Note: This page contains sample records for the topic radio wave scintillations from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

Spacecraft Radio Scintillation and Solar System Exploration  

NASA Technical Reports Server (NTRS)

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

Woo, Richard

1993-01-01

2

Dynamics of ionospheric irregularities producing VHF radio wave scintillations at low latitudes  

NASA Astrophysics Data System (ADS)

Using the data from a network of low latitude field stations in India, recording the amplitude scintillations on 244 MHz radio beacon signals transmitted from FLEETSAT at 73 deg E longitude, dynamics of patches of irregularities in the F-region have been estimated in E-W as well as N-S directions. The occurrence of scintillations in the Indian sector at a station close to the dip equator has been found to be at a maximum during E-months, less during D-months, and least during J-months. The scintillations are found to be greatly reduced during geomagnetic disturbances. The signature of individual scintillation events have been found to be remarkably identical at an E-W pair of stations seperated by 260 km.

Pathan, B. M.; Koparkar, P. V.; Rastogi, R. G.; Rao, D. R. K.

1991-02-01

3

East-west movement of ionospheric irregularities causing equatorial radio wave scintillations  

NASA Astrophysics Data System (ADS)

The paper describes the results of observation of the scintillations of radio beacon on 244 MHz from geostationary satellite Fleetsat received simultaneously at Trivandrum and Tiruchendur, both situated very close to the magnetic equator. The ionospheric cross-over point at 400 km for the two paths are separated by 105 km in east-west direction. It was observed that the scintillations at these two places were remarkably similar in pattern and duration. The E-W drift of plasma irregularity, calculated on the basis of time shift of onset or decay of identical scintillation patches at the two places, indicated a velocity of about 110 m/s eastward at 1930 hrs IST decreasing monotonously during the course of night and reaching a value of 60 m/s by 0330 hrs IST.

Koparkar, P. V.; Pathan, B. M.; Rastogi, R. G.

1991-10-01

4

Combination of a radio wave scattering algorithm with coherent radar data for equatorial scintillation predictions  

Microsoft Academic Search

1. Summary Ionospheric scintillation exhibits extreme variability in space and time, significantly degrading both the performance and the availability of space-based communication and navigation systems. For their support at equatorial latitudes, short-term scintillation forecast systems based on real-time measurements may explore the facts that the irregularities are field-aligned, their motion is ordered, and their lifetime is relatively long. One such

Emanoel Costa; Eurico R. de Paula; Esfhan A. Kherani; Keith M. Groves

5

A radio wave scattering algorithm and irregularity model for scintillation predictions  

Microsoft Academic Search

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

Emanoel Costa; Santimay Basu

2002-01-01

6

VHF radio scintillations at Bombay  

NASA Astrophysics Data System (ADS)

The simultaneous recordings of the amplitude scintillations of VHF radio signals from nearby geostationary satellites Fleetsat (at 73 deg E long.) and Sirio (at 65 deg E) received at Bombay (geog. lat. 19 deg N, geog. long. 73 deg E, mag. lat. 15 deg N) have revealed systematic time shifts in the starting and the ending of the individual scintillation events. The ionosphere crossover points of the two transmission paths were separated by only 80 km in the east-west direction, which was smaller than the average size of the irregularity patches. Scintillations normally started after 1930 h, reached a maximum at 2200 h, and slowly decreased until 1000 h, after which no scintillations were observed. The speed of the irregularity patches computed from the time shifts of these events was about 150 m/s in the early hours of the night, decreasing to about 100 m/s by midnight and showing much lower velocities in the post-midnight hours.

Koparkar, P. V.; Rastogi, R. G.

1985-10-01

7

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

8

MEXART Measurements of Radio Sources. Interplanetary Scintillation Array in Mexico  

NASA Astrophysics Data System (ADS)

The Mexican Array Radio Telescope (MEXART) consists of a 64x64 array of full-wave dipoles operating at 139.65 MHz. The primary aim of the array is to perform Interplanetary Scintillations (IPS) observations of radio sources to track large-scale solar wind perturbations within 1~AU. We describe the initial measurements of radio sources and the advances in the calibration of the antenna.

Gonzalez-Esparza, A.; Carrillo, A.; Andrade, E.; Jeyakumar, S.; Ananthakrishnan, S.; Praveenkumar, A.; Sankarasubramanian, G.; Sureshkumar, S.; Sierra, P.; Vazquez, S.; Perez-Enriquez, R.; Kurtz, S.

2005-12-01

9

A decametric wavelength radio telescope for interplanetary scintillation observations  

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

10

The Bubbler and Radio Scintillation  

NSDL National Science Digital Library

This is a lesson about the formation of plasma bubbles in Earth's ionosphere. Plasma bubbles cause stars to twinkle and radio signals from satellites to distort. Learners will build a model ionosphere in order to demonstrate and understand this process. This activity requires special materials including a laser pointer and silicon-based glue.

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. Then students learn general concepts about magnetic fields, leading into how radio waves are created and transmitted. Several demonstrations are performed to help students better understand these concepts. The lesson goal is for students to comprehend how the AM radios they will build during the associated activity function.

Techtronics Program

12

Interplanetary scintillation observations with the Cocoa Cross radio telescope  

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

13

Forecasting low-latitude radio scintillation with 3-D ionospheric plume models: 2. Scintillation calculation  

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 around and within the plumes. With the inclusion of the processes that determine the transport of plasma parallel to the geomagnetic field lines as well as transverse to them,

J. M. Retterer

2010-01-01

14

A Campaign Study of Ionospheric Scintillations Using Simultaneous Formosat-3\\/COSMIC Radio Occultation Observations and AFRL SCINDA Ground Scintillation Measurements  

Microsoft Academic Search

We report preliminary results from a campaign study of ionospheric scintillations using ionospheric radio occultation measurements by Formosat-3\\/COSMIC satellites and ground scintillation measurements by the Scintillation Network Decision Aid (SCINDA) network. Under the SCINDA project, scientists at the Air Force Research Laboratory (AFRL) have developed a sensor network for the purpose of monitoring low-latitude ionospheric total electron content (TEC) and

C. S. Lin; M. J. Starks; Y. Chu; S. Syndergarrd; K. M. Groves; S. Basu

2006-01-01

15

Outflow Structure of the Quiet Sun Corona Probed by Spacecraft Radio Scintillations in Strong Scattering  

NASA Astrophysics Data System (ADS)

Radio scintillation observations have been unable to probe flow speeds in the low corona where the scattering of radio waves is exceedingly strong. Here we estimate outflow speeds continuously from the vicinity of the Sun to the outer corona (heliocentric distances of 1.5-20.5 solar radii) by applying the strong scattering theory to radio scintillations for the first time, using the Akatsuki spacecraft as the radio source. Small, nonzero outflow speeds were observed over a wide latitudinal range in the quiet-Sun low corona, suggesting that the supply of plasma from closed loops to the solar wind occurs over an extended area. The existence of power-law density fluctuations down to the scale of 100 m was suggested, which is indicative of well-developed turbulence which can play a key role in heating the corona. At higher altitudes, a rapid acceleration typical of radial open fields is observed, and the temperatures derived from the speed profile show a distinct maximum in the outer corona. This study opened up a possibility of observing detailed flow structures near the Sun from a vast amount of existing interplanetary scintillation data.

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

2014-06-01

16

On the possibility to study the thin structure of external solar wind in decameter radio waves  

NASA Astrophysics Data System (ADS)

The Feynman path-integral technique is applied to calculate the cross-spectra and phase speed of weak interplanetary scintillations. The possibility to investigate the thin structure of the outer solar wind by simultaneous measurements of temporary scintillation spectra and the phase speed dispersion dependencies is considered for decameter radio waves.

Olyak, M. R.

2006-10-01

17

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

Microsoft Academic Search

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

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

2007-01-01

18

Holograms for shaping radio-wave fields  

Microsoft Academic Search

Holograms - diffractive elements - are designed and fabricated for shaping millimetre-wave radio fields. Methods for the synthesis of hologram elements are discussed and several beam shapes are tested: plane waves, radio-wave vortices and Bessel beams. Here we present an overview of the methods applied and results obtained with quasi-optical hologram techniques using both amplitude and phase holograms.

Janne Salo; Johanna Meltaus; Eero Noponen; Martti M. Salomaa; Anne Lönnqvist; Tomi Koskinen; Ville Viikari; Jussi Säily; Janne Häkli; Juha Ala-Laurinaho; Juha Mallat; Antti V. Räisänen

2002-01-01

19

UHF Radio Wave Attenuation Factor Database  

NASA Astrophysics Data System (ADS)

As is known each sea-going vessel is equipped with navigation, communication and other radio engineering facilities that serve to secure the safety of navigation and are chiefly operated at UHF-wave band. In developing these systems and calculating the energy potential for a necessary coverage range one should be well aware of the radio signal attenuation processes on a propagation path. The key parameter of this path is the (radio) wave attenuation factor V and its distance dependence V(R). A diversity of factors influencing the radio signal attenuation over the oceanic expanses, especially well pronounced and quite stable tropospheric ducts, and the lack of experimental data were the compelling reasons why the researchers of the Institute for Radiophysics and Electronics, NASU, had spent many years on comprehensive radiophysical investigations carried out in different regions of the Atlantic, Indian, Arctic and Pacific Oceans. The experimental data obtained allow creating the database of radio wave attenuation factor V.

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

2007-07-01

20

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

SciTech Connect

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

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

1989-02-01

21

Radio Wave Propagation in Tunnels.  

National Technical Information Service (NTIS)

This report examines the radio propagation model for narrow and long tunnels. Modal analysis is used to model the path gain in 2-D and 3-D rectangular tunnels and the coupling loss of L, T and cross tunnels. Modal attenuation is determined by the waveleng...

J. Lee, H. L. Bertoni

2000-01-01

22

Ionospheric modification by high power radio waves  

Microsoft Academic Search

Investigations using powerful, high frequency (HF) radio waves to temporarily modify the ionosphere are reviewed. Studies of the natural upper atmosphere have been conducted using these controlled, active experiments by observing the ionospheric response to HF induced perturbations. Other basic physics investigations have examined the ionosphere and its properties and behavior as a plasma. Topics examined include ionospheric heating, parametric

L. M. Duncan; W. E. Gordon

1982-01-01

23

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

24

Radio Waves in the Ionosphere  

NASA Astrophysics Data System (ADS)

Preface; 1. Introduction; 2. The basic equations; 3. The constitutive relations; 4. Propagation in a homogenous isotropic medium; 5. Propagation in a homogenous anisotropic medium. Magentoionic theory; 6. Properties of the Appleton-Hartree formula; 7. Definition of the reflection and transmission coefficients; 8. Reflection at a sharp boundary; 9. Slowly varying medium. The W.K.B solutions; 10. Ray theory for vertical incidence when the Earth's magnetic field is neglected; 11. Ray theory for oblique incidence when the Earth's magnetic field is neglected; 12. Ray theory for vertical incidence when the Earth's magnetic field is included; 13. Ray theroy for oblique incidence when the Earth's magnetic field is included; 14. The general problem of ray tracing; 15. The airy integral function and the Stokes phenomenon; 16. Linear gradient of electron density; 17. Various electron density profiles when the Earth's magnetic field is neglected; 18. Anisotropic media. Coupled wave-equations and W.K.B solution; 19. Application of coupled wave-equations; 20. The phase integral method; 21. Full wave solutions when the Earth's magnetic field is included; 22. Numerical methods for finding reflection coefficients; 23. Reciprocity.

Budden, K. G.

2009-06-01

25

Magnetotellurics and radio-wave interference sounding  

NASA Astrophysics Data System (ADS)

The plane harmonic electromagnetic fields are considered in the theory of magnetotelluric methods in the range of frequencies from 0.0001 Hz to 20 kHz. These fields are natural by their origin and contain information on the depths from tens of meters up to 100 km and more. The magnetotelluric soundings, which use the fields of radio stations, expand the frequency band almost up to 1 MHz and make it possible to study the depths from the first few meters. The method of radio-wave interference sounding supplements geoelectric prospecting on plane waves into the range of even higher frequencies (up to 100 MHz). In this case, the conduction and displacement currents become comparable, which makes it possible to distinguish objects both by their electrical conductivity and by their dielectric permittivity. For the two-layered model of a medium, there exist simple kinematic methods of data interpretation of a radio-interferometry sounding. Within multilayer, and especially horizontally heterogeneous, media, methods for solving equations of electrodynamics and inverse problems of geophysics are required. In the present paper, the foundations of the theory of radio-interferometry sounding, the methodology, its role in geoelectric prospecting, and the opportunities for the solution of geological problems are discussed.

Khmelevskoy, V. K.; Petrukhin, B. P.; Pushkarev, P. Yu.

2010-09-01

26

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

27

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

SciTech Connect

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

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

2012-10-10

28

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

NASA Technical Reports Server (NTRS)

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

Woo, Richard

1994-01-01

29

Radio star and satellite signal scintillation by E region irregularities: A case study  

NASA Astrophysics Data System (ADS)

We present the study of daytime scintillation due to E region irregularities at low latitudes from a set of simultaneous observations on June 3, 1993. The effects of these irregularities are clearly seen on (1) the 103 MHz signal of the radio star 3C 196 recorded at Rajkot and at Thaltej (near Ahmedabad, India), (2) the 244-MHz radio beacon of Fleetsat satellite (73 deg E) recorded at Ahmedabad, and (3) the ionosonde being operated at Ahmedabad. These observations provide an estimate of the irregularity patch with a spatial extent of around 400 km east-west and 80 km north-south. As the subionospheric points of the radio source and satellite observations are quite far apart, a study on the dynamics of these irregularities is also possible which indicates a southward movement of the patch. The drift speed of approx. 60 m/sec is calculated from the upper frequency roll off of the scintillation spectrum at 103 MHz. This is found to be consistent with earlier investigations of blanketing Es near magnetic equator.

Vats, Hari Om; Chandra, Harish; Deshpande, M. R.; Vyas, G. D.

1995-03-01

30

LUMPED PARAMATER RADIO WAVE PROPAGATION MODEL FOR STORM DRAIN PIPES  

Microsoft Academic Search

We conducted a measurement campaign to examine narrowband radio wave propagation characteristics of storm drain pipes (SDPs). The SDPs behave as multimode leaky waveguides for radio wave transmissions at higher frequencies. We derive a model for radio frequency (RF) propagation through concrete SDPs. We also observe attenuation in RF transmissions at 2.4 - 2.5 GHz and at 5.2 GHz by

Ivan Howitt; Jumanah Khan; Safeer Khan

31

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

NASA Astrophysics Data System (ADS)

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 ? 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.; Chashei, I. V.; Bird, M. K.; Pätzold, M.; Tellmann, S.

2010-03-01

32

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

33

Radio Wave Emission from the Outer Planets Before Cassini  

Microsoft Academic Search

We review observations and theories of radio wave emissions from the outer planets. These include radio emissions from the auroral regions and from the radiation belts, low-frequency electromagnetic emissions, and atmospheric lightning. For each of these emissions, we present in more details our knowledge of the Saturn counterpart, as well as expectations for Cassini. We summarize the capabilities of the

P. Zarka; W. S. Kurth

2005-01-01

34

On Microwave Radio Scintillation Effects and Space Weather Impacts on Electric Power Supply Systems in Middle Latitudes  

Microsoft Academic Search

In this paper results of morphological studies and investigations on revealing of main characteristics of ionospheric scintillation effects experienced for microwave radio signals for the Space-Earth path, its impacts on navigation and communication systems, dependence on the solar and geomagnetic activity, geophysical and other processes\\/factors are briefly provided to help system designers who are involved in the activities related to

E. S. Babayev; A. M. Hashimov; A. B. Asgarov; N. A. Yusifbeyli; P. N. Shustarev

2006-01-01

35

Scintillation modeling using in situ data  

Microsoft Academic Search

Satellite in situ measurements of plasma (electron) density fluctuations provide direct information about the structure and morphology of irregularities that are responsible for scintillation of radio waves on transionospheric links. When supplemented with the ionosphere model and irregularity anisotropy model, they can be applied to model morphology of scintillation provided a suitable propagation model is used. In this paper we

A. W. Wernik; L. Alfonsi; M. Materassi

2007-01-01

36

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

37

Evidence for nonlinear wave-wave interactions in solar type III radio bursts  

NASA Technical Reports Server (NTRS)

Evidence is presented that nonlinear wave-wave interactions occur in type III solar radio bursts. Intense, spiky Langmuir waves are observed to be driven by electron beams associated with type III solar radio bursts in the interplanetary medium. Bursts of 30-300 Hz (in the spacecraft frame) waves are often observed coincident in time with the most intense spikes of the Langmuir waves. These low-frequency waves appear to be long-wavelength ion acoustic waves, with wavenumber approximately equal to the beam resonant Langmuir wavenumber. Three possible interpretations of these observations are considered: modulational instability, parametric decay of the parent Langmuir waves to daughter ion acoustic and Langmuir waves, and decay to daughter electromagnetic waves and ion acoustic waves.

Lin, R. P.; Levedahl, W. K.; Lotko, W.; Gurnett, D. A.; Scarf, F. L.

1986-01-01

38

Coincidently Searching for Gravitational Waves and Low Frequency Radio Transients  

NASA Astrophysics Data System (ADS)

The transient sky has become an important area of astrophysical study, especially with the appearance of recent fast transients, but little is known about the sources of these transients. One possible approach which can shed light on this area is multi-messenger astronomy using gravitational waves and prompt emission meter-wavelength radio to observe fast transients. This is made possible with gravitational-wave detectors such as LIGO, VIRGO, and GEO (IndIGO and KAGRA proposed or under construction) and phased-array radio-telescopes such LWA, LOFAR, LoFASM, and MWA. This talk presents a method for coincidence of gravitational wave and meter-wavelength radio observations to enable multi-messenger astronomy and discusses the optimization of gravitational-wave and radio sensitivities to attain effective combined observational sensitivities. It is shown that coincidence provides a 52.9% increase to the sensitivity distance for LIGO and a 200% increase to the SNR of radio arrays for particular cases.

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

2014-01-01

39

Physics-based forecasts of equatorial radio scintillation for the Communication and Navigation Outage Forecasting System (C\\/NOFS)  

Microsoft Academic Search

The plans for producing long-term (6–24 hour) forecasts of equatorial plasma structure and radio scintillation for the Communication and Navigation Outage Forecasting System (C\\/NOFS) program are described. We discuss the calculations and computer models required to represent the physics of the phenomena pertinent to the C\\/NOFS mission. We describe the means by which the models will be integrated into a

John M. Retterer

2005-01-01

40

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

41

Excitation of parametric instabilities by radio waves in the ionosphere.  

NASA Technical Reports Server (NTRS)

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

Fejer, J. A.; Leer, E.

1972-01-01

42

On the Possibility of Study of the External Solar Wind Thin Structure in Decameter Radio Waves  

NASA Astrophysics Data System (ADS)

The purpose of this work is to develop the research technique of the thin structure of outer solar wind in decameter waves. The extended medium model and Feynman path-integral method were applied for calculations of the cross - spectra of weak interplanetary scintillations. The temporary spectra W(f) and phase speed dispersion dependencies V(f) for the spherically symmetric (curves 1) and two-high-speed (curves 2) models of solar wind were calculated. The meanings of solar wind parameters were chosen so that the differences of temporary spectra for two models were minimal and laid within the limits of probable measurements errors ([S:f:S][Author ID2: at Fri Jul 14 10:28:00 2006 ] F[Author ID2: at Fri Jul 14 10:28:00 2006 ]ig. 1). It is shown that the supervision of scintillations on two spatially carried antennas and study of dispersion dependence of phase speed will allow to notice the presence of the accelerated flows on a beam of sight when the measurements on one antenna do not give the unequivocal answer to the question whether the flows of solar wind with various speeds are present in external areas of interplanetary medium. It is shown that by using of simultaneous measurements of temporary spectra and dispersion dependences of phase speed the detection of fast and slow solar wind flows and the definition of their parameters are possible in decameter radio waves.

Olyak, M. R.

2006-08-01

43

From Millihertz to Tetrahertz: Radio Waves in Marine Communication and Navigation.  

National Technical Information Service (NTIS)

Classification of radio waves by their manner of propagation is discussed including the influence of the earth's magnetic field on this process. Radio waves of specific frequency ranges are also examined with special attention to the applications of ultra...

M. P. Dolukhanov

1971-01-01

44

Absorption refraction and scintillation measurements at 4700 mc\\/s with a travelling-wave tube radiometer  

Microsoft Academic Search

By means of radio astronomy techniques, measurements of atmospheric ; absorption, refraction, and scintillation were made at C band (4700 Mc\\/s), with ; the sun as a source of radiofrequency energy. The measurements were made with a ; comparison-type radiometer, using travelingwave tubes, a tuned radio frequency ; receiver, and an altazimuth antenna mount. The average solar temperatures ; recorded

J. P. Castelli; J. Aarons; C. Ferioli; J. Casey

1959-01-01

45

Cassini Radio Science Observations of Density Waves in Saturn's Rings  

Microsoft Academic Search

Saturn's ring system is an elegant celestial mechanical laboratory for studying the interactions between a host of small and large moons, and the rings themselves. Resonances between the satellites and the ring particles result in spiral density waves whose detailed characteristics can be used to determine the physical properties of the rings. Over the past year, the Cassini Radio Science

C. A. McGhee; R. G. French; N. J. Rappaport; E. A. Marouf; R. Dawson; K. Stack

2006-01-01

46

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

47

Time-dependent scintillations of pulsed Gaussian-beam waves propagating in generalized atmospheric turbulence  

NASA Astrophysics Data System (ADS)

Expressions for both the temporal first- and second-order intensity moments of pulsed Gaussian-beam waves passing through generalized atmospheric turbulence are derived under the near- and far-field approximations, respectively. With the help of these expressions, the time-dependent scintillation behavior of optical pulses during propagation in generalized atmospheric turbulence is examined by numerical calculations. The effects that the spectral index of the spatial power spectrum of refractive-index fluctuations has on the temporal dependence of pulse scintillations are analyzed under the condition that the generalized plane-wave Rytov variance is specified as a constant for various spectral indices. It is shown that both the near- and far-field scintillations of an optical pulse are less dependent on time as the spectral index becomes smaller, indicating that there does exist a significant difference between the time-dependent scintillation behavior of an optical pulse in non-Kolmogorov turbulence and that in the Kolmogorov one. The obtained results are helpful for understanding the time-dependent scintillations of optical pulses propagating in generalized atmospheric turbulence and hence are useful for practical applications.

Chen, Chunyi; Yang, Huamin; Kavehrad, Mohsen; Lou, Yan

2014-09-01

48

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

49

VHF radio scintillations at Rajkot - A station near the crest of the equatorial anomaly in India  

NASA Astrophysics Data System (ADS)

The salient features of scintillation occurrence, scintillation depth, and rate of fluctuation of amplitude near the crest of the Appleton anomaly in the Indian zone are identified using amplitude scintillations of FLEETSAT signals at 244 MHz at Rajkot for a period of increasing solar activity during 1987-1989. VHF scintillation at Rajkot is found to be mainly a nighttime phenomenon, predominantly in the premidnight period in equinox and winter seasons and in the postmidnight period in summer. In equinox and winter, scintillation occurrence increases with sunspot number, while in summer it decreases for moderate levels and thereafter is almost independent of sunspot activity. Nighttime scintillation occurrence is suppressed by magnetic activity in equinox and winter seasons, while in summer this trend is reversed.

Mathew, Boby; Iyer, K. N.; Pathan, B. M.

1992-08-01

50

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

2013-01-01

51

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

SciTech Connect

The authors present results from a prototype high pressure xenon gas scintillation drift chamber using a novel wave-shifter fiber readout scheme. They have measured the primary scintillation light yield to be one photon per 76 {+-} 12 eV deposited energy. They present initial results of our chamber for the two-interaction separation (< 4 mm in the drift direction, {approximately} 7 mm orthogonal to the drift); for the position resolution (< 400 {mu}m rms in the plane orthogonal to the drift direction); and for the energy resolution ({Delta}E/E < 6% FWHM at 122 keV).

Parsons, A.; Edberg, T.K.; Sadoulet, B.; Weiss, S.; Wilkerson, J.; Hurley, K.; Lin, R.P. (California Univ., Berkeley, CA (USA). Dept. of Physics); Smith, G. (Lawrence Berkeley Lab., CA (USA))

1990-04-01

52

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

53

Electron Acceleration by High Power Radio Waves in the Ionosphere  

NASA Astrophysics Data System (ADS)

At the highest ERP of the High Altitude Auroral Research Program (HAARP) facility in Alaska, high frequency (HF) electromagnetic (EM) waves in the ionosphere produce artificial aurora and electron-ion plasma layers. Using HAARP, electrons are accelerated by high power electrostatic (ES) waves to energies >100 times the thermal temperature of the ambient plasma. These ES waves are driven by decay of the pump EM wave tuned to plasma resonances. The most efficient acceleration process occurs near the harmonics of the electron cyclotron frequency in earth's magnetic field. Mode conversion plays a role in transforming the ES waves into EM signals that are recorded with ground receivers. These diagnostic waves, called stimulated EM emissions (SEE), show unique resonant signatures of the strongest electron acceleration. This SEE also provides clues about the ES waves responsible for electron acceleration. The electron gas is accelerated by high frequency modes including Langmuir (electron plasma), upper hybrid, and electron Bernstein waves. All of these waves have been identified in the scattered EM spectra as downshifted sidebands of the EM pump frequency. Parametric decay is responsible low frequency companion modes such as ion acoustic, lower hybrid, and ion Bernstein waves. The temporal evolution of the scattered EM spectrum indicates development of field aligned irregularities that aid the mode conversion process. The onset of certain spectral features is strongly correlated with glow plasma discharge structures that are both visible with the unaided eye and detectable using radio backscatter techniques at HF and UHF frequencies. The primary goals are to understand natural plasma layers, to study basic plasma physics in a unique ``laboratory with walls,'' and to create artificial plasma structures that can aid radio communications.

Bernhardt, Paul

2012-10-01

54

Remote personal health monitoring with radio waves  

NASA Astrophysics Data System (ADS)

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

Nguyen, Andrew

2008-05-01

55

Radio frequency wave reducing material and methods for manufacturing same  

US Patent & Trademark Office Database

An improved radio frequency wave attenuating wall (ceiling or floor) or door material comprises a laminated structure having as an integral part thereof one or more layers of a viscoelastic material which also functions as a glue and one or more electrically conducting layers. An electrically conducting material such as tape or a formed metal channel provides an electrical connection between the electrically conducting material and an exposed outer surface of the laminated structure. In one embodiment the electrically conducting material is paint. In one embodiment, standard wallboard, typically gypsum, comprises the external surfaces of the laminated structure and one or more conductive layers are constructed between the gypsum exterior. In one embodiment, the conducting layer material is selected to provide physical security in addition to radio frequency wave attenuation. The construction is such that acoustical attenuation is also achieved.

2011-10-04

56

Radio observations of atmospheric gravity waves with Callisto  

NASA Astrophysics Data System (ADS)

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

Monstein, C.

2013-12-01

57

Data compression for the Cassini radio and plasma wave instrument  

NASA Technical Reports Server (NTRS)

The Cassini Radio and Plasma Wave Science experiment will employ data compression to make effective use of the available data telemetry bandwidth. Some compression will be achieved by use of a lossless data compression chip and some by software in a dedicated 80C85 processor. A description of the instrument and data compression system are included in this report. Also, the selection of data compression systems and acceptability of data degradation is addressed.

Farrell, W. M.; Gurnett, D. A.; Kirchner, D. L.; Kurth, W. S.; Woolliscroft, L. J. C.

1993-01-01

58

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

59

PhET: Radio Waves and 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.

2009-11-25

60

Magellan Radio Occultation Measurements of Atmospheric Waves on Venus  

Microsoft Academic Search

Radio occultation experiments were conducted at Venus on three consecutive orbits of the Magellan spacecraft in October 1991. Each occultation occurred over the same topography (67°N, 127°E) and at the same local time (22h5m), but the data are sensitive to zonal variations because the atmosphere rotates significantly during one orbit. Through comparisons between observations and predictions of standard wave theory,

David P. Hinson; Jon M. Jenkins

1995-01-01

61

Upper limits on gravitational wave emission from 78 radio pulsars  

Microsoft Academic Search

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

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

2007-01-01

62

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

63

Optical detection of radio waves through a nanomechanical transducer  

NASA Astrophysics Data System (ADS)

Low-loss transmission and sensitive recovery of weak radio-frequency and microwave signals is a ubiquitous challenge, crucial in radio astronomy, medical imaging, navigation, and classical and quantum communication. Efficient up-conversion of radio-frequency signals to an optical carrier would enable their transmission through optical fibres instead of through copper wires, drastically reducing losses, and would give access to the set of established quantum optical techniques that are routinely used in quantum-limited signal detection. Research in cavity optomechanics has shown that nanomechanical oscillators can couple strongly to either microwave or optical fields. Here we demonstrate a room-temperature optoelectromechanical transducer with both these functionalities, following a recent proposal using a high-quality nanomembrane. A voltage bias of less than 10 V is sufficient to induce strong coupling between the voltage fluctuations in a radio-frequency resonance circuit and the membrane's displacement, which is simultaneously coupled to light reflected off its surface. The radio-frequency signals are detected as an optical phase shift with quantum-limited sensitivity. The corresponding half-wave voltage is in the microvolt range, orders of magnitude less than that of standard optical modulators. The noise of the transducer--beyond the measured Johnson noise of the resonant circuit--consists of the quantum noise of light and thermal fluctuations of the membrane, dominating the noise floor in potential applications in radio astronomy and nuclear magnetic imaging. Each of these contributions is inferred to be when balanced by choosing an electromechanical cooperativity of with an optical power of 1 mW. The noise temperature of the membrane is divided by the cooperativity. For the highest observed cooperativity of , this leads to a projected noise temperature of 40 mK and a sensitivity limit of . Our approach to all-optical, ultralow-noise detection of classical electronic signals sets the stage for coherent up-conversion of low-frequency quantum signals to the optical domain.

Bagci, T.; Simonsen, A.; Schmid, S.; Villanueva, L. G.; Zeuthen, E.; Appel, J.; Taylor, J. M.; Sørensen, A.; Usami, K.; Schliesser, A.; Polzik, E. S.

2014-03-01

64

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

65

Scattering of radio frequency waves by blobs in tokamak plasmas  

SciTech Connect

The density fluctuations and blobs present in the edge region of magnetic fusion devices can scatter radio frequency (RF) waves through refraction, reflection, diffraction, and coupling to other plasma waves. This, in turn, affects the spectrum of the RF waves and the electromagnetic power that reaches the core of the plasma. The usual geometric optics analysis of RF scattering by density blobs accounts for only refractive effects. It is valid when the amplitude of the fluctuations is small, of the order of 10%, compared to the background density. In experiments, density fluctuations with much larger amplitudes are routinely observed, so that a more general treatment of the scattering process is needed. In this paper, a full-wave model for the scattering of RF waves by a blob is developed. The full-wave approach extends the range of validity well beyond that of geometric optics; however, it is theoretically and computationally much more challenging. The theoretical procedure, although similar to that followed for the Mie solution of Maxwell's equations, is generalized to plasmas in a magnetic field. Besides diffraction and reflection, the model includes coupling to a different plasma wave than the one imposed by the external antenna structure. In the model, it is assumed that the RF waves interact with a spherical blob. The plasma inside and around the blob is cold, homogeneous, and imbedded in a uniform magnetic field. After formulating the complete analytical theory, the effect of the blob on short wavelength electron cyclotron waves and longer wavelength lower hybrid waves is studied numerically.

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

2013-05-15

66

Propagation of Radio Frequency Waves in a Weakly Ionized Gas  

NASA Astrophysics Data System (ADS)

Long distance communication and diagnostics of the space environment rely on an understanding of the refraction, phase alteration and attenuation of electromagnetic waves in the ionosphere and plasmasphere. The nature of wave propagation in a spatially inhomogeneous plasma was explored using a numerical implementation of the eikonal approach(L. D. Landau and E. M. Lifshitz, Electrodynamics of Continuous Media), (Pergamon Press 1960), pp. 269-279. . The calculation was validated by comparing numerical results with analytic solutions( K. G. Budden, Radio Waves In the Ionosphere), (Cambridge University Press, 1966), pp. 179-182. for a horizontally stratified plasma with linear and exponential variations in the density. The treatment was extended to treat arbitrary plasma distributions. Ray trajectories and attentuation are presented for typical ionospheric profiles, exhibiting non-monotonic density variations, and profiles associated with a plasma generated by injection of a relativistic electron beam. USE ONLY)

Lockwood, Nathaniel P.; Bailey, Wm. F.

2000-10-01

67

Ion species mix and ion density measurements using radio frequency waves  

Microsoft Academic Search

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

George Wilder Watson III

2003-01-01

68

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

69

Ionospheric and Tropospheric Scintillations of a Radio Star at Zero to Five Degrees of Elevation.  

National Technical Information Service (NTIS)

Using Cygnus A as the source, a multi-frequency study of both scintillation rate and index was made in 1961 and 1962. Using an 84 ft parabola, simultaneous observations were made at 63, 112, 225, 1200, and 2980 Mc/s with angles of elevation from 0 to 5 de...

J. P. Castelli J. Aarons H. M. Silverman

1964-01-01

70

Flare Generated Coronal Fast Wave Trains of Decimetric Radio Pulsations  

NASA Astrophysics Data System (ADS)

The 22 minutes lasting interval of broadband dm-radio pulsations observed simultaneously during a decay phase of the June 6, 2000 flare by the Brazilian Solar Spectroscope (BSS) and Ondrejov radiospectrograph in frequency range 1200-4500 MHz has been analyzed. We have realized that dominant periods (32-64 s) belong to fast wave trains with a tadpole pattern in their wavelet power spectra. The whole time interval contains series of about 4 wave trains. These trains propagate in whole frequency range 1200-4500 MHz. The propagation of individual trains at lower levels of the solar atmosphere (higher frequencies) is different from propagation of individual trains at higher ones (lower frequencies). The wave trains at the same frequencies but in different time subintervals have some common as well as different properties. The main statistical parameters (periodical, quasi-periodical and decay phase) of these wave trains in their wavelet power spectra have been studied and the first results will be presented and discussed.

Meszarosova, H.; Sawant, H. S.; Cecatto, J. R.; Rybak, J.; Karlicky, M.; Fernandes, F. C. R.; Jiricka, K.; Andrade, M. C.

2008-09-01

71

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

72

Analysis of the defocusing of radio waves in the inosphere due to the influence of an intense radio-frequency radiation field  

Microsoft Academic Search

This paper reports on strong attenuation of probe radio waves that have been observed when the waves propagate through the ionosphere as it is being disturbed by an intense radio wave. Experimental results are compared with theory. The effect observed is shown to be due to the defocusing of the probe wave propagating through an artificial ionospheric lens which is

G. N. Boiko; Y. S. Dimant; S. F. Golyan; A. V. Gurevich; V. Y. Kim; V. V. Vaskov; V. A. Zyuzin

1986-01-01

73

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

74

Solar Corona and plasma effects on Radio Frequency waves  

NASA Astrophysics Data System (ADS)

Solar corona (plasma) effects on radio signal waves for three different frequency bands S (2.3 GHz), X (8.4 GHz), and Ka (32 GHz), currently used to track probes in the solar system, have been computed using different models of the total electron content (TEC) along the propagation path between the Earth and Mars. The Earth-Mars-Sun configuration has been obtained from the planetary ephemerides DE421 (using SPICE kernels) for the period from September 2004 to September 2006. This configuration is expressed as a function of the Sun-Earth-Probe (SEP) angles (the probe being in close orbit to Mars). We used the TEC values provided by the different models proposed in the literature in order to estimate the TEC along the propagation path (STEC, for Slant TEC). From these model-dependent STEC estimates, the time delay on the wave propagation as well as the associated frequency shift with a 10 seconds sampling time have been obtained for each of the three frequency bands. For the X-band mostly used in radio science, we have obtained estimates differing by up to several orders of magnitude due to the different STEC values derived from different models of TEC. For example, if the propagation path passes near the Sun such that SEP angle is 1.55° the STEC is ranging from 4.6x1020 electron/m2 to 6.07x1016 electron/m2, which corresponds to a time delay range between 0.87 ?s and 1.15x10-4 ?s, respectively. For SEP angles between 2° and 8°, the range of the different time delay values reduces to 2.8x10-1 ?s and becomes as small as 1.6x10-2 ?s for SEP angles larger than 8° (1x10-2 ?s is about the order of magnitude of the radioscience instrument precision). These results show that the correction of the solar corona effect on radio frequency waves can be reliably done on usual X-band tracking data of spacecraft for SEP angles >12°, but should be use with caution for lower SEP angles, especially lower than 2°.

Nkono, C.; Rosenblatt, P.; Dehant, V. M.

2009-12-01

75

Simultaneous rocket probe, scintillation, and incoherent scatter radar observations of irregularities in the auroral zone ionosphere  

Microsoft Academic Search

Wideband satellite scintillation and Chatanika incoherent scatter radar observations were made to study the properties of high-latitude nighttime irregularities in the auroral zone and the effects on radio wave transmission. With regard to the observed power law dependence of the irregularities, a turbulent process seems to occur; in addition, the power law indexes determined both from rocket probe and scintillation

M. C. Kelley; K. D. Baker; J. C. Ulwick; C. L. Rino; M. J. Baron

1980-01-01

76

Solar and geomagnetic activity control on equatorial VHF Scintillations in the Indian region  

NASA Astrophysics Data System (ADS)

The ionospheric plasma density irregularities are responsible for scintillation of trans-equatorial radio signals. VHF radio wave Scintillation technique is extensively used to study plasma density irregularities of sub-km size. A ground network of 14 stations were operated by Indian Institute of Geomagnetism (and one station at Waltair) under All India coordinated Programme of Ionospheric and Thermospheric Studies (AICPITS), monitoring amplitude scintillations of 244/250 MHz signal from FLEETSAT (73° E) in India for more than a solar cycle. Effect of solar and geomagnetic activity on scintillation is studied in detail. Using long series of simultaneous amplitude scintillation data at different stations for the period 1989-2000, solar cycle association of scintillation is studied. Boundary of the equatorial belt of scintillation is determined using the entire network data. Geomagnetic control on the width of the scintillation belt is studied from the latitudinal variations of scintillation occurrence separately for geomagnetic quiet and disturbed days and also for the groups of days with low, medium and high Kp values. Kp and Ap indices, characterizing the geomagnetic activity which are shown extensively related to the dynamic properties of the plasma from the sun, are examined for their association with the scintillations. It is noticed that with increase in geomagnetic activity at low and equatorial regions scintillation occurrence is inhibited. Scintillation activity under different magnetic storm conditions is studied using Dst index and classification of the various geomagnetic storms into 3 types of Aaron's criteria (Radio Science,1991), satisfying in about 70 % of cases.

Banola, S.; Maurya, R. N.; Prasad, D. S. V.; Rama Rao, P. S. V.

77

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

PubMed

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 degrees 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. PMID:19293468

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

2009-04-01

78

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

79

An Approach to Measuring the Direction of Arrival of Radio Waves in the Presence of Wave Interference.  

National Technical Information Service (NTIS)

When two radio waves are reflected from the ionosphere and arrive at an antenna via two different elevation angles, the measurement of the angle of arrival of the stronger wave is influenced by the weaker interfering wave. This phenomenon is examined in d...

S. E. Cooper

1968-01-01

80

Upper limits on gravitational wave emission from 78 radio pulsars  

SciTech Connect

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 2.6x10{sup -25} for PSR J1603-7202, and the equatorial ellipticity of PSR J2124-3358 is less than 10{sup -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.; Anderson, S. B.; Araya, M.; Armandula, H.; Ballmer, S.; Barish, B. C.; Bhawal, B.; Billingsley, G.; Black, E.; Blackburn, K.; Bork, R.; Boschi, V.; Busby, D.; Cardenas, L.; Cepeda, C.; Chatterji, S.; Coyne, D. [LIGO-California Institute of Technology, Pasadena, California 91125 (United States)] (and others)

2007-08-15

81

Radio and thermoluminescence and energy transfer processes in Ce 3+(Tb 3+)-doped phosphate scintillating glasses  

Microsoft Academic Search

Ce3+ and Tb3+-doped Na(K)-Gd phosphate glasses were synthesized and their radio-, photo- and thermoluminescence properties were investigated. Increased radioluminescence efficiency with respect to Gd-free glass matrix has been achieved at Gd concentrations above 20mol%. This is explained by efficient capture of thermalised electrons and holes in the Gd3+-sublattice resulting in the formation of Gd3+ excited states followed by Gd3+-Gd3+ energy

M. Nikl; J. A. Mares; E. Mihokova; K. Nitsch; N. Solovieva; V. Babin; A. Krasnikov; S. Zazubovich; M. Martini; A. Vedda; P. Fabeni; G. P. Pazzi; S. Baccaro

2001-01-01

82

Radio and Plasma Wave Science Opportunities Afforded by the Jupiter Icy Moons Orbiter  

Microsoft Academic Search

The Galileo mission demonstrated the extensive and varied interactions between the Jovian magnetosphere and the icy Galilean satellites. In particular, the Galileo plasma wave investigation showed the surprisingly complex array of plasma and radio wave phenomena accompanying Ganymede's magnetosphere, evidence of an extensive magnetospheric interaction at Europa, and a weaker yet highly variable interaction at Callisto. The plasma wave observations

W. S. Kurth; D. A. Gurnett; W. M. Farrell; M. D. Desch; M. L. Kaiser; P. Zarka; A. Lecacheux; P. Canu; S. J. Bolton; J. E. Wahlund; L. G. Blomberg; S. D. Bale; M. Moncuquet

2003-01-01

83

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

NASA Astrophysics Data System (ADS)

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

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

2007-03-01

84

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

Microsoft Academic Search

We present detailed in situ observations from the ISEE 3 spacecraft of energetic electrons, plasma waves, and radio emission for the type III solar radio burst of 1979 February 17. The reduced one-dimensional distribution function f (v) of the electrons is constructed as a function of time. Since the faster electrons arrive before the slower ones, a bump on tail

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

1981-01-01

85

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

Microsoft Academic Search

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

Parisa Noorishad; Sarod Yatawatta

2011-01-01

86

Density Waves in Saturn's Rings from Cassini Radio Occultations  

Microsoft Academic Search

The Cassini Radio Science Team conducted a set of optimized diametric occultations by Saturn and its rings from May to September 2005, providing 11 separate probes of Saturn's ionosphere and atmosphere, and 12 optical depth profiles of the complete ring system. Each event was observed by the stations of the Deep Space Net (DSN) at three radio frequencies (S, X,

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

2005-01-01

87

Comparative Equatorial Scintillation Morphology--American and Pacific Sectors.  

National Technical Information Service (NTIS)

This report examines the severity of radio-wave amplitude scintillation measured at two stations near the equator, but far apart in longitude: Kwajalein Atoll in the Marshall Islands, and Ancon, Peru. The data used are observations of the Wideband satelli...

R. C. Livingston

1978-01-01

88

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

Microsoft Academic Search

Ionospheric small-scale waves in the F region, initiated by heating facilities in Nizhniy Novgorod, have been studied by the method of field-aligned scattering of diagnostic HF radio signals. Experimental data have been obtained on the radio path Kiev–N. Novgorod–St. Petersburg during heating campaigns with heater radiated power ERP = 20 MW and 100 MW. Observations of scattered HF signals have

N. F. Blagoveshchenskaya; M. Yu. Chernyshev; V. A. Kornienko

1998-01-01

89

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

Microsoft Academic Search

Ionospheric small-scale waves in the F region, initiated by heating facilities in Nizhniy Novgorod, have been studied by the method of field-aligned scattering of diagnostic HF radio signals. Experimental data have been obtained on the radio path Kiev-N. Novgorod-St. Petersburg during heating campaigns with heater radiated power ERP = 20 MW and 100 MW. Observations of scattered HF signals have

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

1998-01-01

90

Electron acceleration and type II radio emission at quasi-parallel shock waves  

NASA Astrophysics Data System (ADS)

Solar type II radio bursts are interpreted as the radio signature of shock waves travelling through the solar corona. Some of these shock waves are able to enter into the interplanetary medium and are observed as interplanetary type II bursts. The nonthermal radio emission of these bursts indicates that electrons are accelerated up to superthermal and/or relativistic velocities at the corresponding shocks. Plasma wave measurements at interplanetary shock waves support the assumption that the fundamental type II radio emission is generated by wave-wave interactions of electron plasma waves and ion acoustic waves and that the source region is located near the transition region of the shock. Therefore, the instantaneous bandwidth of type II bursts should reflect the density jump across the shock. Comparing the theoretically predicted density jump of coronal shock waves (Rankine-Hugoniot relations) and the measured instantaneous bandwidth of solar type II radio bursts it is appropriate to assume that these bursts are generated by weak supercritical quasi-parallel shock waves. Two different mechanisms for the accelaration of electrons at this kind of shock waves are investigated in the form of test particle calculations in given magnetic and electric fields. These fields have been extracted from in-situ measurements at the quasi-parallel region at Earth’s bow shock, which showed large amplitude magnetic field fluctuations (so-called SLAMS: Short Large Amplitude Magnetic Field Structures) as constituent parts. The first mechanism treats these structures as strong magnetic mirrors, at which charged particles are reflected and accelerated. Thus, thermal electrons gain energy due to multiple reflections between two approaching SLAMS. The second mechanism shows that it is possible to accelerate electrons inside a single SLAMS due to a noncoplanar component of the magnetic field in these structures. Both mechanism are described in the form of test particle calculations, which are supplemented by calculations according to adiabatic theory. The results are discussed for circumstances in the solar corona and in interplanetary space.

Claßen, H.-T.; Mann, G.

1998-01-01

91

Electron acceleration and type II radio emission at quasi-parallel shock waves  

NASA Astrophysics Data System (ADS)

Solar type II radio bursts are interpreted as the radio signature of shock waves travelling through the solar corona. Some of these shock waves are able to enter into the interplanetary medium and are observed as interplanetary type II bursts. The nonthermal radio emission of these bursts indicates that electrons are accelerated up to superthermal and/or relativistic velocities at the corresponding shocks. Plasma wave measurements at interplanetary shock waves support the assumption that the fundamental type II radio emission is generated by wave-wave interactions of electron plasma waves and ion acoustic waves and that the source region is located near the transition region of the shock. Therefore, the instantaneous bandwidth of type II bursts should reflect the density jump across the shock. Comparing the theoretically predicted density jump of coronal shock waves (Rankine-Hugoniot relations) and the measured instantaneous bandwidth of solar type II radio bursts it is appropriate to assume that these bursts are generated by weak supercritical quasi-parallel shock waves. Two different mechanisms for the accelaration of electrons at this kind of shock waves are investigated in the form of test particle calculations in given magnetic and electric fields. These fields have been extracted from in-situ measurements at the quasi-parallel region at Earth’s bow shock, which showed large amplitude magnetic field fluctuations (so-called SLAMS: Short Large Amplitude Magnetic Field Structures) as constituent parts. The first mechanism treats these structures as strong magnetic mirrors, at which charged particles are reflected and accelerated. Thus, thermal electrons gain energy due to multiple reflections between two approaching SLAMS. The second mechanism shows that it is possible to accelerate electrons inside a single SLAMS due to a noncoplanar component of the magnetic field in these structures. Both mechanism are described in the form of test particle calculations, which are supplemented by calculations according to adiabatic theory. The results are discussed for circumstances in the solar corona and in interplanetary space.

Claßen, H.-T.; Mann, G.

1996-01-01

92

Wave propagation and earth satellite radio emission studies  

NASA Technical Reports Server (NTRS)

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

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

1974-01-01

93

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

NASA Technical Reports Server (NTRS)

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 the spacecraft telemetry link is capable of transmitting back to the Earth. Thus, techniques of on-board data compression and data reduction are important. The RPWS instrument has one processor dedicated to data compression tasks.

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

1993-01-01

94

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

NASA Technical Reports Server (NTRS)

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 the spacecraft telemetry link is capable of transmitting back to the Earth. Thus, techniques of on-board data compression and data reduction are important. The RPWS instrument has one processor dedicated to data compression tasks.

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

1993-01-01

95

Approach warning system for snowplow using aerial-high-power ultrasonic wave with radio wave  

NASA Astrophysics Data System (ADS)

An approach warning system for a snowplow and guide was developed by using aerial-high-power ultrasonic transducer. To be robust against some serious factors in winter, ultrasonic signal and radio one were combined on the system, and the flat face side of stepped circular vibrating plate was utilized as a radiation plate. The ultrasonic wave radiated from the flat face side still had a better directivity, and the flat face had advantage to prevent bad influences from water, snow or ice. From experiment results, when double transducers were set on both sides of roof of snowplow, this system was able to be measure distance between a guide and snowplow in whole of controlled area.

Manabu, Aoyagi; Yuta, Amagi; Hiroaki, Miura; Okeya, Ryota; Hideki, Tamura; Takehiro, Takano

2012-05-01

96

Kelvin wave variability near the equatorial tropopause observed in GPS radio occultation measurements  

Microsoft Academic Search

Temperature fields in the equatorial upper troposphere and lower stratosphere, derived from GPS radio occultation measurements for 2001-2002, show evidence for planetary-scale Kelvin waves. These waves have a characteristic eastward phase tilt with height and typical vertical wavelengths of ~4-8 km. The Kelvin waves exhibit coherent vertical structure over ~12-25 km, with maximum amplitudes near the tropical tropopause (~17 km).

William J. Randel; Fei Wu

2005-01-01

97

Prospects for optical and radio-wave remote imaging of high latitude exospheric processes  

NASA Technical Reports Server (NTRS)

The paper examines the use of optical, radio-wave, and extreme UV imaging to study the distribution of magnetospheric plasma continuously and thereby study magnetospheric global dynamics. Optical imaging of the terrestrial exosphere at FUV and EUV wavelengths is discussed in the light of evidence from recent observational campaigns. Radio imaging of the earth's magnetosphere is shown to provide good instantaneous images of the plasma from beyond 4 earth radii. Optical imaging is examined with respect to the study of other planetary exospheres, and the technique is shown to depend on the ability to do normal incidence optics in the EUV. The Cassini radio-uplink experiment is examined as an example of radio-wave tomography which can provide geometry-based tomographic montages to image the heliosphere and the planetary magnetospheres.

Chiu, Y. T.

1992-01-01

98

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.

99

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

PubMed

We report the discovery of radio-wave-induced red emission of OH Meinel rotation-vibrational bands at 629.79 nm. These are the first measurements of artificial aurora below 100 km. We believe that the 629.79-nm OH emission was due to radio-wave focusing by sporadic ionization clouds near 80-85 km altitude, thus giving a technique to visualize the low-altitude sporadic ionization and providing insight into ionospheric interactions at these low altitudes. PMID:15783973

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

2005-03-11

100

Phase fluctuations of radio waves experiencing total reflection from a randomly inhomogeneous plasma layer  

NASA Astrophysics Data System (ADS)

We examine the problem of small-angle scattering of radio waves experiencing total reflection from a randomly inhomogeneous layer of plasma. We consider the waves to be normally incident on the layer. To take into account the scattering peculiarities in the neighborhood of the reflection point, we introduce an analytical transformation for the eikonal equation solution derived by the perturbation method. This transformation permits calculations of radio-wave phase fluctuations for any monotonous profile of the regular dielectric permittivity of the plasma in the layer. Using this approach, we have derived analytical formulas for the variance and two-dimensional spatial spectrum of phase fluctuations, depending on the three-dimensional power spectrum of plasma fluctuations. We have also estimated a contribution of reflection point fluctuations to the phase fluctuations and determined the limits of applicability of the derived formulas. The presented analytical transformation of the eikonal equation solution can be used to calculate other statistical moments of the radio wave phase in many problems of solar-terrestrial physics where scattering and reflection of radio waves by plasma formations are important.

Afanasiev, N. T.; Afanasiev, A. N.; Larunin, O. A.; Markov, V. P.

2010-05-01

101

Application of surface acoustic wave devices to radio telemetry  

NASA Technical Reports Server (NTRS)

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

Strasilla, U.

1983-01-01

102

Scattering of radio frequency waves by edge density blobs in tokamaks  

NASA Astrophysics Data System (ADS)

The density blobs and fluctuations present in the edge region of magnetic fusion devices can scatter radio frequency (RF) waves through refraction and diffraction. A previous study has considered refractive scattering using the geometric optics approximation [1]. It is found that the scattering can diffuse rays in configuration space and in wave-vector space. The diffusion in space can make the rays miss their intended target region, while the diffusion in wave-vector space can broaden the wave spectrum and modify the wave damping profile. The geometric optics approximation is of limited validity. We have developed a full-wave, cold plasma, model for wave scattering in which the size and density of the blobs are arbitrary. The model allows for diffractive scattering of waves as well as coupling of the incident wave to other plasma waves. Diffractive scattering can lead to ``shadowing'' while the coupling to other plasma waves can broaden the spectrum of the incident wave, and reduce the power propagating into the interior of the plasma. The full-wave model and the consequences of diffractive scattering of RF waves by blobs will be discussed. [4pt] [1] K. Hizanidis, A.K. Ram, Y. Kominis, and C. Tsironis, Phys. Plasmas 17, 022505 (2010).

Ram, A. K.; Hizanidis, K.; Kominis, Y.

2012-03-01

103

Propagation characteristics of the ionospheric transmission window relating to long wave radio location issues  

NASA Astrophysics Data System (ADS)

Most applications of long radio waves (ELF/VLF/LF/MF) are ground-based and exploit the fact that such signals can propagate to great distances via reflections from the lower ionosphere. It is known however that, owing to the influence of the earth's magnetic field, long wave signals can penetrate through the ionosphere as well; at times, the waves penetrate with relatively little loss, depending on ionospheric conditions and other propagation factors. This has prompted investigations of the long wave 'ionospheric transmission window' as part of efforts to assess the feasibility of deploying long wave emitters in space for terrestrial applications and/or for exploiting, in space, signals emanating from ground-based long wave transmitters. This paper outlines results of theoretical and experimental investigations of the ionospheric transmission window over the frequency range from about 100 Hz to 500 kHz, with emphasis on directional issues associated with long wave penetration of the ionosphere.

Kossey, Paul A.; Lewis, Edward A.

1992-11-01

104

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

SciTech Connect

We present detailed in situ observations from the ISEE 3 spacecraft of energetic electrons, plasma waves, and radio emission for the type III solar radio burst of 1979 February 17. The reduced one-dimensional distribution function f (v) of the electrons is constructed as a function of time. Since the faster electrons arrive before the slower ones, a bump on tail distribution is formed which is unstable on the growth of Langmuir waves. The plasma wave growth computed from f (v) agrees well with the observed onset of the Langmuir waves, and there is qualitative agreement between variations in the plasma wave levels and in the development of regions of positive slope in f (v). The evolution of f (v), however, predicts far higher plasma wave levels than those observed. The maximum levels observed are about equal to the threshold for nonlinear wave processes, such as oscillating two-stream instability and soliton collapse. Also, the lack of obvious plateauing of the distribution suggests that the observed waves have been removed from resonance with the beam electrons. Finally, the plasma waves are observed to be highly impulsive in nature.

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

1981-12-01

105

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

PubMed

We report data from the Cassini radio and plasma wave instrument during the approach and first orbit at Saturn. During the approach, radio emissions from Saturn showed that the radio rotation period is now 10 hours 45 minutes 45 +/- 36 seconds, about 6 minutes longer than measured by Voyager in 1980 to 1981. In addition, many intense impulsive radio signals were detected from Saturn lightning during the approach and first orbit. Some of these have been linked to storm systems observed by the Cassini imaging instrument. Within the magnetosphere, whistler-mode auroral hiss emissions were observed near the rings, suggesting that a strong electrodynamic interaction is occurring in or near the rings. PMID:15604362

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

2005-02-25

106

An Approximate Model of Radio Wave Propagation for Inter-Vehicles Communication Simulation Systems  

Microsoft Academic Search

In development of inter-vehicles com- munication (IVC) systems, simulation technologies are very essential to verify the correctness of proto- cols. We focus on a model of radio wave propaga- tion for IVC simulation systems and approximate the model. As a land mobile communication model, we adopt Kaji model. In our model, a distance be- tween vehicles, a building density, and

Junya Oishi; Koichi Asakura; Toyohide Watanabe

2006-01-01

107

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

108

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

109

Skin Effect in Uniform Half-Space for Unsteady Radio Waves.  

National Technical Information Service (NTIS)

A theoretical study is given of the skin effect for radio waves emitted into a half-space below by a vertical dipole situated in the lower portion of a half-space above. It is assumed that the upper half-space contains a vacuum and that the lower half-spa...

Y. P. Verbin

1972-01-01

110

Some Calculations of Ionospheric Reflection Coefficients for Low Frequency Radio Waves.  

National Technical Information Service (NTIS)

Results are presented of the computation of the reflective properties of a sharply bounded ionosphere for low frequency radio waves. The method of Barber and Crombie has been adopted. It is shown that for this model of ionosphere the phase of the reflecti...

B. Burgess G. C. A. Sunderland

1966-01-01

111

Remote Sensing of Low and Mid-Latitude Ionospheric Disturbances During Solar Minimum Using CITRIS and CERTO Measurements of TEC and Radio Scintillation  

NASA Astrophysics Data System (ADS)

Unique data on ionospheric plasma disturbances from the Naval Research Laboratory CITRIS (Scintillation and TEC Receiver in Space) instrument will be presented. CITRIS is a multi-band receiver that recorded TEC (Total Electron Content) and radio scintillations from Low-Earth Orbit (LEO) on STPSat1. The 555+/5 km altitude 35° inclination orbit covers low and mid-latitudes. The measurements require propagation from a transmitter to a receiver through the F-region plasma. CITRIS used both 1) satellite beacons in LEO, such as the NRL CERTO (Coherent Electromagnetic Radio TOmography) three-frequency beacons transmitting at 150/400/1067 MHz and 2) the French global network of ground-based DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) beacons transmitting at 401.25 and 2036.25 MHz. CITRIS was operated in a complementary fashion with the C/NOFS satellite during most of its first year of operations; C/NOFS carries CERTO beacon along with in-situ diagnostics. CITRIS and ground receivers can simultaneously measure TEC and scintillations on different paths using CERTO on C/NOFS. When C/NOFS is not in view, CITRIS makes measurements from DORIS beacons and other LEO satellites. Because of the orbits CITRIS will always make measurements at the same longitude within 48 min of C/NOFS. The ability to look at multiple paths is unique and useful for studying the spatial extent and time duration of disturbances. The combination of TEC and scintillation measurements provides information on a range of scale-sizes from >1 km to about 100 m. The joint data set on plasma structures at low-latitudes is a focus of our presentation, with the addition of comparisons to CITRIS data taken at mid-latitude. Several types of irregularities have been studied including Spread-F and the newly discovered dawn-side depletions. The data covers large portions of the Earth (including the Pacific, African and South American sectors) during an unusually quite portion of the most recent solar minimum.

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

2010-12-01

112

Standing Wave Pattern of HF Radio Waves in the Ionospheric Reflection Region. Part 2. Applications.  

National Technical Information Service (NTIS)

General analytical formulas derived within a uniform approximation are utilized for determining the wave pattern of a vertically propagating HF wave totally or partially reflected from the ionosphere. The full three-dimensional wave is calculated accurate...

B. Lundborg B. Thide

1985-01-01

113

Magnetospheric propagation of very long radio waves in geomagnetic waveguides  

NASA Astrophysics Data System (ADS)

The conditions of the propagation of VLF waves along geomagnetic waveguides in the earth magnetosphere are investigated theoretically, and the results are compared with satellite data. It is shown that VLF signals emitted from the earth surface are captured by geomagnetic waveguides at heights of approximately 500-2000 km above the earth surface when charged particle concentration in the waveguide exceeds that in the ambient plasma by at least 10 percent. A criterion for the capture of VLF signals by a geomagnetic waveguide is formulated. The results obtained are consistent with satellite measurements of VLF signals from ground transmitters.

Aksenov, V. I.; Moshkov, A. V.

114

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

115

Beam characterization of a new continuous wave radio frequency quadrupole accelerator  

NASA Astrophysics Data System (ADS)

A new Continuous Wave (CW) Radio Frequency Quadrupole (RFQ) for the ATLAS (Argonne Tandem Linac Accelerator System) Intensity Upgrade was developed, built and tested at Argonne National Laboratory. We present here a characterization of the RFQ output beam in the longitudinal phase space, as well as a measurement of the transverse beam halo. Measurement results are compared to simulations performed using the beam dynamics code TRACK.

Perry, A.; Dickerson, C.; Ostroumov, P. N.; Zinkann, G.

2014-01-01

116

Phase shift keying using optical delay modulation for millimeter-wave fiber-optic radio links  

Microsoft Academic Search

We propose a novel phase shift keying technique that uses optical delay modulation for fiber optic radio links. Using only a 2×1 switch and a delay line, this technique enables modulation of a millimeter-wave carrier at bit rates of several gigabits per second or higher, where high-speed devices are not needed. Binary phase shift keying (BPSK) was experimentally demonstrated, 2-Gb\\/s

Yoshiyuki Doi; Seiji Fukushima; Tetsuichiro Ohno; Yutaka Matsuoka; Hiroaki Takeuchi

2000-01-01

117

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

NASA Astrophysics Data System (ADS)

A numerical analysis is made of signal effects on short-wave paths more than 260 km long, due to radio scattering by a traveling spherical disturbance generated by a shock wave caused by an industrial surface explosion. It is shown that the Doppler frequency shift of the scattered signal takes a positive value and decreases montonically with time. Ray trajectories of the transmitter/disturbance/F2-layer/receiver and transmitter/F2-layer/disturbance/receiver types are found to occur.

Spitsyn, V. G.

1987-08-01

118

Radar Characteristics of Precipitation of Different Nature, Spectra, Intensity and Temperatures in the Centimeter and Millimeter Ranges of Radio Waves.  

National Technical Information Service (NTIS)

The specific effective area of retrograde scattering and attenuation factors of radio waves in the centimeter and millimeter range, by rainfall at various temperatures and intensities were calculated. This quantitative data on the attenuating and reflecti...

N. P. Krasyuk V. I. Rozenberg D. A. Chistyakov

1969-01-01

119

On the determination of gravity wave momentum flux from GPS radio occultation data  

NASA Astrophysics Data System (ADS)

Global Positioning System (GPS) radio occultation (RO) is a well-established technique for obtaining global gravity wave (GW) information. RO uses GPS signals received by 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 of global monitoring of the vertical temperature structure and atmospheric wave parameters. The six-satellite 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. Here, a method for the determination of the real horizontal wavelength from three vertical profiles is 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.

2013-11-01

120

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

NASA Technical Reports Server (NTRS)

The four wave interaction process, known as the oscillating two stream instability (OTSI) is considered as one of the mechanisms responsible for stabilizing the electron beams associated with solar type III radio bursts. It has been reported that (1) an intense localized Langmuir wave packet associated with a type III burst contains the spectral characteristics of the OTSI: (a) a resonant peak at the local electron plasma frequency, f(sub pe), (b) a Stokes peak at a frequency slightly lower than f(sub pe), (c) anti-Stokes peak at a frequency slightly higher than f(sub pe), and (d) a low frequency enhancement below a few hundred Hz, (2) the frequencies and wave numbers of these spectral components satisfy the resonance conditions of the OTSI, and (3) the peak intensity of the wave packet is well above the thresholds for the OTSI as well as spatial collapse of envelope solitons. Here, for the first time, applying the trispectral analysis on this wave packet, we show that the tricoherence, which measures the degree of coherent four-wave coupling amongst the observed spectral components exhibits a peak. This provides an additional evidence for the OTSI and related spatial collapse of Langmuir envelope solitons in type III burst sources.

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

2012-01-01

121

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

122

Dynamical evidence for nonlinear Langmuir wave processes in type III solar radio bursts  

NASA Astrophysics Data System (ADS)

The nonlinear processes and evolution of Langmuir waves in the source regions of type III solar radio bursts are explored in detail. Langmuir waves recorded by the Time Domain Sampler of the STEREO/WAVES instrument can be roughly classified into six groups based on the waveform, power spectra, and field strength perpendicular to the local magnetic field. It is argued that these groups correspond to either different stages of the evolution of Langmuir waves generated by electron beams or differ due to the direction of the magnetic field relative to the solar wind velocity. Approximately half of the observed Langmuir waves have strong perpendicular fields, meaning that understanding how these fields are produced is crucial for understanding type III sources. Most events recorded are either localized waveforms consistent with Langmuir eigenmodes or have two or more spectral peaks consistent with electrostatic (ES) decay of Langmuir/z mode waves. The remaining events appear to correspond to either earlier or later stages of Langmuir wave evolution or are decay events for which the Doppler shift is insufficient to distinguish the beam-driven and product Langmuir waves. This is supported by the fact that most events exceed the threshold for ES decay even though their spectra show no evidence for decay and some of the events are observed when the solar wind flow is approximately perpendicular to the magnetic field, minimizing Doppler shifting. Low-frequency fields produced by intense Langmuir waves are quantitatively consistent with density perturbations produced by the ponderomotive force, ion-acoustic waves produced by ES decay, or sheath rectification. Above the observed nonlinear threshold, quantitative analysis suggests that the observed low-frequency signals are consistent with perturbations produced by ponderomotive effects and ion-acoustic waves produced by ES decay, but effects of sheath rectification may also contribute.

Graham, D. B.; Cairns, Iver H.

2014-04-01

123

Comparative equatorial scintillation morphology: American and pacific sectors  

Microsoft Academic Search

This report examines the severity of radio-wave amplitude scintillation measured at two stations near the equator, but far apart in longitude: Kwajalein Atoll in the Marshall Islands, and Ancon, Peru. The data used are observations of the Wideband satellite signal intensity at VHF, UHF, and L-band frequencies. These are presented in terms of the cumulative distribution of S4 index, which

R. C. Livingston

1978-01-01

124

Backscattering of short-wave radio waves from the ocean surface  

Microsoft Academic Search

The Kirchhoff method is used to obtain expressions for the coherent and incoherent components of a radio signal reflected from the ocean surface with a quasi-harmonic correlation function for the case of almost vertical angles of incidence. It is found that the ratio of the power of the incoherent signal to that of the coherent signal at vertical incidence and

A. A. Garnakerian; A. S. Sosunov

1976-01-01

125

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

126

Investigation of methods for improving models of ionospheric plasma-density irregularities and radio-frequency scintillation. Technical report  

SciTech Connect

Many modern military systems used for communications, command and control, navigation, and surveillance depend on reliable and relatively noise-free transmission of radiowave signals through the earth's ionosphere. Small-scale irregularities in the ionospheric density can cause severe distortion, known as radiowave scintillation, of both the amplitude and phase of these signals. The WBMOD computer program can be used to estimate these effects on a wide range of systems. The objective of this study is to investigate improvements to the WBMOD model based on extensive data sets covering both the equatorial and high-latitude regimes. This report summarizes the work completed during the second year, which include completion of the new models for the equatorial region and initial development of models for the high latitude (auroral and polar cap) region.

Secan, J.A.; Bussey, R.M.

1993-11-01

127

On altitude structure of centimeter-wave radio emission of solar active regions  

NASA Astrophysics Data System (ADS)

A method is presented for the direct measurement of the heights of the radio emission of solar active regions when they are located at the limb in order to reconstruct the vertical structure of the magnetic field in solar active regions. The method involves an analysis of radio source positions in the scans based on high frequency resolution one-dimensional centimeter-wave measurements performed on the RATAN-600 radio telescope. Radio sources are difficult to identify at many frequencies when observed at the limb at zero position angle because of abrupt signal variations at the solar limb. To eliminate edge effects on the scan, special observing periods are used (near vernal and autumnal equinoxes), when the source at the limb is located far from the scan edge because of the large position angle of the Sun. As a result of these observations, the spectra of relative heights are constructed for a number of sources for the period from 2007 through 2012. Source heights are shown to generally increase with wavelength. The height difference between the 5 and 2 cm emission is equal to 5.2 ± 2.0 Mm, and the corresponding height difference between the 8 and 2 cm emission is equal to 9.6 ± 3.0 Mm. It is shown that such characteristics can be obtained for a field generated by a dipole submerged under the photosphere at a depth of 17 Mm irrespective of the possible reduction of relative altitudes to absolute altitudes.

Bogod, V. M.; Yasnov, L. V.

2013-07-01

128

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

129

Verification of particle simulation of radio frequency waves in fusion plasmas  

NASA Astrophysics Data System (ADS)

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

Kuley, Animesh; Wang, Z. X.; Lin, Z.; Wessel, F.

2013-10-01

130

Nonlinear reflectivity of high-power radio waves in the ionosphere  

NASA Astrophysics Data System (ADS)

The results of an experiment to determine the effect of wide-band absorption (WBA) on a radio pump wave causing the WBA are reported. The amplitude of the 5.423 MHz pump wave was measured at a receiver 40 km south of the transmitter at high latitudes. The effective radiated power of the wave was stepped upwards 40 times from 0-260 MW and down again in 9 sec intervals. Several cycles were repeated, and the reflected signal was observed to increase steadily, but increasingly more slowly, up to 40-50% of full power, when the effective reflected signal power began to decrease with increasing signal power. The results indicate the presence of a certain optimum power above which the signal received via the ionosphere will be reduced.

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

1982-02-01

131

Verification of particle simulation of radio frequency waves in fusion plasmas  

SciTech Connect

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

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

2013-10-15

132

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

133

Self-compensated standing wave probe for characterization of radio-frequency plasmas.  

PubMed

A simple self-compensated Langmuir probe using the character of a standing wave is developed for characterization of radio-frequency (RF) discharge plasmas. This probe is based on a concept that the interference of RF field is eliminated at the node of a standing wave which exists ideally at one-fourth of the RF wavelength (?/4) away from the probe tip in the plasma. The fluctuation of plasma space potential is suppressed as confirmed by comparison with a non-compensated probe and a self-compensated probe using an inductor-capacitor (LC) resonant circuit. The plasma parameters obtained with the standing wave probe are in agreement with those with the LC resonant probe within discrepancy of 15% indicating high reliability of the results. PMID:24985819

Sung, Ta-Lun; Matsumura, Shosaku; Teii, Kungen; Teii, Shinriki

2014-06-01

134

Full-wave reflection of lightning long-wave radio pulses from the ionospheric D- region  

NASA Astrophysics Data System (ADS)

A model is developed for calculating ionospheric reflection of electromagnetic pulses emitted by lightning, with most energy in the long-wave spectral region (f = 3 - 100 kHz). The building-block of the calculation is a differential-equation full-wave solution of Maxwell's Equations for the complex reflection of individual plane waves incident from below, by the anisotropic, dissipative, diffuse dielectric profile of the lower ionosphere. This full-wave solution is then put into a summation over plane waves in an angular Direct Fourier Transform to obtain the reflection properties of curved wavefronts. This step models also the diffraction effects of long- wave ionospheric reflections observed at short or medium range (200 - 500 km). The calculation can be done with any arbitrary but smooth dielectric profile versus altitude. For an initial test, we use the classic D- region exponential profiles of electron density and collision rate given by Wait. With even these simple profiles, our model of full-wave reflection of curved wavefronts captures some of the basic attributes of observed reflected waveforms recorded with the Los Alamos Sferic Array.

Jacobson, A. R.; Shao, X.; Holzworth, R.

2008-12-01

135

Particle events associated with local type III radio emission and Langmuir waves in the interplanetary medium.  

NASA Astrophysics Data System (ADS)

The first detection of local type III radio emissions at the fundamental and harmonic of the plasma frequency was made by the Ulysses spacecraft when it was in the ecliptic plane and between ~1.4 and ~2.2AU from the Sun. In-situ Langmuir waves were observed simultaneously with each local radio event, indicating the presence of an electron beam at the spacecraft. We analyze the energetic electron (42-290keV) and ion (60-5000keV) fluxes measured by the HI-SCALE instrument on Ulysses and examine the magnetic field and plasma structures present in the interplanetary medium during the times of the three reported local type III events. An impulsive electron event was found to be associated with each of the local radio events. For two events, the electron fluxes were observed simultaneously in all energy channels, indicating that an interplanetary structure, with propagating energetic particles already present, convected past the spacecraft. One of these structures is seen in association with a magnetic cloud. The presence of energetic electrons of solar origin reveals that one end of the structure field lines on which they move was still magnetically connected to the Sun. However, the back streaming electrons present a loss cone with high angles (50-60deg) which indicates that the other side of the magnetic field lines cannot be rooted back at the Sun and are essentially opened into the outer heliosphere. The last observation indicates that the structure is either a substructure of the magnetic cloud or at the edge of the cloud. The local fundamental and 2nd harmonic radiation and in-situ Langmuir waves were observed as Ulysses entered the cloud. For the third local type III event a velocity dispersion in the onset times of the energetic electrons was observed. The measured velocity dispersion was used to determine the ejection time of the electrons at the Sun and to estimate the lowest energy (8+/-3keV) of the electrons at the spacecraft at the onset of the local radio emission. The minimum energy of the electrons associated with the other local radio events was estimated to be ~6+/-1 and 24+/-3keV. These estimated minimum electron energies, associated with the production of in-situ Langmuir waves, are consistent with previous direct measurements by spacecraft at 1AU.

Chaizy, P.; Pick, M.; Reiner, M.; Anderson, K. A.; Phillips, J.; Forsyth, R.

1995-11-01

136

EUV jets, type III radio bursts and sunspot waves investigated using SDO/AIA observations  

NASA Astrophysics Data System (ADS)

Context. Quasi-periodic plasma jets are often ejected from the Sun into interplanetary space. The commonly observed signatures are day-long sequences of type III radio bursts. Aims: The aim is to identify the source of quasi-periodic jets observed on 3 Aug. 2010 in the Sun's corona and in interplanetary space. Methods: Images from the Solar Dynamics Observatory (SDO) at 211 Å are used to identify the solar source of the type III radio bursts seen in WIND/WAVES dynamic spectra. We analyse a 2.5 h period during which six strong bursts are seen. The radio signals are cross-correlated with emission from extreme ultraviolet (EUV) jets coming from the western side of a sunspot in AR 11092. The jets are further cross-correlated with brightening at a small site on the edge of the sunspot umbra, and the brightening with 3-min sunspot intensity oscillations. Results: The radio bursts correlate very well with the EUV jets. The EUV jet emission also correlates well with brightening at what looks like their footpoint at the edge of the umbra. The jet emission lags the radio signals and the footpoint brightening by about 30 s because the EUV jets take time to develop. For 10-15 min after strong EUV jets are ejected, the footpoint brightens at roughly 3 min intervals. In both the EUV images and the extracted light curves, it looks as though the brightening is related to the 3-min sunspot oscillations, although the correlation coefficient is rather low. The only open field near the jets is rooted in the sunspot. Conclusions: Active region EUV/X-ray jets and interplanetary electron streams originate on the edge of the sunspot umbra. They form along a current sheet between the sunspot open field and closed field connecting to underlying satellite flux. Sunspot running penumbral waves cause roughly 3-min jet footpoint brightening. The relationship between the waves and jets is less clear. Movie is available in electronic form at http://www.aanda.org

Innes, D. E.; Cameron, R. H.; Solanki, S. K.

2011-07-01

137

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

NASA Astrophysics Data System (ADS)

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

Golla, Thejappa; MacDowall, Robert

138

Statistical Analysis of Langmuir Waves Associated with Type III Radio Bursts  

NASA Astrophysics Data System (ADS)

Interplanetary electron beams, produced by CMEs and flares, are unstable in the solar wind and generate Langmuir waves at the local plasma frequency (f_p) or its harmonic (2f_p). Radio observations of the waves in the range 4 - 256 kHz from the WAVES experiment onboard the WIND spacecraft have been statistically analyzed. A subset of 36 events has been selected for this study. The background consisting of thermal noise, type III bursts and Galactic background has been removed and the remaining power spectral density has been fitted by Pearsons system of probability distributions. The coefficients of the probability distributions have been calculated by using two methods: method of moments and maximum likelihood estimation method. We have shown that the probability distributions of the power spectral density of the Langmuir waves belong to three different types of Pearsons probability distributions: type I, type IV and type VI. In order to compare the goodness of the fits, a few statistical tests have been applied, showing for all of the considered events that the Pearsons probability distributions fit the data better than the Gaussian ones. This is in contradiction with the Stochastic Growth Theory which predicts log-normal distribution for the power spectral density of the Langmuir waves. The uncertainty analysis that has been performed also goes in favor of the use of Pearsons system of distributions to fit the data.

Vidojevic, S.; Zaslavsky, A.; Maksimovic, M.; Atanackovic, O.; Hoang, S.; Drazic, M.

2012-01-01

139

Ion species mix and ion density measurements using radio frequency waves  

NASA Astrophysics Data System (ADS)

Radio frequency wave applications have demonstrated great versatility in tokamak plasmas. Two applications, using the same diagnostic design, can make use of a fast Alfven wave to make ion species mix and ion density measurements. A discussion and derivation, using the cold plasma approximation, is given for a fast Alfven radio wave used for making an interferometry density measurement, a two ion species mix reflectometry measurement, and a three ion species mix reflectometry measurement. Utilizing the dependence of the fast Alfven wave upon density, the mass density evolution of a plasma can be tracked via interferometry. In addition, new antennas were installed where the graphite tiles were converted to be part of the receiving antenna, increasing reception by at least one order of magnitude. Density evolution measurements with these new antennas (˜100 MHz, 20mW) were made for the first several hundred milliseconds until tracking was lost. When tracking was successful, the density evolution observed from the new antennas shows reasonable agreement with existing diagnostics. A heterodyne reflectometer could provide a direct and inexpensive measurement of ion species mixes with different charge to mass ratios. Using the cold plasma dispersion relation for multiple ion species, the ion-ion hybrid cutoff frequency is uniquely determined by the density ratio and cyclotron frequencies of those two species. The phase of a ˜20 MHz wave that travels from the launching point to the cutoff layer to the receiving antenna provides a direct measure of the hydrogen: deuterium species mix. In the first experiment, a fast Alfven wave was launched perpendicular to a hydrogen-deuterium plasma from the low field side of the DIII-D tokamak. Quantitative measurements observed a hydrogen concentration range of 3%--67% and a maximum penetration depth of 0.60 m. Corroborative values were obtained from two independent diagnostics. In the second experiment, the fast Alfven wave was launched from the high field side during a hydrogen puffing experiment. Results again show agreement with other diagnostics. In addition, it is demonstrated that a wave launched from the high field side is able to tunnel through the resonance layer and be reflected back to the receiving antenna.

Watson, George Wilder, III

140

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

141

Review of equatorial scintillation phenomena in light of recent developments in the theory and measurement of equatorial irregularities  

Microsoft Academic Search

Recent developments in the understanding of equatorial irregularities have come from a unique combination of rocket, satellite, radar, theoretical, and computer simulation investigations. These will be reviewed with emphasis on the effect of the irregularities upon the propagation of radio waves. Recent scintillation calculations based upon in situ rocket and satellite irregularity measurements are also reviewed and a new composite

S. Basu; M. C. Kelley

1977-01-01

142

Wave activity at ionospheric heights above the Andes Mountains detected from FORMOSAT-3/COSMIC GPS radio occultation data  

NASA Astrophysics Data System (ADS)

estimation of the ionospheric wave activity, derived from 4 years of FORMOSAT-3/ COSMIC GPS (Taiwan's Formosa Satellite Mission 3/Constellation Observing System for Meteorology—Global Positioning System) radio occultation electron density data, is presented. A systematic enhancement at the eastern side of the Andes range with respect to the western side is observed. A fitting method to remove the wavelike component from each measured profile and estimate the wave activity is described. The differential effect introduced by the action of orography on the generation, to the eastern side of the Andes, of mountain waves, deep convection waves, or even secondary waves aloft after momentum deposition in the middle atmosphere, is suggested.

Torre, A.; Alexander, P.; Llamedo, P.; Hierro, R.; Nava, B.; Radicella, S.; Schmidt, T.; Wickert, J.

2014-03-01

143

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

144

Development of data communication system with ultra high frequency radio wave for implantable artificial hearts.  

PubMed

In order to minimize infection risks of patients with artificial hearts, wireless data transmission methods with electromagnetic induction or light have been developed. However, these methods tend to become difficult to transmit data if the external data transmission unit moves from its proper position. To resolve this serious problem, the purpose of this study is to develop a prototype wireless data communication system with ultra high frequency radio wave and confirm its performance. Due to its high-speed communication rate, low power consumption, high tolerance to electromagnetic disturbances, and secure wireless communication, we adopted Bluetooth radio wave technology for our system. The system consists of an internal data transmission unit and an external data transmission unit (53 by 64 by 16 mm, each), and each has a Bluetooth module (radio field intensity: 4 dBm, receiver sensitivity: -80 dBm). The internal unit also has a micro controller with an 8-channel 10-bit A/D converter, and the external unit also has a RS-232C converter. We experimented with the internal unit implanted into pig meat, and carried out data transmission tests to evaluate the performance of this system in tissue thickness of up to 3 mm. As a result, data transfer speeds of about 20 kbps were achieved within the communication distance of 10 m. In conclusion, we confirmed that the system can wirelessly transmit the data from the inside of the body to the outside, and it promises to resolve unstable data transmission due to accidental movements of an external data transmission unit. PMID:19964616

Tsujimura, Shinichi; Yamagishi, Hiroto; Sankai, Yoshiyuki

2009-01-01

145

Measurement of Attenuation Length for Radio Wave in Natural Rock Salt Samples Concerning Ultra High Energy Neutrino Detection  

NASA Astrophysics Data System (ADS)

Ultra high energy (UHE) neutrinos with the energy larger than 1015 eV, surely arrive at the earth with Greisen, Zatsepin, Kuz'min (GZK) effect, though the rate is very few. The rare call requires us to utilize a large mass (>10 Gton) of detection medium. UHE neutrino generates a huge number of unpaired electrons in rock salt. They would emit sensible radio wave by coherent Cherenkov (Askar'yan) effect. The longer attenuation length of radio wave in rock salt reduces the number of antennas required. Several rock salt samples including synthesized one are measured in attenuation length for radio wave transmission at 0.3 and 1.0 GHz. Some show attenuation length larger than 300 m, which indicate a possibility for constructing a salt neutrino detector.

Chiba, Masami; Watanabe, Yusuke; Yasuda, Osamu; Kamijo, Toshio; Chikashige, Yuichi; Kon, Tadashi; Amano, Akio; Takeoka, Yosito; Shimizu, Yutaka; Mori, Satoshi; Ninomiya, Sosuke

146

Measurement of Attenuation Length in Rock Salt and Limestone in Radio Wave for Ultra-High Energy Neutrino Detector  

NASA Astrophysics Data System (ADS)

Rock salt and limestone are studied to determine their suitability for use as a radio wave transmission medium in an ultra high energy (UHE) cosmic neutrino detector. The detector would detect radio wave generated by the Askar'yan effect (coherent Cherenkov from negative excess charges in an electromagnetic shower) in the interaction of the UHE neutrinos with the high-density medium. We have measured the radio wave attenuation lengths of the rock salt samples from the Asse mine in Germany at 9.4 GHz and found it to be longer than 3.3 m and then whereas under the assumption of constant tan? with respect to frequency, we estimate it by extrapolation to be longer than 330 m at 94 MHz.

Chiba, Masami; Kawaki, Miho; Inuzuka, Masahide; Kamijo, Toshio; Athar, H.

2002-09-01

147

Ionospheric scintillation  

Microsoft Academic Search

Available observations of ionospheric scintillation are analyzed to evaluate the adequacy of existing models used for the interpretation of scintillation data. The theoretical models are reviewed and the frequency and propagation geometry dependences predicted by the models are compared with the observations. The models were used to construct scintillation occurrence distribution functions which show that scintillation phenomena significantly affect the

R. K. Crane

1977-01-01

148

Statistical Survey of Type III Radio Bursts at Long Wavelengths Observed by the Solar TErrestrial RElations Observatory (STEREO)/ Waves Instruments: Radio Flux Density Variations with Frequency  

NASA Astrophysics Data System (ADS)

We have performed a statistical study of 152 Type III radio bursts observed by Solar TErrestrial RElations Observatory (STEREO)/ Waves between May 2007 and February 2013. We investigated the flux density between 125 kHz and 16 MHz. Both high- and low-frequency cutoffs were observed in 60 % of events, suggesting an important role of propagation. As already reported by previous authors, we observed that the highest flux density occurs at 1 MHz on both spacecraft. We developed a simplified analytical model of the flux density as a function of radial distance and compared it with the STEREO/ Waves data.

Krupar, V.; Maksimovic, M.; Santolik, O.; Kontar, E. P.; Cecconi, B.; Hoang, S.; Kruparova, O.; Soucek, J.; Reid, H.; Zaslavsky, A.

2014-08-01

149

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

150

The radio waves & thermal electrostatic noise spectroscopy (SORBET) experiment on BepiColombo/MMO/PWI and the importance of radio HF measurements at Mercury  

NASA Astrophysics Data System (ADS)

SORBET (Spectroscopie des Ondes Radio & du Bruit Electrostatique Thermique) is a radio HF spectrometer designed for the radio and Plasma Waves Instrument (PWI) onboard BepiColombo/Mercury Magnetospheric Orbiter (MMO), which performs remote and in-situ measurements of waves (electromagnetic and electrostatic). Technically, SORBET includes a plasma wave spectrometer, with two E-field inputs from the two perpendicular electric antennas and one B-field input from a search coil, in the range 2.5 kHz - 640 kHz. This frequency band includes the local gyrofrequency and plasma frequency expected on most part of the MMO orbits. SORBET also includes a higher frequency radio receiver for remote sensing in the range 500kHz-10.2MHz. Owing to its capabilities, SORBET will be able to address the following scientific objectives: High resolution mapping (˜ 30 km) of electron density and temperature in the solar wind and Hermean magnetosphere and exo-ionosphere, via the technique of Quasi-Thermal Noise (QTN) spectroscopy. It is noteworthy that the QTN technique is weakly sensitive to spacecraft potential and photoelectron perturbations, a point highly in favour of this technique at Mercury. These QTN measurements will be determinant for the dynamic modeling of the magnetosphere and will provide a fundamental input for the chemistry of cold ionized species (Na, K, O ...) in Mercury's environment. Detection and study of Hermean radio emissions, including possible cyclotron emissions (up to ˜ 10-20 kHz) from mildly energetic electrons in highly magnetized (polar?) regions, and possible synchrotron radiation (up to a few MHz?) from more energetic electrons. Monitoring of solar radio emissions up to ~10 MHz, in order to create a solar activity index from the view point of Mercury, allowing to correlate it with the Hermean magnetospheric response. We propose to further discuss these scientific objectives and to underline that such radio HF measurements are a clue for understanding the structure and dynamics (regions, boundaries, acceleration, dissipation processes ...) of the Hermean magnetosphere/exo-ionosphere system and its interaction with the solar wind.

Moncuquet, M.; Matsumoto, H.; Bougeret, J.-L.; Issautier, K.; Kojima, H.; Maksimovic, M.; Meyer-Vernet, N.; Zarka, P.

151

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

NASA Astrophysics Data System (ADS)

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 frequency (UHF) ion line enhancements. Likewise, the stimulated electromagnetic emission (SEE) spectra changed as the pump frequency approached the fourth electron gyroharmonic due to pump-induced variations in electron concentration. Optical recordings were made from Skibotn at 630.0 and 557.7 nm and from Ramfjord in white light. The altitude of the initial optical ring and steady state blob has been estimated by triangulation. The evolution in altitude of the optical emissions, ion line enhancements, and SEE spectra all show a similar morphology but are generally not at exactly the same height. Typically, the optical height is close to and a few kilometers below that of the radar backscatter but sometimes above it, both of which are above the SEE generation altitude. There is evidence that upper hybrid (UH) waves, which propagate perpendicular to the magnetic field line, and Langmuir (L) waves, which propagate parallel to the magnetic field line, act simultaneously to accelerate electrons even in the steady state.

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

2007-05-01

152

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

153

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 ...

154

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

155

GNSS Phase Scintillation and Cycle Slips Occurrence at High Latitudes: Climatology and Forecasting  

NASA Astrophysics Data System (ADS)

Space weather impacts the operation of modern technology that relies on Global Navigation Satellite Systems (GNSS). Ionospheric scintillation (rapid fluctuation of radio wave amplitude and phase) degrades GPS positional accuracy and causes cycle slips leading to loss of lock that affects performance of radio communication and navigation systems. At high latitudes, GPS scintillation and total electron content has been monitored by the Canadian High Arctic Ionospheric Network (CHAIN). GPS phase scintillation and cycle slips, as a function of magnetic latitude and local time, occur on the dayside in the ionospheric cusp, in the nightside auroral oval, and in the polar cap. Interplanetary coronal mass ejections and corotating interaction regions on the leading edge of high-speed streams are closely correlated with the occurrence of scintillation at high latitudes. Results of a superposed epoch analysis of time series of phase scintillation and cycle slips occurrence keyed by arrival times of high speed solar wind streams and interplanetary coronal mass ejections are presented. Based on these results, a method of probabilistic forecasting of high-latitude phase scintillation occurrence is proposed.

Prikryl, Paul; Jayachandran, Periyadan T.; Chadwick, Richard; Kelly, Todd D.

2014-05-01

156

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

NASA Astrophysics Data System (ADS)

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

Chattopadhyay, Taraprasad

2012-07-01

157

Observations of Langmuir Waves Associated with Type III Radio Bursts : Wind Observations and Further Improvements with Inner Heliospheric Missions  

NASA Astrophysics Data System (ADS)

Interplanetary electron beams, produced by solar flares or CMEs, are unstable in the solar wind and generate Langmuir waves at the local plasma frequency Fp. These waves are then converted into the so-called Type III radio bursts which are freely propagating electromagnetic emissions at Fp or its harmonic. We present a statistical analysis of both in-situ Langmuir Waves, associated energetic electrons and Type III bursts recorded simultaneously by the WIND spacecraft. We discuss the relevance of these observations with respect to the latest developments of Type III generation theories. Finally we describe the possible improvements that the forthcoming inner heliospheric mission can bring to this topic.

Maksimovic, M.; Vidojevic, S.; Arnaud, Z.; Krucker, S.

2011-12-01

158

Jovian plasma sheet density profile from low-frequency radio waves  

SciTech Connect

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. To determine the density profile of the plasma sheet, the authors have derived the hinge point position of the plasma disc from MAG data and used the low-frequency cutoffs observed at three frequencies (562 Hz, 1 kHz, and 1.78 kHz) from the PWS experiment. They show that the hinge point position varies with the solar wind ram pressure, and the plasma disc thickness decreases with distance up to about 60 R{sub J}. The average thickness for an isodensity contour corresponding to 1 kHz is 3.29 R{sub J} for V1 and 3.16 R{sub J} for V2.

Rucker, H.O. (Space Research Institute, Graz (Austria)); Ladreiter, H.P. (Univ. of Graz (Austria)); LeBlanc, Y. (Observatoire de Paris, Meudon (France)); Jones, D. (Natural Environment Research Council, Cambridge (England)); Kurth, W.S. (Univ. of Iowa, Iowa City (USA))

1989-04-01

159

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.

160

Radio frequency CD by LH waves in the reversed field experiment  

SciTech Connect

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 ({approx_equal}1.3 GHz) and the best n{sub parallel} values ({approx_equal}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. [Consorzio RFX, Corso Stati Uniti 4, 35127 Padova (Italy); Istituto Nazionale di Fisica della Materia, Padova (Italy); Brambilla, M. [Maz Planck Institute fuer Plasmaphysik, EURATOM Ass., D-85748 Garching (Germany)

1999-09-20

161

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

162

Measurement-based investigations of radio wave propagation: An expose on building corner diffraction  

NASA Astrophysics Data System (ADS)

Predicting performance metrics for the next-generation of multi-mode and multi-antenna wireless communication systems demands site-specific knowledge of the wireless channels underlying radio wave propagation mechanisms. This thesis describes the first measurement system capable of characterizing individual propagation mechanisms in situ. The measurement system merges a high-resolution spatio-temporal wireless channel sounder with a new field reconstruction technique to provide complete knowledge of the wireless channels impulse response throughout a 2-dimensional region. This wealth of data may be combined with space-time filtering techniques to isolate and characterize individual propagation mechanisms. The utility of the spatio-temporal measurement system is demonstrated through a measurement-based investigation of diffraction around building corners. These measurements are combined with space-time filtering techniques and a new linear wedge diffraction model to extract the first semi-empirical diffraction coefficient. Specific contributions of this thesis are: (1) The first ultra-wideband single-input multiple-output (SIMO) channel sounder based upon the sliding correlator architecture. (2) A quasi 2-dimensional field reconstruction technique based upon a conjoint cylindrical wave expansion of coherent perimeter measurements. (3) A wireless channel "filming" technique that records the time-domain evolution of the wireless channel throughout a 2-dimensional region. (4) High-resolution measurements of the space-time wireless channel near a right-angled brick building corner. (5) The application of space-time filtering techniques to isolate the edge diffraction problem from the overall wireless channel. (6) An approximate uniform geometrical theory of diffraction (UTD)-style linear model describing diffraction by an impedance wedge. (7) The first-ever semi-empirical diffraction coefficient extracted from in situ measurement data. This thesis paves the way for several new avenues of research. The comprehensive measurement data provided by channel "filming" will enable researchers to develop and implement powerful space-time filtering techniques that facilitate measurement-based investigations of radio wave propagation. The measurement procedure described in this thesis may be adapted to extract realistic reflection and rough-surface scattering coefficients. Finally, exhaustive measurements of individual propagation mechanisms will enable the first semi-empirical propagation model that integrates empirical descriptions of propagation mechanisms into a UTD-style mechanistic framework.

Pirkl, Ryan J.

163

The radio waves and thermal electrostatic noise spectroscopy (SORBET) experiment on BEPICOLOMBO/MMO/PWI: Scientific objectives and performance  

NASA Astrophysics Data System (ADS)

SORBET ( Spectroscopie des Ondes Radio and du Bruit Electrostatique Thermique) is a radio HF spectrometer designed for the radio and Plasma Waves Instrument onboard BepiColombo/Mercury Magnetospheric Orbiter (MMO), which performs remote and in situ measurements of waves (electromagnetic and electrostatic). Technically, SORBET includes a plasma wave spectrometer, with two E-field inputs from the two perpendicular electric antennas and one B-field input from a search coil, in the range 2.5-640 kHz. This frequency band includes the local gyrofrequency and plasma frequency expected on most part of the MMO orbits. SORBET also includes a higher frequency radio receiver for remote sensing in the range 500 kHz-10.2 MHz. Owing to its capabilities, SORBET will be able to address the following scientific objectives: High resolution mapping (˜30 km) of electron density and temperature in the solar wind and in the Hermean magnetosphere and exo-ionosphere, via the technique of Quasi-Thermal Noise (QTN) spectroscopy. These QTN measurements will be determinant for the dynamic modeling of the magnetosphere and will provide a fundamental input for the chemistry of cold ionized species (Na, K, O, …) in Mercury's environment. Detection and study of Hermean radio emissions, including possible cyclotron emissions (up to ˜10-20 kHz) from mildly energetic electrons in most highly magnetized (polar?) regions, and possible synchrotron radiation (up to a few MHz?) from more energetic electrons. Monitoring of solar radio emissions up to ˜10 MHz in order to create a solar activity index from the view point of Mercury, allowing to correlate it with the Hermean magnetospheric response. We especially discuss the capabilities of SORBET for performing the QTN spectroscopy in Mercury's magnetosphere, using the two electric dipole antennas equipping MMO, called MEFISTO and WPT.

Moncuquet, M.; Matsumoto, H.; Bougeret, J.-L.; Blomberg, L. G.; Issautier, K.; Kasaba, Y.; Kojima, H.; Maksimovic, M.; Meyer-Vernet, N.; Zarka, P.

2006-01-01

164

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

PubMed

We present an observation of beat oscillation generation by coupled modes associated with parametric decay instability (PDI) during radio frequency (rf) wave heating experiments on the Tokyo Spherical Tokamak-2. Nearly identical PDI spectra, which are characterized by the coexistence of the rf pump wave, the lower-sideband wave, and the low-frequency oscillation in the ion-cyclotron range of frequency, are observed at various locations in the edge plasma. A bispectral power analysis was used to experimentally discriminate beat oscillation from the resonant mode for the first time. The pump and lower-sideband waves have resonant mode components, while the low-frequency oscillation is exclusively excited by nonlinear coupling of the pump and lower-sideband waves. Newly discovered nonlocal transport channels in spectral space and in real space via PDI are described. PMID:20867308

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

2010-06-18

165

Development and beam test of a continuous wave radio frequency quadrupole accelerator  

NASA Astrophysics Data System (ADS)

The front end of any modern ion accelerator includes a radio frequency quadrupole (RFQ). While many pulsed ion linacs successfully operate RFQs, several ion accelerators worldwide have significant difficulties operating continuous wave (CW) RFQs to design specifications. In this paper we describe the development and results of the beam commissioning of a CW RFQ designed and built for the National User Facility: Argonne Tandem Linac Accelerator System (ATLAS). Several innovative ideas were implemented in this CW RFQ. By selecting a multisegment split-coaxial structure, we reached moderate transverse dimensions for a 60.625-MHz resonator and provided a highly stabilized electromagnetic field distribution. The accelerating section of the RFQ occupies approximately 50% of the total length and is based on a trapezoidal vane tip modulation that increased the resonator shunt impedance by 60% in this section as compared to conventional sinusoidal modulation. To form an axially symmetric beam exiting the RFQ, a very short output radial matcher with a length of 0.75?? was developed. The RFQ is designed as a 100% oxygen-free electronic (OFE) copper structure and fabricated with a two-step furnace brazing process. The radio frequency (rf) measurements show excellent rf properties for the resonator, with a measured intrinsic Q equal to 94% of the simulated value for OFE copper. An O5+ ion beam extracted from an electron cyclotron resonance ion source was used for the RFQ commissioning. In off-line beam testing, we found excellent coincidence of the measured beam parameters with the results of beam dynamics simulations performed using the beam dynamics code TRACK, which was developed at Argonne. These results demonstrate the great success of the RFQ design and fabrication technology developed here, which can be applied to future CW RFQs.

Ostroumov, P. N.; Mustapha, B.; Barcikowski, A.; Dickerson, C.; Kolomiets, A. A.; Kondrashev, S. A.; Luo, Y.; Paskvan, D.; Perry, A.; Schrage, D.; Sharamentov, S. I.; Sommer, R.; Toter, W.; Zinkann, G.

2012-11-01

166

Some results of night-time scintillations at low latitude  

NASA Astrophysics Data System (ADS)

Ionospheric scintillation observations of VHF radio signals from FLEETSAT satellite (73 deg E longitude) at Bhopal from January 1990 to December 1990 are used to study the characteristic variations of scintillation activity. It is found that scintillation occurrence is essentially a nighttime phenomenon and daytime scintillations are very rare. Annual average nocturnal variation of percentage occurrence of scintillations shows maximum at around 2100-2200 h LT. Seasonally, scintillations are most prominent during equinoxes and least during summer. Geomagnetic disturbances tend to decrease the occurrence of scintillations in the pre-midnight period.

Kumar, Sushil; Vijay, S. K.; Gwal, A. K.

1993-06-01

167

Ceramic Scintillators  

NASA Astrophysics Data System (ADS)

Scintillators are the primary radiation sensor in many applications such as medical diagnostics, medical radiographs, and industrial component inspection. Some of the limitations in the properties of single-crystal scintillators are discussed for imaging applications, and the advantages of a new class of polycrystalline ceramic scintillators are described in detail. After the important scintillator properties of transparency, X-ray stopping power, light output, primary speed, luminescent afterglow, and radiation damage are described, the processing and performance of ceramic scintillators (Y,Gd)2O3:Eu,Pr; Gd2O2S:Pr,Ce,F; and Gd3Ga5O12:Cr,Ce are discussed. Ceramic scintillator uses and trends are presented in light of issues related to their uses in advanced medical and industrial X-ray detectors for CT imaging applications. Finally, some of the challenges are given for successfully developing a polycrystalline ceramic scintillator for use in photon-counting applications.

Greskovich, C.; Duclos, S.

1997-08-01

168

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

NASA Astrophysics Data System (ADS)

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

Jin, Yaqi; Moen, Jøran; Miloch, Wojciech

2014-05-01

169

Study of Sun-Earth interactions using equatorial VHF scintillation in the Indian region  

NASA Astrophysics Data System (ADS)

Plasma density irregularities in the ionosphere (associated with ESF, plasma bubbles and Spo-radic E layers) cause scintillations in various frequency ranges. VHF radio wave scintillation technique is extensively used to study plasma density irregularities of sub-kilometre size . Ef-fects of magnetic and solar activity on ionospheric irregularities are studied so as to ascertain their role in the space weather of the near earth environment in space. Indian Institute of Ge-omagnetism operated a ground network of 13 stations monitoring amplitude scintillations on 244/251 MHz (FLEETSAT 73° E) signals in placecountry-regionIndia for more than a decade under AICPITS. At present VHF scintillation is being recorded at Mumbai by monitoring 251 MHz signal transmitted by geostationary satellite UFO2(71.2 E). sampling at 20 Hz. During CAWSES campaign (March-April 2006, low sunspot period) occurrence of daytime scintilla-tions was observed higher than the nighttime scintillations. This could be due to the fact that during low sunspot years occurrence of spread-F is limited to a narrow latitude region near the dip equator. To study solar cycle association of scintillations, long series of simultaneous amplitude scintillation data for period Jan 1989 to Dec 2000 at Indian low-latitude stations Tirunelveli/Trivandrum, close to dip equator, Pondicherry/Karur, located at the fringe of elec-trojet, Mumbai (dip lat. 13.5o N), a temperate station and Ujjain (dip lat. 18.6o N), close to anomaly crest region are utilized. Nighttime scintillation occurrence is solar activity dependent. Equatorial scintillations are inhibited with increase in geomagnetic activity.

Banola, Sridhar

170

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

171

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

172

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

173

Comparison of Antarctic riometer radio wave absorption and THEMIS mission energetic electron fluxes  

NASA Astrophysics Data System (ADS)

Simultaneous observations of in situ plasma properties in the tail of the Earth's magnetosphere and of ground based instruments, lying on the same geomagnetic field lines, have recently proved to yield significant new results. In most cases magnetosphere ionosphere interactions during the night-time northern hemisphere conditions are studied. Here, observations of energetic electrons in the tail of the Earth's magnetosphere made by the THEMIS mission satellites are compared with auroral radio wave absorption determined by riometers in the Antarctic for sunlit conditions. Days for which satellites and riometers are connected by the same geomagnetic field line are selected using a geomagnetic field model. The six days analysed show clear associations between fluxes and absorptions in some cases. However, these do not necessarily correspond to conjugacy intervals. Hours of positive associations are 1.65 times those for negative associations, all hours and days considered (1.42-3.6 on five days and 0.58 on the other day). These computations are assumed appropriate since the footprints of the satellites used approximately follow corrected geomagnetic parallels for all six days studied. The use of a finer parameterization of geomagnetic models to determine conjugacy may be needed.

Ovalle, Elías M.; Vidal, Sergio E.; Foppiano, Alberto J.; Weatherwax, Allan T.; Stepanova, Marina V.

2012-06-01

174

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

175

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

176

Optimization of Four Wave Mixing Effect in Radio-over-Fiber for a 32Channel 40-GBPS DWDM System  

Microsoft Academic Search

In this paper, we have discussed in detail the four wave mixing (FWM) effect of dense wavelength division multiplexing (DWDM) in Radio-over-Fiber (RoF) system. A 32-channel 40-Gbps system is considered. FWM effect for various channel spacing, input power level, effective fiber area and modulation formats are analyzed. Different schemes for minimizing these effects are discussed for the first time. Considering

Bijayananda Patnaik; P. K. Sahu

2010-01-01

177

Optical Front-Ends to Generate Optical Millimeter-Wave Signal in Radio-Over-Fiber Systems With Different Architectures  

Microsoft Academic Search

We have proposed and experimentally demonstrated three different optical front-ends to implement in wavelength-division-multiplexing (WDM) radio-over-fiber (ROF) networks to minimize the cost of the ROF system. When the number of WDM channels is small, such as smaller than four channels, the simplest front-end to generate WDM optical millimeter (mm)-wave signals is to use only broadband direct-modulation laser (DML) for each

Lin Chen; Shuangchun C. Wen; Ying Li; Jing He; Hong Wen; Yufeng Shao; Ze Dong; Yazhi Pi

2007-01-01

178

Proton injector operational results on a high-power continuous-wave radio-frequency quadrupole accelerator  

Microsoft Academic Search

A 50 keV proton injector utilizing a dc microwave source has been used to operate a 1.25 MeV continuous wave (cw) radio-frequency quadrupole (RFQ) accelerator. RFQ injection places stringent requirements on beam properties including centroid control, emittance, and phase-space matching. The ion source chosen for these applications is based on a microwave discharge operating at 2.45 GHz with an on-axis

Joseph D. Sherman; Gerald O. Bolme; Lash D. Hansborough; Thomas W. Hardek; Debora M. Kerstiens; Earl A. Meyer; J. David Schneider; H. Vernon Smith; Matthew W. Stettler; Ralph R. Stevens; Michael E. Thuot; Thomas J. Zaugg; Adrian A. Arvin; Alvin S. Bolt; Patrick H. Hegler; Mitchell C. Richards; Jack E. Boers; James H. Kamperschroer; Terry L. Figueroa

2000-01-01

179

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

180

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

181

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.

1992-07-28

182

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

183

Stormtime Ionospheric Irregularities in SAPS-Related Troughs: Causes of GPS Scintillations at Mid Latitudes  

NASA Astrophysics Data System (ADS)

Radio-wave scintillations are space weather effects caused by ionospheric plasma density irregularities. The subauroral ionosphere, at magnetic latitudes corresponding to the northeastern US, is generally free of such irregularities and consequently scintillations. Recently, Basu et al. [JGR, 106, 30389, 2001] and Ledvina et al. [GRL, 29, 10.1029/2002GL014770] reported observations of strong GPS phase and amplitude scintillations at 1.5 GHz at Hanscom AFB, MA and Ithaca, NY during the magnetic storms of 23 September, 1999 and 25 - 26 September, 2001, respectively. We report results of a survey of small-scale plasma density and electromagnetic oscillations detected by DMSP F13, 14, and 15 satellites while flying over the affected regions at altitude of 840 km. Langmuir probe data, sampled at a rate of 24 Hz, show that during the scintillation intervals the amplitudes of density oscillations in the frequency range of 3-10 Hz increased by a factor of 100. The enhanced fluctuations appeared at the poleward edges of large-scale density troughs, embedded within subauroral polarization streams. When Doppler-shifted from spacecraft frames of reference the oscillations correspond to irregularities with spatial scales of 2-0.7 km. Most likely these irregularities are responsible for radio-signal scintillations at frequencies near 1 GHz.

Mishin, E. V.; Burke, W. J.; Basu, S.; Kintner, P. M.; Ledvina, B.

2003-12-01

184

Day-fo-day Monitoring of the Comparisons Between UHF Scintillation Forecasts and GNSS Observations  

NASA Astrophysics Data System (ADS)

When trans-ionospheric radio waves propagate through an irregular ionosphere with plasma depletions or 'bubbles', they are subject to sporadic enhancement and fading which is referred to as scintillation. Communication and navigation systems may be subject to these detrimental effects if the scintillation is strong enough. It is critical to have knowledge of the current ionospheric conditions so that system operators can distinguish between the natural radio environment and system-induced failures. In this paper, we present and describe a proven technique for forecasting UHF scintillation activity in the equatorial region after sunset and compare these forecasts with observed global navigation satellite systems (GNSS) L-band scintillation activity at Jicamarca, Peru, on a night-to-night basis. The UHF scintillation forecasting technique is described in a paper by Redmon et al. (Space Weather, Vol 8, 2010) entitled 'A Forecasting Ionospheric Real-time Scintillation Tool (FIRST).' The technique utilizes the observed characteristic parameter h'F from a ground-based, ionospheric sounder near the magnetic equator. This paper demonstrated that there exists an excellent correlation (R2 ~ 0.91) between h'F (1930LT) and the pre-reversal enhancement in vertical ExB drift velocity after sunset which is the prime driver for creating plasma depletions and bubbles. In addition, there exists a 'threshold' in the h'F value at 1930 LT, h'Fthr, such that, on any given evening if h'F is significantly above h'Fthr then scintillation activity is likely to occur and if it is below h'Fthr, scintillation activity is unlikely to occur. The digital sounder at Jicamarca, Peru provides the h'F values between 1830 and 2000 LT. A multi-constellation GNSS receiver at Jicamarca provides 50Hz navigation signal observables continuously since December 2012. S4 index and detrended carrier phase standard deviation, two commonly used amplitude and phase scintillation indices are computed from these observables during the equinox months in 2013. An unprecedented number of open signals from GPS, GLONASS, Galileo, Beidou, and SBAS satellites are included in the observations, providing high spatial and temporal resolution of scintillation indices measurements. In addition to the statistical analysis between the UHF scintillation forecast and observed GNSS receiver S4 index values, detailed quantitative relationships between the vertical ExB drift velocity, prompt penetration magnetic storm disturbances, and the intensity, duration, and spatial distributions of amplitude and phase scintillation will be presented.

Anderson, D. N.; Morton, Y.; Jiao, Y.; Redmon, R. J.

2013-12-01

185

Radio wave method for study of physical phenomena and chemical conversions in heterogeneous explosives under shock wave action  

Microsoft Academic Search

A method is described for determination of shock wave parameters (wave and mass velocity) in heterogeneous explosives. The example of exciting explosion in an octogene composition by weak shock waves is used to demonstrate the possibility of reliable measurement of the velocity of the initiating shock wave, the depth at which detonation develops, and the extent of the predetonation zone,

S. V. Batalov; V. P. Filin; V. V. Shaposhnikov

1991-01-01

186

High performance tunable slow wave elements enabled with nano-patterned permalloy thin film for compact radio frequency applications  

NASA Astrophysics Data System (ADS)

Slow wave elements are promising structures to design compact RF (radio frequency) and mmwave components. This paper reports a comparative study on different types of coplanar wave-guide (CPW) slow wave structures (SWS). New techniques including the use of defected ground structure and the different signal conductor shape have been implemented to achieve higher slow wave effect with comparative loss. Results show that over 42% and 35% reduction in length is reported in the expense of only 0.3 dB and 0.1 dB insertion loss, respectively, which can end up with 66% and 58% area reduction for the design of a branch line coupler. Implementation of the sub micrometer patterned Permalloy (Py) thin film on top of the simple SWS has been demonstrated for the first time to increase the slow wave effect. Comparing with the traditional slow wave structure, with 100 nm thick Py patterns, the inductance per unit length of the SWS has been increased from 879 nH/m to 963 nH/m. The slow wave effect of the designed structure is also tunable by applied DC current. Measured results have shown that the phase shift can be changed from 94° to 90.5° by applying 150 mA DC current. This provides a solution in designing RF passive components which can work in multiple frequency bands.

Farid Rahman, B. M.; Divan, Ralu; Zhang, Hanqiao; Rosenmann, Daniel; Peng, Yujia; Wang, Xuehe; Wang, Guoan

2014-05-01

187

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.

188

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

189

Solar Electron Beams Detected in Hard X-Rays and Radio Waves  

Microsoft Academic Search

We present a statistical survey of electron beam signatures that are detected simultaneously at hard X-ray (HXR) and radio wavelengths during solar flares. For the identification of a simultaneous event we require a type III (normal-drifting or reverse-slope-drifting) radio burst that coincides (within ± 1 s) with a significant (>= 3 sigma HXR pulse of similar duration (>= 1 s).

Markus J. Aschwanden; Arnold O. Benz; Brian R. Dennis; Richard A. Schwartz

1995-01-01

190

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

Microsoft Academic Search

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

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

2010-01-01

191

Study of the Earth's Ionosphere by Reception of Radio Waves from Satellites.  

National Technical Information Service (NTIS)

A study of ionospheric scintillations by the reception of signals from the Russian satellite 1962 Cosmos I was undertaken. The satellite transmitted at a frequency of 20 Mc/s and it was found possible to receive the first two harmonics at 40 Mc/s and 60 M...

S. Basu

1964-01-01

192

A Search for Compact Galactic Radio Sources - Part One - the Two-Frequency Method and Scintillating Sources in the Neighborhood of Supernova Remnants  

Microsoft Academic Search

A new two-frequency correlation technique for reception of scintillating radiation is outlined. Its sensitivity is significantly improved over the conventional single-frequency method because of the lessened influence of narrow-band interference, the exclusion of uncorrelated interference of external and instrumental origin, the diminished effect of receiver gain instabilities, and the elimination of uncorrelated noise originating in the strong nonscintillating component of

A. V. Pynzar; V. A. Udaltsov

1981-01-01

193

Comparative equatorial scintillation morphology--American and Pacific sectors. Topical report no. 3, 1 June 1977-30 June 1978  

Microsoft Academic Search

This report examines the severity of radio-wave amplitude scintillation measured at two stations near the equator, but far apart in longitude: Kwajalein Atoll in the Marshall Islands, and Ancon, Peru. The data used are observations of the Wideband satellite signal intensity at VHF, UHF, and L-band frequencies. These are presented in terms of the cumulative distribution of S4 index, which

1978-01-01

194

Global morphology of ionospheric scintillations  

Microsoft Academic Search

A radio wave traversing the upper and lower atmosphere of the earth suffers a distortion of phase and amplitude. When it traverses drifting ionospheric irregularities, the radio wave experiences fading and phase fluctuation which vary widely with frequency, magnetic and solar activity, time of day, season, and latitude. This review has the objective to organize the experimental and theoretical studies

J. Aarons

1982-01-01

195

Fiber-Optical Light Collection from Scintillation Calorimeters.  

National Technical Information Service (NTIS)

A method is described for collecting light from scintillation counter calorimeters by means of an optical fiber connected to a wave length shifter, covering the edge of a scintillation plate. The optical fiber passes between continuous metallic plates and...

V. I. Kryshkin A. I. Ronzhin

1985-01-01

196

Dielectric Detection Using Resonant Radio-Frequency Waves in an Electromagnetic Cavity Device.  

National Technical Information Service (NTIS)

We describe the construction and testing of a prototype device designed to detect materials in glass and plastic containers using electrical measurement. The technique makes use of an electromagnetic cavity. A signal generator radiates a radio signal of v...

J. C. Weatherall H. F. Beckley R. Krauss

2003-01-01

197

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

198

An implicit FDTD scheme for the propagation of VLF-LF radio waves in the Earth-ionosphere waveguide  

NASA Astrophysics Data System (ADS)

A new finite-difference time-domain scheme is presented for the propagation of VLF-LF radio waves in the Earth-ionosphere waveguide. The new scheme relies on the implicit solution of the auxiliary equation that governs the current density in the ionosphere. The advantages and drawbacks of the new scheme are discussed. Its main advantage is its stability condition, which is the same as that of the FDTD method in a vacuum. This permits the time step of the calculation to be increased and then the overall computational time to be reduced. Numerical experiments demonstrate the accuracy of the new scheme and the reduction of the computational time.

Bérenger, Jean-Pierre

2014-05-01

199

Characteristics of atmospheric gravity wave activity in the polar regions revealed by GPS radio occultation data with CHAMP  

NASA Astrophysics Data System (ADS)

Using GPS radio occultation data during 2001-2005, we studied the climatological behavior of atmospheric gravity waves in the polar stratosphere. We calculated temperature fluctuations with vertical wavelengths shorter than 7 km and then determined the wave potential energy, E p , every month in a longitude-latitude cell of 20° × 10° between 12 km and 33 km. In the Arctic region (50-90°N), E p shows an annual variation with maximum in winter, consistent with the zonal mean horizontal wind, V, and the Eliassen-Palm (E-P) flux, F z . The large F z values indicate higher planetary wave activity, resulting in distortion of the polar vortex. The unbalanced flow can then excite gravity waves through geostrophic adjustment. In the Antarctic region (50-90°S), E p gradually increases during winter and reaches its maximum in spring before decreasing rapidly. The time derivative of V coincides with the E p peak and the horizontal distribution of E p has a similar structure to V, suggesting that the E p enhancement is closely related to the decay of the polar vortex. During major warming events over the Arctic, the divergence of E-P flux, ?F, was enhanced, coinciding with large E p . In the Antarctic, ?F strongly correlates with E p in spring. Gravity waves seem to be effectively generated through planetary wave transience and/or breaking. Orographic generation of gravity waves seems to be important in limited areas only, such as Scandinavia and the Antarctic Peninsula, showing that it is less important than the polar night jet in determining the climatological behavior of gravity waves.

Hei, Hayato; Tsuda, Toshitaka; Hirooka, Toshihiko

2008-02-01

200

Coorelation between VHF scintillation and spread F  

NASA Astrophysics Data System (ADS)

The VHF scintillation observed over Bhopal, a station near the northern crest of the equatorial anomaly region, using the 244 MHz radio signal from FLEETSAT (730). The data use to study the occurrence characteristics of scintillation are recorded from March to April 2001 and then September to October 2001. The occurrences of scintillation are compared with the occurrence of spread-F over Delhi as observed by the modern digital ionosonde. The scintillation events are closely associated with the range type spread-F. In this paper the parameters of geomagnetic activity like Kp and Ap are used to study the association of the amplitude scintillation and spread-F. It is observed that an increase in magnetic activity suppressed the occurrence of scintillation and spread-F.

Smita, S.; Rashmi, R.; Gwal, G.

2003-04-01

201

Modification of the high-latitude ionosphere by high-power hf radio waves. 2. Results of coordinated satellite and ground-based observations  

NASA Astrophysics Data System (ADS)

We present the results of coordinated satellite and ground-based observations of the high-latitude ionospheric phenomena induced by high-power high-frequency (HF) radio waves. The ion outflow phenomenon accompanied by a strong increase in the electron temperature and thermal expansion of plasma was observed in the evening hours, when the high-latitude ionospheric F region was heated by high-power O-mode HF radio waves. The DMSP F15 satellite recorded an increase in the ion number density O+ at an altitide of about 850 km in that period. Ultralow-frequency (ULF) radiation at the modulation frequency 3 Hz of the high-power HF radio waves, which was generated in the ionosphere irradiated by high-power O-mode HF radio waves and accompanied by a strong increase in the electron temperature and the generation of artificial small-scale ionospheric irregularities, was recorded by the CHAMP satellite during the heating experiment in Tromsø in November 5, 2009. The results of the DEMETER satellite observations of extremely low frequency (ELF) radiation at the modulation frequency 1178 Hz of the high-power radio waves in the heating experiments were analyzed using the event of March 3, 2009 as an example.

Blagoveshchenskaya, N. F.; Borisova, T. D.; Kornienko, V. A.; Rietveld, M. T.; Yeoman, T. K.; Wright, D. M.; Rother, M.; Lühr, H.; Mishin, E. V.; Roth, C.; Frolov, V. L.; Parrot, M.; Rauch, J. L.

2011-07-01

202

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

NASA Astrophysics Data System (ADS)

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 parameters on the performance of a popular operational evaporation duct model is examined. The strengths and weaknesses of this model are evaluated under specific atmospheric conditions. The relationship between the continually varying evaporation duct height and transmitter-receiver antenna geometries is analyzed, and a range of statistics related to the implications of this relationship on the received signal strength is presented. The various issues under investigation are of direct relevance in the planning of long-range, over-sea radio systems operating in the UHF band, and have implications for the radio regulatory work carried out by organizations such as the International Telecommunication Union.

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

2010-12-01

203

Refractive interstellar scintillation effects in pulsar observations  

SciTech Connect

Propagation of radio waves through the interstellar medium (ISM) produces fluctuations in the obsered intensity of a source because of the scattering caused by the irregular electron density distribution in the interstellar plasma. Under conditions of strong scintillations, the intensity fluctuations produced exhibit two predominant scales - the small scale (diffractive) fluctuations which are modulated by the large scale (refractive) fluctuations. Several aspects of the effect of refractive interstellar scintillation (RISS) in pulsar data are investigated. The results help to constrain the power spectrum of electron density fluctuations in the ISM. Some of these aspects of RISS are tested using numerical simulations of the scattering from a thin screen, for moderate ({approx}20) values of strength of scattering (U). The refractive models are not found to work as well as for the real data. Long-term fluctuations of nine pulsars were observed for fourteen months at 74 MHz using the Fallbrook antenna. The inferred modulation indices (or lower bounds thereof) for many of these pulsars are found to be higher than those predicted by the simple Kolmogorov spectrum, supporting an inner scale of the order of 10{sup 7} - 10{sup 8} m.

Gupta, Y.

1990-01-01

204

Full-wave reflection of lightning long-wave radio pulses from the ionospheric D region: Numerical model  

NASA Astrophysics Data System (ADS)

A model is developed for calculating ionospheric reflection of electromagnetic pulses emitted by lightning, with most energy in the long-wave spectral region (f ~ 3-100 kHz). The building block of the calculation is a differential equation full-wave solution of Maxwell's equations for the complex reflection of individual plane waves incident from below, by the anisotropic, dissipative, diffuse dielectric profile of the lower ionosphere. This full-wave solution is then put into a summation over plane waves in an angular direct Fourier transform to obtain the reflection properties of curved wavefronts. This step models also the diffraction effects of long-wave ionospheric reflections observed at short or medium range (~200-500 km). The calculation can be done with any arbitrary but smooth dielectric profile versus altitude. For an initial test, this article uses the classic D region exponential profiles of electron density and collision rate given by Volland. With even these simple profiles, our model of full-wave reflection of curved wavefronts captures some of the basic attributes of observed reflected waveforms recorded with the Los Alamos Sferic Array. A follow-on article will present a detailed comparison with data in order to retrieve ionospheric parameters.

Jacobson, Abram R.; Shao, Xuan-Min; Holzworth, Robert

2009-03-01

205

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

206

Full-duplex radio-over-fiber system with photonics frequency quadruples for optical millimeter-wave generation  

NASA Astrophysics Data System (ADS)

We have experimentally investigated two different schemes (schemes A and B) to generate optical millimeter-wave using optical frequency quadrupling with a Mach-Zehnder modulator (MZM), and wavelength reuse for uplink connection in the radio-over-fiber (ROF) systems. For scheme A, only one MZM is used for both the optical millimeter-wave generation and signal modulation. For scheme B, two MZMs are used. In this scheme, one of MZMs is used to generate optical millimeter-wave for frequency quadrupling, and another one is used for signal modulation. In both schemes, at the base station (BS), the optical carrier can be reused to carry upstream data and delivered to the central station (CS). By experimentally comparing the performance of downstream and upstream transmission in two schemes, it can be seen that scheme B can overcome the crosstalk between the upstream and downstream signals, but scheme A cannot. Meanwhile we also show that the millimeter-wave generated in scheme B has better quality and is almost robust to fiber chromatic dispersion.

He, J.; Chen, L.; Dong, Z.; Wen, S.; Yu, J.

2009-06-01

207

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

PubMed Central

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

TSUDA, Toshitaka

2014-01-01

208

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

PubMed

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

Tsuda, Toshitaka

2014-01-01

209

Thin Ionospheric Layers Retrieved from Galileo Radio Occultations: Forcing by Gravity Waves?  

Microsoft Academic Search

Measurements of Jupiter's ionosphere from the first Galileo radio-occultation have indicated the presence of thin electron layers below the main broad ``F-type'' peak. At ingress (24(deg) S) the SNR was sufficently large to retrieve two layers just below the 10-nbar level ~ 75 km apart having widths ~ 40 km. We suggest that these layers are driven by vertically propagating

F. M. Flasar; P. J. Schinder; D. P. Hinson

1996-01-01

210

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

211

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

212

Comparison of the three schemes to generate optical mm-wave signal and wavelength reuse for upstream connection in the radio-over-fiber systems  

NASA Astrophysics Data System (ADS)

Three different schemes to generate optical millimeter-wave and wavelength reuse for up-link connection in the radioover- fiber (ROF) systems have been theoretically and experimentally investigated. We have compared the performance of the three different schemes for the radio-over-fiber systems considering the cost and configuration of their architectures. A novel scheme to generate optical millimeter-wave and realize centralize lightwave operation in the radio-over-fiber (ROF) systems has been demonstrated. This scheme has shown high performance and low cost compared with the existing schemes.

Dong, Ze; Pi, Yazi; Lu, Jia; He, Jing; Chen, Lin

2008-11-01

213

Plastic scintillation dosimetry: Optimal selection of scintillating fibers and scintillators  

Microsoft Academic Search

Scintillation dosimetry is a promising avenue for evaluating dose patterns delivered by intensity-modulated radiation therapy plans or for the small fields involved in stereotactic radiosurgery. However, the increase in signal has been the goal for many authors. In this paper, a comparison is made between plastic scintillating fibers and plastic scintillator. The collection of scintillation light was measured experimentally for

Louis Archambault; Jean Arsenault; Luc Gingras; A. Sam Beddar; Rene? Roy; Luc Beaulieu

2005-01-01

214

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

215

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

216

Low-frequency radio monitoring of microquasars  

NASA Astrophysics Data System (ADS)

Microquasars are radio-emitting X-ray binaries (REXBs) with a radio morphology like quasars and high X-ray luminosity. Sixteen known microquasar candidates were extensively monitored for the first time at low radio frequencies using the Giant Meter-wave Radio Telescope (GMRT) between 6-June 2003 and 22-Jan. 2005 at 0.235/0.61 (simultaneous) and 1.28 GHz. Nine out of sixteen sources were detected positively by the GMRT including all six high-mass X-ray binaries (HMXBs) and three low-mass X-ray binaries (LMXBs). Among the nine sources emitting at low frequencies, six are persistent in radio and three are transient at radio wavelengths. In the case of four persistent radio sources (Scorpius X-1, Cyg X-1, Cyg X-3, and LSI+61303) the contemporaneous data suggests a spectral turnover (S sb? = ??, ? > 0) and agrees with the synchrotron self absorption (SSA) effect expected at lower frequencies. The radio spectra of SS433 and LS5039 show a power law decay (S sb? = ??, ? < 0) with no signature of SSA even at the very low frequency of 0.235 GHz. This unique result suggests either that these sources are scatter-broadened at lower frequencies or that the low-frequency radio emission from these sources are superimposed by the emission from an extended region located near these sources. Five sources, GRO J1655-40, XTE J1118+480, 1E1740.7-2942, XTE J1748-288, and GRS 1758-258 were never detected during our observations, thus suggesting that they show the SSA effect at lower frequencies or that they are too faint to be detected at GMRT frequencies. Because interstellar scintillation becomes dominant at low frequencies and may lead to flux-density fluctuations, the scintillation time scale for each microquasar was calculated and compared to the variability time scale in the data. We confirm from these studies that Cyg X-1 and SS433 are most likely affected by scintillation and that LSI+61303, LS 5039, Sco X-1, and XTE J1118+480 may possibly be affected by scintillation. A comparative study of the radio luminosity from centimeter-(GHz) to meter-wavelength (MHz) suggests a decrease by a few orders of magnitude as one goes lower in frequency. We have also plotted the RXTE/ASM X-ray light curve for all the sixteen known microquasars. Based on the ASM data, the X-ray light curve can be classified as: (a) persistent, (b) quasi-persistent or (c) transient. From the analysis of these types and the information about their companion star, the persistent or transient nature of the radio jet can be confirmed. This paper provides a general review of the main observational results obtained up to now, as well as different models for the production of low-frequency radio emissions from these sources. Table 2 is only available in electronic form at http://www.aanda.org

Pandey, M.; Rao, A. P.; Ishwara-Chandra, C. H.; Durouchoux, P.; Manchanda, R. K.

2007-02-01

217

Simulation on Generation of Electromagnetic Waves from Electron Beam: Application to Solar Type III Radio Bursts  

NASA Astrophysics Data System (ADS)

Using a two-dimensional electromagnetic and relativistic particle-in-cell (2-D EM PIC) code, we show that electromagnetic waves are excited with near fundamental plasma frequency from relativistic electron beam instability. It is also shown that electromagnetic waves with almost second harmonics can be emitted after a little time delay.

Sugiyama, D.; Sakai, J.; Nambu, M.

218

Adiabatic radio-frequency potentials for the coherent manipulation of matter waves  

SciTech Connect

Adiabatic dressed state potentials are created when magnetic substates of trapped atoms are coupled by a radio-frequency field. We discuss their theoretical foundations and point out fundamental advantages over potentials purely based on static fields. The enhanced flexibility enables one to implement numerous configurations, including double wells, Mach-Zehnder, and Sagnac interferometers which even allows for internal state-dependent atom manipulation. These can be realized using simple and highly integrated wire geometries on atom chips.

Lesanovsky, I.; Hofferberth, S.; Schmiedmayer, J. [Physikalisches Institut, Universitaet Heidelberg, D-69120 Heidelberg (Germany); Schumm, T. [Physikalisches Institut, Universitaet Heidelberg, D-69120 Heidelberg (Germany); Laboratoire Charles Fabry de l'Institut d'Optique, UMR 8105 du CNRS, F-91403 Orsay (France); Andersson, L. M. [Physikalisches Institut, Universitaet Heidelberg, D-69120 Heidelberg (Germany); Department of Microelectronics and Information Technology, The Royal Institute of Technology, KTH, Electrum 229, SE-164 40, Kista (Sweden); Krueger, P. [Physikalisches Institut, Universitaet Heidelberg, D-69120 Heidelberg (Germany); Laboratoire Kastler Brossel, 24 Rue Lhomond, 75005 Paris (France)

2006-03-15

219

The plasma perturbation evolution in F-region and the estimation of ionospheric parameters by the radio wave back sounding data  

Microsoft Academic Search

The problem of plasma perturbation, caused by the point emission of energy of value 10(exp 14) erg at altitudes of F-region, is considered. The perturbation is observed at radio wave back sounding at first 15 s after explosion. The homogeneous medium and the spherical symmetry of chare are considered. Conditions of appearance of the strong shock wave at F-region are

V. A. Pavlov; A. N. Pinegin; I. R. Smirnovskij

1993-01-01

220

GPS phase scintillation caused by conjugate auroras  

NASA Astrophysics Data System (ADS)

Auroral ionospheric irregularities produced by energetic particle precipitation are known to cause scintillation of transionospheric radio signals. The data obtained by the GPS Ionospheric Scintillation and TEC Monitors (GISTMs) operated in the Arctic and Antarctica are used in an inter-hemispheric study of GPS phase scintillation. The Canadian High Arctic Ionospheric Network (CHAIN) includes two GPS receivers in Iqaluit and Qikiqtarjuaq that are approximately conjugate with South Pole station. An all-sky imager is presently located at South Pole and the Arctic sites are equipped with riometers sensitive to energetic particle precipitation causing ionospheric density enhancements. GPS phase scintillation events closely associated with auroral brightenings and substorms were observed during ionospheric disturbances caused by high-speed solar wind streams. Instances of simultaneity of scintillation and the associated auroral events at conjugate locations are reported.

Jayachandran, P. T.; Prikryl, P.; Mitchell, C. N.; Ebihara, Y.; Weatherwax, A. T.; Danskin, D. W.; Spogli, L.

2011-12-01

221

The incoherent scattering of radio waves in a non-Maxwellian plasma: The effects of Coulomb collisions  

SciTech Connect

In this paper the formulas for the ion distribution as well as the spectrum of radio waves scattered in a magnetized plasma with a strong electric field are derived. It is shown that the presence of the electric field in the ionosphere leads to an anisotropic ion velocity distribution and, therefore, to untypical incoherent scatter spectra for the F region of the polar ionosphere which are caused by ion-neutral together with ion-ion collisions. The effect of ion-ion collisions, which has not been taken into account so far, is to reduce the anisotropy of the ion velocity distribution. Estimates of the ion-ion collision frequency derived from EISCAT measurements show that this may happen above about 300 km.

Tereshchenko, V.D.; Tereshchanko, E.D. (Polar Geophysical Inst., Murmansk (USSR)); Kohl, H. (Max-Planck-Inst. fuer Aeronomie, Katlenburg-Lindau (West Germany))

1991-10-01

222

Measurement of Attenuation Length for UHF Radio Wave in Natural Rock Salt Samples Concerning Ultra High Energy Neutrino Detection  

NASA Astrophysics Data System (ADS)

Ultra high energy (UHE ) neutrinos (E > 1015 eV) exist at any rate due to presence of the cosmic microwave background and UHE cosmic rays implied by Greisen, Zatsepin and Kuz'min (GZK). The low rate of GZK neutrinos requires us to utilize a large mass (> 50 Gton) of detection medium. The UHE neutrino generates a huge number of unpaired electrons in rock salt. They would emit sensible radio wave by coherent Cherenkov effect (Askar'yan effect). Attenuation lengths of natural rock salt samples including synthesized one at 0.3 and 1.0 GHz were measured to find a suitable site constructing a salt neutrino detector. The result indicates a possibility for constructing the salt neutrino detector with economical antenna spacing.

Chiba, Masami; Watanabe, Yusuke; Takayama, Yasuhiro; Fujii, Masatoshi; Yasuda, Osamu; Yabuki, Fumiaki; Shibasaki, Yuji; Kamijo, Toshio; Chikashige, Yuichi; Kon, Tadashi; Amano, Akio; Takeoka, Yoshito; Shimizu, Yutaka; Mori, Satoshi; Ninomiya, Sosuke; Utsumi, Michiaki

2007-03-01

223

Radio-Frequency Characteristics of the Coaxial Step-Disk-Loaded Slow-Wave Structure for Relativistic Travelling Wave Tubes  

Microsoft Academic Search

We present a new periodic all-metal slow wave structure, a coaxial step-disc-loaded system and the dispersion characteristics of the structure. By using the field-matching method, the dispersion equation and the coupling impedance of this structure are obtained. The coaxial structure makes the bandwidth broader than that of the non-coaxial one. Compared with the coaxial disc-loaded and ridged-disc-loaded structures, the pass-band

Ling-Na Yue; Wen-Xiang Wang; Yan-Yu Wei; Yu-Bin Gong

2005-01-01

224

Clumpy Langmuir waves in type III radio sources - Comparison of stochastic-growth theory with observations  

NASA Technical Reports Server (NTRS)

Detailed comparisons are made between the Langmuir-wave properties predicted by the recently developed stochastic-growth theory of type III sources and those observed by the plasma wave experiment on ISEE 3, after correcting for the main instrumental and selection effects. Analysis of the observed field-strength distribution confirms the theoretically predicted form and implies that wave growth fluctuates both spatially and temporally in sign and magnitude, leading to an extremely clumpy distribution of fields. A cutoff in the field-strength distribution is seen at a few mV/m, corresponding to saturation via nonlinear effects. Analysis of the size distribution of Langmuir clumps yields results in accord with those obtained in earlier work and with the size distribution of ambient density fluctuations in the solar wind. This confirms that the inhomogeneities in the Langmuir growth rate are determined by the density fluctuations and that these fluctuations persist during type III events.

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

1993-01-01

225

Plasma ionization through wave-particle interaction in a capacitively coupled radio-frequency discharge  

SciTech Connect

Phase resolved optical emission spectroscopy, with high temporal resolution, shows that wave-particle interactions play a fundamental role in sustaining capacitively coupled rf plasmas. The measurements are in excellent agreement with a simple particle-in-cell simulation. Excitation and ionization mechanisms are dominated by beam-like electrons, energized through the advancing and retreating electric fields of the rf sheath. The associated large-amplitude electron waves, driven by a form of two-stream instability, result in power dissipation through electron trapping and phase mixing.

O'Connell, D.; Gans, T.; Vender, D.; Czarnetzki, U.; Boswell, R. [Institute for Plasma and Atomic Physics, CPST, Ruhr-University Bochum (Germany); Port Arthur, Tasmania (Australia); Institute for Plasma and Atomic Physics, CPST, Ruhr-University Bochum (Germany); SP3/RSPhysSE, ANU, Canberra (Australia)

2007-03-15

226

Millimeter-Wave Schottky Mixer Receivers for Applications in Antenna Measurements and Radio Astronomy.  

National Technical Information Service (NTIS)

The document contains 6 individual papers. In paper 1, an embedding network for a single-ended whisker-contacted millimeter wave mixer is developed. This is based on scaled model measurements at 2.5-12 GHz (from the fundamental to the third harmonic band)...

A. O. Lehto

1990-01-01

227

Studies in Time Averaging and Wave Interference in Radio Direction Finding.  

National Technical Information Service (NTIS)

It is shown that a Watson-Watt direction finder operating under conditions of wave interference will give information allowing a digital bearing computer to determine the directions of arrival of a signal. It is shown that a two-element interferometer ope...

E. W. Ernst M. I. Glick E. C. Jones

1966-01-01

228

Plastic scintillation dosimetry: Optimal selection of scintillating fibers and scintillators  

SciTech Connect

Scintillation dosimetry is a promising avenue for evaluating dose patterns delivered by intensity-modulated radiation therapy plans or for the small fields involved in stereotactic radiosurgery. However, the increase in signal has been the goal for many authors. In this paper, a comparison is made between plastic scintillating fibers and plastic scintillator. The collection of scintillation light was measured experimentally for four commercial models of scintillating fibers (BCF-12, BCF-60, SCSF-78, SCSF-3HF) and two models of plastic scintillators (BC-400, BC-408). The emission spectra of all six scintillators were obtained by using an optical spectrum analyzer and they were compared with theoretical behavior. For scintillation in the blue region, the signal intensity of a singly clad scintillating fiber (BCF-12) was 120% of that of the plastic scintillator (BC-400). For the multiclad fiber (SCSF-78), the signal reached 144% of that of the plastic scintillator. The intensity of the green scintillating fibers was lower than that of the plastic scintillator: 47% for the singly clad fiber (BCF-60) and 77% for the multiclad fiber (SCSF-3HF). The collected light was studied as a function of the scintillator length and radius for a cylindrical probe. We found that symmetric detectors with nearly the same spatial resolution in each direction (2 mm in diameter by 3 mm in length) could be made with a signal equivalent to those of the more commonly used asymmetric scintillators. With augmentation of the signal-to-noise ratio in consideration, this paper presents a series of comparisons that should provide insight into selection of a scintillator type and volume for development of a medical dosimeter.

Archambault, Louis; Arsenault, Jean; Gingras, Luc; Sam Beddar, A.; Roy, Rene; Beaulieu, Luc [Departement de Radio-Oncologie et Centre de Recherche en Cancerologie, Hotel-Dieu de Quebec, 11 cote du palais, Quebec, Quebec G1R 2J6 (Canada) and Departement de Physique, de Genie Physique et d'Optique, Universite Laval, Quebec, Quebec (Canada); Department of Radiation Physics, University of Texas M.D. Anderson Cancer Center, Houston, Texas 77030 (United States); Department de Physique, de Genie Physique et d'Optique, Universite Laval, Quebec, Quebec (Canada); Departement de Radio-Oncologie et Centre de Recherche en Cancerologie, Hotel-Dieu de Quebec, 11 cote du palais, Quebec, Quebec G1R 2J6 (Canada) and Departement de Physique, de Genie Physique et d'Optique, Universite Laval, Quebec, Quebec (Canada)

2005-07-15

229

Plastic scintillation dosimetry: optimal selection of scintillating fibers and scintillators.  

PubMed

Scintillation dosimetry is a promising avenue for evaluating dose patterns delivered by intensity-modulated radiation therapy plans or for the small fields involved in stereotactic radiosurgery. However, the increase in signal has been the goal for many authors. In this paper, a comparison is made between plastic scintillating fibers and plastic scintillator. The collection of scintillation light was measured experimentally for four commercial models of scintillating fibers (BCF-12, BCF-60, SCSF-78, SCSF-3HF) and two models of plastic scintillators (BC-400, BC-408). The emission spectra of all six scintillators were obtained by using an optical spectrum analyzer and they were compared with theoretical behavior. For scintillation in the blue region, the signal intensity of a singly clad scintillating fiber (BCF-12) was 120% of that of the plastic scintillator (BC-400). For the multiclad fiber (SCSF-78), the signal reached 144% of that of the plastic scintillator. The intensity of the green scintillating fibers was lower than that of the plastic scintillator: 47% for the singly clad fiber (BCF-60) and 77% for the multiclad fiber (SCSF-3HF). The collected light was studied as a function of the scintillator length and radius for a cylindrical probe. We found that symmetric detectors with nearly the same spatial resolution in each direction (2 mm in diameter by 3 mm in length) could be made with a signal equivalent to those of the more commonly used asymmetric scintillators. With augmentation of the signal-to-noise ratio in consideration, this paper presents a series of comparisons that should provide insight into selection of a scintillator type and volume for development of a medical dosimeter. PMID:16121582

Archambault, Louis; Arsenault, Jean; Gingras, Luc; Beddar, A Sam; Roy, René; Beaulieu, Luc

2005-07-01

230

In-flight calibration of the Cassini-Radio and Plasma Wave Science (RPWS) antenna system for direction-finding and polarization measurements  

NASA Astrophysics Data System (ADS)

One major objective of the Cassini mission is the analysis of Saturnian radio emissions of magnetospheric (auroral) as well as atmospheric (lightning) origin. The Radio and Plasma Wave Science (RPWS) experiment is designed to measure the full polarization and the wave vector of the incoming radio waves, allowing us to retrieve information on source locations and emission modes. For that purpose, RPWS uses a two-channel receiver, connected to two electric monopoles (selected among three), which measures the voltages induced by the electric field of the incident waves and their various correlations. The accuracy of retrieved source locations depends directly on the precise knowledge of the orientation of the three effective monopole axes and lengths, which do not coincide with the physical ones owing to interaction with the spacecraft body. Antenna calibration aims at determining the so-called effective length vector of each antenna (combining orientation and length information). For that purpose, roll maneuvers of the Cassini spacecraft were performed before and after the Jupiter flyby, at distances such that Jovian radio sources can be identified with the planet's center but still provide a high signal-to-noise ratio. The resulting modulations of the measured signals allow us to derive the orientation and length of the effective antennas. The analysis is performed in two steps: first, the Stokes parameters (wave polarization) are determined using approximate antenna orientations derived from laboratory measurements on a scale model of the spacecraft. Second, measurements with high signal-to-noise ratio and pure circular polarization are selected and used for the determination of the effective length vectors of the RPWS antennas. Two methods have been developed for inverting the system of equations relating antenna parameters, wave parameters, and measurements (least squares fit and analytical inversion), both of which provide consistent results and present different advantages and limitations which are discussed. A final set of antenna parameters to be used for direction finding studies with the RPWS experiment is obtained.

Vogl, Dieter F.; Cecconi, Baptiste; Macher, Wolfgang; Zarka, Philippe; Ladreiter, Hans Peter; FéDou, Pierre; Lecacheux, Alain; Averkamp, Terry; Fischer, Georg; Rucker, Helmut O.; Gurnett, Donald A.; Kurth, William S.; Hospodarsky, George B.

2004-09-01

231

Electromagnetic modelling with wave tilt and reflection coefficient: an application to stratified earth media using low and radio frequencies  

NASA Astrophysics Data System (ADS)

Many models using electromagnetic sounding techniques have been formulated for use in exploration activities. In deriving the governing equations for the models, Maxwell's equations are used and the earth is taken as a layered medium. Using these boundary conditions, the Sommerfeld integrals are obtained for several models. However, the difficulties and limitations posed by the iterations of the functions, especially the strong oscillations and slow convergence of the Bessel function, call for a search for new methods. This work aims to formulate models, with the advantage of bypassing the problems highlighted above, and to discover new response parameters not considered by the older models due to the limitations of time. Three measurable field parameters, (1) amplitude of the correction factor to the wave tilt, (2) phase of the amplitude of the correction factor to the wave tilt and (3) reflection coefficient, were calculated from this model with various conductivity contrasts over a two-layered earth. Two cases of a top layer overlying a more conductive basement and a more conductive top layer overlying a resistive basement were considered with a radio frequency of 125 kHz and a low frequency of 10 Hz. The model was tested using data from existing models and was then applied to a homogeneous and a layered earth. Results revealed that the phase of the amplitude of the correction to the wave tilt was found to be most diagnostic of the changes in layer parameters. Also, depths of 20 m and 2000 m were achieved with the two respective frequency values. The reflection coefficient was discovered to be an important parameter for detecting layered earth structures, in addition to other parameters. Furthermore, an inverse relationship between the transverse electric and transverse magnetic modes of the reflection coefficient is established.

Olowofela, J. A.; Ozebo, V. C.

2006-06-01

232

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

233

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

NASA Astrophysics Data System (ADS)

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

Kochetov, Andrey

234

Ooty Interplanetary Scintillation - Remote-Sensing Observations and Analysis of Coronal Mass Ejections in the Heliosphere  

Microsoft Academic Search

In this paper, I investigate the three-dimensional evolution of solar wind density and speed distributions associated with coronal mass ejections (CMEs). The primary solar wind data used in this study has been obtained from the interplanetary scintillation (IPS) measurements made at the Ooty Radio Telescope, which is capable of measuring scintillation of a large number of radio sources per day

P. K. Manoharan

2010-01-01

235

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

NASA Astrophysics Data System (ADS)

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

Kochetov, Andrey; Menkova, Uliya; Grach, Savely

236

The thresholds of ionospheric plasma instabilities pumped by high-frequency radio waves at EISCAT  

NASA Astrophysics Data System (ADS)

We test the existing theories regarding the thresholds for the parametric decay instability (PDI), the oscillating two-steam instability (OTSI), and the thermal parametric instability (TPI) using the European Incoherent Scatter (EISCAT) facility's ionospheric heater. In these processes, the pump wave can couple to various electrostatic waves in the F layer ionosphere, which can be observed using the EISCAT UHF radar (PDI and OTSI) or by HF radar (TPI). On 19 October 2012, the heater power was stepped from ˜0.5 MW to ˜100 MW effective radiated power in seven steps using a 1 min on, 1 min off cycle. We use an electric field model, taking into account D region absorption, to compare theory with our observations. In all three cases, we find good agreement. In addition, the growth of striations formed during the TPI causes anomalous absorption of the heater wave, which we observe as decreased UHF ion line and plasma line backscatter power. We show evidence that heating for a prolonged period of time reduces the UHF ion line intensity throughout the experiment.

Bryers, C. J.; Kosch, M. J.; Senior, A.; Rietveld, M. T.; Yeoman, T. K.

2013-11-01

237

Radio wave propagation from antennae at satellite altitudes into the earth-ionosphere waveguide  

NASA Astrophysics Data System (ADS)

The problem of the excitation of the earth-ionosphere waveguide by a short linear antenna or by a small circular one at satellite altitudes is considered. The formulation allows for a spherical regular wave guide as well as for a radially inhomogeneous anisotropic ionsphere. A method for the solution is based on the use of the reciprocity theorems for anisotropic media. Numerical techniques have been developed. Some results for VLF are given. To gain some physical interpretations, the fields of sources at low ionospheric heights were investigated.

Rybachek, S. T.

1995-03-01

238

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

NASA Astrophysics Data System (ADS)

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

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

2000-07-01

239

Sixty gigahertz indoor radio wave propagation prediction method based on full scattering model  

NASA Astrophysics Data System (ADS)

In radio system deployment, the main focus is on assuring sufficient coverage, which can be estimated with path loss models for specific scenarios. When more detailed performance metrics such as peak throughput are studied, the environment has to be modeled accurately in order to estimate multipath behavior. By means of laser scanning we can acquire very accurate data of indoor environments, but the format of the scanning data, a point cloud, cannot be used directly in available deterministic propagation prediction tools. Therefore, we propose to use a single-lobe directive model, which calculates the electromagnetic field scattering from a small surface and is applicable to the point cloud, and describe the overall field as fully diffuse backscattering from the point cloud. The focus of this paper is to validate the point cloud-based full diffuse propagation prediction method at 60 GHz. The performance is evaluated by comparing characteristics of measured and predicted power delay profiles in a small office room and an ultrasonic inspection room in a hospital. Also directional characteristics are investigated. It is shown that by considering single-bounce scattering only, the mean delay can be estimated with an average error of 2.6% and the RMS delay spread with an average error of 8.2%. The errors when calculating the azimuth and elevation spreads are 2.6° and 0.6°, respectively. Furthermore, the results demonstrate the applicability of a single parameter set to characterize the propagation channel in all transmit and receive antenna locations in the tested scenarios.

Järveläinen, J.; Haneda, K.

2014-04-01

240

Drift of ionospheric scintillation irregularities at subtropical latitudes  

NASA Astrophysics Data System (ADS)

Using simultaneous observations of VHF radio wave scintillations from two closely spaced satellites, SIRIO at 65 deg E, (transmitting on 136 MHz) and FLEETSAT at 73 deg E (transmitting on 244 MHz), the characteristic properties of the ionospheric irregularities over a tropical station, Bombay have been deduced. It has been shown that usual E-W patch size observed at this latitude is of the order of 200-400 km, and these irregularity patches drift from West to East with a drift speed of about 170 m/s around 2100 h which decreases in the course of night to about 60 m/s by 0500 h. Drift speeds at any time of the night are lower on magnetically disturbed than on quiet days.

Koparkar, P. V.

1988-04-01

241

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

NASA Astrophysics Data System (ADS)

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 km to the north-west, and the Kodiak SuperDARN radar, 856 km to the south-west. Camera observations of the stimulated optical emissions at 557.7 nm (O1S, threshold 4.2 eV) and 630 nm (O1D, threshold 2 eV) were made, allowing tomographic reconstruction of the volume emission. The first observations of pump-induced 732 nm (O+, threshold 18.6 eV) emissions are reported. Kodiak radar backscatter, which is a proxy for upper-hybrid resonance, shows strong production of striations without a minimum on the second gyroharmonic, confirming previous results. PFISR analysis shows clear evidence of electron temperature enhancements, consistent with previous EISCAT results, maximizing when the pump frequency matches the second gyroharmonic and when double resonance occurs, i.e. the upper-hybrid resonance frequency matches the second gyroharmonic. This is consistent with the optical observations. From the above data, we are able to infer the efficiency of different groups of electron-accelerating mechanisms.

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

242

Proton injector operational results on a high-power continuous-wave radio-frequency quadrupole accelerator  

SciTech Connect

A 50 keV proton injector utilizing a dc microwave source has been used to operate a 1.25 MeV continuous wave (cw) radio-frequency quadrupole (RFQ) accelerator. RFQ injection places stringent requirements on beam properties including centroid control, emittance, and phase-space matching. The ion source chosen for these applications is based on a microwave discharge operating at 2.45 GHz with an on-axis magnetic field near 875 G. The injector employs a space-charge-neutralized, two-solenoid-lens, low-energy beam transport (LEBT) system. Proton injector development with a 1.25 MeV RFQ has resulted in meeting the RFQ 75 mA design current specification in cw mode. Details of the ion source and LEBT operation are presented, and simulations for ion beam extraction and transport are compared with the injector measurements. The proton injector has been converted to 75 keV beam operation for injecting into a 6.7 MeV cw RFQ. (c) 2000 American Institute of Physics.

Sherman, Joseph D. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Bolme, Gerald O. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Hansborough, Lash D. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Hardek, Thomas W. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Kerstiens, Debora M. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States); Meyer, Earl A.; Schneider, J. David; Smith, H. Vernon Jr.; Stettler, Matthew W.; Stevens, Ralph R. Jr. [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)] (and others) [Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)

2000-02-01

243

Scenario Machine: fast radio bursts, short gamma-ray burst, dark energy and Laser Interferometer Gravitational-wave Observatory silence  

NASA Astrophysics Data System (ADS)

We discuss the recently reported discovery of fast radio bursts (FRBs) in the framework of the neutron star-neutron star (NS+NS) or neutron star-black hole (NS+BH) binary merger model. We concentrate on what we consider to be an issue of greatest importance: what is the NS merger rate given that the FRB rate (1/1000 yr-1 per galaxy) is inconsistent with gamma-ray burst rate as discussed by Thornton and should be significantly higher. We show that there is no discrepancy between NS merger rate and observed FRB rates in the framework of the Scenario Machine population synthesis - for a kick velocity of 100-150 km s-1 an average NS merger rate is 1/500-1/2000 yr-1 per galaxy up to z = 0.5-1. Based on the Scenario Machine NS merger rate estimates, we discuss the lack of positive detections on the ground-based interferometers, considering the Laser Interferometer Gravitational-wave Observatory.

Lipunov, V. M.; Pruzhinskaya, M. V.

2014-05-01

244

Coronal fast wave trains of the decimetric type IV radio event observed during the decay phase of the June 6, 2000 flare  

NASA Astrophysics Data System (ADS)

The 22 min long decimetric type IV radio event observed during the decay phase of the June 6, 2000 flare simultaneously by the Brazilian Solar Spectroscope (BSS) and the Ond?ejov radiospectrograph in frequency range 1200-4500 MHz has been analyzed. We have found that the characteristic periods of about 60 s belong to the long-period spectral component of the fast wave trains with a tadpole pattern in their wavelet power spectra. We have detected these trains in the whole frequency range 1200-4500 MHz. The behavior of individual wave trains at lower frequencies is different from that at higher frequencies. These individual wave trains have some common as well as different properties. In this paper, we focus on two examples of wave trains in a loop segment and the main statistical parameters in their wavelet power and global spectra are studied and discussed.

Mészárosová, H.; Sawant, H. S.; Cecatto, J. R.; Rybák, J.; Karlický, M.; Fernandes, F. C. R.; de Andrade, M. C.; Ji?i?ka, K.

2009-05-01

245

The transmission performance of the single sideband optical millimeter-wave with BPSK signal in the duplex radio-over-fiber link  

NASA Astrophysics Data System (ADS)

This paper has investigated the transmission performance of the single sideband (SSB) optical millimeter (mm)-wave with signal carried by the sideband in BPSK format in duplex radio-over-fiber (RoF) system theoretically and numerically. The SSB optical mm-wave signal is generated by a LiNbO 3 Mach-Zehnder modulator and there exists an optimal modulation index to generate the SSB optical mm-wave with a maximal RF photocurrent. The SSB optical mm-wave is much suitable for the duplex ROF link with the uplink lightwave recovered from the downlink because the optical carrier carries no signal. In such a duplex RoF link, although there are the spurs on the optical carrier, they have little influence on the downlink and the uplink signal even if the modulation index is large.

Ma, Jianxin; Yu, J.; Xin, Xiangjun; Yu, Chongxiu; Huang, Huiying; Rao, Lan

2008-10-01

246

GPS and ionospheric scintillations  

Microsoft Academic Search

Ionospheric scintillations are one of the earliest known effects of space weather. Caused by ionization density irregularities, scintillating signals change phase unexpectedly and vary rapidly in amplitude. GPS signals are vulnerable to ionospheric irregularities and scintillate with amplitude variations exceeding 20 dB. GPS is a weak signal system and scintillations can interrupt or degrade GPS receiver operation. For individual signals,

P. M. Kintner; B. M. Ledvina; E. R. de Paula

2007-01-01

247

Attenuation of high-frequency radio waves in the low ionosphere at high latitudes when the ionosphere is artificially perturbed by powerful radio emission  

Microsoft Academic Search

We have discovered a significant (up to 60% and more) attenuation of the intensity of high frequency probe signals received from the low nighttime ionosphere at high altitudes. The reason for the attenuation is that the ionosphere is being influenced by powerful shortwave radio emission. The Polar Geophysical Institute (PGI) was set up so that powerful shortwave radiation could artificially

S. I. Martynenko; V. A. Misyura; V. G. Simov; L. F. Chernogor; A. S. Shemet

1983-01-01

248

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

NASA Astrophysics Data System (ADS)

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

Cremonini, Andrea; Mariotti, Sergio; Valenziano, Luca

2012-09-01

249

Problems in the use of plastic scintillators in intense radiation fields.  

National Technical Information Service (NTIS)

Annual doses in the SDC End Cap Calorimeter, and possible design decisions in the use of radiation resistant scintillators are discussed. Some candidates for base radiation tolerant scintillators and wave length shifters are discussed. Absorption and emis...

S. Cherny

1992-01-01

250

Innovative traveling-wave optoelectronic devices for radio over fiber and terahertz applications  

NASA Astrophysics Data System (ADS)

The structure of conventional optoelectronic devices for new high frequency applications as well as the integration with other devices may be modified by using low-loss microwave waveguides. Also the concept of substrate integrated circuits (SICs), which has widely been used in the microwave domain, can be utilized for the integration of optoelectronic devices at millimetre wave (mmW) and sub-mmW frequency ranges. Substrate integrated waveguide (SIW) derived from the general SICs concept is a planar form of rectangular waveguide (RWG) with some metalized via holes instead of metallic side walls of RWG. New optoelectronic devices and in particular TW photodetector and modulator can be proposed based on SIW structure for mmW frequency, terahertz (THz) photonics and electro-optical applications. SIW is considered to propose new types of TW electro-optical modulators. Band-pass LiNbO3 electro-optical phase and amplitude SIW and hybrid SIW-CPW modulators are two types of the proposed devices in this work. The field overlap integral, half-wave voltage, modulation depth and bandwidth are the most important parameters in the design and characterisation of optical modulators which can be optimized for our proposed modulators. For the design of the SIW modulator, the field interaction between the microwave/mmW and optical signals in wide thick SIW and in narrow optical waveguide, respectively, is not considerable and thus low field overlap integral is obtained. This is also because of the half-sinusoidal field distribution of TE10 mode in the transverse cross-section of SIW. Furthermore, the microwave/mmW loss of a thin layer SIW to increase the overlap integral is significantly high which affects the modulation depth and bandwidth of the modulator. Therefore, to improve the overlap integral or half-wave voltage and to have simultaneously acceptable mmW loss or bandwidth of the new phase modulator, a structure with a thin LiNbO3 layer including the use of an optical waveguide array in the top of a thick LiNbO3 layer is designed and optimized. Different structures for array optical waveguides are designed and then modulator parameters are calculated. Also, an optical band-pass LiNbO3 amplitude modulator is introduced based on the SIW phase modulator. The hybrid SIW-CPW modulator is another type of our new designed band-pass electro-optical amplitude modulators using a special coupling mechanism between CPW and SIW for mmW frequencies. This structure preserves the advantages of high field interaction between the optical and microwave signals along CPW electrode structure as well as the advantages of low-loss SIW structure. This is in particular important for mmW packaging, which is critical for practical applications of electro-optical devices. Coupling from SIW to CPW is increased in the half first part of the modulation region and maximized in the middle of the proposed modulator. In the second half part, this coupling happens from CPW to SIW and the output microwave signal can be used in the integrated systems. Overlap integral of this device increases gradually while the microwave signal is transferred to the CPW along the propagation path. The mode coupling mechanism between CPW and SIW in this structure results in a band-pass amplitude modulator for mmW applications. For the probing-station measurement and the validation of the simulated results, CPW to SIW transitions are designed and optimized. THz source generation using photodetectors and photomixing techniques are also studied and realized in this thesis. Surface-type photoconductive as a photomixer as well as the integration of this photomixer with a spiral antenna are designed and fabricated for THz frequencies. Optical signal from dual-wavelength laser diode is detected by the photomixer with interdigitated fingers and the generated THz signal is then radiated from the back side of the substrate. Design and optimization of the photodetector and spiral antenna, design of multi-layer masks, fabrication and measurement of integrated circuits are presented in this work. (A

Mortazy, Ebrahim

251

Pulsar scintillation patterns and strangelets  

NASA Astrophysics Data System (ADS)

We propose that interstellar extreme scattering events, usually observed as pulsar scintillations, may be caused by a coherent agent rather than the usually assumed turbulence of H2 clouds. We find that the penetration of a flux of ionizing, positively charged strangelets or quark nuggets into a dense interstellar hydrogen cloud may produce ionization trails. Depending on the specific nature and energy of the incoming droplets, diffusive propagation or even capture in the cloud are possible. As a result, enhanced electron densities may form and constitute a lens-like scattering screen for radio pulsars and possibly for quasars.

Pérez-García, M. Ángeles; Silk, Joseph; Pen, Ue-Li

2013-12-01

252

How many radio relics await discovery?  

Microsoft Academic Search

Upcoming radio telescopes will allow to study the radio sky at low frequencies with unprecedent sensitivity and resolution. New surveys are expected to discover a large number of new radio sources. Here we investigate the abundance of radio relics, i.e. steep-spectrum diffuse radio emission coming from the periphery of galaxy clusters, which are believed to trace shock waves induced by

S. E. Nuza; M. Hoeft; R. J. van Weeren; S. Gottloeber; G. Yepes

2011-01-01

253

Hyperstrong Radio-Wave Scattering in the Galactic Center. II. A Likelihood Analysis of Free Electrons in the Galactic Center  

NASA Astrophysics Data System (ADS)

The scattering diameters of Sgr A* and several nearby OH masers (~1" at 1 GHz) indicate that a region of enhanced scattering is along the line of sight to the Galactic center. We combine radio-wave scattering data and free-free emission and absorption measurements in a likelihood analysis that constrains the following parameters of the GC scattering region: The GC-scattering region separation, ?GC the angular extent of the region, ?l and ?b the outer scale on which density fluctuations occur, l0; and the gas temperature, Te. The maximum likelihood estimates of these parameters are ?GC=133+200-80 pc, 0.5d<=?l<~1deg, and (l0/1 pc)2/3T-1/2e=10-7+/-0.8. The parameter ?b was not well constrained, and we adopt ?b = 0.5d. The close correspondence between ?GC and ?lDGC suggests that the scattering region encloses the GC. As host media for the scattering, we consider the photoionized surface layers of molecular clouds and the interfaces between molecular clouds and the 107 K ambient gas. We are unable to make an unambiguous determination, but we favor the interface model in which the scattering medium is hot (Te ~ 106 K) and dense (ne ~ 10 cm-3). The GC scattering region produces a 1 GHz scattering diameter for an extragalactic source of 90", if the region is a single screen, or 180", if the region wraps around the GC, as appears probable. We modify the Taylor-Cordes model for the Galactic distribution of free electrons in order to include an explicit GC component. We predict that pulsars seen through this region will have a dispersion measure of approximately 2000 pc cm-3, of which approximately 1500 pc cm-3 arises from the GC component itself. We stress the uniqueness of the GC scattering region, probably resulting from the high-pressure environment in the GC.

Lazio, T. Joseph W.; Cordes, James M.

1998-10-01

254

Scintillation Hole Observed by FORMOSAT-3/COSMIC  

NASA Astrophysics Data System (ADS)

Ionospheric scintillations can significantly disturb satellite positioning, navigation, and communication. FORMOSAT-3/COSMIC provides the first 3-D global observation by solo instrument (radio occultation experiment, GOX). The GPS L-band amplitude fluctuation from 50Hz signal is received and recorded by F3/C GOX to calculate S4-index from 50-800km altitude. The global F3/C S4 index are subdivided and examined in various latitudes, longitudes, altitudes, and seasons during 2007-2012. The F-region scintillations in the equatorial and low-latitude ionosphere start around post-sunset period and often persist till post-midnight hours (0300 MLT, magnetic local time) during the March and September equinox as well as December Solstice seasons. The E-region scintillations reveal a clear solar zenith effect and yield pronounced intensities in mid-latitudes during the Summer Solstice seasons, which are well correlated with occurrences of the sporadic E-layer. It is interesting to find there is no scintillation, which is termed "scintillation hole", in the E region ranging from 80 to 130km altitude over the South Africa region, and become the most pronounced in November-January (December Solstice seasons or summer months). Other space-borne and ground based observations are use to confirm the existence of the scintillation hole.

Chen, Shih Ping; Yenq Liu, Jann; Krishnanunni Rajesh, Panthalingal

2013-04-01

255

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

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

256

Application of Digital Industrial Photogrammetric Technology to Measure the Surface Accuracy of 13.7 m Millimeter-wave Radio Telescope Antenna  

NASA Astrophysics Data System (ADS)

In this paper, the surface accuracy of 13.7 m millimeter-wave radio telescope antenna is measured by digital industrial photogrammetric technology. In order to overcome the inconvenience introduced by local conditions, the circular orbits are used to transport the camera and wireless transmission is used to take on-line photos. Measuring targets are made of retro-reflective material. All camera stations are orientated and the homologous image points are matched automatically by the coded targets. The 3D point coordinates are calculated by the bundle adjustment method. Using the methods of CAD surface conversion algorithm and best fitting to calculate the deviation value of the surface, the RMS of the 480 points gotten from CAD best fitting algorithm is adjusted to 0.083 mm. The feasibility and superiority of photogrammetric technology, which is used to measure the radio astronomy antenna's surface, is demonstrated.

Fan, Q. H.; Fang, S. H.; Zuo, Y. X.; Li, Y.; Sun, J. X.; Yang, J.; Li, J. J.; Xu, Y.; He, D. Y.

2010-04-01

257

First IPS Radio Sources Detected By MEXART  

Microsoft Academic Search

We present a first study of strong radio sources that are known to exhibit interplanetary scintillations (IPS) detected by the Mexican Array Radio Telescope (MEXART). These observations were made using one quarter of the total antenna (16 rows of 64 dipoles each) and a Butler Matrix (BM) of 16X16 ports. The BM displays 16 beams at different declinations (from -48

J. Mejia-Ambriz; A. Gonzalez-Esparza; A. Carrillo-Vargas; P. Villanueva-Hernandez; E. Aguilar-Rodriguez; E. Andrade-Mascote; S. Vazquez-Hernandez; P. Sierra-Figueredo; S. Ananthakrishnan; P. Manoharan

2008-01-01

258

Scintillators and applications thereof  

US Patent & Trademark Office Database

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

2014-07-15

259

Scintillator Manufacture at Fermilab.  

National Technical Information Service (NTIS)

A decade of research into plastic scintillation materials at Fermilab is reviewed. Early work with plastic optical fiber fabrication is revisited and recent experiments with large-scale commercial methods for production of bulk scintillator are discussed....

K. Mellott A. Pla-Dalmau

1998-01-01

260

Monitoring and Forecasting Ionospheric Scintillation at High Latitudes (Invited)  

NASA Astrophysics Data System (ADS)

Ionospheric scintillation (rapid signal amplitude fading and phase fluctuation) poses a threat to reliable and safe operation of modern technology that relies on Global Navigation Satellite Systems (GNSS). Ionospheric scintillation of GNSS signal severely degrades positional accuracy, causes cycle slips leading to loss of lock that affects performance of radio communication and navigation systems. At high latitudes, the scintillation is caused by ionospheric irregularities produced through coupling between solar wind plasma and the magnetosphere. Climatology of GPS scintillation at high latitudes in both hemispheres shows that phase scintillation occurs predominantly on the dayside in the cusp and in the nightside auroral oval. Solar wind disturbances, in particular the co-rotating interaction regions (CIR) on the leading edge of high-speed streams (HSS) and interplanetary coronal mass ejections (ICME), have been closely correlated with the occurrence of scintillation at high latitudes. These results demonstrated a technique of probabilistic forecast of high-latitude phase scintillation occurrence relative to arrival times of HSS and ICME. The Canadian High Arctic Ionospheric Network (CHAIN) has been monitoring GPS ionospheric scintillation and total electron content (TEC) since November 2007. One-minute amplitude and phase scintillation indices from L1 GPS signals and TEC from L1 and L2 GPS signals are computed from amplitude and phase data sampled at 50 Hz. Since 2012, significant expansion of CHAIN has begun with installation of new receivers, each capable of tracking up to 30 satellites including GLONASS and Galileo. The receivers log the raw phase and amplitude of the signal up to a 100-Hz rate for scintillation measurements. We briefly review observations of ionospheric scintillation and highlight new results from CHAIN, including the climatology of scintillation occurrence, collocation with aurora and HF radar backscatter, correlation with CIRs and ICMEs, and the method of probabilistic forecasting of phase scintillation at high latitudes.

Prikryl, P.; Jayachandran, P. T.; Chadwick, R.; Kelly, T.

2013-12-01

261

Scintillator manufacture at Fermilab  

SciTech Connect

A decade of research into plastic scintillation materials at Fermilab is reviewed. Early work with plastic optical fiber fabrication is revisited and recent experiments with large-scale commercial methods for production of bulk scintillator are discussed. Costs for various forms of scintillator are examined and new development goals including cost reduction methods and quality improvement techniques are suggested.

Mellott, K.; Bross, A.; Pla-Dalmau, A.

1998-08-01

262

Scintillator manufacture at Fermilab  

SciTech Connect

A decade of research into plastic scintillation materials at Fermilab is reviewed. Early work with plastic optical fiber fabrication is revisited and recent experiments with large-scale commercial methods for production of bulk scintillator are discussed. Costs for various forms of scintillator are examined and new development goals including cost reduction methods and quality improvement techniques are suggested.

Mellott, K.; Bross, A.; Pla-Dalmau, A. [Fermi National Accelerator Laboratory, Batavia, Illinois 60510 (United States)

1998-11-09

263

Lead carbonate scintillator materials  

DOEpatents

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

Derenzo, Stephen E. (Pinole, CA); Moses, William W. (Berkeley, CA)

1991-01-01

264

Scintillator materials for calorimetry  

SciTech Connect

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

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

1994-09-01

265

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

266

Analysis of GPS ionospheric scintillation measurements at high latitudes  

NASA Astrophysics Data System (ADS)

Transionospheric radio signals may experience fluctuations in their amplitude and phase due to irregularity in the spatial electron density distribution, referred to as scintillation. Ionospheric scintillation is responsible for transionospheric signal degradation that can affect the performance of satellite based navigation systems. Usually, the scintillation activity is measured by means of indices such as the normalised standard deviation of the received intensity and the standard deviation of the received phase. Statistical analyses on the use of an additional index are carried out based on 50 Hz GPS measurements recorded at Dirigibile Italia Station (Ny-Alesund, Svalbard). The usefulness of such an additional parameter for the characterization of the phase scintillation activity is discussed and advanced. Also, the understanding of the signal dynamics due to ionospheric electron density irregularities is attempted by using such a new estimate for the phase scintillation.

Forte, B.; Materassi, M.; Alfonsi, L.; Romano, V.; Spalla, P.; de Franceschi, G.

2009-04-01

267

Project COST 205 - Scintillations in earth-satellite links  

NASA Astrophysics Data System (ADS)

The results of investigations on the fluctuations of the amplitude of signals in earth-satellite paths are described. Annual as well as seasonal and diurnal statistics on scintillations occurring in radio paths are briefly discussed, and histograms of the signal variance for two antennas are shown. It is noted that although the signal variance is always smaller when measured with the larger antenna, the differences are much less in summer than in winter. Severe scintillations are recorded around noon and are mostly associated with cumulus clouds. Weak scintillations show a second maximum of activity in the early morning. Antenna size effects on signal amplitude fluctuations are summarized.

1985-06-01

268

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

NASA Astrophysics Data System (ADS)

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 altitude at which the critical frequency {f_{x{F_2}}} of the F 2 layer is equal to the frequency f H of the heating accompanied by an up to 50% increase in the electron temperature. The spatial structure of the artificially perturbed ionospheric F region is examined in detail using an incoherent scatter radar operated in the regime of scanning over elevation angles from 92° to 74° with a 2° step. It is shown that the spatial size of the heated patch strongly depends on the angle of the HF pumping relative to the Earth's magnetic field. The phenomena occurring in the artificially modified ionospheric F region heated at frequencies near the third electron gyroharmonic, i.e., at f H = 3 f ce = f UH, where f UH is the upper-hybrid frequency, are explored on the basis of multi-instrument observation data.

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

2011-02-01

269

The Sardinia Radio Telescope  

NASA Astrophysics Data System (ADS)

We describe the Sardinia Radio Telescope (SRT), a new general purpose, fully steerable antenna of the National Institute for Astrophysics. The radio telescope is under construction near Cagliari (Sardinia). With its large aperture (64m diameter) and its active surface, SRT is capable of operations up to ˜100GHz, it will contribute significantly to VLBI networks and will represent a powerful single-dish radio telescope for many science fields. The radio telescope has a Gregorian optical configuration with a supplementary beam-waveguide (BWG), which provides additional focal points. The Gregorian surfaces are shaped to minimize the spill-over and standing wave. After the start of the contract for the radio telescope structural and mechanical fabrication in 2003, in the present year the foundation construction will be completed. The schedule foresees the radio telescope inauguration in late 2006.

Grueff, G.; Alvito, G.; Ambrosini, R.; Bolli, P.; D'Amico, N.; Maccaferri, A.; Maccaferri, G.; Morsiani, M.; Mureddu, L.; Natale, V.; Olmi, L.; Orfei, A.; Pernechele, C.; Poma, A.; Porceddu, I.; Rossi, L.; Zacchiroli, G.

270

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

271

Observations of Scintillations of Two Satellite Beacons near the Boundary of the Irregularity Region.  

National Technical Information Service (NTIS)

By using observations of the scintillations of two synchronous satellite beacons, ATS-3 and Intelsat 2F-3, from the Sagamore Hill Radio Observatory, comparisons could be made for ionospheric characteristics at the boundary of the high latitude irregularit...

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

1972-01-01

272

Radio Signatures of November 1998 Leonid Meteor on Transionospheric VHF Satellite Signal  

NASA Astrophysics Data System (ADS)

This letter presents, to our knowledge for the first time, two cases of scintillations of the 244 MHz satellite beacon signal recorded from the geostationary satellite FLEETSATCOM (FSC) (Long: 73°E) at the Haringhata Field Station (HFS) (Lat: 22.97°N Long: 88.50°E Dip: 32°N) of the University of Calcutta on the night of November 16/17, 1998, which corresponds to the peak period of the Leonid meteor shower in terms of its rate and visual magnitude. Scintillations produced by the sporadic-E layer (E s) generated by meteoric ionization are transient and quasi-periodic in nature. This type of scintillations have much shorter durations (˜30-100 s) than those normally observed at night in the equatorial latitudes (˜5 min to couple of hours). It is characterized by a primary deep fade out in field strength, associated with regular ringing patterns before and after it. Generation of quasi-periodic scintillations is believed to be due to a small-scale (scale size ˜100-1000 m) density enhancement or blob which acts as a radio lens in the path of the transionospheric signal. Assuming one-dimensional density irregularities, the peak phase deviation introduced in the radio wave passing through is estimated. The observed scintillation patterns have been simulated considering a series of isolated ionospheric irregularities of different strengths and scale sizes. Critical frequency of the E s layer (f 0E s) measured by the Ahmedabad ionosonde (Lat: 23.03 0N Long: 72.40 0E Dip: 34°N) for the same night shows two isolated spikes which may be due to a sudden increase in plasma density caused by meteoric ionization. In addition, the meteor visual magnitude and cumulative mean flux have been calculated using the meteor intensity data available on the Internet.

Paul, A.; Ray, S.; DasGupta, A.; Chandra, H.

2001-06-01

273

Recent development in organic scintillators  

NASA Technical Reports Server (NTRS)

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

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

1969-01-01

274

The equatorial ionospheric scintillations during geomagnetic storms  

NASA Astrophysics Data System (ADS)

Geomagnetic storms and disturbances are thought to play an important role for initiation of the ionospheric scintillations. Scintillation manifest itself in rapid fluctuation of the phase and intensity of a radio signal that has passed through the Earth's ionosphere, typically on a satellite-to-ground propagation channel. Mechanisms of ionospheric scintillation are better understood than its morphology and serious efforts were made to find the empirical relationships in terms of different geomagnetic indices for their forcasting. Such relationships can help to avoid blackouts and distortions in VLF communication due to ionospheric irregularities. We used the different geomagnetic indices, the ionospheric parameters, and the Bz-component of the interplanetary magnetic field (IMF) to study scintillation activity at the dip latitudes. The relationship between the equatorial ionospheric scintillations and the IMF Bz, Dst, Kp, AU, and AL indices is demonstrated. It is shown that in parallel with much used of Dst- index other indices are also suitable for study of scintillation activity. For example, Kp as planetary index carries information about auroral electrojets also and we can see that no scintillation activity when Kp decreases during positive IMF Bz. This means that the auroral electrojets depicted by the AU, and AL-indices and connected with the field-aligned currents (FAC) are decreased and moved to pole ward. The positive IMF Bz is likely to be the factor that inhibits the equator ward penetration of the high latitude electric field. The negative IMF Bz enhances the auroral electric fields and they can penetrate to the equatorial ionosphere. The examples presented in our study allow us to assume that the southward IMF Bz by the Region 1 FAC can form an additional eastward current system at the equatorial ionosphere. Under these conditions the virtual height h'F rises to high altitudes and when it drops the scintillations can be generated. It may be safely suggested that source of this phenomenon is the solar wind electric field responcible for the auroral and equatorial ionosphere coupling. Other processes such as tides, earthquakes etc. can change the ionospheric height also and may play a role in the generation of the ionospheric scintillations. From a practical point of view, the relationships between the solar wind and the ionospheric parameters can be used for the prediction of scintillations, if one takes into account the time delay between the IMF Bz and the equatorial ionospheric data.

Biktash, L.

275

Kinematics of ICMEs Deduced From Remote Radio Observations  

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

276

Estimating the amplitude scintillation index from sparsely sampled phase screen data  

Microsoft Academic Search

Phase screen techniques are commonly used to model scintillation of radio signals passing through a disturbed ionosphere, but observational phase or in situ density from both archival and real-time sources is often sampled at rates well below the resolution desired for input to such models. Previous phase screen resolution criteria do not address the computation of the amplitude scintillation index

T. L. Beach; T. R. Pedersen; M. J. Starks; S.-Y. Su

2004-01-01

277

Lead carbonate scintillator materials  

DOEpatents

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

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

1991-05-14

278

Features of solar wind acceleration according to radio occultation data  

NASA Technical Reports Server (NTRS)

In addressing one of the fundamental problems in solar physics establishing the mechanism(s) responsible for the solar wind acceleration and the corona heating - it is essential to have a reliable knowledge of the heliocentric radial dependence of the solar wind properties. Adequate data are available for small solar distances R less than 4 R(solar mass) from coronal white light and EUV observations and at distances R greater than 60 R(solar mass) from in situ measurements. One of the few methods available to fill in the gap between these boundaries is the radio scintillation technique. Taking the example of the solar wind velocity, the most reliable such measurements are obtained when phase fluctuation observations of scattered radio waves, which are not susceptible to saturation effects, are recorded at two or more widely-spaced ground stations. Two extensive observation campaigns of this type were carried out with the Venus-orbiting satellites Venera 10 in 1976 and Venera 15/16 in 1984. The observations were performed over the course of three months near superior conjunction at solar offset distances R approximately 6-80 R(solar mass). The main results from the subsequent analysis of these data are: (1) velocities vary between 250 and 380 km s(exp -1) for R greater than 20 R(solar mass), agreeing with similar measurements using natural sources (IPS); (2) velocities derived from two-station phase fluctuation observations varv between 70 and 120 km s(exp -1) for R less than 12 R(solar mass), i.e. values substantially lower than those derived from conventional IPS data; and (3) it is suggested that the different velocity profiles derived from the two data sets at small R may be due to the effects of magnetosonic and Alfvenic waves on radio wave scattering. Further analysis of additional radio sounding data should help resolve the apparent discrepancy.

Efimov, A. I.

1995-01-01

279

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

SciTech Connect

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 over a range of heliocentric radial distance from approx.6 to 44 R/sub sun/ with solar latitudes ranging from -17/sup 0/ to +7/sup 0/. Observations with Mariner 10 during a period of moderate solar activity in 1974 cover from 6 to 24 R/sub sun/ and from approx.20/sup 0/ to near 90/sup 0/. We have found that the temporal frequency variance spectrum of amplitude fluctuations is useful for characterizing the bulk motion of the plasma. This spectrum has an approximately constant low frequency plateau and a power-law high frequency asymptote; the plateau-asymptote intersection frequency provides a measure of the solar wind velocity V. We also obtain the spectral index p of electron density turbulence, Phi/sub N/approx.kappa/sup -p/, where kappa is spatial wavenumber. These results apply to a cylindrical region oriented with its axis along the radio ray path and its center at the point of closest approach to the Sun. The measurements of V and p cover some 78/sup d/ for Viking and 49/sup 2/ for Mariner 10 and show the combined effects of changing heliocentric distance rho, solar latitude theta, and solar longitude Psi, as well as solar activity. The Viking results can be regarded as a function primary of rho and Psi since the observations are concentrated in the equatorial regions when solar activity was near minimum. For Mariner 10, rho, theta, and Psi variations were important. The Viking results show an abrupt change in V(rho) and the turbulence spectral index at approx.15 R/sub sun/.

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

1981-10-01

280

Ionizations scintillation detectors  

NASA Astrophysics Data System (ADS)

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

Policarpo, A. J. P. L.

281

Conditioning Matrices of Liquid Scintillation Cocktails Contaminated with Tritium  

SciTech Connect

This paper describes a viable solidification technology to convert the liquid scintillation cocktail into a stable form which minimizes the probability to release tritium in the environment.This radioactive waste type is generated by the radio-chemical analysis lab of a CANDU nuclear power plant.

Dianu, Magdalena [Institute for Nuclear Research (Romania)

2005-07-15

282

Scintillation study at Varanasi  

NASA Astrophysics Data System (ADS)

A scintillation study carried out at Varanasi (geomag. lat., 14 deg 55 min N) using geostationary satellite FLEETSAT signals at 244.168 MHz is reported. A conventional recording system has been used. The time of peak occurrence is found to vary from month to month and is predominant in the premidnight period. The seasonal dependence of nighttime scintillation variation shows a maximum occurrence of 20 percent for equinox at around 2100-2200 hrs IST. The effect of magnetic activity on scintillation occurrence was examined and it is found that there was no scintillation at all in summer on quiet days in the premidnight period. The computed scintillation index also exhibits nighttime variation. These features are compared with available results at low and midlatitude stations.

Singh, R. P.; Singh, U. P.; Singh, A. K.; Singh, R. N.

1993-02-01

283

Analysis of the Variability and the Spectrum of Periods of Extragalactic Source OJ 287 in The Radio WAVES  

NASA Astrophysics Data System (ADS)

We analyzed long-term monitoring of data flux of extragalactic source OJ 287 obtained at frequencies of 14.5 GHz (1974-2011), 8 GHz (1971-2011), 4.8GHz and (1979-2010), on the RT-26, University of Michigan, USA. Variability of the flux of the radio source was investigated by applying wavelet analysis. There were identified long-period (in the range of 3.6 to 13.6 years) and short (in the range from 1.2 to 1.8 years) components at all studied frequencies and it was determined the time of their existence. The "spectra periods" for each year of observation were built to assess the contribution of individual periods in the formation of the most powerful phase of activity of the radio source. The dynamics of the manifestations of active periods at different frequencies was observed. The obtained data was compared with the results of MOJAVE VLBI monitoring for the period of 1995-2012 years at a frequency of 15.4 GHz. It allowed to investigate the structure of emissions during periods of manifestation activity maxima.

Donskykh, A.; Ryabov, M.; Suharev, A.; Aller, M.

284

Extended ionospheric amplitude scintillation model for GPS receivers  

NASA Astrophysics Data System (ADS)

scintillation is a phenomenon that occurs after sunset, especially in the low-latitude region, affecting radio signals that propagate through the ionosphere. Depending on geophysical conditions, ionospheric scintillation may cause availability and precision problems to Global Navigation Satellite System users. The present work is concerned with the development of an extended model for describing the effects of the amplitude ionospheric scintillation on GPS receivers. Using the ?-? probabilistic model, introduced by previous authors in different contexts, the variance of GPS receiver tracking loop error may be estimated more realistically. The proposed model is developed with basis on the ?-? parameters and also considering correlation between amplitude and phase scintillation. Its results are interpreted to explain how a receiver may experience different error values under the influence of ionospheric conditions leading to a fixed scintillation level S4. The model is applied to a large experimental data set obtained at São José dos Campos, Brazil, near the peak of the equatorial anomaly during high solar flux conditions, between December 2001 and January 2002. The results from the proposed model show that depending on the ?-? pair, moderate scintillation (0.5 ? S4 ? 0.7) may be an issue for the receiver performance. When S4 > 0.7, the results indicate that the effects of scintillation are serious, leading to a reduction in the receiver availability for providing positioning solutions in approximately 50% of the cases.

Oliveira Moraes, Alison; Costa, Emanoel; Paula, Eurico Rodrigues; Perrella, Waldecir João.; Monico, João. Francisco Galera

2014-05-01

285

A full-duplex radio-over-fiber link with 12-tupling mm-wave generation and wavelength reuse for upstream signal  

NASA Astrophysics Data System (ADS)

A full-duplex radio-over-fiber (RoF) link with a novel scheme to generate 60 GHz mm-waves from a 5 GHz RF signal source is investigated. In the RoF downlink, the required frequency of the RF oscillator is reduced greatly. Since the optical carrier is not modulated by downstream data, part of it is reused to carry upstream data and the upstream data is transmitted to the central station using optical single-sideband modulation. In this way, a single wavelength is used for both downstream and upstream transmissions. Based on this scheme, a full-duplex RoF link is built and its transmission performance is analyzed. Theoretical analysis and numerical simulation show that the downstream signal cannot only eliminate code form distortion caused by time shift of the code edges, but also reduce the influence of the fading effect as the 60 GHz DSB optical mm-wave signal is transmitted along the fiber, and the upstream signal is immune to both fading effect and time shift of the code edges.

Chen, Yang; Wen, Aijun; Shang, Lei; Wang, Yong

2011-10-01

286

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

Microsoft Academic Search

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

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

1995-01-01

287

Program for the Calculation of Radio-Wave Transmission Loss over the Spherical Earth and over Obstacles.  

National Technical Information Service (NTIS)

A new computer program was created to evaluate the radioelectric wave propagation loss around the earth in the frequency range of 30 to 40 MHz up to 10 to 12 GHz. The name of the program is CARDIF. Details of the program are given.

M. Ranger J. Regnier M. Andreu Y. Lepape

1987-01-01

288

A study on the scattering of radio waves from buried spherical targets using the step frequency radar  

Microsoft Academic Search

The step frequency radar has been implemented and scattering experiments conducted on buried spherical targets to gather insight on the radar's limitations and target classification. Theoretical results are obtained using a combination of ray optics and a full wave solution for target scattering. These theoretical results are compared with experimental results to show the effect of target size on the

A. P. Freundorfer; K. Iizuka

1993-01-01

289

The wavelet transform function to analyze interplanetary scintillation observations  

NASA Astrophysics Data System (ADS)

Interplanetary scintillation (IPS) observations are useful to remotely sense the inner heliosphere. We present a new technique to analyze IPS observations using a wavelet transform (WT) function. This technique allows us to derive, in a straightforward way, a simple method to obtain the scintillation index (m). We tested this WT technique to analyze IPS observations obtained by the Solar-Terrestrial Environment Laboratory (STEL) radio telescope. The analysis of the m index of the radio source 3C48 detected by STEL over the year 2012 shows the expected decrease with solar elongation reported in previous studies. The WT technique has a great potential for future solar wind studies using IPS observations from contemporary radio telescopes.

Aguilar-Rodriguez, E.; Rodriguez-Martinez, M.; Romero-Hernandez, E.; Mejia-Ambriz, J. C.; Gonzalez-Esparza, J. A.; Tokumaru, M.

2014-05-01

290

Waves  

NSDL National Science Digital Library

The following websites are useful tools in understanding how energy is transferred from place to place through waves. Start by downloading the assignment and then begin with website number 1 and continue until you have visited all three websites. Begin by downloading the IA Waves Internet Assignment: IA Waves Internet Assignment You will answer the questions in Microsoft Word and then e-mail the assignment to me. Website #1: Read about basic information on waves and answer the questions from part 1 of the IA Waves Guide: Basic Wave Information Website #2: Follow the instructions for the following ...

Hansen, Mr.

2010-11-12

291

Computation of amplitude and phase of VLF radio waves: Results from comparative study between wave-hop and waveguide mode theory  

Microsoft Academic Search

We present a comparative study of the wave-hop theory and waveguide mode theory (namely, Long Wavelength Propagation Capability (LWPC)) for computing the amplitude and phase of VLF signals in the context of Indian sub-continent. We use the Indian Navy VTX station transmitting at 18.2 kHz as an example of the source and compute the propagation characteristics. We find the signal

Sujay Pal; Sandip K. Chakrabarti

2011-01-01

292

IPS studies using the Mexican Array Radio Telescope (MEXART)  

NASA Astrophysics Data System (ADS)

The MEXART is an array devoted to observations of radio sources to study solar wind densities and velocities employing the Interplanetary Scintillation (IPS) technique. We report the current configuration of the array and an updated catalogue of IPS radio sources. We report the power spectral analysis procedure of the intensity fluctuations. We apply the power spectrum fitting model to infer solar wind velocities.

Romero Hernandez, E.; Mejía, J.; Gonzalez-Esparza, A.; Aguilar-Rodriguez, E.; Villanueva, P.; Andrade, E.; Carrillo, A.; Mexart

2011-12-01

293

Ultimate performance of optical DSB signal-based millimeter-wave fiber-radio system: effect of laser phase noise  

Microsoft Academic Search

It is theoretically shown that the phase noise of laser light source can be automatically eliminated by compensating the differential group delay due to the fiber dispersion between the two sidebands of the optical DSB signal. The bit error rate (BER) measurement of 60 GHz millimeter (mm)-wave subcarrier multiplexed optical double-sideband (DSB) signal transport in dispersion-compensated optical fiber link using

Ken-Ichi Kitayama

1999-01-01

294

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

Microsoft Academic Search

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.

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

2005-01-01

295

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

Microsoft Academic Search

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

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

2005-01-01

296

Non-Thermal Radio and Gamma-Ray Emissions from a Supernova Remnant by Blast Wave Breaking Out of the Circumstellar Matter  

NASA Astrophysics Data System (ADS)

We calculated synchrotron radio emission and ?-ray emission due to bremsstrahlung, inverse-Compton scattering, and ?0-decay from the remnant of supernova that exploded in the circumstellar matter (CSM) formed by the progenitor's stellar wind. This sort of situation is a possible origin of mixed-morphology supernova remnants (SNRs), like W 49B, which exhibit recombination-radiation spectra in X-ray emission. We assumed that the CSM of 1.5 M? exists at 0.07-3 pc away from the supernova in the interstellar medium (ISM) of density 0.016 cm-3. When the blast wave breaks out of the CSM into the ISM, its velocity rapidly increases, and hence particle acceleration is enhanced. The maximum energy of protons reaches ˜1300 TeV just after the break-out with ˜0.5% of the explosion energy. We considered the non-thermal emission from the blast-shocked ISM shell after the break-out. Synchrotron radio flux at 1 GHz is tens of Jy, comparable to that observed from mixed-morphology SNRs. Because of low density, the ?-ray luminosity is dominated by inverse-Compton scattering, which is higher than the ?0-decay luminosity by an order of magnitude. The total ?-ray luminosity, including bremsstrahlung, is on the order of 1033 erg s-1 lower than the typical value of 1035-1036 erg s-1 observed from mixed-morphology SNRs. However, if, e.g., ˜10% of accelerated protons interact with some matter of density of 100 cm-3, the ?0-decay ?-ray luminosity would be enhanced to be comparable with the observed value.

Shimizu, Takafumi; Masai, Kuniaki; Koyama, Katsuji

2013-06-01

297

Scintillating fiber tracking techniques  

SciTech Connect

The current status of the field of scintillating fiber detection and tracking is briefly reviewed, and avenues for further work are suggested. Attention is given to the core material, cladding material, and extra-mural absorber to be used in the scintillating fibers, as well as to the properties of attenuation length, radiation resistance, and fiber profile. Some examples are given of successful recording of tracks and interactions. Current developments are mentioned in relation to plastic and glass fibers and liquid capillaries. (LEW)

Ruchti, R.

1986-02-01

298

Condensed xenon scintillators  

Microsoft Academic Search

Liquid and solid xenon were investigated as scintillator media for the detection of charged particles. The LET dependence of the integral light output was studied over a wide range of ionization densities using alpha and beta particles and heavy ions of 1.4 MeV\\/amu. For solid xenon, scintillation decay times were measured by the delayed single-photon method. For liquid xenon, a

W. Baum; S. Gotz; H. Heckwolf; P. Heeg; M. Mutterer; J. P. Theobald

1988-01-01

299

Condensed krypton scintillators  

Microsoft Academic Search

Liquid and solid krypton have been studied as scintillators. Attenuation length for Kr scintillation light was determined to be about 1m, after the Kr was purified by a hot Ca-getter and by a Ti discharge purifier in liquid phase. Two detectors (75 and 51 in size, respectively) were tested as stop-counters in a time-of-flight experiment using 1-2 GeV\\/c particle beams

D. Yu. Akimov; A. I. Bolozdynya; D. L. Churakov; A. V. Koutchenkov; V. F. Kuzichev; V. N. Lebendenko; I. A. Rogovsky; M. Chen; V. Yu. Chepel; V. V. Sushkov

1993-01-01

300

Simulating intergalactic quasar scintillation  

NASA Astrophysics Data System (ADS)

Intergalactic scintillation of distant quasars is sensitive to free electrons and therefore complements Ly? absorption-line experiments probing the neutral intergalactic medium (IGM). We present a new scheme to compute IGM refractive scintillation effects on distant sources in combination with adaptive mesh refinement cosmological simulations. First, we validate our model by reproducing the well-known interstellar scintillation (ISS) of Galactic sources. The simulated cosmic density field is then used to infer the statistical properties of intergalactic scintillation. Contrary to previous claims, we find that the scattering measure of the simulated IGM at z < 2 is = 3.879, i.e. almost 40 times larger than that for the usually assumed smooth IGM. This yields an average modulation index ranging from 0.01 (?s = 5 GHz) up to 0.2 (?s = 50 GHz); above ?s ? 30 GHz the IGM contribution dominates over ISS modulation. We compare our model with data from a 0.3 ? z ? 2 quasar sample observed at ?obs = 8.4 GHz. For this high-frequency (10.92 ? ?s ? 25.2), high-galactic-latitude sample ISS is negligible, and IGM scintillation can reproduce the observed modulation with a 4 per cent accuracy, without invoking intrinsic source variability. We conclude by discussing the possibility of using IGM scintillation as a tool to pinpoint the presence of intervening high-z groups/clusters along the line of sight, thus making it a probe suitably complementing Sunyaev-Zel'dovich data recently obtained by Planck.

Pallottini, A.; Ferrara, A.; Evoli, C.

2013-10-01

301

Observations of IPS radio sources at 140 MHz with the Mexican Array Radio Telescope (MEXART)  

NASA Astrophysics Data System (ADS)

The MEXART is a dedicated transit station to perform Interplanetary Scintillation (IPS) ob-servations. The array of 4096 full wavelenght dipoles has a collecting area of 9600 square meters, the operation frequency is 140 MHz with a bandwidth of 2 MHz. Recently we began the IPS observations with the instrument. We report a list of IPS radio sources observed at 140 MHz. We perform an analysis of the scintillation index (m) versus the elongation angle to obtain the first g values given by the instrument for some radio sources. We report the single station solar wind velocity fitting model adapted at 140 MHz based on Manoharan and Ananthakrishnan (1990).

Mejia-Ambriz, Julio-Cesar; Villanueva-Hernandez, Pablo; Gonzalez-Esparza, Americo; Aguilar-Rodriguez, Ernesto; Mendoza-Torrez, Jose Eduardo; Carrillo-Vargas, Armando; Andrade-Mascote, Ernesto

302

Characteristics of quasi-periodic scintillations observed at low latitude  

NASA Astrophysics Data System (ADS)

Quasi-periodic scintillations are characterized as primary deep fadeout in field strength, associated with regular ringing patterns before and after it. In this paper, observations of quasi-periodic scintillations using geostationary satellite (FLEETSAT) transmissions operating at frequency 250 MHz at low-latitude ground station, Varanasi (geomagnetic latitude 14°55'N, longitude 153°59'E), are reported. The results indicate that the quasi-periodic scintillations are most likely produced by plasma blobs/bubbles present in the E and F regions of the ionosphere which are helpful in identifying the generation mechanism of the associated irregularities. The various characteristic features of the different types of quasi-periodic scintillations observed at low latitude are discussed for the first time in detail based on a highly comprehensive analysis of longer data sets using autocorrelation, power spectrum, and scintillation index analysis. The computed horizontal scale size of the quasi-periodic scintillations producing irregularity varies from 100 to 1300 m which shows that the irregularities are of intermediate-scale sizes. The spectral index obtained from the slopes of power spectrum varies from -2 to -8. All of these observed results are important for identifying the generation mechanism of ionospheric irregularities associated with quasi-periodic scintillations. The observed fading patterns, especially the modulation of the diffraction patterns (fading envelopes), can be explained by considering an obstacle called radio lens in the ionosphere elongated in one direction. For the first time, we have successfully simulated the amplitude versus time plots of almost all types of quasi-periodic scintillation patches and found that our modeled and observed characteristics of quasi-periodic scintillation patches compare well with each other.

Patel, Kalpana; Singh, Ashutosh K.; Singh, A. K.; Singh, R. P.

2009-12-01

303

Calculations of equatorial scintillations at VHF and gigahertz frequencies based on a new model of the disturbed equatorial ionosphere  

Microsoft Academic Search

The weak scattering, thin screen theory of scintillation of radio stars and satellites has been applied, in a mathematically rigorous way, to the observations of the plasma density structure deduced from rocket and radar measurements during equatorial spread F conditions. It is shown that bottomside spread F is capable of producing moderate scintillation at VHF, but not at gigahertz frequencies.

Emanoel Costa; M. C. Kelly

1976-01-01

304

Ooty Interplanetary Scintillation – Remote-Sensing Observations and Analysis of Coronal Mass Ejections in the Heliosphere  

Microsoft Academic Search

In this paper, I investigate the three-dimensional evolution of solar wind density and speed distributions associated with\\u000a coronal mass ejections (CMEs). The primary solar wind data used in this study has been obtained from the interplanetary scintillation\\u000a (IPS) measurements made at the Ooty Radio Telescope, which is capable of measuring scintillation of a large number of radio\\u000a sources per day

P. K. Manoharan

2010-01-01

305

Scintillation light emission studies of LSO scintillators  

SciTech Connect

UV and {gamma}-ray excited luminescence and nuclear spectroscopy were used to study the relationship between the scintillation mechanisms of LSO and the spectroscopic characteristics obtained with PMT and APD readouts at room temperature. No correlation was found between scintillation decay time and light output. Like other investigators, the authors observed the existence of two distinct luminescence centers, Ce1 and Ce2, that mainly give rise to short (420 nm) and long (440 nm) emission wavelengths. The measurements showed that different LSO crystals excited by {gamma}-rays have emission spectra with largely different shapes and maxima depending on the relative population and luminescence efficiency of these centers. It was also found that the poor energy resolution of LSO and YSO scintillators is well correlated with the coexistence of the two competing luminescence mechanisms. The prevalence of either Ce1 or Ce2 luminescence tends to reduce the variance of light emission and, thus, to improve energy resolution. Inversely, the coexistence of the two centers increases variance and degrades energy resolution.

Saoudi, A.; Pepin, C.; Houde, D.; Lecomte, R.

1999-12-01

306

The Sardinia Radio Telescope  

NASA Astrophysics Data System (ADS)

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

D'Amico, Nichi

2011-08-01

307

Cassini Radio Science  

Microsoft Academic Search

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

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

2004-01-01

308

Cassini Radio Science  

Microsoft Academic Search

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

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

309

Interplanetary plasma scintillation parameters measurements retrieved from the spacecraft observations.  

NASA Astrophysics Data System (ADS)

Measurement of the Interplanetary Scintillations (IPS) of radio signals propagating through the plasma in the Solar System by the radio astronomical instruments is a powerful tool to characterise and study the spatial and temporal variation of the electron density in the Solar wind. Several techniques based on the observation of natural and artificial radio sources have been developed during the last 50 years. Here we report our results of the IPS parameters measurement based on the multi-station observations of the planetary mission spacecraft. The ESA Venus Express spacecraft was observed at X-band (8.4 GHz) by several European VLBI stations - Metsähovi Radio Observatory (Aalto University , FI), Medicina (INAF-RA, IT), Matera (ASI, IT), Wettzell (BKG, DE), Noto (INAF-IRA, IT) and Yebes (OAN-IGN, ES) during a 2008-2010 campaign in a framework of the PRIDE (Planetary Radio Interferometry and Doppler Experiments) project as a preparatory stage for the European Radio Astronomy VLBI facilities participation in the planned ESA planetary missions (EJSM, TESM, EVE and others). Observational data were processed at Metsähovi Radio Observatory with the on-purpose developed high performance, ultra-high spectral resolution and spacecraft tracking capable software spectrometer-correlator and analysed at the Joint Institute for VLBI in Europe (JIVE, NL). High quality of acquired and analysed data enables us to study and define several parameters of the S/C signal and accompanying "ranging" tones with milli-Hz accuracy, among which the phase fluctuations of the spacecraft signal carrier line can be used to characterise the interplanetary plasma density fluctuations along the signal propagation line at different spatial and temporal scales at different Solar elongations and which exhibits a near-Kolmogorov spectrum. Such essential parameters as the phase scintillation index and bandwidth of scintillations and their dependence on the solar elongation, distance to the target, positions of the source in the Solar system and Solar activity index were retrieved from our measurements and are reported. This study is focused on the technique of the measurements and data analysis, leaving the physical interpretation of the measurement results to the upcoming studies when more observational data is collected. Our measurements of the phase scintillations from the sources within the Solar system are complementary to the classical measurements of the power level scintillations of signals from the natural radio sources. The results presented in this paper are promising and observations will continue during 2010.

Molera Calvés, Guifré; Pogrebenko, S. V.; Wagner, J.; Maccaferri, G.; Colucci, G.; Kronschnabl, G.; Scilliro, F.; Bianco, G.; Pérez Ayúcar, M.; Cosmovici, C. B.

2010-05-01

310

Coherence properties of wideband satellite signals caused by ionospheric scintillation  

NASA Technical Reports Server (NTRS)

Radio scintillation on satellite signals caused by small-scale irregularities in F-region ionospheric electron density can be an important limitation on earth-satellite communication and navigation systems. Scintillation imposes distortion in both amplitude and phase on wideband signals. In the present work, the shallow-modulated phase screen theory is developed in terms of coherence bandwidth including a model based on a turbulent-like power-law description of the irregularities. The model results usually show a greater coherence bandwidth in the signal phase than in the signal amplitude. Therefore, systems that require phase coherence over a large bandwidth should be less affected than those requiring amplitude coherence.

Rufenach, C. L.

1975-01-01

311

Remote sensing of the earth/sea-ionosphere waveguide using ground based ELF-VLF radio wave observations  

NASA Astrophysics Data System (ADS)

The results from lightning and man made transmitter generated ELF-VLF signals recorded under the Word Wide Lightning Location (WWLL) Network at low latitude ground wave station, Suva (18.2°S, 178.3°E), Fiji, in the South Pacific region, are used to study the features of the earth/sea-ionosphere waveguide. A ground wave VLF system was established in Aug. 2003 under WWLL, since then ELF and VLF data are recorded in the regular intervals. Matlab codes are used to analyse the data files recorded using lightning software and each of data file is of 11 MB with one minute duration. The analysis of data shows the occurrence of tweeks signals mainly in the night-time. Unusual higher harmonic tweek signals up to fifth harmonic are recorded particularly in the post-midnight period. Tweek signals have been used to determine the height of ionospheric reflecting layer, total propagation distance in the atmospheric waveguide and attenuation rate for tweeks with different modes. The value of ionospheric reflecting height (H) calculated using waveguide mode theory of electromagnetic wave propagation in the spherical cell waveguide having perfectly conducting boundaries is found to vary from 80-95 km in the night-time. The electron density (N) at the ionpspheric reflecting heights is found to vary from 80 to 1.3x10^3 cm-3 which agrees quite well with experimental data. Total distance propagated by the weeks in the atmospheric waveguide before reaching to the receiver is found to be of the order of few thousand km. The propagation time vs frequency characteristics of ELF and VLF signals explain the dispersion of tweeks. The calculated attenuation rate of tweeks shows less attenuation for lower modes as compared to higher modes. The attenuation increases sharply as the frequencies approach the cut-off frequency and conductivity increases, and it also increases when the reflecting layer height falls, for all the modes. The attenuation is less in the night-time than that in the day-time. The waveguide between the sea surface and the lower layer of the ionosphere offers less attenuation than that between the earth surface and the lower layer of the ionosphere, and explains the occurrence of higher mode tweeks at this station. Preliminary results of measurement of amplitude of 19.8 kHz VLF signals from transmitter NWC (21°48'S, 114°9'E) on the North West Cape of Australia, propagated in the earth/sea-ionosphere waveguide, are also presented. From the measured values of diurnal amplitude changes, the daytime ionospheric parameters are estimated.

Kumar, S.; Ramachandran, V.; Kishore, A.

312

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

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

313

A multidisciplinary study of planetary, solar and astrophysical radio emissions  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

314

Firefighters' Radios  

NASA Technical Reports Server (NTRS)

Public Technology Inc. asked for NASA assistance to devise the original firefighter's radio. Good short-range radio communications are essential during a fire to coordinate hose lines, rescue victims, and otherwise increase efficiency. Useful firefighting tool is lower cost, more rugged short range two-way radio. Inductorless electronic circuit replaced inductances and coils in radio circuits with combination of transistors and other low-cost components. Substitution promises reduced circuit size and cost. Enhanced electrical performance made radio more durable and improved maintainability by incorporating modular construction.

1976-01-01

315

Development of radiation hard scintillators.  

National Technical Information Service (NTIS)

The authors have demonstrated that the radiation stability of scintillators made from styrene polymer is very much improved by compounding with pentaphenyltrimethyltrisiloxane (DC 705 vacuum pump oil). The resulting scintillators are softer than desired, ...

F. Markley M. Davidson J. Keller G. Foster A. Pla-Dalmau

1993-01-01

316

Scintillator plate calorimetry  

SciTech Connect

Calorimetry using scintillator plates or tiles alternated with sheets of (usually heavy) passive absorber has been proven over multiple generations of collider detectors. Recent detectors including UA1, CDF, and ZEUS have shown good results from such calorimeters. The advantages offered by scintillator calorimetry for the SSC environment, in particular, are speed (<10 nsec), excellent energy resolution, low noise, and ease of achieving compensation and hence linearity. On the negative side of the ledger can be placed the historical sensitivity of plastic scintillators to radiation damage, the possibility of nonuniform response because of light attenuation, and the presence of cracks for light collection via wavelength shifting plastic (traditionally in sheet form). This approach to calorimetry is being investigated for SSC use by a collaboration of Ames Laboratory/Iowa State University, Argonne National Laboratory, Bicron Corporation, Florida State University, Louisiana State University, University of Mississippi, Oak Ridge National Laboratory, Virginia Polytechnic Institute and State University, Westinghouse Electric Corporation, and University of Wisconsin.

Price, L.E.

1990-01-01

317

Liquid Scintillator Purification  

SciTech Connect

The KamLAND collaboration has studied background requirements and purification methods needed to observe the 7Be neutrino from the sun. First we will discuss the present background situation in KamLAND where it is found that the main background components are 210Pb and 85Kr. It is then described how to purify the liquid scintillator. The present status and results on how to remove 210Pb from the liquid scintillator are discussed. Specifically, the detailed analysis of the effects of distillation and adsorption techniques are presented.

Kishimoto, Y. [Research Center for Neutrino Science, Tohoku University (Japan)

2005-09-08

318

Extruding plastic scintillator at Fermilab  

Microsoft Academic Search

An understanding of the costs involved in the production of plastic scintillators and the development of a less expensive material have become necessary with the prospects of building very large plastic scintillation detectors. Several factors contribute to the high cost of plastic scintillating sheets, but the principal reason is the labor-intensive nature of the manufacturing process. In order to significantly

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

2003-01-01

319

Radiation damage in scintillating crystals  

Microsoft Academic Search

Crystal Calorimetry in future high-energy physics experiments faces a new challenge to maintain its precision in a hostile radiation environment. This paper discusses the effects of radiation damage in scintillating crystals, and concludes that the predominant radiation damage effect in crystal scintillators is the radiation-induced absorption, or color center formation, not the loss of scintillation light yield. The importance of

Ren-yuan Zhu

1998-01-01

320

Problems in the use of plastic scintillators in intense radiation fields  

SciTech Connect

Annual doses in the SDC End Cap Calorimeter, and possible design decisions in the use of radiation resistant scintillators are discussed. Some candidates for base radiation tolerant scintillators and wave length shifters are discussed. Absorption and emission spectra of one of them are represented.

Cherny, S.

1992-07-01

321

The AT20G view of Swift/BAT selected AGN: high-frequency radio waves meet hard X-rays  

NASA Astrophysics Data System (ADS)

We cross-matched the 6-year Swift/Burst Alert Telescope (BAT) survey of active galactic nuclei (AGN) with the AT20G radio survey of the southern sky, which is one of the largest high-frequency radio surveys available. With these data we investigated the possible correlation between the radio and the X-ray emission at the highest radio and X-ray frequencies. We found 37 AGN with a high probability of association (>80 per cent), among which 19 are local Seyfert galaxies (with median redshift z = 0.03) and 18 blazars. We found that ?20 per cent of the AGN detected in hard X-rays are also bright radio sources at 20 GHz, but the apparent correlation between the radio and hard X-ray luminosity is completely driven by the different median redshifts of the two subgroups of AGN. When we consider only the local Seyfert sample we find no evidence of a correlation between their 20 GHz and 15-55 keV power. Therefore it appears that at high frequencies the radio-X connection, which had been previously observed at lower frequencies, disappears. The disappearance of the radio-X correlation at high radio and X-ray frequencies could be tested through Very Long Baseline Interferometry and the use of the Nuclear Spectroscopic Telescope Array (NuSTAR) satellite.

Burlon, D.; Ghirlanda, G.; Murphy, T.; Chhetri, R.; Sadler, E.; Ajello, M.

2013-05-01

322

Simple instruments in radio astronomy  

NASA Astrophysics Data System (ADS)

Radio astronomy has a major role in the study of the universe. The spiral structure of our Galaxy and the cosmic background radiation were first detected, and the dense component of interstellar gas is studied, at radio wavelengths. COBE revealed very weak temperature fluctuations in the microwave background, considered to be the seeds of galaxies and clusters of galaxies. Most electromagnetic radiation from outer space is absorbed or reflected by the Earth's atmosphere, except in two narrow spectral windows: the visible-near-infrared and the radio, which are nearly transparent. Centimetre and longer radio waves propagate almost freely in space; observations of them are practically independent of weather. Turbulence in our atmosphere does not distort the wavefront, which simplifies the building of radio telescopes, because no devices are needed to correct for it. Observations at these wavelengths can be made in high atmospheric humidity, or where the sky is not clear enough for optical telescopes. Simple instruments operating at radio wavelengths can be built at low cost in tropical countries, to teach students and to familiarize them with radio astronomy. We describe a two-antennae radio interferometer and a single-dish radio telescope operating at centimetre wavelengths. The Sun and strong synchrotron radio-sources, like Cassiopeia A and Cygnus A, are potential targets.

Nguyen-Quang-Rieu

323

The Radio Plasma Imager investigation on the IMAGE spacecraft  

Microsoft Academic Search

Radio plasma imaging uses total reflection of electromagnetic waves from plasmas whose plasma frequencies equal the radio sounding frequency and whose electron density gradients are parallel to the wave normals. The Radio Plasma Imager (RPI) has two orthogonal 500-m long dipole antennas in the spin plane for near omni-directional transmission. The third antenna is a 20-m dipole along the spin

B. W. Reinisch; D. M. Haines; K. Bibl; G. Cheney; I. A. Galkin; X. Huang; S. H. Myers; G. S. Sales; R. F. Benson; S. F. Fung; J. L. Green; S. Boardsen; W. W. L. Taylor; J.-L. Bougeret; R. Manning; N. Meyer-Vernet; M. Moncuquet; D. L. Carpenter; D. L. Gallagher; P. Reiff

2000-01-01

324

Intrinsic Scintillator Resolution  

Microsoft Academic Search

Measurements of spectrometer resolution using an electron gun and phosphor type of light source yield values considerably better than those obtained from scintillations in a phosphor. Line widths of about 3.4 per cent have been obtained at a pulse height equivalent to 661 kev in NaI. An investigation is being made to determine the causes of this difference. A number

G. G. Kelley; P. R. Bell; R. C. Davis; N. H. Lazar

1956-01-01

325

Polysiloxane scintillator composition  

DOEpatents

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

Walker, J.K.

1992-05-05

326

Study of Equatorial Scintillations.  

National Technical Information Service (NTIS)

Observations of the amplitude scintillations produced by the F-region in equatorial areas are presented. The equipment used for conducting the observations is described. The use of transmissions from the ATS-1, ATS-3, and ATS-5 for obtaining data is descr...

J. Pomalaza R. Woodman G. Tisnado E. Nakasone

1972-01-01

327

Polysiloxane scintillator composition  

DOEpatents

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

Walker, James K. (Gainesville, FL)

1992-01-01

328

Boron loaded scintillator  

DOEpatents

A scintillating composition for detecting neutrons and other radiation comprises a phenyl containing silicone rubber with carborane units and at least one phosphor molecule. The carbonate units can either be a carborane molecule dispersed in the rubber with the aid of a compatibilization agent or can be covalently bound to the silicone.

Bell, Zane William (Oak Ridge, TN) [Oak Ridge, TN; Brown, Gilbert Morris (Knoxville, TN) [Knoxville, TN; Maya, Leon (Knoxville, TN) [Knoxville, TN; Sloop, Jr., Frederick Victor (Oak Ridge, TN); Sloop, Jr., Frederick Victor [Oak Ridge, TN

2009-10-20

329

Scintillator Waveguide For Sensing Radiation  

DOEpatents

The present invention is an apparatus for detecting ionizing radiation, having: a waveguide having a first end and a second end, the waveguide formed of a scintillator material wherein the therapeutic ionizing radiation isotropically generates scintillation light signals within the waveguide. This apparatus provides a measure of radiation dose. The apparatus may be modified to permit making a measure of location of radiation dose. Specifically, the scintillation material is segmented into a plurality of segments; and a connecting cable for each of the plurality of segments is used for conducting scintillation signals to a scintillation detector.

Bliss, Mary (West Richland, WA); Craig, Richard A. (West Richland, WA); Reeder; Paul L. (Richland, WA)

2003-04-22

330

Scintillator requirements for medical imaging  

SciTech Connect

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

Moses, William W.

1999-09-01

331

Study of transionospheric signal scintillation: Quasi- particle approach  

NASA Astrophysics Data System (ADS)

A quasi-particle approach is applied to study amplitude scintillation of transionospheric signals caused by Bottomside Sinusoidal (BSS) irregularities. The quasi- particle method exploits wave-particle duality, viewing the wave as a distribution of quasi-particles. This is accomplished by transforming the autocorrelation of the wave function into a Wigner distribution function, which serves as a distribution of quasi-particles in the (/vec r,/ /vec k) phase space. The quasi-particle distribution at any instant of time represents the instantaneous state of the wave. Scattering of the signal by the ionospheric irregularities is equivalent to the evolution of the quasi-particle distribution, due to the collision of the quasi-particles with objects arising from the presence of the BSS irregularities. Subsequently, the perturbed quasi-particle distribution facilitates the computation of average space time propagation properties of the wave. Thus, the scintillation index S4 is determined. Incorporation of essential BSS features in the analysis is accomplished by analytically modeling the power spectrum of the BSS irregularities measured in-situ by the low orbiting Atmosphere-E (AE - E) Satellite. The effect of BSS irregularities on transionospheric signals has been studied. The numerical results agree well with multi-satellite scintillation observations made at Huancayo Peru in close time correspondence with BSS irregularities observed by the AE - E satellite over a few nights (December 8-11, 1979). During this period, the severity of the scintillation varied from moderate to intense, S4 = 0.1-0.8.

Lyle, Ruthie D.

1998-07-01

332

Spectral characteristics of scintillations producing ionospheric irregularities in the Indian region  

NASA Astrophysics Data System (ADS)

VHF amplitude scintillations were recorded at Tirunelveli (8.7°N, 77.7°E; 0.6°N dip Latitude), Pondicherry (12°N, 79.1°E; 4.4°N dip Latitude) and Mumbai, (19°N, 73°E; 13.5°N dip Latitude) for the years 1992-1996 using the 250 MHz radio beacon from the geostationary satellite FLEETSAT (7°E). The recorded digital scintillation data for few nights are analyzed to estimate scintillation index (S4), fade rates, auto-correlation functions and power spectral densities for every 2.5 minute sample during the period of the scintillation activity. The power spectral slopes are shallower for the scintillation at the generation phase and steeper towards the decay phase, which indicates the erosion of smaller scale sizes towards the decay phase.

Banola, S.; Pathan, B. M.; Rao, D. R. K.; Chandra, H.

2005-01-01

333

Radio sociology  

NASA Astrophysics Data System (ADS)

A work was conducted, using radio telemetry, to locate a migrating, radio-tagged, sharp-shinned hawk. The hawk was monitored through the noise radiation it created. The hawk was found. During this study, it was found that the concentration of population corresponds with areas of increased noise temperature. Through this study, a bigger study was planned. The study would involved the relationship between a place's radiation signature and its other attributes, such as economic type, population, geographic concentration. The method of radio sociology would be used to track the sources of radio noise.

Swenson, George W., Jr.

1996-04-01

334

Tilt Estimation in Moderate-to-Strong Scintillation.  

PubMed

Adaptive optics systems are being applied in ever more challenging environments, for example, the projection of lasers over long horizontal paths through the atmosphere. These long atmospheric paths corrupt the signal received from the beacon and typically yield highly scintillated received wave fronts. Tilt estimation for controlling the fast steering mirror in these systems is complicated by the presence of branch points in the scintillated received wave fronts. In particular, correlation between the tilt and the projected beam's centroid error at the target has been observed in horizontal laser beam projection experiments. The presence of this correlation indicates that better tracking performance should be achievable. We compare the performance of four estimation schemes applied to tilt estimation in a horizontal laser projection system. It is demonstrated that all four schemes underestimate the tilt required to return the laser beam to a target in highly scintillated environments. A method of correcting this tilt is presented, and the expected performance improvement is quantified. PMID:18357314

Burl, J B; Roggemann, M C; Welsh, B

2001-06-20

335

On the second order statistics for GPS ionospheric scintillation modeling  

NASA Astrophysics Data System (ADS)

ionospheric scintillation is a phenomenon that occurs frequently, typically during nighttime, affecting radio signals that propagate through the ionosphere. Depending on the temporal and spatial distribution, ionospheric scintillation can represent a problem in the availability and precision for the Global Navigation Satellite System's users. This work is concerned with the statistical evaluation of the amplitude ionospheric scintillation fading events, namely, level crossing rate (LCR) and average fading duration (AFD). Using ?-? model, the LCR and AFD are validated against experimental data obtained in São José dos Campos (23.1°S; 45.8°W; dip latitude 17.3°S), Brazil, a station located near the southern crest of the ionospheric equatorial ionization anomaly. The amplitude scintillation data were collected between December 2001 and January 2002, a period of high solar flux conditions. The obtained results with the proposed model fitted quite well with the experimental data and performed better when compared to the widely used Nakagami-m model. Additionally, this work discusses the estimation of ? and ? parameters, and the best fading coefficients found in this analysis are related to scintillation severity. Finally, for theoretical situations in which no set of experimental data are available, this work also presents parameterized equations to describe these fading statistics properly.

Oliveira Moraes, Alison; Paula, Eurico Rodrigues; Assis Honorato Muella, Marcio Tadeu; Perrella, Waldecir João.

2014-02-01

336

College Radio.  

ERIC Educational Resources Information Center

As with commercial stations, the underlying premise of the college radio station is to serve the community, whether it be the campus community or the community at large, but in unique ways often geared to underserved niches of the population. Much of college radio's charm lies in its unpredictable nature and constant mutations. The stations give…

Sauls, Samuel J.

337

Radiation and solvent effects on wavelength shifting fibers used with liquid scintillators  

Microsoft Academic Search

The chemical compatibility of wave length shifting fibers with several liquid scintillators has been investigated. Based on systematic characterization of the behavior of the BC-517 family, a time of life of 70-450 years was estimated for the polystyrene based wave length shifting fiber in BC-517P scintillator. Wavelength shifting (WLS) fibers irradiated continuously to a dose of 6.4 Mrads (at .377

K. G. Young; M. L. Bauer; B. L. Bishop; H. O. Cohn; T. A. Gabriel; A. M. Gordeev; Y. A. Kamyshkov; R. A. Lillie; F. Plasil; K. F. Read; M. J. Rennich; A. Y. Savin; K. Shmakov; B. H. Singletary; A. V. Smirnov; E. Tarkovsky; R. A. Todd; E. Ables; P. Armatis; R. Bionta; H. Britt; O. Clamp; C. Cochran; G. Graham; M. Lowry; D. Masquelier; K. Skulina; C. Wuest; L. Bolen; L. Cremaldi; S. Harper; B. Moore; B. Quinn; J. Reidy; J. Zhou; L. Croft; R. Piercey; S. C. Berridge; W. M. Bugg; T. Handler; M. Pisharody; T. Aziz; S. Banerjee; S. R. Chendvankar; S. N. Ganfuli; P. K. Malhotra; K. Mazumdar; R. Raghavan; K. Shankar; K. Sudhakar; S. C. Tonwar; A. Arefiev; O. Baranov; Y. Efremenko; Y. Gorodkov; A. Malinin; A. Nikitin; V. Markizov; D. Onoprienko; A. Rozjkov; E. Shoumilov; V. Shoutko

1993-01-01

338

Radio Memories  

NSDL National Science Digital Library

The "Golden Age of Radio" that arguably lasted until the early 1950s may be hard to imagine today in an era of swirling iPod playlists and other genre-bending devices and technologies, but during this time the radio reigned supreme. People tuned in every week to hear the exploits of Flash Gordon, Sam Spade, and Amos n' Andy. Thanks to the Radio Memories website, many of these memories can be relived, or just experienced for the first time. Started in May 2005, the site contains a host of compelling programs, including episodes from the Interplanetary Adventures of Flash Gordon and a number of original episodes of the fabled Radio Detective Story Hour. If those types of programs fail to pique the interest of the casual visitor, the site also contains archived shows that explore the world of radio soap operas from the 1940s and the musical worlds of such stars as Tommy Dorsey and Harry James.

339

Radiation effects on wavelength shifting fibers used with liquid scintillators.  

National Technical Information Service (NTIS)

The chemical compatibility of wave length shifting fibers with several liquid scintillators has been investigated. Based on systematic characterization of the behavior of the BC-517 family, a time of life of 70 to 450 years was estimated for the polystyre...

E. Ables P. Armatis R. Bionta H. Britt O. Clamp

1992-01-01

340

Liquid capillary scintillation detectors  

SciTech Connect

The authors have been developing liquid-in-capillary detectors for tracking applications in high energy physics experiments. The detectors consist of glass capillaries of low refractive index filled with liquids of sufficiently high refractive index to produce an efficient waveguides. This paper describes recent work in which scintillating core liquids were prepared from the solvent 1-phenylnaphthalene and single solutes of selected fluorescent dyes.

Puseljic, D.; Baumbaugh, B.; Ditmire, T.; Kennedy, C.; Ruchti, R.; Ryan, J. (Notre Dame Univ., IN (USA). Dept. of Physics); Baumbaugh, A.; Knickerbocker, K. (Collimated Holes, Inc., Campbell, CA (USA)); Ellis, J.; Mead, R.; Swanson, D. (Collimated Holes, Inc., Campbell, CA (USA))

1990-04-01

341

Composite scintillator screen  

DOEpatents

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

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

1994-01-01

342

Simulating the effects of scintillation on transionospheric signals with a two-way phase screen constructed from ALTAIR phase-derived TEC  

Microsoft Academic Search

Severe scintillation on transionospheric radio signals caused by small-scale plasma irregularities can greatly disrupt wideband communication, surveillance, and navigation systems. Development of techniques to mitigate the effects of scintillation requires accurate characterization of the ionospheric propagation channel. To achieve this goal, multiple campaigns were conducted as part of the joint U.S. -UK Wideband Ionospheric Distortion Experiment to obtain ionospheric signatures

R. G. Caton; C. S. Carrano; C. M. Alcala; K. M. Groves; T. Beach; D. Sponseller

2009-01-01

343

An Analysis on the TEC Variability and Ionospheric Scintillation at Los Alamos, New Mexico Derived from FORTE-Received LAPP Signals  

Microsoft Academic Search

The total electron content (TEC) of ionosphere and its electron density irregularities (scintillation) have effects of degradation and disruption on radio signals passed between ground stations and orbiting man-made satellites. With the rapid increase in operational reliance on UHF\\/VHF satellite communication, it is desirable to obtain understandings of ionosphere TEC variability and scintillation characteristics to improve our ability of predicting

Z. Huang; R. Roussel-Dupre

2003-01-01

344

Assessment of the application of in situ ion-density data from DMSP to modeling of transionospheric scintillation. Final report, 15 September 1989-14 March 1990  

SciTech Connect

Modern military communication, navigation, and surveillance systems depend on reliable, noise-free transionospheric radio-frequency channels. They can be severely impacted by small-scale electron-density irregularities in the ionosphere, which cause both phase and amplitude scintillation. Basic tools used in planning and mitigation schemes are climatological in nature and thus may greatly over- and under-estimate the effects of scintillation in a given scenario. This report summarizes the results of a three-year investigation into the feasibility of using in-situ observations of the ionosphere from the USAF DMSP satellite to calculate estimates of irregularity parameters that could be used to update scintillation models in near real-time. Estimates for the level of intensity and phase scintillation on a transionospheric UHF radio link in the early-evening auroral zone were calculated from DMSP Scintillation Meter (SM) data and compared to the levels actually observed. The intensity scintillation levels predicted and observed compared quite well, but the comparison with the phase scintillation data was complicated by low-frequency phase noise on the UHF radio link. Results are presented from analysis of DMSP SSIES data collected near Kwajalein Island in conjunction with a propagation-effects experiment. Preliminary conclusions to the assessment study are: (1) the DMSP SM data can be used to make quantitative estimates of the level of scintillation at auroral latitudes, and (2) it may be possible to use the data as a qualitative indicator of scintillation-activity levels at equatorial latitudes.

Secan, J.A.; Reinleitner, L.A.; Bussey, R.M.

1990-03-15

345

Pulsar scintillations from corrugated reconnection sheets in the interstellar medium  

NASA Astrophysics Data System (ADS)

We show that surface waves along interstellar current sheets closely aligned with the line of sight lead to pulsar scintillation properties consistent with those observed. This mechanism naturally produces the length-scales and density scales of the interstellar medium (ISM) scattering lenses that are required to explain the magnitude and dynamical spectrum of the scintillations. In this scenario, the parts of warm ionized ISM that are responsible for the scintillations are relatively quiescent, with scintillation and scattering resulting from weak waves propagating along magnetic domain boundary current sheets. These are expected from helicity conservation and have also been observed in numerical simulations. The model statistically predicts the spacing and amplitudes of inverted parabolic arcs seen in Fourier-transformed dynamical spectra of strongly scintillating pulsars with only three parameters. Multifrequency, multi-epoch low-frequency very long baseline interferometry observations can quantitatively test this. If successful, in addition to mapping the ISM, this might allow precise nanoarcsecond pulsar astrometry, distance measurements and emission studies using these 10-au interferometers in the sky.

Pen, Ue-Li; Levin, Yuri

2014-08-01

346

Radio Wave Propagation over Salem  

NASA Astrophysics Data System (ADS)

In this paper study of rainfall has been carried out over Salem, a place in Southern India. Rainfall rate values have been recorded using a fast response rain gauge installed at Sona College of Technology. The derived rainfall rates have been used to estimate attenuation in the 10-100 GHz frequency range. Using the estimated co-polar attenuation cross polar discriminations (XPD) have been computed using ITU-R(2002) model in the 10-35 GHz range. The study shows that attenuation and cross polarization vary with frequency, elevation angle and rainfall rate. The study also depicts the cumulative distribution of rainfall rate, attenuation and XPD.

Jaiswal, R. S.; Uma, S.; Raj, M. V. A.

2007-07-01

347

Jovian type III radio bursts  

NASA Technical Reports Server (NTRS)

Radio bursts have been observed in the Voyager plasma wave data from Jupiter that bear a striking resemblance to solar type III radio bursts. The emissions lie in the frequency range near 10 kHz, have durations of a minute or so, and occur in a set of periodically spaced bursts. The spacing between primary bursts is typically 15 min, but the bursts may have additional components which recur on time scales of about 3 min. The similarity with solar type III radio bursts suggests a source mechanism involving the movement of energetic electrons through a density gradient in the plasma surrounding Jupiter. The periodicity of bursts suggests Io may be involved in the generation of waves, since the timing is similar to the Alfven wave travel time from one hemisphere to the other through the Io torus.

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

1989-01-01

348

Jovian type III radio bursts  

SciTech Connect

Radio bursts have been observed in the Voyager plasma wave data from Jupiter that bear a striking resemblance to solar type III radio bursts. The emissions lie in the frequency range near 10 kHz, have durations of a minute or so, and occur in a set of periodically spaced bursts. The spacing between primary bursts is typically 15 min, but the bursts may have additional components which recur on time scales of about 3 min. The similarity with solar type III radio bursts suggests a source mechanism involving the movement of energetic electrons through a density gradient in the plasma surrounding Jupiter. The periodicity of bursts suggests Io may be involved in the generation of waves, since the timing is similar to the Alfven wave travel time from one hemisphere to the other through the Io torus.

Kurth, W.S.; Gurnett, D.A. (Univ. of Iowa, Iowa City (USA)); Scarf, F.L. (TRW Space and Technology Group, Redondo Beach, CA (USA))

1989-06-01

349

The Polar Solar Wind from 2.5 to 40 Solar Radii: Results of Intensity Scintillation Measurements  

NASA Astrophysics Data System (ADS)

The supersonic expansion of the solar corona into interplanetary space, the solar wind, was predicted in 1958 and conclusively detected by satellite measurements in 1962. However, due to the difficulty of obtaining data close to the sun and the complexities of plasma physics, the problem of solar wind acceleration remains an enigma. Radio propagation measurements, which have been carried out for nearly the last 3 decades, are one of the few means of measuring the plasma properties in the acceleration region of the solar wind. In this thesis we present results from intensity scintillation observations (IPS), which probe the polar solar wind at solar minimum. Our closest observation, at 2.4 solar radii, is the closest ever reported. We have found that: (1) the mean velocity is already very high, even at 2.4 solar radii, perhaps even higher than further out; (2) a wide distribution of radial velocities is present in our observations (e.g. 300 km/s < Vradial < 1200km/s at 11 solar radii)-the width of this distribution decreases with increasing distance from the sun; (3) the observed Alfven wave amplitudes are consistent with WKB evolution; (4) our observations confirm the high degree of anisotropy measured with other radio propagation techniques; (5) there is non radial flow inside of 12 solar radii consistent with the predicted super radial expansion of the polar solar wind. The velocities determined by IPS are the apparent velocity of density irregularities with scales of the order of 10 to 100 km. If the density irregularities are non-propagating then IPS measures the flow velocity, otherwise IPS measures the flow speed plus the group velocity of the density waves. A new model for extracting information from intensity scintillations is presented. The model incorporates: our knowledge of the spectrum of electron density fluctuations gained from other radio propagation observations; the effects of Alfven waves; the super radial expansion of the corona near the sun; the spiral orientation of the field far from the sun; the bimodal nature of the solar wind; and the line-of-sight integration.

Klinglesmith, Michael

1997-06-01

350

Observation and modeling of quasi-periodic scintillations observed at low latitude  

NASA Astrophysics Data System (ADS)

Quasi-periodic scintillations are characterized as primary deep fade-out infield strength, associated with regular ringing patterns before and after it. In this paper, observations of quasi-periodic scintillation using geostationary satellite (FLEETSAT) transmissions operating at frequency 250 MHz at low latitude ground station, Varanasi (geomag. lat 14° 55' N, long. 154°E) are reported. The results indicate that the quasi-periodic scintillations are most likely produced by plasma blobs/bubbles present in the E and F-region of the ionosphere. The various characteristics features of the quasi periodic scintillations are discussed after the autocorrelation, power spectrum and scintillation index analysis. The computed horizontal scale size of the quasi periodic scintillation producing irregularity varies from 100 m to 1300 m which shows that the irregularities are of intermediate-scale sizes. The spectral index obtained from the slopes of power spectrum varies from -2 to -8. The observed fading patterns, especially the modulation of the diffraction pattern (fading envelope) can be explained by considering an obstacle called radio lens in the ionosphere elongated in one direction. We have simulated successfully the amplitude versus time plot of quasi periodic scintillation patches and found that our theoretical and experimental results of quasi periodic scintillation patches compares well with each other and also with the earlier published works.

Patel, Kalpana; Singh, A. K.; Singh, R. P.

2010-02-01

351

CONFERENCES AND SYMPOSIA: Seventy years of the Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Waves Propagation (IZMIRAN) (Scientific session of the Physical Sciences Division of the Russian Academy of Sciences, 25 November 2009)  

NASA Astrophysics Data System (ADS)

A scientific session of the Physical Sciences Division of the Russian Academy of Sciences dedicated to the 70th anniversary of the Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation of the Russian Academy of Sciences (IZMIRAN) (Troitsk, Moscow region) was held in the conference hall of IZMIRAN on 25 November 2009. The following reports were put on the session agenda posted on the web site www.gpad.ac.ru of the Physical Sciences Division, RAS: (1) Gurevich A V (Lebedev Physical Institute RAS, Moscow) "The role of cosmic rays and runaway electron breakdown in atmospheric lightning discharges"; (2) Aleksandrov E B (Ioffe Physical Technical Institute, RAS, St. Petersburg) "Advances in quantum magnetometry for geomagnetic research"; (3) Dorman L I (IZMIRAN, Troitsk, Moscow region, CR & SWC, Israel) "Cosmic ray variations and space weather"; (4) Mareev E A (Institute of Applied Physics, RAS, Nizhnii Novgorod) "Global electric circuit research: achievements and prospects"; (5) Tereshchenko E D, Safargaleev V V (Polar Geophysical Institute, Kola Research Center, RAS, Murmansk) "Geophysical research in Spitsbergen Archipelago: status and prospects"; (6) Gulyaev Yu V, Armand N A, Efimov A I, Matyugov S S, Pavelyev A G, Savich N A, Samoznaev L N, Smirnov V V, Yakovlev O I (Kotel'nikov Institute of Radio Engineering and Electronics RAS, Fryazino Branch, Fryazino, Moscow region) "Results of solar wind and planetary ionosphere research using radiophysical methods"; (7) Kunitsyn V E (Lomonosov Moscow State University, Moscow) "Satellite radio probing and the radio tomography of the ionosphere"; (8) Kuznetsov V D (IZMIRAN, Troitsk, Moscow region) "Space Research at the Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences." Papers based on reports 2-8 are published below. The main contents of report 1 are reproduced in A V Gurevich's review, "Nonlinear effects in the ionosphere" [Phys. Usp. 50 1091 (2007)] and in the paper by A V Gurevich et al., "Nonlinear phenomena in the ionospheric plasma. Effects of cosmic rays and runaway breakdown on thunderstorm discharges" [Phys. Usp. 52 735 (2009)]. • Advances in quantum magnetometry for geomagnetic research , E B Aleksandrov Physics-Uspekhi, 2010, Volume 53, Number 5, Pages 487-496 • Cosmic ray variations and space weather, L I Dorman Physics-Uspekhi, 2010, Volume 53, Number 5, Pages 496-503 • Global electric circuit research: achievements and prospects, E A Mareev Physics-Uspekhi, 2010, Volume 53, Number 5, Pages 504-511 • Geophysical research in Spitsbergen Archipelago: status and prospects, V V Safargaleev, E D Tereshchenko Physics-Uspekhi, 2010, Volume 53, Number 5, Pages 511-517 • Results of solar wind and planetary ionosphere research using radiophysical methods, N A Armand, Yu V Gulyaev, A L Gavrik, A I Efimov, S S Matyugov, A G Pavelyev, N A Savich, L N Samoznaev, V M Smirnov, O I Yakovlev Physics-Uspekhi, 2010, Volume 53, Number 5, Pages 517-523 • Satellite radio probing and radio tomography of the ionosphere, V E Kunitsyn, E D Tereshchenko, E S Andreeva, I A Nesterov Physics-Uspekhi, 2010, Volume 53, Number 5, Pages 523-528 • Space research at the Pushkov Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences , V D Kuznetsov Physics-Uspekhi, 2010, Volume 53, Number 5, Pages 528-534

2010-08-01

352

Extruded Plastic Scintillator for the Minos Calorimeters.  

National Technical Information Service (NTIS)

MINOS is a long-baseline, neutrino-oscillation experiment. Two iron- and scintillator-calorimeters will be built, requiring almost 300 tons of finished plastic scintillator. In order to lower the scintillator costs, MINOS will use an extruded rectangular ...

A. Pla-Dalmau

2001-01-01

353

Properties of new scintillation glasses and scintillating fibers  

SciTech Connect

The authors present data on the light output and optical properties of new scintillation glasses. Data on light (rho approx. = 2.6g/cm/sup 3/) and heavy (rho > 3.4g/cm/sup 3/) glasses are presented. In addition, the performance of scintillating glass fibers fabricated using a new light glass is discussed.

Bross, A.D.

1986-02-01

354

Properties of New Scintillation Glasses and Scintillating Fibers  

Microsoft Academic Search

We present data on the light output and optical properties of new scintillation glasses. Data on light (¿ ¿ 2.6g\\/cm3) and heavy (¿ > 3.4g\\/cm3) glasses are presented. In addition, the performance of scintillating glass fibers fabricated using a new light glass is discussed.

Alan D. Bross

1986-01-01

355

Gravitational Wave Search with the Clock Mission  

NASA Technical Reports Server (NTRS)

Doppler tracking of distant spacecraft is the only method currently available to search for gravitational waves in the low-frequency (approx. 0.0001-0.1 Hz) band. In this technique the Doppler system measures the relative dimensionless velocity 2(delta)v/c = (delta)f/f(sub o) between the earth and the spacecraft as a function of time, where (delta)f is the frequency perturbation and f(sub o) is the nominal frequency of the radio link. A gravitational wave of amplitude h incident on this system causes small frequency perturbations, of order h in (delta)f/f(sub o), replicated three times in the observed record (Estabrook and Wahlquist 1975). All experiments to date and those planned for the near future involve only 'two-way' Doppler-i.e., uplink signal coherently transponded by the spacecraft with Doppler measured using a frequency standard common to the transmit and receive chains of the ground station. If, as on the proposed Clock Mission, there is an additional frequency standard on the spacecraft and a suitable earth-spacecraft radio system, some noise sources can be isolated and removed from the data (Vessot and Levine 1978). Supposing that the Clock Mission spacecraft is transferred into a suitable interplanetary orbit, I discuss here how the on-board frequency standard could be employed with an all-Ka-band radio system using the very high stability Deep Space Network station DSS 25 being instrumented for Cassini. With this configuration, the Clock Mission could search for gravitational waves at a sensitivity limited by the frequency standards, rather than plasma or tropospheric scintillation effects, whenever the sun-earth-spacecraft angle is greater than 90 degrees.

Armstrong, J. W.

1997-01-01

356

Radio science issues - contribution to disaster management  

Microsoft Academic Search

Radio science activities covered by URSI (International Radio Science Union) are briefly reviewed. They encompasses the knowledge and study of all aspects of electromagnetic fields and waves in a wide frequency range running from micropulsation frequencies (i.e. from ~1 mHz) to Terahertz. The topics include: electromagnetic measurements and standards, electromagnetic theory and applications, radio-communication systems and signal processing, electronics and

Francois Lefeuvre

2009-01-01

357

Well-type scintillation assembly  

Microsoft Academic Search

A scintillation detector assembly is described which employs a scintillation phosphor such as a thallium activated sodium iodide crystal, wherein a blind hole is machined in the crystal to improve the efficiency of measuring the degradation rate of a radioactive material placed therein. The performance of the assembly is defined by the energy resolution of the radiation emanating from the

M. R. Farukhi; G. A. Mataraza; O. D. Wimer

1978-01-01

358

New Cerium Activated Scintillating Glasses  

Microsoft Academic Search

The synthesis of cerium activated scintillating glasses is being continued, and two new types have been developed. One of these, a magnesium aluminum borate, is similar to the alkali borate glasses reported previously and was made in an effort to provide a scintillating glass with the highest possible boron content in which a reasonable pulse height could be retained. Its

Robert J. Ginther

1960-01-01

359

STUDY ON SOME SCINTILLATING GLASSES  

Microsoft Academic Search

Scintillation properties of lithium borosilicate cerium activated ; glasses are considered. Measurements of transmittance, excitation, fluorescence ; spectra, and pulse height distribution under thermal neutron irradiation are ; reported along with some considerations on the influence of BâOâ ; content on the scintillation properties. (auth);

G. Bertozzi; C. Coeceva; S. Pizzini

1962-01-01

360

Scintillation detector for carbon-14  

NASA Technical Reports Server (NTRS)

Detector consists of plastic, cylindrical double-wall scintillation cell, which is filled with gas to be analyzed. Thin, inner cell wall is isolated optically from outer (guard) scintillator wall by evaporated-aluminum coating. Bonding technique provides mechanical support to cell wall when device is exposed to high temperatures.

Knoll, G. F.; Rogers, W. L.

1971-01-01

361

Lithium-loaded liquid scintillators  

DOEpatents

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

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

2012-05-15

362

Equatorial scintillation and systems support  

Microsoft Academic Search

The need to nowcast and forecast scintillation for the support of operational systems has been recently identified by the interagency National Space Weather Program. This issue is addressed in the present paper in the context of nighttime irregularities in the equatorial ionosphere that cause intense amplitude and phase scintillations of satellite signals in the VHF\\/UHF range of frequencies and impact

S. Basu; E. J. Weber; M. Smitham; H. Kuenzler; C. E. Valladares; R. Sheehan; E. MacKenzie; J. A. Secan; P. Ning; W. J. McNeill; D. W. Moonan; M. J. Kendra

1997-01-01

363

Development of radiation hard scintillators  

SciTech Connect

The authors have demonstrated that the radiation stability of scintillators made from styrene polymer is very much improved by compounding with pentaphenyltrimethyltrisiloxane (DC 705 vacuum pump oil). The resulting scintillators are softer than desired, so they decided to make the scintillators directly from monomer where the base resin could be easily crosslinked to improve the mechanical properties. They can now demonstrate that scintillators made directly from the monomer, using both styrene and 4-methyl styrene, are also much more radiation resistant when modified with DC705 oil. In fact, they retain from 92% to 95% of their original light output after gamma irradiation to 10 Mrads in nitrogen with air annealing. When these scintillators made directly from monomer are compared with scintillators of the same composition made from polymer the latter have much higher light outputs. They commonly reach 83% while those made form monomer give only 50% to 60% relative to the reference, BC408. When oil modified scintillators using both p-terphenyl and tetraphenylbutadiene are compared with identical scintillators except that they use 3 hydroxy-flavone as the only luminophore the radiation stability is the same. However the 3HF system gives only 30% as much light as BC408 instead of 83% when both are measured with a green extended Phillips XP2081B phototube.

Markley, F.; Davidson, M.; Keller, J.; Foster, G.; Pla-Dalmau, A. [Fermi National Accelerator Lab., Batavia, IL (United States); Harmon, J.; Biagtan, E.; Schueneman, G. [Univ. of Florida, Gainesville, FL (United States). Physics Dept.; Senchishin, V. [Inst. for Single Crystals, Kharkov (Ukraine); Gustfason, H.; Rivard, M. [Univ. of Michigan, Ann Arbor, MI (United States)

1993-11-01

364

EISCAT measurements of interplanetary scintillation  

Microsoft Academic Search

EISCAT has been used to make three types of measurement of the characteristics of the solar wind in the range 10–120 solar radii. The rms fluctuation in the total power received from a single source can be measured to provide a `scintillation index'. The cross-correlation of the scintillations observed at two sites can be used to measure the velocity of

A. R. Breen; W. A. Coles; R. Grall; U.-P. Levhaug; J. Markkanen; H. Misawas; P. J. S. Williams

1996-01-01

365

Gamma-Ray and Radio Observations of PSR B1509-58.  

National Technical Information Service (NTIS)

We report concurrent radio and gamma-ray observations of PSR B1509-58 carried out by the Parkes Radio Telescope and by the Burst and Transient Source Experiment (BATSE) and the Oriented Scintillation Spectrometer Experiment (OSSE) on the Compton Gamma Ray...

K. S. Hagedon M. J. Finger M. P. Ulmer R. B. Wilson S. M. Matz

1993-01-01

366

Survey and prediction of the ionospheric scintillation using data mining techniques  

Microsoft Academic Search

Irregularly structured ionospheric regions may cause amplitude and phase fluctuations of radio signals. Such distortion is called ionospheric scintillation. These ionospheric irregularities occur as part of depleted plasma density regions that are generated at the magnetic equator after sunset by equatorial ionospheric plasma instability mechanism. Also known as ionospheric bubbles, they drift upward to high altitudes at the equator and

L. F. C. Rezende; E. R. de Paula; S. Stephany; I. J. Kantor; M. T. A. H. Muella; P. M. de Siqueira; K. S. Correa

2010-01-01

367

Characterization of GNSS signal parameters under ionosphere scintillation conditions using software-based tracking algorithms  

Microsoft Academic Search

This paper analyzes the carrier tracking outputs of GPS L1 signals during ionosphere scintillations using a conventional PLL, a frequency-assisted PLL, and a Kalman filter based PLL. The data used in the analysis were collected by a radio frequency front end at Ascension Island in March 2001. Among the 8 GPS satellites in view during the 45 minutes data collection

Lei Zhang; Yu Morton; Frank van Graas; Theodore Beach

2010-01-01

368

Planetary radio astronomy experiment for Voyager missions  

Microsoft Academic Search

The planetary radio astronomy experiment will measure radio spectra of planetary emissions in the range 1.2 kHz to 40.5 MHz. These emissions result from wave-particle-plasma interactions in the magnetospheres and ionospheres of the planets. At Jupiter, they are strongly modulated by the Galilean satellite Io.

J. W. Warwick; J. B. Pearce; R. G. Peltzer; A. C. Riddle

1977-01-01

369

HUT Radio Laboratory Research and Education 2001.  

National Technical Information Service (NTIS)

The Radio Laboratory is active in research and education in the fields of RF, microwave and millimeter wave techniques and their applications. The Radio Laboratory has now 3 professors as Dr. Pekka Eskelinen started on January 1, 2001 ad the forth profess...

P. Vainkainen S. Lindberg

2003-01-01

370

Total electron content and scintillation in the vicinity of the main ionospheric trough over Northern Europe. Final report, 1 Jul 90-30 Jun 91  

SciTech Connect

A receiving system for NNSS satellites located at Lerwick (60.1N, 1.2W) has been used to make differential carrier phase measurements in the vicinity of the main ionospheric trough. The observations have been calibrated to obtain absolute total electron content using measurements from a co-located GPS receiver for two months near solar maximum. Mapping techniques, developed to study the changes in night-time total electron content as a function of both latitude and time, are described. Examples are given of characteristic trough behaviour for different levels of geomagnetic activity. A new feature of the work is the limited extent of the poleward wall of the trough for moderate geomagnetic conditions. The mapping techniques can also be applied to measurements of radio-wave scintillation allowing comparison between small-scale irregularity behaviour and the larger-scale changes in total electron content.

Kersley, L.; Walker, I.K.

1991-06-30

371

Radio science investigations by VeRa onboard the Venus Express spacecraft  

NASA Astrophysics Data System (ADS)

The Venus Express Radio Science Experiment (VeRa) uses radio signals at wavelengths of 3.6 and 13 cm ("X"- and "S"-band, respectively) to investigate the Venus surface, neutral atmosphere, ionosphere, and gravity field, as well as the interplanetary medium. An ultrastable oscillator (USO) provides a high quality onboard reference frequency source; instrumentation on Earth is used to record amplitude, phase, propagation time, and polarization of the received signals. Simultaneous, coherent measurements at the two wavelengths allow separation of dispersive media effects from classical Doppler shift. VeRa science objectives include the following: Determination of neutral atmospheric structure from the cloud deck (approximately 40 km altitude) to 100 km altitude from vertical profiles of neutral mass density, temperature, and pressure as a function of local time and season. Within the atmospheric structure, search for, and if detected, study of the vertical structure of localized buoyancy waves, and the presence and properties of planetary waves. Study of the H 2SO 4 vapor absorbing layer in the atmosphere by variations in signal intensity and application of this information to tracing atmospheric motions. Scintillation effects caused by radio wave diffraction within the atmosphere can also provide information on small-scale atmospheric turbulence. Investigation of ionospheric structure from approximately 80 km to the ionopause (<600 km), allowing study of the interaction between solar wind plasma and the Venus atmosphere. Observation of forward-scattered surface echoes obliquely reflected from selected high-elevation targets with anomalous radar properties (such as Maxwell Montes). More generally, such bistatic radar measurements provide information on the roughness and density of the surface material on scales of centimeters to meters. Detection of gravity anomalies, thereby providing insight into the properties of the Venus crust and lithosphere. Measurement of the Doppler shift, propagation time, and frequency fluctuations along the interplanetary ray path, especially during periods of superior conjunction, thus enabling investigation of dynamical processes in the solar corona.

Häusler, B.; Pätzold, M.; Tyler, G. L.; Simpson, R. A.; Bird, M. K.; Dehant, V.; Barriot, J.-P.; Eidel, W.; Mattei, R.; Remus, S.; Selle, J.; Tellmann, S.; Imamura, T.

2006-11-01

372

Simplified BS without light source and RF local oscillator in full duplex millimeter-wave radio-on-fiber system based upon external modulation technique  

Microsoft Academic Search

A simpler full-duplex radio-on-fiber system using a single light source is investigated. Error-free simultaneous fiber-optic transmission of 60-GHz-band down- and uplink signals over 25-km-long standard single-mode fibers is experimentally demonstrated without serious dispersion problem

Toshiaki Kuri; Ken-ichi Kitayama; Yoshiro Takahashi

1999-01-01

373

Scintillation analysis for multiple uplink Gaussian beams in the presence of beam wander  

NASA Astrophysics Data System (ADS)

For a beam from ground to space, the main optical turbulence effects are scintillation and beam wander. Multiple incoherent beams can reduce the scintillation. The scintillation is determined by the number of the beams, the beam separation and the size of the beam wander variance. A wave optics simulation was applied to study the scintillation index of 1-, 3, 6 collimated uplink Gaussian beams, where a hexagonal close-pack spacing is used. Based on the results of simulations, we propose an approximation to average spatial correlation in terms of the beam separation in the tracked and untracked cases. The relation between scintillation index and beam separation is different in the weak and moderately-strong fluctuation regimes when the number of beams is the same. And the average spatial correlation is determined by the beam waist radius, beam separation and beam wander variance.

Wu, Wu-ming; Ning, Yu; Zhang, Peng-fei; Feng, Xiao-xing; Qiao, Chun-hong

2014-02-01

374

Optical and Radio Remote Sensing of Space Plasma Turbulence.  

National Technical Information Service (NTIS)

Experiments were conducted at Arecibo, Puerto Rico to investigate naturally-occurring and radio wave-induced ionospheric plasma turbulence. The intriguing phenomena reported here include large-scale turbulence created by tsunami-launched gravity waves (Le...

M. Lee

2008-01-01

375

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

376

VHF scintillations as a diagnostic tool for the study of ionospheric irregularities  

NASA Astrophysics Data System (ADS)

In this paper we present the results of observations of the scintillations of radio beacon on 250.351 MHz from geostationary satellite FLEETSAT (73 deg E) recorded at Bombay on April 9-10, 1992 during night hours. The scintillation index, S(sub 4), is used to describe the strength of the scintillations. The variation of scintillation index with local time shows a maxima of 0.589 at 02:55 India Standard Time (IST). This scintillation activity is linked with the spread F-irregularities. A brief description of the scintillation theories like phase screen theory and theory for weak scintillations -- Rytov solution is given. These theories provide an integral measure of the fluctuations in terms of phase and amplitude fluctuations imposed on VHF signals while traversing through the ionosphere. Power spectrum analysis for the log-amplitude and phase departure and cross spectrum between them have also been carried out. Using spectral index p = 1, we have shown that the scale sizes for the ionospheric irregularities are greater than 1 km.

Ahmad, Altaf; Ahmad, M. M.; Pathan, B. M.

1994-01-01

377

Radio astronomy  

NASA Technical Reports Server (NTRS)

The following subject areas are covered: (1) scientific opportunities (millimeter and sub-millimeter wavelength astronomy; meter to hectometer astronomy; the Sun, stars, pulsars, interstellar masers, and extrasolar planets; the planets, asteroids, and comets; radio galaxies, quasars, and cosmology; and challenges for radio astronomy in the 1990's); (2) recommendations for new facilities (the millimeter arrays, medium scale instruments, and small-scale projects); (3) continuing activities and maintenance, upgrading of telescopes and instrumentation; (4) long range programs and technology development; and (5) social, political, and organizational considerations.

Kellermann, Kenneth I.; Heeschen, David; Backer, Donald C.; Cohen, Marshall H.; Davis, Michael; Depater, Imke; Deyoung, David; Dulk, George A.; Fisher, J. R.; Goss, W. Miller

1991-01-01

378

Scintillating optical fiber trajectory detectors  

NASA Astrophysics Data System (ADS)

Measurements of attenuation in several types of plastic scintillating optical fibers give attenuation lengths varying from 0.8 to 1.5 m. By comparing attenuation as a function of wavelength in fibers of different thicknesses we infer the contributions to the attenuation from reflection losses and bulk scintillation losses. We find good agreement between these values and calculated estimates of attenuation in scintillator. We have also calculated the effective scintillation efficiency of small fibers relative to that of bulk scintillator (for scintillator with dimethyl POPOP as the waveshifting dye) for the two cases of optically coupled and decoupled fibers. Scintillating fiber ribbons made of 200 ?m square cross section fibers were exposed to relativistic iron nuclei at the LBL Bevalac, and positional resolution of 70 ?m was obtained. Relativistic neon and carbon were also detected in these ribbons. In a similar exposure of 100 ?m fibers to 50 MeV/n nitrogen nuclei at the NSCL cyclotron, Michigan State University, a positional resolution of about 50 ?m was obtained.

Davis, A. J.; Hink, P. L.; Binns, W. R.; Epstein, J. W.; Connell, J. J.; Israel, M. H.; Klarmann, J.; Vylet, V.; Kaplan, D. H.; Reucroft, S.

1989-03-01

379

Proton recoil scintillator neutron rem meter  

DOEpatents

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

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

2003-01-01

380

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

381

Solar Type II Radio Bursts and IP Type II Events  

Microsoft Academic Search

We have examined radio data from the WAVES experiment on the Wind spacecraft in conjunction with ground-based data in order to investigate the relationship between the shocks responsible for metric type II radio bursts and the shocks in front of coronal mass ejections (CMEs). The bow shocks of fast, large CMEs are strong interplanetary (IP) shocks, and the associated radio

H. V. Cane; W. C. Erickson

2005-01-01

382

A Simple Radio Receiver Aids Understanding of Wireless Communication  

ERIC Educational Resources Information Center

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

Straulino, S.; Orlando, A.

2012-01-01

383

Development of radio seeing monitor using LEO satellite beacons  

Microsoft Academic Search

To monitor the atmospheric conditions in the radio astronomical observations, we have developed a new type of the radio seeing monitor, which enables us to measure the atmospheric turbulence in real-time and in a wide range of the direction in the celestial hemisphere. The base of the measurement system is a radio interferometer, in which the beacon waves of low

Masanori Nishio; Tomonari Suzuyama; Hiroshi Kohashiguchi; Tomoyuki Miyazaki; Yoshio Sumino; Takafusa Ando; Masako Hirata; Qinghui Liu

2002-01-01

384

Geophysical properties of the ionospheric irregularities responsible for radio scintillation  

NASA Technical Reports Server (NTRS)

The properties of F-region ionospheric irregularities are described based on in-situ measurements of the actual waveforms of ion concentration. The spectral properties of the irregularities are discussed. In high, middle and low latitudes most of the irregularities observed fall into a single 'noiselike' category having power spectra which can be approximated by f to the negative n-th power and S to the n-th power, where S is the irregularity scale size and n is approximately 2. Thus the spectral components have a maximum gradient which is almost independent of their size. Other categories of irregularities are also observed occasionally.

Mcclure, J. P.

1974-01-01

385

Scintillator materials containing lanthanum fluorides  

DOEpatents

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

Moses, W.W.

1991-05-14

386

Scintillator materials containing lanthanum fluorides  

DOEpatents

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

Moses, William W. (Berkeley, CA)

1991-01-01

387

Properties of scintillator solutes  

SciTech Connect

This special report summarizes measurements of the spectroscopic and other properties of the solutes that were used in the preparation of several new liquid scintillators developed at EG and G/Energy Measurements/Santa Barbara Operations (the precursor to Bechtel Nevada/Special Technologies Laboratory) on the radiation-to-light converter program. The data on the individual compounds are presented in a form similar to that used by Prof. Isadore Berlman in his classic handbook of fluorescence spectra. The temporal properties and relative efficiencies of the new scintillators are presented in Table 1, and the efficiencies as a function of wavelength are presented graphically in Figure 1. In addition, there is a descriptive glossary of the abbreviations used herein. Figure 2 illustrates the basic structures of some of the compounds and of the four solvents reported in this summary. The emission spectra generally exhibit more structure than the absorption spectra, with the result that the peak emission wavelength for a given compound may lie several nm away from the wavelength, {lambda}{sub avg}, at the geometric center of the emission spectrum. Therefore, the author has chosen to list absorption peaks, {lambda}{sub max}, and emission {lambda}{sub avg} values in Figures 3--30, as being most illustrative of the differences between the compounds. The compounds, BHTP, BTPB, ADBT, and DPTPB were all developed on this program. P-terphenyl, PBD, and TPB are commercially available blue emitters. C-480 and the other longer-wavelength emitters are laser dyes available commercially from Exciton Corporation. 1 ref., 30 figs.

Fluornoy, J.M.

1998-06-01

388

Estimating random transverse velocities in the fast solar wind from EISCAT Interplanetary Scintillation measurements  

Microsoft Academic Search

Interplanetary scintillation measurements can yield estimates of a large number of solar wind parameters, including bulk flow speed, variation in bulk velocity along the observing path through the solar wind and random variation in transverse velocity. This last parameter is of particular interest, as it can indicate the flux of low-frequency Alfvén waves, and the dissipation of these waves has

A. Canals; A. R. Breen; L. Ofman; P. J. Moran; R. A. Fallows

2002-01-01

389

Scintillating glass fiber neutron sensors.  

National Technical Information Service (NTIS)

Cerium-doped lithium-silicate glass fibers have been developed at Pacific Northwest Laboratory (PNL) for use as thermal neutron detectors. By using highly-enriched (sup 6) Li , these fibers efficiently capture thermal neutrons and produce scintillation li...

K. H. Abel R. J. Arthur M. Bliss

1994-01-01

390

Development of intrinsic IPT scintillator.  

National Technical Information Service (NTIS)

We report on the development of a new polystyrene based plastic scintillator. Optical absorption, fluorescence and light output measurements are presented. Preliminary results of radiation damage effects are also given and compared to the effects on a com...

A. D. Bross

1989-01-01

391

Scintillator fiber optic long counter  

DOEpatents

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

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

1994-01-01

392

Gravity waves in Titan's atmosphere  

Microsoft Academic Search

Scintillations (high frequency variations) observed in the radio signal during the occultation of Voyager 1 by Titan (Hinson and Tyler, 1983) provide information concerning neutral atmospheric density fluctuations on scales on hundreds of meters to a few kilometers. Those seen at altitudes higher than 25 km above the surface were interpreted by Hinson and Tyler as being caused by linear,

A. James Friedson

1994-01-01

393

About NICADD extruded scintillating strips  

SciTech Connect

The results of control measurements of extruded scintillating strip responses to a radioactive source Sr-90 are provided, and details of strip choice, preparation, and method of measurement are included. About four hundred one meter long extruded scintillating strips were measured at four different points. These results were essential for prototyping a tail catcher and muon tracker for a future international electron positron linear collider detector.

Dyshkant, A.; Beznosko, D.; Blazey, G.; Chakraborty, D.; Francis, K.; Kubik, D.; Lima, J.G.; Rykalin, V.; Zutshi, v.; /Northern Illinois U.; Baldina, E.; Bross, A.; Deering, P.; Nebel, T.; Pla-Dalmau, A.; Schellpfeffer, J.; Serritella, C.; Zimmerman, J.; /Fermilab

2005-04-01

394

Scintillating glass fiber neutron senors  

Microsoft Academic Search

Cerium-doped lithium-silicate glass fibers have been developed at Pacific Northwest Laboratory (PNL) for use as thermal neutron detectors. By using highly-enriched ⁶ Li , these fibers efficiently capture thermal neutrons and produce scintillation light that can be detected at the ends of the fibers. Advantages of scintillating fibers over ³He or BFâ proportional tubes include flexibility in geometric configuration, ruggedness

K. H. Abel; R. J. Arthur; M. Bliss; D BRITE; R BRODZINSKI; R CRAIG; B GEELHOOD; D GOLDMAN; J GRIFFIN; R PERKINS

1994-01-01

395

New low cost acrylic scintillators  

NASA Astrophysics Data System (ADS)

We have developed a variety of new acrylic scintillators. One of them is to be used in calorimetry in combination with the wavelength shifter bar technique and the others in a more classical way, directly coupled to photomulitpliers. Their common characteristic is a high light output together with a low cost. We present the mechanical and opitcal properties of these scintillators and compare them with some commonly used existing ones.

Aurouet, C.; Blumenfeld, H.; Bosc, G.; Bourdinaud, M.; Evrard, P.; Jeanney, C.; Lafond, C.

1980-02-01

396

Lunar components in Lunping scintillations  

NASA Astrophysics Data System (ADS)

Fourteen consecutive years of 15-min scintillation index values observed in Lunping, Taiwan have been analyzed by the lunar age superposition method. Analysis covers 24 hrs/day and is performed separately for each of the four seasons. Statistically significant first and second lunar harmonics have been found at all seasons, but the largest and most significant occur in the summertime data. During the daytime the probability of scintillations at Lunping is significantly correlated with f(0)E(s). We conclude that our lunar harmonics probably result from the modulation, in the E region, of neutral winds of solar thermal origin by upward propagating lunar tides. The nighttime scintillations are larger and tidal neutral air velocities seem to play a role in the production mechanism(s). There is clear evidence for both the summertime temperate latitude type of scintillations observed in Japan and the scintillations, mainly equinoctial, arising from the equatorial bubble mechanism. Four distinct statistically significant summertime scintillation periods are found, plus one each in the autumnal and winter data. An attempt is made to identify the production mechanism associated with each.

Koster, John R.; Huang, Yinn-Nien; Lue, H. Y.; Wu, Hsi-Shu

1993-08-01

397

Radiation effects on wavelength shifting fibers used with liquid scintillators  

SciTech Connect

The chemical compatibility of wave length shifting fibers with several liquid scintillators has been investigated. Based on systematic characterization of the behavior of the BC-517 family, a time of life of 70{endash}450 years was estimated for the polystyrene based wave length shifting fiber in BC-517P scintillator. WLS (wavelength shifting) fibers irradiated continuously to a dose of 6.4 Mrads (at .377Mrad/hr of Co-60) were observed to decrease from 100% to 5% transmission; however, after 100 hours of annealing, the transmission increased to 90%. Geant simulations of a simplified calorimeter located behind a BaF2 electromagnetic calorimeter for the GEM detector at SSC showed that the constant term in the energy resolution will change from 1.8 to 2.9 in five years at 10{star}{star}34 luminosity for psuedorapidity eta=3.

Ables, E.; Armatis, P.; Bionta, R.; Britt, H.; Clamp, O.; Cochran, C.; Graham, G.; Lowry, M.; Masquelier, D.; Skulina, K.; Wuest, C. [Lawrence Livermore National Lab., CA (United States); Bolen, L.; Cremaldi, L.; Harper, S.; Moore, B.; Quinn, B.; Reidy, J.; Zhou, J. [Mississippi Univ., University, MS (United States); Croft, L.; Piercey, R. [Mississippi State Univ., MS (United States); Bauer, M.L.; Bishop, B.L.; Cohn, H.O.; Gabriel, T.A.; Gordeev, A.; Kamyshkov, Yu.; Lillei, R.A.; Plasil, F.; Read, K.; Rennich, M.J.; Savin, A.; Shmakov, K.; Singeltary, B.H.; Smirnov, A.; Tarkovsky, E.; Todd, R.A.; Young, K.G. [Oak Ridge National Lab., TN (United States); Berridge, S.C.; Bugg, W.M.; Handler, T.; Pisharody, M. [Tennessee Univ., Knoxville, TN (United States); Aziz, T.; Banerjee, S.; Chendvankar, S.R.; Ganfuli, S.N.; Malhotra, K.; Mazumdar, K.; Raghavan, R.; Shankar, K.; Sudhakar, K.; Tonwar, S.C. [Tata Inst. of Fundamental Research, Bombay (India); Arefiev, A.; Baranov, O.; Efremenko, Yu.; Gorodkov, Yu.; Malinin, A.; Nikitin, A.; Markizov, V.; Onoprienko, D.; Rozjkov, A.; Shoumilov, E.; Shoutko, V. [Institute for Theoretical and Experimental Research, Moscow (Russia)

1992-06-01

398

Full-wave consistent MDS-based simulation of a beam-waveguide circuit fragment for a deep space communication or radio astronomy antenna  

Microsoft Academic Search

In this paper we perform full-wave two-dimensional (2-D) simulation of the e-polarized beam wave guidance and scattering by a chain of four finite-size reflectors and mirrors modelling a typical fragment of quasioptical feeding circuit of a deep-space communication antenna. Elementary geometry tuning aimed at the maximum circuit transmission is also demonstrated. The feed beam generated by the aperture of a

Andrey A. Nosich; Ronan Sauleau; Yuriy V. Gandel

2008-01-01

399

Rise-Time Characteristics of Organic Solution Scintillators  

Microsoft Academic Search

A special demountable cathode-ray tube has been designed to produce electron-beam excitation of organic scintillator solutions. Solutions are irradiated through an electron-permeable window. The beam is swept across the window in 0.4 ?? 10-9 seconds. A 1P28 photomultiplier and traveling-wave oscilloscope are used in recording. About 25,000 mev of excitation energy is delivered per pulse and pulse oscillograms are free

D. F. McDonald; B. J. Dunn; J. V. Braddock

1960-01-01

400

The Radio JOVE Project - Shoestring Radio Astronomy  

NASA Technical Reports Server (NTRS)

Radio JOVE is an education and outreach project intended to give students and other interested individuals hands-on experience in learning radio astronomy. They can do this through building a radio telescope from a relatively inexpensive kit that includes the parts for a receiver and an antenna as well as software for a computer chart recorder emulator (Radio Skypipe) and other reference materials

Thieman, J.; Flagg, R.; Greenman, W.; Higgins, C.; Reyes, F.; Sky, J.

2010-01-01

401

Flux tube analysis of L-band ionospheric scintillation  

NASA Astrophysics Data System (ADS)

This manuscript presents magnetic flux tube analysis of L-band signal scintillation in the nighttime equatorial and low-latitude ionosphere. Residues of the scintillation index S4 estimated from the L-band signals received from Geostationary Earth Orbit (GEO) satellites are employed in the analysis. The S4 estimates have been shown to be associated with simultaneous GPS VTEC variations derived from JPL's GIPSY-GIM package. We have applied the wavelet decomposition technique simultaneously on the S4 time series in a flux tube over the equatorial and low-latitude regions. The technique decomposes the S4 signal to identify the dominant mode of variabilities and the temporal variations of scintillation-producing irregularities in the context of a flux tube. Statistically significant regions of the wavelet power spectra considered in our study have mainly shown that (a) dominant plasma irregularities associated with S4 variabilities in a flux tube have periods of about 4 to 15 minutes (horizontal irregularity scales of about 24 to 90 km). These periods match short period gravity waves, (b) scintillation-producing irregularities are anisotropic along the flux tube and in the east-west direction, and (c) the occurrences of scintillation-producing irregularities along the flux tube indicate that the entire flux tube became unstable. However, plasma instability occurrences were not simultaneous in most cases along the flux tube, there were time delays of various orders. Understanding the attributes of L-band scintillation-producing irregularities could be important for developing measures to mitigate L-band signal degradation.

Shume, E. B.; Mannucci, A. J.; Butala, M. D.; Pi, X.; Valladares, C. E.

2013-06-01

402

Space Telecommunications Radio System STRS Cognitive Radio  

NASA Technical Reports Server (NTRS)

Radios today are evolving from awareness toward cognition. A software defined radio (SDR) provides the most capability for integrating autonomic decision making ability and allows the incremental evolution toward a cognitive radio. This cognitive radio technology will impact NASA space communications in areas such as spectrum utilization, interoperability, network operations, and radio resource management over a wide range of operating conditions. NASAs cognitive radio will build upon the infrastructure being developed by Space Telecommunication Radio System (STRS) SDR technology. This paper explores the feasibility of inserting cognitive capabilities in the NASA STRS architecture and the interfaces between the cognitive engine and the STRS radio. The STRS architecture defines methods that can inform the cognitive engine about the radio environment so that the cognitive engine can learn autonomously from experience, and take appropriate actions to adapt the radio operating characteristics and optimize performance.

Briones, Janette C.; Handler, Louis M.

2013-01-01

403

Imaging of indoor multipath radio propagation for 18 GHz band wireless LAN systems: applied radio holography  

Microsoft Academic Search

Development of high-speed wireless LANs is a major goal of telecommunications industry. We propose a dual-frequency continuous wave (CW) radio holography method for evaluating radio wave propagation environments for such LANs. Our method images the propagation environment with higher resolution (1 ns or less) and higher sensitivity (10 dB ?V\\/m) than conventional techniques which use frequency-modulated CWs (FMCWs), pseudonoise (PN)

H. Kitayoshi

1994-01-01

404

IPS limits on very low frequency VLBI. [Interplanetary Scintillation  

NASA Technical Reports Server (NTRS)

The ability of a space-based radio interferometer array to make high resolution images at frequencies of only a few MHz will be limited by interplanetary scintillation. Numerical simulations have been used to study the severity of interferometer phase fluctuations caused by the density fluctuations in the solar wind over a range of frequencies and solar elongation angles. The impact of these fluctuations on the quality of radio images produced has also been investigated. The results show that, for baselines up to 100 km, accurate imaging should be possible when nu sin (epsilon/2) is equal to or greater than 2.5, where nu is the observing frequency in MHz and epsilon is the solar elongation angle.

Jones, Dayton L.; Williamson, Robert S., III

1990-01-01

405

Cassini/RPWS: A low frequency radio imager at Saturn  

NASA Astrophysics Data System (ADS)

The High Frequency Receiver (HFR) of the Radio and Plasma Waves Science experiment (RPWS) onboard Cassini is a sensitive, and versatile radio instrument. Although the radio antenna connected to this instrument have no intrinsic directivity, the HFR measurements can provide instantaneous direction of arrival, flux density and polarization degree of the observed radio waves. Hence, the HFR can be described as an full-sky radio imager. As the instrument provides direction of arrival, radio sources can be located with some assumption on the propagation between the source and the observer. Hence, it is possible to produce radio source maps and correlate them with observations at other wavelengths, such as UV or IR observations of the auroral regions of Saturn. The flux and polarization measurements together with the time-frequency shape of the radio emissions can also be used to identify the radio emission processes. We present a review of the results of the Cassini/RPWS/HFR observations since its arrival at Saturn in 2004: interpretation of the radio arc shapes and equatorial shadow zones; in-situ observations in the radio source region; comparison with other wavelengths and particle measurements; confirmation of the Cyclotron Maser Instability (CMI) as the main emission mechanism for auroral radio emissions; monitoring of the radio emission variability in time and location, etc.

Cecconi, Baptiste; Lamy, Laurent; Zarka, Philippe

2014-05-01

406

FNAL-NICADD extruded scintillator  

SciTech Connect

The possibility to produce a scintillator that satisfies the demands of physicists from different science areas has emerged with the installation of an extrusion line at Fermi National Accelerator Laboratory (FNAL). The extruder is the product of the fruitful collaboration between FNAL and Northern Illinois Center for Accelerator and Detector Development (NICADD) at Northern Illinois University (NIU). The results from the light output, light attenuation length and mechanical tolerance indicate that FNAL-NICADD scintillator is of high quality. Improvements in the extrusion die will yield better scintillator profiles and decrease the time needed for initial tuning. This paper will present the characteristics of the FNAL-NICADD scintillator based on the measurements performed. They include the response to MIPs from cosmic rays for individual extruded strips and irradiation studies where extruded samples were irradiated up to 1 Mrad. We will also discuss the results achieved with a new die design. The attractive perspective of using the extruded scintillator with MRS (Metal Resistive Semiconductor) photodetector readout will also be shown.

Beznosko, D.; /Northern Illinois U.; Bross, A.; /Fermilab; Dyshkant, A.; /Northern Illinois U.; Pla-Dalmau, A.; /Fermilab; Rykalin, V.; /Northern Illinois U.

2005-09-01

407

Mitigation of scintillation noise by common mode rejection  

NASA Astrophysics Data System (ADS)

There is increasing interest in free space optical communications as an alternative to fibre optics and radio frequency communications, particularly in 'last mile' applications and applications with weight and power restrictions e.g. communications with unmanned aerial vehicles. The potential advantages of free space optical communications include: high bandwidth; no licensing issues; smaller, lighter payloads; low probability of intercept; and immunity from interference/jamming. However, propagation through the atmosphere is subject to atmospheric scintillation noise affecting the signal-to-noise ratio (SNR), effectively reducing the range and bandwidth of the communication link. This scintillation is experienced even over relatively short propagation paths and is caused by small temperature variations in the atmosphere, resulting in index of refraction changes. In this paper we present a technique to correct for atmospheric scintillation noise in free space optical communications and laser remote sensing. It uses common mode rejection to remove co-channel noise, where each channel is transmitted on separate, but closely spaced, wavelengths. The signal-to-noise ratio is significantly increased, thereby increasing the range and/or bandwidth of the link. To date, tests have been conducted with analogue audio and video transmissions. This has been successful, with improvements of up to 12dB in SNR having been demonstrated. This has been limited by the current implementation, which is only at prototype stage -- the ultimate achievable improvement in SNR is anticipated to be significantly higher.

Grant, Kenneth J.; Corbett, Kerry A.; Clare, Bradley A.; Davies, James E.; Nener, Brett D.

2005-05-01

408

Scintillating glass fiber neutron senors  

SciTech Connect

Cerium-doped lithium-silicate glass fibers have been developed at Pacific Northwest Laboratory (PNL) for use as thermal neutron detectors. By using highly-enriched {sup 6} Li , these fibers efficiently capture thermal neutrons and produce scintillation light that can be detected at the ends of the fibers. Advantages of scintillating fibers over {sup 3}He or BF{sub 3} proportional tubes include flexibility in geometric configuration, ruggedness in high-vibration environments, and less detector weight for the same neutron sensitivity. This paper describes the performance of these scintillating fibers with regard to count rates, pulse height spectra, absolute efficiencies, and neutron/gamma discrimination. Fibers with light transmission lengths (1/e) of greater than 2 m have been produced at PNL. Neutron sensors in fiber form allow development of a variety of neutron detectors packaged in previously unavailable configurations. Brief descriptions of some of the devices already produced are included to illustrate these possibilities.

Abel, K.H.; Arthur, R.J.; Bliss, M.

1994-04-01

409

Unitary scintillation detector and system  

DOEpatents

The invention is a unitary alpha, beta, and gamma scintillation detector and system for sensing the presence of alpha, beta, and gamma radiations selectively or simultaneously. The scintillators are mounted in a light-tight housing provided with an entrance window for admitting alpha, beta, and gamma radiation and excluding ambient light from the housing. Light pulses from each scintillator have different decay constants that are converted by a photosensitive device into corresponding differently shaped electrical pulses. A pulse discrimination system identifies the electrical pulses by their respective pulse shapes which are determined by decay time. The identified electrical pulses are counted in separate channel analyzers to indicate the respective levels of sensed alpha, beta, and gamma radiations.

McElhaney, Stephanie A. (Oak Ridge, TN); Chiles, Marion M. (Knoxville, TN)

1994-01-01

410

Unitary scintillation detector and system  

DOEpatents

The invention is a unitary alpha, beta, and gamma scintillation detector and system for sensing the presence of alpha, beta, and gamma radiations selectively or simultaneously. The scintillators are mounted in a light-tight housing provided with an entrance window for admitting alpha, beta, and gamma radiation and excluding ambient light from the housing. Light pulses from each scintillator have different decay constants that are converted by a photosensitive device into corresponding differently shaped electrical pulses. A pulse discrimination system identifies the electrical pulses by their respective pulse shapes which are determined by decay time. The identified electrical pulses are counted in separate channel analyzers to indicate the respective levels of sensed alpha, beta, and gamma radiations. 10 figs.

McElhaney, S.A.; Chiles, M.M.

1994-05-31

411

Fracture-resistant lanthanide scintillators  

DOEpatents

Lanthanide halide alloys have recently enabled scintillating gamma ray spectrometers comparable to room temperature semiconductors (<3% FWHM energy resolutions at 662 keV). However brittle fracture of these materials upon cooling hinders the growth of large volume crystals. Efforts to improve the strength through non-lanthanide alloy substitution, while preserving scintillation, have been demonstrated. Isovalent alloys having nominal compositions of comprising Al, Ga, Sc, Y, and In dopants as well as aliovalent alloys comprising Ca, Sr, Zr, Hf, Zn, and Pb dopants were prepared. All of these alloys exhibit bright fluorescence under UV excitation, with varying shifts in the spectral peaks and intensities relative to pure CeBr.sub.3. Further, these alloys scintillate when coupled to a photomultiplier tube (PMT) and exposed to .sup.137Cs gamma rays.

Doty, F. Patrick (Livermore, CA)

2011-01-04

412

Nanophosphor composite scintillator with a liquid matrix  

DOEpatents

An improved nanophosphor scintillator liquid comprises nanophosphor particles in a liquid matrix. The nanophosphor particles are optionally surface modified with an organic ligand. The surface modified nanophosphor particle is essentially surface charge neutral, thereby preventing agglomeration of the nanophosphor particles during dispersion in a liquid scintillator matrix. The improved nanophosphor scintillator liquid may be used in any conventional liquid scintillator application, including in a radiation detector.

McKigney, Edward Allen (Los Alamos, NM) [Los Alamos, NM; Burrell, Anthony Keiran (Los Alamos, NM) [Los Alamos, NM; Bennett, Bryan L. (Los Alamos, NM) [Los Alamos, NM; Cooke, David Wayne (Santa Fe, NM) [Santa Fe, NM; Ott, Kevin Curtis (Los Alamos, NM) [Los Alamos, NM; Bacrania, Minesh Kantilal (Los Alamos, NM) [Los Alamos, NM; Del Sesto, Rico Emilio (Los Alamos, NM) [Los Alamos, NM; Gilbertson, Robert David (Los Alamos, NM) [Los Alamos, NM; Muenchausen, Ross Edward (Los Alamos, NM) [Los Alamos, NM; McCleskey, Thomas Mark (Los Alamos, NM) [Los Alamos, NM

2010-03-16

413

Distributed feedback lasing of commercial liquid scintillators.  

PubMed

It is shown that lasing can be achieved in commercial organic liquid scintillators. Using a dynamic grating induced by an interference pattern in the scintillator volume, distributed feedback lasing is shown to occur in four out of five commercial liquid scintillators that have been investigated. Although these scintillators are not designed for lasing application, their purpose being to measure radioactivity, induction of a laser effect, furthermore with a tuning range of approximately 30 nm, has been attained. PMID:24322244

Michel, Maugan; Rocha, Licinio; Hamel, Matthieu; Normand, Stéphane; Angélique, Jean-Claude

2013-12-15

414

Study of a Coincident Observation Between the Ionospheric Density Irregularities and Ground Scintillation Experiment  

NASA Astrophysics Data System (ADS)

A coincident observation was made on March 24, 2000 between the ROCSAT observed density irregularities at the 600-km altitude and the Ascension Island scintillation experiment. Although the observed density irregularity structure did not show particularly large, the ground scintillation observed in VHF and L bands indicated strong scintillation has occurred with S4 indices in both channels hovering around 1 and above. The characteristics of density irregularities in space and the scintillation signals on the ground are studied separately and then compared against each other for the coincident observation. In addition, the parabolic equation of Yeh and Liu (1982) was used to carry out a numerical simulation of a plane EM wave passing through the observed density irregularity structure to obtain the scintillation effect observed on the ground for comparison with the Ascension Island experiment. The gross feature in the temporal and amplitudinal variations of the simulated scintillation resemble very well with the ground observed scintillation signals. However, there still uncertainties existed in the study of the coincident event and these will be discussed in the presentation.

Su, S.; Liu, C.; Liu, Y.; Chao, C.

2012-12-01

415

Interplanetary Scintillation, STEREO Heliospheric Imager and Venus Express ASPERA observations of solar wind structures in May 2007  

Microsoft Academic Search

We present results from a co-ordinated study of solar wind structure in the inner helisphere during May 2007, combining results from radio measurements of interplanetary scintillation (IPS), STEREO HI imaging of interplanetary structures and in-situ measurements from the ASPERA instrument on Venus Express. The ASPERA results revealed periodic disturbances in the solar wind at Venus, which we show correspond to

A. R. Breen; G. D. Dorrian; D. S. Brown; I. Whittaker; R. A. Fallows; J. A. Davies; A. Roulliard

2009-01-01

416

A new view of solar wind structures: Combined interplanetary scintillation and STEREO HI studies of the inner solar wind  

Microsoft Academic Search

The heliospheric imagers (HI) on the STEREO A and B spacecraft are now providing the first continuous, detailed images of structures in the interplanetary solar wind. When combined with simultaneous radio measurements of interplanetary scintillation (IPS), STEREO images allow the structure of the solar wind to be studied with much greater certainty than has been possible before. The STEREO HI

R. A. Fallows; A. R. Breen; G. D. Dorrian; I. Whittaker; M. Grande

2009-01-01

417

Scintillator Cosmic Ray Super Telescope  

NASA Astrophysics Data System (ADS)

The Scintillator Cosmic Ray Super Telescope (SciCRST) is a new experiment to detect solar neutrons, and also it is expected to work as a muon and cosmic ray detector. The SciCRST consist of 14,848 plastic scintillator bars, and it will be installed at the top of Sierra Negra volcano, Mexico, 4580 m.a.s.l. We use a prototype, called as miniSciBar, to test the hardware and software of the final experiment. In this paper, we present the status and details of the experiment, and results of the prototype.

González, L. X.; Valdés-Galicia, J. F.; Matsubara, Y.; Nagai, Y.; Itow, Y.; Sako, T.; López, D.; Mitsuka, G.; Munakata, K.; Kato, C.; Yasue, S.; Kosai, M.; Tsurusashi, M.; Nakamo, Y.; Shibata, S.; Takamaru, H.; Kojima, H.; Tsuchiya, H.; Watanabe, K.; Koi, T.; Fragoso, E.; Hurtado, A.; Musalem, O.

2013-04-01

418

Radio tracking system  

Microsoft Academic Search

The principles and techniques of deep space radio tracking are described along with the uses of tracking data in navigation and radio science. Emphasis is placed on the measurement functions of radio tracking.

J. C. Breidenthal; T. A. Komarek

1982-01-01

419

Ionospheric scintillation effects on single frequency GPS  

Microsoft Academic Search

Ionospheric scintillation of Global Positioning System (GPS) signals threatens navigation and military operations by degrading performance or making GPS unavailable. Scintillation is particularly active within, although not limited to, a belt encircling the Earth within 20 degrees of the geomagnetic equator. As GPS applications and users increase, so does the potential for degraded precision and availability from scintillation. We examined

R. A. Steenburgh; C. G. Smithtro; K. M. Groves

2008-01-01

420

Characteristics of High Latitude Ionosphere Scintillations  

NASA Astrophysics Data System (ADS)

As we enter a new solar maximum period, global navigation satellite systems (GNSS) receivers, especially the ones operating in high latitude and equatorial regions, are facing an increasing threat from ionosphere scintillations. The increased solar activities, however, also offer a great opportunity to collect scintillation data to characterize scintillation signal parameters and ionosphere irregularities. While there are numerous GPS receivers deployed around the globe to monitor ionosphere scintillations, most of them are commercial receivers whose signal processing mechanisms are not designed to operate under ionosphere scintillation. As a result, they may distort scintillation signal parameters or lose lock of satellite signals under strong scintillations. Since 2008, we have established and continuously improved a unique GNSS receiver array at HAARP, Alaska. The array contains high ends commercial receivers and custom RF front ends which can be automatically triggered to collect high quality GPS and GLONASS satellite signals during controlled heating experiments and natural scintillation events. Custom designed receiver signal tracking algorithms aim to preserve true scintillation signatures are used to process the raw RF samples. Signal strength, carrier phase, and relative TEC measurements generated by the receiver array since its inception have been analyzed to characterize high latitude scintillation phenomena. Daily, seasonal, and solar events dependency of scintillation occurrence, spectral contents of scintillation activities, and plasma drifts derived from these measurements will be presented. These interesting results demonstrate the feasibility and effectiveness of our experimental data collection system in providing insightful details of ionosphere responses to active perturbations and natural disturbances.

Morton, Y.

2012-12-01

421

Composite scintillators for detection of ionizing radiation  

DOEpatents

Applicant's present invention is a composite scintillator having enhanced transparency for detecting ionizing radiation comprising a material having optical transparency wherein said material comprises nano-sized objects having a size in at least one dimension that is less than the wavelength of light emitted by the composite scintillator wherein the composite scintillator is designed to have selected properties suitable for a particular application.

Dai, Sheng (Knoxville, TN) [Knoxville, TN; Stephan, Andrew Curtis (Knoxville, TN) [Knoxville, TN; Brown, Suree S. (Knoxville, TN) [Knoxville, TN; Wallace, Steven A. (Knoxville, TN) [Knoxville, TN; Rondinone, Adam J [Knoxville, TN

2010-12-28

422

Synthesis of plastic scintillation microspheres: Evaluation of scintillators  

NASA Astrophysics Data System (ADS)

The use of plastic scintillation microspheres (PSm) appear to be an alternative to liquid scintillation for the quantification of alpha and beta emitters because it does not generate mixed wastes after the measurement (organic and radioactive). In addition to routine radionuclide determinations, PSm can be used for further applications, e.g. for usage in a continuous monitoring equipment, for measurements of samples with a high salt concentration and for an extractive scintillation support which permits the separation, pre-concentration and measurement of the radionuclides without additional steps of elution and sample preparation. However, only a few manufacturers provide PSm, and the low number of regular suppliers reduces its availability and restricts the compositions and sizes available. In this article, a synthesis method based on the extraction/evaporation methodology has been developed and successfully used for the synthesis of plastic scintillation microspheres. Seven different compositions of plastic scintillation microspheres have been synthesised; PSm1 with polystyrene, PSm2 with 2,5-Diphenyloxazol(PPO), PSm3 with p-terphenyl (pT), PSm4 with PPO and 1,4-bis(5-phenyloxazol-2-yl) (POPOP), PSm5 pT and (1,4-bis [2-methylstyryl] benzene) (Bis-MSB), PSm6 with PPO, POPOP and naphthalene and PSm7 with pT, Bis-MSB and naphthalene. The synthesised plastic scintillation microspheres have been characterised in terms of their morphology, detection capabilities and alpha/beta separation capacity. The microspheres had a median diameter of approximately 130 ?m. Maximum detection efficiency values were obtained for the PSm4 composition as follows 1.18% for 3H, 51.2% for 14C, 180.6% for 90Sr/90Y and 76.7% for 241Am. Values of the SQP(E) parameter were approximately 790 for PSm4 and PSm5. These values show that the synthesised PSm exhibit good scintillation properties and that the spectra are at channel numbers higher than in commercial PSm. Finally, the addition of naphthalene modifies the shape of the pulses produced by alpha and beta particles leading to better alpha/beta separation.

Santiago, L. M.; Bagán, H.; Tarancón, A.; Garcia, J. F.

2013-01-01

423

Scintillation Velocities of Five Millisecond Pulsars  

NASA Astrophysics Data System (ADS)

Millisecond pulsars differ from normal pulsars in their mode of origin and their properties. They are thought to be born either through binary interaction or through accretion-induced collapse (AIC) of white dwarf stars. Several theoretical considerations suggest that these different mechanisms for the origin of millisecond pulsars would lead to different distributions of the space velocities of millisecond pulsars. Therefore, it is important to estimate the average space velocity of millisecond pulsars and compare it with that of normal pulsars. Here we present transverse velocity estimates of five millisecond pulsars obtained from interstellar scintillation observations, carried out with the Ooty Radio Telescope (ORT) at 327 MHz. For the pulsars J0437-4715, B1257+12, B1534+12, J1730-2304, and J2145-0750 we obtain velocity estimates of 231, 225, 191, 56, and 113 km s-1, respectively. The average velocity for these is much smaller than that of the normal pulsars and larger than that expected from the AIC process. Present velocity estimates are closer to other recent measurements of millisecond pulsars.

Gothoskar, Pradeep; Gupta, Yashwant

2000-03-01

424

Ship detection in heavy sea clutter echoes and man-made radio noise environment for an on-shore HF ground wave frequency agile radar  

Microsoft Academic Search

The spectral characteristics of sea clutter echoes and man-made noise disturbance in the HF band are analyzed. A new spectral method for ship detection in heavy sea clutter and man-made noise environment by an onshore ground wave radar is introduced. A T-R cell averaging detector with the assistance of a spectrum monitoring system operates on a frequency agile mode, and

Xiaolin Qiao; Yongtan Liu

1990-01-01

425

Submillimeter receivers for radio astronomy  

Microsoft Academic Search

The state of development of receivers for submillimeter-wave radio astronomy is reviewed. Bolometers for continuum observation, hot-electron mixer receivers for narrowband spectral line observation, and heterodyne receivers, both Schottky diode and superconducting tunnel junction, are presented. At the lower frequency end of the submillimeter band, standard waveguide techniques, scaled from millimeter wavelengths, prevail. At wavelengths shorter than about 0.5 mm,

Raymond Blundell; CHEUK-YU EDWARD TONG

1992-01-01

426

Radio plasma imager simulations and measurements  

Microsoft Academic Search

The Radio Plasma Imager (RPI) will be the first-of-its kind instrument designed to use radio wave sounding techniques to perform repetitive remote sensing measurements of electron number density (Ne) structures and the dynamics of the magnetosphere and plasmasphere. RPI will fly on the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) mission to be launched early in the year 2000. The design

J. L. Green; R. F. Benson; S. F. Fung; W. W. L. Taylor; S. A. Boardsen; B. W. Reinisch; D. M. Haines; K. Bibl; G. Cheney; I. A. Galkin; X. Huang; S. H. Myers; G. S. Sales; J.-L. Bougeret; R. Manning; N. Meyer-Vernet; M. Moncuquet; D. L. Carpenter; D. L. Gallagher; P. H. Reiff

2000-01-01

427

Japanese radio astronomy - past, present, and future.  

NASA Astrophysics Data System (ADS)

The past, present and future of radio astronomy in Japan are described from the author's personal view point. The radio astronomy in Japan is quickly growing in terms of the telescope size, the budget scale, and the total number of researchers in the country. The status of the major future projects such as VSOP, VERA, LMSA, and the submillimeter-wave telescope at Mt.Fuji is reviewed.

Deguchi, S.

1995-06-01

428

Boron Doped Plastic Scintillator Efficiency  

NASA Astrophysics Data System (ADS)

This talk will describe the progress made in an interdisciplinary development project aimed at cost-effective, neutron sensitive, plastic scintillator. Colorado School of Mines researchers with backgrounds in Physics, Chemistry, and Chemical Engineering have worked on the incorporation of ^10B in plastics through extrusion. First results on transparent samples using fluorescent spectroscopy and beta excitation will be presented.

Mahl, Adam; Chouinard-Dussault, Pascale; Pecinovsky, Cory; Potter, Andrew; Remedes, Tyler; Dorgan, John; Greife, Uwe

2013-04-01

429

A Solid State Scintillation Detector  

Microsoft Academic Search

Efforts to substitute a solid state device for the usual photomultiplier of a scintillation type nuclear detector led to the photoconductive cell. Although extremely sensitive, cadmium sulfide responds slowly to low levels of light, and a technique providing improvement over several orders of magnitude failed to achieve measurement of individual pulses. In an integrating application, however, such a method makes

George E. Wilcox

1967-01-01

430

Time response of plastic scintillators  

Microsoft Academic Search

Time-response characteristics of eight commercial plastic scintillators ; have been studied. Samples were excited by 50 ps electron or bremsstrahlung ; pulses. Sampling techniques were used to record the signal from a fast vacuum ; photodiode. Effects of surface preparation on time response were studied. The ; observed fwhm (in ns) for the three fastest plastics was 1.5, 2.0, and

P. B. Lyons; J. Stevens

1974-01-01

431

Radiation damage of plastic scintillators  

Microsoft Academic Search

Degradation and annealing mechanisms in polystyrene were studied in order to account for the losses in transmittance and light yield observed in polystyrene-based plastic scintillators. Special emphasis was put on irradiations in oxygen and on the oxygen annealing process. These experiments indicated that: (a) irradiations in which oxygen was continuously available throughout the bulk of the polystyrene sample were the

A. D. Bross; A. Pla-Dalmau

1992-01-01

432

Cerium doped elpasolite halide scintillators.  

SciTech Connect

Low-cost, high-performance gamma-ray spectrometers are urgently needed for proliferation detection and homeland security. The cost and availability of large scintillators used in the spectrometer generally hinge on their mechanical property and crystal symmetry. Low symmetry, intrinsically brittle crystals, such as these emerging lanthanide halide scintillators, are particularly difficult to grow in large sizes due to the development of large anisotropic thermomechanical stresses during solidification process. Isotropic cubic scintillators, such as alkali halides, while affordable and can be produced in large sizes, are poor spectrometers due to severe nonproportional response and modest light yield. This work investigates and compares four new elpasolite based lanthanide halides, including Cs2LiLaBr6, Cs2NaLaBr6, Cs2LiLaI6, and Cs2NaLaI6, in terms of their crystal symmetry, characteristics of photoluminescence and optical quantum efficiency. The mechanical property and thermal expansion behavior of the cubic Cs2LiLaBr6 will be reported. The isotropic nature of this material has potential for scaled-up crystal growth, as well as the possibility of low-cost polycrystalline ceramic processing. In addition, the proportional response with gamma-ray energy of directionally solidified Cs2LiLaBr6 will be compared with workhorse alkali halide scintillators. The processing challenges associated with hot forged polycrystalline elpasolite based lanthanide halides will also be discussed.

Doty, F. Patrick (Sandia National Laboratories, Livermore, CA); Shah, Kanai Subodhbhai (Radiation Monitoring Devices, Watertown, MA); Noda, Frank T.; Yang, Pin; Zhou, Xiao Wang (Sandia National Laboratories, Livermore, CA)

2010-05-01

433

SNO+ Scintillator Purification and Assay  

SciTech Connect

We describe the R and D on the scintillator purification and assay methods and technology for the SNO+ neutrino and double-beta decay experiment. The SNO+ experiment is a replacement of the SNO heavy water with liquid scintillator comprised of 2 g/L PPO in linear alkylbenzene (LAB). During filling the LAB will be transported underground by rail car and purified by multi-stage distillation and steam stripping at a flow rate of 19 LPM. While the detector is operational the scintillator can be recirculated at 150 LPM (full detector volume in 4 days) to provide repurification as necessary by either water extraction (for Ra, K, Bi) or by functional metal scavenger columns (for Pb, Ra, Bi, Ac, Th) followed by steam stripping to remove noble gases and oxygen (Rn, O{sub 2}, Kr, Ar). The metal scavenger columns also provide a method for scintillator assay for ex-situ measurement of the U and Th chain radioactivity. We have developed ''natural'' radioactive spikes of Pb and Ra in LAB and use these for purification testing. Lastly, we present the planned operating modes and purification strategies and the plant specifications and design.

Ford, R.; Vazquez-Jauregui, E. [SNOLAB, Creighton Mine, Lively, P3Y 1N2 (Canada); Chen, M. [Department of Physics, Queen's University, Kingston, K7L 3N6 (Canada); Chkvorets, O.; Hallman, D. [Department of Physics, Laurentian University, Sudbury, P3E 2C6 (Canada)

2011-04-27

434

Method of making a scintillator waveguide  

DOEpatents

The present invention is an apparatus for detecting ionizing radiation, having: a waveguide having a first end and a second end, the waveguide formed of a scintillator material wherein the therapeutic ionizing radiation isotropically generates scintillation light signals within the waveguide. This apparatus provides a measure of radiation dose. The apparatus may be modified to permit making a measure of location of radiation dose. Specifically, the scintillation material is segmented into a plurality of segments; and a connecting cable for each of the plurality of segments is used for conducting scintillation signals to a scintillation detector.

Bliss, Mary (West Richland, WA); Craig, Richard A. (West Richland, WA); Reeder, Paul L. (Richland, WA)

2000-01-01

435

Extruded plastic scintillator for MINERvA  

SciTech Connect

An extrusion line has recently been installed at Fermilab in collaboration with NICADD (Northern Illinois Center for Accelerator and Detector Development). This new facility will serve to further develop and improve extruded plastic scintillator. Since polystyrene is widely used in the consumer industry, the logical path was to investigate the extrusion of commercial-grade polystyrene pellets with dopants to yield high quality plastic scintillator. The D0 and MINOS experiments are already using extruded scintillator strips in their detectors. A new experiment at Fermilab is pursuing the use of extruded plastic scintillator. A new plastic scintillator strip is being tested and its properties characterized. The initial results are presented here.

Pla-Dalmau, Anna; Bross, Alan D.; /Fermilab; Rykalin, Victor V.; Wood, Brian M.; /NICADD, DeKalb

2005-11-01

436

AM Radio Ionosphere Station: Teacher's Guide  

NSDL National Science Digital Library

In this activity students will monitor the ionosphere by using an amplitude modulated (AM) radio to track solar storms and other changes in ionosphere reflectivity. They will discover that above the earth's surface a layer of charged particles called the ionosphere is capable of reflecting radio waves and that the reflectivity properties of the ionosphere can be changed dramatically by solar activity. In order to detect and study some of these changes, students will use the