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1

Morphology of auroral zone radio wave scintillation  

Microsoft Academic Search

This paper describes the morphology of midnight sector and morning sector auroral zone scintillation observations made over a two-year period using the Wideband satelite, which is in a sun-synchronous, low-altitude orbit. No definitive seasonal variation was found. The nighttime data showed the highest scintillation ocurrence levels, but significant amounts of morning scintillation were observed. For the most part the scintillation

C. L. Rino; S. J. Matthews

1980-01-01

2

Radio wave phase scintillation and precision Doppler tracking of spacecraft  

Microsoft Academic Search

Phase scintillation caused by propagation through solar wind, ionospheric, and tropospheric irregularities is a noise process for many spacecraft radio science experiments. In precision Doppler tracking observations, scintillation can be the dominant noise process. Scintillation statistics are necessary for experiment planning and in design of signal processing procedures. Here high-precision tracking data taken with operational spacecraft (Mars Observer, Galileo, and

J. W. Armstrong

1998-01-01

3

Scintillation Effects on Radio Wave Propagation Through Solar Corona  

Microsoft Academic Search

When RF waves pass through the solar corona and solar wind regions close to the Sun, strong scintillation effects appear at their amplitude, frequency and phase, especially in the regions very close to the Sun (less than 4 solar radius). After analyzing recent solar corona conjunction experimental data at S, X and Ka bands, we have developed a group of

C. M. Ho; M. K. Sue; A. Bedrossian; R. W. Sniffin

4

The effect of wind velocity on the amplitude scintillations of millimetre radio waves  

Microsoft Academic Search

The effect of transverse wind velocity on the amplitude scintillations of millimeter radio waves is studied. Scintillation data obtained on two line-of-sight microwave links at 36 GHz and 110 GHz on a common 4.1 km path are used to estimate the wind velocity perpendicular to the propagation path. The estimated wind velocity is within 20% of the value obtained from

K. L. Ho; R. S. Cole; N. D. Mavrokoukoulakis

1978-01-01

5

Radio Wave Scintillation in the Neutral Atmosphere as Noise in Precision Spacecraft Tracking Observations  

Microsoft Academic Search

Tropospheric phase scintillation degrades the coherence of a radio link and thus introduces noise in interferometer observations and spacecraft Doppler tracking experiments. High-quality Doppler data were taken in March-April 1993 with the Mars Observer spacecraft when it was in interplanetary cruise (sun-earth-spacecraft angle ~100 degrees; earth-spacecraft distance ~500 light seconds). The radio wave phase residuals from these tracks can be

J. W. Armstrong

1996-01-01

6

Attenuation and scintillation of radio waves in the Earth's atmosphere from radio occultation experiments on satellite-to-  

Microsoft Academic Search

A theoretical analysis of refractive loss of radio waves by the Earth's atmosphere in radio occultation measurements along the satellite-to-satellite line for various altitude profiles of the refractive index is given. Experimental results for refractive loss on the orbital spacecraft - geostationary satellite link are presented. Theoretical calculations are compared with experimental data, and a conclusion is drawn that the

O. I. Yakovlev; I. A. Vilkov

1995-01-01

7

Attenuation and scintillation of radio waves in the Earth's atmosphere from radio occultation experiments on satellite-to-satellite links  

Microsoft Academic Search

A theoretical analysis of refractive loss of radio waves by the Earth's atmosphere in radio occultation measurements along the satellite-to-satellite line for various altitude profiles of the refractive index is given. Experimental results for refractive loss on the orbital spacecraft-geostationary satellite link are presented. Theoretical calculations are compared with experimental data, and a conclusion is drawn that the signal amplitude

O. I. Yakovlev; S. S. Matyugov; I. A. Vilkov

1995-01-01

8

A radio wave scattering algorithm and irregularity model for scintillation predictions  

NASA Astrophysics Data System (ADS)

An algorithm for calculations of phase and amplitude scintillation of satellite signals in the equatorial region will be described in detail. The algorithm will be developed by initially transforming the discrete version of the Huygens-Fresnel integral into a convolution involving a series of coefficients with decreasing amplitudes. Next, the Fourier transform of the corresponding series of coefficients is stored for all the frequencies of interest, and the fast Fourier transform algorithm is used to evaluate discrete convolutions. Two phase screen models will be described. The first assumes that the phase fluctuations of the wave front emerging from the bottom of the irregularity layer are proportional to electron density fluctuations directly obtained from satellite in situ measurements. The second assumes that the same phase fluctuations can be obtained from their power spectral densities and phase spectra, represented by analytical functions with parameters provided by physics-based or morphological models of ionospheric irregularities. The propagation algorithm will be applied to both phase screen models, assuming five frequencies in the high-VHF to low-SHF band (suffering strong to weak scattering), to display its potential in the prediction of phase and amplitude scintillation of satellite signals.

Costa, Emanoel; Basu, Santimay

2002-06-01

9

Model computations of radio wave scintillation caused by equatorial ionospheric bubbles  

Microsoft Academic Search

In situ data measured on board AE satellites and rockets reveal spiky and wedgelike electron density structures inside the equatorial ionospheric bubbles. Two models are constructed to simulate the initial stage and fully developed stage of a bubble. Effects of radio propagation through such bubbles are simulated by solving the parabolic equation numerically. The results show that even though the

A. W. Wernik; C. H. Liu; K. C. Yeh

1980-01-01

10

Radio wave.  

PubMed

In developing countries with high rates of poverty and illiteracy, radio is emerging as an excellent medium for delivering information on health issues, family planning, nutrition, and agricultural development. Since radio does not require wired electricity, it can reach remote rural populations. Surveys have found that between 50-75% of poor rural households in developing countries own radios, and the majority listen to educational radio at least once a week. A program that reaches the urban poor outside of Lima, Peru, has been instrumental in controlling the spread of cholera. A Bolivian station broadcasts 8 hours of literacy, health, agricultural, and cultural programming a day to an audience of more than 2 million Aymara Indians. Small village radio stations with a broadcast range of 15 miles can be established for under US$400 and can generally achieve sustainability through local fundraising events such as raffles. In many cases, listeners have become broadcasters at their local radio stations. PMID:12286181

Elkin, V

11

Riding the Radio Waves  

NSDL National Science Digital Library

Through this lesson 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 a given waveform. Students then learn general concepts about magnetic fields, leading into how radio waves are created and transmitted. Several demonstrations can be performed in order to help students better understand these concepts. The goal of this lesson is for students to understand how the AM radios built during the associated activity function.

Techtronics Program

12

Scintillation and Absorption of Radio Waves in the Earth's Atmosphere in Radio Occultation Experiments on the Satellite-to-Satellite Link  

Microsoft Academic Search

A radio occultation experiment where both transmitter and receiver are above troporpheric characteristic altitudes and at long distances from each other has been performed. Results from such a satellite-to-satellite link are analyzed.

I. A. Vilkov; S. S. Matyugov; O. I. Yakovlev

1996-01-01

13

Multiple phase screen modeling of ionospheric scintillation along radio occultation raypaths  

NASA Astrophysics Data System (ADS)

We present the Radio Occultation Scintillation Simulator (ROSS), which uses the multiple phase screen method (MPS) to simulate the forward scatter of radio waves by irregularities in the equatorial ionosphere during radio occultation experiments. ROSS simulates propagation through equatorial plasma bubbles which are modeled as homogeneous electron density fluctuations modulated by a Chapman profile in altitude and a Gaussian window in the magnetic east-west direction. We adjust the parameters of the density model using electron density profiles derived from the ALTAIR incoherent scatter radar (9.4°N, 167.5°E, 4.3° north dip), and space-to-ground observations of scintillation using VHF and GPS receivers that are colocated with the radar. We compare the simulated occultation scintillation to observations of scintillation from the CORISS instrument onboard the C/NOFS satellite during a radio occultation occurring near ALTAIR on 21 April 2009. The ratio of MPS predicted S4 to CORISS observed S4 throughout the F region altitudes of 240-350 km ranged between 0.86 and 1.14.

Carrano, Charles S.; Groves, Keith M.; Caton, Ronald G.; Rino, Charles L.; Straus, Paul R.

2011-12-01

14

Effect of solar variability on transionospheric radio wave propagation in the equatorial region  

Microsoft Academic Search

Growth of plasma instabilities in the post-sunset equatorial ionospheric F region gives rise to irregularities known by the generic name: equatorial spread F (ESF), which scatter incident VHF or higher frequency radio waves to produce scintillations on trans-ionospheric radio waves. Changes in large scale (> 10 km) electron density distribution in the equatorial and low latitude ionosphere due to electrodynamic

A. Bhattacharyya; B. Engavale; D. Tiwari; S. Bose

2006-01-01

15

HF produced ionospheric electron density irregularities diagnosed by UHF radio star scintillations  

SciTech Connect

HF-waves incident on an overdense (HF-frequency < penetration frequency) ionosphere are known to produce large scale electron density irregularities. It is predicted that similar irregularities are formed during underdense HF-modification. The propagation of UHF radio waves originating from radio stars will be affected by such irregularities in the ionosphere. The interest in a scintillation experiment is twofold. One may obtain information on the electron density irregularies and one may learn about the propagation of radio waves through such a perturbed medium. A thin screen (diffractive) theory is derived which allows to draw conclusons on the electron density irregularities from the intensity fluctuations measured on the ground if the phase perturbations are much less than one radian. Since radio stars suitable for scintillation measurements at UHF are very faint an antenna with a large collection area is required. The observations reported in this dissertation were performed with the 300m diameter spherical reflector of the Arecibo Observatory. Successful observations were performed at 430 MHz and at 1400 MHz. Intensity fluctuations at such high frequencies measured with a large antenna suffer severe filtering in the thin phase screen regime. The theory presented in this dissertation includes these filtering effects. Many observations agree with the predictions of that theory. Some observations indicate that refraction effects have to be included to explain the data. HF-induced electron density irregularities were only observed during overdense heating.

Alfred, F.

1982-01-01

16

Interstellar Seeing. I. Superresolution Techniques Using Radio Scintillation  

Microsoft Academic Search

Interstellar scintillation can be used to probe transverse sizes of radio\\u000asources on scales inaccessible to the nominal resolution of any terrestrial\\u000atelescope, e.g. $\\\\lesssim 10^{-6}$ arc sec. Methodology is presented that\\u000aexploits this superresolution phenomenon for both single aperture and\\u000ainterferometer observations. The treatment applies to the saturated\\u000a(strong-scattering) regime and holds for both thin screens and extended media.

J. M. Cordes

2000-01-01

17

Interstellar Seeing. I. Superresolution Techniques Using Radio Scintillation  

Microsoft Academic Search

Interstellar scintillation can be used to probe transverse sizes of radio sources on scales inaccessible to the nominal resolution of any terrestrial telescope, e.g. $\\\\lesssim 10^{-6}$ arc sec. Methodology is presented that exploits this superresolution phenomenon for both single aperture and interferometer observations. The treatment applies to the saturated (strong-scattering) regime and holds for both thin screens and extended media.

J. M. Cordes

2000-01-01

18

Application of refractive scintillation theory to radio transmission through the ionosphere and the solar wind, and to reflection from a rough ocean  

Microsoft Academic Search

The theory of diffractive scattering by small-scale irregularities is combined with the results of Booker and MajidiAhi (1981) concerning refractive scattering by large-scale irregularities in a phase-changing screen, in a study of three intensity scintillation phenomena: (1) the reflection of radio and optical waves from an ocean surface disturbed by a spectrum of water waves; (2) the scintillation of VHF,

H. G. Booker

1981-01-01

19

Characterization of Ionospheric Scintillation Using Simultaneous Formosat-3/COSMIC Radio Occultation Observations and AFRL SCINDA Ground Scintillation Measurements  

NASA Astrophysics Data System (ADS)

Ionospheric scintillation at low latitudes has been studied using ionospheric radio occultation (RO) measurements by the FORMOSAT-3/COSMIC micro-satellites in conjunction with ground-based data from the Scintillation Network Decision Aid (SCINDA) station at Kwajalein Atoll. The Air Force Research Laboratory has developed the SCINDA network for monitoring low-latitude ionospheric total electron content (TEC) and scintillation associated with equatorial spread F. The network currently consists of sixteen stations distributed around the globe and the data have been used to conduct numerous studies on the characteristics and climatology of equatorial scintillation. The present study focuses on COSMIC RO and SCINDA data during the three COSMIC campaigns in 2006. Radio occultation events are selected by requiring that ionospheric scintillation was detected by the SCINDA VHF scintillation monitor at Kwajalein, and that the occultation ray path intersected the Kwajalein longitude below the satellite altitude, which varied from 500 to 800 km for the six FORMOSAT-3 satellites. In order to exclude tropospheric effects, only GPS signal amplitudes from FORMOSAT-3 with ray path tangent altitudes above 100 km are considered. Locations of ionospheric scintillation are estimated by triangulation using the satellites and the SCINDA ground station. Airglow images at Kwajalein are also used to confirm occurrence of equatorial ionospheric scintillations. For the selected events, large amplitude L1 and L2 scintillations tend to occur at altitudes below 200 km at frequencies around 0.5 Hz. The results are discussed as a potential path toward better specifying the occurrence of equatorial scintillations.

Starks, M. J.; Lin, C. S.; Groves, K. M.; Pedersen, T. R.; Basu, S.; Syndergaard, S.; Rocken, C.

2007-05-01

20

Propagation of Radio Waves in the Corona and Solar Wind  

NASA Astrophysics Data System (ADS)

The solar corona and solar wind are plasmas characterized by large scale MHD structures, waves, and turbulence. These introduce both systematic and random variations in the refractive index which affect the propagation of radio waves. A variety of propagation phenomena occur -- regular refraction; angular, temporal, and spectral broadening; scintillations in amplitude and phase -- widely referred to as scattering phenomena. In this tutorial I review the physical basis of these phenomena and describe a variety of techniques designed to exploit observations of scattering phenomena to deduce properties of the corona and solar wind plasma.

Bastian, T. S.

21

Effect of solar variability on transionospheric radio wave propagation in the equatorial region  

NASA Astrophysics Data System (ADS)

Growth of plasma instabilities in the post-sunset equatorial ionospheric F region gives rise to irregularities known by the generic name: equatorial spread F (ESF), which scatter incident VHF or higher frequency radio waves to produce scintillations on trans-ionospheric radio waves. Changes in large scale (> 10 km) electron density distribution in the equatorial and low latitude ionosphere due to electrodynamic effects associated with magnetic storms, influence the generation of ESF irregularities as seen in the pattern of occurrence of nighttime equatorial scintillations that may be specifically linked with magnetic activity. Besides such effects due to transient solar events, it is well known that the probability of occurrence of ionospheric scintillations caused by ESF irregularities as well as the strength of these scintillations during different phases of the solar cycle show a significant modulation of the generation and evolution of these irregularities by solar cycle related changes in the ionosphere and thermosphere. Evolution of spatial structure in the ESF irregularities determines the spatial scales that occur in the ground scintillation pattern during different phases of a scintillation event, and these spatial scales together with the dynamics of the irregularities determine the extent of degradation of transionospheric radio signals. Solar cycle effects on the structure and dynamics of ESF irregularities and hence on degradation of transionospheic radio signals during magnetically quiet periods, as also the effect of magnetic activity on the generation of ESF irregularities are discussed here on the basis of long term spaced receiver scintillation observations at an equatorial location.

Bhattacharyya, A.; Engavale, B.; Tiwari, D.; Bose, S.

22

RADIO-WAVE METHOD OF GEOLOGICAL MAPPING  

Microsoft Academic Search

Practical methods of using radio waves in geological mapping are considered. The history and basic principles of the method are briefly outlined. When transmitted radio waves penetrate the earth to a definite depth, they induce currents in the heterogeneous geological structures encountered (ore veins, contacts of different rocks, ground-water lenses, for example). The electromagnetic fields of these currents superimposed on

A. D. Frolov

1961-01-01

23

The Cassini Radio and Plasma Wave Investigation  

Microsoft Academic Search

The Cassini radio and plasma wave investigation is designed to study radio emissions, plasma waves, thermal plasma, and dust in the vicinity of Saturn. Three nearly orthogonal electric field antennas are used to detect electric fields over a frequency range from 1 Hz to 16 MHz, and three orthogonal search coil magnetic antennas are used to detect magnetic fields over

D. A. Gurnett; W. S. Kurth; D. L. Kirchner; G. B. Hospodarsky; T. F. Averkamp; P. Zarka; A. Lecacheux; R. Manning; A. Roux; P. Canu; N. Cornilleau-Wehrlin; P. Galopeau; A. Meyer; R. Boström; G. Gustafsson; J.-E. Wahlund; L. Åhlen; H. O. Rucker; H. P. Ladreiter; W. Macher; L. J. C. Woolliscroft; H. Alleyne; M. L. Kaiser; M. D. Desch; W. M. Farrell; C. C. Harvey; P. Louarn; P. J. Kellogg; K. Goetz; A. Pedersen

2004-01-01

24

Radio Waves and the Living Organism.  

National Technical Information Service (NTIS)

The possible effects of radio waves, from various sources including natural and instrumental, on humans are examined. The effects of various lengths, frequencies, and time of exposure were also examined. Efforts were made to determine how man can be prote...

Y. V. Sebrant M. P. Troyanskii

1972-01-01

25

Speckles in interstellar radio-wave scattering  

Microsoft Academic Search

Observations of speckles in the scattering disk of the Vela pulsar are presented and speckle techniques for studying and circumventing scattering of radio waves by the turbulent interstellar plasma are discussed. The speckle pattern contains, in a hologrammatic fashion, complete information on the structure of the radio source as well as the distribution of the scattering material. Speckle observations of

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

1991-01-01

26

Introducing Radio-Wave Propagation with Hypercard  

Microsoft Academic Search

An educational software developed for the introduction to radio-wave propagation is presented. Based on the HyperCard authoring system, the software is designed around the modelization of a classical radio or microwave link. Used in a continuing education program, organized for technicians and engineers involved more in the practical than in the theoretical aspects of propagation, this software greatly helps for

R. Crampagne; M. Helier; W. Tabbara

1992-01-01

27

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.

28

Interplanetary scintillations of strong radio sources in the descending phase near the cycle 23 minimum  

NASA Astrophysics Data System (ADS)

Observations of interplanetary scintillations of the 3C 298 and 3C 48 radio sources during low solar activity, performed with a BSA FIAN radio telescope at a frequency of 111 MHz, are presented. The radial dependences of the scintillation indices, where the effect of a low-latitude heliospheric current sheet is observed, have been obtained. Based on the scintillation temporal spectra, the solar wind velocity values have been obtained, and it has been indicated that these values are in good agreement with those found using the spaced measurements method.

Glubokova, S. K.; Glyantsev, A. V.; Tyul'Bashev, S. A.; Chashei, I. V.; Shishov, V. I.

2011-12-01

29

Reconstruction of ionospheric irregularities using transionospheric radio waves  

NASA Astrophysics Data System (ADS)

Several approaches which use trans-ionospheric radio signals to study the fine structures of ionospheric irregularities are presented. Based on the theory of wave propagation in a random media, the statistical scintillation theory relates the statistics of the observed radio signal to the statistical characteristics of the irregularities; first and second order statistical quantities, such as mean square fluctuations of electron density, as well as the correlation and power spectra of the irregularities can be inferred from the data. Reconstruction by inverse propagation involves the use of simultaneous phase and amplitude information for multi-frequency coherent beacon signals to reconstruct irregularities similar to the optical synthetic holograms. Snap pictures of the fluctuating structures from this approach are provided, and examples of both approaches are given.

Liu, C. H.; Yeh, K. C.

30

Enhanced Specification of the Equatorial Ionospheric Scintillation Environment with Satellite Radio Beacons  

Microsoft Academic Search

Remote sensing of radio signals from low-Earth orbiting (LEO) satellites provides a wealth of information on the presence and location of disturbances in the equatorial ionosphere which result in scintillations. Results will be presented emphasizing the statistical improvements provided to existing ionospheric specification models with the assimilation of measurements from the Coherent Electromagnetic Radio Tomography (CERTO) beacon onboard the Communication\\/Navigation

R. G. Caton; K. M. Groves; M. Verlinden

2010-01-01

31

Polarization Parameters of the Downcoming Radio Wave  

Microsoft Academic Search

The phase difference between the normal and the abnormal components of the magnetic vector of the radio wave (i.e., the components in and at right angles to the plane containing the wave normal and the direction of the earth's magnetic field) and the limits of the tilt angle of the major axis of the polarization ellipse (traced out by the

Y. S. N. Murty; S. R. Khastgir

1960-01-01

32

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

33

Huygen's principle applied to radio wave propagation  

Microsoft Academic Search

Huygen's principle, in the form of boundary integral equations, is applied to the problem of radio wave propagation. Complex propagation is analyzed by dividing the region between transmitter and receiver into a number of zones and propagating the solution between these zones by means of integral equations with simple approximate kernels. In the limit that the regions become dense, the

C. J. Coleman

2002-01-01

34

The propagation of radio waves in the terrestrial environment  

Microsoft Academic Search

The propagation of a radio wave from a transmitter to an antenna, with one of the two imbedded in the neutral or ionized earth atmosphere, is examined. Attention is given to the propagation of radio waves through an unobstructed space, such as occurs with microwave communications and radar. The theoretical basis for radio wave propagation is reviewed, as are the

L. Boithias

1983-01-01

35

Radio wave loss deviation and shadow loss at 900 MHz  

Microsoft Academic Search

Radio wave propagation between base and mobile stations is normally described as being Rayleigh distributed due to multipath radio wave combining. When the number of radio wave paths are limited the variation in received signal amplitude frequently follows a more general case given by a Weibull distribution. A significant portion of the Weibull distribution is defined as the transmission loss

NEAL H. SHEPHERD

1977-01-01

36

Forecasting low-latitude radio scintillation with 3-D ionospheric plume models: 1. Plume model  

Microsoft Academic Search

A three-dimensional model has been developed for the plasma plumes caused by interchange instabilities in the low-latitude ionosphere to describe the structure and extent of the radio scintillation generated by turbulence in and around the plumes (down to the scale sizes resolvable by the computer model). With the inclusion of the processes that determine the transport of plasma parallel to

J. M. Retterer

2010-01-01

37

Radio and plasma waves at the outer planets  

Microsoft Academic Search

We review our present knowledge of plasma waves and non-thermal radio emissions at the outer planets. The review mainly concerns waves linked to electron dynamics. After a summary of the basics of radio and plasma wave modes as derived from the theory and from observations in the Earth's vicinity, we discuss the counterpart of these waves as observed in outer

P. Zarka

2004-01-01

38

Radio Wave Reflections in the Troposphere  

Microsoft Academic Search

IN recent publications, Friend and Colwell1,2 have reported the reflection of radio waves at vertical incidence from temperature inversions in the troposphere, and have estimated the reflection coefficient to be of the order of 10-3 at a frequency of 2398 kc.\\/s. On the assumption that atmospheric reflections are due to discontinuities in water content, Piddington3 has calculated the reflection coefficient

L. G. Stoodley

1940-01-01

39

Using millimeter radio waves to probe the earth's atmosphere  

Microsoft Academic Search

We analyze the unique features involved in employing millimeter radio waves to investigate and monitor the earth's atmosphere by means of radio transmissions involving the use of two satellites. We discuss the absorption of radio waves in the atmosphere along the path of the two satellites, depending on the wavelength and the time of year. Signal attenuation is analyzed in

S. D. Eliseev; O. I. Yakovlev

1989-01-01

40

Studies of radio-wave propagation in the solar system  

Microsoft Academic Search

A review is given of studies of radio-wave propagation in the solar system that were conducted from 1963 to 1973 with the Soviet spacecraft Venera, Mars, and Luna. Results are presented for satellite radio-occultation investigations of the Martian atmosphere. Properties of radio-wave propagation in the dense atmosphere of Venus, involving a radio link with descending spacecraft, are examined along with

M. A. Kolosov; O. I. Iakovlev

1975-01-01

41

Anomalous radio wave absorption due to ionospheric heating effects  

Microsoft Academic Search

An ionospheric volume in the F layer subjected to high power high frequency illumination is observed to be an effective scattering medium for radio signals. Experimental results are representative of a field-aligned scattering geometry. Scatter of the incident wave into electrostatic waves by these strongly field-aligned density irregularities is considered. This model explains the large decreases in radio wave reflectivity

Kristine N. Graham; J. A. Fejer

1976-01-01

42

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

43

Modifying the ionosphere with intense radio waves.  

PubMed

The ionospheric modification experiments provide an opportunity to better understand the aeronomy of the natural ionosphere and also afford the control of a naturally occurring plasma, which will make possible further progress in plasma physics. The ionospheric modification by powerful radio waves is analogous to studies of laser and microwave heating of laboratory plasmas (20). " Anomalous" reflectivity effects similar to the observed ionospheric attenuation have already been noted in plasmas modulated by microwaves, and anomalous heating may have been observed in plasmas irradiated by lasers. Contacts have now been established between the workers in these diverse areas, which span a wide range of the electromagnetic spectrum. Perhaps ionospheric modification will also be a valuable technique in radio communications. PMID:17778050

Utlaut, W F; Cohen, R

1971-10-15

44

Interplanetary scintillations of an ensemble of radio sources during the solar activity minimum of cycles 23/24  

NASA Astrophysics Data System (ADS)

The results of observations of interplanetary scintillations of a statistical ensemble of radio sources in the period of 2007-2011 are presented. Observation were carried out in the monitoring regime with the BSA LPI radio telescope at the frequency 111 MHz. Fluctuations of radio emission flux of all sources (a few hundred in total) were recorded 24 hours a day. Those sources were investigated, which had a scintillating flux greater than 0.2 Jy and fell within the sky band of 8° width in declination, corresponding to radio telescope's 16-beam system. The statistical ensemble of radio sources is characterized by the mean variance of a scintillating radiation flux, which is proportional to the squared scintillation index. It follows from the obtained data that the radial dependence of a mean scintillation index during a deep solar activity minimum of 2008-2009 occurs to be weaker than one could expect in the case of spherically symmetric geometry of the solar wind. Suppression of a radial dependence of the mean scintillation index is explained by the effect of the heliospheric current sheet, which reveals itself in a high density of solar wind's turbulent plasma in the helioequator plane. It is shown that the level of scintillations, averaged over monthly series of observations, was changing synchronously with the solar activity level.

Chashei, I. V.; Shishov, V. I.; Tyul'bashev, S. A.; Glyantsev, A. V.; Subaev, I. A.

2013-01-01

45

Using TEC and radio scintillation data from the CITRIS radio beacon receiver to study low and midlatitude ionospheric irregularities  

NASA Astrophysics Data System (ADS)

Unique data on ionospheric plasma irregularities from the Naval Research Laboratory Scintillation and TEC Receiver in Space (CITRIS) instrument is presented. CITRIS is a multiband receiver that recorded Total Electron Content (TEC) and radio scintillations from Low-Earth Orbit (LEO) on STPSat1. The 555 ± 5 km altitude 35° inclination orbit covers low and midlatitudes. The measurements require propagation from a transmitter to a receiver through the F region plasma. CITRIS used both 1) satellite beacons in LEO and 2) the French sponsored global network of ground-based Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) beacons. This paper is both a brief review of the CITRIS experiment and the first combined TEC and scintillation study of ionospheric irregularities using a satellite-borne beacon receiver. It primarily focuses on CITRIS/DORIS observations and is a case study of the ionospheric irregularities and associated scintillation characteristics at 401.25 MHz during the 2008 equinox solar minimum. In addition, CITRIS was operated in a complementary fashion with the Communication/Navigations Outages Forecasting System (C/NOFS) satellite during C/NOFS' first year of operations and comparison with measured C/NOFS irregularity characteristics are made. Several types of irregularities have been studied including Spread-F and the newly discovered dawn-side depletions.

Siefring, Carl L.; Bernhardt, Paul A.; Koch, Douglas E.; Galysh, Ivan J.

2011-12-01

46

Observations of equatorial plasma bubbles using broadcast VHF radio waves  

Microsoft Academic Search

The propagation of VHF radio waves affected by field-aligned irregularities within equatorial plasma bubbles is examined. Continuous observation of VHF radio waves at Tateyama, Japan, shows that broadcast radio waves transmitted from Southeast Asia propagate to Japan. Using a ray-tracing calculation combined with a model of scattering by field-aligned irregularities, we determined scatter points suitable for the reception of these

H. Nakata; I. Nagashima; K. Sakata; Y. Otsuka; Y. Akaike; T. Takano; S. Shimakura; K. Shiokawa; T. Ogawa

2005-01-01

47

Constraining the Vela Pulsar's Radio Emission Region Using Nyquist-limited Scintillation Statistics  

NASA Astrophysics Data System (ADS)

Using a novel technique, we achieve ~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.; Demorest, P.

2012-10-01

48

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

49

Interstellar scintillations and nanoarcsecond resolution in radio astronomy  

Microsoft Academic Search

Interstellar turbulent plasma can be considered to be a radio astronomy antenna—an interstellar diffraction grating, with\\u000a an aperture size roughly equal to the scattering-disk radius, R\\u000a \\u000a sc\\u000a = z\\u000a \\u000a eff\\u000a ?\\u000a sc\\u000a ? 1 AU (where z\\u000a \\u000a eff\\u000a is the effective distance and ?\\u000a \\u000a sc\\u000a the scattering angle). The angular resolution of this interstellar diffraction grating is of the order

V. I. Shishov

2010-01-01

50

Precipitation in relation to radio wave propagation studies in India  

Microsoft Academic Search

In this presentation efforts have been made to highlight the research work made on precipitation characterization and its effects on radio wave propagation particularly at frequency above 10 GHz over the Indian subcontinent. The work carried out on attenuation of radio wave due to water vapour, rain and cloud has been highlighted. To evolve better formulations suitable to tropical countries

S. K. Sarkar

2007-01-01

51

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

52

A search for Galactic compact radio sources - Scintillating sources at low Galactic latitudes  

NASA Astrophysics Data System (ADS)

A search for compact scintillating radio sources with angular sizes less than 1.5 arcsec in the region l = 34-71 deg, absolute value b less than or equal to 6 deg was performed at 102.5 MHz using the BSA telescope. A total of 58 scintillating sources were detected and 49 of them were observed as compact sources for the first time. Comparison with radio sources from standard catalogs reveals that three sources have one component, eight are unidentified, 37 have a complicated structure of core-halo type, and 10 may have a one-component or multicomponent structure. The five galactic sources include G 34.2+1.7, G 41.6-30, and 40.8-4.7. The nature of these sources is discussed. A strong dependence of angular sizes of sources on galactic coordinates is detected, indicating increased scattering in the galactic plane, especially in the arms. Eight new compact unidentified radio sources are noted that may be potential candidates for short-period quasars or peculiar galactic objects similar to SS 433.

Pynzar, A. V.; Udal'Tsov, V. A.

1989-10-01

53

Scintillation index of optical plane wave propagating through non-Kolmogorov moderate-strong turbulence  

NASA Astrophysics Data System (ADS)

An optical plane wave propagating through atmospheric turbulence is affected by irradiance fluctuations known as scintillation. The scintillation index of an optical wave in strong turbulence can be analyzed by extended Rytov theory, which uses filter functions to eliminate the effect of cell turbulence sizes that do not contribute to scintillation, and it already has been calculated by Kolmogorov's power spectral density model. However several experiments showed that Kolmogorov theory is sometimes incomplete to describe atmospheric turbulence properly. In this paper, for a horizontal path, we use extended Rytov theory to carry out plane wave scintillation index analysis in non Kolmogorov strong turbulence. We do it using a non Kolmogorov power spectrum which uses a generalized exponent factor and a generalized amplitude factor. Although our final expressions for the scintillation have been obtained by extended Rytov theory, which is necessary to adopt in strong turbulence conditions, they reduce to the proper results also in weak turbulence.

Toselli, Italo; Andrews, Larry C.; Phillips, Ronald L.; Ferrero, Valter

2007-10-01

54

Nonlinear Langmuir waves during type III solar radio bursts  

Microsoft Academic Search

Type III solar radio bursts are thought to be associated with intense levels of electron beam excited Langmuir waves. We numerically study the nonlinear evolution of these waves, in time and in two spatial dimensions, due to their coupling to other waves. For parameters appropriate to one-half the Earth-Sun distance, we find nonlinear effects to be important, as in previous

D. R. Nicholson; M. V. Goldman; P. Hoyng; J. C. Weatherall

1978-01-01

55

Making Waves: Pirate Radio and Popular Music.  

ERIC Educational Resources Information Center

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

Jones, Steve

56

Effect of blowing snow and ground blizzards on millimeter wave scintillation spectra  

NASA Astrophysics Data System (ADS)

We describe the effect of ground blizzards and blowing snow on millimeter wave scintillation spectra at 116 and 230 GHz. During snowstorms, multipath propagation can occur for various reasons. Whatever the reason for the multipath, it will affect the scintillation spectrum. Enhancement of the scintillation spectrum is observed at both low and high temporal frequencies. In some cases, two additional corner frequencies are evident at the high-frequency end of the scintillation spectrum. The method of obtaining the cross-path wind component fails when the wind is nearly parallel to the propagation path.

Sarma, A. D.; Hill, R. J.

1991-09-01

57

Plasma and radio waves from Neptune: Source mechamisms and propagation  

NASA Astrophysics Data System (ADS)

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

1994-07-01

58

Coronal Radio Sounding Experiments with Mars Express: Scintillation Spectra during Low Solar Activity  

SciTech Connect

Coronal radio sounding observations were carried out with the radio science experiment MaRS on the ESA spacecraft Mars Express during the period from 25 August to 22 October 2004. Differential frequency and log-amplitude fluctuations of the dual-frequency signals were recorded during a period of low solar activity. The data are applicable to low heliographic latitudes, i.e. to slow solar wind. The mean frequency fluctuation and power law index of the frequency fluctuation temporal spectra are determined as a function of heliocentric distance. The radial dependence of the frequency fluctuation spectral index alpha reflects the previously documented flattening of the scintillation power spectra in the solar wind acceleration region. Temporal spectra of S-band and X-band normalized log-amplitude fluctuations were investigated over the range of fluctuation frequencies 0.01 Hzscintillation data. Evidence for a weak increase in the fractional electron density turbulence level is obtained in the range 10-40 solar radii.

Efimov, A. I.; Lukanina, L. A.; Samoznaev, L. N.; Rudash, V. K. [Kotel'nikov Inst. Radio Engg. and Electronics, Russian Acad. Science, 125009 Moscow (Russian Federation); Chashei, I. V. [Lebedev Phys. Inst., Russian Acad. Science, 117924 Moscow (Russian Federation); Bird, M. K. [Argelander-Institut fuer Astronomie, Univ. Bonn, 53121 Bonn (Germany); Paetzold, M.; Tellmann, S. [Rheinisches Institut fuer Umweltforschung, Univ. Koeln, 50931 Koeln (Germany)

2010-03-25

59

Polarization of Radio Waves Reflected from the Inhomogeneous Ionosphere.  

National Technical Information Service (NTIS)

Calculations show that there is a very small difference between the true mean field polarization of radio waves reflected from the inhomogeneous ionosphere and that calculated using Stokes parameters. A Stokes parameter system is derived, from which the w...

Y. V. Morozov

1973-01-01

60

Radio evidence on shock wave formation in the solar corona  

Microsoft Academic Search

In order to investigate the formation of radio emitting shock waves above flaring active regions, we combine spectral and imaging observations of type II radio events with X-ray imaging and full-Sun observations and, in one case, with the extrapolated magnetic field configuration in the corona. We confirm and extend earlier findings that type II bursts are emitted above active region

A. Klassen; H. Aurass; K.-L. Klein; A. Hofmann; G. Mann

1999-01-01

61

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?

Tewksbury, Barb

62

Single scattering estimates for the scintillation function of waves in random media  

SciTech Connect

The energy density of high frequency waves propagating in highly oscillatory random media is well approximated by solutions of deterministic kinetic models. The scintillation function determines the statistical instability of the kinetic solution. This paper analyzes the single scattering term in the scintillation function. This is the term of the scintillation function that is linear in the power spectrum of the random fluctuations. We show that the structure of the scintillation function is already quite complicated in this simplified setting. It strongly depends on the singularity of the initial conditions for the wave field and on the correlation properties of the random medium. We obtain limiting expressions for the scintillation function as the correlation length of the random medium tends to zero.

Bal, Guillaume; Langmore, Ian [Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027 (United States); Pinaud, Olivier [CNRS, UMR 5208 Institut Camille Jordan/ISTIL, Universite de Lyon, Universite Lyon 1, Batiment du Doyen Jean Braconnier, 43, Blvd. du 11 Novembre 1918, F - 69622 Villeurbanne Cedex (France)

2010-02-15

63

Millimeter-Wave Carrier Generation System for Radio over Fiber  

Microsoft Academic Search

Due to the huge demand for the mm-wave band in future communication system applications, many researchers are investigating and continue working on the generation of millimeter-wave (mm-wave) signal for radio over fiber (RoF). RoF is an expanding technology that applicable in high channel capacity, wider service coverage and broadband mm-wave access system. However, the limited availability of the RF bands

N. Mohamed; S. M. Idrus; A. B. Mohammad; H. Harun

2008-01-01

64

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

65

Radio wave propagation below the Jovian ionosphere  

Microsoft Academic Search

The lightning and radio emission detector (LRD) instrument on board the Galileo probe measured the spectral intensity and other characteristics of radio frequency (RF) signals during descent. The measured spectra show a frequency dependent height profile with a maximum at the beginning of descent around the 1 bar level and a minimum around the 3-6 bar level [Rinnert et al.,

Klaus Rinnert; L. J. Lanzerotti

1998-01-01

66

Nonlinear scattering of radio waves by metal objects  

Microsoft Academic Search

Nonlinear scattering of radio waves by metal structures with resulting harmonic and intermodulation interference is analyzed from both theoretical and empirical standpoints, disregarding nonlinear effects associated with the nonlinear dependence of the electric or magnetic polarization vector on respectively the electric or magnetic field intensity in the wave propagating medium. Nonlinear characteristics of metal-oxide-metal contacts where the thin oxide film

V. B. Shteynshleyger

1984-01-01

67

Shock Waves and Radio Continuum in Miras  

NASA Astrophysics Data System (ADS)

We report a search for radio continuum emission from a sample of 34 Mira and semi-regular variable stars. The main aim of this survey was to look for thermal free-free emission from post-shock ionised gas. The stars were observed on November 3-5, 1995, at 4.8 and 8.6 GHz using the Australia Telescope Compact Array. Radio continuum emission was detected from one source only, the symbiotic Mira R Aqr, which is a well-known radio continuum source. No continuum emission was detected from the other sources with 3 sigma upper limits of typically 0.3 mJy. We have not either detected the Miras previously known to display radio continuum, including o Cet, R Aql and W Hya. Upper limits to radio brightness temperatures are determined. We discuss a simple model for strong shocks propagating in the inner envelopes of long-period variable stars and we derive simple formulae allowing to estimate the shock velocity from the observed radio continuum flux. From the upper limits to the radio flux densities we find no direct evidence for strong shocks with velocities above 25 km/s near two stellar radii, and we infer that the pulsation-driven stellar shocks generated in the stellar photospheres are strongly damped within a short radial distance from the stellar surface.

Chapman, J. M.; Rudnitskij, G. M.

68

Optical and millimeter-wave radio seamless MIMO transmission based on a radio over fiber technology.  

PubMed

Multi-input multi-output (MIMO) transmission of two millimeter-wave radio signals seamlessly converted from polarization-division-multiplexed quadrature-phase-shift-keying optical signals is successfully demonstrated, where a radio access unit basically consisting of only optical-to-electrical converters and a radio receiver performs total signal equalization of both the optical and the radio paths and demodulation with digital signal processing (DSP). Orthogonally polarized optical components that are directly converted to two-channel radio components can be demultiplexed and demodulated with high-speed DSP as in optical digital coherent detection. 20-Gbaud optical and radio seamless MIMO transmission provides a total capacity of 74.4 Gb/s with a forward error correction overhead of 7%. PMID:23388767

Kanno, Atsushi; Kuri, Toshiaki; Hosako, Iwao; Kawanishi, Tetsuya; Yoshida, Yuki; Yasumura, Yoshihiro; Kitayama, Ken-ichi

2012-12-31

69

Radio wave refractivity deduced from lidar measurements  

NASA Astrophysics Data System (ADS)

A high resolution lidar is used to backscatter light from atmospheric aerosols. The actual relative humidity is measured at altitudes corresponding to those from which the backscattered light occurs. A mathematical relationship between the two is then derived and this is used to predict atmospheric relative humidity from subsequent lidar backscatter's measurements. The predicted relative humidity is used with temperature and pressures derived from standard lapse rates to calculate the radio refractivity of the atmosphere. Radio ray coverage is then determined based upon the calculated radio refractivity.

Paulson, Merle R.; Hughes, Herbert G.

1993-12-01

70

Stabilization of magnetohydrodynamic modes by applied radio-frequency waves  

Microsoft Academic Search

A kinetic theory describing the nonlinear interaction of radio-frequency waves with low-frequency magnetohydrodynamic modes is presented. The calculation of the nonlinear force density on a fluid element includes both ponderomotive and sideband mode coupling terms and allows arbitrary rf wave polarization. Electromagnetic effects and wave--particle interactions are retained in the analysis. The influence of the nonlinear force on magnetohydrodynamic plasma

D. A. D'Ippolito; J. R. Myra

1986-01-01

71

Stabilization of magnetohydrodynamic modes by applied radio-frequency waves  

Microsoft Academic Search

A kinetic theory describing the nonlinear interaction of radio-frequency waves with low-frequency magnetohydrodynamic modes is presented. The calculation of the nonlinear force density on a fluid element includes both ponderomotive and sideband mode coupling terms and allows arbitrary rf wave polarization. Electromagnetic effects and wave–particle interactions are retained in the analysis. The influence of the nonlinear force on magnetohydrodynamic plasma

D. A. D’Ippolito; J. R. Myra

1986-01-01

72

Ionospheric modification by radio waves: An overview and novel applications  

Microsoft Academic Search

High-power high-frequency radio waves, when beamed into the Earth's ionosphere, can heat the plasma by particle collisions in the D-layer or generate wave-plasma resonances in the F-layer. These basic phenomena have been used in many research applications. In the D-layer, ionospheric currents can be modulated through conductance modification to produce artificial ULF and VLF waves, which propagate allowing magnetospheric research.

M. J. Kosch

2008-01-01

73

APPLICATION OF SMALL SATELLITES FOR HIGH PRECISION MEASURING EFFECTS OF RADIO WAVE PROPAGATION  

Microsoft Academic Search

The radio holography methodology may be applied in the scientific programs for future small satellite that will use radio signals emitted by radio navigation, radio communication satellites for precise measuring effects of radio waves propagation at low elevation angles and for global monitoring of radio communication channels passed through the atmosphere and ionosphere. Another task consists in monitoring of the

K. Igarashi; N. A. Armand; A. G. Pavelyev; Ch. Reigber; J. Wickert; K. Hocke; G. Beyerle; S. S. Matyugov; O. I. Yakovlev

74

Ionospheric applications of the scintillation and tomography receiver in space (CITRIS) mission when used with the DORIS radio beacon network  

NASA Astrophysics Data System (ADS)

The scintillation and tomography receiver in space (CITRIS) instrument will orbit the Earth near 560 km altitude to detect signals from the ground-based array of more than 50 DORIS UHF/S-band radio beacons established at sites around the world by the French Centre National d‘Etudes Spatiales (CNES) and the Institut Géographique National (IGN). The CITRIS receiver is on the US Air Force Space Test Program satellite STPSAT1, which is scheduled for launch in November 2006. CITRIS will record ionospheric total electron content (TEC) and radio scintillations with a unique ground-to-space geometry. The new instrument has been developed to study the ionosphere using data obtained with the UHF and S-band radio transmissions from the DORIS beacons because ionospheric radio scintillations can seriously degrade the performance of many space-geodetic systems, including the DORIS precise satellite orbitography system and GNSS (Global Navigation Satellite Systems). The ionospheric data will be based on radio signals sampled at a rate of 200 Hz by the CITRIS receiver. Numerical models have been used to predict that the DORIS signals measured by CITRIS may have 30 dB fluctuations in amplitude and 30 rad in phase as the satellite flies over kilometer-scale ionospheric structures. The data from the space-based CITRIS receiver will help update and validate theories on the generation and effect of ionospheric irregularities known to influence radio systems. By using simultaneous beacon transmissions from DORIS on the ground and from low-Earth-orbit beacons in space, the concept of reciprocity in a non-bilateral propagation medium like the ionosphere will be tested. Computer simulations are used to predict the magnitude of amplitude and phase scintillations that are expected to be recorded with the CITRIS instrument.

Bernhardt, Paul A.; Siefring, Carl L.; Galysh, Ivan J.; Rodilosso, Thomas F.; Koch, Douglas E.; MacDonald, Thomas L.; Wilkens, Matthew R.; Landis, G. Paul

2006-11-01

75

Radio-Wave Method for Geophysical Prospecting  

Microsoft Academic Search

The problem of ground wave propagation over a nonuniform overburden with arbitrarily varying complex dielectric coefficient and depth is analyzed. Using a full wave approach, the effects of the nonuniform overburden upon the surface wave and the radiation field are examined. The criteria for distinguishing between the effects of variations of the overburden depth and variations of its complex dielectric

E. Bahar

1971-01-01

76

Active control of edge localized modes by radio frequency waves  

NASA Astrophysics Data System (ADS)

The effect of radio frequency wave driven torque on edge localized mode (ELM) activity is studied. It is shown that the radio frequency driven torque causes transition of type I giant ELMs to the benign grassy ELM behavior. The efficiency of this process scales directly with minor radius and inversely with the plasma density. It is argued that the technique of active ELM control will be efficient in the present for moderate-sized machines and in the future for large machines.

Avinash, K.; Diamond, P. H.

2000-11-01

77

Ionospheric wave and irregularity measurements using passive radio astronomy techniques  

SciTech Connect

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. 10 references.

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

1988-06-01

78

Stimulated scattering of radio waves off acoustic waves in partially ionized plasmas  

Microsoft Academic Search

Stimulated scattering emchanisms involving electromagnetic and acoustic waves in a partially ionized plasma are considered. The growth rates and thresholds for three-wave decay interactions as well as modulational instabilities are obtained. The relevance of the investigation to the nonlinear propagation of powerful radio waves through the upper atmosphere is pointed out.

N. L. Tsintsadze; T. D. Buadze; P. K. Shukla; L. Stenflo

1990-01-01

79

Stimulated scattering of radio waves off acoustic waves in partially ionized plasmas  

Microsoft Academic Search

Stimulated scattering mechanisms involving electromagnetic and acoustic waves in a partially ionized plasma are considered. The growth rates and thresholds for three-wave decay interactions as well as modulational instabilities are obtained. The relevance of the investigation to the nonlinear propagation of powerful radio waves through the upper atmosphere is pointed out.

N. L. Tsintsadze; T. D. Buadze; P. K. Shukla; L. Stenflo

1990-01-01

80

Refractive Index Formulae for Radio Waves  

Microsoft Academic Search

The radio refractive index formula adopted in 1963 by the International Union of Geodesy and Geophysics (IUGG) and the International Association of Geodesy (IAG) is being reviewed. Forty years ago, this formula was essential for the reduction of distances measured with microwave EDM instruments. Since then, long-range EDM has been replaced by the Global Positioning System (GPS). Today, the formulae

Jean M. RÜEGER

2002-01-01

81

Radio wave propagation in potato fields  

Microsoft Academic Search

Reliable communication is crucial for successful de- ployment of wireless sensor networks. Therefore, it is important to understand the impact of environmental conditions on the performance of the radios (Chipcon CC1000 transceivers) used in typical sensor nodes. This paper reports on an extensive set of measurements taken in a potato field, where the foliage has an important effect on the

John Thelen; Daan Goense; Koen Langendoen

2005-01-01

82

MARTIAN ATMOSPHERIC EFFECTS ON RADIO WAVE PROPAGATION  

Microsoft Academic Search

Because Mars has very low atmospheric pressure (less than 1% of Earth's), the Martian atmospheric radio refractivity is about two orders of magnitude smaller than that of Earth. Ray bending effect on microwave is not obvious. The optical depths of Martian clouds and fogs are about 1 .O at visual wavelengths. In the limiting case, the Martian clouds are expected

C. M. Ho; M. K. Sue; N. Golshan

83

CLASSICAL AREAS OF PHENOMENOLOGY: Scintillation index of optical wave propagating in turbulent atmosphere  

NASA Astrophysics Data System (ADS)

A concise expression of the scintillation index is proposed for a plane optical wave and a spherical optical wave both propagating in a turbulent atmosphere with a zero inner scale and a finite inner scale under an arbitrary fluctuation condition. The expression is based on both the results in the Rytov approximation under a weak fluctuation condition and the numerical results in a strong fluctuation regime. The maximum value of the scintillation index and its corresponding Rytov index are evaluated. These quantities are affected by the ratio of the turbulence inner scale to the Fresnel size.

Rao, Rui-Zhong

2009-02-01

84

Correctability limitations imposed by plane-wave scintillation in multiconjugate adaptive optics.  

PubMed

Plane-wave scintillation is shown to impose multiconjugate adaptive optics (MCAO) correctability limitations that are independent of wavefront sensing and reconstruction. Residual phase and log-amplitude variances induced by scintillation in weak turbulence are derived using linear (diffraction-based) diffractive MCAO spatial filters or (diffraction-ignorant) geometric MCAO proportional gains as open-loop control parameters. In the case of Kolmogorov turbulence, expressions involving the Rytov variance and/or weighted C(2)(n) integrals apply. Differences in performance between diffractive MCAO and geometric MCAO resemble chromatic errors. Optimal corrections based on least squares imply irreducible performance limits that are validated by wave-optic simulations. PMID:16985544

Lee, Lawton H; Baker, Gary J; Benson, Robert S

2006-10-01

85

Correctability limitations imposed by plane-wave scintillation in multiconjugate adaptive optics  

NASA Astrophysics Data System (ADS)

Plane-wave scintillation is shown to impose multiconjugate adaptive optics (MCAO) correctability limitations that are independent of wavefront sensing and reconstruction. Residual phase and log-amplitude variances induced by scintillation in weak turbulence are derived using linear (diffraction-based) diffractive MCAO spatial filters or (diffraction-ignorant) geometric MCAO proportional gains as open-loop control parameters. In the case of Kolmogorov turbulence, expressions involving the Rytov variance and/or weighted C2n integrals apply. Differences in performance between diffractive MCAO and geometric MCAO resemble chromatic errors. Optimal corrections based on least squares imply irreducible performance limits that are validated by wave-optic simulations.

Lee, Lawton H.; Baker, Gary J.; Benson, Robert S.

2006-10-01

86

Modulation of radio frequency signals by ULF waves  

Microsoft Academic Search

The ionospheric plasma is continually perturbed by ultra-low frequency (ULF; 1-100 mHz) plasma waves that are incident from the magnetosphere. In this paper we present a combined experimental and modeling study of the variation in radio frequency of signals propagating in the ionosphere due to the interaction of ULF wave energy with the ionospheric plasma. Modeling the interaction shows that

C. L. Waters; T. K. Yeoman; M. D. Sciffer; P. Ponomarenko; D. M. Wright

2007-01-01

87

Digital measurements of LF radio wave absorption in the lower ionosphere and inferred gravity wave activity  

Microsoft Academic Search

Low frequency (LF) radio wave absorption in the lower ionosphere has been measured at Pruhonice (approximately 50 deg N) since 1957. A new digital computer-controlled measuring-recording-processing system was introduced in 1988. The A3 method of radio wave absorption measurement, the measuring equipment used for the digital measurements at 270 kHz, is briefly described. The digital nighttime LF A3 measurements allow

J. Lastovicka; J. Boska; D. Buresova

1993-01-01

88

Short-Wave Radio: An Aid to Language Learning.  

ERIC Educational Resources Information Center

|Discusses use of short-wave radio broadcasts as method for expanding students' appreciation of practical advantages of language learning. Suggests use of news broadcasts and gives guidelines for using broadcasts such as level of aural comprehension in class. (Author/BK)|

Lutcavage, Charles P.

1982-01-01

89

Radio Frequency Probing Apparatus for Surface Acoustic Wave Devices.  

National Technical Information Service (NTIS)

Wafer probing apparatus especially adapted to probing surface acoustic wave (SAW) device die such as delay lines is disclosed: the apparatus includes a probe card especially suited to the radio frequency and multiple output nature of a SAW delay line toge...

F. Y. Cho M. Adamo D. E. Le Son

1984-01-01

90

Radio frequency probing apparatus for surface acoustic wave devices  

NASA Astrophysics Data System (ADS)

Wafer probing apparatus especially adapted to probing surface acoustic wave (SAW) device die such as delay lines is disclosed: the apparatus includes a probe card especially suited to the radio frequency and multiple output nature of a SAW delay line together with a computer-aided electronic system for exciting the delay line and evaluating its output.

Cho, F.; Adamo, M. D.; Leson, D. E.

1984-05-01

91

HUYGEN'S PRINCIPLE APPLIED TO RADIO WAVE PROPAGATION IN ANISOTROPIC MEDIA  

Microsoft Academic Search

Huygens principle describes radio wave propagation in terms of the development of the electromagnetic field from one wavefront to another. This approach finds its mathematical expression in terms of Kirchhoff integrals. For isotropic propagation media, the necessary integrals can be derived from reciprocity relations. In the current paper, it is shown that it is possible to extend the approach to

C. J. Coleman

92

Integrated Measurement of Soil Moisture by Use of Radio Waves.  

National Technical Information Service (NTIS)

An integrated value of soil moisture can be determined by measuring the attenuation of vertically-polarized surface radio waves that are propagated over the ground between a transmitting and receiving antenna. Soil moisture values in the root-zone region ...

D. G. Chadwick

1973-01-01

93

The origin of radio-wave reflections in the troposphere  

Microsoft Academic Search

The evidence relating to the reflection of radio waves in the lower atmosphere is critically examined. It is shown that reflection is most probably due, not to ionized layers as was previously supposed, but to discontinuities in the concentration and state of the water content. It is considered probable that all reflections causing echoes of semi-path less than about 25

J H Piddington

1939-01-01

94

Anomalies in the Absorption of Radio Waves by Atmospheric Gases  

Microsoft Academic Search

This paper summarizes recent measurements of the attenuation of radio waves by atmospheric gases and compares the measured losses with those predicted by Van Vleck. Reasonably good agreement has been noted between the predicted and measured losses for oxygen, but the measured loss for water vapor is considerably in excess of that predicted. Various factors which may influence this discrepancy

A. W. Straiton; C. W. Tolbert

1960-01-01

95

Sodium nightglow and radio wave absorption during winter  

Microsoft Academic Search

A positive correlation is reported between sodium nightglow intensity and radio wave absorption of the previous midday for the period October 1970-March 1971. For the same period a weak correlation, at best, exists for the green line (5577 A) nightglow and absorption. The correlations are briefly discussed and water vapor is suggested as a possible link between the sodium nightglow

M. C. Isherwood

1977-01-01

96

Propagation of Radio Waves in the Lower Troposphere  

Microsoft Academic Search

The effect of tropospheric layers on the propagation of high-frequency radio waves has been experimentally investigated. A theory is proposed which is in agreement with the salient propagation characteristics observed on a nonoptical link. Fields beyond the optical horizon are governed by the layer height and the refractive index change through the layer. For low layers the higher frequencies have

J. B. Smyth; L. G. Trolese

1947-01-01

97

Radio-wave propagation for space communications systems  

Microsoft Academic Search

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,

L. J. Ippolito

1981-01-01

98

Heating the F Region by Deviative Absorption of Radio Waves  

Microsoft Academic Search

The heating and hydrodynamic expansion of the F layer caused by absorption of an incident radio wave occurs in several phases. During the first minute, energy is imparted to the electron gas through ohmic dissipation, the electron temperature is raised, field-aligned pressure gradients are established, and the plasma begins to expand along the magnetic field. Plasma density changes are small,

G. Meltz; R. E. Lelevier

1970-01-01

99

Radio wave propagation along mixed paths in forest environments  

Microsoft Academic Search

The propagation of radio waves is examined for communication paths that may be partly within a forest and partly in regions outside the vegetation. Analytic results are found for simple canonic geometries in which the fields can be described in terms of ray-trajectories. By viewing a realistic forest environment as a combination of such canonic cases, it is possible to

T. Tamir

1977-01-01

100

Radio wave propagation through rain forests of India  

Microsoft Academic Search

A radio wave attenuation measurement survey program was undertaken for the tropical rain forests of India. Measurements were taken at frequencies from 50 to 800 MHz, for antenna heights from 1.5 to 16.5 m above the ground with both horizontally and vertically polarized emissions, and at various separation distances varying from 40 to 4000 m. There were 96 combinations of

R. K. Tewari; S. Swarup; M. N. Roy

1990-01-01

101

Guidance of Radio and Hydromagnetic Waves in the Magnetosphere  

Microsoft Academic Search

The strength and transverse scale of field-aligned irregularities of ionization likely to be required to guide electromagnetic waves through the magnetosphere around the lines of flux of the earth's magnetic field are investigated over the spectrum from hydromag- netic through audio to radio frequencies. For a given flux line there are about five decades of frequency over which guidance is

Henry G. Booker

1962-01-01

102

Radio wave propagation: A comparison between 900 and 1800 MHz  

Microsoft Academic Search

Extensive measurements of radio wave propagation in macro cells were performed. Two transmitters, generating 900 and 1800 MHz, respectively, were situated together. The measurements were performed for six separate transmitter locations in different terrain types. The average value of the signal strength was calculated and stored every 13.3 m over a total distance of 550 km. The difference in path

Lena Melin; Martin Ronnlund; Rickard Angbratt

1993-01-01

103

Radio-Wave Propagation between World Wars I and II  

Microsoft Academic Search

The period between World Wars I and II, 1918 to 1941, is particularly noteworthy for the significant developments that led to a comprehensive understanding of the factors that control the propagation of radio waves through the atmosphere. In slightly over two decades it became possible to identify the basic physical mechanisms with the aid and correlation of theory and experiment,

Stephen Attwood

1962-01-01

104

Ionospheric applications of the scintillation and tomography receiver in space (CITRIS) mission when used with the DORIS radio beacon network  

Microsoft Academic Search

The scintillation and tomography receiver in space (CITRIS) instrument will orbit the Earth near 560 km altitude to detect signals from the ground-based array of more than 50 DORIS UHF\\/S-band radio beacons established at sites around the world by the French Centre National d‘Etudes Spatiales (CNES) and the Institut Géographique National (IGN). The CITRIS receiver is on the US Air Force

Paul A. Bernhardt; Carl L. Siefring; Ivan J. Galysh; Thomas F. Rodilosso; Douglas E. Koch; Thomas L. MacDonald; Matthew R. Wilkens; G. Paul Landis

2006-01-01

105

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

106

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

107

Strong field aligned scattering of UHF radio waves in ionospheric modification  

Microsoft Academic Search

The excitation of super-small-scale (SSS) field aligned plasma density disturbances in ionospheric modification by powerful radio waves is predicted. The SSS disturbances are generated when the frequency of pump radio wave is close to multiple gyroharmonic. The SSS inhomogeneities could to provide a basis for strong scattering of UHF radio waves with frequencies up to 1–3 GHz.

A. V. Gurevich; K. P. Zybin

2006-01-01

108

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

109

Status of RadioWave Neutrino Detection  

NASA Astrophysics Data System (ADS)

As of this writing, there are three dedicated experiments, all based in Antarctica, which seek first-ever measurement of the ultra-high energy neutrino flux at Earth. All three (ANITA, ARA and ARIANNA) exploit the Askaryan Effect to detect the so-called cosmogenic neutrinos which should result from interactions of ultra-high energy baryons with the Cosmic Microwave Background Radiation (CMBR). Photoproduction of those neutrinos, via N? ? ? ? N?+/-, with subsequent weak decays of those pions resulting in neutrinos. In-ice weak and neutral scattering of those neutrinos off ice molecules can yield in a detectable pulse of coherent, radio-frequency radiation. We summarize the three experiments, and discuss prospects.

Besson, Dave

2012-12-01

110

Non-Gaussian Radio-Wave Scattering in the Interstellar Medium  

Microsoft Academic Search

It was recently suggested by Boldyrev & Gwinn that the characteristics of radio scintillations from distant pulsars are best understood if the interstellar electron density fluctuations that cause the time broadening of the radio pulses obey non-Gaussian statistics. In this picture the density fluctuations are inferred to be strong on very small scales (~108-1010 cm). We argue that such density

Stanislav Boldyrev; Arieh Königl

2006-01-01

111

Resonance scattering of radio waves in the acoustically disturbed ionosphere  

SciTech Connect

It is known that acoustic waves are excited in the atmosphere for a variety of reasons, including seismic oscillations of the earth's surface as a result of earthquakes, volcanic eruptions, explosions, and in the operation of other powerful sources of natural or artificial origin. When sound waves are sufficiently intense, they can create disturbances in the electron density at ionospheric heights. In this paper, we consider the properties of radio wave scattering off such disturbances created by infrasound waves, i.e., we consider Mandel'shtam-Brillouin scattering in the ionosphere. The authors discuss the possibility of a radiophysical enhancement of the effect connected with the phenomenon of resonance scattering of the radiowaves off the disturbances created in the medium by the acoustic wave.

Plotkin, V.V.; Izraileva, N.I.

1987-11-01

112

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

113

Twisted Radio Waves and Twisted Thermodynamics  

PubMed Central

We present and analyze a gedanken experiment and show that the assumption that an antenna operating at a single frequency can transmit more than two independent information channels to the far field violates the Second Law of Thermodynamics. Transmission of a large number of channels, each associated with an angular momenta ‘twisted wave’ mode, to the far field in free space is therefore not possible.

Kish, Laszlo B.; Nevels, Robert D.

2013-01-01

114

Transpolar Propagation of Long Radio Waves  

Microsoft Academic Search

This report presents the results of a theoretical analysis and a laboratory simulation of certain transpolar VLF\\/ELF propagation phenomena. The calculations are based on daytime ionospheric models representative of ambient conditions and of conditions that prevail during polar-cap absorption (PCA) events. The laboratory simulation utilized a wave guide that models VLF propagation in the earth-ionosphere cavity. The influence of the

E. C. Field; C. Greifinger; K. Schwartz

1972-01-01

115

Radio wave propagation experiments at the MTRS  

Microsoft Academic Search

Results of analyzing wave propagation data above 10 GHz obtained at the Main Transmit and Receive Station at Kashima since 1978 are presented. Statistics on rainfall rate and rain-induced attenuation of the beacon signal are used to determine that the effective path length was about 5 km with an elevation angle of 37 degrees. The ratio of up-link to down-link

H. Fukuchi; T. Kozu; Y. Takahashi; Y. Otsu; T. Oda

1986-01-01

116

Twisted radio waves and twisted thermodynamics.  

PubMed

We present and analyze a gedanken experiment and show that the assumption that an antenna operating at a single frequency can transmit more than two independent information channels to the far field violates the Second Law of Thermodynamics. Transmission of a large number of channels, each associated with an angular momenta 'twisted wave' mode, to the far field in free space is therefore not possible. PMID:23424647

Kish, Laszlo B; Nevels, Robert D

2013-02-12

117

Waves in Saturn's rings probed by radio occultation  

SciTech Connect

Thirty wave features, observed in 3.6 and 13 cm-wavelength optical depth profiles of Saturn's rings obtained by Voyager 1 radio occultation, are analyzed individually and comparatively. Many are the signature of spiral density waves and bending waves excited by gravitational resonances with Saturn's satellites. A new technique for locating waveform extrema, which fits a sinusoid to each half cycle of wave data, quantifies the wavelength variation across a feature. Fitting dispersion models to the derived wavelengths provides new estimates of ambient surface mass density {sigma} in each wave region. For fourteen weak density waves in Ring A, modelling of the waveform near resonance with linear density wave theory gives independent estimates of {sigma}, as well as reliable estimates of resonance location. Measurements of wave amplitude damping give an upper bound for ring thickness 2H, where H is the ring scale height. In the wave regions studied, Rings A, B, and C have 30 {approx lt} {sigma} {approx lt} 70, {sigma} {approx gt} 65, and {sigma} {approximately} 1 g/cm{sup 2}, respectively. Mass loading estimates from waveform modelling are 20 to 40% larger than dispersion-derived values, suggesting accumulation of mass in the wave regions. The average offset of derived wave location from theoretical resonance is about 1 km. Model waveforms of overlapping waves excited by the satellites Janus and Epimethenus agree well with observed morphologies in the linear region near resonance. In Ring C, dispersion analysis indicates that the most prominent wave feature, previously unidentified, is a one-armed spiral wave.

Rosen, P.A.

1989-01-01

118

Waves in Saturn's rings probed by radio occultation  

NASA Astrophysics Data System (ADS)

Thirty wave features, observed in 3.6 and 13 cm-wavelength optical depth profiles of Saturn's rings obtained by Voyager 1 radio occultation, are analyzed individually and comparatively. A new technique for locating waveform extrema, which fits a sinusoid to each half cycle of wave data, quantifies the wavelength variation across a feature. Fitting dispersion models to the derived wavelengths provides new estimates of ambient surface mass density sigma in each wave region. For 14 weak density waves in Ring A, modelling of the waveform near resonance with linear density wave theory gives independent estimates of sigma, as well as reliable estimates of resonance location. Measurements of wave amplitude damping give an upper bound for ring thickness 2H, where H is the ring scale height. Mass loading estimates from waveform modelling are 20 to 40 percent larger than dispersion-derived values, suggesting accumulation of mass in the wave regions. The average offset of derived wave location from theoretical resonance is about 1 km. In Ring C, dispersion analysis indicates that the most prominent wave feature, previously unidentified, is a one-armed spiral wave at Titan's -1:0 nodal inner vertical resonance, the first wave of this kind identified in nature. Eight other wave features in Ring C remain unexplained. The locations of all identified Ring C resonances stronger than the Mimas 4:1 inner Lindblad resonance (ILR) coincide with gap-ringlet features. If these features are created by the resonances, the required deficit of viscous torque relative to satellite torque limits the ring thickness to 2H less than or approximately equal to 1 m. From wave damping lengths in Ring C, 2H less than or approximately equal to 5 m at least locally.

Rosen, Paul Alan

119

Some problems in modelling water waves for the study of back-scattering of microwave radio energy  

Microsoft Academic Search

Existing information on back-scattering of centimeter radio energy by ocean waves is examined with the thought that back-scattering might be modelled using small water waves and millimeter radio waves. The author concludes that such modeling will be unsuccessful because the scattering of millimeter radio waves will be by capillary water waves rather than gravity waves.

Raymond C. Staley

1958-01-01

120

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

121

Progress in millimeter-wave fiber-radio access networks  

Microsoft Academic Search

\\u000a Abstract  Future radio access networks operating at millimeter-wave frequencies have the capacity to offer broadband interactive services\\u000a to a customer base requiring untethered access. Optical fiber-feed networks incorporating wavelength division multiplexing\\u000a have been proposed as a backbone network providing full-duplex interconnectivity between multiple remote antenna basestations\\u000a and a central office implementing a variety of switching and routing functions. Rapid developments in

A. Nirmalathas; C. Lim; D. Novak; R. B. Waterhouse

2001-01-01

122

Self-focusing of radio waves in an underdense ionosphere  

Microsoft Academic Search

The theory of self-focusing instabilities in the ionosphere is developed emphasizing the critical parameters required to obtain sufficiently fast temporal and spatial growth rates so that the instability may be observed. It is shown that self-focusing will not occur unless 2cf\\/rf\\/sub p\\/²l<1, where f is the radio wave frequency, f\\/sub p\\/ a typical ionospheric plasma frequency, and l the spatial

F. W. Perkins; M. V. Goldman

1981-01-01

123

Electron Transport by Radio Frequency Waves in Tokamak Plasmas  

SciTech Connect

A relativistic kinetic description for momentum and spatial diffusion of electrons by radio frequency (RF) waves and non-axisymmetric magnetic field perturbations in a tokamak is formulated. The Lie perturbation technique is used to obtain a non-singular, time dependent evolution equation for resonant and non-resonant electron diffusion in momentum space and diffusion in configuration space. The kinetic equation for the electron distribution function is different from the usual quasilinear equations as it includes interactions that are non-Markovian. It is suitable for studying wave-particle interaction in present tokamaks and in ITER. A primary goal of RF waves, and, in particular, of electron cyclotron waves, in ITER is to control instabilities like the neoclassical tearing mode (NTM). Non-axisymmetric effects due to NTMs are included in the kinetic formalism.

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

2009-11-26

124

Radio fiber bursts and fast magnetoacoustic wave trains  

NASA Astrophysics Data System (ADS)

Aims: We present a model for dm-fiber bursts that is based on assuming fast sausage magnetoacoustic wave trains that propagate along a dense vertical filament or current sheet. Methods: Eight groups of dm-fiber bursts that were observed during solar flares were selected and analyzed by the wavelet analysis method. To model these fiber bursts we built a semi-empirical model. We also did magnetohydrodynamic simulations of a propagation of the magnetoacoustic wave train in a vertical and gravitationally stratified current sheet. Results: In the wavelet spectra of the fiber bursts computed at different radio frequencies we found the wavelet tadpoles, whose head maxima have the same frequency drift as the drift of fiber bursts. It indicates that the drift of these fiber bursts can be explained by the propagating fast sausage magnetoacoustic wave train. Using new semi-empirical and magnetohydrodynamic models with a simple radio emission model we generated the artificial radio spectra of the fiber bursts, which are similar to the observed ones.

Karlický, M.; Mészárosová, H.; Jelínek, P.

2013-02-01

125

A ring beam mechanism for radio wave emission in the interplanetary medium  

Microsoft Academic Search

Radio wave emission sources in the interplanetary medium (IPM) include type II and type III radio bursts and emission from planetary bow shock regions. The presence of electron beams in a range of energies suggests the possibility of a ring beam-plasma interaction as a mechanism for the generation of radio waves at both the fundamental and the second harmonic of

S. Kainer; R. J. MacDowall

1996-01-01

126

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

127

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

Microsoft Academic Search

Lanthanum bromide (LaBr3:Ce) scintillators offer significantly better resolution (<3 percent at 662keV) relative to sodium iodide (NaI(Tl)) but contain internal radioactivity that contributes to spectral counts. LaBr3: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. LaBr3:Ce

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

2007-01-01

128

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

Microsoft Academic Search

The formation of a volume grating in the near-equator regions of ionosphere due to a high power radio wave is investigated. The radio wave, launched from a ground based transmitter, forms a standing wave pattern below the critical layer, heating the electrons in a space periodic manner. The thermal conduction along the magnetic lines of force inhibits the rise in

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

2011-01-01

129

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

National Technical Information Service (NTIS)

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 ...

J. R. Johler R. L. Lewis

1968-01-01

130

An Overview of Cassini Radio, Plasma Wave, and Langmuir Probe Observations in the Vicinity of Saturn  

Microsoft Academic Search

The Cassini Radio and Plasma Wave Science (RPWS) instrument detected a wide variety of radio and plasma wave phenomena during the approach and first flyby of Saturn. These include Saturn kilometric radiation (SKR), Saturn electrostatic discharges (SEDs), upstream electrostatic waves, the bow shock, trapped continuum radiation, whistler-mode chorus emissions, electrostatic upper-hybrid emissions, impulsive signals from dust impacts, narrowband electromagnetic emissions

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

2004-01-01

131

Cassini radio and plasma wave investigation: Data compression and scientific applications  

Microsoft Academic Search

The Radio and Plasma Wave Science (RPWS) experiment being built for the Cassini spacecraft will study a wide range of plasma and radio wave phenomena in the magnetosphere of Saturn and will also make valuable measurements during the cruise phase and at other encounters. A feature of data from wave receivers is the capability of producing vastly more data than

L. J. C. Woolliscroft; W. M. Farrell; H. St. C. Alleyne; D. A. Gurnett; D. L. Kirchner; W. S. Kurth; J. A. Thompson

1993-01-01

132

Cassini radio and plasma wave investigation - Data compression and scientific applications  

Microsoft Academic Search

The Radio and Plasma Wave Science (RPWS) experiment being built for the Cassini spacecraft will study a wide range of plasma and radio wave phenomena in the magnetosphere of Saturn and will also make valuable measurements during the cruise phase and at other encounters. A feature of data from wave receivers is the capability of producing vastly more data than

L. J. C. Woolliscroft; W. M. Farrell; H. St. C. Alleyne; D. A. Gurnett; D. L. Kirchner; W. S. Kurth; J. A. Thompson

1993-01-01

133

A Forecasting Ionospheric Real-time Scintillation Tool (FIRST)  

Microsoft Academic Search

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

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

2010-01-01

134

Hertz and the Discovery of Radio Waves and the Photoelectric Effect.  

ERIC Educational Resources Information Center

|Describes the discoveries by Hertz historically, such as photoelectric effect, radio waves, their impact on modern physics and some applications. Presents several diagrams and two chronological tables. (YP)|

Spradley, Joseph L.

1988-01-01

135

Radio occultation criterion and detection of internal gravity waves  

NASA Astrophysics Data System (ADS)

A necessary and sufficient criterion is obtained for a layer to be located at the radio occultation (RO) ray perigee. The displacement of an ionospheric or atmospheric layer from the RO ray perigee can be assessed both, qualitatively and quantitatively using this criterion. RO data from the CHAllenge Minisatellite Payload (CHAMP) is used to validate the criterion introduced when significant variations of the amplitude and phase of RO signals are observed at RO ray perigee altitudes below 80 km. The new criterion opens a new avenue in terms of measuring the altitude and slope of the atmospheric and ionospheric layers. This is important for the location and determination of the wind shear and the direction of internal gravity wave (IGW) propagation in the lower ionosphere, and possibly in the atmosphere. The inclination of the wave front can be used to find the angular frequency of GWs. An application of the criterion to the RO data has given the possibility to identify the IGWs in the Earth's stratosphere 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 Earth's stratosphere deduced from the COSMIC and CHAMP GPS occultation temperature profiles are presented and discussed. The work is partly supported by RFBR grant No. 10-02-01015-a.

Pavelyev, A. G.; Gubenko, V.; Liou, Y.-A.; Zhang, K.; Pavelyev, A. A.; Wickert, J.; Kuleshov, Yu.

2012-04-01

136

Upper limits on gravitational wave emission from 78 radio pulsars  

NASA Astrophysics Data System (ADS)

We present upper limits on the gravitational wave emission from 78 radio pulsars based on data from the third and fourth science runs of the LIGO and GEO 600 gravitational wave detectors. The data from both runs have been combined coherently to maximize sensitivity. For the first time, pulsars within binary (or multiple) systems have been included in the search by taking into account the signal modulation due to their orbits. Our upper limits are therefore the first measured for 56 of these pulsars. For the remaining 22, our results improve on previous upper limits by up to a factor of 10. For example, our tightest upper limit on the gravitational strain is 2.6×10-25 for PSR J1603-7202, and the equatorial ellipticity of PSR J2124 3358 is less than 10-6. Furthermore, our strain upper limit for the Crab pulsar is only 2.2 times greater than the fiducial spin-down limit.

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

2007-08-01

137

Searching for Correlated Radio Transients & Gravitational Wave Bursts  

NASA Astrophysics Data System (ADS)

We will discuss an ongoing multi-messenger search for transient radio pulses and gravitational wave bursts. This work is being conducted jointly by the Long Wavelength Array (LWA) and the LIGO Scientific Collaboration (LSC). A variety of astrophysical sources can produce simultaneous emission of gravitational waves and coherent low-frequency electromagnetic radiation. The primary common source motivating this work is the merger of neutron star binaries for which the LWA and LSC instruments have comparable sensitivity. Additional common sources include supernovae, long timescale GRBs and cosmic string cusp events. Data taken by both instruments can be compared to search for correlated signals. Identification of correlated signals can be used to increase the sensitivity of both instruments. We will summarize the coincident observations which have already been conducted and outline plans for future work. We will describe the process being used for synthesizing these data set and present preliminary results.

Kavic, Michael; Shawhan, P. S.; Yancey, C.; Cutchin, S.; Simonetti, J. H.; Bear, B.; Tsai, J.

2013-01-01

138

Focusing of HF radio-waves by ionospheric ducts  

NASA Astrophysics Data System (ADS)

This paper presents the first direct observations of HF focusing induced by natural and artificial ionospheric ducts along with a simple theoretical model. The experiments were conducted by injecting HF radio-waves using the Ionospheric Research Instrument of the High Frequency Active Auroral Research Program located in Gakona, Alaska and detecting them with instruments on the overflying French micro-satellite DEMETER. The latter observed a multiple frequency band structure, which is characteristic of a strong HF signal exceeding the detector's saturation level. Analysis of the O+ density measured by DEMETER along its orbit shows that the strong radio signal coincides with the presence of a “negative” duct in the ionosphere. “Negative” refers to the presence of a plasma density depletion with the peak depletion located near the center of the duct. Such ducts induce changes in the index of refraction leading to the focusing of HF waves in a manner equivalent to a “thick” plasma lens. Examination of the data along with a simple plasma lens model indicates the presence of focal node(s) in the vicinity of the overflying satellite. Two examples, one corresponding to focusing by a natural duct and one by an artificial one are presented.

Milikh, G. M.; Vartanyan, A.; Papadopoulos, K.; Parrot, M.

2011-08-01

139

Variations of the tropospheric propagation range of ultrashort radio waves above the sea  

Microsoft Academic Search

In connection with the development of beyond-the-horizon radar, communications and remote sensing of the atmosphere, the problem of predicting the tropospheric propagation range of ultrashort (US) radio waves has assumed great practical importance. Therefore, the dependence of radio signal characteristics on the propagation conditions has been investigated over different radio paths. Of special interest are routes over oceans, where the

A. R. Gliner; S. N. Krivonozhkin; B. M. Shevtsov

1988-01-01

140

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

141

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

Microsoft Academic Search

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

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

2008-01-01

142

Nonlinear reflection of a high-frequency radio wave by the ionospheric grating created by another wave  

Microsoft Academic Search

A powerful O-mode radio wave of frequency ?0, launched from a ground-based transmitter into the equatorial ionosphere, forms a standing wave pattern below the critical layer, heating the electrons with spatial periodicity. Subsequent ambipolar redistribution of plasma creates a density ripple. When another radio wave, of higher-frequency ?, is launched into the ripple region, the oscillatory electron velocity due to

Ashok Kumar; R. Uma; V. K. Tripathi

2006-01-01

143

The Properties of Plane-wave Scintillation Index Curves for 2D Gaussian and Power Law Random Media  

Microsoft Academic Search

The plane-wave fourth-moment equation is solved numerically for two-dimensional homogeneous random media with Gaussian and power-law fluctuation spectra. Scintillation index curves are calculated for scattering strengths ? spanning the range 0·5 to 10. Multiple peaks in the scintillation index curves are found to occur for moderate values of ? (?10) for power-law media with power indices ? greater than ?2·5.

M. C. Cook

1991-01-01

144

Measurements of Radio Star and Satellite Scintillations at a Subauroral Latitude  

Microsoft Academic Search

Observations of two radio stars, Cygnus A and Cassiopeia A, and of two satellites, Cosmos I and Transit 4A, have yielded data on lower and upper atmospheric irregularities. The frequencies studied have included 20 Mc, 40 Mc and 54 Mc for satellite transmissions, and 30 Mc to 3000 Mc for radio star signals. The antennas used have ranged from a

R. S. Allen; J. Aarons; H. Whitney

1964-01-01

145

Measurements of radio star and satellite scintillations at a subauroral latitude  

Microsoft Academic Search

Observations of two radio stars, Cygnus A and Cassiopeia A, and of two satellites, Cosmos I and Transit 4A, have yielded data on lower and upper atmospheric irregularities. The frequencies studied have included 20 Mc, 40 Mc and 54 Mc for satellite transmissions, and 30 Mc to 3000 Mc for radio star signals. The antennas used have ranged from a

R. S. ALLEN; J. Aarons; H. Whitney

1964-01-01

146

Ionospheric Heating by Radio Waves: Predictions for Arecibo and the Satellite Power Station  

Microsoft Academic Search

The effect of resistive heating by radio waves on ionospheric temperatures, electron densities, and airglow emissions is examined by using numerical ionospheric structure and heat balance codes. Two cases are studied: (1) a 3-GHz, 10-GW microwave beam from a proposed satellite power station and (2) IMW and 3-MW beams of 15-MHz radio waves launched by the Arecibo antenna. By intent,

F. W. Perkins; R. G. Roble

1978-01-01

147

Suprathermal electrons generated by the interaction of powerful radio wave with the ionosphere  

Microsoft Academic Search

We present two sets of observations of suprathermal electrons, produced by the interaction of powerful radio wave with the ionosphere, as seen using the incoherent scatter radar (ISR) technique. The observational data are compared with the theory of multiple acceleration of electrons in the strongly excited resonance region near the reflection point of the powerful radio wave. The structure of

A. V. Gurevich; H. C. Carlson; G. M. Milikh; K. P. Zybin; F. T. Djuth; K. Groves

2000-01-01

148

Stimulated scattering of high-power radio waves in multi-component collisional plasmas  

Microsoft Academic Search

The nonlinear coupling of intense radio waves with the low-frequency electrostatic perturbations of multi-component collisional plasmas is considered. Assuming the presence of two distinct groups of electrons and singly charged ions, we obtain equations for the radio wave sidebands and plasma slow motions that are driven by the combined effects of the radiation pressure and the differential Joule heating of

P. K. Shukla; L. Stenflo

1997-01-01

149

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

150

TH4E: Special Session: Submillimeter Wave Radio Astronomy and Mauna Kea  

Microsoft Academic Search

The historic role that Mauna Kea has played in the development of Radio Astronomy as well as the historic role that radio astronomy has played in the MTT society will be highlighted in this very special focus session on submillimeter wave instrumentation, techniques, and astronomy. A wide range of talks will cover both current topics in millimeter and submillimeter wave

P. Goldsmith; P. H. Siegel

2007-01-01

151

The History of Radio Wave Propagation up to the End of World War I  

Microsoft Academic Search

Hertz in the 1880's demonstrated electromagnetic wave propagation predicted by Maxwell from his equations in 1864. Heaviside and Kennelly postulated the ionosphere to explain Marconi's historical transatlantic reception of radio waves in 1901. Austin derived the first formula for radio propagation in 1911 from experimental data in the kilometer wavelength range taken in the daytime. Much theoretical effort was expended

Charles Burrows

1962-01-01

152

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

153

The Diffraction of Radio Waves in Passing through a Phase-Changing Ionosphere  

Microsoft Academic Search

The radio waves from 'radio stars' may suffer irregular phase changes in passing through the terrestrial ionosphere, so that when they reach the earth's surface they produce a disturbance in which both amplitude and phase vary over the ground. In this paper it is assumed that the wave emerges from the ionosphere with amplitude constant but with phase varying across

A. Hewish

1951-01-01

154

Radio-Holographic Location of Internal Waves in the Ionosphere and Atmosphere  

Microsoft Academic Search

A new radio-holographic method is introduced to locate layers in the propagation medium based on simultaneous observations of radio wave temporal amplitude and phase variations in satellite-to-satellite links The method determines position of a tangent point on the ray trajectory where gradient of refractivity is perpendicular to the ray trajectory and influence of a layered structure on radio wave parameters

A. G. Pavelyev; J. Wickert; Y. A. Liou; A. A. Pavelyev; T. Schmidt; K. Igarashi

2006-01-01

155

Ionospheric Scintillation Effects on GPS Receivers during Solar Minimum and Maximum  

Microsoft Academic Search

The ionosphere has practical importance in GPS (Global Positioning System) applications because it influences transionospheric radio wave propagation. Among various phenomena in the ionosphere, ionospheric scintillation is characterized by rapid fluctuation and fading of the received signal intensity due to electron density irregularity inside the ionosphere. Deep signal fading caused by scintillation can lead to loss of lock of the

Jiwon Seo; Todd Walter; Edward Marks; Tsung-Yu Chiou; Per Enge

2007-01-01

156

A magnetohydrodynamic mechanism for generating radio waves by bright fireballs  

NASA Astrophysics Data System (ADS)

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 only the brightest fireballs exceed the magnetic-Reynolds-number (Rem) threshold for this amplification; a 2-kg, 12-cm-diameter body traveling at 30 km/sec and having a brightness of -12 m is found to have an Rem of 25, the approximate limiting value. The field growth and decay times and the power released by field decay are estimated (for a 2-km/sec object at an altitude of 50 km) as 0.001 sec, 0.002 sec, and 2.5 GW, of which about 2.5 MW are emitted as radio waves and about 2.5 kW are converted to acoustic energy. The latter value is shown to be in general agreement with 'electrophonic-fireball' observations.

Bronshten, V. A.

1983-10-01

157

A Multi-Messenger Search for Radio Transients and Gravitational Waves  

NASA Astrophysics Data System (ADS)

The sensitivity of gravitational waves searches could be improved by coincident observation of electromagnetic signals from expected gravitational wave sources. One possibility is using low-frequency radio transients to trigger and constrain searches for gravitational wave signals. Both are all-sky observations with a number of common sources, and low frequency observations are able to provide spatial and temporal constraints to the search for gravitational wave signals. There is also the added benefit that coincident low-frequency radio and gravitational spectra will allow for more in-depth study of astrophysical events and processes than otherwise possible. In this talk I will layout the case for using low-frequency radio observations to trigger and constrain searches for coincident gravitational wave signals. Common sources and potential ways the joint observation of low-frequency radio and gravitational waves can enhance our understanding of the physics behind these sources will be addressed.

Kavic, Michael; Simonetti, J.; Shawhan, P.; Yancey, C.; Kanner, J.; Cutchin, S.; Ellingson, S.

2012-01-01

158

Radio Wave Fluctuations and Layered Structure of the Upper Region of Venusian Clouds from Radio Occultation Data  

Microsoft Academic Search

The results of the cross-correlation analysis of the amplitude fluctuations of radio waves of the ? = 32 cm band in seven sessions of radio occultation measurements of the northern polar atmosphere of the planet are presented. The existence of the cross-correlation of fluctuations (b? ˜ 0.6) is established in the altitude realizations in the interval 61.5–65.0 km for two

V. N. Gubenko; V. E. Andreev

2003-01-01

159

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

160

Scintillation Detecting and Ranging (scidar/lidar) description of a gravity wave and associated turbulence  

NASA Astrophysics Data System (ADS)

The SCIntillation Detection And Ranging (scidar) optical device was used for remote sensing of atmospheric turbulence from an altitude of 1 km up to 20 to 30 km. The basic principle of this turbulence profiler is the statistical analysis of the speckle pattern produced by the light coming from a double star. It detected a thin sheet structure inside a thick turbulent layer at the tropopause. The periodic occurrence of turbulence in respect to time and altitude was associated with a gravity wave degenerating in turbulence. Its vertical wavelength is found to be 2700 m, and its apparent temporal periodicity 38 min. Two infinity sets of solutions describe the two components of the horizontal wavenumber, and temporal frequency of the gravity wave. Lidar ozone measurements show the same temporal periodicity, with wavelength 21.3 km.

Vernin, J.

1985-08-01

161

Parametric decay of high-frequency radio waves of high intensity in an ionospheric plasma  

Microsoft Academic Search

The parametric instability of ionospheric plasma in a field of intense radio waves in the meter range is discussed. In particular, the decay of high-frequency radio waves into Langmuir and transverse electromagnetic (i.e., stimulated Raman scattering) and into ion-acoustic and electromagnetic waves (i.e., stimulated Brillouin scattering) is considered. A calculation of the threshold fields and increments of perturbation growth number

A. S. Abyzov; A. S. Bakai; G. K. Solodovnikov

1981-01-01

162

Excitation of artificial airglow by high power radio waves from the SURA ionospheric heating facility  

Microsoft Academic Search

The SURA facility for generation of high power radio waves, located near the village of Vasil'sursk USSR, operates between 4.5 and 9.0 MHz and has a maximum effective radiated power (ERP) of 300 MW. Nonlinear interactions between the HF radio waves and F-layer plasma occur near the electromagnetic wave reflection point. Energetic electrons are accelerated out of the interaction regions

P.A. Bernhardt; W. A. Scales; S. M. Grach; A. N. Keroshtin; D. S. Kotik; S. V. Polyakov

1991-01-01

163

Comparison of two phase scintillation estimators for GPS data obtained from High Latitudes.  

NASA Astrophysics Data System (ADS)

Radio waves propagating through small scale plasma density irregularities produce fluctuations in both amplitude and phase of the signal. These fluctuations are called ionospheric scintillations. Due to their spatial diversity, GPS satellites allow scintillation measurement from different azimuthal sectors. Reliability of derived scintillation indices depend on the scintillation estimators used. Here we compare two different estimators for phase scintillations for data obtained from Canadian High Arctic Ionospheric Network (CHAIN) GPS receivers at high latitudes. These stations are specifically chosen to represent polar cap, near to the auroral boundary, and sub-auroral regions . Results of the comparison and its implications will be discussed.

Mushini, S. C.; Thayyil, J. P.; Langley, R. B.; MacDougall, J. W.

2009-05-01

164

The angular dependence and effective point of measurement of a cylindrical scintillation dosimeter with and without a radio-opaque marker for brachytherapy  

NASA Astrophysics Data System (ADS)

Fibre optic scintillation dosimeters, consisting of a plastic scintillator coupled to an optical fibre, are a promising dosimeter in brachytherapy applications. The combination of tissue equivalence, real-time readout and small spatial size makes them especially attractive for in vivo verification of patient treatments. Given that the orientation of the dosimeter with respect to the radioactive source changes during brachytherapy treatment, the angular dependence of the dosimeter is important. We derived the dependence of the response of a cylindrical dosimeter to a point radiation source as a function of distance along its axis and along a radius. Using the results, the effective point of measurement of a cylindrical scintillator was located for two points in the angular response curve as a function of distance between the source and dosimeter. We measured the angular response experimentally for a cylindrical scintillation dosimeter, when the source was located at a distance of 50 mm from the centre of the scintillator. A refinement of the design, in which a radio-opaque marker is incorporated into the tip for accurate localization in the patient, modifies the angular response of the dosimeter. For this new dosimeter design, we show that the dosimeter response decreases by 20% when the source is located on the axis of the scintillator, due to absorption by the marker. The dosimeter response becomes almost angle independent at 10° away from the axis. Excluding this cone, a cylindrical scintillation dosimeter which incorporates a radio-opaque marker was found to be angle independent to within 2%. In most clinical brachytherapy applications, this design has an acceptable angular dependence.

Cartwright, L. E.; Lambert, J.; McKenzie, D. R.; Suchowerska, N.

2009-04-01

165

Measurements of Radio Star and Satellite Scintillations at a Subauroral Latitude.  

National Technical Information Service (NTIS)

Observations of two radio stars, Cygnus A and Cassiopeia A, and of two satellites, Cosmos I and Transit 4A, have yielded data on lower and upper atmospheric irregularities. The frequencies studied have included 20 Mc, 40 Mc and 54 Mc for satellite transmi...

R. S. Allen J. Aarons H. Whitney

1964-01-01

166

A study of VHF radio wave propagation over a water surface of variable conductivity  

Microsoft Academic Search

The ground wave propagation of VHF radio waves over an inhomogeneous sea surface of variable conductivity and under various sea roughness conditions is studied both theoretically and experimentally. Theoretical simulations predict a high sensitivity of the ground wave attenuation factor upon large variations of the surface conductivity, as can be found in an estuary. This sensitivity can be influenced appreciably

P. Forget; P. Broche

1991-01-01

167

Low frequency radio wave propagation in the Atlantic and Mediterranean areas  

Microsoft Academic Search

Data from eighteen long range aircraft flights are compared with the wave hop propagation model of Berry, and areas of agreement and disagreement noted. The field strength of low frequency radio waves from transmitting stations in Iceland, Scotland, Morocco, and Greece was measured under daytime and nighttime conditions. The nighttime waves at about 1 mm seem to oscillate with distance

F. J. Kelly; F. J. Rhoads; D. J. Baker; J. A. Murray

1982-01-01

168

Simulation of Radio Wave Propagation Through the Turbulent ISM  

Microsoft Academic Search

Multiple imaging of pulsars by AU-scale structures results in (low-level) organized patterns in pulsar dynamic spectra and ``scintillation arcs'' in secondary spectra. Detailed new observations of scintillation arcs have been made in the past several years (e. g. Hill et al. 2003 ApJ, 599, 457), showing evidence for scattering from stochastic and deterministic structures in the ionized ISM. Progress requires

M. L. Rudolph; K. A. Allen; T. J. W. Lazio; D. R. Stinebring

2004-01-01

169

Radio wave propagation in structured ionization for satellite and radar applications  

NASA Astrophysics Data System (ADS)

This report is an extension to DNA 5304D and DNA-IR-82-02 which presented the radio propagation algorithms recommended for use by DNA to calculate the properties of scintillated signals. This report covers effects related to antennas and extends the formalism to cover two component power spectra of plasma fluctuations. In addition, an improved representation of the total electron content power spectrum is included to support space radar and similar applications. Appendix E contains SUBROUTINE PROP which implements the radio propagation models.

Wittwer, Leon A.

1993-08-01

170

Collaboration between URSI and CCIR in the study of tropospheric radio wave propagation problems  

Microsoft Academic Search

Topics in tropospheric radio wave propagation addressed by the International Union of Radio Science and the International Radio Consultative Committee include clear-air phenomena, precipitation effects, improvements in centimeter-wavelength space and terrestrial communications, and planning for VHF and UHF services. An example of cochannel interference between earth-space and terrestrial links operating at 4 GHz is presented. In addition, interference by precipitation

J. A. Saxton

1978-01-01

171

Measurements of turbulence in the Venus atmosphere deduced from Pioneer Venus multiprobe radio scintillations  

Microsoft Academic Search

The 2.3-GHz log-amplitude fluctuations observed in the radio links of the Pioneer Venus entry probes during Venus encounter have been used to study turbulence in the Venus atmosphere. The deduced estimates of the upper bound of the structure constant of the refractive index fluctuations (less than approximately 4 x 10 to the -8th\\/cu root cm) are inconsistent with similar entry

R. Woo; J. W. Armstrong; W. B. Kendall

1979-01-01

172

On radio wave scattering in the outer heliosphere  

NASA Astrophysics Data System (ADS)

Recently it has been proposed that scattering by density irregularities causes significant angular broadening of the 2-3 kHz radiation observed by the Voyager spacecraft beyond 10 AU. This proposal is based on analogies with scattered radio emissions within 1 AU, certain characteristics of the 2-3 kHz radiation, and preliminary calculations of angular broadening. This paper describes further angular broadening analyses. Predictions are presented for the scattered source size and the intensity modulation during Voyager rolls, based on the parabolic wave equation formalism and a density spectrum extrapolated from within 1 AU. Comparing the theory with data provides strong evidence that angular scattering dominates the intrinsic source size and produces the large source sizes observed, and that the source is located in the outer heliosphere. Subjects discussed include the level and radial dependence of density turbulence in the outer heliosphere, variations of the apparent source size and modulation index with radial distance and radiation frequency, the onset of modulation for radiation near 2 kHz, the formalism's theoretical limitations, and future research.

Cairns, Iver H.

1996-07-01

173

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

174

Influence of ionospheric irregularities on decameter radio wave propagation: Mathematic modeling  

SciTech Connect

Based on numerical simulation and using the Monte Carlo method, an investigation is carried out of the influence of random irregularities in the ionospheric F-region on short-wave propagation along one-hop radio paths.

Ivanov, V.B.

1995-05-01

175

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

176

Statistical modelling of radio wave propagation under sporadic E-Layer influence  

NASA Astrophysics Data System (ADS)

A technique of modelling the one-hop radio wave propagation at middle latitudes in the presence of sporadic E-Layer is presented. The technique is focused on the performance of the long-term forecast of the maximum usable frequency range and on the increase of the radio communication reliability. Examples of calculation for medium-distance paths are shown.

Sherstyukov, O. N.; Akchurin, A. D.; Ryabchenko, E. Yu.

2009-06-01

177

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

178

Frequency and phase fluctuations of radio waves during propagation in the Venus atmosphere  

Microsoft Academic Search

Radio-occultation data on the Venus atmosphere obtained with the Venera-10 probe are used to analyze the effect of atmospheric irregularities on frequency and phase fluctuations of radio waves at a wavelength of 32 cm; the experiments were carried out in March 1976. It is shown that, as in the case of amplitude fluctuations, when the line of sight is removed

A. I. Efimov; V. M. Razmanov; T. S. Timofeeva; O. I. Iakovlev

1982-01-01

179

Decimeter radio wave propagation in the turbulent plasma near the sun, using Venera 10 spacecraft  

Microsoft Academic Search

The 1976 Venus superior solar conjunction resulted in the occultation of the spacecraft Venera 10 by the sun at solar minimum. At the conjunction time, decimeter radio waves passed through the solar corona. The broadening of the spectrum line, as well as amplitude and frequency fluctuations, was observed over extensive distances of the radio link from the sun. The fluctuation

M. A. Kolosov; O. I. Yakovlev; A. I. Efimov; V. I. Rogal'sky; V. M. Razmanov; V. K. Shtrykov

1982-01-01

180

Radio wave penetration into urban buildings in small cells and microcells  

Microsoft Academic Search

We performed 950 and 1800 MHz CW-measurements of radio wave propagation into various urban buildings in small-cell and microcell propagation scenarios in Vienna. We introduced a new empirical building penetration model that accounted for the power outdoors in a more detailed way than simpler previous ones. In both urban cell types, radio coverage of buildings can successfully be estimated from

Rainer Gahleitner; Emst Bonek

1994-01-01

181

Gravity Wave Analysis with GPS Radio Occultation Data  

Microsoft Academic Search

Atmospheric waves interconnect atmospheric layers. Gravity waves are mesoscale waves with horizontal wavelengths from 10-1000 km and therefore small in comparison to the resolution of climate models. For climate modelling a parametrization of gravity waves is incorporated. Required are global measurements of wave properties. This includes vertical and horizontal wave parameters as well as all possible sources and their temporal

Antonia Haser; Torsten Schmidt; Alejandro de la Torre; Jens Wickert; J. Fischer

2010-01-01

182

Ionospheric heating by radio waves - Predictions for Arecibo and the satellite power station  

Microsoft Academic Search

The effect of resistive heating by radio waves on ionospheric temperatures, electron densities, and airglow emissions is examined by using numerical ionospheric structure and heat balance codes. Two cases are studied: a 3-GHz, 10-GW microwave beam from a proposed satellite power station and 1-MW and 3-MW beams of 15-MHz radio waves launched by the Arecibo antenna. The most dramatic heating

F. W. Perkins; R. G. Roble

1978-01-01

183

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

Microsoft Academic Search

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

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

1989-01-01

184

Attenuation of centimeter radio waves by two H2O phases in the atmosphere of Venus  

Microsoft Academic Search

Using data obtained by Veneras 4 through 6, the integral radio-wave absorption by the uncondensed H2O phase in the Venusian atmosphere is calculated as a function of the impact parameter for the frequency range between 9300 and 21,000 MHz. The height profile of total radio-wave attenuation by uncondensed water vapor and condensed water in the atmosphere is calculated for the

O. F. Tyrnov

1974-01-01

185

Co-Channel Interference Analysis of Point to Point mm-Wave Radio Links  

Microsoft Academic Search

Point to point mm-wave radio links are being increasingly deployed because of the expansion of commercial wireless services. Providers of wireless services continue to demand systems with higher data rate and higher carrier frequency. In order to fulfill the demand unlicensed mm-wave bands have been investigated for fixed point-to-point outdoor radio ap- plications. An analytical method is developed in this

Mingdong Xu; Peter Nuechter

2006-01-01

186

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

187

Nomograms for the calculation of propagation effects on tactical millimeter wave radio links  

Microsoft Academic Search

Description of the development and use of nomograms for calculating propagation effects on tactical millimeter-wave radio links are investigated. The principal causes of attenuation in the millimeter-wave band (35-75 GHz) are oxygen absorption, which depends on radio frequency, and rain scattering, which depends on frequency and rain rate. The nomograms display these dependencies and the range equation, and may be

W. Sollfrey

1979-01-01

188

Prospects of CMOS technology for millimeter-wave radio-over-fiber applications  

Microsoft Academic Search

Millimeter-wave (mm-wave) Radio-over-Fiber (RoF) can be described as mm-wave wireless links in combination with large bandwidth fiber optic interconnections. CMOS technology demonstrated the potential for wireless applications in mm-wave frequencies with advantages of low power consumption, high level of integration capability with other analog and digital circuits, and potentially low cost for mass production. The fundamental principles of RoF technology

Yong Zhang; T. T. Y. Wong

2010-01-01

189

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

SciTech Connect

LaBr3:Ce scintillators offer significantly better resolution (< 3% at 662 keV) relative to NaI(Tl) and have recently become commercially available in sizes large enough for the handheld, Radio-Isotope Identification Device (RIID) market. Drawbacks to lanthanum halide detectors, however, include internal radioactivity contributing to spectral counts, and a low-energy response which can cause detector resolution to be worse 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 1.5² ´ 1.5² LaBr¬3:Ce detector with an Exploranium GR-135 RIID, which contains a 1.5² ´ 2.2² NaI(Tl) detector. Measurements were taken for short timeframes, as typifies RIID usage. Measurements included examples of naturally occurring radioactive material (NORM), typically found in cargo, and special nuclear materials. Some measurements were non-contact, 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).

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

2005-10-23

190

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

SciTech Connect

Lanthanum bromide (LaBr3:Ce) scintillators offer significantly better resolution [<3 percent at 662 kilo-electron volt (keV)] relative to sodium iodide [NaI(Tl)] but contain internal radioactivity that contributes to spectral counts. LaBr3: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 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 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 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 activity due to 138La in the LaBr3:Ce detector exists and NaI(Tl) consistently outperformed LaBr3:Ce.

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

2007-03-11

191

Comparison of LaBr3:Ce and NAI(Tl) scintillators for radio-isotope identification devices  

NASA Astrophysics Data System (ADS)

Lanthanum bromide (LaBr3: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. LaBr3: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. LaBr3: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 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 activity due to 138La in the LaBr3:Ce detector exists and NaI(Tl) consistently outperformed LaBr3:Ce.

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

2007-03-01

192

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

193

Clamping of time scales and collation of frequencies in the frequency range of super-long radio waves  

Microsoft Academic Search

The frequency range of super-long radio waves was historically the first frequency range used for radio communication. Fifty to 55 years ago, almost all of radio (mainly spark transmitters and the corresponding receiving equipment) worked on frequencies below 60 kHz. The theory of propagation of super-long radio waves around the earth reached at that time a rather high development stage

M. V. Bolotnikov; A. D. Klykov

1972-01-01

194

Statistical characteristics of radio waves in a layer with strongly extended random inhomogeneities  

Microsoft Academic Search

We obtain and analyze the transport equation for the frequency correlation function and for other correlation characteristics of radio waves which have passed through a medium with strongly extended random inhomogeneities. It is shown that the correlation characteristics of the waves depend on the parameters S~ and #, where S~ is the average square of the fluctuations of the geometrical

L. M. Erukhimov; P. I. Shpiro

1981-01-01

195

The Influence of the Earth's Magnetic Field on Radio Propagation by WaveGuide Modes  

Microsoft Academic Search

A general theory of radio propagation by wave-guide modes is given, which simultaneously makes allowance for the gradualness of the lowest part of the ionosphere, the earth's curvature and the earth's magnetic field. The method involves solving differential equations satisfied by the matrix admittance or matrix reflexion coefficient variables. The mode condition, excitation factor, and polarization of the waves in

K. G. Budden

1962-01-01

196

Observations of chorus at Saturn using the Cassini Radio and Plasma Wave Science instrument  

Microsoft Academic Search

Observations at Saturn of whistler mode chorus emissions have been obtained by the Cassini Radio and Plasma Wave Science instrument. Data from the first 45 orbits are analyzed, and the characteristics of the chorus emissions are discussed. Wave normal and Poynting vector measurements from the five-channel waveform receiver are used to examine the propagation characteristics of the chorus, and high-resolution

G. B. Hospodarsky; T. F. Averkamp; W. S. Kurth; D. A. Gurnett; J. D. Menietti; O. Santolik; M. K. Dougherty

2008-01-01

197

The absorption and reradiation of radio waves by oxygen and water vapor in the atmosphere  

Microsoft Academic Search

This is a brief review paper on the interaction of radio waves with oxygen and water vapor in the atmosphere. It is the first of a series of mini-reviews sponsored by the Wave Propagation Standards Committee of IEEE and is intended primarily for those persons who have not had occasion to study extensively in the subject.

ARCHIE W. STRAITON

1975-01-01

198

Simplified theory of first- and second-order scattering of HF radio waves from the sea  

Microsoft Academic Search

Since the pioneering work of Crombie [1955], experiments involving backscatter of HF radio waves from sea waves have become an accepted means of remotely mapping the state of the ocean surface [Dexter et al., 1982]. The dominant features of the backscattered frequency power spectrum are two peaks, Doppler shifted with respect to the transmitted signal by amounts consistent with the

R. E. Robson

1984-01-01

199

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

Microsoft Academic Search

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

R. L. Ives; Y. M. Mizuhara; R. V. Schumacher; R. P. Pendleton

1999-01-01

200

On the Reception of Quasi-Monochromatic, Partially Polarized Radio Waves  

Microsoft Academic Search

The response of an elliptically polarized antenna to a quasi-monochromatic, partially polarized radio wave is treated from the standpoint of coherence theory. A general formula is derived for the available power at the terminals of a receiving antenna in terms of appropriately chosen coherency matrices for the antenna and the incident wave. It is shown that the result is formally

H. C. Ko

1962-01-01

201

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.

202

The CERTO and CITRIS Instruments for Radio Scintillation and Electron Density Tomography from the C/NOFS, COSMIC, NPSAT1 and STPSAT1 Satellites  

NASA Astrophysics Data System (ADS)

A new constellation of radio beacon and radio beacon receivers will be providing global measurements of radio scintillations and total electron content (TEC) for near real time measurements of the ionosphere. This constellation is comprised of the NRL Coherent Electromagnetic Radio Tomography (CERTO) beacons on the Communications/Navigation Forecast Outage System (C/NOFS) satellite, the six Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) satellites, and the Naval Postgraduate (NPSAT1) Satellite. These satellites will be launched in the time period of 2004 through 2006. The CERTO beacons operating at 150.012, 400.032, and 1066.752 MHz will be transmitting to ground receivers located in chains to acquire TEC data for computerized ionospheric tomography (CIT). In addition, in early 2006 a five frequency receiver will be placed in low earth orbit with the United States Air Force Space Test Program (STPSAT1) satellite. This CITRIS receiver will use radio beacon transmissions from the French DORIS network of ground beacons at 401.25 and 2036.25 MHz and space-based beacons at 150, 400 and 1067 MHz to measure the earth's ionosphere. On board tracking software will lock onto Doppler shifted frequencies to determine total electron content (TEC) and scintillation parameters. The STPSAT1 will be launched along with a companion satellite (NPSAT1) which carries the CERTO radio beacon and a Langmuir probe. All of the CERTO beacons as well as the ionospheric sensors on STPSAT1 and NPSAT1 are being constructed at the Naval Research Laboratory. The data obtained using the CITRIS instrument will provide a global description of the ionosphere from orbits with inclinations ranging from 15 degrees to 70 degrees and altitudes from 375 to 800 km. The tandem operations of the CITRIS and CERTO instruments will provide the fully low-earth-orbit based occultation measurements of the ionosphere. All of the data will be available for rapid assimilation ionospheric, space-weather models.

Bernhardt, P. A.; Siefring, C. L.

2004-05-01

203

Ionospheric modification by chemical releases and high-power radio waves  

SciTech Connect

Ionospheric plasma density irregularities can be produced locally by chemical releases from space vehicles or remotely by a beam of high power radio waves transmitted from the ground. F-region plasma modification occurs by (1) chemically enhancing the electron number density, (2) chemically reducing the electron population, or (3) physically convecting the plasma from one region to another. The three processes (production, loss, and transport) can determine the effectiveness of ionospheric chemical releases and high frequency electromagnetic wave transmissions in subtle and surprising ways. Initially, a chemical release produces a localized change in plasma density and high power radio waves heat the electrons to yield enhanced transport from pressure gradients in the heated region. Subsequent processes, however, can lead to enhanced transport in chemically modified regions and modified reaction rates in the regions affected by high power radio waves.

Bernhardt, P.A.; Scales, W.A.; Keskinen, M.J.; Duncan, L.M.; Rowland, H.L.

1990-05-03

204

Centimeter-wave Research with the Morehead State University 21 M Radio Telescope: Involving Undergraduate Students in Radio Astronomy Research  

NASA Astrophysics Data System (ADS)

The Space Science Center at Morehead State University has developed a medium aperture cm-wave radio telescope, the 21 M Space Tracking Antenna and Radio Telescope. Located in the radio-frequency quiet, mountainous region of eastern Kentucky, the telescope serves as an Earth Station for satellite mission support and provides telemetry, tracking, and control services with an emphasis on university cubesat missions. In addition, the telescope is engaged in research programs in radio astronomy and features receivers operating in the Ku-band (11.2 to 12.7 GHz, including a well-known methanol line) and the L-band (1.4 to 1.7 GHz, including lines of atomic hydrogen and molecular hydroxyl). At these bands, the telescope is capable of supporting a wide variety of niche astronomical research programs, including longitudinal studies (e.g., active galactic nuclei (AGN) monitoring), observations of transient phenomena (e.g., gamma-ray bursts and supernovae), and surveys (e.g., kinematic studies of Galactic HI). A description of the space tracking antenna system and radio telescope, its capabilities and research projects planned for or currently underway with the telescope (namely monitoring AGNs and surveying the Galactic supernova remnant population) will be presented and discussed. Funding for the 21m telescope has been provided by NASA, the SBA, the Kentucky Science and Engineering Foundation and Kentucky NSF EPSCoR.

Malphrus, Benjamin K.; Pannuti, T. G.; Atwood, J. W.; Ennis, M. E.

2007-12-01

205

Three-dimensional Langmuir wave instabilities in type III solar radio bursts  

Microsoft Academic Search

Assuming that type III solar radio bursts are associated with electron streams moving at about c\\/3, Langmuir waves should be strongly excited. A study is made of the Langmuir-wave linear parametric instabilities excited in cylindrical symmetry by an electron-stream-driven Langmuir wave-pump propagating along the stream axis. Included in this unified homogeneous treatment are induced backscattering off ions, the oscillating two-stream

S. Bardwell; M. V. Goldman

1976-01-01

206

Study of long-wave radio signal disturbances due to lightning-induced energetic electron precipitation  

Microsoft Academic Search

Observing long-wave radio signals at short distances simultaneously with the broadband reception of VLF radiations, we obtained\\u000a an abrupt (by more than 10%) amplitude variation of signals from the Moscow long-wave transmitter which can be identified\\u000a as the reflection of long-wave signals from lightning-induced energetic electron precipitation regions in the ionosphere.\\u000a Some amplitude variation events were accompanied by single-hop whistlers

P. P. Savchenko

1997-01-01

207

Investigation of Stimulated Brillouin Scattering for the Generation of Millimeter Waves for Radio over Fiber System  

Microsoft Academic Search

Radio over fiber (RoF) is a promising technique in providing broadband wireless access services in the emerging optical-wireless networks. Optical millimeter-wave (mm-wave) generation is a key technique to realize low cost and high transmission performance in the RoF systems. Several techniques have been proposed for the optical generation of mm-waves such as direct modulation, external modulation, optical heterodyning and so

N. M. Nawawi; S. M. Idrus

2008-01-01

208

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

Microsoft Academic Search

The architecture of fiber-radio mm-wave wireless access systems critically depends upon the optical mm-wave generation and transport techniques. Four optical mm-wave generation and transport techniques: 1) optical self-heterodyning, 2) external modulation, 3) up- and downconversion, and 4) optical transceiver, will be assessed. From the technical viewpoints, their advantages and disadvantages are discussed. The economical assessment, focusing on the cost of

Ken-Ichi Kitayama

2000-01-01

209

Polarization effects in radio wave scattering from meteor bursts  

Microsoft Academic Search

Using polarimetric radio echoes measured from meteor trails in the 1950s, the authors analyze the time-dependent scattering contributions from the specular as well as the plasma resonance effects in the radar-target scattering matrix representation. It is found that the radio echoes from underdense meteor bursts are stronger in the transverse direction than in the longitudinal during the first half of

P. S. P. Wei; C. R. Miller; C. K. Martin

1989-01-01

210

Polarization effects in radio wave scattering from meteor bursts  

Microsoft Academic Search

Using polarimetric radio echoes measured from meteor trails in the 1950s, the authors analyze the time-dependent scattering contributions from the specular as well as the plasma resonance effects in the radar-target scattering matrix representation. It is found that the radio echoes from the underdense meteor bursts are stronger in the transverse direction than in the longitudinal during the first half

P. S. P. Wei; C. R. Miller; C. K. Martin

1989-01-01

211

Millimeter-wave fiber optics systems for personal radio communication  

Microsoft Academic Search

System concepts for millimeter-wave personal communication systems and the advantages of millimeter-wave band usage are briefly described. Demonstration of broadband millimeter-wave subcarrier transmission concepts over fiber-optic links is performed. Several fiber-optic link architectures, including one using a combination of direct laser modulation and indirect (external) optical modulation, are outlined with respect to signal transmission at millimeter-wave frequencies. Several configurations are

Hiroyo Ogawa; David Polifko; Seiichi Banba

1992-01-01

212

Clumpy Langmuir waves in type III radio sources  

Microsoft Academic Search

A model is developed for the clumpy Langmuir waves observed in type III source regions. In this model the waves are generated by instability of a beam which propagates outward from the Sun in a state close to marginal stability. Ambient density perturbations cause fluctuations about the marginally stable state, leading to nonuniformities in both beam and waves and, hence,

P. A. Robinson

1992-01-01

213

Prolonged millimeter-wave radio emission from a solar flare near the limb  

Microsoft Academic Search

We present a multi-wavelength analysis of a gradual radio flare on June 27, 1993 which showed emission at millimeter waves long after the soft X-ray flux had peaked. The radio flare located at S12 E75 was associated with a GOES class M3.6 flare that lasted for more than one hour and hard X-ray emission during the rising phase of the

S. Pohjolainen; J. Hildebrandt; M. Karlický; A. Magun; I. M. Chertok

2002-01-01

214

Variations of radio-wave propagation conditions in the corona during a solar activity cycle  

Microsoft Academic Search

Variations of the propagation conditions of monochromatic radio waves through the solar corona during an 11-year cycle are analyzed on the basis of space-probe (Pioneer, Mariner, Mars, Venera, Helios, Viking, and Voyager) data. It is shown that, besides short-term variations of radio-signal parameters with a characteristic time of 5-20 days, there occur long-term variations of propagation conditions with periods of

A. I. Efimov; O. I. Iakovlev; V. K. Shtrykov; V. I. Rogalskii

1984-01-01

215

Transmission Performance of mm-Waves on Radio over Fiber Systems: Dispersion and Intermodulation Issues  

NASA Astrophysics Data System (ADS)

Next generation wireless networks must provide high broadband access, which can be achieved by combining the fiber optics and wireless technologies. In this paper we analyze a mm-wave radio over fiber (RoF) optical access network architecture, combining radio subcarrier multiplexing techniques to improve system efficiency with fiber dispersion mitigation provided by optical single sideband modulation techniques. Our results show the system degradation introduced by the fiber link, namely fiber dispersion and intermodulation effects.

Avó, Ricardo; Laurêncio, Paula; Madeiros, Maria C. R.

216

Transmission Performance of mm-Waves on Radio over Fiber Systems: Dispersion and Intermodulation Issues  

Microsoft Academic Search

\\u000a Next generation wireless networks must provide high broadband access, which can be achieved by combining the fiber optics\\u000a and wireless technologies. In this paper we analyze a mm-wave radio over fiber (RoF) optical access network architecture,\\u000a combining radio subcarrier multiplexing techniques to improve system efficiency with fiber dispersion mitigation provided\\u000a by optical single sideband modulation techniques. Our results show the

Ricardo Avó; Paula Laurêncio; Maria C. R. Madeiros

2010-01-01

217

Short-baseline neutrino oscillation waves in ultra-large liquid scintillator detectors  

NASA Astrophysics Data System (ADS)

Powerful new multi-kiloton liquid scintillator neutrino detectors, including NO?A and, possibly, LENA, will come on-line within the next decade. When coupled with a modest-power decay-at-rest (DAR) neutrino source at short-baseline, these detectors can decisively address signals for neutrino oscillations at high ?m2. Along the greater than 50 m length of the detector, the characteristic oscillation wave will be apparent, providing powerful verification of the oscillation phenomenon. LENA can simultaneously perform ?? ? ?e appearance and ?e ? ?e disappearance searches while NO?A is likely limited to ?e disappearance. For the appearance channel, a LENA-like detector could test the LSND and MiniBooNE signal regions at >5 ? with a fiducial volume of 5 kt and a 10 kW neutrino source. The LENA and NO?A ?e disappearance sensitivities are complementary to the recent reactor anomaly indicating possible ?e disappearance and would cover this possible oscillation signal at ~3 ?.

Agarwalla, Sanjib Kumar; Conrad, J. M.; Shaevitz, M. H.

2011-12-01

218

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

219

Spatial and temporal distribution of the VHF\\/UHF radio waves in built-up land communication links  

Microsoft Academic Search

We present a unified approach of the description of the spatial and temporal distribution of radio signals within built-up radio communication links. This approach is based on a multiparametric stochastic model, which takes into account the characteristic features of built-up terrain and peculiarities of radio wave propagation related with multiple reflections, diffraction and scattering phenomena caused by obstructions surrounding both

Nathan Blaunstein; Nathalie Yarkoni; Dmitry Katz

2006-01-01

220

The evolution of scattering equatorial F-region irregularities and resultant effects on trans-ionospheric radio waves  

Microsoft Academic Search

Results from a series of ground and airborne experiments are presented which describe spatial and temporal characteristics of equatorial F-region irregularities and the effect of these irregularities on transionospheric radio propagation. The experiments included UHF amplitude scintillation measurements from the WIDEBAND, MARISAT, and LES-9 satellites, and simultaneous ionospheric measurements from the AFGL Airborne Ionospheric Observatory and the Jicamarca Radar Observatory

H. E. Whitney; J. Aarons; J. Buchau; E. J. Weber; J. P. McClure

1978-01-01

221

Propagation of VHF Radio Waves on Sea Routes in the South Polar Latitudes  

NASA Astrophysics Data System (ADS)

We present the results of meteorological and radiometeorological observations as well as the results of measurements of the attenuation factor of very-high-frequency (VHF) radio waves during the 28th Soviet Antarctic expedition in January March 1983. It is shown that radiometeorological parameters over the South ocean area in summer almost coincide with the corresponding averaged parameters over the land in winter. The main mechanism of radio-wave propagation at distances over 100 km is single scattering by turbulent fluctuations of the atmospheric refractive index. Absolute values of the running attenuation at high frequencies are low compared to those in other climatic areas.

Ivanov, V. K.; Lanovoy, V. N.; Shalyapin, V. N.; Egorova, L. A.; Vasil'Yev, A. S.; Mogila, A. A.

2005-07-01

222

Radio wave propagation in a multiscale inhomogeneous ionosphere  

Microsoft Academic Search

Results of an experimental study of the structure of a multiscale inhomogeneous ionosphere and statistical characteristics of signal propagation are reported. A theory is developed for the propagation of radio signals of arbitrary power and polarization in an ionosphere containing multiscale inhomogeneities. The mechanisms responsible for the formation of nonlinearities in an inhomogeneous ionosphere under the effect of oblique-incidence high-intensity

Gennadii K. Solodovnikov; Viktor I. Novozhilov; Mars N. Fatkullin

1990-01-01

223

Digital Radio Link: Wave Propagation Measurements Using Narrow Band Technique.  

National Technical Information Service (NTIS)

Measurements on a 34 M Bit, 7 GHz digital radio link with a linkhop of 56 km are described. Events with flat and frequency selective fading are presented and a method using narrow band measurements to evaluate frequency selective fading is outlined. By ma...

S. Nilsson L. Ladell

1984-01-01

224

SCINTILLATION SPECTROMETER  

DOEpatents

A portable scintillation spectrometer is described which is especially useful in radio-biological studies for determining the uptake and distribution of gamma -emitting substances in tissue. The spectrometer includes a collimator having a plurality of apertures that are hexagonal in cross section. Two crystals are provided: one is activated to respond to incident rays from the collimator; the other is not activated and shields the first from external radiation.

Bell, P.R.; Francis, J.E.

1960-06-21

225

Excitation of artificial airglow by high power radio waves from the SURA ionospheric heating facility  

SciTech Connect

The SURA facility for generation of high power radio waves, located near the village of Vasil'sursk USSR, operates between 4.5 and 9.0 MHz and has a maximum effective radiated power (ERP) of 300 MW. Nonlinear interactions between the HF radio waves and F-layer plasma occur near the electromagnetic wave reflection point. Energetic electrons are accelerated out of the interaction regions by the electrostatic waves. Ambient oxygen atoms collisionally excited by these suprathermal electrons yield enhanced airglow. Low-light-level, optical measurements were made at SURA during September 1990. Images of enhanced red-line (630 nm) emissions were recorded during radio wave transmissions at 4.786, 5.455, and 5.828 MHz. The antenna radiation pattern, ionospheric irregularities, and the magnetic field orientation affected the shape of the observed airglow structures. The airglow clouds drifted across the night sky, disappeared, and reformed at the zenith of the antenna array. This has been interpreted in terms of radio beam refraction in drifting plasma irregularities and bifurcation when the beam is split between two density cavities. Subject to clear skies, the authors experience indicates that the low-light-level-imaging technique is a reliable method to study large scale irregularities and electron acceleration with high-power HF transmitting facilities.

Bernhardt, P.A.; Scales, W.A. (Naval Research Lab., Washington, DC (United States)); Grach, S.M.; Keroshtin, A.N.; Kotik, D.S.; Polyakov, S.V. (Radiophysical Research Inst., Novgorod (USSR))

1991-08-01

226

The Diffraction of Galactic Radio Waves as a Method of Investigating the Irregular Structure of the Ionosphere  

Microsoft Academic Search

The amplitudes of the radio waves received from a radio star at two points separated by about 1 km have been studied and compared. The results indicate that the variations of phase and amplitude at one point can be ascribed to the steady drift of an irregular wave-pattern over the ground. It is shown how the structure and movement of

A. Hewish

1952-01-01

227

Passage of a powerful HF radio wave through the lower ionosphere as a function of initial electron density profiles  

Microsoft Academic Search

The results of numerical modelling of powerful HF radio wave propagation through the ionosphere plasma are presented. Comparison of the heating wave parameters with those of a low powerwave gives the possibility to study the self-action of the powerful HF wave. At low altitudes the ‘translucence’ of the ionosphere plasma takes place. At high altitudes the wave absorption sharply increases.

E. G. Belova; A. B. Pashin; W. B. Lyatsky

1995-01-01

228

Resonant scattering of radio waves in the high-latitude lower ionosphere  

Microsoft Academic Search

A resonant-scattering investigation was carried out in the nighttime high-latitude lower ionosphere during February-March 1978 in the Monchegorsk region. Ionospheric plasma was artificially disturbed by a transmitter continuously emitting linear polarized radio waves at a frequency of 3.3 MHz and an effective power of about 10 MW. Two standing waves were produced in the ionosphere as a result of magnetoionic

V. K. Galaidych; S. I. Maretynenko; V. A. Misiura; L. A. Piven; I. A. Sergienko; V. G. Somov; L. F. Chernogor

1985-01-01

229

Rain induced attenuation of millimeter waves radio link in Indian continent  

Microsoft Academic Search

The performance and reliability of millimeter wave radio link is degraded mainly by rain. In the present paper the aspect\\u000a of rain induced attenuation with respect to raindrop is described. How the microstructure details of rain are necessary for\\u000a estimating the rain induced attenuation in millimeter wave region are explained on the basis of the rain data for different\\u000a stations

Saxena Poonam; T. K. Bandopadhyaya

1997-01-01

230

Building Penetration and Shadowing Characteristics of 1865 MHz Radio Waves  

Microsoft Academic Search

An in-building measurement campaign was conducted to characterize building properties pertaining to radio frequency propagation\\u000a and losses for personal communication system (PCS) applications. Measurements were made in and around seven buildings in urban\\u000a environments in three cities in The Netherlands. The mean building shadowing loss for all buildings, measured on the groundfloor,\\u000a was found to be 12.4 dB with a

Manish Panjwani; Gary Hawkins

231

An equatorial scintillation model  

Microsoft Academic Search

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

E. J. Fremouw; R. E. Robins

1985-01-01

232

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

NASA Astrophysics Data System (ADS)

A new approach for obtaining integrated estimates of soil moisture content over larger regions of typically 10-50 km is described. It is based on a known correlation between propagation characteristics of low frequency radio surface waves and surface soil moisture, and provides valuable new benefits especially for meteorological prognostic models and for soil water estimation in agriculture. The paper consists of (1) a description of the theory of radio wave propagation with an extension of the classical theory of Norton (Proceedings of the Institute of Radio Engineers, Vol. 24, 1936), specifically the exploitation of the phase information, (2) demonstration of a method which guarantees the selection of reliable results from a large measurement data set, (3) a presentation of a new low cost measurement device to detect the amplitude and phase changes, and (4) results from initial measurements providing evidence that theoretical calculations are consistent with the measured change of electromagnetic signal properties due to soil moisture change.

Huebner, Christof; Kottmeier, Christoph; Brandelik, Alexander

2011-06-01

233

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

2004-12-16

234

An FFT-based Kirchhoff integral technique for the simulation of radio waves in complex environments  

Microsoft Academic Search

Kirchhoff integral (KI) techniques provide an effective means of simulating radio wave propagation in nonhomogeneous media with complex boundaries. In particular, these techniques can handle quite general boundary topography. Due to the translation-dependent nature of their kernels, however, they cannot take advantage of the fast Fourier transform (FFT) techniques that give the parabolic equation methods their speed. In this paper

Christopher John Coleman

2010-01-01

235

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

236

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

237

Propagation of VHF Radio Waves on Sea Routes in the South Polar Latitudes  

Microsoft Academic Search

We present the results of meteorological and radiometeorological observations as well as the results of measurements of the attenuation factor of very-high-frequency (VHF) radio waves during the 28th Soviet Antarctic expedition in January March 1983. It is shown that radiometeorological parameters over the South ocean area in summer almost coincide with the corresponding averaged parameters over the land in winter.

V. K. Ivanov; V. N. Lanovoy; V. N. Shalyapin; L. A. Egorova; A. S. Vasil'Yev; A. A. Mogila

2005-01-01

238

Scattering of radio waves from the mesosphere. I - Theory and observations  

Microsoft Academic Search

Scattering of radio waves at VHF and UHF frequencies from thermal and nonthermal fluctuations in the mesosphere is considered. The formulation of scattering from a statistically homogeneous and stationary medium is described and extended to the case of a locally homogeneous and locally stationary medium to show that the scattering is affected by fluctuations in the vicinity of the Bragg

P. K. Rastogi; S. A. Bowhill

1976-01-01

239

A Hybrid Model for Radio Wave Propagation Through Frequency Selective Structures (FSS)  

Microsoft Academic Search

A novel hybrid model is presented to study the radio wave propagation through frequency selective structures (FSS) used to control propagation in an outdoor to indoor building environment. This hybrid model is based on combining ray-tracing with a commercial tool, Computer Simulation Technology (CST) Microwave Studio. Numerical results of the hybrid model have been compared with those of a full

Ming Yang; Anthony K. Brown

2010-01-01

240

Factors Influencing Radio Wave Transmission and Reception: Use of Radiotelemetry in Large River Systems  

Microsoft Academic Search

Many technical and environmental variables affect radio wave transmission and reception in aquatic environments. We used a controlled experimental design in three large North American rivers (Illinois and Mississippi rivers, Illinois, and Skeena River, British Columbia) to examine the effects of water conductivity, transmitter depth, electromagnetic noise, antenna height, and transmitter type on detection distance. Detection distance was significantly affected

Lindsay M. Peters; Ulrich G. Reinhardt; Mark A. Pegg

2008-01-01

241

The Relation of Radio SkyWave Transmission to Ionosphere Measurements  

Microsoft Academic Search

A simple, rapid, graphical method is given for obtaining maximum usable frequencies and effective reflection heights of radio waves, from vertical-incidence measurements of the critical frequencies and virtual heights of the various layers in the ionosphere. The method consists of the use of \\

N. Smith

1939-01-01

242

Observational Constraints on Gravitational Wave Recoil Kick Velocities in Supermassive Black Hole Binaries from Radio Galaxies  

Microsoft Academic Search

In recent years, general relativity simulations of binary black hole mergers have demonstrated that large `kicks' due to gravitational wave radiation recoil are possible. An observable manifestation of this phenomena would be a displacement of the resultant active nucleus from its parent host galaxy. We test this interesting possibility with measurements of a large sample of radio galaxies, focusing in

Teddy Cheung

2009-01-01

243

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

244

A simple demonstration for exploring the radio waves generated by a mobile phone  

NASA Astrophysics Data System (ADS)

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.

Hare, Jonathan

2010-09-01

245

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

246

Radio-wave reflections from a spherical Earth. Predictions at VHF and UHF  

Microsoft Academic Search

The field strength of radio waves at VHF and UHF is affected by reflections from the ground or water. Except for the shortest paths, the reflecting surface must be considered to be spherical rather than flat. Computer programs for automatically finding the reflection point, for calculating the effective coefficient of reflection, and for estimating the effect of any obstructions in

J. H. Whitteker

1982-01-01

247

The Scattering of Radio Waves in the Lower and Middle Atmosphere  

Microsoft Academic Search

The evidence relating to the reflection of radio waves from levels below 80 kilometers is considered and apparatus used to investigate the reflection coefficients of these regions is described. The new experimental results here presented are not in agreement with those of earlier workers, but indicate that reflections from region B (below 10 kilometers) and region C (35 to 60

J. H. Piddington

1939-01-01

248

EFFECTS OF RADIO FREQUENCY WAVES ON FUNGAL COLONIZATION OF STYROBLOCK CONTAINERS  

Microsoft Academic Search

Fungal pathogens tend to accumulate within styroblock containers, which are reused to produce successive crops of container-grown seedlings. Most nurseries treat reused containers by immersing them in hot water for varying time periods. The efficacy of radio frequency waves (RFs) to reduce levels of selected groups of fungi within styroblock containers was evaluated. RFs were effective only on containers that

R. L. James; Andy Trent

249

Measurement of atmospheric water vapour on the ground's surface by radio waves  

Microsoft Academic Search

Water vapour in the atmosphere and various meteorological phenomena are essential to the understanding of the mechanism of the water cycle. However, it is very difficult to observe water vapour in the atmosphere because the quantities are usually observed at a single point not over long intervals or in a specific plane or volume. Accordingly, the use of radio waves

Tokuo Kishii; Yasuhisa Kuzuha; Fumi Sugita; Michiko Hayano

2001-01-01

250

Characterization of the Indoor Channel by an Optimised Simulation of the Radio Wave Propagation  

Microsoft Academic Search

This paper is based on a 3D simulation software of radio waves propagation (1)for wireless systems in indoor environments. This software (figure 1), developed in the IRCOM-SIC lab- oratory (University of Poitiers, France), allows to predict the coverage zone of a base station and the behaviour of the wide band propagation channel. Firstly, after a brief recall of our propagation

Rudolf Vauzelle; F. Escarieu

251

Measurements of the propagation of UHF radio waves on an underground railway train  

Microsoft Academic Search

Measurements of the natural propagation of UHF radio waves on an underground train are reported. Of prime interest are the natural propagation attenuation and the median signal level behavior. The propagation attenuation rates or the median signal level behaviors are found to correlate with the train carriages and frequency. On the front carriage, the propagation attenuation rate is 54 dB\\/100

Y. P. Zhang; Z. R. Jiang; T. S. Ng; J. H. Sheng

2000-01-01

252

Characteristics of radio wave for the indoor wireless communication in Malaysian typical office environment  

Microsoft Academic Search

It is well known that the propagation characteristics are changed for wireless communication. We have investigated the characteristics of radio wave for indoor wireless communication in a typical Malaysian office environment. It is not too far when a lot of Malaysian people will use their personal computer or lab top in the office for signal transmission through an indoor wireless

M. Shahidul Islami; T. A. Rahman

2003-01-01

253

Analysis of radio wave propagation from an indoor hall to a corridor  

Microsoft Academic Search

In this paper the radio wave propagation from an indoor hall to a corridor was studied by analyzing the results from a multi-link MIMO channel sounding measurement. The results showed that despite NLOS conditions, the dominant propagation mechanisms comprised direct path through the wall and specular reflections. These findings were verified by plotting the dominant pathways with a measurement-based ray

Juho Poutanen; Katsuyuki Haneda; Jussi Salmi; Veli-Matti Kolmonen; J. Koivunen; P. Almers; P. Vainikainen

2009-01-01

254

Prediction of mobile radio wave propagation over buildings of irregular heights and spacings  

Microsoft Academic Search

Two models of mobile radio wave propagation over buildings are presented. The first, the flat edge model, provides a simple yet accurate representation when buildings are assumed to be of constant height and spacing. The second model combines the first with a rapid new method of calculating multiple edge diffraction to allow deterministic predictions with arbitrary buildings and spacings. This

S. R. Saunders; F. R. Bonar

1994-01-01

255

Radio wave scattering from the tropical mesosphere observed with the Jicamarca radar  

Microsoft Academic Search

The paper reports on radio wave scattering from the tropical mesosphere which was observed on November 14-16, 1977, using the VHF radar at Jicamarca. It is shown that strong aspect sensitive scattering that is accompanied by a marked positive correlation between the temporal variation of the echo power and the signal correlation time is observed below about 75 km as

S. Fukao; T. Sato; S. Kato

1980-01-01

256

A model for the tropospheric excess path length of radio waves from surface meteorological measurements  

Microsoft Academic Search

Two models are given for predicting of the excess path length of radio waves from ground-based measurements of pressure, temperature, and humidity, at zenith and at a given apparent elevation angle. The models use the same formulation for the hydrostatic component of the excess path, but use different methods for the wet component. For the hydrostatic component, the models provide

H. Berrada Baby; P. Gole; J. Lavergnat

1988-01-01

257

Measurements of rain drop size distributions and estimation of radio-wave attenuation coefficients  

NASA Astrophysics Data System (ADS)

Results of photoelectron-detector measurements of rain drop size distributions carried out near Dubna, USSR during May-September, 1987 are presented. It is shown that, for large and small drop diameters, these distributions differ from the Marshall-Palmer ones. Radio-wave attenuation coefficients are evaluated for such distributions.

Zakharian, M. V.; Kornilov, L. N.; Pozhidaev, V. N.

1989-10-01

258

Type III Radio Bursts at Long Wavelengths: Statistics from STEREO/Waves 2007-2010  

NASA Astrophysics Data System (ADS)

During increased solar activity type III radio bursts are frequently observed by the S/Waves instrument on-board both STEREO spacecraft. These radio bursts are generated by a non-linear conversion of the Langmuir waves which have been excited by beams of fast electrons connected with solar flares and/or CME driven shocks. The High Frequency Receiver (HFR; a part of S/Waves) records fluctuations of the electric field from 125 kHz up to 1975 kHz with goniopolarimetric (GP) capabilities that allows us to perform propagation analysis of an incident wave. We present extensive statistics of more than 100 intense events observed between March 2007 and July 2010. We have found that type III radio bursts generally propagate in the solar equatorial plane. For larger frequencies dispersion of the central directions toward the sources distribution decreases suggesting that scattering of the primary beam pattern plays a key role in propagation comparing to refraction. Our results indicate that type III radio bursts have the apparent source 23 size half-width of 25 - 30 degrees.

Krupar, V.; Santolik, O.; Maksimovic, M.; Cecconi, B.

2010-12-01

259

Radio-wave emission due to hypervelocity impacts and its correlation with optical observations  

NASA Astrophysics Data System (ADS)

This paper describes the most interesting phenomena of radio-wave emission due to hypervelocity impacts. A projectile of polycarbonate with 1.1 g weight was accelerated by a rail gun to 3.8 km/sec, and hit two targets which are a 2 mm thick aluminum plate upstream and a 45 mm diameter aluminum column downstream, respectively. The projectile first breaks wires to give a triggering signal to a data recorder, then penetrates the aluminum plate, and finally hit the column, The emitted radio-waves propagate through the chamber window, and are received by antennas at each frequency band. The receivers in 22 GHz- and 2 GHz-bands consist of a low noise amplifier, a mixer, a local oscillator and an IF amplifier , respectively. The receiver in 1 MHz-band is a simple RF amplifier. The outputs of all receivers are fed to a data recorder which is actually a high-speed digital oscilloscope with a large amount of memory. The radio-waves were successfully recorded in 22 GHz-band with 500 MHz bandwidth, in 2 GHz-band with 300 MHz bandwidth, and in 1MHz-band. The waveforms in 22 GHz- and 2 GHz-bands coincide well each other, and are composed of two groups of sharp impulses with a separation of about 20 micro seconds. The width of an impulse is less than 2 n sec. which is the resolution limit of the data recorder. We carried out optical observations using an ultra-high speed camera simultaneously through another window of the chamber. The time interval between scenes is 2 micro sec. We can see a faint light of the projectile before the first impact to the plate, and then a brilliant gas exploding backward from the plate and forward to the column. After hitting the column target, the brilliant gas flows to the chamber wall and is reflected back to make a mixture with dark gas in the chamber. Excellent correlation between radio-wave emission and the observed optical phenomena was obtained in the experiment. It is easily conceived that the radio-waves consist of quite a wide frequency spectrum because of the spiky waveforms. The emission of the radio-waves is delayed from the optical events by several micro seconds. The optical phenomena are said to be mostly attributed to Bremstrahlung. The radio-wave phenomena are esteemed to be partially due to Bremstrahlung, but mainly due to other causes such as the heating effects of the targets or energy release from broken lattices of the targets.

Takano, T.; Maki, K.; Yamori, A.

260

Influence of temperature treatment on radiation stability of plastic scintillator and wave-length shifter  

Microsoft Academic Search

The influence of temperature treatment before or after irradiation on the radiation damage of plastic scintillators and wavelength shifters was measured. The influence of temperature treatment on the radiation stability before or after irradiation was investigated. The polymethyl-methacrylate (PMMA)-based wavelength shifters showed strong recovery in argon with heating after irradiation, whereas the polystyrene-based scintillator SCSN-38 in air suffered with heating

B. Bicken; A. Dannemann; U. Holm; T. Neumann; K. Wick

1992-01-01

261

NONLINEAR WAVE INTERACTIONS AS EMISSION PROCESS OF TYPE II RADIO BURSTS  

SciTech Connect

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 [Lehrstuhl fuer Astronomie, Universitaet Wuerzburg, Wuerzburg (Germany); Vainio, Rami, E-mail: uganse@astro.uni-wuerzburg.de [Department of Physics, University of Helsinki, Helsinki (Finland)

2012-06-01

262

On radio-wave propagation in forest environments  

Microsoft Academic Search

Propagation of electromagnetic waves in forest environments at medium and high (1-100 MHz) frequencies is examined for the case where both the transmitting and receiving points are situated within the vegetation. A dissipative slab in the presence of a reflecting ionosphere is employed to describe the forest configuration. If the effect of the ground-forest interface is disregarded, the radiated field

T. Tamir; J. Fainberg

1967-01-01

263

The Attenuation vs Frequency Characteristics of VLF Radio Waves  

Microsoft Academic Search

The theoretical dependence on frequency of the attenuation of the wave guide modes in vlf propagation is discussed in some detail. It is indicated that most of the published experimental data between 1 and 30 kc was compatible with the sharply bounded model of the ionosphere with a reflecting height of about 70 km during the day and 90 km

James Wait

1957-01-01

264

Ionospheric scintillation: A brief review  

NASA Astrophysics Data System (ADS)

Irregular diffraction of radio signals by the global ionosphere is studied to predict scintillation using easily measured geophysical parameters. Using a network of equatorial stations it was possible to measure and model the average scintillation characteristics and to relate them to geophysical parameters such as solar flux and geomagnetic indices. Typical models for various stations are shown, including the variations of scintillation as predicted and as measured. The scintillation in auroral regions and the phase distortion caused by the ionosphere are also discussed.

Mullen, J. P.; Aarons, J.; MacKenzie, E. M.

265

The diffraction of VLF radio waves by the Antarctic ice cap  

NASA Astrophysics Data System (ADS)

Measurements of the amplitude and phase of VLF radio signals from the Omega transmitters on La Reunion Island and in Argentina have been made on routine Antarctic re-supply flights from Christchurch, New Zealand. It has been found that when the propagation paths to the transmitters cross the Antarctic ice cap, the direct path signals are very rapidly attenuated below the receiver noise level, the dominant signal source then being provided by the radio waves diffracting around the edge of the ice cap. These results have been made possible by the simultaneous use of the phase and amplitude data in a synthetic aperture antenna type analysis.

Barr, R.

1987-01-01

266

Determining the solar wind speed above active regions using remote radio-wave observations.  

PubMed

A new technique has made it possible to measure the velocity of portions of the solar wind during its flow outward from the sun. This analysis utilizes spacecraft (ISEE-3) observations of radio emission generated in regions of the solar wind associated with solar active regions. By tracking the source of these radio waves over periods of days, it is possible to measure the motion of the emission regions. Evidence of solar wind acceleration during this outward flow, consistent with theoretical models, has also been obtained. PMID:17746203

Bougeret, J L; Fainberg, J; Stone, R G

1983-11-01

267

The propagation of medium radio waves in the ionosphere  

Microsoft Academic Search

All the available measurements of sky-wave intensities at medium frequencies are collated and expressed as field-strength, distance curves for six typical wavelengths and for distances from 25 to 1000 km. It is shown how this material may be used for the determination of the non-fading radii of broadcasting emitters over country of any effective conductivity. From the observational material an

D F Martyn

1935-01-01

268

Laboratory measurements of polarization radios of wind wave surfaces  

Microsoft Academic Search

Polarization ratios (sigma_{vv}\\/sigma_{HH}) of wind-generated rough water surfaces are studied experimentally by means of radar backscatter power measurements. The measurements were made at 9.23 GHz with incidence angles between45degand55degfor wind speeds between 3 m\\/s to 10 m\\/s. Scattering surface statistics at all wind speeds were also measured by means of a wave height gauge and a laser slope gauge. The

PETER H. Y. LEE

1978-01-01

269

Echo power loss with RASS (radio acoustic sounding system) due to defocusing effects by distorted acoustic wave front  

Microsoft Academic Search

We have calculated the intensity of RASS (radio acoustic sounding system) echoes scattered by refractive index fluctuations produced by acoustic waves. Because of temperature changes in the atmosphere, the sound speed decreases in the troposphere and the shape of the acoustic wave front becomes elliptical. When the shape of acoustic wave fronts is significantly distorted from a sphere, the backscattered

Y. Masuda; J. Awaka; K. Okamoto; T. Tsuda; S. Fukao; S. Kato

1990-01-01

270

First experimental evidence of HF produced electron density irregularities in the polar ionosphere; diagnosed by UHF radio star scintillations  

SciTech Connect

HF-produced electron density irregularities with scale sizes of several hundred meters were observed in the polar ionosphere by means of UHF-scintillations using the new facilities at Tromso. HF-power densities as low as 20 ..mu..W/m/sup 2/ excited irregularities during over-dense (HF

Frey, A.; Stubbe, P.; Kopka, H.

1984-05-01

271

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

272

On the problem about determination of the sea wave period based on radio altimeter data  

NASA Astrophysics Data System (ADS)

We consider the features of backscattering of electromagnetic microwaves during nadir sounding of the sea surface. Combined analysis of radar data and sea buoy information allowed us to refine the connection between the parameters of the waves and the reflected radar signal. It is shown that knowing of the wind velocity and the wave steepness or the slope variance of largescale waves is sufficient to calculate the cross section of the backscattering at a zero incidence angle. Several types of wave periods were used as quantitative characteristics of sea waves. It has been shown that the sea wave characteristics can be retrieved from radio altimeter data. The comparison of the retrieved and measured parameters confirmed the efficiency of the developed algorithms. One can state that the allowance for these data in numerical sea wave models will make it possible to improve the accuracy of numerical modeling of the wave environment. A nonmonotonic dependence of wave periods on the backscattering cross section has been found.

Karaev, V. Yu.; Meshkov, E. M.; Cotton, D.; Chu, X.

2013-08-01

273

A radio-on-fiber based millimeter-wave road-vehicle communication system by a code division multiplexing radio transmission scheme  

Microsoft Academic Search

A radio-on-fiber (ROF) based road-vehicle communication system is described in which several radio base stations (RBSs) communicate with a control station (CS) over ROF connections. The RBSs use the same millimeter-wave frequency band to communicate with mobile stations (MSs). The result is one large virtual cellular zone encompassing several RBSs controlled by one CS. However, in one virtual cellular zone,

Hiroshi Harada; Katsuyoshi Sato; Masayuki Fujise

2001-01-01

274

Propagation of 2 GHz Radio Waves Over the English Channel: Analysis of Cases of SubRefraction  

Microsoft Academic Search

This paper presents details about the transhorizon propagation of 2 GHz radio waves over the sea during sub- refractive atmospheric conditions. Sub-refraction is perhaps the most rare of the four refractive conditions (ducting, super-refraction, normal refraction and sub-refraction), but nevertheless cannot be ignored when assessing the performance of a radio link. Specifically, for a 50 km, low-altitude, over-sea radio path

E. M. Warrington; D. R. Siddle

275

An FFT-based Kirchhoff integral technique for the simulation of radio waves in complex environments  

NASA Astrophysics Data System (ADS)

Kirchhoff integral (KI) techniques provide an effective means of simulating radio wave propagation in nonhomogeneous media with complex boundaries. In particular, these techniques can handle quite general boundary topography. Due to the translation-dependent nature of their kernels, however, they cannot take advantage of the fast Fourier transform (FFT) techniques that give the parabolic equation methods their speed. In this paper it is shown that, by means of approximate kernels, the KI technique can be recast in a form where FFT techniques can be applied. Furthermore, through the use of effective reflection coefficients, the technique can handle quite general boundary topography without the need for boundary flattening transformations. The technique is demonstrated through the simulation of several complex 2-D and 3-D radio wave propagation scenarios.

Coleman, Christopher John

2010-04-01

276

Ionospheric heating with oblique waves. Volume 2: Applications to high-frequency radio propagation  

Microsoft Academic Search

This volume presents numerical calculations of ionospheric electron density perturbations and ground-level signal changes for several electric field distributions produced by high-frequency (HF) transmitters. This volume applies theory developed in earlier work (Vol. 1) to the problem of possible self-effects of powerful obliquely incident radio waves. Using the results from this earlier work, we use field-driven changes in ionospheric electron

R. M. Bloom; E. C. Field Jr.

1989-01-01

277

Depolarization of a 50MHz radio wave backscattered from the middle atmosphere  

Microsoft Academic Search

Depolarization properties from the middle atmosphere, which refer to the change in polarization of radio waves, are investigated by using the high-powered 50-MHz radar at Jicamarca (12.0 deg S, 76.9 deg W). The echoes of the pulses transmitted alternately in right and left circular polarizations are received simultaneously by two receivers of each polarization. Small depolarization is generally observed at

K. Wakasugi; S. Kato; S. Fukao

1980-01-01

278

HF radio wave acceleration of ionospheric electrons: Analysis of HF-induced optical enhancements  

Microsoft Academic Search

The shape of the HF-pump modified electron energy distribution has long been a central question in the field of ionospheric high-frequency radio wave modification experiments. Here we present estimates of the enhanced differential electron flux, from 1.9 to 100 eV based on optical multiwavelength (6300, 5577, 8446, and 4278 Å) data and 930 MHz incoherent scatter radar measurements of ion

B. Gustavsson; B. Eliasson

2008-01-01

279

Spatiotemporal evolution of radio wave pump-induced ionospheric phenomena near the fourth electron gyroharmonic  

Microsoft Academic Search

On 12 November 2001, the European Incoherent Scatter (EISCAT) high-frequency (HF) radio wave transmitter facility, operating in O-mode at 5.423 MHz with 550 MW effective radiated power, produced artificial optical rings which appeared immediately at transmitter turn-on and collapsed into blobs after ~60 s while descending in altitude. A similar descent in altitude was observed in the EISCAT ultra high

M. Ashrafi; K. Kaila; B. Isham

2007-01-01

280

VHF radio wave scattering due to range and frequency types of equatorial spread-F  

Microsoft Academic Search

Comparing vertical incidence ionograms during spread-F conditions at the equatorial station Huancayo and modified range time intensity records of 50 MHz scatter echoes at Jicamarca, it has been shown that the range type of spread-F is very efficient for the back-scattering of VHF radio waves. On the other hand, the frequency type of spread-F does not seem to produce strong

R. G. Rastogi; R. F. Woodman

1978-01-01

281

Spatiotemporal evolution of radio wave pump-induced ionospheric phenomena near the fourth electron gyroharmonic  

Microsoft Academic Search

On 12 November 2001, the European Incoherent Scatter (EISCAT) high-frequency (HF) radio wave transmitter facility, operating in O-mode at 5.423 MHz with 550 MW effective radiated power, produced artificial optical rings which appeared immediately at transmitter turn-on and collapsed into blobs after ?60 s while descending in altitude. A similar descent in altitude was observed in the EISCAT ultra high

M. Ashrafi; M. J. Kosch; K. Kaila; B. Isham

2007-01-01

282

Propagation of VHF Radio Waves on Sea Routes in the South Polar Latitudes  

Microsoft Academic Search

We present the results of meteorological and radiometeorological observations as well as the results of measurements of the attenuation factor of very-high-frequency (VHF) radio waves during the 28th Soviet Antarctic expedition in January–March 1983. It is shown that radiometeorological parameters over the South ocean area in summer almost coincide with the corresponding averaged parameters over the land in winter. The

V. K. Ivanov; V. N. Lanovoy; V. N. Shalyapin; L. A. Egorova; A. S. Vasil'yev; A. A. Mogila

2005-01-01

283

Experimental verification of the dimer-absorption mechanism of radio waves in the earth's atmosphere  

Microsoft Academic Search

Data obtained on the research vessel Akademik Kuchatov in the framework of the TROPEX-74 and GATE-74 programs are analyzed in order to elucidate radio-wave propagation in water-vapor dimers in the atmosphere. It is found that the upper limit to total vertical absorption in dimers does not exceed 2 percent of the absorption in monomers, the dimer density in the atmosphere

V. M. Plechkov; K. S. Stankevich

1990-01-01

284

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

285

Storm time, short-lived bursts of relativistic electron precipitation detected by subionospheric radio wave propagation  

Microsoft Academic Search

In this study we report on ground-based observations of short bursts of relativistic electron precipitation (REP), detected by a subionospheric propagation sensor in Sodankylä, Finland during 2005. In two ~4 hour case study periods from L = 5.2, around local midnight, several hundred short-lived radio wave perturbations were observed, covering a wide range of arrival azimuths. The vast majority (~99%)

Craig J. Rodger; Mark A. Clilverd; David Nunn; Pekka T. Verronen; Jacob Bortnik; Esa Turunen

2007-01-01

286

Attenuation in melting snow on microwave- and millimetre-wave terrestrial radio links  

Microsoft Academic Search

The scattering properties of melting snow on microwave and millimeter-wave terrestrial radio links are predicted using a new model for melting which includes coalescence. Attenuation, differential attenuation and differential phase are calculated for a horizontal path, with results at 36.25 GHz presented. Peak specific attenuation in the range 8-13 dB\\/km is expected for underspread rain with 10-15 mm\\/h rain rates.

Y. M. Jain; P. A. Watson

1985-01-01

287

Fractal-Based Modeling of Radio-Wave Scattering from the Surface of Venus  

Microsoft Academic Search

The use of fractal geometry has become increasingly attractive both as a model for natural surfaces and as the basis for a new generation of radio-wave scattering laws. The apparent advantages of the fractal-based (F-B) laws over classical laws, which typically are parameterized by a surface power reflection coefficient and a surface RMS slope-related parameter, are that (i) F-B laws

G. L. Tyler; A. K. Sultan-Salem

2005-01-01

288

Hyperstrong Radio-Wave Scattering and Free Electrons in the Galactic Center  

Microsoft Academic Search

The scattering [index interstellar scattering! angular broadening] diameters of Sgr A* [index Source! Sgr A*] and several nearby OH masers (? 1 arcsec at 1 GHz) indicate that a region of enhanced scattering [index interstellar scattering] is along the line of sight to the Galactic center. We have combined radio-wave scattering data and free-free emission [index free-free emission] measurements in

T. J. W. Lazio; J. M. Cordes; K. R. Anantharamaiah; W. M. Goss; N. E. Kassim

1999-01-01

289

An SBR\\/image approach for radio wave propagation in indoor environments with metallic furniture  

Microsoft Academic Search

In this paper, we propose a deterministic approach to model the radio wave propagation channels in complex indoor environments. This technique applies the modified shooting-and-bouncing-ray (SBR) method to find the equivalent sources (images) for each launched ray tube. In addition, the first-order wedge diffraction from furniture is included and the diffracted rays also can be attributed to the corresponding images.

Shin-Hon Chen; Shyh-Kang Jeng

1997-01-01

290

High resolution of electromagnetic waves in time-varying radio channels  

Microsoft Academic Search

The applicability of the SAGE (space-alternating generalized expectation-maximization) algorithm to the estimation of time variant radio channels is demonstrated. This algorithm allows one to separate the complex multi-dimensional optimization problem required to compute the estimate of the parameters characterizing the impinging waves, i.e. their delay, incidence azimuth, Doppler frequency, and complex amplitude, into separate one dimensional optimization processes that can

Klaus I. Pedersen; Bernard H. Fleury; Preben E. Mogensen

1997-01-01

291

Wavelength interleaving towards DWDM and spectral efficiency in dual-toned millimeter-wave radio-over-fiber systems [invited  

Microsoft Academic Search

Wavelength interleaving scheme that has the potential to implement DWDM channel spacing smaller than the millimeter-wave radio frequencies in high-speed radio-over-fiber systems are addressed. Optical subsystems potentially enabling the scheme practically are also briefly discussed.

Masuduzzaman Bakaul; Ampalavanapillai Nirmalthas; Christina Lim; Dalma Novak; R. Waterhouse

2009-01-01

292

Auroral absorption of HF radio waves in the ionosphere: A review of results from the first decade of riometry  

Microsoft Academic Search

In the decade since the International Geophysical Year, information about the ionospheric absorption of radio waves during periods of auroral and magnetic disturbance has been greatly increased by the use of the riometer technique. Such studies are important for their geophysical implications as well as in direct applications to radio propagation. The purpose of this paper is to summarize the

J. K. Hargreaves

1969-01-01

293

All-optical subcarrier demodulation in upstream link of millimeter-wave radio over fiber system.  

PubMed

A means to achieve all-optical broadband demodulation of subcarrier back into digital data in an upstream link of a millimeter-wave radio over fiber (RoF) system is proposed and demonstrated experimentally. In the central station, the subcarrier from the base station of RoF system can be demodulated in the optical domain directly, without any millimeter-wave electronic device. Using this approach, the rf power degradation can be avoided even when the base stations in systems employ the conventional simple double-sideband modulation. Therefore, an inexpensive and simple configuration of the uplink for broadband signal receiving can be realized. PMID:17671599

Song, Yiqiao; Zheng, Xiaoping; Zhang, Hanyi; Guo, Yili; Zhou, Bingkun

2007-08-01

294

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

NASA Astrophysics Data System (ADS)

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 with a canonical transform maps the wave field to a different representation. Mapping to the representation of ray impact parameter was used in the formulation of the canonical transform (CT) method for processing radio occultation data. The full-spectrum inversion (FSI) method can also be looked at as an FIO associated with a canonical transform of a different type. We discuss the general principles of the theory of FIOs and formulate a generalization of the CT and FSI techniques. We derive the FIO that maps radio occultation data measured along the low Earth orbiter orbit without first applying back propagation. This operator is used for the retrieval of refraction angles and atmospheric absorption. We give a closed derivation of the exact phase function of the FIO obtained in the "phase matching" approach by [2004] We derive a novel FIO algorithm denoted CT2, which is a modification and improvement of FSI. We discuss the use of FIOs for asymptotic direct modeling of radio occultation data. This direct model is numerically much faster then the multiple phase screen technique. This is especially useful for simulating LEO-LEO occultations at frequencies of 10-30 GHz.

Gorbunov, M. E.; Lauritsen, K. B.

2004-08-01

295

Search for non-thermal radio emission from Eta Carina's outer blast wave with ATCA  

NASA Astrophysics Data System (ADS)

Non-thermal hard X-ray and high-energy (HE; 1 MeV < E < 100 GeV) gamma-ray emission in the direction of Eta Carina has been recently detected using the INTEGRAL, AGILE and Fermi satellites. This emission can be either interpreted in the framework of particle acceleration in the colliding wind region between the two massive stars or in the very fast moving blast wave which originates in the historical 1843 "Great Eruption". The detection of a radio shell at the location of the shock would support the latter scenario and confirm Eta Carina as prime example of a new source type, namely, an LBV star whose massive ejecta accelerates electrons to non-thermal energies. While Fermi and INTEGRAL do not provide sufficient angular resolution to resolve the blast wave, high resolution radio observations using ATCA will be able to test non-thermal radio emission from this acceleration site. The current sensitivity of ATCA is such that a relatively modest observation time of 12 hours will be sufficient to image the synchrotron emission from the blast region down to magnetic field strengths well below typical ISM values and hence prove or reject our blast-wave hypothesis for the high energy emission.

Ohm, Stefan; Urquhart, James; Skilton, Joanna Lucy; Hinton, Jim; Domainko, Wilfried

2010-10-01

296

Attenuation and phase variation of millimeter and centimeter radio waves in a medium consisting of dry and wet dust particles  

Microsoft Academic Search

The attenuating and refracting properties of wet dust particles with sand and loam nuclei at wavelengths of about 0.1–10 cm are considered. Quantitative characteristics of radio-wave attenuation obtained for various models of homogeneous particles with effective permittivity are compared with an exact solution of the electrodynamic problem for two-layer particles (“sphere in envelope”). Radio-wave phase variations caused by the presence

E. N. Vinyaikin; M. B. Zinicheva; A. P. Naumov

1994-01-01

297

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

Microsoft Academic Search

Various papers on the ionosphere and radio wave propagation are presented. The subjects discussed include: day-to-day variability in foF2 at low latitudes over a solar cycle; semiempirical, low-latitude ionospheric model; remote sensing with the Jindalee skywave radar; photographic approach to irregularities in the 80-100 km region; interference of radio waves in a CW system; study of the F-region characteristics at

D. G. Cole; L. F. McNamara

1985-01-01

298

Fokker-Planck description of the scattering of radio frequency waves at the plasma edge  

SciTech Connect

In magnetic fusion devices, radio frequency (rf) waves in the electron cyclotron (EC) and lower hybrid (LH) range of frequencies are being commonly used to modify the plasma current profile. In ITER, EC waves are expected to stabilize the neoclassical tearing mode (NTM) by providing current in the island region [R. Aymar et al., Nucl. Fusion 41, 1301 (2001)]. The appearance of NTMs severely limits the plasma pressure and leads to the degradation of plasma confinement. LH waves could be used in ITER to modify the current profile closer to the edge of the plasma. These rf waves propagate from the excitation structures to the core of the plasma through an edge region, which is characterized by turbulence--in particular, density fluctuations. These fluctuations, in the form of blobs, can modify the propagation properties of the waves by refraction. In this paper, the effect on rf due to randomly distributed blobs in the edge region is studied. The waves are represented as geometric optics rays and the refractive scattering from a distribution of blobs is formulated as a Fokker-Planck equation. The scattering can have two diffusive effects--one in real space and the other in wave vector space. The scattering can modify the trajectory of rays into the plasma and it can affect the wave vector spectrum. The refraction of EC waves, for example, could make them miss the intended target region where the NTMs occur. The broadening of the wave vector spectrum could broaden the wave generated current profile. The Fokker-Planck formalism for diffusion in real space and wave vector space is used to study the effect of density blobs on EC and LH waves in an ITER type of plasma environment. For EC waves the refractive effects become important since the distance of propagation from the edge to the core in ITER is of the order of a meter. The diffusion in wave vector space is small. For LH waves the refractive effects are insignificant but the diffusion in wave vector space is important. The theoretical model is general enough to study the effect of density blobs on all propagating cold plasma waves.

Hizanidis, Kyriakos; Kominis, Yannis; Tsironis, Christos [School of Electrical and Computer Engineering, National Technical University of Athens, Athens GR 15773 (Greece); Ram, Abhay K. [Plasma Science and Fusion Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2010-02-15

299

Miyun metre-wave aperture synthesis radio telescope  

NASA Astrophysics Data System (ADS)

The Miyun metre-wave aperture synthesis radiotelescope, working at frequency of 232 MHz, consists of an E-W array of 28 elements, each of 9 m aperture. 192 baselines are effected with a full coverage of the U-V plane (Fig. 2). The longest baseline is 1,164m. This instrument is designed for source survey and detection of peculiar sources in northern declinations. A set of observations completed in 2 × 12 hours gives a thermal noise limited sensititity of 0.05 Jy and a resolution of 3'8 × 3'8 csc ?. The field of view is 8° × 8°. This should enable us to complete an overall survey of the region ? >= + 30° within two years, and to carry out monitoring of selected areas. Figures 1 and 2 show the main properties and general design of the instrument and Figures 3 and 4 give some preliminary results of sky mapping. The following persons took part in the designing and making of the telescope: WANG Hong, Wang Xin-min, Wang Shou-guan, Liu Fu-you, Pu Ting-yi, Chen Hong-shen, Qiu Yu-hai, Yang Yi-pei, Pang Lei, Zhang Chun-lu, Zhang Guo-quan, Zhang Xi-zhen, Jin Tie-lin, Zheng Yi-jia, Zhao Hui-ping, Nan Ren-dong, Kang Lian-sheng, Bao Hong-qi, Wei Ming-zhi.

1986-03-01

300

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

301

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

302

Aging studies on stressed and unstressed scintillating, wave-shifting, and clear fibers  

NASA Astrophysics Data System (ADS)

For the upgrade in 1998, the Fermilab D-Zero collaboration will install detectors which have many thousand scintillating and wavelength shifting fibers coupled to clear lightguide fibers. Our objective was to study whether the fibers' performance will deteriorate with age. Aging in these three kinds of fibers were studied by measuring attenuation lengths and light yields as a function of time. Attenuation lengths of scintillating and wavelength shifting fibers were measured using an ultraviolet light source and effective light yields of scintillating fibers were measured using a (superscript 207)Bi radiation source. For clear fibers, attenuation measurements were made using light from a green light-emitting diode. Scintillating fibers have shown no noticeable changes in attenuation lengths and light yields over periods of up to 3.5 years when they were stored properly. Wavelength shifting fibers have been studied for a period of five months and have shown no degradation. Clear fibers have been studied over periods of up to seven months and have shown a reduction of a few percent in the attenuation length. These will have to be monitored for a longer period of time to establish if the effect is significant. The effects of aging on mechanically stressed fibers have also been studied. Light transmissions in clear fibers coiled into loops of various radii have been compared to transmissions in straight fibers. The stressed fibers have shown no change in the light loss for almost one year. The observations made over the past 3.5 years indicate that fiber aging is not a serious problem, however, the clear fibers require further investigation.

Chung, Manho; Margulies, Seymour

1995-09-01

303

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

304

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

305

Survey of electric field shear driven by radio frequency waves in tokamak plasmas  

SciTech Connect

The stabilization of plasma turbulence by sheared poloidal rotation is thought to explain enhanced confinement in tokamak plasmas. One method proposed for controlling sheared flow is the use of externally driven radio-frequency (RF) waves. A number of calculations and some experiments have suggested that a modest amount of power in the ion cyclotron range of frequencies (ICRF) can drive the needed flows. Previous calculations have relied on incompressible fluid models which balance RF forces in the poloidal direction against neoclassical viscosity. But the incompressible assumption is not always valid, particularly for ion Bernstein waves (IBW). Also, since the IBW is a kinetic wave by nature, a fully consistent model should include kinetic effects. In this paper, RF driven flows are calculated from both compressible fluid and kinetic points of view.

Jaeger, E.F.; Berry, L.A.; Batchelor, D.B.

1998-11-01

306

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

307

Surface-wave data acquisition and dissemination by VHF packet radio and computer networking  

NASA Astrophysics Data System (ADS)

Waverider buoy data are normally transmitted on a 27 MHz analog radio link to a shore station a few miles away, where the buoy data are plotted on a paper strip-chart recorder or logged digitally for later computer processing. Instead, we have constructed a relay station on Martha's Vineyard island that retransmits the received Waverider data over a digital, 148 MHz packet-radio link a personal computer in our laboratory on Cape Cod, where the data are edited, processed, spectrally analyzed, and then sent over an Ethernet line to our Institution mainframe computer for archiving. Telephone modem access of a special wave-data file on the mainframe permits unattended data dissemination to the public. The report describes the entire system, including Waverider buoy mooring hardware, computer programs, and equipment. The purpose of the project was to learn what difficulties are involved in the automated acquisition and dissemination of telemetered oceanographic data, and to gain experience with packet radio techniques. Although secondary to these purposes, the long-term surface-wave monitoring off the southwest shore of Martha's Vineyard has its own scientific, engineering, and environmental benefits.

Briscoe, M.; Denton, E.; Frye, D.; Hunt, M.; Montgomery, E.

1988-04-01

308

Jovian non-thermal radio emission observed by STEREO/WAVES  

NASA Astrophysics Data System (ADS)

Solar TErrestrial RElations Observatory (STEREO) consists of two 3-axis-stabilized identical spacecraft (STEREO-A and STEREO-B), launched on Oct. 25, 2006. The WAVES experiment onboard STEREO is a radio burst tracer which observes the generation and evolution of the radio disturbances from the Sun to the orbit of Earth. Being mainly dedicated for measuring solar radio bursts, SWAVES also provided unique observations of the Jovian planetary radio emission. For the first time Jovian radiation is observed stereoscopically by two identical spacecraft in a frequency range from few kHz up to 16 MHz. The data recorded during more than two years (Nov 2006 - Dec 2008) of mission operations is analyzed. A big amount of the events of non-Io and Io controlled "arc-like" decametric components of the Jovian radiation (DAM) as well as hectometric emission (HOM) has been recorded. The unique stereoscopic observations by STEREO provide the opportunity to determine the propagation characteristics of the Jovian non-thermal radiation such as directivity and beam width of the emission cone. First results will be presented.

Rucker, H. O.; Panchenko, M.; Shaposhnikov, V. E.; Melnik, V. N.; Boudjada, M. Y.; Stereo Team

2009-04-01

309

Forecasting Ionospheric Real-time Scintillation Tool (FIRST)  

Microsoft Academic Search

It is well-known that the generation of equatorial, F-region plasma density irregularities, via the Generalized Rayleigh-Taylor instability mechanism is critically dependent on the magnitude of the pre-reversal enhancement (PRE) in upward ExB drift velocity after sunset. These plasma density bubbles that are generated after sunset lead to the scintillation of trans-ionospheric radio wave signals that pass through these bubbles and

D. N. Anderson; R. Redmon; T. Bullett; R. G. Caton; J. M. Retterer

2009-01-01

310

Radio and Plasma Wave Observations From the Cassini and Galileo Spacecraft During the Cassini Flyby of Jupiter  

Microsoft Academic Search

During the Cassini flyby of Jupiter, which occurred on December 30, 2000, simultaneous data were collected from the Galileo spacecraft, which is in orbit around Jupiter, and from the Cassini spacecraft. In this paper we report results from the Radio and Plasma Wave Science (RPWS) instrument on the Cassini spacecraft and from the Plasma Wave Science (PWS) instrument on the

D. Gurnett; W. Kurth; G. Hospodarsky; A. Persoon; H. Alleyne; S. Bolton; R. Bostrom; P. Canu; N. Cornilleau-Wehrlin; M. Desch; W. Farrell; P. Galopeau; K. Goetz; G. Gustafsson; C. Harvey; M. Kaiser; P. Kellogg; H. P. Ladreiter; A. Lecacheux; P. Louarn; A. Pedersen; A. Roux; H. Rucker; J. Wahlund; P. Zarka

2001-01-01

311

Role of aspect-sensitive scattering at auroral inhomogeneities in the slip mechanism of radio-wave propagation  

Microsoft Academic Search

The effect of aspect-sensitive scattering of radio waves at magnetically oriented inhomogeneities of the auroral ionosphere on the energy output from the ionospheric wave channel is investigated. A good agreement of the results of the computation of the zone of optimal reception of signals scattered at ardsotrop~c inhomogeneities of the south auroral zone is obtained with the experimental data from

S. N. Matyugin; V. P. Uryadov

1977-01-01

312

Some key technologies for millimeter-wave radio-over-fiber systems based on injection locked lasers  

Microsoft Academic Search

The seamless integration of broadband optical and wireless access networks is considered to be a promising solution for next generation access networks which will provide high capacity and flexibility with lower cost. In such access networks millimeter wave (mm-wave) radio over fiber (RoF) system is a key enabling technology due to its its large bandwidth and short reach in atmosphere.

Zhangyuan Chen; Weiwei Hu; Cheng Hong; Cheng Zhang; Mingjin Li; Yushu Chen; Xiang Wang

2008-01-01

313

The coherer: with simple demonstrations of the generation, propagation and detection of radio waves  

NASA Astrophysics Data System (ADS)

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 (tens of ohms). This state persists until the device is mechanically disturbed, whereupon the high resistance state is restored. This characteristic was employed by scientists in the 1890s to detect radio waves, and applied commercially by Marconi in his 'wireless' telegraph. It is easy to make a working coherer and directions are given for operating it from a distance with a spark transmitter based on a piezoelectric gas igniter. Incorporation of an 'aerial' and 'earth' enable a range of 7 m to be achieved and simple signals may be transmitted.

Mills, Allan

2010-03-01

314

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

315

Convectively generated internal gravity waves in Venus's middle atmosphere  

Microsoft Academic Search

We investigate the emission of internal gravity waves from dry convection in Venus's atmosphere, how they might support Venus's atmospheric superrotation, and how they manifest themselves in radio scintillation data. Firstly, we calculate the emission of gravity waves from dry convection between 50 and 55 km altitude in Venus's atmosphere. We assume order of magnitude estimates for nonlinear terms in

Stephen Sylvain Leroy

1994-01-01

316

Effects of gravity waves on eclipse time absorption of radio waves  

Microsoft Academic Search

Ionograms and amplitude measurements at 2.7 MHz taken during the solar eclipse of February 16, 1980, at Gauhati University (India) are discussed. Abnormally low absorption observed during the maximum eclipse effect condition is linked with the formation of distortions or curvatures in the reflecting surface produced by the gravity waves generated during the eclipse. The wave variation pattern of f(0)F2,

M. Devi; A. K. Barbara; P. Talukdar

1982-01-01

317

Science Sampler: Radio-wave inquiry with web-controlled receivers  

NSDL National Science Digital Library

This article describes a web-enhanced investigation of radio waves suitable for upper middle school science students that correlates with the National Science Education Standards. In this engaging lesson, students are involved in science inquiry using internet-linked instruments to observe and study electromagnetic radiation, one of the fundamental forces of nature. It follows the learning cycle phases of exploring, inventing or introducing, and applying a concept (Abraham 1997). This investigation builds on previous work by incorporating the unique twist of having students use high-quality, web-controlled receivers (Wise 2006, 2007).

Wise, Kevin

2007-04-01

318

Measurements and predictions of HF ground wave radio propagation over irregular, inhomogeneous terrain  

NASA Astrophysics Data System (ADS)

Measurements of radio propagation path loss were made over four paths in the 3 to 30 MHz band. The paths were of lengths up to 45 km. They ranged from smooth to mountainous terrain, from open areas with few or no man-made structures to suburban areas with building heights up to three stories, and from open spaces with little vegetation to heavily forested regions. On one path, measurements were made with and without snow cover. The measurements were made in the daytime and because of the short paths, the primary mode of propagation was ground wave. Measurements of the ground constants at each of the four measurement frequencies were made at the transmitter site using the wave-tilt measurement technique.

Adams, J. E.; Carroll, J. C.; Costa, E. A.; Ebaugh, D. R., Jr.; Godwin, J. R.; Haakinson, E. J.; Layton, D. H.; Smith, D.

1984-07-01

319

Jovian plasma sheet density profile from low-frequency radio waves  

NASA Astrophysics Data System (ADS)

By using planetary radio astronomy (PRA), plasma wave system (PWS), and magnetometer (MAG) data from Voyager 1 and 2 (V1 and V2), essential features of the nightside Jovian plasma sheet are derived, and the density gradient of the corotating plasma structure in the middle Jovian magnetosphere is calculated. The PRA experiment gives information about the plasma wave polarization. The density profile of the plasma sheet is determined using the hinge point position of the plasma disk derived from MAG data, and the low-frequency cutoffs observed at three frequencies (562 Hz, 1 kHz, and 1.78 kHz) from the PWS experiment. It is shown that the hinge point position varies with the solar wind ram pressure.

Rucker, H. O.; Ladreiter, H. P.; Leblanc, Y.; Jones, D.; Kurth, W. S.

1989-04-01

320

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

321

A review of recent observations of equatorial scintillations and their relationship to current theories of F region irregularity generation  

Microsoft Academic Search

Our understanding of transionospheric radio wave propagation problems associated with irregularities in the nighttime equatorial F region has grown enormously in the past few years. This has been achieved by making coordinated phase and amplitude scintillations from a host of geostationary and orbiting satellites and multitechnique irregularity measurements. The variety of supporting measurements include radar backscatter, in situ irregularity observations

Sunanda Basu; M. C. Kelley

1979-01-01

322

PROGRESS IN MEASUREMENTS OF THE GRAVITATIONAL BENDING OF RADIO WAVES USING THE VLBA  

SciTech Connect

We have used the Very Long Baseline Array (VLBA) at 43, 23, and 15 GHz to measure the solar gravitational deflection of radio waves among four radio sources during an 18 day period in 2005 October. Using phase-referenced radio interferometry to fit the measured phase delay to the propagation equation of the parameterized post-Newtonian formalism, we have determined the deflection parameter {gamma} = 0.9998 {+-} 0.0003 (68% confidence level), in agreement with general relativity. The results come mainly from 43 GHz observations where the refraction effects of the solar corona were negligible beyond 3 deg from the Sun. The purpose of this experiment is three-fold: to improve on the previous results in the gravitational bending experiments near the solar limb; to examine and evaluate the accuracy limits of terrestrial VLBI techniques; and to determine the prospects and outcomes of future experiments. Our conclusion is that a series of improved designed experiments with the VLBA could increase the presented accuracy by at least a factor of 4.

Fomalont, E. [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States); Kopeikin, S. [Department of Physics and Astronomy, University of Missouri, Columbia, MO 65211 (United States); Lanyi, G. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Benson, J. [National Radio Astronomy Observatory, Socorro, NM 87801 (United States)], E-mail: efomalon@nrao.edu, E-mail: kopeikins@missouri.edu, E-mail: gabor.e.lanyi@jpl.nasa.gov, E-mail: jbenson@nrao.edu

2009-07-10

323

Progress in Measurements of the Gravitational Bending of Radio Waves Using the VLBA  

NASA Astrophysics Data System (ADS)

We have used the Very Long Baseline Array (VLBA) at 43, 23, and 15 GHz to measure the solar gravitational deflection of radio waves among four radio sources during an 18 day period in 2005 October. Using phase-referenced radio interferometry to fit the measured phase delay to the propagation equation of the parameterized post-Newtonian formalism, we have determined the deflection parameter ? = 0.9998 ± 0.0003 (68% confidence level), in agreement with general relativity. The results come mainly from 43 GHz observations where the refraction effects of the solar corona were negligible beyond 3 deg from the Sun. The purpose of this experiment is three-fold: to improve on the previous results in the gravitational bending experiments near the solar limb; to examine and evaluate the accuracy limits of terrestrial VLBI techniques; and to determine the prospects and outcomes of future experiments. Our conclusion is that a series of improved designed experiments with the VLBA could increase the presented accuracy by at least a factor of 4.

Fomalont, E.; Kopeikin, S.; Lanyi, G.; Benson, J.

2009-07-01

324

Atmospheric absorption of radio waves in the region of the rotational resonance of water vapor at ??1.35 cm  

Microsoft Academic Search

UDC 621.371.246 An experimental study is reported of the vertical absorption of radio waves with X ~ 1.25 cm by atmospheric water molecules and oxygen, using the intrinsic radio emission of the atmosphere. It is shown that the absorption coefficient of tt20 vapor near the rotational resonance at X -~ 1.35 cm, obtained from measurements of vertical absorption on the

V. M. Plechkov

1969-01-01

325

Water-Wave Effects on Radio Wave Propagation in the Ocean.  

National Technical Information Service (NTIS)

A sinusoidal surface profile is used to study by an exact method the effect of water waves on an electromagnetic field propagating downwards from the surface. It is assumed that the magnetic field is directed parallel to the surface corrugations. The resu...

M. L. Burrows

1970-01-01

326

Cluster merger blast wave and the mystery of ringlike radio-relic formation around some galaxy clusters  

NASA Astrophysics Data System (ADS)

In this work I studied the nature and important effects of massive galaxy cluster merger phenomena. Due to inherent complexity of such events analytical solution is impossible, so, numerical simulations are performed using ENZO-2.1 hydrodynamic code. It is noticed that the formation of Mega parsec scale merger shocks in such events substantially change the energy distribution of Inter Cluster Medium. A striking similarity is noticed between expanding intra cluster medium during mergers with the blast wave formation in supernovae explosion. The blast wave meets the void/ accretion shocks when propagated out to the virial radius. Particle acceleration at the meeting point produce a significant amount of synchrotron radio emission through which curved shocks are made visible in radio waves. This study thus also sheds some light on the formation of curved and nearly symmetric radio emission found in Abell 3376, Abell 3667, CIZA J2242.8+5301, plck g287.0+32.9 etc. clusters.

Paul, Surajit

2012-12-01

327

Ionospheric disturbances during November 30-December 1, 1988. XI - Abnormal propagations of HF and VHF radio waves  

NASA Astrophysics Data System (ADS)

Unusual propagations of HF and VHF radio waves associated with a geomagnetic storm during the period from November 30 to December 1, 1988 are investigated using ionospheric data collected from Japan, China, and Taiwan. The increased field strength of the Japanese frequency standard signals (JJY 2.5 MHz and 5 MHz) which were received at Akita Radio Wave Observatory on the night of November 30 seem to have been caused by increased MUFs and/or scattering due to the disturbed ionosphere. The VHF-TV radio waves propagated from China were received at Kokubunji in Tokyo. One of the most probable mechanisms explaining this unusual propagation of VHF is a one-hop-F2 mode of propagation created by an ionosphere with an anomalously high f0F2. It was found out that these unusual HF and VHF propagations were attributed to unusual ionospheric conditions associated with these geomagnetic disturbances.

Ichinose, Masaru; Kamata, Mitsuhiro

1992-07-01

328

A new approach to global gravity wave momentum flux determination from GPS radio occultation data  

NASA Astrophysics Data System (ADS)

GPS Radio Occultation (RO) is a well-established technique for obtaining global gravity wave (GW) information. RO uses GPS signals received aboard low Earth orbiting satellites for atmospheric limb sounding. Temperature profiles are derived with high vertical resolution and provide a global coverage under any weather conditions offering the possibility for global monitoring of the vertical temperature structure and atmospheric wave parameters. The six satellites constellation COSMIC/FORMOSAT-3 delivers approximately 2000 temperature profiles daily. In this study, we use a method to obtain global distributions of horizontal gravity wave wavelengths, to be applied in the determination of the vertical flux of horizontal momentum transported by gravity waves. The horizontal wavenumber is derived by the ratio of the phase shift and the spatial distance between adjacent temperature fluctuation profiles at a given altitude, following the method by Ern et al. (2004). A new method for the determination of the real horizontal wavelength from triads of vertical profiles is presented and applied to the COSMIC data. The horizontal and vertical wavelength, the specific potential energy (Ep) and the vertical flux of horizontal momentum (MF) are calculated and their global distribution is discussed.

Faber, A.; Llamedo, P.; Schmidt, T.; de la Torre, A.; Wickert, J.

2013-03-01

329

Global Gravity Wave Momentum Flux Determination from Triads of GPS Radio Occultation Profiles  

NASA Astrophysics Data System (ADS)

The GPS Radio Occultation technique (RO) is a well-established technique for obtaining global gravity wave (GW) information from temperature profiles. RO uses GPS signals received aboard low Earth orbiting satellites for atmospheric limb sounding. Temperature profiles are derived with high resolution and provide a global coverage under any weather conditions offering the possibility for global monitoring of the temperature structure and wave parameters. The six satellites constellation COSMIC/FORMOSAT-3 delivers approximately 1800 temperature profiles daily. In this study, we derive global distributions of vertical and horizontal save numbers and wave potential energy, needed to compute the momentum flux. The horizontal wavenumber kh is derived by the ratio of the phase shift ??ij and the spatial distance ?xij between the regarded profiles at a given altitude (kh = ??ij/?xij). To extract the horizontal wavelength along the wave propagation direction, a third measurement is needed. These triads must be close in time and space. The horizontal and vertical wavelength, the specific potential energy (Ep), the vertical flux of horizontal momentum (MF) is calculated and possible trends are discussed. The horizontal wavelength distribution shows results between 2000 and 3000 km with larger wavelength toward the equator and on the winter hemisphere. Global analysis including seasonal mean results of vertical wavelength and potential energy in an altitude range of 20 to 30 km are discussed, too.

Faber, Antonia; Llamedo, Pablo; Schmidt, Torsten; de la Torre, Alejandro; Wickert, Jens; Heise, Stefan

2013-04-01

330

Evaluation of uncertainty in gravity wave potential energy calculations through GPS radio occultation measurements  

NASA Astrophysics Data System (ADS)

The application of the Global Positioning System (GPS) radio occultation (RO) method to the atmosphere enables the determination of height profiles of temperature, among other variables. From these measurements, gravity wave activity is usually quantified by calculating the potential energy through the integration of the ratio of perturbation and background temperatures between two given altitudes in each profile. The uncertainty in the estimation of wave activity depends on the systematic biases and random errors of the measured temperature, but also on additional factors like the selected vertical integration layer and the separation method between background and perturbation temperatures. In this study, the contributions of different parameters and variables to the uncertainty in the calculation of gravity wave potential energy in the lower stratosphere are investigated and quantified. In particular, a Monte Carlo method is used to evaluate the uncertainty that results from different GPS RO temperature error distributions. In addition, our analysis shows that RO data above 30 km height becomes dubious for gravity waves potential energy calculations.

Luna, D.; Alexander, P.; de la Torre, A.

2013-09-01

331

Z-Mode Waves as the Source of Saturn Narrowband Radio Emissions  

NASA Astrophysics Data System (ADS)

We report ~5 kHz narrowband Z-mode emissions observed by the Cassini Radio Plasma Wave Science (RPWS) instrument during high latitude perikrone passes. The narrowband emissions observed below the local electron cyclotron frequency (fce) are >20 dB more intense than the usual L-O mode narrowband emissions observed above local fce. Polarization measurements show that the narrowband emissions observed below fce are oppositely polarized to those above fce, which identifies the emissions below fce as Z-mode waves. We propose that the L-O mode narrowband emissions observed at ~5 kHz are mode converted from the Z-mode waves at a density gradient or density irregularity. The Z- mode to O-mode conversion via scattering off of density irregularities can also account for the direction finding results of ~5 kHz narrowband emissions that cannot be explained by the model in Ye et al. [2008], where narrowband emissions are first generated as electrostatic upper hybrid waves when the matching condition fUH = (n+1/2)fce is satisfied.

Ye, S.; Menietti, J. D.; Fischer, G.; Gurnett, D. A.; Kurth, W. S.; Wang, Z.

2008-12-01

332

Effect of electron-density gradients on propagation of radio waves in the mid-latitude trough. Master's thesis  

SciTech Connect

Partial contents of this thesis include: (1) Radio-wave propagation and the mid-latitude trough; (2) Ionospheric measurements; (3) Modification of time-dependent ionospheric model output with latitudinal electron-density profiles from digisonde trough depictions; (4) Ray-tracing simulations to examine ground range; and (5) Effects of three-dimensional gradients in electron density on radio-wave propagation in the trough region. Data is tabulated for geophysical conditions, solar activity level, geomagnetic activity level, conditions for vertical ray refraction to surface, and ray-tracing fixed-input conditions.

Citrone, P.J.

1991-01-01

333

Some key technologies for millimeter-wave radio-over-fiber systems based on injection locked lasers  

NASA Astrophysics Data System (ADS)

The seamless integration of broadband optical and wireless access networks is considered to be a promising solution for next generation access networks which will provide high capacity and flexibility with lower cost. In such access networks millimeter wave (mm-wave) radio over fiber (RoF) system is a key enabling technology due to its its large bandwidth and short reach in atmosphere. In this paper, we will discuss some key technologies based on injection locked lasers for mm-wave RoF systems, including all optical generation of mm-wave signal, up- and down-conversion, single sideband modulation, and transmission.

Chen, Zhangyuan; Hu, Weiwei; Hong, Cheng; Zhang, Cheng; Li, Mingjin; Chen, Yushu; Wang, Xiang

2008-11-01

334

Centralized Lightwave Radio-Over-Fiber System With Photonic Frequency Quadrupling for High-Frequency Millimeter-Wave Generation  

Microsoft Academic Search

We have proposed a novel radio-over-fiber architecture to reduce the system cost at both central office (CO) and base station (BS). In this architecture, by incorporating the proper dc bias and optical filtering techniques in CO, the optical millimeter- wave (mm-wave) carriers are generated with four times frequency of the local oscillator signal. The BS is simplified by using the

Jianjun Yu; Zhensheng Jia; Ting Wang; Gee Kung Chang

2007-01-01

335

A hysteresis effect in the generation of field-aligned irregularities by a high-power radio wave  

Microsoft Academic Search

The anomalous self-absorption of a high-power radio wave measured during recent ionospheric modification experiments exhibits a hysteresis effect. These results are consistent with the assumption that the growth of field-aligned irregularities due to the interaction of a high-power pump wave and the ionospheric plasma occurs in two stages. During the first stage, striation growth is due to an instability which

T. B. Jones; T. Robinson; P. Stubbe; H. Kopka

1983-01-01

336

Blood-brain barrier disruption by continuous-wave radio frequency radiation.  

PubMed

The increasing use of cellular phones and the increasing number of associated base stations are becoming a widespread source of non ionizing electromagnetic radiation. Some biological effects are likely to occur even at low-level EM fields. This study was designed to investigate the effects of 900 and 1,800 MHz Continuous Wave Radio Frequency Radiation (CW RFR) on the permeability of Blood Brain Barrier (BBB) of rats. Results have shown that 20 min RFR exposure of 900 and 1,800 MHz induces an effect and increases the permeability of BBB of male rats. There was no change in female rats. The scientific evidence on RFR safety or harm remains inconclusive. More studies are needed to demonstrate the effects of RFR on the permeability of BBB and the mechanisms of that breakdown. PMID:19811403

Sirav, Bahriye; Seyhan, Nesrin

2009-01-01

337

A test for the solar cycle variability of ionospheric radio wave absorption by A_1 technique  

NASA Astrophysics Data System (ADS)

The quiet time solar cycle variability of ionospheric radio wave absorption of 2.132 MHz at Delhi is compared with the absorption calculated by using the well known aeronomical (six-ion) and empirical (IRI-1990) models of electron density profiles and standard collision frequency distributions. It is found that the observed increase of absorption in solar cycle 21/22 is by a factor of 2.5 greater than values computed with IRI. These latter are almost satisfactory for low and moderate values of the 1-8 Angstroms solar X-ray flux. Absorption and X-ray flux are well correlated for low and moderate, not so for high flux values.

Nath, N.; Abraham, S.

1996-01-01

338

Radio-wave heating of iron oxide nanoparticles can regulate plasma glucose in mice.  

PubMed

Medical applications of nanotechnology typically focus on drug delivery and biosensors. Here, we combine nanotechnology and bioengineering to demonstrate that nanoparticles can be used to remotely regulate protein production in vivo. We decorated a modified temperature-sensitive channel, TRPV1, with antibody-coated iron oxide nanoparticles that are heated in a low-frequency magnetic field. When local temperature rises, TRPV1 gates calcium to stimulate synthesis and release of bioengineered insulin driven by a Ca(2+)-sensitive promoter. Studying tumor xenografts expressing the bioengineered insulin gene, we show that exposure to radio waves stimulates insulin release from the tumors and lowers blood glucose in mice. We further show that cells can be engineered to synthesize genetically encoded ferritin nanoparticles and inducibly release insulin. These approaches provide a platform for using nanotechnology to activate cells. PMID:22556257

Stanley, Sarah A; Gagner, Jennifer E; Damanpour, Shadi; Yoshida, Mitsukuni; Dordick, Jonathan S; Friedman, Jeffrey M

2012-05-01

339

Correlation of solar radio bursts associated with electron plasma oscillations, solar particles and shock waves  

NASA Astrophysics Data System (ADS)

A model for the generation mechanism of type III solar radio bursts (SRB) was originally proposed by Ginzburg-Zhelenznyakov (1958), and consists of a two-step process. The first process causes local electron plasma oscillations at the electron plasma frequency. During the second process, these electron plasma oscillations (EPO) are converted to electromagnetic radiation. Concerning the first process, the question arises, whether all of the electron plasma oscillation events be caused by nonthermal solar flare electrons ejected directly from the sun. Correlating EPO-SRB events with solar particle and shock wave observations, the present investigation indicates that there are a considerable number of EPO-SRB events which are not correlated with low energy electrons, but some of them are correlated with interplanetary shocks and/or low energy electrons.

Kikuchi, H.; Gurnett, D. A.; Keppler, E.; Richter, A. K.; Schwenn, R.; Rosenbauer, H.

340

Measurements of Antenna Surface for Millimeter-Wave Space Radio Telescope  

NASA Astrophysics Data System (ADS)

In the construction of a space radio telescope, it is essential to use materials with a low noise factor and high mechanical robustness for the antenna surface. We present the results of measurements of the reflection performance of two candidates for antenna surface materials for use in a radio telescope installed in a new millimeter-wave astronomical satellite, ASTRO-G. To estimate the amount of degradation caused by fluctuations in the thermal environment in the projected orbit of the satellite, a thermal cycle test was carried out for two candidates, namely, copper foil carbon fiber reinforced plastic (CFRP) and aluminum-coated CFRP. At certain points during the thermal cycle test, the reflection loss of the surfaces was measured precisely by using a radiometer in the 41-45 GHz band. In both candidates, cracks appeared on the surface after the thermal cycle test, where the number density of the cracks increased as the thermal cycle progressed. The reflection loss also increased in proportion to the number density of the cracks. Nevertheless, the loss of the copper foil surface met the requirements of ASTRO-G at the end of the equivalent life, whereas that of the aluminum-coated surface exceeded the maximal value in the requirement even before the end of the cycle.

Kamegai, Kazuhisa; Tsuboi, Masato; Doi, Akihiro; Sato, Eiichi

2011-06-01

341

Angular scattering of radio waves: Implications for mode coupling in the solar corona  

NASA Astrophysics Data System (ADS)

The solar corona is highly inhomogeneous. The magnetionic modes may therefore couple under certain circumstances, and the polarization properties of solar radio sources may, as a consequence, be modified. An application of the simple theory of mode coupling to the propagation of radio waves in the solar corona leads to the expectation that mode coupling in quasi-transverse (QT) magnetic field regions should always be weak (coupling ratio Q much less than 1) at meter wavelengths. Observations to date suggest that, on the contrary, mode coupling is moderate (Q approximately 1) to strong (Q much greater than 1) in QT regions at meter wavelengths. I suggest that observations and theory can be reconciled by including the effect of turbulence on mode coupling. Specifically, angular scattering on turbulent inhomogeneities greatly reduces the spatial scale relevant to the theory at low frequencies. As a result, the coupling ratio is increased by a corresponding factor and mode coupling may be moderate to strong in QT regions at meter wavelengths.

Bastian, T. S.

1995-01-01

342

A tool to improve space weather forecasts: Kilometric radio emissions from Wind/WAVES  

NASA Astrophysics Data System (ADS)

For decades, space environment forecasters have used the appearance of metric Type II radio emission as a proxy for eruptions in the solar corona. The drift rate of these near-Sun emissions is often turned into a speed, commonly assumed to be that of an MHD shock. However, their utility to forecast shock arrival times has not proved to be conclusive. Metric emissions can be detected by ground-based antennae, while lower-frequency components of these slowly drifting emissions can also be tracked by spacecraft in interplanetary space, as far down in frequency as that of the local plasma frequency. For a spacecraft at L1, this corresponds to about 25 kHz, or an electron density of about 7 cm-3 in the ambient solar wind. Here we report a recent study that aims to improve the predictions of shock arrival time at L1 by means of the low-frequency emissions detected by WIND/WAVES. This technique, implemented on an extensive sample of hectometric and kilometric type II radio bursts, has yielded promising results.

Cremades, H.; St. Cyr, O. C.; Kaiser, M. L.

2007-08-01

343

Search for Exoplanetary Radio-Bursts in Decameter Wave Band: Statistical Enhancement of Sensitivity Under Severe Interference Conditions  

Microsoft Academic Search

Radio observations in decameter wave band are known to be subject to strong man-made interference signals that make difficult the detection of comparatively weak emissions of cosmic origin. The efficient methods of filtering out the interferences have been recently proposed that utilize the differences in characteristic time scales of the analyzed signals. Those methods, however, restrict the sensitivity of observations

V. B. Ryabov; P. Zarka; B. P. Ryabov

2003-01-01

344

Analysis of radio wave reflection and transmission characteristics at reinforced concrete slab by numerical simulation and scaled model experiment  

Microsoft Academic Search

The authors present the reflection and transmission characteristics of radio waves at the reinforced concrete (RC) slab of buildings. The purpose of this study is to formulate the reflection and transmission characteristics of RC slab at various realistic conditions, for the effective use of mobile communications systems inside and from outside to inside of buildings. The object frequencies for this

H. Chiba; Y. Miyazaki

1999-01-01

345

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

Microsoft Academic Search

In recent years, large electron temperature increases of 300% (3000 K above background) caused by powerful HF-radio wave injection have been observed during nighttime using the EISCAT incoherent scatter radar near Tromsø in northern Norway. In a case study we examine the spatial structure of the modified region. The electron heating is accompanied by ion heating of about 100 degrees

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

2003-01-01

346

Rise and fall of electron temperatures: Ohmic heating of ionospheric electrons from underdense HF radio wave pumping  

Microsoft Academic Search

Here we present electron temperature variations observed with incoherent scatter radar during a European Incoherent Scatter Scientific Association Heating experiment with high-frequency (HF) radio wave transmission at frequencies above the peak ionospheric critical frequency. The electron temperature increased from 2000 K up to 2800 K during the HF transmission periods. During the experiment both pump frequency and polarization were altered

B. Gustavsson; M. T. Rietveld; N. V. Ivchenko; M. J. Kosch

2010-01-01

347

First incoherent scatter radar observations of radio wave pumping in the ionosphere around the second electron gyroharmonic  

Microsoft Academic Search

We report results from a unique experiment performed at the HIPAS ionospheric modification facility in Alaska. High power radio waves at 2.85 MHz, which corresponds to the second electron gyroharmonic at 240 km altitude, were transmitted into the nighttime ionosphere. Diagnostics included optical equipment at HIPAS and HAARP, 288 km to the south-east, the PFISR radar at Poker Flat, 32

Michael Kosch; Bill Bristow; Bjorn Gustavsson; Craig Heinselman; John Hughes; Brett Isham; Charles Mutiso; Kim Nielsen; Todd Pedersen; Weiyuan Wang; Alfred Wong

2008-01-01

348

The Measurement of Phase and Amplitude Radio Wave Interaction at University Park, Pennsylvania, for July-August-September, 1964.  

National Technical Information Service (NTIS)

The measurement of phase and amplitude radio wave interaction, to be carried out during the IQSY, comprises the contents of this report. The interaction parameters, T sub A and T sub phi are given as a function of height for the dates and times indicated....

A. J. Ferraro H. S. Lee

1965-01-01

349

EFFECT OF CENTIMETER BAND RADIO WAVES ON THE ABSORPTION OF AMINO ACIDS, CHLORIDES AND WATER IN THE STOMACH AND INTESTINE  

Microsoft Academic Search

The absorption of amino acids, chlorides, and water was studied in the ; normal state and under the effect of high frequency of the centimeter waveband on ; 8 dogs with Pavlov pouches (3) and isolated loop of the small intestine (3 dogs). ; The effect of a 50 watt radio-wave field acting on the organism for 10 minutes on

Feitelberg-Blank

1962-01-01

350

Characteristics of dust particles detected near Saturn's ring plane with the Cassini Radio and Plasma Wave instrument  

Microsoft Academic Search

During the inbound and outbound passes of the Cassini spacecraft through Saturn's ring plane on July 1, 2004, the Radio and Plasma Wave Science (RPWS) instrument detected many small particles striking the spacecraft. When a small particle strikes the spacecraft at a high velocity, it is instantly vaporized and produces a small cloud of plasma that expands radially outward from

Z. Wang; D. A. Gurnett; T. F. Averkamp; A. M. Persoon; W. S. Kurth

2006-01-01

351

Ionospheric absorption of radio waves at midlatitudes in the winter, solar activity, geomagnetic disturbances, and atmospheric circulation  

Microsoft Academic Search

Analysis of the indices of radio-wave absorption in the ionosphere (Moscow station), as well as those of solar activity and geomagnetic disturbances during 1957-1984 reveals the complex manner in which they vary. It is found that the penetration of energetic particles fluxes into the atmosphere of the auroral zone leads to the formation of nitric oxide and the dissociation of

Z. Ts. Rapoport

1986-01-01

352

On the anomalies and role of water clusters in atmospheric absorption of millimeter and submillimeter radio waves  

Microsoft Academic Search

Experimental data are presented which do not confirm the existence of anomalies observed by many investigators in the atmospheric absorption of millimeter and submillimeter radio waves and make questionable the hypothesis on the importance of large water clusters in absorption that is invoked to explain the anomalies.

V. Yu. Katkov; N. I. Furashov

1996-01-01

353

Application of frequency and space correlation of radio wave propagation conditions for the purpose of designing satellite communications links  

Microsoft Academic Search

The present consideration of the influence of rain effect prediction methods on 10-30 GHz frequency range satellite communications links gives attention to the possible application of the frequency and space correlation of radio wave propagation on earth-satellite paths. Different evaluation methods are discussed in light of results obtained by propagation experiments conducted under the Intercosmos program. Agreement is noted to

B. Balabanov; E. Aleksandrova; V. Sviatogor; V. Bykov; A. Kavetzki

1987-01-01

354

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

355

Prediction of diffraction effects due to irregular terrain on radio wave propagation in the VHF and UHF bands  

Microsoft Academic Search

Many models have been proposed to represent diffraction effects on the propagation of radio waves over irregular terrain in the VHF and UHF bands. Predictions from these models have been compared with results from associated field-strength measurements available in extensive databases that also incorporate the technical parameters of thousands of VHF and UHF links. Some possible sources of the still

Emanoel Costa; Marco Aurelio Nunes da Silva; Markus Liniger

2011-01-01

356

A THEORY OF INCOHERENT SCATTERING OF RADIO WAVES BY A PLASMA. II. SCATTERING IN A MAGNETIC FIELD  

Microsoft Academic Search

A general expression for the frequency spectrum of radio waves scattered ; by random thermal fluctuations of electron density in a plasma in a magnetic ; field is derived. The derivation is based on the generalized Nyquist noise ; theorem. The result is simplified by an approximation assuming the velocity of ; light to be infinite. It is shown that

D.T. Farley; J. P. Dougherty; D. W. Barron

1961-01-01

357

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 ...

358

Fungicidal Effects of Plasma and Radio-Wave Pre-treatments on Seeds of Grain Crops and Legumes  

NASA Astrophysics Data System (ADS)

An influence of RF plasma and RF electromagnetic field pre-treatments on level of fungal infection of some important agricultural plants has been studied. It is shown that pre-sowing plasma and radio-wave seeds treatments contribute to their germination enhancement and plant productivity improvement owing to stimulative and fungicidal effect of plasma and RF electromagnetic field irradiation.

Filatova, Irina; Azharonok, Viktor; Shik, Alexander; Antoniuk, Alexandra; Terletskaya, Natalia

359

Quasilinear theory of electron transport by radio frequency waves and nonaxisymmetric perturbations in toroidal plasmas  

SciTech Connect

The use of radio frequency waves to generate plasma current and to modify the current profile in magnetically confined fusion devices is well documented. The current is generated by the interaction of electrons with an appropriately tailored spectrum of externally launched rf waves. In theoretical and computational studies, the interaction of rf waves with electrons is represented by a quasilinear diffusion operator. The balance, in steady state, between the quasilinear operator and the collision operator gives the modified electron distribution from which the generated current can be calculated. In this paper the relativistic operator for momentum and spatial diffusion of electrons due to rf waves and nonaxisymmetric magnetic field perturbations is derived. Relativistic treatment is necessary for the interaction of electrons with waves in the electron cyclotron range of frequencies. The spatial profile of the rf waves is treated in general so that diffusion due to localized beams is included. The nonaxisymmetric magnetic field perturbations can be due to magnetic islands as in neoclassical tearing modes. The plasma equilibrium is expressed in terms of the magnetic flux coordinates of an axisymmetric toroidal plasma. The electron motion is described by guiding center coordinates using the action-angle variables of motion in an axisymmetric toroidal equilibrium. The Lie perturbation technique is used to derive a diffusion operator which is nonsingular and time dependent. The resulting action diffusion equation describes resonant and nonresonant momentum and spatial diffusion. Momentum space diffusion leads to current generation in the plasma and spatial diffusion describes the effect of rf waves and magnetic perturbations on spatial evolution of the current profile. Depending on the symmetry of the equilibrium and the corresponding relation of the action variables to the configuration space variables, in addition to diffusion along the radial direction, poloidal, and toroidal electron diffusion, is also described. In deriving the diffusion operator, no statistical assumption, such as, the Markovian assumption, for the underlying electron dynamics, is imposed. Consequently, the operator is time dependent and valid for a dynamical phase space that is a mix of correlated regular orbits and decorrelated chaotic orbits. The diffusion operator is expressed in a form suitable for implementation in a numerical code.

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

2008-12-15

360

Modeling Ionospheric HF/VHF Radio-Wave Absorption due to Solar Energetic Proton Events  

NASA Astrophysics Data System (ADS)

Simple, one-parameter, algorithms have been applied to the observed energetic proton flux as provided by the GOES series of satellites to yield estimates of the high latitude HF and VHF radio-wave absorption for both day and night respectively. The twilight response is obtained as a bi-linear function of the solar zenith angle at the observation positions, and the latitude dependence of the absorption region near the edge of the absorbing region (the polar caps) are estimated from extant models of geomagnetic cut-offs and their dependence on geomagnetic activity. The approximate inverse square frequency dependence of ionospheric absorption is used to translate across the HF/VHF range and predictions of the minimum duration of events are determined. Calculations of the polar cap absorption of HF radio waves have been performed for eleven larger Solar Energetic Proton (SEP) events during the period from 1992 through 2002 and the results compared to observations of 30 MHz Riometers operated by the AFGL and located at Thule, Greenland. While discrepancies between the estimated and observed absorption using these procedures occur, especially at low absorption levels, this model has operational value in view of its simplicity and its being the only extant model, to our knowledge, which treats solar-illumination, geomagnetic cutoff variation, and frequency effects, at least to first order. Specimen graphical representations of the north and south polar caps illustrate the output of the model for the peak of the 12 December 2006 solar proton event. Given sufficient interest, improvements to the methodology used here are practicable and could be expected to achieve accuracies to the order of 25% or better.

Sauer, H. H.; Wilkinson, D. C.

2007-12-01

361

Monitoring, mapping and prediction of ionospheric scintillation over the Brazilian equatorial and low latitude regions  

NASA Astrophysics Data System (ADS)

It is well known, today, that equatorial ionospheric scintillations affect performance of GPS receivers. Scintillation occurs when a radio wave crosses the ionosphere and suffers distortion in phase and amplitude. It also contributes to loss of lock of GPS receivers, resulting decrease of the number of available satellites and consequently yielding poor satellite geometry. Therefore, the required accuracy and positioning precision for aerial navigation are affected. Among other activities, EMBRACE, the space weather program of INPE, is monitoring and mapping the ionospheric scintillation over the South American equatorial and low latitude region in real time. This mapping is available in the internet by means of computer programs that retrieve data from a network of GPS receivers distributed in Brazil. These data are also being used to survey and predict the occurrence of ionospheric scintillation through data mining techniques.

Becker-Guedes, Fabio; de Paula, E. R.; de Rezende, L. F. C.; Stephany, S.; Kantor, I. J.; Muella, M. T. A. H.; Siqueira, P. M.; Correa, K. S.; Dutra, A. P.; Guedes, C.; Takahashi, H.; Silva, J. D. S.

362

Applications of a travelling wave-based radio-frequency-only stacked ring ion guide.  

PubMed

The use of radio-frequency (RF)-only ion guides for efficient transport of ions through regions of a mass spectrometer where the background gas pressure is relatively high is widespread in present instrumentation. Whilst multiple collisions between ions and the background gas can be beneficial, for example in inducing fragmentation and/or decreasing the spread in ion energies, the resultant reduction of ion axial velocity can be detrimental in modes of operation where a rapidly changing influx of ions to the gas-filled ion guide needs to be reproduced at the exit. In general, the RF-only ion guides presently in use are based on multipole rod sets. Here we report investigations into a new mode of ion propulsion within an RF ion guide based on a stack of ring electrodes. Ion propulsion is produced by superimposing a voltage pulse on the confining RF of an electrode and then moving the pulse to an adjacent electrode and so on along the guide to provide a travelling voltage wave on which the ions can surf. Through appropriate choice of the travelling wave pulse height, velocity and gas pressure it will be shown that the stacked ring ion guide with the travelling wave is effective as a collision cell in a tandem mass spectrometer where fast mass scanning or switching is required, as an ion mobility separator at pressures around 0.2 mbar, as an ion delivery device for enhancement of duty cycle on an orthogonal acceleration time-of-flight (oa-TOF) mass analyser, and as an ion fragmentation device at higher wave velocities. PMID:15386629

Giles, Kevin; Pringle, Steven D; Worthington, Kenneth R; Little, David; Wildgoose, Jason L; Bateman, Robert H

2004-01-01

363

Radio wave propagation in the Martian polar deposits: models and implications for radar sounding.  

NASA Astrophysics Data System (ADS)

In the present study the propagation of electromagnetic waves in the northern polar ice sheet of Mars is considered Several different scenarios of the structure of the polar deposits and composition of the ice compatible with previously published observational data are proposed Both analytical and numerical simulations of ultra wide band chirp radar pulse propagating through the cap are performed Approximate approach based on the non-coherent theory of the radiative transfer in layered media has been applied to the problem of the propagation of radar pulses in the polar caps Both 1D and 2D and 3D geometry applicable to the orbital and landed radar instruments are studied The side clutter and phase distortions of the signal are also addressed analyzed The possibilities of retrieval of the geological information depending on transparency of the polar cap for radio waves are discussed If the polar cap is relatively transparent the echo from the base of the sheet should be clearly distinctive and interpretable in terms of basal topography of the cap In the case of moderate optical thickness coherent basal echo is corrupted by strong multiple scattering in the layered structure However some conclusions about basal conditions could be made from the signals for example the subglacial lakes may be detected Finally optically thick polar caps prevent any sounding of the base so only the medium itself can be characterized by GPR measurements e g the impurity content in the ice can be found Ilyushin Y A R Seu

Ilyushin, Ya. A.

364

Radio frequency CD by LH waves in the reversed field experiment  

NASA Astrophysics Data System (ADS)

We present a feasibility study for the active control of the poloidal current density profile in the RFX (reversed field pinch) experiment using radio frequency in the range of lower hybrid waves. The main goal of the rf current drive is to reduce the magnetic fluctuations and the magnetic stochasticity, so as to improve the energy confinement. The compelling constraints of accessibility and damping of the slow waves due to the present and extrapolated RFX plasma parameters are investigated; they have been used to fix the frequency (~1.3 GHz) and the best n? values (~8), and therefore the antenna size (Grill). A modified version of the FELICE code, which takes into account the strong shear of the magnetic field of the RFP plasmas, has been developed and used to estimate the antenna-plasma coupling: the reflected power for the proposed antenna is found to be less than 30% for a quite wide range of plasma parameters. In order to estimate the current drive profile and efficiency a one dimensional Fokker-Planck code has been used: an additional crucial contribution to the driven current is due to the enhancement of the plasma conductivity as consequence of the suprathermal electron population increase. Although the total estimated CD efficiency is promising, the rf-power required to drive the current necessary to produce a significant reduction of the magnetic fluctuations is found to be in the MW range.

Bilato, R.; Brambilla, M.

1999-09-01

365

EVIDENCE FOR THE OSCILLATING TWO STREAM INSTABILITY AND SPATIAL COLLAPSE OF LANGMUIR WAVES IN A SOLAR TYPE III RADIO BURST  

SciTech Connect

We present observational evidence for the oscillating two stream instability (OTSI) and spatial collapse of Langmuir waves in the source region of a solar type III radio burst. High time resolution observations from the STEREO A spacecraft show that Langmuir waves excited by the electron beam occur as isolated field structures with short durations {approx}3.2 ms and with high intensities exceeding the strong turbulence thresholds. These short duration events are identified as the envelope solitons which have collapsed to spatial scales of a few hundred Debye lengths. The spectra of these wave packets contain an intense peak and two sidebands, corresponding to beam-resonant Langmuir waves, and down-shifted and up-shifted daughter Langmuir waves, respectively, and low-frequency enhancements below a few hundred Hz. The frequencies and wave numbers of these spectral components satisfy the resonance conditions of the OTSI. The observed high intensities, short scale lengths, sideband spectral structures, and low-frequency enhancements strongly suggest that the OTSI and spatial collapse of Langmuir waves probably control the nonlinear beam-plasma interactions in type III radio bursts.

Thejappa, G.; Bergamo, M.; Papadopoulos, K. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); MacDowall, R. J., E-mail: thejappa.golla@nasa.gov, E-mail: mbergamo@umd.edu, E-mail: kp@astro.umd.edu, E-mail: Robert.MacDowall@nasa.gov [NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2012-03-15

366

A study of acoustic-gravity waves responsible for focusing of HF radio waves reflected from the ionsphere  

NASA Astrophysics Data System (ADS)

Acoustic-gravity waves (AGWs) cause transient curvature in the ionospheric reflector, evidenced by amplitude modulation in HF radio skywave channels. When the reflector's radius of curvature approximates the reflector's height, the modulation takes the dramatic form of sharp spikes in power. Systematic observations of such spikes in the course of a synoptic study of the midlatitude, midday, winter/spring F region during 1989 are reported. The three-dimensional velocity of the associated AGWs is inferred from a combination of (1) coherent-array correlations (for the horizontal velocity) and (2) simply recording the delay for focusing from two separate heights (for vertical velocity). The dominant propagation azimuth is toward the SE; the phase velocity vector is typically tilted down (from horizontal) by 10-30 deg; the typical three-dimensional phase speed is in the range 100 m/s. The period in the observer's frame is inferred to be around 20 min; the horizontal wavenumber is inferred to be around 0.05/km. The intrinsic period (in the frame moving with the neutral wind) is inferred to be near the buoyancy period.

Jacobson, Abram R.; Carlos, Robert C.

1990-04-01

367

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

2010-06-16

368

Observation of Beat Oscillation Generation by Coupled Waves Associated with Parametric Decay during Radio Frequency Wave Heating of a Spherical Tokamak Plasma  

SciTech Connect

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.

Nagashima, Yoshihiko; Oosako, Takuya; Takase, Yuichi; Ejiri, Akira; Watanabe, Osamu; Kobayashi, Hiroaki; Adachi, Yuuki; Yamaguchi, Takashi; Kurashina, Hiroki; Yamada, Kotaro; Hayashi, Hiroyuki; Matsuzawa, Haduki; Hanashima, Kentaro; Sakamoto, Takuya [Graduate School of Frontier Sciences, University of Tokyo, Kashiwa-shi, Chiba 277-8561 (Japan); Tojo, Hiroshi [Naka Fusion Institute, Japan Atomic Energy Agency, Naka-shi, Ibaraki 311-0193 (Japan); An, Byung Il; Hiratsuka, Junichi; Kakuda, Hidetoshi; Wakatsuki, Takuma [Graduate School of Science, University of Tokyo, Kashiwa-shi, Chiba 277-8561 (Japan); Kasahara, Hiroshi [National Institute for Fusion Science, Toki-shi, Gifu 509-5292 (Japan)

2010-06-18

369

Update on Local Time and Radial Dependence of HOM/DAM Radio Emission Observed by the Galileo Plasma Wave Instrument  

NASA Astrophysics Data System (ADS)

We have previously reported on the local time and radial dependence of HOM/DAM radio emission observed by the plasma wave instrument on board the Galileo spacecraft. The original study covered portions of the first 17 orbits of the spacecraft, but the early morning and afternoon sectors of local time were observed at much smaller radial distances than the other local time quadrants. In the present study we have compiled data from the extended mission to present a much more comprehensive picture of the radio emission power levels and occurrence probabilities. We will discuss these findings in light of our current knowledge of the Jovian magnetosphere.

Menietti, J. D.; Gurnett, D. A.; Groene, J. B.; Kurth, W. S.

2002-12-01

370

VHF Interferometry System for Detecting Anomalous Propagation of FM Radio Broadcasting Wave Related to Earthquake and its Preliminary Result  

NASA Astrophysics Data System (ADS)

Earthquake-related anomalous electromagnetic phenomena have been reported in various frequency ranges in a few decades. Investigation on the anomalous propagation of VHF transmitter waves is one of promising approaches on the short-term prediction and crustal activity monitoring. The anomalous propagation is considered to be generated by disturbances of the atmosphere above the epicenter or along the propagation path prior to large earthquakes. Consequently, over-horizontal propagation has been received. A recent study shows that the appearance of anomalies was significantly enhanced within 5 days before earthquakes with M ? 4.8. However, there is no information on the scattered place, that is, the direction of wave arrival. Therefore, a simple interferometer system for VHF radio wave to identify the position between space-time of earthquake-related atmospheric disturbances has been developed and installed at Chiba University. In this paper, we will show you the developed interferometer system and results of fundamental tests to evaluate the performance of developed and installed interferometer at Chiba. In addition, facts on invisible propagation of VHF radio wave obtained from 1-year continuous measurement at Chiba are described in this paper. Those are possible radio duct propagations and possible earthquake-related anomalous propagations.

Ohno, Nozomi; Tone, Yuka; Hattori, Katsumi; Yamamoto, Isao; Shimakura, Shin; Takano, Toshiaki

371

Global estimates of gravity wave parameters from GPS radio occultation temperature data  

NASA Astrophysics Data System (ADS)

Gravity waves (GWs) play critical roles in the global circulation and the temperature and constituent structures in the middle atmosphere. They also play significant roles in the dynamics and transport and mixing processes in the upper troposphere and lower stratosphere and can affect tropospheric weather. Despite significant advances in our understanding of GWS and their effects in different regions of the atmosphere in the past few decades, observational constraints on GW parameters including momentum flux and propagation direction are still sorely lacking. Global Positioning System (GPS) radio occultation (RO) technique provides global, all-weather, high vertical resolution temperature profiles in the stratosphere and troposphere. The unprecedentedly large number of combined temperature soundings from the Constellation Observing System for Meteorology, Ionosphere, and Climate and Challenging Minisatellite Payload GPS RO missions allows us to obtain GW perturbations by removing the gravest zonal modes using the wavelet method for each day. We extended the GW analysis method of Alexander et al. (2008) to three dimensions to estimate the complete set of GW parameters (including momentum flux and horizontal propagation direction) from the GW temperature perturbations thus derived. To demonstrate the effectiveness of the analysis, we showed global estimates of GW temperature amplitudes, vertical and horizontal wavelengths, intrinsic frequency, and vertical flux of horizontal momentum in the altitude range of 17.5-22.5 km during December 2006 to February 2007. Consistent with many previous studies, GW temperature amplitudes are a maximum in the tropics and are generally larger over land, likely reflecting convection and topography as main GW sources. GW vertical wavelengths are a minimum at equator, likely due to wave refraction, whereas GW horizontal wavelengths are generally longer in the tropics. Most of the waves captured in the analysis of the GPS data are low-intrinsic frequency inertia-GWs, and the estimated intrinsic frequencies scaled by the Coriolis parameter also show a strong maximum at equator. Enhanced wave fluxes are linked to convection, topography, and storm tracks, among others. As preliminary tests of the analysis in deriving horizontal propagation directions, we compared the GPS estimates with the corresponding estimates from the U.S. high vertical resolution radiosonde data using the conventional Stokes parameters method and we also conducted a separate analysis of the GPS data over the southern Andes in South America. We also showed the first global estimates of GW propagation directions from the GPS data. Finally, the sensitivity of the analysis to the temporal and spatial dimensions of the longitude × latitude × time cells and the uncertainties of the analysis and possible ways to reduce these uncertainties are discussed.

Wang, L.; Alexander, M. J.

2010-11-01

372

Hyperactive Chipmunk Radio  

Microsoft Academic Search

The hyperactive chipmunk radio modulates voice signals so that the radio waves behave the same in the radio medium as sound waves normally do in the acoustic medium. This is accomplished by segmenting the voice signal and compressing the segments in time before transmitting them through the radio channel. If the compression factor is correct, the distortion characteristics of the

G. H. McGibney; S. T. Nichols

373

Radio-frequency spectroscopy of {sup 6}Li p-wave molecules: Towards photoemission spectroscopy of a p-wave superfluid  

SciTech Connect

We study rf spectroscopy of a lithium gas with the goal to explore the possibilities for photoemission spectroscopy of a strongly interacting p-wave Fermi gas. Radio-frequency spectra of quasibound p-wave molecules and of free atoms in the vicinity of the p-wave Feshbach resonance located at 159.15 G are presented. The spectra are free of detrimental final-state effects. The observed relative magnetic-field shifts of the molecular and atomic resonances confirm earlier measurements realized with direct rf association. Furthermore, evidence of molecule production by adiabatically ramping the magnetic field is observed. Finally, we propose the use of a one-dimensional optical lattice to study anisotropic superfluid gaps as most direct proof of p-wave superfluidity.

Maier, R. A. W.; Marzok, C.; Zimmermann, C.; Courteille, Ph. W. [Physikalisches Institut, Eberhard Karls Universitaet Tuebingen, Auf der Morgenstelle 14, D-72076 Tuebingen (Germany); Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, Caixa Postal 369, Sao Carlos-SP 13560-970 (Brazil)

2010-06-15

374

Forecasting scintillations, the CNOFS satellite challenge  

NASA Astrophysics Data System (ADS)

This paper describes the science issues associated with the Communication / Navigation Outage Forecasting System (C/NOFS) Mission of the Air Force Research Laboratory. The primary purpose of C/NOFS is to forecast ionospheric irregularities that adversely impact communication and navigation systems. A satellite, scheduled for launch in January 2004 into a low inclination (13^o), elliptical (˜400 × 700 km) orbit, is the main component of the C/NOFS Mission. Complementary ground-based measurements are also part of the Mission. Difficulties in predicting the presence of scintillation-producing irregularities may be organized into three categories: (1) understand physical processes active in the background ionosphere and thermosphere, in order to nowcast and forecast the equatorial ionosphere; (2) identify mechanisms that trigger or quench the plasma irregularities; and (3) determine how irregularity spectra evolve. C/NOFS is the first satellite solely dedicated to forecasting ionospheric irregularities and radio wave scintillations. Its sensors will measure the following parameters: ambient and fluctuating electron densities; ion and electron temperatures; AC and DC electric fields; magnetic fields; neutral winds; ionospheric scintillations; and electron content along the lines of sight between the C/NOFS and GPS satellites. Forecasting will be based on both ground and space data. Significant international participation in pursuing C/NOFS science goals is desired and anticipated.

de La Beaujardiere, O.; Retterer, J.; Groves, K.; Burke, W.; Rich, F.; Basu, B.; Decker, D.; Jeong, L.

2003-04-01

375

Characteristics of small-scale ionospheric irregularities as deduced from scintillation observations of radio signals from satellites ETS-2 and Polar Bear 4 at Irkutsk  

NASA Astrophysics Data System (ADS)

This paper presents some new results on the small-scale inhomogeneous ionospheric structure obtained at a facility for spaced-antenna reception of transionospheric signals from ETS-2 and Polar Bear 4 near Irkutsk (Eastern Siberia, 52 deg N, 104 deg E). A technique based on transferring time spectra of scintillations to spatial spectra using measured horizontal irregularity drift velocities is used to obtain an estimate of the mean spatial spectrum of midlatitude scintillations. Two different methods were used to determine the inclination index of the scintillation spectrum, which was found to be equal to -2, in agreement with the value recently predicted for small-scale F region irregularities generated through mapping of small-scale, turbulent electric fields from the E region to the F region. Drift velocities of the diffraction pattern, and also the altitudes at which ionospheric irregularities are located, agree well with results obtained by other authors for midlatitudes. Using simultaneous measurements for a geostationary satellite and an orbiting satellite, the supposition about the existence of the southern boundary of the scintillation region has been confirmed. Finally, analysis of quasi-periodic (QP) scintillations and simultaneously determined diffraction pattern velocities is used to show that the height of isolated irregularities giving rise to QP scintillations corresponds to the maximum of the ionospheric F2 region.

Afraimovich, E. L.; Zherebtsov, G. A.; Zvezdin, V. N.; Franke, S. J.

1994-07-01

376

Atmospherics in relation to source phenomena and radio wave propagation in the VHF, UHF, microwave and millimetre wave bands  

Microsoft Academic Search

Atmospherics originating from lightning flashes have been extensively studied by radio scientists for the last several decades, with a view to assessing and predicting the interfering effect on radio communication systems. Most of the earlier studies were confined to frequencies below about 30 MHz where ionospheric propagation can be exploited. The advent of satellite communication for a global coverage has,

A. K. Sen; M. K. Das Gupta

1987-01-01

377

Comparing the H-alpha Intensity and Radio Wave Scattering on Eight Low-Latitude Lines of Sight  

Microsoft Academic Search

Spangler and Reynolds compared H-alpha intensities, measured using the Wisconsin Fabry-Perot interferometer, with radio-wave scattering sizes of eight extragalactic sources along low-latitiude lines of sight. They find that some correlation exists between scattering and H-alpha intensity, as one might expect. However, the H-alpha observations were made with a 50(') beam size; higher resolution observations might provide a more accurate measure

J. H. Simonetti; B. Dennison; G. A. Topasna

1995-01-01

378

Analysis of Atmospheric and Ionospheric Wave Structures Using the CHAMP and GPS\\/MET Radio Occultation Database  

Microsoft Academic Search

In this paper new directions of application of GPS radio occultation (RO) method are presented: (1) measuring the vertical\\u000a gradients of the refractivity in the atmosphere and electron density in the lower ionosphere, (2) study of the ionospheric\\u000a disturbances on a global scale, (3) investigation of the internal wave activity in the atmosphere. New directions may be informative\\u000a for investigations

A. G. Pavelyev; J. Wickert; Y. A. Liou; A. A. Pavelyev; C. Jacobi

379

Simultaneous observations of radio wave phase and intensity variations for locating the plasma layers in the ionosphere  

Microsoft Academic Search

A new method is introduced to locate the layered structures in the ionosphere based on simultaneous observations of radio wave temporal intensity and phase variations in trans-ionospheric satellite-to-satellite links. The method determines location of the tangent point on the trans-ionospheric ray trajectory where gradient of refractivity is perpendicular to the ray trajectory and the influence of a layered structure on

Y. A. Liou; A. G. Pavelyev

2006-01-01

380

Radio data and a theoretical model for the fast-mode MHD shock wave generated by the solar flare of 1973 September 5, 18:26 UT  

Microsoft Academic Search

Data on the solar radio burst of spectral type II generated by the solar flare of 1973 September 5, 18:26 UT are analyzed, and the radial velocity of the shock wave that gave rise to the radio burst is estimated at about 1100 km s⁻¹. This estimate is critically dependent on the model assumed for electron density above the flare

M. Dryer; A. Maxwell

1979-01-01

381

Radio wave scattering observations of the solar corona: First-order measurements of expansion velocity and turbulence spectrum using Viking and Mariner 10 spacecraft  

Microsoft Academic Search

Solar conjunction of Mars on 1976 November 25 occurred very near the beginning of solar cycle 21, about 4 months after the first Viking spacecraft arrived at the planet. Radio wave scattering data were collected at 3.6 and 13 cm wavelengths, using the radio link between the Viking orbiters and the Earth. These data allow measurements of solar wind properties

G. L. Tyler; J. F. Vesecky; M. A. Plume; H. T. Howard; A. Barnes

1981-01-01

382

Radio wave scattering observations of the solar corona First-order measurements of expansion velocity and turbulence spectrum using Viking and Mariner 10 spacecraft  

Microsoft Academic Search

Radio wave scattering data were collected at 3.6 and 13 cm wavelengths by means of the radio link between the Viking orbiters and the earth during the Nov. 25, 1976 solar conjunction of Mars, which occurred near the beginning of solar cycle 21; Mariner 10 solar activity observations during 1974 are also used. It is found that the temporal frequency

G. L. Tyler; J. F. Vesecky; M. A. Plume; H. T. Howard; A. Barnes

1981-01-01

383

Radio imaging of layers and investigation of the internal atmospheric waves by use of high-stable signals of navigational satellites  

Microsoft Academic Search

An essential connection between the eikonal acceleration and intensity of radio waves has been established under assumption of local spherical symmetry. This connection is similar to the well known classical dynamics equation. Application of this relationship to analysis of experi-mental radio occultation data obtained during CHAMP and FORMOSAT-3 missions revealed that the second derivative of the eikonal with respect to

Alexander Pavelyev; Yuei An Liou; Vladimir Gubenko; Kefei Zhang; Yuriy Kuleshov

2010-01-01

384

Type III Radio Bursts at Long Wavelengths: STEREO/Waves Observations and Future Prospects for Inner Heliospheric Missions  

NASA Astrophysics Data System (ADS)

We investigate solar type III radio bursts observed by the S/Waves instruments on-board the STEREO spacecraft. These instruments provides us with goniopolarimetric (GP, also referred to as direction-finding) measurements between 125 kHz and 1975 kHz while amplitudes of electric field fluctuations are recorded up to 16 MHz. We have investigated large number of type III radio bursts from May 2007 till July 2010. Some of them have been associated with solar flares within the NOAA directory of active regions. That allows us to determine a source position of bursts when the electron density model of LeBlanc et al. (1998) has been considered. We have also located a region of type III radio bursts by triangulating the position using GP measurements. Observed type III radio bursts generally propagate in the solar equatorial plane. Our results indicate that the maximum flux density occurs at ~ 800 kHz. Future solar missions (e.g., Solar Orbiter and Solar Probe Plus) will provide new insights into properties of type III radio bursts as for instance sampling the region where this latter maximum occurs.

Krupar, V.; Santolik, O.; Maksimovic, M.; Cecconi, B.

2011-12-01

385

Io-Jupiter interaction as deduced from radio observations at the Nançay decameter array : Alfvèn wave and slow shock  

NASA Astrophysics Data System (ADS)

It is now known that the Io-Jupiter electrodynamic interaction results in electron precipitation and thus electromagnetic emissions near the footprints of the Io flux tube (IFT), but the detailed process of electron acceleration is not known. Due to the finite propagation time required to transport energy from low to high latitudes, and to the fact that the magnetosphere rotates faster than Io's orbital motion, the location of sources of electromagnetic emissions "lead" the instantaneous IFT by several degrees or even tens of degrees for decameter (DAM) radio emissions from the northern hemisphere. This lead angle and its variations thus contain important information on the physics of the Io-Jupiter interaction. We present the first analysis of the Nançay catalog of ~8 years of DAM observations, and derive from the maximum frequency variations of the observed radio emissions the lead angle and its variations as a function of longitude. Comparison to theoretical lead angle predictions using the best available plasma and magnetic field models allow us to identify two distinct types of Io-Jupiter radio emissions: one is linked to Alfvèn waves accelerating electrons to several keV which produce the intense radio "arcs" as well as the UV and IR spots observed near the IFT footprints ; the other - new - one, is attributed to a slow shock excited by a plasma pressure pulse at Io which ultimatey accelerates electrons to about 1 keV and produces the faint radio, UV and IR "trails" observed following the main intense emissions. This interpretation solves a long-standing controversy between radio observations and Jovian magnetic field models, as well as between radio and UV/IR observations. It sets strong constraints on Jovian magnetic field models that can be used to improve them.

Zarka, P.; Langmayr, D.; Gerbault, A.

2003-04-01

386

Probability Distribution of Irradiance Scintillation.  

National Technical Information Service (NTIS)

We calculated the probability distribution function (PDF) from simulations. The simulations were of an initially spherical wave propagated through homogeneous atmospheric turbulence. The onset of strong scintillation was calculated. The simulations' PDFs ...

R. J. Hill R. G. Frehlich W. D. Otto

1997-01-01

387

The effects of modification of a high-latitude ionosphere by high-power HF radio waves. Part 1. Results of multi-instrument ground-based observations  

Microsoft Academic Search

We present the results of multi-instrument experiments related to studying the phenomena in the high-latitude ionosphere affected by high-power radio waves using the EISCAT technical facilities. It was found for the first time that strong small-scale artificial field-aligned irregularities (AFAIs) are excited when the ionospheric F region is heated by a high-power HF radio wave with X-mode polarization near the

N. F. Blagoveshchenskaya; F. T. D. Borisova; T. K. Yeoman; M. T. Rietveld

2011-01-01

388

The effects of modification of a high-latitude ionosphere by high-power HF radio waves. Part 1. Results of multi-instrument ground-based observations  

Microsoft Academic Search

We present the results of multi-instrument experiments related to studying the phenomena in the high-latitude ionosphere affected\\u000a by high-power radio waves using the EISCAT technical facilities. It was found for the first time that strong small-scale artificial\\u000a field-aligned irregularities (AFAIs) are excited when the ionospheric F region is heated by a high-power HF radio wave with X-mode polarization near the

N. F. Blagoveshchenskaya; f T. D. Borisova; T. K. Yeoman; M. T. Rietveld

2011-01-01

389

A Study of the Effect of Very High Voltage 345kV T\\/L on Broadcasting Radio Wave and Human Body  

Microsoft Academic Search

We centrally study effect of very high voltage 345 kV T\\/L which is set up at residential area (Yangyang Donghae in Gangwon-do) to broadcasting radio wave and human body. First, to compare predicted result of radio wave disturbance, we set 7 areas 13 point and divide broadcasting quality, electric and magnetic fields in T\\/L process. Result of estimation, we confirm

Hwang-bin Yim; Nam-gyu Ko

2008-01-01

390

F Layer Scintillations and the Aurora.  

National Technical Information Service (NTIS)

Defense Meteorological Satellite Program photographs of the aurora are correlated with the scintillation of radio signals from both low-altitude and synchronous satellites. Measurements from several stations ranging from subauroral to auroral locations sh...

E. Martin J. Aarons

1975-01-01

391

Experimental Studies of the Effects Observed During the Nonlinear Interaction of Two High-Power Radio Waves in a Magnetoplasma  

NASA Astrophysics Data System (ADS)

We present the results of experiments on modification of the ionospheric F region by two high-power (Peff ? 20 MW) O-mode electromagnetic waves. The experiments were performed at the “Sura” heating facility of the Radiophysical Research Institute (Nizhny Novgorod, Russia) in May 23 27, 1993 at the pump frequencies near the 4th, 5th, or 6th harmonics of the electron gyrofrequency. Ionospheric perturbations were diagnosed by measuring the stationary spectral characteristics of the stimulated electromagnetic emission (SEE) of the ionospheric plasma. We determine the features of variation in the spectral characteristics of particular SEE components during the simultaneous heating of the ionospheric plasma by two radio waves in comparison with the case of a monochromatic pump wave. We observed the effect of enhanced generation of the broad up-shifted maximum (BUM) by the higher-frequency pump wave. This is accompanied by strong suppression of the BUM induced by the lower-frequency pump wave. It is shown that the effects observed during the two-frequency heating of the ionosphere have well pronounced gyroharmonic properties, i.e., depend on both the electron-gyroharmonic number and the frequency detuning of the pump waves from a harmonic of the electron gyrofrequency. We also pointed out that a change in the properties of artificial small-scale ionospheric irregularities (striations) excited by high-power radio waves is not the cause of a change in the properties of the down-shifted maximum and the BUM during the two-frequency modification of the ionospheric plasma. Ways for the further development of these studies are discussed.

Frolov, V. L.; Sergeev, E. N.; Thide, B.; Shorokhova, E. A.

2005-02-01

392

Nanotube radio.  

PubMed

We have constructed a fully functional, fully integrated radio receiver from a single carbon nanotube. The nanotube serves simultaneously as all essential components of a radio: antenna, tunable band-pass filter, amplifier, and demodulator. A direct current voltage source, as supplied by a battery, powers the radio. Using carrier waves in the commercially relevant 40-400 MHz range and both frequency and amplitude modulation techniques, we demonstrate successful music and voice reception. PMID:17973438

Jensen, K; Weldon, J; Garcia, H; Zettl, A

2007-10-31

393

A gravity waves study close to the Andes mountains in Patagonia and Antarctica with GPS radio occultation observations  

NASA Astrophysics Data System (ADS)

We first study the seasonal and geographical behavior of gravity wave activity in the lower stratosphere over the southernmost Andes mountains and their prolongation in the Antarctic Peninsula by global positioning system (GPS) radio occultation (RO) temperature profiles, obtained between years 2002 and 2005 by the CHAllenging Minisatellite Payload (CHAMP) mission. The observed features complement observations in the same zone by other satellite passive remote sensing instruments, which are able to detect different height regions and other spectral intervals of the wave spectrum. Comparisons with previous GPS RO studies in smaller areas than the one covered in our analysis are also established. Significant seasonal variation of wave activity is observed in our work, in agreement with results from other instruments. The locations of significant cases indicate that topography is an important source. Some strong wave activity is also found over open ocean. Critical level filtering is shown to have an attenuation effect, implying that a large fraction of the observed activity can be considered to be an outcome of mountain waves. The studied region has a significant advantage as compared to other regions of our planet: it generates wavefronts nearly aligned with the North-South direction (almost parallel to the mountains), whereby this geometry favors the wave detection by the nearly meridional line of sight characterizing most of the GPS RO observations used. A distribution of the observed gravity waves in terms of amplitudes and wavelengths is also presented.

Alexander, P.; Luna, D.; Llamedo, P.; de La Torre, A.

2010-02-01

394

Waves in the Mesosphere of Venus as seen by the Venus Express Radio Science Experiment VeRa  

NASA Astrophysics Data System (ADS)

The Venus Express Radio Science Experiment (VeRa) has retrieved more than 700 profiles of the mesosphere and troposphere of Venus. These profiles cover a wide range of latitudes and local times, enabling study of atmospheric wave phenomena over a range spatial scales at altitudes of 40-90 km. In addition to quasi-horizontal waves and eddies on near planetary scales, diurnally forced eddies and thermal tides, small-scale gravity waves, and turbulence play a significant role in the development and maintenance of atmospheric super-rotation. Small-scale temperature variations with vertical wavelengths of 4 km or less have wave amplitudes reaching TBD km in the stable atmosphere above the tropopause, in contrast with much weaker temperature perturbations observed in the middle cloud layer below. The strength of gravity waves increases with latitude in both hemispheres. The results suggest that convection at low latitudes and topographical forcing at high northern latitudes—possibly in combination with convection and/or Kelvin-Helmholtz instabilities—play key roles in the genesis of gravity waves. Further, thermal tides also play an important role in the mesosphere. Diurnal and semi-diurnal wave modes are observed at different latitudes and altitudes. The latitudinal and height dependence of the thermal tide modes will be investigated.

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

2013-10-01

395

Identification and radio vision of the vertical structure of the layers and wave activity in the atmoshere  

NASA Astrophysics Data System (ADS)

Identification and radio vision of the vertical structure of the layers and wave activity in the atmosphere Alexander Pavelyev, Vladimir Gubenko Institute of Radio Engineering and Electronics, Russian Academy of Sciences, Fryazino, Russia Kefei Zhang, Erjiang Fu and Chuan-Sheng Wang School of Mathematical and Geospatial Sciences, RMIT University, Melbourne, Australia Yuei-An Liou Center for Space and Remote Sensing Research (CSRSR), National Central University, Jhongli, Taiwan Yuriy Kuleshov National Climate Centre, Bureau of Meteorology, Melbourne, Australia From an analysis of the CHAMP (Challenging Minisatellite Payload, Germany) and the FORMOSAT-3/COSMIC (FORMOSA Satellite Constellation Observing Systems for Meteorology, Ionosphere, and Climate mission, USA -Taiwan) satellite data it follows that the second-order time derivative of the eikonal (eikonal acceleration) and the Doppler frequency shift are two most important parameters indispensable for the radio vision of layers in the atmosphere and the ionosphere. Measurements of the temporal evolution of the Doppler shift permit one to study the vertical structure of the atmosphere under the condition of its spherical symmetry. Analysis of the amplitude and phase of interrelated variations in the eikonal acceleration and radio-wave intensity permits one to detect and identify the layers in the atmosphere and ionosphere. Therefore the eikonal acceleration/intensity technique can be applied to separate the influence of layered structures from contributions of irregularities and turbulence in the atmosphere. In many cases the layered structures in the atmosphere indicate quasi-periodical altitude dependence that reveals their wave origin. The altitude profile of the vertical gradient of refractivity in the layered structures can be used to find the main characteristics of the internal wave activity with a global coverage. When the type of internal waves are not known, the height dependence of the vertical gradient of refractivity can be applied for monitoring the temporal and spatial distributions of wave activity at different levels in the atmosphere. In the case of the internal gravity waves one can measure their important parameters by use of the vertical profile of the refractivity: the intrinsic phase speed, the horizontal wind perturbations and, under some assumptions, the intrinsic frequency as functions of height in the atmosphere. Advantages of the eikonal acceleration/intensity technique are validated by means of analysis of the CHAMP and FORMOSAT-3/COSMIC RO data. Eikonal variations may be converted into refraction attenuation variations, which allows the integral absorption to be determined with the refraction effect on the radio-wave intensity cancelled out. This is necessary for measurements of the water-vapor density and gas minorities during multifrequency radio-occultation sounding along the satellite-to-satellite paths. The obtained results can be of common value for other remote-sounding paths, as well.

Alexander, Pavelyev; Kefei, Zhang; Vladimir, Gubenko; Erjiang, Fu; Chuan-Sheng, Wang; Yuei-An, Liou; Yuriy, Kuleshov

2010-05-01

396

Measurements of stray antenna capacitance in the STEREO/WAVES instrument: Comparison of the radio frequency voltage spectrum with models of the galactic nonthermal continuum spectrum  

NASA Astrophysics Data System (ADS)

The STEREO/WAVES instrument is designed to measure interplanetary radio emission and in situ plasma waves in the solar wind. The instrument uses three orthogonal monopole electric antennas as its sensor system in both a pseudodipole and monopole mode. At high radio frequencies, the capacitance of the antennas determines the system gain. Here we estimate the stray capacitance in the antenna system by comparing the measured voltage spectrum with a model of the galactic continuum spectrum, which is the instrument background at high frequencies. Together with the antenna free-space capacitance, these measurements provide an absolute calibration of the STEREO/WAVES experiment at radio frequencies, a prerequisite for quantitative studies of solar and astrophysical radio emission.

Eastwood, J. P.; Bale, S. D.; Maksimovic, M.; Zouganelis, I.; Goetz, K.; Kaiser, M. L.; Bougeret, J.-L.

2009-08-01

397

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

398

Making Radio Waves: Tune in to These Tips for Getting Your Campus News on the Air.  

ERIC Educational Resources Information Center

|Radio is a relatively simple and effective way to make campus news and information available to the public. Establishing a college radio news service is not difficult, and developing a sound-bite service requires little equipment or expertise, just careful attention to quality and technique. More sophisticated systems can be developed easily.…

Stubbee, Melinda

1993-01-01

399

Radio-Wave Propagation Into Large Building Structures—Part 1: CW Signal Attenuation and Variability  

Microsoft Academic Search

We report on our investigation into radio communications problems faced by emergency responders in disaster situations. A fundamental challenge to communications into and out of large buildings is the strong attenuation of radio signals caused by losses and scattering in the building materials and structure. Another challenge is the large signal variability that occurs throughout these large structures. We designed

William F. Young; Christopher L. Holloway; Galen Koepke; Dennis Camell; Yann Becquet; Kate A. Remley

2010-01-01

400

Radio wave propagation characteristics in lossy circular waveguides such as tunnels, mine shafts, and boreholes  

Microsoft Academic Search

We present the characteristics of radio propagation in a circular lossy waveguide whose walls are composed of earth soil materials with frequency-dependent properties. This type of structure is used to represent a radio link for an underground wireless communication channel such as a tunnel, mine shaft, or borehole. We present calculated results of the attenuation constant for various propagation modes

Christopher L. Holloway; David A. Hill; Roger A. Dalke; George A. Hufford

2000-01-01

401

Radio wave propagation measurements for land-mobile satellite systems at 2.33 GHz  

Microsoft Academic Search

The performance of a mobile satellite communications link is dominated by roadside attenuation due to vegetation or manmade structures. Previous measurement campaigns characterized land-mobile satellite channels at UHF and L bands. In 1997, the FCC allocated S-band spectrum to the Digital Audio Radio Satellite (DARS) service to provide nationwide radio services to the North American continent via satellite. This article

L. Mousselon; R. M. Barts; S. Licul; G. Joshi

2003-01-01

402

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

SciTech Connect

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

Eastwood, J. P.; Hudson, H. S.; Krucker, S.; Bale, S. D. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Wheatland, M. S. [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006 (Australia); Maksimovic, M.; Bougeret, J.-L. [LESIA, Observatoire de Paris, F-92195 Meudon (France); Goetz, K. [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States)], E-mail: eastwood@ssl.berkeley.edu

2010-01-10

403

Scintillator material  

DOEpatents

An improved scintillator material comprising cerium fluoride is disclosed. Cerium fluoride has been found to provide a balance of good stopping power, high light yield and short decay constant that is superior to known scintillator materials such as thallium-doped sodium iodide, barium fluoride and bismuth germanate. As a result, cerium fluoride is favorably suited for use as a scintillator material in positron emission tomography. 4 figs.

Anderson, D.F.; Kross, B.J.

1994-06-07

404

Scintillator material  

DOEpatents

An improved scintillator material comprising cerium fluoride is disclosed. Cerium fluoride has been found to provide a balance of good stopping power, high light yield and short decay constant that is superior to known scintillator materials such as thallium-doped sodium iodide, barium fluoride and bismuth germanate. As a result, cerium fluoride is favorably suited for use as a scintillator material in positron emission tomography.

Anderson, David F. (Batavia, IL); Kross, Brian J. (Aurora, IL)

1992-01-01

405

Scintillator material  

DOEpatents

An improved scintillator material comprising cerium fluoride is disclosed. Cerium fluoride has been found to provide a balance of good stopping power, high light yield and short decay constant that is superior to known scintillator materials such as thallium-doped sodium iodide, barium fluoride and bismuth germanate. As a result, cerium fluoride is favorably suited for use as a scintillator material in positron emission tomography.

Anderson, David F. (Batavia, IL); Kross, Brian J. (Aurora, IL)

1994-01-01

406

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

NASA Astrophysics Data System (ADS)

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 are also mentioned as important errors which can influence the angle of arrival and direct ranging. Ionospheric range errors are defined in terms of first-order and higher-order errors including the second-order refraction error, and the pulse-travel-time delay is mentioned. The parameters required to estimate ionospheric errors include slant electron content, and mean ionospheric height, and the second-order errors require knowledge of the vertical electron content, the equivalent slant thickness, the height of the F-layer peak, and the shape factor.

Leitinger, R.

407

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

408

Annular beam scintillations in strong turbulence.  

PubMed

A scintillation index formulation for annular beams in strong turbulence is developed that is also valid in moderate and weak turbulence. In our derivation, a modified Rytov solution is employed to obtain the small-scale and large-scale scintillation indices of annular beams by utilizing the amplitude spatial filtering of the atmospheric spectrum. Our solution yields only the on-axis scintillation index for the annular beam and correctly reduces to the existing strong turbulence results for the Gaussian beam--thus plane and spherical wave scintillation indices--and also correctly yields the existing weak turbulence annular beam scintillations. Compared to collimated Gaussian beam, plane, and spherical wave scintillations, collimated annular beams seem to be advantageous in the weak regime but lose this advantage in strongly turbulent atmosphere. It is observed that the contribution of annular beam scintillations comes mainly from the small-scale effects. At a fixed primary beam size, the scintillations of thinner collimated annular beams compared to thicker collimated annular beams are smaller in moderate turbulence but larger in strong turbulence; however, thinner annular beams of finite focal length have a smaller scintillation index than the thicker annular beams in strong turbulence. Decrease in the focal length decreases the annular beam scintillations in strong turbulence. Examining constant area annular beams, smaller primary sized annular structures have larger scintillations in moderate but smaller scintillations in strong turbulence. PMID:20686588

Gerçekcio?lu, Hamza; Baykal, Yahya; Nakibo?lu, Cem

2010-08-01

409

What is Radio Astronomy?  

NSDL National Science Digital Library

This website contains information on radio astronomy, the NRAO, how telescopes work, the history and discovery of radio astronomy, and the radio communication process. This website has activites like "Make your own Radio Image", and visual aids on topics such as: free-free emission, spectral lines, synchrotron emission, masers, and how radio communication works. The site is also a resource for blackbody radiation, the Cosmic Microwave Backround, and the mechanisms of radio wave emission.

2004-07-14

410

Scintillation Counters  

NASA Astrophysics Data System (ADS)

Scintillators find wide use in radiation detection as the detecting medium for gamma/X-rays, and charged and neutral particles. Since the first notice in 1895 by Roentgen of the production of light by X-rays on a barium platinocyanide screen, and Thomas Edison's work over the following 2 years resulting in the discovery of calcium tungstate as a superior fluoroscopy screen, much research and experimentation have been undertaken to discover and elucidate the properties of new scintillators. Scintillators with high density and high atomic number are prized for the detection of gamma rays above 1 MeV; lower atomic number, lower-density materials find use for detecting beta particles and heavy charged particles; hydrogenous scintillators find use in fast-neutron detection; and boron-, lithium-, and gadolinium-containing scintillators are used for slow-neutron detection. This chapter provides the practitioner with an overview of the general characteristics of scintillators, including the variation of probability of interaction with density and atomic number, the characteristics of the light pulse, a list and characteristics of commonly available scintillators and their approximate cost, and recommendations regarding the choice of material for a few specific applications. This chapter does not pretend to present an exhaustive list of scintillators and applications.

Bell, Zane W.

411

A good prospect for broadband millimeter-wave fiber-radio access system-an approach to single optical component at antenna base station  

Microsoft Academic Search

To realize low-cost antenna base station (BS) of the millimeter-wave (mm-wave) fiber-radio access systems, an approach to a single optical component at the BS is presented by introducing 60-GHz-band electroabsorption transceiver (EAT). By using an EAT the full-duplex 60-GHz mm-wave 156-Mb\\/s access system and optical add-drop multiplexing of WDM ring network will be discussed

K.-I. Kitayama; T. Kuri; R. Heinzelmann; A. Stohr; D. Jager; Y. Takahashi

2000-01-01

412

Studies on the Effect of Radio-Frequency Waves in Biological Macromolecules.  

National Technical Information Service (NTIS)

The effect of radio-frequency electric fields on various biologic materials was examined. Particularly, the effects on alcohol dehydrogenase and DNA were carefully investigated. To avoid the effects of heating, a pulsed electric field was used, and sample...

S. Takashima

1965-01-01

413

Attenuation of Radio Wave Signals Coupled Into Twelve Large Building Structures.  

National Technical Information Service (NTIS)

This is the fourth in a series of NIST technical notes (TN) on propagation and detection of radio signals in large building structures (apartment complex, hotel, office buildings, sports stadium, shopping mall, etc.). The first, second, and third NIST Tec...

C. L. Holloway D. Camell G. Koepke K. A. Remley W. F. Young

2008-01-01

414

HiLat scintillation measurements at Spitsbergen  

NASA Astrophysics Data System (ADS)

Since October 1984, the amplitudes of 137 and 413 MHz HiLat radio beacon transmissions have been recorded at the Polish Polar Station at Hornsund, Spitsbergen (Svalbard) (77.00 deg N, 15.55 deg E). Graphs are presented of the magnetic local time dependence of the percentage occurrence of scintillation with SI greater than 0 and 0.3. For Kp = 3, scintillation occurrence is at a minimum at noon; for Kp less than 3, scintillation is at a maximum in the dawn and dusk sectors. The scintillation intensity is found to rapidly decrease on the equatorward side of the auroral oval.

Wernik, A. W.; Gola, M.

415

A CMOS UWB transmitter for possible use for medical and biological imaging based on radio-wave induced ultrasound.  

PubMed

Medical and biological imaging based on radio-wave induced ultrasound with a single source capable of irradiating multiple signals of different frequencies simultaneously can be implemented using ultra-wideband (UWB) technique. Development of a low-cost miniature UWB CMOS transmitter that can be used for this medical application is presented. The UWB transmitter designed using a 0.25-µm CMOS process can generate and transmit both monocycle pulses from 140 to 350 ps and impulses from 100 to 300 ps which contain many concurrent frequencies such as 3.1-10.6 GHz of the UWB spectrum. PMID:24110982

Nguyen, Andrew; Nguyen, Cam

2013-07-01

416

Search for radio-bursts from magnetized exoplanets in decameter wave band  

Microsoft Academic Search

We report on an attempt of detecting radio emissions (similar to Jupiter S-bursts) from 20 candidate exoplanets located within ~25 parsecs distance from the Earth. The combination of the world largest decameter radio telescope UTR-2, located near Kharkov, Ukraine, broad-band multichannel acousto-optical spectrometer with digitized output, and special post-processing software for eliminating man-made interference resulted in high sensitivity (down to

V. B. Ryabov; P. Zarka; B. P. Ryabov

2003-01-01

417

The Receiving System for Long-Wave Trans-Atlantic Radio Telephony  

Microsoft Academic Search

Transmission considerations and practical limitations indicate that in the lower frequency range, frequencies near 60 kc are best suited for transatlantic radio-telephone transmission. A radio receiving location in Maine gives a signal-to-noise ratio improvement over a New York location equivalent to increasing the power of the British transmitter about 50 times. Various types of receiving antennas are briefly discussed. The

A. Bailey; S. W. Dean; W. T. Wintringham

1928-01-01

418

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

419

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

420

Forecasting Equatorial Scintillation Activity in Real-time  

NASA Astrophysics Data System (ADS)

It is well-known that the generation of equatorial, F-region plasma density irregularities, via the Generalized Rayleigh-Taylor instability mechanism is critically dependent on the magnitude of the pre-reversal enhancement (PRE) in upward ExB drift velocity after sunset. These plasma density "bubbles" that are generated after sunset lead to the "scintillation" of trans-ionospheric radio wave signals that pass through these bubbles and is commonly referred to as "scintillation activity". Communication and Navigation systems can be severely disrupted by these plasma density irregularities. A measure of scintillation activity is given by the "S4 Index" and a network of Air Force, ground-based UHF and L-band receivers measuring the S4 Index is called the SCIntillation Network Decision Aid (SCINDA) network. This paper describes a technique for automatically forecasting, in real-time, the occurrence or non-occurrence of scintillation activity that relies on real-time data from a ground-based ionospheric sounder at or near the geomagnetic equator. After sunset, the height-rise with time of the bottom-side of the F-layer reflects the magnitude of the upward ExB drift velocity. The value of the ionospheric parameter, h'f (the virtual height of the bottom-side F-layer) at 1930 LT reflects the integrated ExB drift effect on lifting the F-layer to an altitude where the Rayleigh-Taylor instability mechanism becomes important. Incorporating observed h'f values from the Jicamarca, Peru digital sounder at 1930 LT and relating these values to the Total Hourly S4 Index (THS4) observed by the UHF receiver at the Ancon, Peru SCINDA site, it is found that a "threshold" in h'f exists below which, THS4 < 1 (no scintillation activity) and above which THS4 > 1 (scintillation activity). Examples of Jicamarca sounder observations and h'f values prior to the onset of scintillation activity are given. We present results that describe how the threshold value of h'f changes with solar cycle activity and how these results have been incorporated into a real-time capability for automatically forecasting scintillation activity that is available on Google Earth to all interested parties.

Redmon, R.; Anderson, D.; Caton, R. G.; Bullett, T. W.

2008-12-01

421

The short distance propagation of LF 40 kHz radio waves and some aspects of the D-region  

NASA Astrophysics Data System (ADS)

An analysis is made of the amplitude and phase data for LF 40 kHz radio wave propagated over a surface distance of 395 km to examine its propagation characteristics, and some aspects of the D-region as inferred from them are discussed. The analysis shows that the amplitude of the sky wave remains nearly constant during daytime while the nighttime amplitude varies appreciably. It is also demonstrated that the amplitude of the skywave is enhanced during daytime on winter anomaly days and that the occurrence of a winter anomaly event can be predicted by detecting the characteristic changes in the pattern of the occurrence time of interference maxima and minima. Finally, it is inferred from the analysis of the interference pattern that a transition layer appears during the periods of sunrise and sunset. This layer has a semi-peak below 80 km and extends upward to blend with the E-layer.

Ishimine, Tsuyoshi; Echizenya, Yoshimatsu

1989-11-01

422

HF Radio Wave Transmission over Sea Ice And Remote Sensing Possibilities  

Microsoft Academic Search

Ground wave propagation is analyzed for a path where sea water is covered by a uniform layer of sea ice. The source is taken to be a vertical electric dipole on or above the ice layer. The solution indicates that a trapped surface wave is significant at short ranges while, at longer ranges, the usual ground wave modes are dominant.

David A. Hill; James R. Wait

1981-01-01

423

HF radio wave transmission over sea ice and remote sensing possibilities  

Microsoft Academic Search

Ground wave propagation is analyzed for a path where sea water is covered by a uniform layer of sea ice. The source is taken to be a vertical electric dipole on or above the ice layer. The solution indicates that a trapped surface wave is significant at short ranges while, at longer ranges, the usual ground wave modes are dominant.

D. A. Hill; J. R. Wait

1981-01-01

424

Radio-over-Fiber Multi-service MM-Wave Interconnection with Photonic Upconversion, Dual Band Remote Delivery and Photonic Envelop Detection  

Microsoft Academic Search

A broadband radio-over-fiber architecture with dual-band remote delivery capabilities based on photonic up-conversion and envelop detection for wireless and wireline multi-service transmission is proposed. The architecture has been experimentally demonstrated for Gigabit-Ethernet wireless LAN interconnection employing millimeter-wave point-to-point radio links. Moreover, the simultaneous transmission of digital base-band data and intermediate-frequency signals has been analytically investigated

M. A. Piqueras; B. Vidal; H. Pfrommer; V. Polo; A. Ramirez; D. Zorrilla; J. Marti

2006-01-01

425

Coronal mass ejection kinematics deduced from white light (Solar Mass Ejection Imager) and radio (Wind/WAVES) observations  

NASA Astrophysics Data System (ADS)

White-light and radio observations are combined to deduce the coronal and interplanetary kinematics of a fast coronal mass ejection (CME) that was ejected from the Sun at about 1700 UT on 2 November 2003. The CME, which was associated with an X8.3 solar flare from W56°, was observed by the Mauna Loa and Solar and Heliospheric Observatory (SOHO) Large-Angle Spectrometric Coronograph (LASCO) coronagraphs to 14 R?. The measured plane-of-sky speed of the LASCO CME was 2600 km s-1. To deduce the kinematics of this CME, we use the plane-of-sky white light observations from both the Solar Mass Ejection Imager (SMEI) all-sky camera on board the Coriolis spacecraft and the SOHO/LASCO coronagraph, as well as the frequency drift rate of the low-frequency radio data and the results of the radio direction-finding analysis from the WAVES experiment on the Wind spacecraft. In agreement with the in situ observations for this event, we find that both the white light and radio observations indicate that the CME must have decelerated significantly beginning near the Sun and continuing well into the interplanetary medium. More specifically, by requiring self-consistency of all the available remote and in situ data, together with a simple, but not unreasonable, assumption about the general characteristic of the CME deceleration, we were able to deduce the radial speed and distance time profiles for this CME as it propagated from the Sun to 1 AU. The technique presented here, which is applicable to mutual SMEI/WAVES CME events, is expected to provide a more complete description and better quantitative understanding of how CMEs propagate through interplanetary space, as well as how the radio emissions, generated by propagating CME/shocks, relate to the shock and CME. This understanding can potentially lead to more accurate predictions for the onset times of space weather events, such as those that were observed during this unique period of intense solar activity.

Reiner, M. J.; Jackson, B. V.; Webb, D. F.; Mizuno, D. R.; Kaiser, M. L.; Bougeret, J.-L.

2005-09-01

426

Comparing the H-alpha Intensity and Radio Wave Scattering on Eight Low-Latitude Lines of Sight  

NASA Astrophysics Data System (ADS)

Spangler and Reynolds compared H-alpha intensities, measured using the Wisconsin Fabry-Perot interferometer, with radio-wave scattering sizes of eight extragalactic sources along low-latitiude lines of sight. They find that some correlation exists between scattering and H-alpha intensity, as one might expect. However, the H-alpha observations were made with a 50(') beam size; higher resolution observations might provide a more accurate measure of the intensity along the scattering line of sight. We made sensitive, arcminute resolution H-alpha images of the same fields to upgrade the accuracy of their results. We find that many of their measured H-alpha intensities are accurate, but some of the higher intensities are biased upward by the presence of clumped emission. Appropriate reduction of these large intensities increases the degree of correlation between scattering and H-alpha intensity, thus strengthening their original conclusions. This work is a first step towards using our spectral-line imaging system for a more extensive study of the relationship between the warm ionized medium and scattering of radio waves. This research was supported by NSF grant AST-9319670 and a grant from the Horton Foundation to Virginia Tech.

Simonetti, J. H.; Dennison, B.; Topasna, G. A.

1995-12-01

427

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

NASA Astrophysics Data System (ADS)

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

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

1985-12-01

428

Wave structures in the electron density pro(le in the ionospheric D- and E-layers observed by radio holography analysis of the GPS\\/MET radio occultation data  

Microsoft Academic Search

Vertical distribution of the electron density in the upper atmosphere can be studied using high-precision global positioning system (GPS). In this paper, we show that the radio holography method allows one to determine the vertical pro(le of the electron density and monitoring wave structures in the upper atmosphere. As an example of this approach, results of analysis of data corresponding

A. Pavelyeva; T. Tsuda; K. Igarashi; Y. A. Liou; K. Hocke

429

Determination of Area-Averaged Water Vapour Fluxes with Large Aperture and Radio Wave Scintillometers over a Heterogeneous Surface – Flevoland Field Experiment  

Microsoft Academic Search

A large aperture scintillometer (LAS) andradio wave scintillometer (RWS)were installed over a heterogeneous areato test the applicability of the scintillation method.The heterogeneity in the area, whichconsisted of many plots, was mainly caused bydifferences in thermal properties ofthe crops; the variations in theaerodynamic roughness lengthwere small. The water vapour fluxesderived from the combined LAS-RWSsystem, also known as the two-wavelengthmethod, agreed fairly

W. M. L. Meijninger; A. E. Green; O. K. Hartogensis; W. Kohsiek; J. C. B. Hoedjes; R. M. Zuurbier; H. A. R. De Bruin

2002-01-01

430

Determination of Area-Averaged Water Vapour Fluxes with Large Aperture and Radio Wave Scintillometers over a Heterogeneous Surface Flevoland Field Experiment  

Microsoft Academic Search

A large aperture scintillometer (LAS) andradio wave scintillometer (RWS)were installed over a heterogeneous areato test the applicability of the scintillation method.The heterogeneity in the area, whichconsisted of many plots, was mainly caused bydifferences in thermal properties ofthe crops; the variations in theaerodynamic roughness lengthwere small. The water vapour fluxesderived from the combined LAS-RWSsystem, also known as the two-wavelengthmethod, agreed fairly

W. M. L. Meijninger; A. E. Green; O. K. Hartogensis

2002-01-01

431

47 CFR 32.2231 - Radio systems.  

Code of Federal Regulations, 2010 CFR

...original cost of radio equipment used to provide radio communication channels. Radio equipment is that equipment which is used for...reception, modulation, and demodulation of radio waves in free space over which communication...

2009-10-01

432

47 CFR 32.2231 - Radio systems.  

Code of Federal Regulations, 2010 CFR

...original cost of radio equipment used to provide radio communication channels. Radio equipment is that equipment which is used for...reception, modulation, and demodulation of radio waves in free space over which communication...

2010-10-01

433

Influence of Long Waves on Energy Spectra of Radio Signals Scattered by the Sea Surface.  

National Technical Information Service (NTIS)

The report contains an investigation of a fine structure of radar signals scattered by the sea surface at small slip angles. A model is suggested for the scattering surface which permits an explanation of the observed frequency shifts of radio signals of ...

I. A. Leikin I. E. Ostrovskii A. D. Rozenberg V. G. Ruskevich I. M. Fuks

1975-01-01

434

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

435

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

436

Radio-Wave Scattering of 3C279 by the Solar Wind  

Microsoft Academic Search

The apparent sizes of radio sources increase when they are observed through the solar wind due to turbulent fluctuations of electron density. The defining characteristics of this turbulence are the inner and outer scales, corresponding to the smallest and largest lengthscales on which the fluctuations occur; and a power spectral index, which relates the relative strength of large and small

K. M. Desai; V. Dhawan; K. R. Anantharamaiah; P. Gothaskar

1996-01-01

437

Scattering of radio waves from the mesosphere. II - Evidence for intermittent mesospheric turbulence  

Microsoft Academic Search

Strong intermittency of coherent VHF radio echoes from 70-80 km height, observed at Jicamarca, Peru, suggests the existence of sudden bursts in the rate at which energy is dissipated per unit mass by turbulence. It is shown that the observed correlation between the power and correlation time of these echoes implies that stronger turbulence occurs in thinner layers. A detailed

P. K. Rastogi; S. A. Bowhill

1976-01-01

438

The amplitude fluctuations of the radio wave scattered from a thick ionospheric layer with weak irregularities  

Microsoft Academic Search

The signal received at the ground from a satellite or radio star shows small fluctuations of both phase and amplitude, which are produced by irregularities of refractive index in the ionosphere. The amplitude fluctuations are much the easier to measure and this paper examines theoretically what can be learned about the ionosphere from a study of amplitude fluctuations alone. The

K. G. Budden

1965-01-01

439

Measurements and Predictions of HF Ground Wave Radio Propagation Over Irregular, Inhomogeneous Terrain.  

National Technical Information Service (NTIS)

Measurements of radio propagation path loss were made over four paths in the 3 to 30 MHz band. The paths were of lengths up to 45 km in the Boulder, CO, area. They ranged from smooth to mountainous terrain, from open areas with few or no man-made structur...

J. E. Adams J. C. Carroll E. A. Costa D. R. Ebaugh J. R. Godwin

1984-01-01

440

Correlation of Long Wave Transatlantic Radio Transmission with Other Factors Affected by Solar Activity  

Microsoft Academic Search

Phenomena usually thought of as being affected by solar activity are: Sun spots, solar constant, earth's magnetic field, atmospheric electricity, auroras, earth currents, and, as has been recently shown, radio transmission. In order to correlate these with each other, the daily character of each must be reduced to some single figure. The factors which lend themselves most easily to quantitative

C. N. Anderson

1928-01-01

441

Refraction of Radio Waves at Low Angles within Various Air Masses  

Microsoft Academic Search

The refractive index structure and bending of radio rays within air masses of nonexponential refractive index height structure is treated in terms of the value expected in an average atmosphere of exponential form. It is demonstrated that refraction differences within air masses arise from departures of refractive index structure from the normal ex- ponential decrease with height. The effect upon

B. R. Bean; J. D. Horn; L. P. Riggs

1960-01-01

442

Oxygen and water vapor absorption of radio waves in the atmosphere  

Microsoft Academic Search

Summary Calculated values of the gaseous atmospheric absorption are presented for the frequency range 100 to 50,000 Mc at elevations above ground up to at least 130,000 feet, for average conditions during February and August at Bismarck, N. D. and Washington, D. C. Total radio path absorptionsare presented for tropospheric forward scatter communication links for distances of 100, 300 and

B. R. Bean; R. Abbott

1957-01-01

443

Receiving and transmitting light-like radio waves: Antenna effect in arrays of aligned carbon nanotubes  

Microsoft Academic Search

We present optical measurements of random arrays of aligned carbon nanotubes, and show that the response is consistent with conventional radio antenna theory. We first demonstrate the polarization effect, the suppression of the reflected signal when the electric field of the incoming radiation is polarized perpendicular to the nanotube axis. Next, we observe the interference colors of the reflected light

Y. Wang; K. Kempa; B. Kimball; J. B. Carlson; G. Benham; W. Z. Li; T. Kempa; J. Rybczynski; A. Herczynski; Z. F. Ren

2004-01-01

444

SBR image approach for radio wave propagation in tunnels with and without traffic  

Microsoft Academic Search

We propose a deterministic approach to model the radio propagation channels in tunnels with and without traffic. This technique applies the modified shooting and bouncing ray (SBR) method to find equivalent sources (images) in each launched ray tube and sums the receiving complex amplitude contributed by all images coherently. In addition, the vector effective antenna height (VEH) is introduced to

Shin-Hon Chen; Shyh-Kang Jeng

1996-01-01

445

Analysis of the radio acoustic sounding system using a chirped acoustic wave  

Microsoft Academic Search

We investigated radio acoustic sounding system (RASS) echoes backscattered from refractive index fluctuations produced by an acoustic pulse linearly modulated in frequency (a chirped acoustic pulse). We have numerically simulated errors of the Doppler frequency shift which are caused by the fact that the widths of the acoustic and radar pulse are finite. We analytically showed that a RASS with

Yoshihisa Masuda; Jun Awaka; Kenji Nakamura; Tatsuhiro Adachi; Toshitaka Tsuda

1992-01-01

446

Study of equatorial ionospheric F-region irregularities by reflection, backscatter and transmission of radio waves  

Microsoft Academic Search

Modified range time intensity (MRTI) records of the 50-MHz backscatter radar at Jicamarca were compared with simultaneous vertical incidence ionograms from Huancayo, as well as VHF radio transmissions from the ATS-3 geostationary satellite. The altitudes of range spread echoes in the ionogram corresponded well with the altitudes of maximum echo scatter intensity in VHF and backscatter MRTI records. It is

R. G. Rastogi

1984-01-01

447

Depolarization, Scattering, and Attenuation of Circularly Polarized Radio Waves by Spherically Asymmetric Melting Ice Particles  

Microsoft Academic Search

The eccentric spheres model and an extended Mie solution are used to formulate scattering of a plane, electromagnetic wave by a single melting ice particle as well as by a horizontal layer of such particles. The incident wave is left-hand circularly polarized, whereas the scattered wave, as a result of depolarization by the spherically asymmetric particles, comprises left-hand and right-hand

Melina P. Ioannidou; Dimitris P. Chrissoulidis

2007-01-01

448

Nonlinear structuring of the ionosphere modified by powerful radio waves at low latitudes  

Microsoft Academic Search

The problem of the nonlinear structuring of the modified ionosphere due to the self-focusing of the pump wave on the bunches of striations is investigated. Two main conditions of self-focusing are formulated: (1) propagation of the pump wave quite along the magnetic field for effective excitation of striations, and (2) trapping of the pump wave by large-scale irregularities. It is

A. Gurevich; H. Carlson; M. Kelley; T. Hagfors; A. Karashtin; K. Zybin

1999-01-01

449

Noise reduction in GaN-based radio frequency surface acoustic wave filters  

Microsoft Academic Search

In this work we have fabricated and characterized GaN based surface acoustic wave (SAW) delay lines grown by metal organic chemical vapor deposition (MOCVD) on sapphire substrate. The acoustic wave velocity of 0th Rayleigh and Sezawa modes, and the piezoelectric electromechanical coupling constant have been measured for different wave numbers in a 2 mum-thick layer. The acoustic velocity resulted to

S. Petroni; G. Tripoli; C. Combi; B. Vigna; M. de Vittorio; M. T. Todaro; G. Epifani; R. Cingolani; A. Passaseo

2004-01-01

450

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

451

ESD sources pinpointed by numerical analysis of radio wave emissions 1 © 1997. Reprinted with permission, after revision, from Electrical Overstress\\/Electrostatic Discharge Symposium Proceedings, EOS19, Santa Clara, CA, USA, September 23–25, 1997. 1  

Microsoft Academic Search

ESD (electrostatic discharge) events are a source of radio waves. Time delay information from a system of antennas detecting those radio waves can be used, much like a GPS (global positioning satellite) system, to pinpoint the location of the discharge. In this system, numerical analysis is used to successively approximate the location in space at which an emitted electromagnetic signal

Joe Bernier; Gregg Croft; Rex Lowther

1998-01-01

452

Simulation of GPS Scintillation and TEC Using Rocket Borne Ionospheric Density Measurements  

NASA Astrophysics Data System (ADS)

Scintillations in trans-ionospheric radio signals arise as the signal propagates through naturally occurring plasma irregularities. If the receiver, satellite, or ionospheric irregularities are in motion, a time series of signal fading and phase fluctuations will occur at the receiver. It is well known that diffraction of the radio phase front produces amplitude and phase fluctuations even at GPS frequencies. Significant progress in scintillation modeling has been made since the dawn of the space age, with most of the efforts focused on statistically characterizing the plasma structure and radio wave fluctuations. In an attempt to better relate measured scintillations to the physical processes that cause them, we present results from modeling scintillation using a standard phase-screen approach but with electron density distributions measured from rocket borne Langmuir probes as input to model. The result of our model is simulated GPS phase and amplitude for a receiver on the ground, which we compare to actual GPS measurements from the Italian INGV network in the region. The ICI-2 Rocket was launched into moderate cusp irregularities on Dec 5, 2008, and measured three regions of F-region density fluctuation that appear consistent with the F-region gradient drift instability. These fluctuations caused modeled S4 of 0.2 and sigma phi of 0.1 consistent with nearby GPS measurements. One of the unexpected results of this work is that we find that the weak scintillations can cause non-physical fluctuations in TEC that peak at values as high as 2 TECU (~20 cm range error) and appear as TEC micropulsations, when indeed they are merely differenced diffraction patterns from two frequencies. This finding will be of interest to both practical GPS applications and scientists interested in using GPS to measure physical micropulsations.

Dyrud, L.; Murr, D.; Moen, J. I.; Alfonsi, L.

2010-12-01

453

Centralized Lightwave Radio-over-Fiber System with High-Frequency Optical Millimeter-Wave Generation by Low-Frequency and Low-Bandwidth Optical and Electrical Sources  

Microsoft Academic Search

We have proposed a novel radio-over-fiber (ROF) architecture to reduce the system cost at both central office (CO) and base station (US). In this architecture, by incorporating the proper DC bias and optical filtering techniques in CO, the optical millimeter-wave (mm-wave) carriers are generated with four times frequency of the local oscillator (LO) signal. The BS is simplified by using

Jianjun Yu; Ting Wang; Zhensheng Jia; Gee Kung Chang

2007-01-01

454

Wideband Radio Wave Observations of Lightning Discharge by Maido-1 Satellite  

NASA Astrophysics Data System (ADS)

Maido-1 satellite was launched on 23 January 2009. The satellite carries the radio-frequency payload, Broadband Measurement of Waveform for VHF Lightning Impulses (VHF sensor), for research on lightning discharges. The final goal of our research is to locate sources of impulsive VHF radiation from lightning discharges and constantly monitor lightning activity from space. Maido-1 satellite has the aim of proving the functions of the sensor in space and to study the radio propagation characteristics of the ionosphere. Through the operation/observation for 5 months, more than 10, 000 VHF signals have been recorded. The locations where VHF signals are detected and the examples of the received waveforms are presented in this paper. We discuss the regional dependency of the received signals.

Kikuchi, Hiroshi; Morimoto, Takeshi; Ushio, Tomoo; Kawasaki, Zen

455

Controlled stimulation of magnetospheric electrons by radio waves: experimental model for lightning effects  

SciTech Connect

Magnetospheric electrons precipitated by ground-based coded very low frequency radio transmissions have been detected by rocket measurement of bremsstrahlung x-rays, caused by impact of the electrons with the upper atmosphere. The direct correlations obtained between the very low frequency signals and the x-rays demonstrate the limits of sensitivity required and indicate that this remote sensing technique would be useful for future study of very low frequency effects induced by single lightning strokes.

Goldberg, R.A. (NASA/Goddard Space Flight Center, Greenbelt, MD); Curtis, S.A.; Barcus, J.R.; Siefring, C.L.; Kelley, M.C.

1983-03-18

456

Controlled stimulation of magnetospheric electrons by radio waves: experimental model for lightning effects.  

PubMed

Magnetospheric electrons precipitated by ground-based coded very low frequency radio transmissions have been detected by rocket measurement of bremsstrahlung x-rays, caused by impact of the electrons with the upper atmosphere. The direct correlations obtained between the very low frequency signals and the x-rays demonstrate the limits of sensitivity required and indicate that this remote sensing technique would be useful for future study of very low frequency effects induced by single lightning strokes. PMID:17735612

Goldberg, R A; Curtis, S A; Barcus, J R; Siefring, C L; Kelley, M C

1983-03-18

457

Analysis of Propagation Conditions of ELF Radio Waves on the ``Zeus''-Transbaikalia Path  

NASA Astrophysics Data System (ADS)

We consider the results of measurements of the absolute values of horizontal electric and magnetic components of the electromagnetic field of the ``Zeus'' ELF radio facility at frequencies 33, 44, 82, and 188 Hz, carried out in Transbaikalia. Electromagnetic-field variations during 17 semidiurnal sessions (about 204 hours of synchronous records) are analyzed. The length of the ``Zeus''-Transbaikalia path is approximately 4000 km.

Bashkuev, Yu. B.; Khaptanov, V. B.; Khankharaev, A. V.

2003-12-01

458

Significance of common scatterers in multi-link indoor radio wave propagation  

Microsoft Academic Search

Correlation between different links is an essential characteristic for many of the forthcoming radio communication systems that utilize the multiple-input-multiple-output (MIMO) technology. This paper investigates the physical phenomena that cause the inter-link correlation by introducing a measure to quantify how large amount of energy propagates via similar propagation mechanisms in different links. The conditions for the so-called significance of common

Juho Poutanen; Katsuyuki Haneda; Jussi Salmi; Veli-Matti Kolmonen; Fredrik Tufvesson; Tommy Hult; Pertti Vainikainen

2010-01-01

459

Variations in the ionospheric wave perturbation spectrum during periodic heating of the plasma by high-power high-frequency radio waves  

NASA Astrophysics Data System (ADS)

We present the results of spectral analysis of temporal variations in the Doppler frequency shift of the ionosphere-reflected signals from a high-frequency vertical ionospheric sounding radar located near the city of Kharkov in the days of exposure of the ionospheric plasma to the high-power radio emission of the Sura facility (Nizhny Novgorod) and in the reference day in the absence of such an exposure. It was established that the spectral characteristics of quasiperiodic variations in the Doppler frequency shift in the range of periods 10-60 min in the days of work of the facility and in the reference day differed significantly. This is considered as evidence in favor of the generation (amplification) of acoustic-gravity waves propagating at the ionospheric altitudes by high-power periodic high-frequency radiation of the Sura facility.

Chernogor, L. F.; Frolov, V. L.; Komrakov, G. P.; Pushin, V. F.

2011-07-01

460

Type III Metric Radio-Wave Activity Prior to and During Active Region Flaring and CMEs (Invited)  

NASA Astrophysics Data System (ADS)

From the time that type III metric radio-wave activity has been known, and imaged, there has been a realization that this activity often increases during, and for some events from a few minutes to several hours prior to the major manifestations observed for a flare or Coronal Mass Ejection (CME). We review these analyses from as long ago as the observations from Culgoora, Australia, and more recently from the French Nancay radio observatory. We find there can be precursor activity before a flare or CME as indicated by the increasing numbers of isolated type III bursts, and that this can be a maximum prior to the most obvious manifestation of either the surface flare or the most obvious rapid outward coronal motion of a CME. Current imaging measurements from the Nancay radio array further clarify the location of this activity for specific events such as the 26 April 2008 CME that was observed just following the Whole Heliosphere Interval (WHI) near the time of solar minimum. A plausible explanation for this precursor activity exists, and we expect that this idea can be more fully tested using present-day observations. As solar activity increases and more observations become available from, for instance, the Murchison Widefield Array (MWA) now under construction in Western Australia, far better worldwide temporal coverage for this type of analysis will exist. In conjunction with current NASA instrumentation such as the Solar TErrestrial RElations Observatory (STEREO) and SOlar and Heliospheric Observatory (SOHO) coronagraphs, and the Solar Dynamics Observatory (SDO), we expect a significant improvement in our understanding of this unique flare and CME precursor activity.

Jackson, B. V.; Hick, P. P.; Buffington, A.; Oberoi, D.; Matthews, L. D.

2010-12-01

461

Continuous-Wave Radio Transmission on a Wave Length of 100 Meters, Using a Special Type of Antenna  

Microsoft Academic Search

The paper describes a method and apparatus for continuouswave transmission on a wave length of 105 meters. An electron tube generating set was used which employed four 50-watt tubes in a tuned-plate primary circuit, coupled to the antenna circuit. The antenna was rectangular in shape, 18 feet (5.5 m.) high by 40 feet (12.4. m.) long, and consisted of 23

F. W. Dunmore

1923-01-01

462

Artificial optical emissions in the high-latitude thermosphere induced by powerful radio waves: An observational review  

NASA Astrophysics Data System (ADS)

High-power high-frequency radio waves beamed into the ionosphere with O-mode polarization cause plasma turbulence, which can accelerate electrons. These electrons collide with the F-layer neutrals causing artificial optical emissions identical to the natural aurora. The brightest optical emissions are O( 1D) 630 nm, with a threshold of ˜2 eV, and O( 1S) 557.7 nm, with a threshold of ˜4.2 eV. The optical emissions give direct evidence of electron acceleration by plasma turbulence, the non-Maxwellian electron energy spectrum as well as the morphology of the accelerating region with high spatial resolution. HF pumping of the ionosphere also causes bulk electron temperature enhancements, but these alone are not sufficient to explain the optical emissions. We review the published radar and optical observations of high-latitude pump-induced artificial optical emissions and introduce new data.

Kosch, M. J.; Pedersen, T.; Rietveld, M. T.; Gustavsson, B.; Grach, S. M.; Hagfors, T.

463

Simplified millimeter-wave radio-over-fiber system using optical heterodyning of low-cost independent light sources and RF homodyning at the receiver  

Microsoft Academic Search

A simplified, cost-effective millimeter-wave radio-over-fiber system is proposed by heterodyning two independent low-cost light-sources and RF homodyning at the receiver that suppresses phase-noise effects. Proposed system avoids phase\\/frequency locking, high-speed modulators and local oscillators\\/mixers in CO and BSs.

A. H. M. Razibul Islam; Masuduzzaman Bakaul; Ampalavanapillai Nirmalathas; Graham E. Town

2009-01-01

464

Transmission characteristics of VLF\\/ELF radio waves through the Jovian ionosphere  

Microsoft Academic Search

The propagation characteristics of whistler-mode waves through the plausible profiles of the Jovian ionosphere have been investigated by means of full-wave numerical computations. There were three different profiles examined in detail: an irregular profile based on Pioneer measurements, a more-idealized smoother profile, and a smooth profile with a low-altitude ledge. The whistler transmission losses for the Pioneer profiles with several

Ken Nagai; Kenji Ohta; Yasuhide Hobara; Masashi Hayakawa

1993-01-01

465

Simultaneous observation of VHF radio wave transmission anomaly propagated beyond line of site prior to earthquakes in multiple sites  

NASA Astrophysics Data System (ADS)

The VHF radio wave transmission anomalies propagated beyond line of site prior to earthquakes (M>4), (hereafter termed EQ-echo) have been observed more than 20 times from 2004 at the Erimo observatory (ERM) in Hokkaido, Northern Japan. A statistical relationship between magnitude of preceding earthquake and total duration time of the EQ-echo has been proposed (Moriya et al.2009). To confirm a region where the EQ-echo simultaneously observed for each earthquake, we installed another 3 observatory with approximately 5 km spacing in the surroundings of ERM. The EQ-echoes have been observed simultaneously at two observatories prior to four earthquakes since 2008. The initial time and duration of each EQ echo were same time in several cases but different at some minutes each other in other cases. The wave forms of the EQ-echoes were similar in both records. In the Fuyushima observatory (FYS, 10km away from ERM) , three-way antennas were installed at every 120 degree to detect an arrival direction of EQ-echoes. Simultaneous observations of EQ-echoes at ERM and FYS for the preceding EQ (M=4.7) that occurred in the Hidaka mountains revealed that this EQ-echo came from direction of the epicenter based on the FYS observation and this direction was consistent with that of EQ-echo observed simultaneously in ERM. Although some of simultaneous observed EQ-echoes were observed in same time completely at both observatories, but some of them were with time rag of duration of each EQ-echo between multiple observed sites. We discussed what these time rags mean by considering possibilities of moving of scattering objects, generation of a radio duct, and so on, as in response to this fact.

Yamashita, H.; Mogi, T.; Moriya, T.; Takada, M.; Morisada, M.

2010-12-01

466

Anomalous pre-seismic transmission of VHF-band radio waves resulting from large earthquakes, and its statistical relationship to magnitude of impending earthquakes  

NASA Astrophysics Data System (ADS)

To confirm the relationship between anomalous transmission of VHF-band radio waves and impending earthquakes, we designed a new data-collection system and have documented the anomalous VHF-band radio-wave propagation beyond the line of sight prior to earthquakes since 2002 December in Hokkaido, northern Japan. Anomalous VHF-band radio waves were recorded before two large earthquakes, the Tokachi-oki earthquake (Mj = 8.0, Mj: magnitude defined by the Japan Meteorological Agency) on 2003 September 26 and the southern Rumoi sub-prefecture earthquake (Mj = 6.1) on 2004 December 14. Radio waves transmitted from a given FM radio station are considered to be scattered, such that they could be received by an observation station beyond the line of sight. A linear relationship was established between the logarithm of the total duration time of anomalous transmissions (Te) and the magnitude (M) or maximum seismic intensity (I) of the impending earthquake, for M4-M5 class earthquakes that occurred at depths of 48-54 km beneath the Hidaka Mountains in Hokkaido in 2004 June and 2005 August. Similar linear relationships are also valid for earthquakes that occurred at different depths. The relationship was shifted to longer Te for shallower earthquakes and to shorter Te for deeper ones. Numerous parameters seem to affect Te, including hypocenter depths and surface conditions of epicentral area (i.e. sea or land). This relationship is important because it means that pre-seismic anomalous transmission of VHF-band waves may be useful in predicting the size of an impending earthquake.

Moriya, T.; Mogi, T.; Takada, M.

2010-02-01

467

Structure of ionospheric irregularities from amplitude and phase scintillation observations  

SciTech Connect

The mutual coherence function Gamma 2, or the second moment of the complex amplitude of a radio wave which traverses through equatorial F region irregularities, is computed from amplitude and phase scintillation data. Theoretically, the equation satisfied by the coherence function has an analytic solution over the whole range of scintillation strength. This solution is directly related to the structure function for the phase fluctuations produced by the irregularities. Hence, the shape of the correlation function for variations in the total electron content along the signal path can be derived from the computed values of Gamma 2. With a suitable power-law model for the irregularities, an 'intermediate break scale', this scale, as well as the rms density fluctuation are deduced from a comparison of computed values for short-time lags with those expected from theory. During a postsunset scintillation event, this scale is found to increase with local time. In the context of the generalized Rayleigh-Taylor instability, which is the likely source of the irregularities, this increase may be attributed to a decline in the effective electric field prevailing in the region of the irregularities. 26 refs.

Bhattacharyya, A.; Rastogi, R.G. (Indian Institute of Geomagnetism, Colaba (India))

1991-04-01

468

Radio Wave Propagation along Earth-Space Paths in the Presence of a Multilayered Anisotropic Forest  

Microsoft Academic Search

Propagation of electromagnetic waves along earth-space paths in forest environments is analyzed in this paper, where the transmitter is placed in the air region above the vegetation, while the receiver may be in the air region or within the vegetation. This propagation model considers the forest as a horizontally stratified, anisotropic medium of canopy and trunk, bounded by ground below

Le-Wei Li; Chee-Keong Lee; Tat-Soon Yeo; Mook-Seng Leong

2002-01-01

469

MICROWAVE signal parametric transfer via radio channel using running wave resonator  

Microsoft Academic Search

Traveling-wave resonators (TWR) designed on the basis of directional couplers (DC), with locked up in the ring secondary arms, find a wide application in the systems of combining and decommutation of frequency channels, for example in the circuits of directed filters. A technical decision directed on a formation of a modulated signal with one adjacent frequency, for the application in

V. D. Rjabchij; V. V. Safonov; E. A. Taran

2009-01-01

470

Global estimates of gravity wave parameters from GPS radio occultation temperature data  

Microsoft Academic Search

Gravity waves (GWs) play critical roles in the global circulation and the temperature and constituent structures in the middle atmosphere. They also play significant roles in the dynamics and transport and mixing processes in the upper troposphere and lower stratosphere and can affect tropospheric weather. Despite significant advances in our understanding of GWS and their effects in different regions of

L. Wang; M. J. Alexander

2010-01-01

471

Mathematical space-time model of a sky wave radio field  

NASA Astrophysics Data System (ADS)

The three-dimensional mathematical field model of HF sky waves reflected by a spatially nonuniform nonstationary magnetoactive ionosphere is described. The model is based on the structural physical approach, which leads to complete understanding of the field structure in space and time associated with specific geomagnetic conditions.

Barabashov, B. G.; Anishin, M. M.; Pelevin, O. Y.

2006-10-01

472

Application of radio ground-wave propagation theory to the tomographic imaging of ground surfaces  

Microsoft Academic Search

Radiowave propagation over ground has been historically studied for predicting the radiated fields when the ground properties are known and the field has been well covered over the past hundred years. The theory of ground-wave propagation is applied to the inverse problem of the tomographic imaging of ground surfaces. After the inverse problem is formulated, an iterative technique for solving

Zhipeng Wu

2000-01-01

473

Absorption of radio waves by water vapor in the atmospheres of Venus and Mars  

Microsoft Academic Search

In this paper, we shall consider the quantitative relationships between the absorption coefficients of monomeric and dimeric molecules of water vapor in the atmospheres of Venus and Mars. This problem is of interest in the analysis of the conditions for the propagation of electromagnetic waves with wavelengths X ~ 0.7 mm [5] in the atmospheres of these planets and for

A. A. Viktorova; A. P. Naumov

1969-01-01

474

Energy Efficient Millimeter Wave Radio Link Establishment With Smart Array Antennas.  

National Technical Information Service (NTIS)

Consider a system of two millimeter wave transceiver nodes A and B. We assume that each node is equipped with a circular array antenna that has beamforming capability. We are interested in using the beamforming capability to find the best possible directi...

B. Neekzad J. S. Baras K. Sayrafian-Pour

2006-01-01

475

Critical Rain Intensity for Millimeter Wave Radio Link IP Network with Partial Mesh Topology  

Microsoft Academic Search

In this paper we described the algorithm and software for determining maximum rain intensity in the center of the rain cell, for which an IP network with millimeter wave links graph remains fully connected. Model of convective rain cell was assumed with Gaussian distribution that is moving due to influence of wind. Another problems that arise from use of real

Dragana Peric; Miroslav Peric

2005-01-01

476

European research activities on radio-wave propagation above 10 GHz in the framework of cost  

Microsoft Academic Search

The European joint research program on the influence of atmospheric conditions on electromagnetic wave propagation above 10 GHz implemented within the framework of the Eurocop-Cost (EUROpean Cooperation and Coordination in the field of Scientific and Technical research) projects in the field of telecommunications, is illustrated. The aims, type of cooperation envisaged, and criteria governing the research program are described. The

F. Fedi

1976-01-01

477

A fast time-domain wireless channel simulation tool for radio-wave propagation courses  

Microsoft Academic Search

The application of current implementations of electromagnetic simulators to realistic wireless communication problems requires excessively large computational time. As a result, computational electromagnetic tools have not been incorporated into the electromagnetics curricula yet. Building on a recent breakthrough in FDTD technology, we developed a novel simulation environment that enables the educational study of wave propagation in wireless links

Melissa Leung; Jackie Leung; Gerard S. Baron; Costas D. Sarris

2006-01-01

478

STUDY OF EFFECT OF RAIN AND DUST ON PROPAGATION OF RADIO WAVES AT MILLIMETER WAVELENGTH  

Microsoft Academic Search

The propagation of Electromagnetic waves in millimeter band is severely affected by rain rate, drop size and dust particle size in terms of attenuation, de-polarization and noise. The vertical looking radiometers will give vertical path attenuation due to rain as well as dust and line of sight link will give horizontal path attenuation whereas the satellite link gives slant path

O. P. N. Calla; J. S. Purohit

479

Radio wave propagation studies along an Earth-space satellite link  

Microsoft Academic Search

The use of superhigh microwave frequencies for satellite communications has many advantages, but its major drawback lies in the effects of atmospheric hydrometeors on electromagnetic wave propagation. One research effort under way to investigate this problem is being conducted by the European Space Agency, which will launch the Olympus-1 communications satellite in June 1989. One of this satellite's four payloads

Jacques Albert

1990-01-01

480

A full finite difference time domain implementation for radio wave propagation in a plasma  

Microsoft Academic Search

A full finite difference time domain methodology is developed for electromagnetic wave propagation in a plasma. The finite difference grid is consistent with central difference approximation of the curl, divergence and gradient operators that appear in the joint equations of Euler and Maxwell, and the coupling effects between the fluid velocity and the electric field. To accomplish the time advancement,

J. L. Young

1994-01-01

481

The Propagation of Radio Waves over the Surface of the Earth and in the Upper Atmosphere  

Microsoft Academic Search

Simple formulas and graphs are given which represent the ground-wave field intensity at the surface of the earth as radiated from a short vertical antenna at the surface of the earth. The theory is compared to some experimental results reported by other investigators to determine its range of application. The diffraction formula given is theoretically valid only at the lower

K. A. Norton

1936-01-01

482

Target detection and identification methods based on radio- and optical waves  

Microsoft Academic Search

Technological advances in the fields of microwave techniques, electrooptics, and computer technology are discussed in terms of application to target detection\\/identification systems. Increasing the target identification capability of these sensor systems is emphasized. Tunable lasers and IR heterodyne receivers are among the sensor systems described. Fundamental principles of target signature analysis are examined including the interaction between electromagnetic waves and

D. T. Gjessing

1978-01-01

483

Compact optoelectronic oscillator using whispering gallery mode resonators for radio-frequency and millimeter wave generation  

NASA Astrophysics Data System (ADS)

Optoelectronic oscillators are ultra-pure microwave generators based on optical energy storage instead of high finesse radio-frequency resonators. We present in this communication a new and compact architecture where the optical energy storage is performed by trapping laser light into the ultra-high Q whispering gallery modes of a millimeter-size disk resonator. As a proof of concept, we demonstrate the generation of a 10.7 GHz microwave with a phase noise of -110 dBrad2/Hz at 100 kHz. We also discuss in detail the potential of this architecture for the generation of microwaves with a frequency ranging from 50 to 200 GHz.

Volyanskiy, Kirill; Salzenstein, Patrice; Tavernier, Hervé; Pogurmirskiy, Maxim; Chembo, Yanne K.; Larger, Laurent

2011-02-01

484

Polarization of 920-MHz galactic radio waves in the Loop III region  

SciTech Connect

Measurements of the linear polarization of galactic background radio emission at 920 MHz are reported. The observations utilized an 8-m paraboloid with a 2/sup 0/56' x 2/sup 0/56' beam. A portion of Loop III has been surveyed (00/sup h/< or =..cap alpha..< or =10/sup h/, 54/sup 0/< or =delta< or =74/sup 0/). In this part of the sky two areas of enhanced polarization (approx. =2/sup 0/K) can be discriminated (near l<144/sup 0/, b<+6/sup 0/ and l<131/sup 0/, b<+9/sup 0/), as well as an extended region of low polarization (<0/sup 0/.3K) along bapprox. =+20/sup 0/.

Paseka, A.M.

1978-11-01

485

Effect of radio frequency waves of electromagnetic field on the tubulin.  

PubMed

Microtubules (MTs) are macromolecular structures consisting of tubulin heterodimers and present in almost every eukaryotic cell. MTs fulfill all conditions for generation of electromagnetic field and are electrically polar due to the electrical polarity of a tubulin heterodimer. The calculated static electric dipole moment of about 1000 Debye makes them capable of being aligned parallel to the applied electromagnetic field direction. In the present study, the tubulin heterodimers were extracted and purified from the rat brains. MTs were obtained by polymerization in vitro. Samples of microtubules were adsorbed in the absence and in the presence of electromagnetic fields with radio frequency of 900 Hz. Our results demonstrate the effect of electromagnetic field with 900 Hz frequency to change the structure of MTs. In this paper, a related patent was used that will help to better understand the studied subject. PMID:23470160

Taghi, Mousavi; Gholamhosein, Riazi; Saeed, Rezayi-Zarchi

2013-09-01

486

Light scintillation in oceanic turbulence  

Microsoft Academic Search

The scintillation index of plane and spherical light waves as well as of a Gaussian beam, propagating in the clear-water weakly turbulent ocean, is revealed. The results are of utmost importance for underwater optical communications and sensing. An analysis of the threshold between the weak and strong regimes of oceanic turbulence is made, with the accent on the contribution from

O. Korotkova; N. Farwell; E. Shchepakina

2012-01-01

487

Rocket experiment of VLF and MF radio wave measurement by using a single loop antenna  

NASA Astrophysics Data System (ADS)

A wideband loop antenna system has been tested using the sounding rocket S-310-18 to confirm its performance in detecting EM waves for frequencies from ELF to MF band in the lower ionosphere. The loop antenna system detected the one-hop whistlers with high S/N at 0.1-12 kHz and the spectra are used to study the propagation characteristics in the ionosphere. The VLF signal transmitted from the NDT station (Yosami, 17.4 + or - 0.05 kHz) was continuously received during the flight of rocket. The altitude dependence of the wave intensity and polarization are obtained. The polarization change of NDT signal from linear (free space mode) to circular (whistler mode) was clearly observed at a certain altitude in the ionosphere.

Okada, Toshimi; Nagano, Isamu

1990-02-01