frequency of 4.8 MHz with a power of 200 MW. The effects observed on the linear-FM ionograms are classified according to the effects of artificial irregularities of different

L. M. Erukhimov; V. A. Ivanov; N. A. Mitiakov; V. P. Uriadov; V. A. Frolov

1987-01-01

353

The 27-day versus 13.5-day variations in the solar Lyman-alpha radiation and the radio wave absorption in the lower ionosphere over Europe  

NASA Technical Reports Server (NTRS)

In order to clarify the question of solar periods in absorption, the pattern was studied of the solar Lyman-alpha radiation (the principal ionizing agent of the lower ionosphere) and of the radio wave absorption at five widely spaced places in Europe. When the solar Lyman-alpha flux variability is very well developed, then it dominates in the lower ionospheric variability. The most pronounced Lyman-alpha variation on time scale day-month is the solar rotation variation (about 27 days). When the Lyman-alpha variability is developed rather poorly, as it is typical for periods dominated by the 13.5 day variability, then the lower ionospheric variability appears to be dominated by variations of meteorological origin. The conclusions hold for all five widely spaced placed in Europe.

Delamorena, B. A.; Lastovicka, Jan; Rapoport, Z. TS.; Alberca, L.

1989-01-01

354

Pulsating Solar Radio Emission  

NASA Astrophysics Data System (ADS)

A status report of current research on pulsating radio emission is given, based on working group discussions at the CESRA 2004 workshop. Quasi-periodic pulsations have been observed at all wavelength ranges of the radio band. Usually, they are associated with flare events; however since the late 90s, pulsations of the slowly-varying component of the Sun’s radio emission have also been observed. Radio pulsations show a large variety in their periods, bandwidths, amplitudes, temporal and spatial signatures. Most of them have been attributed to MHD oscillations?dex waves!MHD waves in coronal loops, while alternative interpretations consider intrinsic oscillations of a nonlinear regime of kinetic plasma instabilities or modulation of the electron acceleration. Combined radio spectroscopic observations with radio imaging and X-ray/EUV data have revived interest in the subject. We summarize recent progress in using radio pulsations as a powerful tool for coronal plasma and magnetic field diagnostics. Also the latest developments on the study of the physical processes leading to radio emission modulation are summarized.

Nindos, Alexander; Aurass, Henry

355

Remote sensing and modeling of lightning caused long recovery events within the lower ionosphere using VLF/LF radio wave propagation  

NASA Astrophysics Data System (ADS)

On the 4 November 2012 at 3:04:27 UT a strong lightning in the midst of the North Sea affected the propagation conditions of VLF/LF transmitter radio signals from NRK (Iceland, 37.5 kHz) and GBZ (UK, 19.58 kHz) received at 5246° N 8° E (NW Germany). The amplitude and phase dips show a recovery time of 6-12 min pointing to a LOng Recovery Early VLF (LORE) event. Clear assignment of the causative return stroke in space and time was possible with data from the WWLLN (Worldwide Lightning Location Network). Based on a return stroke current model the electric field is calculated and an excess electron density distribution which decays over time in the lower ionosphere is derived. Ionization, attachment and recombination processes are modeled in detail. Entering the electron density distribution in VLF/LF radio wave propagation calculations using the LWPC (Long Wavelength Propagation Capability) code allows to model the VLF/LF amplitude and phase behavior by adjusting the return stroke current moment. The results endorse and quantify the conception of lower ionosphere EMP heating by strong - but not necessarily extremely strong - return strokes of both polarities.

Schmitter, E. D.

2014-11-01

356

EVIDENCE AGAINST THE OSCILLATING TWO-STREAM INSTABILITY AND SPATIAL COLLAPSE OF LANGMUIR WAVES IN SOLAR TYPE III RADIO BURSTS  

SciTech Connect

Recently Thejappa et al. studied a specific Langmuir wave packet observed by STEREO A and argued based on the electric field from one of the three antennas that this packet satisfied the conditions for the oscillating two-stream instability (OTSI) and was undergoing wave collapse. We analyze the same event using all three electric components and show that, while the wave packet has structure consistent with collapse simulations and theory, the field strength is well below that required for collapse to proceed. Analyzing the three electric field components shows that the power spectrum and dominance of wave power perpendicular to the local magnetic field are inconsistent with OTSI. We show that this packet and other more intense packets are inconsistent with collapse and show no evidence of OTSI, but are likely trapped eigenmodes in density wells. Therefore, OTSI and collapse are unlikely explanations for intense Langmuir events observed in the solar wind.

Graham, D. B.; Cairns, Iver H. [School of Physics, University of Sydney, New South Wales 2006 (Australia); Malaspina, D. M.; Ergun, R. E., E-mail: dgraham@physics.usyd.edu.au [Laboratory for Atmospheric and Space Physics, University of Colorado at Boulder, Boulder, CO (United States)

2012-07-01

357

Enhanced efficiency of PbWO4:Mo,Nb scintillator  

Microsoft Academic Search

The effect of Nb codoping on the optical properties of the PbWO4:Mo scintillator is investigated by radio- and thermoluminescence, scintillation decay, and light yield measurements. Steady-state radioluminescence efficiency of PbWO4:Mo,Nb with optimized doping concentrations (2750 and 350 molar ppm, respectively) becomes up to 20 times higher with respect to that of undoped PbWO4 and is comparable to that of Bi3Ge4O12.

M. Nikl; P. Bohacek; E. Mihokova; N. Solovieva; A. Vedda; M. Martini; G. P. Pazzi; P. Fabeni; M. Kobayashi; M. Ishii

2002-01-01

358

A mathematical analysis of the theory of interplanetary scintillation in the weak scattering approximation  

Microsoft Academic Search

A simplified analytical technique is presented for modeling the interplanetary scintillation of radio sources of finite angular size with a power-law electron-density-fluctuation power spectrum. The simplification results from the representation of the scintillation spectrum in confluent hypergeometric functions. The approximations presented allow fast numerical evaluation of a spectrum for a weakly scattering but extended medium with less than 10% error

D. G. Mitchell; E. C. Roelof

1976-01-01

359

Internal, nonperturbing, radio frequency wave monitor reflectometer system on the DIII-D tokamak (abstract)a)  

NASA Astrophysics Data System (ADS)

A new reflectometer system designed to monitor density fluctuations associated with rf waves has been successfully demonstrated on the DIII-D tokamak. It is a direct, internal, and nonperturbing diagnostic with access into the plasma core. This new diagnostic is motivated by a desire to improve understanding of rf wave physics issues, such as wave trajectory, heating mechanisms, rf wave deposition profile, and wave number, and is highly relevant to planned tokamaks such as ITER and TPX. This work is the first application of reflectometry to rf wave studies in a tokamak. Feedforward tracking receiver techniques are employed to remove frequency instabilities due to inherent drifts in the microwave sources and frequency pulling. In order to minimize spurious pickup of the rf pulse (˜60 MHz), heterodyne detection techniques are utilized, and all components are installed inside an rf shielding box. The system operates in the extraordinary mode (X mode) at 70 GHz. In this paper, a detailed description of the system, and data illustrating its successful operation will be presented.

Lee, J. H.; Doyle, E. J.; Luhmann, N. C., Jr.; Peebles, W. A.; Petty, C. C.; Pinsker, R. I.; Rettig, C. L.; Rhodes, T. L.

1995-01-01

360

Composite scintillator screen  

DOEpatents

A scintillator screen for an X-ray system includes a substrate of low-Z material and bodies of a high-Z material embedded within the substrate. By preselecting the size of the bodies embedded within the substrate, the spacial separation of the bodies and the thickness of the screen, the sensitivity of the screen to X-rays within a predetermined energy range can be predicted.

Zeman, Herbert D. (1687 Peach St., Memphis, TN 38112)

1994-01-01

361

Analysis of Radio Wave Propagation for ISM 2.4 GHz Wireless Sensor Networks in Inhomogeneous Vegetation Environments.  

PubMed

The use of wireless networks has experienced exponential growth due to the improvements in terms of battery life and low consumption of the devices. However, it is compulsory to conduct previous radio propagation analysis when deploying a wireless sensor network. These studies are necessary to perform an estimation of the range coverage, in order to optimize the distance between devices in an actual network deployment. In this work, the radio channel characterization for ISM 2.4 GHz Wireless Sensor Networks (WSNs) in an inhomogeneous vegetation environment has been analyzed. This analysis allows designing environment monitoring tools based on ZigBee and WiFi where WSN and smartphones cooperate, providing rich and customized monitoring information to users in a friendly manner. The impact of topology as well as morphology of the environment is assessed by means of an in-house developed 3D Ray Launching code, to emulate the realistic operation in the framework of the scenario. Experimental results gathered from a measurement campaign conducted by deploying a ZigBee Wireless Sensor Network, are analyzed and compared with simulations in this paper. The scenario where this network is intended to operate is a combination of buildings and diverse vegetation species. To gain insight in the effects of radio propagation, a simplified vegetation model has been developed, considering the material parameters and simplified geometry embedded in the simulation scenario. An initial location-based application has been implemented in a real scenario, to test the functionality within a context aware scenario. The use of deterministic tools can aid to know the impact of the topological influence in the deployment of the optimal Wireless Sensor Network in terms of capacity, coverage and energy consumption, making the use of these systems attractive for multiple applications in inhomogeneous vegetation environments. PMID:25513820

Azpilicueta, Leire; López-Iturri, Peio; Aguirre, Erik; Mateo, Ignacio; Astrain, José Javier; Villadangos, Jesús; Falcone, Francisco

2014-01-01

362

Analysis of Radio Wave Propagation for ISM 2.4 GHz Wireless Sensor Networks in Inhomogeneous Vegetation Environments  

PubMed Central

The use of wireless networks has experienced exponential growth due to the improvements in terms of battery life and low consumption of the devices. However, it is compulsory to conduct previous radio propagation analysis when deploying a wireless sensor network. These studies are necessary to perform an estimation of the range coverage, in order to optimize the distance between devices in an actual network deployment. In this work, the radio channel characterization for ISM 2.4 GHz Wireless Sensor Networks (WSNs) in an inhomogeneous vegetation environment has been analyzed. This analysis allows designing environment monitoring tools based on ZigBee and WiFi where WSN and smartphones cooperate, providing rich and customized monitoring information to users in a friendly manner. The impact of topology as well as morphology of the environment is assessed by means of an in-house developed 3D Ray Launching code, to emulate the realistic operation in the framework of the scenario. Experimental results gathered from a measurement campaign conducted by deploying a ZigBee Wireless Sensor Network, are analyzed and compared with simulations in this paper. The scenario where this network is intended to operate is a combination of buildings and diverse vegetation species. To gain insight in the effects of radio propagation, a simplified vegetation model has been developed, considering the material parameters and simplified geometry embedded in the simulation scenario. An initial location-based application has been implemented in a real scenario, to test the functionality within a context aware scenario. The use of deterministic tools can aid to know the impact of the topological influence in the deployment of the optimal Wireless Sensor Network in terms of capacity, coverage and energy consumption, making the use of these systems attractive for multiple applications in inhomogeneous vegetation environments. PMID:25513820

Azpilicueta, Leire; López-Iturri, Peio; Aguirre, Erik; Mateo, Ignacio; Astrain, José Javier; Villadangos, Jesús; Falcone, Francisco

2014-01-01

363

Deformation welding on scintillating materials  

SciTech Connect

Experiments on connecting scintillating crystals to form homogeneous pieces by means of plastical deformation are described. Optical transmission, radiation hardness, and scintillation spectra have been used for the evaluation of the quality of the bond. The results of experiments on fluorides of cerium, barium, and lead; and cesium iodide confirm that deformation welding can be used successfully for economic manufacturing of large homogeneous scintillators from several smaller parts.

Bazhenov, A.V.; Egorov, V.K.; Gasparov, L.V.; Klassen, N.V.; Mahonin, S.I.; Shmurak, S.Z.; Shmyt`ko, I.M. [Russian Academy of Sciences, Chernogolovka (Russian Federation). Inst. of Solid State Physics

1994-12-31

364

Circular Polarization of Solar Radio Noise  

Microsoft Academic Search

IN two recent communications to these columns1,2 we have reported the existence of powerful radio emissions in the 5-metre wave-length band from sunspot areas. Since such radio waves must travel through regions of considerable ionization in escaping from the sun, it occurred to us that the magneto-ionic theory of radio wave propagation3, which has proved so useful in elucidating phenomena

E. V. Appleton; J. S. Hey

1946-01-01

365

Optical generation of millimeter-wave signals for fiber-radio systems using a dual-mode DFB semiconductor laser  

Microsoft Academic Search

This paper presents a new approach to the optical generation of millimeter-wave signals using a dual-mode multisection distributed feedback semiconductor laser. This simple device is capable of generating high power signals between 40 and 60 GHz with extremely high spectral purity and stability. The two optical modes produced by this laser are heterodyned on an ultrafast photodiode to give a

David Wake; Claudio R. Lima; Phillip A. Davies

1995-01-01

366

Modelling Radio-Wave Propagation in Buildings Solving 19th Century Physics with 21st Century Computers  

E-print Network

-wave propagation is governed by Maxwell's equations (formulated by James Clerk Maxwell in 1861). These equations, analytical solutions to Maxwell's equations are difficult, if not impossible, to obtain for anything other numerical solutions to Maxwell's equations. Contributions of this Research This research focuses on applying

Sun, Jing

367

Radio-frequency electromagnetic field measurements for direct detection of electron Bernstein waves in a torus plasma  

SciTech Connect

To identify the mode-converted electron Bernstein wave (EBW) in a torus plasma directly, we have developed an interferometry system, in which a diagnostic microwave injected outside of the plasma column was directly detected with the probing antenna inserted into the plasma. In this work, plasma production and heating are achieved with 2.45 GHz, 2.5 kW electron cyclotron heating (ECH), whereas diagnostics are carried out with a lower power (10 W) separate frequency (1-2.1 GHz) microwave. Three components, i.e., two electromagnetic (toroidal and poloidal directions) and an electrostatic (if refractive index is sufficiently higher than unity, it corresponds to radial component), of ECRF electric field are simultaneously measured with three probing antennas, which are inserted into plasma. Selectivities of each component signal were checked experimentally. Excitation antennas have quite high selectivity of direction of linear polarization. As probing antennas for detecting electromagnetic components, we employed a monopole antenna with a length of 35 mm, and the separation of the poloidal (O-wave) and toroidal (X-wave) components of ECRF electric field could be available with this antenna. To detect EBW, which is an electrostatic wave, a small tip (1 mm) antenna was used. As the preliminary results, we detected signals that have three characteristics of EBW, i.e., short wavelength, backward propagation, and electrostatic.

Yatsuka, Eiichi; Kinjo, Kiyotake; Morikawa, Junji; Ogawa, Yuichi [Graduate School of Frontier Sciences, University of Tokyo, Chiba 277-8568 (Japan)

2009-02-15

368

Self consistent radio-frequency wave propagation and peripheral direct current plasma biasing: Simplified three dimensional non-linear treatment in the 'wide sheath' asymptotic regime  

SciTech Connect

A minimal two-field fluid approach is followed to describe the radio-frequency (RF) wave propagation in the bounded scrape-off layer plasma of magnetic fusion devices self-consistently with direct current (DC) biasing of this plasma. The RF and DC parts are coupled by non-linear RF and DC sheath boundary conditions at both ends of open magnetic field lines. The physical model is studied within a simplified framework featuring slow wave (SW) only and lateral walls normal to the straight confinement magnetic field. The possibility is however kept to excite the system by any realistic 2D RF field map imposed at the outer boundary of the simulation domain. The self-consistent RF + DC system is solved explicitly in the asymptotic limit when the width of the sheaths gets very large, for several configurations of the RF excitation and of the target plasma. In the case of 3D parallelepipedic geometry, semi-analytical results are proposed in terms of asymptotic waveguide eigenmodes that can easily be implemented numerically. The validity of the asymptotic treatment is discussed and is illustrated by numerical tests against a quantitative criterion expressed from the simulation parameters. Iterative improvement of the solution from the asymptotic result is also outlined. Throughout the resolution, key physical properties of the solution are presented. The radial penetration of the RF sheath voltages along lateral walls at both ends of the open magnetic field lines can be far deeper than the skin depth characteristic of the SW evanescence. This is interpreted in terms of sheath-plasma wave excitation. Therefore, the proper choice of the inner boundary location is discussed as well as the appropriate boundary conditions to apply there. The asymptotic scaling of various quantities with the amplitude of the input RF excitation is established.

Colas, L.; Jacquot, J.; Hillairet, J.; Goniche, M. [CEA, IRFM, F-13108 Saint-Paul-lez-Durance (France); Heuraux, S.; Faudot, E. [IJL-P2M UMR 7198 CNRS, F-54506 Vandoeuvre les Nancy (France); Crombe, K. [Department of Applied Physics, Ghent University, B-9000 Ghent (Belgium); Kyrytsya, V. [LPP-ERM/KMS, Association Euratom-'Belgian State', TEC Partner, Brussels (Belgium)

2012-09-15

369

Lithium-loaded liquid scintillators  

SciTech Connect

The invention is directed to a liquid scintillating composition containing (i) one or more non-polar organic solvents; (ii) (lithium-6)-containing nanoparticles having a size of up to 10 nm and surface-capped by hydrophobic molecules; and (iii) one or more fluorophores. The invention is also directed to a liquid scintillator containing the above composition.

Dai, Sheng (Knoxville, TN); Kesanli, Banu (Mersin, TR); Neal, John S. (Knoxville, TN)

2012-05-15

370

Scintillation light transport and detection  

NASA Astrophysics Data System (ADS)

The MORSE neutron gamma-ray transport code has been modified to allow for the transport of scintillation light. This modified code is used to analyze the light collection characteristics of a large liquid scintillator module (18 × 18 × 350 cm 3).

Gabriel, T. A.; Lillie, R. A.

1987-08-01

371

Scintillation light transport and detection  

SciTech Connect

The MORSE neutron gamma-ray transport code has been modified to allow for the transport of scintillation light. This modified code is used to analyze the light collection characteristics of a large liquid scintillator module (18 x 18 x 350 cm/sup 3/).

Gabriel, T.A.; Lillie, R.A.

1986-08-01

372

Extruding plastic scintillator at Fermilab  

SciTech Connect

An understanding of the costs involved in the production of plastic scintillators and the development of a less expensive material have become necessary with the prospects of building very large plastic scintillation detectors. Several factors contribute to the high cost of plastic scintillating sheets, but the principal reason is the labor-intensive nature of the manufacturing process. In order to significantly lower the costs, the current casting procedures had to be abandoned. Since polystyrene is widely used in the consumer industry, the logical path was to investigate the extrusion of commercial-grade polystyrene pellets with dopants to yield high quality plastic scintillator. This concept was tested and high quality extruded plastic scintillator was produced. The D0 and MINOS experiments are already using extruded scintillator strips in their detectors. An extrusion line has recently been installed at Fermilab in collaboration with NICADD (Northern Illinois Center for Accelerator and Detector Development). This new facility will serve to further develop and improve extruded plastic scintillator. This paper will discuss the characteristics of extruded plastic scintillator and its raw materials, the different manufacturing techniques and the current R&D program at Fermilab.

Anna Pla-Dalmau; Alan D. Bross; Victor V. Rykalin

2003-10-31

373

Free liquid scintillation counting bibliography  

SciTech Connect

Packard Instrument Company announces the availability of its newly updated Bibliography of Packard Tri-Carb Liquid Scintillation Analyzers. This unique new booklet lists 628 references in which Packard Tri-Carb{reg_sign} liquid scintillation analyzers have been used in life science, environmental, nuclear power and archaeological measurements. All listings are cross-referenced by radionuclide, specific field of study and author.

NONE

1996-12-31

374

Intensity Scintillation and Astronomical Quantum Observation  

E-print Network

Holography is 3D imaging which can record intensity and phase at the same time. The importance of construct hologram is holographic recording and wavefront reconstruction. It is surprised that holography be discovered in study interstellar scintillation for pulsar provide a coherent light source recently. I think that is speckle hologram and speckle interference(i.e. intensity interference), and use modern technique which include phased array,CCD, digital signal processing and supercomputer can achieve that digital and computer holography from radio to X-ray astronomy. This means we can use it to image the universe and beyond the limited of telescope for cosmos provide much coherent light from pulsar,maser, black hole to 21cm recombination line. It gives a probe to the medium of near the black hole et al. From those coherent light sources in the sky, we can uncover one different universe that through astronomical quantum observation which use intensity interference.

Jiang Dong

2008-12-14

375

Radio science investigations with Voyager  

NASA Technical Reports Server (NTRS)

Radio links to and from the Voyager spacecraft will be used for occultation measurements of planetary and satellite atmospheres and ionospheres, the rings of Saturn, the solar corona, and the general-relativistic time delay for radio wave propagation through the solar gravity field. In addition, the radio link measurements may provide information on the gravity fields of the planets, the masses of the satellites, properties of the interplanetary medium, and long-wavelength gravitational radiation propagation in the solar system.

Eshleman, V. R.; Tyler, G. L.; Anderson, J. D.; Fjeldbo, G.; Levy, G. S.; Wood, G. E.; Croft, T. A.

1977-01-01

376

Radio-holographic analysis of Microlab-1 radio occultation data in the lower troposphere  

Microsoft Academic Search

The interpretation of radio occultation data in the lower troposphere is a complicated problem due to strong multipath effects. This problem can be solved on the basis of the wave optics. We analyze Microlab-1 radio occultation using two radio-holographic approaches: the radio-optics method, which employs the analysis of the local spatial spectra of the registered wave field, and the canonical

M. E. Gorbunov

2002-01-01

377

Radio telescopes  

Microsoft Academic Search

A radio telescope is used in radio astronomy to measure the intensity of the radiation received from various parts of the sky. Such a telescope must be able both to detect and to locate faint radio sources of small angular size, and also to measure the brightness distribution across extended radio sources or over large sky areas. Ideally the telescope

J. Findlay

1964-01-01

378

Climatology of ionospheric scintillations and TEC trend over the Ugandan region  

NASA Astrophysics Data System (ADS)

This study presents results on the investigation of the diurnal, monthly and seasonal variability of Total Electron Content (TEC), phase (??) and amplitude (S4) scintillation indices over Ugandan (Low latitude) region. Scintillation Network Decision Aid (SCINDA) data was obtained from Makerere (0.34°N, 32.57°E) station, Uganda for two years (2011 and 2012). Data from two dual frequency GPS receivers at Mbarara (0.60°S, 30.74°E) and Entebbe (0.04°N, 32.44°E) was used to study TEC climatology during the same period of scintillation study. The results show that peak TEC values were recorded during the months of October-November, and the lowest values during the months of July-August. The diurnal peak of TEC occurs between 10:00 and 14:00 UT hours. Seasonally, the ascending and descending phases of TEC were observed during the equinoxes (March and September) and solstice (June and December), respectively. The scintillations observed during the study were classified as weak (0.1?S4,???0.3) and strong (0.3scintillation pattern showed peaks between 17:00 and 22:00 UT hour, while the seasonal pattern follows the TEC pattern mentioned above. Amplitude scintillation was more dominant than phase scintillation during the two years of the study. Scintillation peaks occur during the months of March-April and September-October, while the least scintillations occur during the months of June-July. Therefore, the contribution of this study is filling the gap in the current documentation of amplitude scintillation without phase scintillation over the Ugandan region. The scintillations observed have been attributed to wave-like structures which have periods of about 2-3 h, in the range of that of large scale travelling ionospheric disturbances (LSTIDs).

Amabayo, Emirant Bertillas; Edward, Jurua; Cilliers, Pierre J.; Habarulema, John Bosco

2014-03-01

379

Guided radio-wave propagation in the equatorial ionosphere according to the Intercosmos-19 and Alouette/ISIS satellites  

NASA Astrophysics Data System (ADS)

In addition to normal vertical-incident ionogram traces, strongly remote (up to 2000 km), traces of HF-radio-signal reflections observed on topside-sounder ionograms of the Interkosmos-19 satellite obtained in the equatorial ionosphere are presented. Such traces are connected with waveguides (ducts). These waveguides are field-aligned irregularities of ionospheric plasma with electron density depletion of a few percent and cross-field dimension of a few to several kilometers. Ray tracing confirms this supposition and allows an estimate of the typical parameters of the waveguides. The waveguide traces usually start at the cutoff frequency of the main trace. However, sometimes they begin at much lower frequencies which indicate the waveguides are located in plasma bubbles. Only one ducted trace is usually observed on the Interkosmos-19 ionograms; a second conjugate trace is rarely recorded. Waveguides are observed at all heights of Interkosmos-19 (500-1000 km) inside the equatorial anomaly region (from -40 to +40 degrees DipLat). Ducted-echo characteristics observed with the Interkosmos-19 are different from those observed earlier with the Alouette and ISIS satellites. This difference is discussed. It is shown that the ionospheric plasma irregularities responsible for the waveguides are observed much more often during nighttime than during daytime.

Karpachev, Alexander; Zhbankov, Gennadii; Telegin, Viktor; Kuleshova, Valentina

380

Guided radio-wave propagation in the equatorial ionosphere according to the topside sounding onboard Interkosmos-19  

NASA Astrophysics Data System (ADS)

In addition to normal vertical-incident ionogram traces, strongly remote (up to 2000 km) traces of HF-radio-signal reflections observed on topside-sounder ionograms of the Interkosmos-19 satellite obtained in the equatorial ionosphere are presented. Such traces are connected with waveguides (ducts). These waveguides are field-aligned irregularities of the ionospheric plasma with electron density depletions of a few percent and cross-field dimension of a few to several kilometers. Ray tracing confirms this supposition and allows an estimate of typical waveguide parameters: diameter ?10-15 km and amplitude |?N/N|?10%, where N is the electron density. The waveguide traces usually start at the cutoff frequencies of the main traces. However, sometimes they begin at much lower frequencies which indicates the satellite was transitioning through an equatorial plasma bubble during the recording of the ionogram. The X-mode of ducted echoes is more distinct then the O-mode. Only one ducted trace is usually observed on the Interkosmos-19 ionograms; a second conjugate trace is rarely recorded. The same is true for combination modes which is a combination of an oblique-incidence and guided propagation. Waveguides are observed at all heights of Interkosmos-19 (500-1000 km) inside the equatorial anomaly region (from -40° to +40° Dip). Waveguides are usually associated with other irregularities of various sizes in the equatorial ionosphere, some of which cause additional traces and spread F on the topside-sounding ionograms. Ducted-echo characteristics observed with Interkosmos-19 are different from those observed earlier with the Alouette and ISIS satellites. This difference is discussed. It is shown that the ionospheric plasma irregularities responsible for the waveguides are observed much more often during nighttime than during daytime.

Karpachev, A. T.; Zhbankov, G. A.; Kuleshova, V. P.; Telegin, V. A.

2014-12-01

381

Impairment of radio wave signal by rainfall on fixed satellite service on earth-space path at 37 stations in Nigeria  

NASA Astrophysics Data System (ADS)

This study investigates the effect of rainfall on horizontally polarized radio waves for fixed satellite service at Ku, Ka and V bands for links to the recently launched Nigeria Communication Satellite one (NigComSat-1), for annual time availabilities of 99-99.99% in an average year for 37 stations in Nigeria. The results obtained at Ku-band downlink shows that 99.99% availability is possible in all the 37-stations in Nigeria. At Ka-band downlink the results also show that only 99.9% availability is practicable in all the 37 stations in Nigeria. At V-band downlink, 99.99% availability is also not possible in all the 37 stations in Nigeria. An availability level of 99.9% is only practicable in the North-West (NW) and North-East (NE) regions, where the attenuation is between 14 and 17.9 dB. Total fade out of signals during rainfall are probable in the South-South (SS), South-East (SE), South-West (SW) and Middle-Belt (MB) regions at 99.9% availability.

Omotosho, T. V.; Oluwafemi, C. O.

2009-06-01

382

Impact of the Ulysses velocity on the diagnosis of the electron density by the Unified Radio and Plasma Wave sounder in the outskirts of the Io torus  

NASA Astrophysics Data System (ADS)

The resonance spectra collected on February 8, 1992, in the outskirts of the Io plasma torus by the Unified Radio and Plasma wave (URAP) relaxation sounder on board the Ulysses spacecraft present significant differences from the active spectra gathered by earthbound spacecraft in similar plasma conditions. The most striking anomaly is the lack of resonances at the harmonics of the electron gyrofrequency, one of the most common signatures found in usual sounder spectra. These differences are interpreted, when computing the dispersion relation of the Bernstein modes triggered by the sounder, by taking into account the large frequency shift induced on the resonances by the high speed of the Ulysses spacecraft in the plasma. The frequency of the shifted resonances depends on the ratio Vsat/p/Vth of the spacecraft speed relative to the plasma and the thermal speed of the electrons. The observed resonances are all found to be in excellent agreement with the computed frequencies obtained in this way. Some predicted resonances are not observed on the Ulysses spectra, but it is suggested that they have too long a wavelength to be easily detected by the URAP antenna. As a by-product of the electron density diagnosis allowed by this analysis a rough estimate of the electron temperature can be deduced.

Le Sager, Philippe; Canu, Patrick; Cornilleau-Wehrlin, Nicole

1998-11-01

383

High Efficiency Traveling-Wave Tube Power Amplifier for Ka-Band Software Defined Radio on International Space Station-A Platform for Communications Technology Development  

NASA Technical Reports Server (NTRS)

The design, fabrication and RF performance of the output traveling-wave tube amplifier (TWTA) for a space based Ka-band software defined radio (SDR) is presented. The TWTA, the SDR and the supporting avionics are integrated to forms a testbed, which is currently located on an exterior truss of the International Space Station (ISS). The SDR in the testbed communicates at Ka-band frequencies through a high-gain antenna directed to NASA s Tracking and Data Relay Satellite System (TDRSS), which communicates to the ground station located at White Sands Complex. The application of the testbed is for demonstrating new waveforms and software designed to enhance data delivery from scientific spacecraft and, the waveforms and software can be upgraded and reconfigured from the ground. The construction and the salient features of the Ka-band SDR are discussed. The testbed is currently undergoing on-orbit checkout and commissioning and is expected to operate for 3 to 5 years in space.

Simons, Rainee N.; Force, Dale A.; Kacpura, Thomas J.

2013-01-01

384

Proton recoil scintillator neutron rem meter  

DOEpatents

A neutron rem meter utilizing proton recoil and thermal neutron scintillators to provide neutron detection and dose measurement. In using both fast scintillators and a thermal neutron scintillator the meter provides a wide range of sensitivity, uniform directional response, and uniform dose response. The scintillators output light to a photomultiplier tube that produces an electrical signal to an external neutron counter.

Olsher, Richard H. (Los Alamos, NM); Seagraves, David T. (Los Alamos, NM)

2003-01-01

385

Cassini Radio Science  

Microsoft Academic Search

Cassini radio science investigations will be conducted both during the cruise (gravitational wave and conjunction experiments) and the Saturnian tour of the mission (atmospheric and ionospheric occultations, ring occultations, determinations of masses and gravity fields). New technologies in the construction of the instrument, which consists of a portion on-board the spacecraft and another portion on the ground, including the use

A. J. Kliore; J. D. Anderson; J. W. Armstrong; S. W. Asmar; C. L. Hamilton; N. J. Rappaport; H. D. Wahlquist; R. Ambrosini; F. M. Flasar; R. G. French; L. Iess; E. A. Marouf; A. F. Nagy

2004-01-01

386

Cassini Radio Science  

Microsoft Academic Search

Cassini radio science investigations will be conducted both during the cruise (gravitational wave and conjunction experiments) and the Saturnian tour of the mission (atmospheric and ionospheric occultations, ring occultations, determinations of masses and gravity fields). New technologies in the construction of the instrument, which consists of a portion on-board the spacecraft and another portion on the ground, including the use

A. J. KLIORE; J. D. ANDERSON; J. W. ARMSTRONG; S. W. ASMAR; C. L. HAMILTON; N. J. RAPPAPORT; H. D. WAHLQUIST; R. Ambrosini; F. M. FLASAR; R. G. FRENCH; L. Iess; E. A. MAROUF; A. F. NAGY

387

Radio Emissions At Mercury  

NASA Astrophysics Data System (ADS)

Mercury may produce cyclotron radio emissions (up to~10-20 kHz) from mildly ener- getic electrons in its most highly magnetized (polar) regions, and possible synchrotron radiation (up to a few MHz?) from more energetic electrons. Cyclotron emissions would be trapped in the magnetospheric cavity, and we attempt to estimate their in- tensity by extrapolating a scaling law established for the other solar system plane- tary radio emissions. In paralel, solar radio emissions (from interplanetary transient shocks, CMEs, and energetic particle streams) observed in the vicinity of Mercury could be a good index of solar activity, to be correlated with the Hemrean magne- tospheric response. We summarize the experimental requirements corresponding to these scientific objectives and present a possible contribution to a Radio and Plasma Wave Electric-field (RPW-E) instrument on BepiColombo/MMO.

Zarka, P.; Bougeret, J.-L.; Issautier, K.; Maksimovic, M.; Manning, R.; Meyer, N.; Moncuquet, M.

388

The Sardinia Radio Telescope  

NASA Astrophysics Data System (ADS)

We present the status of the Sardinia Radio Telescope (SRT) project, a new general purpose, fully steerable 64 m diameter parabolic radio telescope under construction in Sardinia. The instrument is funded by Italian Ministry of University and Research (MIUR), by the Sardinia Regional Government (RAS), and by the Italian Space Agency (ASI), and it is charge to three research structures of the National Institute for Astrophysics (INAF): the Institute of Radio Astronomy of Bologna, the Cagliari Astronomical Observatory (in Sardinia), and the Arcetri Astrophysical Observatory in Florence. The radio telescope has a shaped Gregorian optical configuration with a 8 m diameter secondary mirror and additional Beam-Wave Guide (BWG) mirrors. One of the most challenging feature of SRT is the active surface of the primary reflector which provides good efficiency up to about 100 GHz. This paper reports on the most recent advances of the construction.

D'Amico, Nichi

2011-08-01

389

A multidisciplinary study of planetary, solar and astrophysical radio emissions  

NASA Technical Reports Server (NTRS)

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.

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

1986-01-01

390

Scintillator materials containing lanthanum fluorides  

DOEpatents

An improved radiation detector containing a crystalline mixture of LaF[sub 3] and CeF[sub 3] as the scintillator element is disclosed. Scintillators made with from 25% to 99.5% LaF[sub 3] and the remainder CeF[sub 3] have been found to provide a balance of good stopping power, high light yield and short decay constant that is equal to or superior to other known scintillator materials, and which may be processed from natural starting materials containing both rare earth elements. The radiation detectors disclosed are favorably suited for use in general purpose detection and in positron emission tomography. 2 figures.

Moses, W.W.

1991-05-14

391

A multi-instrument case study of high-latitude ionospheric GNSS scintillation due to drifting plasma irregularities  

NASA Astrophysics Data System (ADS)

For this study, GPS receiver scintillation and Total Electron Content (TEC) data from high-latitude locations on Svalbard have been combined with several other data sets, including the EISCAT Svalbard Radar (ESR) and allsky cameras, to perform a multi-instrument case study of high-latitude GPS ionospheric scintillations in relation to drifting plasma irregularities at night over Svalbard on 31 October 2011. Scintillations are rapid amplitude and phase fluctuations of electromagnetic signals. GNSS-based systems may be disturbed by ionospheric plasma irregularities and structures such as plasma patches (areas of enhanced electron density in the polar cap) and plasma gradients. When the GNSS radio signals propagate through such areas, in particular gradients, the signals experience scintillations that at best increases positioning errors and at worst may break the receiver's signal lock, potentially resulting in the GNSS receiver losing track of its position. Due to the importance of many GNSS applications, it is desirable to study the scintillation environment to understand the limitations of the GNSS systems. We find scintillation mainly localised to plasma gradients, with predominantly phase scintillation at the leading edge of patches and both phase and amplitude scintillation at the trailing edge. A single edge may also contain different scintillation types at different locations.

van der Meeren, C.; Oksavik, K.; Moen, J. I.; Romano, V.

2013-12-01

392

Ionospheric irregularities during a substorm event: Observations of ULF pulsations and GPS scintillations  

NASA Astrophysics Data System (ADS)

Plasma instability in the ionosphere is often observed as disturbances and distortions of the amplitude and phase of the radio signals, which are known as ionospheric scintillations. High-latitude ionospheric plasma, closely connected to the solar wind and magnetospheric dynamics, produces very dynamic and short-lived Global Positioning System (GPS) scintillations, making it challenging to characterize them. It is observed that scintillations in the high-latitude ionosphere occur frequently during geomagnetic storms and substorms. In addition, it is well known that Ultra Low Frequency (ULF) pulsations (Pi2 and Pi1B) are closely associated with substorm activity. This study reports simultaneous observations of Pi2 and Pi1B pulsations and GPS phase scintillations during a substorm using a newly designed Autonomous Adaptive Low-Power Instrument Platform (AAL-PIP) installed at the South Pole. The magnetic field and GPS data from the instruments appear to be associated in terms of their temporal and spectral features. Moreover, the scintillation events were observed near the auroral latitudes where Pi1B pulsations are commonly detected. The temporal, spectral and spatial association between the scintillation and geomagnetic pulsation events suggests that the magnetic field perturbations and enhanced electric fields caused by substorm currents could contribute to the creation of plasma instability in the high-latitude ionosphere, leading to GPS scintillations.

Kim, H.; Clauer, C. R.; Deshpande, K.; Lessard, M. R.; Weatherwax, A. T.; Bust, G. S.; Crowley, G.; Humphreys, T. E.

2014-07-01

393

Scintillator fiber optic long counter  

DOEpatents

A flat response position sensitive neutron detector capable of providing neutron spectroscopic data utilizing scintillator fiber optic filaments embedded in a neutron moderating housing having an open end through which neutrons enter to be detected.

McCollum, Tom (Sterling, VA); Spector, Garry B. (Fairfax, VA)

1994-01-01

394

Ionospheric Irregularities at High Latitudes During Geomagnetic Storms and Substorms: Simultaneous Observations of Magnetic Field Perturbations and GPS Scintillations  

NASA Astrophysics Data System (ADS)

Plasma instability in the ionosphere is often observed as disturbance and distortion of the amplitude and phase of radio signals, which are known as ionospheric scintillations. High-latitude ionospheric plasma, closely connected to solar wind and magnetospheric dynamics, produce very dynamic and short-lived GPS scintillations, making it challenging to characterize them. This study reports simultaneous observations of geomagnetic pulsations and GPS signal scintillations during geomagnetic storms and substorms using a newly designed Autonomous Adaptive Low-Power Instrument Platform (AAL-PIP) installed at the South Pole. A statistical investigation of the AAL-PIP data recorded from January through May 2012 is presented to study local time distribution of scintillation events and a correlation between GPS scintillation and magnetic field perturbations. This report discusses a possible connection between magnetic field perturbations associated with the ionospheric currents and the creation of plasma instability by examining relative contribution of storm/substorm activity to ionospheric irregularities.

Kim, H.; Deshpande, K.; Clauer, C. R.; Bust, G. S.; Crowley, G.; Humphreys, T. E.; Kim, L.; Lessard, M.; Weatherwax, A. T.; Zachariah, T. P.

2012-12-01

395

Correlation of scintillation occurrence with IMF reversals and impact on GNSS receiver tracking performance in Northern Europe  

NASA Astrophysics Data System (ADS)

Ionospheric scintillation manifests itself as rapid fluctuations in the phase and amplitude of a transionospheric radio signal as it passes through small scale ionospheric plasma density irregularities. The occurrence of ionospheric scintillation is highest over the equatorial and auroral regions. Over the auroral regions, scintillation occurrence is associated with large scale plasma structures and is mainly enhanced during geomagnetic storms. At the GNSS (Global Navigation Satellite Systems) frequencies, amplitude scintillation is not of significant concern for auroral regions. Phase scintillation however poses a greater concern. In this context, an investigation on the possible correlation between the southward turning of the Interplanetary Magnetic Field (IMF) Bz and the occurrence of phase scintillation at high latitudes was carried out, which could help improve our understanding of the auroral scintillation. Scintillation data used for the studies were collected over the high latitude station of Bronnoysund (geographic latitude 65 deg. N) in Norway. This station is currently deployed under an Engineering and Physical Sciences Research Council (EPSRC) funded project titled "GNSS scintillation: Detection, forecasting and mitigation". The occurrence of phase scintillation is characterised by the widely used index Phi60, which is the standard deviation of the carrier phase averaged over 60s, based on 50 Hz measurements. The IMF Bz data used in the analysis was obtained from the Advanced Composition Explorer (ACE) website. In the case of GNSS receivers, scintillation can cause cycle slips, degrade the positioning accuracy and when severe enough even lead to complete loss of signal lock. An analysis of correlation between phase scintillation levels and tracking performance of a GNSS receiver deployed in Bronnoysund was performed for GPS L1C/A, L2C and GLONASS L1, L2 signals. The receiver tracking performance was evaluated by calculating the variance of the error at the output of the Phase Locked Loop (PLL).

Vadakke Veettil, S.; Aquino, M.

2012-12-01

396

Turbulence in deep radio occultations  

NASA Astrophysics Data System (ADS)

The effects of turbulence in the focal region of spherical or weakly oblate refracting bodies on the evolute flashes associated with the crossing of the evolute of the planetary limb by an occulted spacecraft are investigated. The approximate theory of focal evolutes in oblate refractivity fields developed by Eshleman et al. (1979) is combined with a generalized weak scattering scintillation theory that includes the effect of focusing around a curved limb to obtain expressions for the scintillation index and power spectrum. Results are then applied to the radio observations of the crossing of the focal evolute of Jupiter by Voyager 1, in which no flash was detected, and to the effects of the solar coronal plasma on the gravitational lens of the sun.

Haugstad, B. S.

1981-12-01

397

Cognitive radio: Making software radios more personal  

Microsoft Academic Search

Software radios are emerging as platforms for multiband multimode personal communications systems. Radio etiquette is the set of RF bands, air interfaces, protocols, and spatial and temporal patterns that moderate the use of the radio spectrum. Cognitive radio extends the software radio with radio-domain model-based reasoning about such etiquettes. Cognitive radio enhances the flexibility of personal services through a Radio

Joseph Mitola; Gerald Quentin Maguire Jr.

1999-01-01

398

LORA: A scintillator array for LOFAR to measure extensive air showers  

NASA Astrophysics Data System (ADS)

The measurement of the radio emission from extensive air showers, induced by high-energy cosmic rays, is one of the key science projects of the LOFAR radio telescope. The LOfar Radboud air shower Array (LORA) has been installed in the core of LOFAR in the Netherlands. The main purpose of LORA is to measure the properties of air showers and to trigger the read-out of the LOFAR radio antennas to register extensive air showers. The experimental set-up of the array of scintillation detectors and its performance are described.

Thoudam, S.; Buitink, S.; Corstanje, A.; Enriquez, J. E.; Falcke, H.; Frieswijk, W.; Hörandel, J. R.; Horneffer, A.; Krause, M.; Nelles, A.; Schellart, P.; Scholten, O.; ter Veen, S.; van den Akker, M.

2014-12-01

399

The Radial Extent and Warp of the Ionized Galactic Disk. II. A Likelihood Analysis of Radio-Wave Scattering Toward the Anticenter  

E-print Network

We use radio-wave scattering data to constrain the distribution of ionized gas in the outer Galaxy. Like previous models, our model for the H II disk includes parameters for the radial scale length and scale height of the H II, but we allow the H II disk to warp and flare. Our model also includes the Perseus arm. We use a likelihood analysis on 11 extragalactic sources and 7 pulsars. Scattering in the Perseus arm is no more than 60% of the level contributed by spiral arms in the inner Galaxy, equivalent to a 1 GHz scattering diameter of 1.5 mas. Our analysis favors an unwarped, nonflaring disk with a 1 kpc scale height, though this may reflect the non-uniform and coarse coverage provided by the available data. The lack of a warp indicates that VLBI observations near 1 GHz with an orbiting station having baseline lengths of a few Earth diameters will not be affected by interstellar scattering at Galactic latitudes |b| ~ 15 degrees. The radial scale length is 15--20 kpc, but the data cannot distinguish between a gradual decrease in the electron density and a truncated distribution. We favor a truncated one, because we associate the scattering with massive star formation, which is also truncated near 20 kpc. The distribution of electron density turbulence decreases more rapidly with Galactocentric distance than does the hydrogen distribution. Alternate ionizing and turbulent agents---the intergalactic ionizing flux and satellite galaxies passing through the disk---do not contribute significantly to scattering. We cannot exclude the possibility that a largely ionized, but quiescent disk extends to >~ 100 kpc, similar to that for some Ly-alpha absorbers.

T. Joseph W. Lazio; James M. Cordes

1997-11-15

400

Firefighters' Radios  

NASA Technical Reports Server (NTRS)

Public Technology Inc. asked for NASA assistance to devise the original firefighter's radio. Good short-range radio communications are essential during a fire to coordinate hose lines, rescue victims, and otherwise increase efficiency. Useful firefighting tool is lower cost, more rugged short range two-way radio. Inductorless electronic circuit replaced inductances and coils in radio circuits with combination of transistors and other low-cost components. Substitution promises reduced circuit size and cost. Enhanced electrical performance made radio more durable and improved maintainability by incorporating modular construction.

1976-01-01

401

Radio Frequency Interference: Radio Astronomy's Biggest Enemy  

NASA Astrophysics Data System (ADS)

As technology progresses, the demand for the usage of the electromagnetic spectrum increases with it. The development is so fast and prolific that clean band space for passive users such as Radio Astronomy is becoming ever so scarce. Even though, several spectral bands have been protected for Radio Astronomy by Federal Communication Commission (in the USA) under the recommendations of the International Telecommunication Union (ITU), pressure for making more spectral space commercially usable is extreme. Although these commercial usages make our modern living at all possible, often the extreme vulnerability of passive users are are not fully appreciated, resulting in unwanted emissions (RFI) in the Radio Astronomy Bands. Another source of RFI is the fact that many of the electronic devices used in the observatories themselves generate radio waves. If proper precautions are not taken, these can be received back through the Radio Telescope itself. This problem is referred to as internal RFI. The focus of this paper is the search and diminution of internal RFI in the Arecibo Observatory in Arecibo, Puerto Rico. Using a simple setup of a log-periodic antenna and a Spectrum Analyzer, spectra spanning a frequency range of 100 - 1800 MHZ were recorded in some areas of the Observatory and the new Visitor Center (AOVEF). The measurements disclosed sources of radio emission among some of the digital electronic equipment in the Equipment room and a few displays in the AOVEF. Most prominent of these was a 2.5 MHz comb spanning the entire range of the measurements emitted from the SRENDIP and AOFTM machines. The respective groups were informed and corrective shielding & isolations were implemented immediately. In AOVEF, three displays, some audio-visual equipment, and video/digital cameras used by the visitors were found to be "leaky". In future, the use of such cameras will be prohibited and the exhibits will be screened appropriately.

Acevedo, F.; Ghosh, Tapasi

1997-12-01

402

FNAL-NICADD extruded scintillator  

SciTech Connect

The possibility to produce a scintillator that satisfies the demands of physicists from different science areas has emerged with the installation of an extrusion line at Fermi National Accelerator Laboratory (FNAL). The extruder is the product of the fruitful collaboration between FNAL and Northern Illinois Center for Accelerator and Detector Development (NICADD) at Northern Illinois University (NIU). The results from the light output, light attenuation length and mechanical tolerance indicate that FNAL-NICADD scintillator is of high quality. Improvements in the extrusion die will yield better scintillator profiles and decrease the time needed for initial tuning. This paper will present the characteristics of the FNAL-NICADD scintillator based on the measurements performed. They include the response to MIPs from cosmic rays for individual extruded strips and irradiation studies where extruded samples were irradiated up to 1 Mrad. We will also discuss the results achieved with a new die design. The attractive perspective of using the extruded scintillator with MRS (Metal Resistive Semiconductor) photodetector readout will also be shown.

Beznosko, D.; /Northern Illinois U.; Bross, A.; /Fermilab; Dyshkant, A.; /Northern Illinois U.; Pla-Dalmau, A.; /Fermilab; Rykalin, V.; /Northern Illinois U.

2005-09-01

403

Magnetohydrodynamic solitons and radio knots in jets  

NASA Technical Reports Server (NTRS)

Weakly nonlinear surface waves are examined in the context of the beam model for jetlike radio sources. By introducing a finite scale length, viz. the beam radius, geometrical dispersion can act to balance nonlinear wave growth and thereby produce solitons, localized wave packets of stable waveform. A method for obtaining a soliton equation from the MHD equations is presented and then applied to radio knots in jets.

Fiedler, R.

1986-01-01

404

EE4.18 RF Electronics 1. Radio and Radar Links 1 Radio and Radar Links  

E-print Network

An antenna is a transducer. A transmitting antenna converts the guided waves travelling on the cables connecting it to an electronic transmitter to travelling waves in space. The receiving antenna interactsEE4.18 RF Electronics 1. Radio and Radar Links 1 Radio and Radar Links 1.1 Objectives · Become

Papavassiliou, Christos

405

Development of radiation hard scintillators  

SciTech Connect

Substantial improvements have been made in the radiation hardness of plastic scintillators. Cylinders of scintillating materials 2.2 cm in diameter and 1 cm thick have been exposed to 10 Mrads of gamma rays at a dose rate of 1 Mrad/h in a nitrogen atmosphere. One of the formulations tested showed an immediate decrease in pulse height of only 4% and has remained stable for 12 days while annealing in air. By comparison a commercial PVT scintillator showed an immediate decrease of 58% and after 43 days of annealing in air it improved to a 14% loss. The formulated sample consisted of 70 parts by weight of Dow polystyrene, 30 pbw of pentaphenyltrimethyltrisiloxane (Dow Corning DC 705 oil), 2 pbw of p-terphenyl, 0.2 pbw of tetraphenylbutadiene, and 0.5 pbw of UVASIL299LM from Ferro.

Markley, F.; Woods, D.; Pla-Dalmau, A.; Foster, G. (Fermi National Accelerator Lab., Batavia, IL (United States)); Blackburn, R. (Michigan Univ., Nuclear Reactor Lab., Ann Arbor, MI (United States))

1992-05-01

406

Studies on scintillating fiber response  

NASA Astrophysics Data System (ADS)

Scintillating fibers of type Bicron BCF-12 with 2 × 2 mm 2 cross section, up to 600 mm length, and PMMA cladding have been tested, in conjunction with the multi-channel photomultiplier Hamamatsu R 4760, with minimum ionizing electrons. The impact of cladding, extramural absorbers and/or wrapping on the light attenuation and photoelectron yield is studied in detail. Fibers have been circularly bent with radii of 171 mm and arranged in two layers to bundles forming granulated scintillator rings. Their performance in the EDDA experiment at COSY for detection of high energy protons revealed typically more than 9 (6) photoelectrons per fiber from bundles with (without) mirror on the rear side, guaranteeing detection efficiencies >99% and full compatibility with corresponding solid scintillator rings. The time resolution of 3.4 ns FWHM per fiber read out is essentially due to the R 4760.

Albers, D.; Bisplinghoff, J.; Bollmann, R.; Büßer, K.; Cloth, P.; Diehl, O.; Dohrmann, F.; Drüke, V.; Engelhardt, H. P.; Ernst, J.; Eversheim, P. D.; Filges, D.; Gasthuber, M.; Gebel, R.; Greiff, J.; Groß, A.; Groß-Hardt, R.; Heine, A.; Heider, S.; Hinterberger, F.; Igelbrink, M.; Jahn, R.; Jeske, M.; Langkau, R.; Lindlein, J.; Maier, R.; Maschuw, R.; Mayer-Kuckuk, T.; Mertler, G.; Metsch, B.; Mosel, F.; Müller, M.; Münstermann, M.; Paetz gen. Schieck, H.; Petry, H. R.; Prasuhn, D.; Rohdjeß, H.; Rosendaal, D.; Roß, U.; von Rossen, P.; Scheid, H.; Schirm, N.; Schulz-Rojahn, M.; Schwandt, F.; Scobel, W.; Steeg, B.; Sterzenbach, G.; Trelle, H. J.; Wellinghausen, A.; Wiedmann, W.; Woller, K.; Ziegler, R.

1996-02-01

407

Development of radiation hard scintillators  

NASA Astrophysics Data System (ADS)

Substantial improvements have been made in the radiation hardness of plastic scintillators. Cylinders of scintillating materials 2.2 cm in diameter and 1 cm thick have been exposed to 10 Mrads of gamma rays at a dose rate of 1 Mrad/h in a nitrogen atmosphere. One of the formulations tested showed an immediate decrease in pulse height of only 4% and has remained stable for 12 days while annealing in air. By comparison a commercial PVT scintillator showed an immediate decrease of 58% and after 43 days of annealing in air it improved to a 14% loss. The formulated sample consisted of 70 parts by weight of Dow polystyrene, 30 pbw of pentaphenyltrimethyltrisiloxane (Dow Corning DC 705 oil), 2 pbw of p-terphenyl, 0.2 pbw of tetraphenylbutadiene, and 0.5 pbw of UVASIL299LM from Ferro.

Markley, F.; Woods, D.; Pla-Dalmau, A.; Foster, G.; Blackburn, R.

1993-01-01

408

Unitary scintillation detector and system  

DOEpatents

The invention is a unitary alpha, beta, and gamma scintillation detector and system for sensing the presence of alpha, beta, and gamma radiations selectively or simultaneously. The scintillators are mounted in a light-tight housing provided with an entrance window for admitting alpha, beta, and gamma radiation and excluding ambient light from the housing. Light pulses from each scintillator have different decay constants that are converted by a photosensitive device into corresponding differently shaped electrical pulses. A pulse discrimination system identifies the electrical pulses by their respective pulse shapes which are determined by decay time. The identified electrical pulses are counted in separate channel analyzers to indicate the respective levels of sensed alpha, beta, and gamma radiations.

McElhaney, Stephanie A. (Oak Ridge, TN); Chiles, Marion M. (Knoxville, TN)

1994-01-01

409

Galileo radio science investigations  

NASA Technical Reports Server (NTRS)

Galileo radio-propagation experiments are based on measurements of absolute and differential propagation time delay, differential phase delay, Doppler shift, signal strength, and polarization. These measurements can be used to study: the atmospheric and ionospheric structure, constituents, and dynamics of Jupiter; the magnetic field of Jupiter; the diameter of Io, its ionospheric structure, and the distribution of plasma in the Io torus; the diameters of the other Galilean satellites, certain properties of their surfaces, and possibly their atmospheres and ionospheres; and the plasma dynamics and magnetic field of the solar corona. The spacecraft system provides linear rather than circular polarization on the S-band downlink signal, the capability to receive X-band uplink signals, and a differential downlink ranging mode. A highly-stable, dual-frequency, spacecraft radio system is developed that is suitable for simultaneous measurements of all the parameters normally attributed to radio waves.

Howard, H. T.; Eshleman, V. R.; Hinson, D. P.; Kliore, A. J.; Lindal, G. F.; Woo, R.; Bird, M. K.; Volland, H.; Edenhoffer, P.; Paetzold, M.

1992-01-01

410

Enhanced efficiency of PbWO4:Mo,Nb scintillator  

NASA Astrophysics Data System (ADS)

The effect of Nb codoping on the optical properties of the PbWO4:Mo scintillator is investigated by radio- and thermoluminescence, scintillation decay, and light yield measurements. Steady-state radioluminescence efficiency of PbWO4:Mo,Nb with optimized doping concentrations (2750 and 350 molar ppm, respectively) becomes up to 20 times higher with respect to that of undoped PbWO4 and is comparable to that of Bi3Ge4O12. However, slow components down to several tens of microseconds appear in the time decay. Their existence may be related to the presence of traps monitored by thermoluminescence.

Nikl, M.; Bohacek, P.; Mihokova, E.; Solovieva, N.; Vedda, A.; Martini, M.; Pazzi, G. P.; Fabeni, P.; Kobayashi, M.; Ishii, M.

2002-04-01

411

Nanophosphor composite scintillator with a liquid matrix  

DOEpatents

An improved nanophosphor scintillator liquid comprises nanophosphor particles in a liquid matrix. The nanophosphor particles are optionally surface modified with an organic ligand. The surface modified nanophosphor particle is essentially surface charge neutral, thereby preventing agglomeration of the nanophosphor particles during dispersion in a liquid scintillator matrix. The improved nanophosphor scintillator liquid may be used in any conventional liquid scintillator application, including in a radiation detector.

McKigney, Edward Allen (Los Alamos, NM); Burrell, Anthony Keiran (Los Alamos, NM); Bennett, Bryan L. (Los Alamos, NM); Cooke, David Wayne (Santa Fe, NM); Ott, Kevin Curtis (Los Alamos, NM); Bacrania, Minesh Kantilal (Los Alamos, NM); Del Sesto, Rico Emilio (Los Alamos, NM); Gilbertson, Robert David (Los Alamos, NM); Muenchausen, Ross Edward (Los Alamos, NM); McCleskey, Thomas Mark (Los Alamos, NM)

2010-03-16

412

3D Printing of Scintillating Materials  

E-print Network

We demonstrate, for the first time, the applicability of 3D printing technique to the manufacture of scintillation detectors. We report of a formulation, usable in stereolithographic printing, that exhibits scintillation efficiency on the order of 30\\% of that of commercial polystyrene based scintillators. We discuss the applicability of these techniques and propose future enhancements that will allow tailoring the printed scintillation detectors to various application.

Mishnayot, Y; Cooperstein, I; Magdassi, S; Ron, G

2014-01-01

413

3D Printing of Scintillating Materials  

E-print Network

We demonstrate, for the first time, the applicability of 3D printing technique to the manufacture of scintillation detectors. We report of a formulation, usable in stereolithographic printing, that exhibits scintillation efficiency on the order of 30\\% of that of commercial polystyrene based scintillators. We discuss the applicability of these techniques and propose future enhancements that will allow tailoring the printed scintillation detectors to various application.

Y. Mishnayot; M. Layani; I. Cooperstein; S. Magdassi; G. Ron

2014-06-15

414

Hygroscopicity Evaluation of Halide Scintillators  

SciTech Connect

A collaborative study of relative hygroscopicity of anhydrous halide scintillators grown at various laboratories is presented. We have developed a technique to evaluate moisture sensitivity of both raw materials and grown crystals, in which the moisture absorption rate is measured using a gravimetric analysis. Degradation of the scintillation performance was investigated by recording gamma-ray spectra and monitoring the photopeak position, count rate and energy resolution. The accompanying physical degradation of the samples exposed to ambient atmosphere was photographically recorded as well. The results were compared with ben

Zhuravleva, M [The University of Tennessee] [The University of Tennessee; Stand, L [The University of Tennessee] [The University of Tennessee; Wei, H [The University of Tennessee] [The University of Tennessee; Hobbs, C. L. [University of Tennessee, Knoxville (UTK)] [University of Tennessee, Knoxville (UTK); Boatner, Lynn A [ORNL] [ORNL; Ramey, Joanne Oxendine [ORNL] [ORNL; Burger, Arnold [Fisk University, Nashville] [Fisk University, Nashville; Rowe, E [Fisk University, Nashville] [Fisk University, Nashville; Bhattacharya, P. [Fisk University, Nashville] [Fisk University, Nashville; Tupitsyn, E [Fisk University, Nashville] [Fisk University, Nashville; Melcher, Charles L [University of Tennessee, Knoxville (UTK)] [University of Tennessee, Knoxville (UTK)

2014-01-01

415

Tracking of Interplanetary CME/Shocks evolution using Type II radio burst observations  

NASA Astrophysics Data System (ADS)

The aim of this work is to apply a new analysis technique, using Type II radio observations in the kilometric (km) domain obtained by the Thermal Noise Receiver (TNR) of the WIND/WAVES experiment, to infer the speed evolution of interplanetary (IP) CME/shocks. These CME/Shocks propagating in the IP medium can generate km Type II radio emissions that occur at the fundamental and/or harmonic of the plasma frequency, so these radio emissions provide a means of remotely tracking CME/shocks. We combine our results with previously reported speeds from coronagraph white light and interplanetary scintillation observations, and in-situ measurements, to study the temporal speed evolution of these events. The shock speed values obtained by our analysis technique are in a reasonable agreement with the speed measurements inferred by other techniques at different heliocentric distance ranges. The combination of all the speed measurements show a gradual deceleration of the CME/shocks as they propagate to 1 AU.

Aguilar-Rodriguez, E.; Gonzalez-Esparza, A.; Ontiveros, V.

2010-12-01

416

Characteristics of High Latitude Ionosphere Scintillations  

NASA Astrophysics Data System (ADS)

As we enter a new solar maximum period, global navigation satellite systems (GNSS) receivers, especially the ones operating in high latitude and equatorial regions, are facing an increasing threat from ionosphere scintillations. The increased solar activities, however, also offer a great opportunity to collect scintillation data to characterize scintillation signal parameters and ionosphere irregularities. While there are numerous GPS receivers deployed around the globe to monitor ionosphere scintillations, most of them are commercial receivers whose signal processing mechanisms are not designed to operate under ionosphere scintillation. As a result, they may distort scintillation signal parameters or lose lock of satellite signals under strong scintillations. Since 2008, we have established and continuously improved a unique GNSS receiver array at HAARP, Alaska. The array contains high ends commercial receivers and custom RF front ends which can be automatically triggered to collect high quality GPS and GLONASS satellite signals during controlled heating experiments and natural scintillation events. Custom designed receiver signal tracking algorithms aim to preserve true scintillation signatures are used to process the raw RF samples. Signal strength, carrier phase, and relative TEC measurements generated by the receiver array since its inception have been analyzed to characterize high latitude scintillation phenomena. Daily, seasonal, and solar events dependency of scintillation occurrence, spectral contents of scintillation activities, and plasma drifts derived from these measurements will be presented. These interesting results demonstrate the feasibility and effectiveness of our experimental data collection system in providing insightful details of ionosphere responses to active perturbations and natural disturbances.

Morton, Y.

2012-12-01

417

Advantages and Problems of Nanocrystalline Scintillators  

Microsoft Academic Search

Our experiments with nanocrystalline scintillating rare earth oxides and rare earth fluorides have shown that in some cases nanoscopic dimensions provide essential improvement of the most important scintillation parameters: light yield, kinetics of scintillations, radiation hardness, etc. We found that in the range from 20 to 100-nm of the oxide and fluoride particles there are 3 types of layered structures:

N. V. Klassen; V. V. Kedrov; V. N. Kurlov; Yu. A. Ossipyan; S. Z. Shmurak; I. M. Shmyt'ko; G. K. Strukova; N. P. Kobelev; E. A. Kudrenko; O. A. Krivko; A. P. Kiselev; A. V. Bazhenov; T. N. Fursova

2008-01-01

418

Composite scintillators for detection of ionizing radiation  

DOEpatents

Applicant's present invention is a composite scintillator having enhanced transparency for detecting ionizing radiation comprising a material having optical transparency wherein said material comprises nano-sized objects having a size in at least one dimension that is less than the wavelength of light emitted by the composite scintillator wherein the composite scintillator is designed to have selected properties suitable for a particular application.

Dai, Sheng (Knoxville, TN) [Knoxville, TN; Stephan, Andrew Curtis (Knoxville, TN) [Knoxville, TN; Brown, Suree S. (Knoxville, TN) [Knoxville, TN; Wallace, Steven A. (Knoxville, TN) [Knoxville, TN; Rondinone, Adam J [Knoxville, TN

2010-12-28

419

Application of radio phase modes to modification and remote sensing of the atmosphere and space  

Microsoft Academic Search

Radio phase modes are a low-frequency electromagnetic wave (radio) manifestation of photon orbital angular momentum (OAM) modes. At optical (laser) wavelengths OAM is an active area of theoretical and experimental research. Theory and modelling of radio phase modes show they may also easily be generated and, under certain conditions, detected with modern radio antenna arrays. Transimission of radio phase modes

B. Isham; S. Mohammadi; J. Chau; D. L. Hysell; L. K. Daldorff; B. Thide; J. Bergman

2009-01-01

420

Jovian type III radio bursts  

NASA Technical Reports Server (NTRS)

Radio bursts have been observed in the Voyager plasma wave data from Jupiter that bear a striking resemblance to solar type III radio bursts. The emissions lie in the frequency range near 10 kHz, have durations of a minute or so, and occur in a set of periodically spaced bursts. The spacing between primary bursts is typically 15 min, but the bursts may have additional components which recur on time scales of about 3 min. The similarity with solar type III radio bursts suggests a source mechanism involving the movement of energetic electrons through a density gradient in the plasma surrounding Jupiter. The periodicity of bursts suggests Io may be involved in the generation of waves, since the timing is similar to the Alfven wave travel time from one hemisphere to the other through the Io torus.

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

1989-01-01

421

An improved scintillation beta spectrometer  

E-print Network

AN IYiiROVED SCINTILLATION BETA SPECTROMETER A Thesis Jimmy Fred McClary Submitted to the Graduate College of Tezas AdM University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE January 1964. Ma]or Sub...

McClary, Jimmy Fred

1964-01-01

422

SNO+ Scintillator Purification and Assay  

SciTech Connect

We describe the R and D on the scintillator purification and assay methods and technology for the SNO+ neutrino and double-beta decay experiment. The SNO+ experiment is a replacement of the SNO heavy water with liquid scintillator comprised of 2 g/L PPO in linear alkylbenzene (LAB). During filling the LAB will be transported underground by rail car and purified by multi-stage distillation and steam stripping at a flow rate of 19 LPM. While the detector is operational the scintillator can be recirculated at 150 LPM (full detector volume in 4 days) to provide repurification as necessary by either water extraction (for Ra, K, Bi) or by functional metal scavenger columns (for Pb, Ra, Bi, Ac, Th) followed by steam stripping to remove noble gases and oxygen (Rn, O{sub 2}, Kr, Ar). The metal scavenger columns also provide a method for scintillator assay for ex-situ measurement of the U and Th chain radioactivity. We have developed ''natural'' radioactive spikes of Pb and Ra in LAB and use these for purification testing. Lastly, we present the planned operating modes and purification strategies and the plant specifications and design.

Ford, R.; Vazquez-Jauregui, E. [SNOLAB, Creighton Mine, Lively, P3Y 1N2 (Canada); Chen, M. [Department of Physics, Queen's University, Kingston, K7L 3N6 (Canada); Chkvorets, O.; Hallman, D. [Department of Physics, Laurentian University, Sudbury, P3E 2C6 (Canada)

2011-04-27

423

Radio science investigations by VeRa onboard the Venus Express spacecraft  

NASA Astrophysics Data System (ADS)

The Venus Express Radio Science Experiment (VeRa) uses radio signals at wavelengths of 3.6 and 13 cm ("X"- and "S"-band, respectively) to investigate the Venus surface, neutral atmosphere, ionosphere, and gravity field, as well as the interplanetary medium. An ultrastable oscillator (USO) provides a high quality onboard reference frequency source; instrumentation on Earth is used to record amplitude, phase, propagation time, and polarization of the received signals. Simultaneous, coherent measurements at the two wavelengths allow separation of dispersive media effects from classical Doppler shift. VeRa science objectives include the following: Determination of neutral atmospheric structure from the cloud deck (approximately 40 km altitude) to 100 km altitude from vertical profiles of neutral mass density, temperature, and pressure as a function of local time and season. Within the atmospheric structure, search for, and if detected, study of the vertical structure of localized buoyancy waves, and the presence and properties of planetary waves. Study of the H 2SO 4 vapor absorbing layer in the atmosphere by variations in signal intensity and application of this information to tracing atmospheric motions. Scintillation effects caused by radio wave diffraction within the atmosphere can also provide information on small-scale atmospheric turbulence. Investigation of ionospheric structure from approximately 80 km to the ionopause (<600 km), allowing study of the interaction between solar wind plasma and the Venus atmosphere. Observation of forward-scattered surface echoes obliquely reflected from selected high-elevation targets with anomalous radar properties (such as Maxwell Montes). More generally, such bistatic radar measurements provide information on the roughness and density of the surface material on scales of centimeters to meters. Detection of gravity anomalies, thereby providing insight into the properties of the Venus crust and lithosphere. Measurement of the Doppler shift, propagation time, and frequency fluctuations along the interplanetary ray path, especially during periods of superior conjunction, thus enabling investigation of dynamical processes in the solar corona.

Häusler, B.; Pätzold, M.; Tyler, G. L.; Simpson, R. A.; Bird, M. K.; Dehant, V.; Barriot, J.-P.; Eidel, W.; Mattei, R.; Remus, S.; Selle, J.; Tellmann, S.; Imamura, T.

2006-11-01

424

Virtual radios  

Microsoft Academic Search

Conventional software radios take advantage of vastly improved analog to digital converters (ADCs) and digital signal processing (DSP) hardware. Our approach, which we refer to as virtual radios, also depends upon high performance ADCs. However, rather than use DSPs, we have chosen to ride the curve of rapidly improving workstation hardware. We use wideband digitization and then perform all of

Vanu Bose; Michael Ismert; Matt Welborn; John Guttag

1999-01-01

425

College Radio.  

ERIC Educational Resources Information Center

As with commercial stations, the underlying premise of the college radio station is to serve the community, whether it be the campus community or the community at large, but in unique ways often geared to underserved niches of the population. Much of college radio's charm lies in its unpredictable nature and constant mutations. The stations give…

Sauls, Samuel J.

426

Application of locality principle to radio occultation studies of the Earth's atmosphere and ionosphere  

NASA Astrophysics Data System (ADS)

A new formulation of previously introduced principle of locality is presented. The principle can be applied for modernization of the radio occultation (RO) remote sensing of the atmospheres and ionospheres of the Earth and planets. The principle states that significant contributions to variations of the amplitude and phase of the radio waves passing through a layered medium are connected with influence of the vicinities of tangential points where the refractivity gradient is perpendicular to the radio ray trajectory. The RO method assumes spherical symmetry of the investigated medium. In this case if location of a tangent point relative to the spherical symmetry center is known, the derivatives on time of the RO signal phase and Doppler frequency variations can be recalculated into the refractive attenuation. Several important findings are consequences of the locality principle: (i) if position of the center of symmetry is known, the total absorption along the ray path can be determined at a single frequency, (ii) in the case of low absorption the height, displacement from the radio ray perigee, and tilt of the inclined ionospheric (atmospheric) layers can be evaluated, (iii) the contributions of the layered and irregular structures in the RO signal can be separated and parameters of layers and turbulence can be measured at a single frequency using joint analysis of the amplitude and phase variations. Specially for the Earth's troposphere, the altitude distributions of the weak total absorption (about of 1-4 db) of the radio waves at GPS frequencies corresponding to possible influence of the oxygen and water vapor can be measured with accuracy of about 0.1 db at a single frequency. According with the locality principle, a new index of ionospheric activity is introduced. This index is measured from the phase variations of radio waves passing through the ionosphere. Its high correlation with S4 scintillation index is established. This correlation indicates the significant influence of locally spherical symmetric ionospheric layers on variations of the phase and amplitude of the RO signal passing through transionospheric communication links. Obtained results expand the applicable domain of the RO method as a powerful remote sensing technique for geophysical and meteorological research.

Pavelyev, A. G.; Liou, Y. A.; Matyugov, S. S.; Pavelyev, A. A.; Gubenko, V. N.; Zhang, K.; Kuleshov, Y.

2015-01-01

427

Author's personal copy A tunneling model for afterglow suppression in CsI:Tl,Sm scintillation materials  

E-print Network

radioluminescence, afterglow and thermoluminescence experiments on single-crystal samples of co-doped Cs thallium traps and combined radio- luminescence, afterglow and thermoluminescence experiments on single for 48 h at þ250 C, were also investigated by combined scintillation and thermoluminescence. The purpose

Hamilton, Douglas S.

428

Cosmic ray scintillations. II - General theory of interplanetary scintillations  

NASA Technical Reports Server (NTRS)

The motion of charged particles in a stochastic magnetic field with nonzero mean is considered via a generalized quasi-linear expansion of Liouville's equation. The general result is an equation relating cosmic ray scintillations to magnetic fluctuations and to cosmic ray gradients. The resonant interaction between particles and the random magnetic field is considered in detail, and the effect of nonlinear terms in the equations is considered. The nonlinear terms are important in damping out initial conditions and in determining conditions near cyclotron resonances. The application of the theory to the propagation of cosmic rays during quiet times in interplanetary space is considered. It is concluded that cosmic ray scintillations in interplanetary space may provide useful information about interplanetary particles and fields and also about nonlinear plasma interactions.

Owens, A. J.

1974-01-01

429

A multi-instrument study of high-latitude ionospheric irregularities and their effects on GPS ionospheric scintillation  

NASA Astrophysics Data System (ADS)

Scintillations are rapid amplitude and phase fluctuations of electromagnetic signals. GNSS-based systems may be disturbed by plasma irregularities and structures such as plasma patches (areas of enhanced electron density) and plasma gradients in the ionosphere. When the GNSS radio signals propagate through such areas, in particular gradients, the signals experience scintillations that at best increases positioning errors and at worst may break the receiver's signal lock, potentially resulting in the GNSS receiver losing track of its position. Due to the importance of many GNSS applications, it is desirable to study the scintillation environment to understand the limitations of the GNSS systems. For this study, GPS receiver scintillation and Total Electron Content (TEC) data from high-latitude locations will be combined with several other data sets, including the EISCAT Svalbard Radar (ESR) and allsky cameras to perform a multi-instrument case study of GPS ionospheric scintillations. The EISCAT data provides a means to determine the altitude and density of the F layer, which can then be used to calibrate allsky projections as well as coordinates of ionospheric piercing points of the GPS signals. The focus will be studying any connection between scintillations and polar cap patches; however, other interesting and related findings will also be presented, herein statistical long-timespan studies of GPS TEC and/or scintillation data.

van der Meeren, Christer; Oksavik, Kjellmar; Moen, Jøran; Romano, Vincenzo

2013-04-01

430

Millimeter-wave propagation in moist air: Model versus path data  

NASA Astrophysics Data System (ADS)

A practical atmospheric millimeter-wave propagation model (MPM) is updated and tested with experimental data from horizontal, line-of-sight links when there is no precipitation. The MPM computer program predicts attenuation and delay properties of moist air over ranges in frequency from 1 to 1000 GHz and in height from 0 to 30 km. Input variables are radio path distributions of pressure, temperature, relative humidity, and a suspended droplet concentration simulating haze and fog conditions. Terrestrial path data from millimeter-wave propagation experiments, including those from a 27 km link operated at 11.4, 28.8, and 96.1 GHz by the Institute for Telecommunication Sciences (ITS), have been analyzed. Calibrated mean signal levels permitted studies of water vapor losses. In addition, a spectral analysis was performed of clear-air scintillations caused by turbulence. In general, good agreement is obtained with the MPM for test frequencies up to 430 GHz.

Liebe, H. J.; Allen, K. C.; Hand, G. R.; Espeland, R. H.; Violette, E. J.

1985-03-01

431

Wave propagation in precipitation  

NASA Astrophysics Data System (ADS)

A unified model of electromagnetic wave interaction with the precipitation medium is presented. The scattering of an incident monochromatic field by a polydispersion of particles is considered. The radiometric implications of the thermal radiation of a polydispersion are outlined. Propagation through inhomogeneous dispersions, turbulence, and scintillation is treated. Monostatic dual polarization radar remote sensing of polydispersions is covered.

Delogne, P.

1983-04-01

432

Coherent Emission Mechanisms in Radio Pulsars  

NASA Astrophysics Data System (ADS)

A theory of pulsar radio emission generation, in which the observed waves are produced directly by the maser-type plasma instabilities on the anomalous cyclotron-Cherenkov resonance $$\\omega -\\kappa\\par\

Lyutikov, Maxim

1998-07-01

433

Planetary radio astronomy experiment for Voyager missions  

Microsoft Academic Search

The planetary radio astronomy experiment will measure radio spectra of planetary emissions in the range 1.2 kHz to 40.5 MHz. These emissions result from wave-particle-plasma interactions in the magnetospheres and ionospheres of the planets. At Jupiter, they are strongly modulated by the Galilean satellite Io.

J. W. Warwick; J. B. Pearce; R. G. Peltzer; A. C. Riddle

1977-01-01

434

Rural Radio in Dahomey: September, 1972.  

ERIC Educational Resources Information Center

Rural Radio (RR) in Dahomey has a radio network that covers most of the national territory with two transmitters plus 4KW short wave. The program themes are suggested by an advisory group from interested ministries such as Education, Youth and Sport, Agriculture, Health, etc., but the primary objective of the project lies in promoting dialogues…

McAnany, Emile G.

435

A helical scintillating fiber hodoscope  

NASA Astrophysics Data System (ADS)

A novel scintillating fiber hodoscope in helically cylindric geometry has been developed for detection of low multiplicity events of fast protons and other light charged particles in the internal target experiment EDDA at the Cooler Synchrotron COSY. The hodoscope consists of 640 scintillating fibers (2.5 mm diameter), arranged in four layers surrounding the COSY beam pipe. The fibers are helically wound in opposing directions and read out individually using 16-channel photomultipliers connected to a modified commercial encoding system. The detector covers an angular range of 9°? ??72° and 0°? ??360° in the lab frame. The detector length is 590 mm, the inner diameter 161 mm. Geometry and granularity of the hodoscope afford a position resolution of about 1.3 mm. The detector design took into consideration a maximum of reliability and a minimum of maintenance. An LED array may be used for monitoring purposes.

Altmeier, M.; Bauer, F.; Bisplinghoff, J.; Bissel, T.; Bollmann, R.; Busch, M.; Büßer, K.; Colberg, T.; Demirörs, L.; Diehl, O.; Dohrmann, F.; Engelhardt, H. P.; Eversheim, P. D.; Felden, O.; Gebel, R.; Glende, M.; Greiff, J.; Groß, A.; Groß-Hardt, R.; Hinterberger, F.; Jahn, R.; Jeske, M.; Jonas, E.; Krause, H.; Lahr, U.; Langkau, R.; Lindemann, T.; Lindlein, J.; Maier, R.; Maschuw, R.; Mayer-Kuckuck, T.; Meinerzhagen, A.; Nähle, O.; Pfuff, M.; Prasuhn, D.; Rohdjeß, H.; Rosendaal, D.; von Rossen, P.; Sanz, B.; Schirm, N.; Schulz-Rojahn, M.; Schwarz, V.; Scobel, W.; Thomas, S.; Trelle, H. J.; Weise, E.; Wellinghausen, A.; Wiedmann, W.; Woller, K.; Ziegler, R.; EDDA Collaboration

1999-07-01

436

The Production of Free Electrons in the Ionospheric D Layer by Solar and Galactic Cosmic Rays and the Resultant Absorption of Radio Waves  

Microsoft Academic Search

The behavior of the D layer under bombardment by solar and galactic cosmic rays of energy greater than a few Mev is discussed. In particular, the variation with incident particle flux of the ionospheric parameters that determine the equilibrium electron density is deduced by means of the measurements of mid-day and mid-night absorption of cosmic radio noise corre- sponding to

William Webber

1962-01-01

437

Buried plastic scintillator muon telescope  

NASA Astrophysics Data System (ADS)

Muon telescopes can have several applications, ranging from astrophysical to solar-terrestrial interaction studies, and fundamental particle physics. We show the design parameters, characterization and end-to-end simulations of a detector composed by a set of three parallel dual-layer scintillator planes, buried at fix depths ranging from 0.30 m to 3 m. Each layer is 4 m2 and is composed by 50 rectangular pixels of 4cm x 2 m, oriented at a 90 deg angle with respect to its companion layer. The scintillators are MINOS extruded polystyrene strips with two Bicron wavelength shifting fibers mounted on machined grooves. Scintillation light is collected by multi-anode PMTs of 64 pixels, accommodating two fibers per pixel. The front-end electronics has a time resolution of 7.5 nsec. Any strip signal above threshold opens a GPS-tagged 2 micro-seconds data collection window. All data, including signal and background, are saved to hard disk. Separation of extensive air shower signals from secondary cosmic-ray background muons and electrons is done offline using the GPS-tagged threefold coincidence signal from surface water cerenkov detectors located nearby in a triangular array. Cosmic-ray showers above 6 PeV are selected. The data acquisition system is designed to keep both, background and signals from extensive air showers for a detailed offline data.

Sanchez, F.; Medina-Tanco, G. A.; D'Olivo, J. C.; et al.

438

Application of an imaging HF riometer for the observation of scintillations of discrete cosmic sources  

NASA Astrophysics Data System (ADS)

Scintillations of discrete cosmic radio sources have been investigated theoretically and experimentally for radiation scattered from natural and artificial inhomogeneities in the auroral zone ionosphere. The observations were performed at a frequency of 38.2 MHz with the multibeam phased array antenna of the imaging riometer located at Poker Flat, Alaska. For quiet ionospheric conditions and weak scintillations, the spatial spectrum and transverse motion velocities of the Fresnel inhomogeneities have been recovered. A theoretically based approach has been developed to estimate the time coherence interval of the radiation for the case of saturated scintillations and strong ionospheric turbulence. Examples of scintillation records are analyzed for the case of scattering from artificial ionospheric irregularities induced by high-power HF radiation from the high-power auroral simulation (HIPAS) ionospheric modification facility. The effect of aspect-sensitive scattering of the cosmic source radiation by artificial field-aligned small-scale irregularities has been predicted and detected. Prospects for routine observations of the effects of scintillations and aspect-sensitive scattering are discussed for special operation modes of the ionospheric modification facility.

Bezrodny, V. G.; Charkina, O. V.; Galushko, V. G.; Groves, K.; Kashcheyev, A. S.; Watkins, B. J.; Yampolski, Y. M.; Murayama, Y.

2008-12-01

439

INSPIRE: A VLF Radio Project for High School Students  

ERIC Educational Resources Information Center

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…

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

2007-01-01

440

(Astro)Physics 343 Lecture # 7: Radio Telescopes etc.  

E-print Network

(Astro)Physics 343 Lecture # 7: Radio Telescopes etc. #12; Lab # 3: new data coming Several need telescopes? If a simple dipole antenna can detect radio waves... ...why do we need a telescope! Lab Report # 3 will now be due on Monday, March 31st. #12; Beware: radio frequency interference

Baker, Andrew J.

441

Exploring the Dynamic Radio Sky  

NASA Astrophysics Data System (ADS)

Most of what is currently known about slow radio transients (supernovae, gamma-ray bursts, tidal disruption events, stellar flares, etc.) has come via radio follow-up of objects identified by synoptic telescopes at optical, X-ray or gamma-ray wavelengths. However, with the ability to capture obscured, unbeamed and magnetically-driven phenomena, radio surveys offer unique discovery strong diagnostic for cosmic transients. For the first time, we are systematically exploring the dynamic radio sky on timescales between one day to several years using multi-epoch large surveys with the Karl G. Jansky Array (VLA). We have carried out surveys in the COSMOS deep field as well as wide fields like Stripe 82. I have developed a unique infrastructure for near-real-time calibration, imaging, transient search, transient vetting, rapid multiwavelength follow-up, and contemporaneous optical surveys to better characterize radio transient phenomena. A large part of my thesis includes the commissioning of a new observing mode at the VLA: On-The-Fly Mosaicking. This mode has significantly improved the survey efficiency of the VLA, and it is a driver for VLASS, the future all-sky survey planned with this telescope. Through our radio surveys we have discovered several fascinating transients that are unique to the radio. These surveys have established the VLA as an efficient transient discovery machine. My thesis has enormous implications for how to design efficient transient surveys for the next generation of radio interferometer facilities like ASKAP, MeerKAT, WSRT/Apertif and LOFAR. My work has also provided answers to key problems such as the rates of transients, demographics of variability of radio sources including AGN, and false-positive foreground for future searches for the radio counterparts of gravitational-wave (GW) sources.

Mooley, Kunal P.; Hallinan, Gregg; Frail, Dale A.; Myers, Steven T.; Kulkarni, Shrinivas R.; Bourke, Stephen; Horesh, Assaf

2015-01-01

442

Recording of relativistic particles in thin scintillators  

SciTech Connect

Results of investigating an assembly of thin scintillators and silicon photomultipliers for registering relativistic particles with the minimum ionization are presented. A high efficiency of registering relativistic particles using an Ej-212 plastic scintillator, BSF-91A wavelength-shifting fiber (Saint-Gobain), and a silicon photomultiplier (Hamamtsu) is shown. The measurement results are used for creating a scintillation hodoscope of the magnetic spectrometer for registering ? quanta in the GlueX experiment.

Tolstukhin, I A.; Somov, Alexander S. [JLAB; Somov, S. V.; Bolozdynya, A. I.

2014-11-01

443

Neutron position-sensitive scintillation detector  

DOEpatents

A device is provided for mapping one- and two-dimensional distributions of neutron-positions in a scintillation detector. The device consists of a lithium glass scintillator coupled by an air gap and a light coupler to an array of photomultipliers. The air gap concentrates light flashes from the scintillator, whereas the light coupler disperses this concentrated light to a predetermined fraction of the photomultiplier tube array.

Strauss, Michael G. (Downers Grove, IL); Brenner, Raul (Woodridge, IL)

1984-01-01

444

Neutron Spectrum Unfolding with Organic Scintillators for  

E-print Network

Neutron Spectrum Unfolding with Organic Scintillators for Arms-control Verification by Christopher of Doctor of Philosophy (Nuclear Engineering and Radiological Sciences) in The University of Michigan 2014

Becchetti, Fred

445

Waveshifters and Scintillators for Ionizing Radiation Detection  

SciTech Connect

Scintillation and waveshifter materials have been developed for the detection of ionizing radiation in an STTR program between Ludlum Measurements, Inc. and the University of Notre Dame. Several new waveshifter materials have been developed which are comparable in efficiency and faster in fluorescence decay than the standard material Y11 (K27) used in particle physics for several decades. Additionally, new scintillation materials useful for fiber tracking have been developed which have been compared to 3HF. Lastly, work was done on developing liquid scintillators and paint-on scintillators and waveshifters for high radiation environments.

B.Baumgaugh; J.Bishop; D.Karmgard; J.Marchant; M.McKenna; R.Ruchti; M.Vigneault; L.Hernandez; C.Hurlbut

2007-12-11

446

Understanding the Radio Variability of Sgr A*  

E-print Network

We determine the characteristics of the 7mm to 20cm wavelength radio variability in Sgr A* on time scales from days to three decades. The amplitude of the intensity modulation is between 30 and 39% at all wavelengths. Analysis of uniformly sampled data with proper accounting of the sampling errors associated with the lightcurves shows that Sgr A* exhibits no 57- or 106-day quasi-periodic oscillations, contrary to previous claims. The cause of the variability is investigated by examining a number of plausible scintillation models, enabling those variations which could be attributed to interstellar scintillation to be isolated from those that must be intrinsic to the source. Thin-screen scattering models do not account for the variability amplitude on most time scales. However, models in which the scattering region is extended out to a radius of 50-500pc from the Galactic Center account well for the broad characteristics of the variability on >4-day time scales. The ~ 10% variability on <4-day time scales at 0.7-3cm appears to be intrinsic to the source. The degree of scintillation variability expected at millimeter wavelengths depends sensitively on the intrinsic source size; the variations, if due to scintillation, would require an intrinsic source size smaller than that expected.

Jean-Pierre Macquart; Geoff Bower

2005-12-12

447

Cassini Radio Science  

NASA Astrophysics Data System (ADS)

Cassini radio science investigations will be conducted both during the cruise (gravitational wave and conjunction experiments) and the Saturnian tour of the mission (atmospheric and ionospheric occultations, ring occultations, determinations of masses and gravity fields). New technologies in the construction of the instrument, which consists of a portion on-board the spacecraft and another portion on the ground, including the use of the Ka-band signal in addition to that of the S- and X-bands, open opportunities for important discoveries in each of the above scientific areas, due to increased accuracy, resolution, sensitivity, and dynamic range.

Kliore, A. J.; Anderson, J. D.; Armstrong, J. W.; Asmar, S. W.; Hamilton, C. L.; Rappaport, N. J.; Wahlquist, H. D.; Ambrosini, R.; Flasar, F. M.; French, R. G.; Iess, L.; Marouf, E. A.; Nagy, A. F.

448

Cassini Radio Science  

NASA Astrophysics Data System (ADS)

Cassini radio science investigations will be conducted both during the cruise (gravitational wave and conjunction experiments) and the Saturnian tour of the mission (atmospheric and ionospheric occultations, ring occultations, determinations of masses and gravity fields). New technologies in the construction of the instrument, which consists of a portion on-board the spacecraft and another portion on the ground, including the use of the Ka-band signal in addition to that of the S- and X-bands, open opportunities for important discoveries in each of the above scientific areas, due to increased accuracy, resolution, sensitivity, and dynamic range.

Kliore, A. J.; Anderson, J. D.; Armstrong, J. W.; Asmar, S. W.; Hamilton, C. L.; Rappaport, N. J.; Wahlquist, H. D.; Ambrosini, R.; Flasar, F. M.; French, R. G.; Iess, L.; Marouf, E. A.; Nagy, A. F.

2004-12-01

449

Optical Variability of the Radio Source J 1128+5925  

E-print Network

Very recently, J 1128+5925 was found to show strong intraday variability at radio wavelengths and may be a new source with annual modulation of the timescale of its radio variability. Therefore, its radio variability can be best explained via interstellar scintillation. Here we present the properties of its optical variability for the first time after a monitoring program in 2007 May. Our observations indicate that in this period J 1128+5925 only showed trivial optical variability on internight timescale, and did not show any clear intranight variability. This behavior is quite different from its strong radio intraday variability. Either this object was in a quiescent state in optical in this period, or it is intrinsically not so active in optical as it is in radio regimes.

Jianghua Wu; Xu Zhou; Jun Ma; Zhenyu Wu; Zhaoji Jiang; Jiansheng Chen

2007-10-08

450

Photodetectors for Scintillator Proportionality Measurement  

SciTech Connect

We evaluate photodetectors for use in a Compton Coincidence apparatus designed for measuring scintillator proportionality. There are many requirements placed on the photodetector in these systems, including active area, linearity, and the ability to accurately measure low light levels (which implies high quantum efficiency and high signal-to-noise ratio). Through a combination of measurement and Monte Carlo simulation, we evaluate a number of potential photodetectors, especially photomultiplier tubes and hybrid photodetectors. Of these, we find that the most promising devices available are photomultiplier tubes with high ({approx}50%) quantum efficiency, although hybrid photodetectors with high quantum efficiency would be preferable.

Moses, William W.; Choong, Woon-Seng; Hull, Giulia; Payne, Steve; Cherepy, Nerine; Valentine, J.D.

2010-10-18

451

Laboratory Studies of Lead Removal from Liquid Scintillator in Preparation for KamLAND's Low Background Phase  

SciTech Connect

The removal of Radon induced Lead from liquid scintillator was extensively studied in preparation for KamLAND's low background phase. This work presents the results from laboratory experiments performed at the University of Alabama and their implications for KamLAND and future low background experiments using carbon based liquid scintillator. It was observed that distillation was the most effective purification procedure and that one must consider a non-polar and non-ionic component of Lead in order to reach the levels of radio-purity required for these new class of ultra-low background experiments.

Keefer, Gregory [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

2011-04-27

452

Binderless composite scintillator for neutron detection  

DOEpatents

Composite scintillator material consisting of a binderless sintered mixture of a Lithium (Li) compound containing .sup.6Li as the neutron converter and Y.sub.2SiO.sub.5:Ce as the scintillation phosphor, and the use of this material as a method for neutron detection. Other embodiments of the invention include various other Li compounds.

Hodges, Jason P [Knoxville, TN; Crow, Jr; Lowell, M [Oak Ridge, TN; Cooper, Ronald G [Oak Ridge, TN

2009-03-10

453

The most powerful scintillator supernovae detector: LVD  

Microsoft Academic Search

Summary The Large Volume Detector (LVD) in the Gran Sasso underground Laboratory is a multipurpose detector consisting of a large volume of liquid scintillator interleaved with limited streamer tubes. In this paper we discuss its power to study low-energy cosmic neutrinos. The results show that the first LVD tower (368 tons of liquid scintillator) is well suited to detect neutrinos

M. Aglietta; B. Alpat; E. D. Alyea; P. Antonioli; G. Anzivino; G. Badino; Y. Ban; G. Bari; M. Basile; A. Benelli; V. S. Berezinsky; L. Bergamasco; S. Bianco; A. Bizzetti; G. Bruni; Y. Cao; G. Cara Romeo; R. Casaccia; C. Castagnoli; A. Castellina; K. Chen; R. Chen; J. A. Chinellato; L. Cifarelli; G. Cini; S. Cong; A. Contin; V. L. Dadikin; M. Dardo; A. De Silva; M. Deutsch; L. G. Dos Santos; R. I. Enikeev; F. L. Fabbri; W. Fulgione; P. Galeotti; P. L. Ghia; P. Giusti; F. Grianti; S. Gu; E. S. Hafen; P. Haridas; G. Iacobucci; N. Inoue; F. F. Khalchukov; E. V. Korolkova; P. V. Kortchaguin; V. B. Kortchaguin; V. A. Kudryavtsev; G. Landi; K. Lau; X. Lin; L. Lu; J. Ma; Z. Ma; G. Maccarrone; A. S. Malguin; Z. Mao; M. A. Markov; T. Massam; B. Mayes; N. Mengotti Silva; A. Misaki; G. H. Mo; B. Monteleoni; C. Morello; J. Moromisato; R. Nania; G. Navarra; L. Panaro; D. Parks; P. G. Pelfer; L. Periale; P. Picchi; P. Pinna; L. Pinsky; I. A. Pless; M. Pu; J. Pyrlyk; J. Qiu; V. G. Ryasny; O. G. Ryazhskaya; O. Saavedra; K. Saitoh; D. Sanders; G. Sartorelli; S. Sarwar; D. Shen; V. P. Talochkin; H. Tang; J. Tang; W. Tian; G. C. Trinchero; A. Turtelli; I. Uman; P. Vallania; S. Vernetto; E. von Goeler; L. Votano; T. Wada; F. Wang; H. Wang; S. Wang; R. Weathers; R. Weinstein; M. Widgoff; L. Xu; Z. Xu; V. F. Yakushev; I. Yamamoto; G. Yi; A. Zallo; G. T. Zatsepin; X. Zhou; Q. Zhu; X. Zhu; B. Zhuan; A. Zichichi

1992-01-01

454

A study of intense ionospheric scintillation observed during a quiet day in the East African low-latitude region  

NASA Astrophysics Data System (ADS)

Ionospheric plasma density irregularities are a common feature of the equatorial and low-latitude ionosphere. These irregularities are known to cause fading and phase fluctuation (scintillation) of L-band radio navigation signals such as those used by Global Navigation Satellite Systems. This study investigates the occurrence of intense ionospheric scintillation in the postsunset period during a geomagnetically quiet day on 8 April 2011. In particular, we use Global Positioning System (GPS) derived observations, i.e., total electron content (TEC) and amplitude scintillation intensity index, S4, to examine the occurrence of intense scintillations at two low-latitude stations in the East African sector. Deep TEC depletions, in some cases roughly 40 TECU, are observed consistently with the occurrence of intense scintillations. In addition, we compare the GPS-based observations to the Communication/Navigation Outage Forecasting System (C/NOFS) satellite plasma data. The intense scintillation events also correspond well with plasma depletion structures present on the C/NOFS observations and can be attributed to strong plasma bubble activity. The C/NOFS data also provide evidence of strong upward drift velocities (> 60 m/s) associated with the depletions, which may have contributed to the generation of the strong irregularities.

Ngwira, Chigomezyo M.; Klenzing, Jeff; Olwendo, Joseph; D'ujanga, Florence M.; Stoneback, Russell; Baki, Paul

2013-07-01