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1

Radio wave scintillations at equatorial regions  

NASA Technical Reports Server (NTRS)

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

Poularikas, A. D.

1972-01-01

2

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

Microsoft Academic Search

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

John K. Harmon; William A. Coles

2005-01-01

3

Forecasting ionospheric space weather with applications to satellite drag and radio wave communications and scintillation  

NASA Astrophysics Data System (ADS)

The development of quantitative models that describe physical processes from the solar corona to the Earth’s upper atmosphere opens the possibility of numerical space weather prediction with a lead-time of a few days. Forecasting solar wind-driven variability in the ionosphere and thermosphere poses especially stringent tests of our scientific understanding and modeling capabilities, in particular of coupling processes to regions above and below. We will describe our work with community models to develop upper atmosphere forecasts starting with the solar wind driver. A number of phenomena are relevant, including high latitude energy deposition, its impact on global thermospheric circulation patterns and composition, and global electrodynamics. Improved scientific understanding of this sun to Earth interaction ultimately leads to practical benefits. We will focus on two ways the upper atmosphere affects life on Earth: by changing satellite orbits, and by interfering with long-range radio communications. Challenges in forecasting these impacts will be addressed, with a particular emphasis on the physical bases for the impacts, and how they connect upstream to the sun and the heliosphere.

Mannucci, Anthony J.; Tsurutani, Bruce T.; Verkhoglyadova, Olga P.; Meng, Xing; Pi, Xiaoqing; Kuang, Da; Wang, Chunming; Rosen, Gary; Ridley, Aaron; Lynch, Erin; Sharma, Surja; Manchester, Ward B.; van der Holst, Bart

2015-04-01

4

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

5

Radio wave.  

PubMed

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

Elkin, V

1992-01-01

6

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

NASA Technical Reports Server (NTRS)

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

Hinson, D. P.

1983-01-01

7

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.

8

Riding the Radio Waves  

NSDL National Science Digital Library

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

2014-09-18

9

The Origin of Radio Scintillation In the Local Interstellar Medium  

E-print Network

We study three quasar radio sources (B1257-326, B1519-273, and J1819+385) that show large amplitude intraday and annual scintillation variability produced by the Earth's motion relative to turbulent-scattering screens located within a few parsecs of the Sun. We find that the lines of sight to these sources pass through the edges of partially ionized warm interstellar clouds where two or more clouds may interact. From the gas flow vectors of these clouds, we find that the relative radial and transverse velocities of these clouds are large and could generate the turbulence that is responsible for the observed scintillation. For all three sight lines the flow velocities of nearby warm local interstellar clouds are consistent with the fits to the transverse flows of the radio scintillation signals.

Jeffrey L. Linsky; Barney J. Rickett; Seth Redfield

2007-11-07

10

Multiple phase screen modeling of ionospheric scintillation along radio occultation raypaths  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

11

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

12

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

13

Interplanetary scintillation observations with the Cocoa Cross radio telescope  

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

14

Elements of Radio Waves  

E-print Network

We present a summary of the basic properties of the radio wave generation, propagation and reception, with a special attention to the gigahertz bandwidth region which is of interest for wireless sensor networks. We also present some measurement results which use the so-called RSSI indicator in order to track how the field strength varies with position and distance of the transceivers. We hope the paper may be useful to anyone who looks for a quick review of the fundamentals of electromagnetic theory with application to antennas.

Frank G. Borg; Ismo Hakala; Jukka Määttälä

2007-12-24

15

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

16

Radio Waves and the Ionosphere  

NSDL National Science Digital Library

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

Susan Higley

17

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

NASA Astrophysics Data System (ADS)

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

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

2007-05-01

18

INTERPLANETARY SCINTILLATION RADIO SOURCES DETECTED WITH THE MEXICAN ARRAY RADIO TELESCOPE (MEXART)  

NASA Astrophysics Data System (ADS)

The Mexican Array Radio Telescope (MEXART) has an antenna composed by 4096 full-wavelength dipoles, covering about 9800 square meters. The instrument is primary devoted to carry out observations of compact stelar radio sources presenting Interplanetary Scintillation (IPS) at 140 MHz. The IPS technique is a very useful tool to perform observations of large-scale solar wind density disturbances in the inner heliosphere at heliocentric ranges where no other instruments can cover. These observations can help to track the evolution of CMEs and shocks in the interplanetary medium. We present the first catalog of IPS sources detected with the MEXART. We show the power spectrum analysis to obtain information of solar wind velocity and density.

Mejia Ambriz, J. C.; Villanueva-Hernandez, P.; Gonzalez-Esparza, A.; Aguilar-Rodriguez, E.; Andrade-Mascote, E.; Carrillo-Vargas, A.

2009-12-01

19

Ionospheric scintillations at Guilin detected by GPS ground-based and radio occultation observations  

NASA Astrophysics Data System (ADS)

The occurrence of ionospheric scintillations with S4 ? 0.2 was studied using GPS measurements at Guilin, China (25.29°N, 110.33°E; geomagnetic: 15.04°N, 181.98°E), a station located near the northern crest of the equatorial anomaly. The results are presented for data collected from January 2009 to March 2010. The results show that nighttime amplitude scintillations only took place in February and March of the considered years, while daytime amplitude scintillations occurred in August and December of 2009. Nighttime amplitude scintillations, observed in the south of Guilin, always occurred with phase scintillations, TEC (Total Electron Content) depletions, and ROT (Rate Of change of TEC) fluctuations. However, TEC depletions and ROT fluctuations were weak during daytime amplitude scintillations, and daytime amplitude scintillations always took place simultaneously for most of the GPS satellites which appeared over Guilin in different azimuth directions. Ground-based GPS scintillation/TEC observations recorded at Guilin and signal-to-noise-ratio (SNR) measurements obtained from GPS-COSMIC radio occultation indicate that nighttime and daytime scintillations are very likely caused by ionospheric F region irregularities and sporadic E, respectively. Moreover, strong daytime amplitude scintillations may be associated with the plasma density enhancements in ionospheric E region caused by the Perseid and Geminid meteor shower activities.

Zou, Yuhua

2011-03-01

20

Global analysis of scintillation variance: Indication of gravity wave breaking in the polar winter upper stratosphere  

Microsoft Academic Search

Stellar scintillations observed through the Earth atmosphere are caused by air density irregularities generated mainly by internal gravity waves and turbulence. We present global analysis of scintillation variance in two seasons of year 2003 based on GOMOS\\/Envisat fast photometer measurements. Scintillation variance can serve as a qualitative indicator of intensity of small-scale processes in the stratosphere. Strong increase of scintillation

V. F. Sofieva; E. Kyrölä; S. Hassinen; L. Backman; J. Tamminen; A. Seppälä; L. Thölix; A. S. Gurvich; V. Kan; F. Dalaudier; A. Hauchecorne; J.-L. Bertaux; D. Fussen; F. Vanhellemont; O. Fanton d' Andon; G. Barrot; A. Mangin; M. Guirlet; T. Fehr; P. Snoeij; L. Saavedra; R. Koopman; R. Fraisse

2007-01-01

21

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

NASA Astrophysics Data System (ADS)

Remote sensing of radio signals from low-Earth orbiting (LEO) satellites provides a wealth of information on the presence and location of disturbances in the equatorial ionosphere which result in scintillations. Results will be presented emphasizing the statistical improvements provided to existing ionospheric specification models with the assimilation of measurements from the Coherent Electromagnetic Radio Tomography (CERTO) beacon onboard the Communication/Navigation Outage Forecasting System satellite. Spatial and temporal enhancements to regional specifications from the Scintillation Network Decision Aid (SCINDA) model are analyzed in this study carried out under solar minimum conditions in the Pacific sector. In a subset of the study covering 68 days beginning at the peak of the scintillation season, more than 60% of the events in which scintillation was observed in the C/NOFS CERTO beacon data occurred during the absence of scintillation on SCINDA VHF and GPS receivers. Oftentimes, scintillation detected on the LEO beacon signal could be directly correlated with activity later observed on a SCINDA VHF link to a geosynchronous satellite providing a forecast capability of up to two hours. Numerous cases were noted, however, in which disturbances measured during C/NOFS overflights were not observed at all on SCINDA links due to geometry constraints. Conclusions from this investigation strongly support the inclusion of radio beacon data into regional ionospheric scintillation specification and forecast models.

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

2010-12-01

22

The Cassini Radio and Plasma Wave Investigation  

Microsoft Academic Search

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

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

2004-01-01

23

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

24

ELF and VLF radio waves  

NASA Astrophysics Data System (ADS)

This review covers developments in ELF and VLF radio-wave propagation research over the last 50 years of the Journal of Atmospheric and Solar-Terrestrial Physics. A review of such a large field, over such a long period, cannot be fully comprehensive and the authors have therefore covered important areas which have they themselves have found interesting. The survey begins with a review of work on natural and man made sources of ELF and VLF radiation. This is followed by sections on experimental and theoretical studies of unperturbed (ambient) ELF and VLF radio propagation. Schumann resonance research, which is currently undergoing a renaissance, is then reviewed. A review of research into transient perturbations of ELF and VLF propagation follows, extending from the early work on nuclear explosions up to the current work on sprites. The review concludes with a brief summary of the VLF navigation systems of the USSR and USA, (Alpha and Omega) whose development and life-span covered most of the last 50 years.

Barr, R.; Jones, D. L.; Rodger, C. J.

2000-11-01

25

Interplanetary and Ionosphere Scintillation Monitoring of Radio Sources Ensemble at the Solar Activity Minimum  

NASA Astrophysics Data System (ADS)

Results are presented of twenty-four-hour interplanetary and ionosphere scintillation monitoring obtained in Pushchino Radioastronomy Observatory during three observation series: between 18 November and 30 December 2006; between 11 June and 18 June 2007; between 20 October and 4 November 2008. Observations were carried out simultaneously in 16 beams of the radio telescope BSA LPI (Big Scanning Array of Lebedev Physical Institute) at the frequency 111 MHz. All the sources with scintillating flux greater than 0.2 Jy were recorded in the range of declination from +3° to +12°40 by observations in the years 2006, 2008 and from 21° to 28° in the year 2007. The values of radio source flux fluctuation temporal structure functions were measured at the temporal lags of 0.1 s, 1 s and 10 s, which characterize noise, interplanetary scintillations and ionosphere scintillations, respectively. About 1000 scintillating radio sources were observed every day. The number of sources N ( ? IPS? ? IPS,0) with scintillating flux ? IPS greater than the given value ? IPS,0 in the sky area with sizes 8° in declination and 0.5 hours in right ascension was used as the parameter describing turbulent interplanetary plasma. This parameter is shown to be proportional to the mean scintillation index of the radio source statistical ensemble in the given sky area. Similarly, the parameter N ( ? IONS? ? IONS,0) was introduced for a description of the turbulent ionosphere. The mean twenty-four-hour temporal dependence of the scintillation index is found. Weak day-to-day variations of the scintillation index were observed. In general, interplanetary plasma, as well as the ionosphere, was in a quiet state during the observation periods. Unusually a weak dependence of scintillation index on the position of the sources relative to the Sun was observed in the year 2008 at very deep solar activity minimum. Such a weak dependence is explained by a strong elongation of the turbulence level spatial distribution along the solar equatorial plane during a very deep minimum of solar activity.

Shishov, V. I.; Tyul'Bashev, S. A.; Chashei, I. V.; Subaev, I. A.; Lapaev, K. A.

2010-08-01

26

Radio wave propagation and acoustic sounding  

NASA Astrophysics Data System (ADS)

Radio wave propagation of the decimetric and centimetric waves depends to a large extent on the boundary layer meteorological conditions which give rise to severe fadings, very often due to multipath propagation. Sodar is one of the inexpensive remote sensing techniques which can be employed to probe the boundary layer structure. In the paper a historical perspective has been given of the simultaneously conducted studies on radio waves and sodar at various places. The radio meteorological information needed for propagation studies has been clearly spelt out and conditions of a ray path especially in the presence of a ducting layer have been defined as giving rise to fading or signal enhancement conditions. Finally the potential of the sodar studies to obtain information about the boundary layer phenomena has been stressed, clearly spelling out the use of acoustic sounding in radio wave propagation studies.

Singal, S. P.

27

Antenna Construction and Propagation of Radio Waves.  

ERIC Educational Resources Information Center

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

Marine Corps Inst., Washington, DC.

28

Radio Wave Propagation through a Medium Containing Electron Density Fluctuations Described by an Anisotropic Goldreich-Sridhar Spectrum  

Microsoft Academic Search

We study the propagation of radio waves through a medium possessing density fluctuations that are elongated along the ambient magnetic field and described by an anisotropic Goldreich-Sridhar power spectrum. We derive general formulae for the wave phase structure function Dphi, visibility, angular broadening, diffraction pattern length scales, and scintillation timescale for arbitrary distributions of turbulence along the line of sight

B. D. G. Chandran; D. C. Backer

2002-01-01

29

The Mexican Array Radio Telescope (MEXART). An Interplanetary Scintillation Array in Mexico in the IHY  

NASA Astrophysics Data System (ADS)

The Mexican Array Radio Telescope (MEXART) consists of a 64x64 (4096) full wavelength dipole antenna array, operating at 140 MHz, occupying 9,500 square meters (70 m x 140 m) to carry out interplanetary scintillation (IPS) observations. This is a dedicated radio array for IPS observations located in the state of Michoacan (350 km north-west from Mexico City, lat. 19° 48' N, long. 101° 41' W and 1964 m above sea level). The aim of this instrument is to track large-sclae solar wind disturbances propagating between the Sun and the Earth using the Interplanetary scintillation technique. We report the system testings, radio source measurements and the collaboration plans for the International Heliophysical Year 2007.

Gonzalez-Esparza, J. A.; Andrade, E.; Carrillo, A.; et al.

30

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

Microsoft Academic Search

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

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

1988-01-01

31

Wave-wave interactions in solar type III radio bursts  

SciTech Connect

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

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

2014-02-11

32

Wave-wave interactions in solar type III radio bursts  

NASA Astrophysics Data System (ADS)

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

Thejappa, G.; MacDowall, R. J.

2014-02-01

33

Information Content in Radio Waves: Student Investigations in Radio Science  

NASA Astrophysics Data System (ADS)

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

Jacobs, K.; Scaduto, T.

2013-12-01

34

Comparisons Between In-Situ Plasma Fluctuation and Radio Occultation Based Measures of Ionospheric Scintillation  

NASA Astrophysics Data System (ADS)

Ionospheric radio occultation (RO) and in-situ measurements of plasma density fluctuations provide two different approaches for inferring the presence or absence of ionospheric scintillation. The RO technique involves a direct measure of scintillation at L-band frequencies, but in a limb-viewing geometry that entails some uncertainty regarding the precise geolocation of the associated irregularity region or regions. Scintillation over a range of frequencies from UHF to L-band can be inferred from observation of the in-situ irregularity spectrum together with a set of modeling assumptions. The CORISS (C/NOFS Occultation Receiver for Ionospheric Sensing and Specification) and PLP (Planar Langmuir Probe) instruments on board the C/NOFS satellite provide a means to compare and contrast the two approaches in a rigorous manner. This presentation with report initial comparison results based on data collected during the 2008-2010 time frame.

Straus, P. R.; Roddy, P. A.; Bonito, N.

2010-12-01

35

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

36

A Review of Ionospheric Scintillation Models  

NASA Astrophysics Data System (ADS)

This is a general review of the existing climatological models of ionospheric radio scintillation for high and equatorial latitudes. Trans-ionospheric communication of radio waves from transmitter to user is affected by the ionosphere which is highly variable and dynamic in both time and space. Scintillation is the term given to irregular amplitude and phase fluctuations of the received signals and related to the electron density irregularities in the ionosphere. Key sources of ionospheric irregularities are plasma instabilities; every irregularities model is based on the theory of radio wave propagation in random media. It is important to understand scintillation phenomena and the approach of different theories. Therefore, we have briefly discussed the theories that are used to interpret ionospheric scintillation data. The global morphology of ionospheric scintillation is also discussed briefly. The most important (in our opinion) analytical and physical models of scintillation are reviewed here.

Priyadarshi, S.

2015-01-01

37

A Review of Ionospheric Scintillation Models  

NASA Astrophysics Data System (ADS)

This is a general review of the existing climatological models of ionospheric radio scintillation for high and equatorial latitudes. Trans-ionospheric communication of radio waves from transmitter to user is affected by the ionosphere which is highly variable and dynamic in both time and space. Scintillation is the term given to irregular amplitude and phase fluctuations of the received signals and related to the electron density irregularities in the ionosphere. Key sources of ionospheric irregularities are plasma instabilities; every irregularities model is based on the theory of radio wave propagation in random media. It is important to understand scintillation phenomena and the approach of different theories. Therefore, we have briefly discussed the theories that are used to interpret ionospheric scintillation data. The global morphology of ionospheric scintillation is also discussed briefly. The most important (in our opinion) analytical and physical models of scintillation are reviewed here.

Priyadarshi, S.

2015-03-01

38

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

39

Plasma distribution of Comet ISON (C/2012 S1) observed using the radio scintillation method  

E-print Network

We report the electron density in a plasma tail of Comet ISON (C/2012 S1) derived from interplanetary scintillation (IPS) observations during November 1--28, 2013. Comet ISON showed a well-developed plasma tail (longer than 2.98 x 10^{7} km) before its perihelion passage on November 28. We identified a radio source whose line-of-sight approached the ISON's plasma tail in the above period and obtained its IPS data using the Solar Wind Imaging Facility at 327 MHz. We used the Heliospheric Imager onboard the Solar-Terrestrial Relation Observatory to distinguish between the cometary tail and solar eruption origins of their enhanced scintillation. From our examinations, we confirmed three IPS enhancements of a radio source 1148-00 on November 13, 16, and 17, which could be attributed to the disturbance in the cometary tail. They showed no appreciable change of fluctuation power spectra during the occultation by the plasma tail of Comet ISON. We estimated the electron density in the ISON's plasma tail and found 84 ...

Iju, Tomoya; Tokumaru, Munetoshi; Fujiki, Ken'ichi

2014-01-01

40

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

Microsoft Academic Search

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

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

1980-01-01

41

Observations of Interplanetary Scintillation (IPS) Using the Mexican Array Radio Telescope (MEXART)  

NASA Astrophysics Data System (ADS)

The Mexican Array Radio Telescope (MEXART) consists of a 64×64 (4096) full-wavelength dipole antenna array, operating at 140 MHz, with a bandwidth of 2 MHz, occupying about 9660 square meters (69 m × 140 m) ( http://www.mexart.unam.mx ). This is a dedicated radio array for Interplanetary Scintillation (IPS) observations located at latitude 19°48'N, longitude 101°41'W. We characterize the performance of the system. We report the first IPS observations with the instrument, employing a Butler Matrix (BM) of 16×16 ports, fed by 16 east - west lines of 64 dipoles (1/4 of the total array). The BM displays a radiation pattern of 16 beams at different declinations (from -48, to +88 degrees). We present a list of 19 strong IPS radio sources (having at least 3 ? in power gain) detected by the instrument. We report the power spectral analysis procedure of the intensity fluctuations. The operation of MEXART will allow us a better coverage of solar wind disturbances, complementing the data provided by the other, previously built, instruments.

Mejia-Ambriz, J. C.; Villanueva-Hernandez, P.; Gonzalez-Esparza, J. A.; Aguilar-Rodriguez, E.; Jeyakumar, S.

2010-08-01

42

Radio-wave propagation for space communications systems  

NASA Technical Reports Server (NTRS)

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

Ippolito, L. J.

1981-01-01

43

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

Microsoft Academic Search

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

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

1986-01-01

44

Analysis of Gravity Waves from Radio Occultation Measurements  

E-print Network

Analysis of Gravity Waves from Radio Occultation Measurements Martin Lange and Christoph Jacobi occultation mea- surements. Due to the spherical symmetry assumption in the retrieval algorithm and the low that with radio occultation measurements more than 90% of the simulated wave spectrum can be resolved

45

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

PubMed

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

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

2006-10-01

46

Magnetospheric radio and plasma wave research - 1987-1990  

SciTech Connect

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

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

1991-01-01

47

WBMod assisted PLL GPS software receiver for mitigating scintillation affect in high latitude region  

Microsoft Academic Search

Ionospheric scintillation occurs for transionospheric radio waves propagating through random ionospheric irregularities, which affect the phase and\\/or amplitude observations made by the receiver. Generally, the scintillation induces excess carrier phase jitter in the phase lock loop (PLL) of the GPS receiver, and strong scintillation can cause a conventional PLL (ATAN [arctangent method], constant bandwidth Bn = 10 Hz) to lose

R. Tiwari; S. Skone; S. Tiwari; H. J. Strangeways

2011-01-01

48

WAVES: THE RADIO AND PLASMA WAVE INVESTIGATION ON THE WIND SPACECRAFT  

E-print Network

, of neural networks in real-time on board a scientificspacecraft to analyze data and command observationWAVES: THE RADIO AND PLASMA WAVE INVESTIGATION ON THE WIND SPACECRAFT J.-L. BOUGERET DESPA spacecraft will provide comprehensive mea- surements of the radio and plasma wave phenomena which occur

Christian, Eric

49

Type III radio bursts: STEREO/WAVES observations  

NASA Astrophysics Data System (ADS)

Type III radio bursts are the most intense interplanetary radio waves observed in the solar wind. Electrostatic Langmuir waves (produced by field-aligned beams of fast electrons connected with coronal mass ejections and/or solar flares) are triggers of the type III radio bursts. The two STEREO spacecraft provide us with unique stereoscopic observations of the Sun. The S/WAVES instruments (the HFR receivers) measure all components of the electric field in a frequency range from 125 kHz up to 1975 kHz. It allows us to investigate directions of the wave vectors and estimate apparent source sizes as well. In this paper the Singular Value Decomposition method has been used as an effective tool for multi-component wave analysis. A statistical study (based on 80 events) of goniopolarimetric properties of the type III radio bursts will be presented. We have investigated a spatial distribution of their sources. We have also studied the apparent source sizes.

Krupar, Vratislav; Maksimovic, Milan; Santolik, Ondrej; Cecconi, Baptiste

2010-05-01

50

BotEC: The Distance Radio Waves Have Traveled  

NSDL National Science Digital Library

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

Barb Tewksbury

51

Radio wave scattering in the outer heliosphere  

NASA Technical Reports Server (NTRS)

Current models for the 2-3 kHz emissions observed by the Voyager spacecraft in the outer heliosphere involve 2f(p) radiation generated near the termination shock or the heliopause. Radio wave scattering by solar wind density irregularities strongly affects observed sources of f(p) and 2f(p) emission in the inner heliosphere and the characteristics of astrophysical sources. In particular, the angular size, brightness temperature, and time variability of the source are strongly affected by scattering, thereby having major implications for the inferred size, energy budget, time variability, location, and nature of the source if scattering is ignored. This paper addresses whether scattering is important for interpreting the Voyager 2-3 kHz emissions. Quantitative calculations (with and without diffraction) are performed for the angular broadening of an outer heliospheric source as a function of path length, radiation frequency relative to f(p) and the spectrum of density irregularities. The effects of scattering in both the solar wind and the heliosheath are considered. Predictions for radial gradients in the source's apparent angular size and in the source's modulation index are presented. The calculations are compared with observations and the results discussed. First estimates suggest that scattering plausibly dominates the observed source size. The observed trend in modulation index with heliocentric distance is consistent with scattering being important and the source being in the outer heliosphere. Additional arguments for scattering being important are summarized.

Cairns, Iver H.

1995-01-01

52

Equatorial GPS ionospheric scintillations over Kototabang, Indonesia and their relation to atmospheric waves from below  

NASA Astrophysics Data System (ADS)

Using Global Positioning System (GPS) satellites, we have been conducting equatorial ionospheric scintillation observations at Kototabang, Indonesia since January 2003. Scintillations caused by equatorial plasma bubbles appear between 2000 and 0100 LT in equinoctial months with a seasonal asymmetry, and their activity decreases with decreasing solar activity. A comparison between scintillation index ( S 4) and Earth's brightness temperature ( T bb) variations suggests that the scintillation activity can be related to tropospheric disturbances over the Indian Ocean to the west of Kototabang. To understand better the reasons of day-to-day variability of S 4, we analyze S 4, T bband lower thermospheric neutral wind () data. The results show that S 4 fluctuates with periods of about 2.5, 5, 8, 14 and 25 days, possibly due to atmospheric waves from below and that similar periods are also found in the T bband variations. Using a general circulation model, we made numerical simulations to determine the behavior of neutral wind in the equatorial thermosphere. The results indicate the following: (1) 2- to 20-day waves dissipate rapidly above about an altitude of 125 km, and 0.5- to 3-hour waves become predominant above 100 km, (2) zonal winds above 200 km altitude are, on the whole, eastward during sunset-sunrise, (3) zonal wind patterns due to short-period (1-4 h) atmospheric gravity waves (AGWs) above 120 km altitude change day by day, exhibit wavy structures with scale lengths of about 30-1000 km and, as a whole, move eastward at about 100-1 while changing patterns over time. These simulations suggest that the Rayleigh-Taylor instability responsible for plasma bubble generation can be seeded by AGWs with short periods of about 0.5-3 h, and that background conditions necessary for this instability are modulated by planetary-scale atmospheric waves propagating up to an altitude of about 120 km from below.

Ogawa, Tadahiko; Miyoshi, Yasunobu; Otsuka, Yuichi; Nakamura, Takuji; Shiokawa, Kazuo

2009-04-01

53

Plasma and radio waves from Neptune: Source mechanisms and propagation  

NASA Technical Reports Server (NTRS)

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

Wong, H. K.

1994-01-01

54

GALILEO RADIO AND PLASMA WAVE OBSERVATIONS AT JUPITER: AN INVITED  

E-print Network

GALILEO RADIO AND PLASMA WAVE OBSERVATIONS AT JUPITER: AN INVITED OVERVIEW D. A. Gurnett , W. S. Kurth , A. Roux , C. F. Kennel and S. J. Bolton§ On 7 December 1995 the Galileo spacecraft made a close of the immediate vicinity of Io. The Galileo plasma wave investigation found that the torus was a factor of two

Gurnett, Donald A.

55

SOHO and radio observations of a CME shock wave  

Microsoft Academic Search

A 1200 kms-1 Coronal Mass Ejection was observed with the SOHO instruments EIT, LASCO and UVCS on June 11, 1998. Simultaneously, Type II radio bursts were observed with the WAVES experiment aboard the Wind spacecraft at 4 MHz and by ground-based instruments at metric wavelengths. The density in the shock wave implied by the higher frequency is close to that

John C. Raymond; Barbara J. Thompson; O. C. St. Cyr; Nat Gopalswamy; S. Kahler; M. Kaiser; A. Lara; A. Ciaravella; M. Romoli; R. O'Neal

2000-01-01

56

Stabilization of magnetohydrodynamic modes by applied radio-frequency waves  

Microsoft Academic Search

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

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

1986-01-01

57

Stabilization of magnetohydrodynamic modes by applied radio-frequency waves  

Microsoft Academic Search

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

D. A. D’Ippolito; J. R. Myra

1986-01-01

58

Roles Played by Electrostatic Waves in Producing Radio Emissions  

NASA Technical Reports Server (NTRS)

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

Cairns, Iver H.

2000-01-01

59

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

60

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

SciTech Connect

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

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

2009-05-15

61

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

E-print Network

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

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

2008-12-13

62

Embracing the Wave: Using the Very Small Radio Telescope to Teach Students about Radio Astronomy  

NASA Astrophysics Data System (ADS)

The Very Small Radio Telescope (VSRT) is a low-cost educational tool appropriate for laboratory demonstrations of the nature of radio waves and the principles of interferometry for use in both high school and undergraduate physics/astronomy classes. The system consists of small direct broadcast antenna dishes and other commercially available parts and can be assembled for under $500. Complete teaching units have been developed and tested by high school physics teachers to demonstrate radio wave transmission and exponential absorption though materials (Beer's law), the polarization of electromagnetic waves (Malus' law), the inverse square law, and interferometry. These units can be used to explore the properties of electromagnetic waves, including similarities and differences between radio and visible light, while challenging students' misconceptions about a wavelength regime that is important to both astronomy and everyday life. In addition, the VSRT can be used as a radio astronomical interferometer to measure the diameter of the Sun at 12 GHz. Full details, including a parts list, comprehensive assembly instructions, informational memos, teaching units, software, and conformance to national and Massachusetts educational standards, are available on the web at http://www.haystack.mit.edu/edu/undergrad/VSRT/index.html . Development of the VSRT at MIT Haystack Observatory is made possible through funding provided by the National Science Foundation.

Fish, Vincent L.; Needles, M. M.; Rogers, A. E. E.; Doherty, M.; Minnigh, S.; Arndt, M. B.; Pratap, P.

2010-01-01

63

Characteristics of layers, waves and turbulence in the atmosphere and ionosphere as estimated by GPS space radio-holography  

NASA Astrophysics Data System (ADS)

The spatial, seasonal and geographical distrubutions of the intensity of layers, turbulence and internal waves at different altitudes in the atmosphere and ionosphere of the Earth are presented. The results have been obtained on the base of locality principle using a new phase acceleration-intensity method for analysis of the GPS radio occultation signals. This methodology has been applied to mesearements of the inclination and altitude of ionospheric layers. Obtained information has been used for estimation of the front orientation, internal frequency and phase speed of the internal waves in the ionosphere and neutral atmosphere. A new index of the ionospheric activity as measured from the phase of radio waves passed through the ionosphere is introduced and its high correlation with S4 scintillation index is established. This correlation indicates the significant influence of ionospheric layers on variations of characteristics of radio waves in transionospheric communication links. Specially for the troposphere the geographical distribution of the weak total absorption (about of 1-2 db) of the radio waves at GPS frequencies in the Earth atmosphere corresponding to influence of the oxygen and water vapor in the troposphere is measured with accuracy better than 0.1 db. Obtained results expanded the applicable domain of the GPS space radio-holography for global investigation of the natural processes in the atmosphere and ionosphere as function of solar activity and space weather effects. The new phase acceleration-intensity method is also a basic tool which can be applied for data analysis of future planetary radio occultation missions

Pavelyev, Alexander; Gubenko, Vladimir; Matyugov, Stanislav; Pavelyev, Alexey

64

A torsional wave model for solar radio pulsations  

Microsoft Academic Search

One of the widely accepted models for solar radio pulsations invokes radial oscillations of a magnetic flux tube. Due to acoustic, radiative damping, this theory does not easily explain the long length of the pulse trains, the large modulation depths or the great stability of the pulse repetition rate often observed. Torsional waves efficiently modulate synchrotron emission, and since they

K. F. Tapping

1983-01-01

65

Modeling and scientific application of scintillation results  

Microsoft Academic Search

At many locations around the world, observations have been made of ionospherically imposed radio wave scintillations. There is, therefore, a need for an orderly means to assemble the data. Computer-based models intended for application to transionospheric communication systems provide such a scientifically useful repository of information. The present study is concerned with an attempt to illustrate such models with the

E. J. Fremouw; J. A. Secan

1984-01-01

66

Electromagnetic Waves - From X Rays to Radio Waves: The Energy of the Universe  

NASA Astrophysics Data System (ADS)

This book explores the world of electromagnetic waves ranging from radio frequencies to X-rays. The first part is physical and describes all the causes that produce electromagnetic waves in our world. The second part is astronomical and describes how electromagnetic waves are produced by astrophysical objects of different kinds, ranging from low-energy stars to high-energy objects such as pulsars and magnetars. The third part is devoted to some considerations concerning cosmology and the birth of electromagnetic waves.

Teodorani, M.

2008-09-01

67

Tracking the CME-driven Shock Wave on 2012 March 5 and Radio Triangulation of Associated Radio Emission  

NASA Astrophysics Data System (ADS)

We present a multiwavelength study of the 2012 March 5 solar eruptive event, with an emphasis on the radio triangulation of the associated radio bursts. The main points of the study are reconstruction of the propagation of shock waves driven by coronal mass ejections (CMEs) using radio observations and finding the relative positions of the CME, the CME-driven shock wave, and its radio signatures. For the first time, radio triangulation is applied to different types of radio bursts in the same event and performed in a detailed way using goniopolarimetric observations from STEREO/Waves and WIND/Waves spacecraft. The event on 2012 March 5 was associated with a X1.1 flare from the NOAA AR 1429 situated near the northeast limb, accompanied by a full halo CME and a radio event comprising long-lasting interplanetary type II radio bursts. The results of the three-dimensional reconstruction of the CME (using SOHO/LASCO, STEREO COR, and HI observations), and modeling with the ENLIL cone model suggest that the CME-driven shock wave arrived at 1 AU at about 12:00 UT on March 7 (as observed by SOHO/CELIAS). The results of radio triangulation show that the source of the type II radio burst was situated on the southern flank of the CME. We suggest that the interaction of the shock wave and a nearby coronal streamer resulted in the interplanetary type II radio emission.

Magdaleni?, J.; Marqué, C.; Krupar, V.; Mierla, M.; Zhukov, A. N.; Rodriguez, L.; Maksimovi?, M.; Cecconi, B.

2014-08-01

68

Energy coupling channels and effecting mechanism of continuous wave irradiation to radio fuze  

Microsoft Academic Search

Based on introducing experiment equipment and method the irradiation effects experiments of continuous wave to radio fuze are studied Analyzing the experiment results indicate that the coupling channels of continuous wave to radio fuze are the antenna and shell body. The effecting mechanism is that the energy of continuous wave couples into radio fuze via the antenna and shell body,

Zhiqiang Fei; Guanghui Wei; Lifei Geng; Fu Li

2009-01-01

69

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

E-print Network

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

Bennun, Alfred

2012-01-01

70

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

E-print Network

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

Alfred Bennun

2012-08-16

71

THE ORIGIN OF RADIO SCINTILLATION IN THE LOCAL INTERSTELLAR MEDIUM Jeffrey L. Linsky,1  

E-print Network

and annual scintillation variability produced by the Earth's motion relative to turbulent-scattering screens flow vectors of these clouds, we find that the relative radial and transverse velocities. For all three sight lines the flow velocities of nearby warm local interstellar clouds are consistent

Royer, Dana

72

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

Microsoft Academic Search

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

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

1995-01-01

73

Transpolar Propagation of Long Radio Waves  

Microsoft Academic Search

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

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

1972-01-01

74

Remote personal health monitoring with radio waves  

NASA Astrophysics Data System (ADS)

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

Nguyen, Andrew

2008-03-01

75

The stationary phase point method for transitional scattering: diffractive radio scintillation for pulsar  

E-print Network

The stationary phase point (SPP) method in one-dimensional case is introduced to treat the diffractive scintillation. From weak scattering, where the SPP number N=1, to strong scattering (N$\\gg$1), via transitional scattering regime (N$\\sim$2,3), we find that the modulation index of intensity experiences the monotonically increasing from 0 to 1 with the scattering strength, characterized by the ratio of Fresnel scale $\\rf$ to diffractive scale $\\rdiff$.

C. M. Zhang

2007-01-22

76

Modeling of ionospheric scintillation at low-latitude  

NASA Astrophysics Data System (ADS)

The presence and movement of plasma density fluctuations in the F-region of the ionosphere are studied by monitoring phase and amplitude of radio waves propagating through the region. In this paper, we have used weak scattering theory and assumed the plasma density fluctuations to behave like phase changing diffraction screen. Appropriate relations for scintillation index S4, and phase variance ?? are derived and computed for different parameters of the plasma density irregularities of the ionosphere. SROSS-C2 satellite in situ measurements of plasma density fluctuations, which provide direct information about the structure and morphology of irregularities that are responsible for scintillation of radio waves, were used first time to develop a scintillation model for low latitude. It is observed that the scintillation index S4 and phase variance ?? depends on the strength of the plasma turbulence. Finally, the results obtained from modeling are compared and discussed with the available recent results.

Patel, K.; Singh, Ashutosh K.; Subrahmanyam, P.; Singh, A. K.

2011-02-01

77

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

78

Long time scale evolution of high-power radio wave ionospheric heating 1. Beam propagation  

Microsoft Academic Search

The long time scale evolution, that is, for times long compared to an electron collision period of high-power radio wave ionospheric heating, is studied. Preliminary studies are made to model high-power radio wave propagation in an ionosphere containing a dynamically produced electron density cavity. We show that high-power radio wave-induced plasma density depletions in the F region ionosphere will convect

M. J. Keskinen; P. K. Chaturvedi; S. L. Ossakow

1993-01-01

79

Long time scale evolution of high-power radio wave ionospheric heating. 1. Beam propagation  

Microsoft Academic Search

The long time scale evolution, that is, for times long compared to an electron collision period of high-power radio wave ionospheric heating, is studied. Preliminary studies are made to model high-power radio wave propagation in an ionosphere containing a dynamically produced electron density cavity. We show that high-power radio wave-induced plasma density depletions in the F region ionosphere will convect

M. J. Keskinen; P. K. Chaturvedi; S. L. Ossakow

1993-01-01

80

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

ERIC Educational Resources Information Center

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

Spradley, Joseph L.

1988-01-01

81

Upper limits on gravitational wave emission from 78 radio pulsars  

NASA Astrophysics Data System (ADS)

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

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

2007-08-01

82

Radio Wave Propagation Handbook for Communication on and Around Mars  

NASA Technical Reports Server (NTRS)

This handbook examines the effects of the Martian environment on radio wave propagation on Mars and in the space near the planet. The environmental effects include these from the Martian atmosphere, ionosphere, global dust storms, aerosols, clouds, and geomorphologic features. Relevant Martian environmental parameters were extracted from the measurements of Mars missions during the past 30 years, especially from Mars Pathfinder and Mars Global Surveyor. The results derived from measurements and analyses have been reviewed through an extensive literature search. The updated parameters have been theoretically analyzed to study their effects on radio propagation. This handbook also provides basic information about the entire telecommunications environment on and around Mars for propagation researchers, system engineers, and link analysts. Based on these original analyses, some important recommendations have been made, including the use of the Martian ionosphere as a reflector for Mars global or trans-horizon communication between future Martian colonies, reducing dust storm scattering effects, etc. These results have extended our wave propagation knowledge to a planet other than Earth; and the tables, models, and graphics included in this handbook will benefit telecommunication system engineers and scientific researchers.

Ho, Christian; Golshan, Nasser; Kliore, Arvydas

2002-01-01

83

Optical detection of radio waves through a nanomechanical transducer.  

PubMed

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 800 pV Hz-1/2 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 60 pV Hz-1/2 when balanced by choosing an electromechanical cooperativity of ~150 with an optical power of 1?mW. The noise temperature of the membrane is divided by the cooperativity. For the highest observed cooperativity of 6,800, this leads to a projected noise temperature of 40 mK and a sensitivity limit of 5 pV Hz-1/2. 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. PMID:24598636

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

84

Possible Electromagnetic Interference with Electronic Medical Equipment by Radio Waves Coming from Outside the Hospital  

Microsoft Academic Search

Electromagnetic interference (EMI) with electronic medical equipment by radio waves from mobile telephone handsets has been reported and is currently receiving wide attention. The possibility of EMI with electronic medical equipment by radio waves coming into the hospital has also been pointed out. But so far, there are no reports measuring the frequency distribution of electric field intensity induced by

Eisuke Hanada; Kenji Kodama; Kyoko Takano; Yoshiaki Watanabe; Yoshiaki Nose

2001-01-01

85

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

Microsoft Academic Search

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

Charles Burrows

1962-01-01

86

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

ERIC Educational Resources Information Center

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

Dombi, Andra; Tunyagi, Arthur; Neda, Zoltan

2013-01-01

87

Z mode waves as the source of Saturn narrowband radio emissions  

E-print Network

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

Gurnett, Donald A.

88

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

89

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

SciTech Connect

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

Singh, Rohtash; Sharma, A. K.; Tripathi, V. K. [Department of Physics, Indian Institute of Technology Delhi, New Delhi-110016 (India)

2011-11-15

90

Annual report 1992/93, FOA 38. Radio systems and wave propagation  

NASA Astrophysics Data System (ADS)

The main objective of the division of Radio Systems and Wave Propagation is to carry out research and development in the field of secure and robust radio communications for Sweden's national defense. This is the Annual Report for fiscal year 1992/93 of the Division of Radio Systems and Wave Propagation. The division is responsible for research and development of secure radio communication for information transmission. We are also responsible for wave propagation research within a frequency range from LF to SHF. We carry out applied research in fields like antijamming systems, modulation, error correcting codes, wave propagation and digital signal processing. The wave propagation research is carried out by basic research so the demands from new techniques and new radio systems for accurate propagation models can be achieved.

Mildh, I. M.

1994-01-01

91

An equatorial scintillation model  

Microsoft Academic Search

Radiowave scintillation in the presence of natural and\\/or high altitude nuclear disturbances has the potential to disrupt numerous transionospheric radio and radar systems. This report develops a model characterizing the plasma density irregularities that produce scintillation in the naturally disturbed equatorial F layer. The model has been incorporated into Program WBMOD along with subroutines for computing both link geometry and

E. J. Fremouw; R. E. Robins

1985-01-01

92

Model of interaction between decameter-decimenter radio waves and a strongly inhomogeneous mid-latitude ionosphere  

Microsoft Academic Search

A model of decameter-decimeter radio wave propagation in a strongly inhomogeneous mid-latitude ionosphere is constructed using\\u000a a modified method of radio wave refractive scattering. The model establishes the relationship between the basic statistical\\u000a radio wave characteristics and the turbulence parameters of the upper ionosphere. Different aspects of the theory of radio\\u000a wave refractive scattering are considered in application to the

V. A. Alimov; A. V. Rakhlin; F. I. Vybornov

1997-01-01

93

Radio Wave Scattering in the Outer Heliosphere: Preliminary Calculations  

NASA Technical Reports Server (NTRS)

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

Cairns, Iver H.

1995-01-01

94

Catalogue of the 1997 SOHO-EIT coronal transient waves and associated type II radio burst spectra  

Microsoft Academic Search

We compare the coronal transient wave phenomenon discovered by SOHO extreme ultraviolet observations (``EIT waves'') with the associated radio signature of a coronal shock wave (type II burst). 90% of the type II bursts are associated with an EIT wave. On average, the speed derived from the radio burst is about three times larger than the EIT wave speed. Within

A. Klassen; H. Aurass; G. Mann; B. J. Thompson

2000-01-01

95

Relationships Between Star Size, Radio Wave Emissions, and Dust Stellar Astronomy and Radio Emissions  

Microsoft Academic Search

Radio astronomy is a branch of astronomy that deals with radio emissions from celestial objects. Hydrogen is an abundant element that makes up much of the universe. Neutral Hydrogen, found in many parts of the sky, emits radio emissions at a frequency of 1420MHz as its protons fall into lower energy levels. Through the use of a radio telescope, one

Parth Sehgal; Julian Trent; Adam Susaneck; Matt Robinson

96

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

SciTech Connect

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

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

2006-07-31

97

Low-latitude ionospheric scintillations and total electron content obtained with the CITRIS instrument on STPSat1 using radio transmissions from DORIS ground beacons  

NASA Astrophysics Data System (ADS)

The primary objective of the Scintillation and Tomography Receiver in Space (CITRIS) is to detect ionospheric irregularities from space at low latitude. For this purpose, the satellite receiver uses the UHF and S-Band transmissions of the ground network of Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) beacons. CITRIS, developed at the Naval Research Laboratory, differs from the normal DORIS receiver by being able to capture and store the complex amplitude of the 401.25 and 2036.25 MHz transmissions at 200 Hz sample rate. Ground processing of the CITRIS data yields total electron content (TEC) and both phase and amplitude scintillations. With CITRIS flying on the US Space Test Program (STP) satellite STPSat1, 2 years of data were collected and processed to determine the fluctuations in ionospheric TEC and radio scintillations associated with equatorial irregularities. CITRIS flights over DORIS transmitters yield direct measurements of the horizontal plasma density fluctuations associated with equatorial plasma bubbles. Future flights of CITRIS can provide valuable complements to other satellite instruments such as GPS occultation receivers used to estimate vertical electron density profiles in the ionosphere.

Bernhardt, Paul A.; Siefring, Carl L.

2010-06-01

98

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

SciTech Connect

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

Ivanov, V.B.

1995-05-01

99

Put a Short-Wave Radio in Your Foreign Language Classroom  

ERIC Educational Resources Information Center

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

Oksenholt, Svein

1977-01-01

100

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

Microsoft Academic Search

Detailed in situ observations from the ISEE 3 spacecraft of energetic electrons, plasma waves, and radio emission for the type II solar radio burst of February 17, 1979, are presented. The reduced, one-dimensional electron distribution function is constructed as a function of time. Since the faster electrons arrive before the slower ones, a bump on tail distribution forms which is

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

1981-01-01

101

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

102

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

Microsoft Academic Search

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

O. F. Tyrnov

1974-01-01

103

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

Microsoft Academic Search

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

F. W. Perkins; R. G. Roble

1978-01-01

104

Turbulence-induced millimeter-wave scintillation compared with micrometeorological measurements  

Microsoft Academic Search

Scintillations of intensity and phase difference were measured at millimeter wavelengths in a horizontally homogeneous atmospheric surface layer. Simultaneous micrometeorological and optical propagation measurements characterized the clear-air turbulence. Predicted and measured propagation statistics are in good agreement. It is shown that the phase structure function showed a rolloff at large spacings as was expected because the outer scale of the

Reginald J. Hill; Steven F. Clifford; Joseph Tant Priestley; Ronald A. Bohlander; Robert W. McMillan

1988-01-01

105

STEREO/WAVES antennas calibration: Implications for radio source triangulation  

NASA Astrophysics Data System (ADS)

NASA will launch in April 2006 the two STEREO spacecraft with the radio experiment, called SWAVES, which is designed to observe solar radio emissions by using direction finding capabilities. This method enables the triangulation of radio sources. The present paper provides the latest results on the determination of the effective antenna vectors and the methodology of direction finding. Further it gives some thoughts on the implications of the data interpretation, since higher frequency observations have direction of incidence dependent effective antenna vectors.

Oswald, T. H.; Macher, W.; Fischer, G.; Rucker, H. O.; Taubenschuss, U.; Bougeret, J. L.; Kaiser, M. L.; Goetz, K.

2005-12-01

106

Type II radio bursts: Applications of a new analytic formalism for the electron beams, Langmuir waves, and radio emission  

NASA Astrophysics Data System (ADS)

Type II radio bursts drift in frequency as shock waves and coronal mass ejections (CMEs) move through the Sun's corona and the solar wind. We apply an extended theoretical model for type II radio bursts to an MHD simulation of rippled shock fronts found at the flanks of a CME-driven shock. The theory treats the acceleration of electrons at the shock, formation of electron beams, growth of Langmuir waves, and conversion of Langmuir energy into radiation. The extended theory is entirely analytic and includes kappa electron velocity distribution functions for the plasma electrons and the shock-reflected electron beam. It also includes the plateauing of the electron beam, which releases energy for the Langmuir waves. This paper presents and discusses our numerical results for synthetic radio images and synthetic dynamical spectra, gained by applying our radiation model to MHD simulations of a coronal shock driven by a CME. The investigation reveals strong emission upstream of the flanks of the shock. A complicated rippled shock geometry develops with embedded ``bright spots'' that stimulate torch-like short-lived radio sources, which lead to complicated substructures in the dynamic spectrum.

Schmidt, Joachim; Cairns, Iver

2012-07-01

107

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

ERIC Educational Resources Information Center

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

Marine Corps, Washington, DC.

108

An investigation of methods for improving models of ionospheric plasma-density irregularities and radio-frequency scintillation  

Microsoft Academic Search

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

James A. Secan; Robert M. Bussey

1993-01-01

109

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

Microsoft Academic Search

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

J. A. Secan; R. M. Bussey

1993-01-01

110

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

111

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

112

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

113

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

Microsoft Academic Search

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

S. Bardwell; M. V. Goldman

1976-01-01

114

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

NASA Technical Reports Server (NTRS)

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

Borovsky, Joseph E.

1987-01-01

115

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

NASA Technical Reports Server (NTRS)

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

Borovsky, Joseph E.

1987-01-01

116

Higher order moments used in ionospheric scintillation description  

NASA Astrophysics Data System (ADS)

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

Stevanovic, D.; Wernik, A. W.

2013-12-01

117

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

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

118

Type II radio bursts: 1. New entirely analytic formalism for the electron beams, Langmuir waves, and radio emission  

NASA Astrophysics Data System (ADS)

Type II radio bursts drift in frequency as shock waves and coronal mass ejections (CMEs) move through the Sun's corona and the solar wind. This paper extends the theoretical models for type II radio bursts of Knock et al. (2001, 2003), Knock and Cairns (2005), Cairns and Knock (2006) and Schmidt and Gopalswamy (2008). The theory treats the acceleration of electrons at the shock, formation of electron beams, growth of Langmuir waves, and conversion of Langmuir energy into radiation. An entirely analytical and more general formalism is developed, which includes kappa electron velocity distribution functions for the plasma electrons and the shock-reflected electron beam. The radiation model also includes the plateauing of the electron beam, which releases energy for the Langmuir waves. This paper has two parts. First, the new entirely analytical formalism is presented. Second, first numerical results for synthetic radio images and synthetic dynamic spectra are discussed, gained by applying our radiation model to MHD simulations of a shock driven by a CME. The results are compared with earlier analytic approaches. This work is also applicable to other shock-related emissions in space and astrophysical plasmas.

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

2012-04-01

119

Millimeter-wave fiber optics systems for personal radio communication  

Microsoft Academic Search

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

Hiroyo Ogawa; David Polifko; Seiichi Banba

1992-01-01

120

Clumpy Langmuir waves in type III radio sources  

Microsoft Academic Search

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

P. A. Robinson

1992-01-01

121

Single Step Generation of Micro and Radio Wave Signals in a Short Cavity Fiber Laser  

Microsoft Academic Search

Generation of stable micro or radio waves by fre- quency down-conversion has always been a challenging but rewarding task in radio over fiber systems. In this letter, a novel method for such a generation using a short-cavity fiber laser is demonstrated. For this purpose, an all-fiber laser is designed to have two stable longitudinal laser modes, each of them having

Udari Basnayaka; Xavier Fernando; Xijia Gu

2011-01-01

122

Radio-Frequency and Millimeter-Wave Photonic Techniques for Broadband Communications and Sensor Networks  

Microsoft Academic Search

Recent advances in radio-frequency (RF) and millimeter-wave (mmW) photonics are reviewed with emphasis on our research in broadband radio-over-fiber system architectures, photonic generation and processing of RF and mmW signals, and optoelectronic device design for mmW photonics applications. Future system design challenges are also discussed. In particular, the concept of substrate integrated circuits (SICs) is shown to have great potentials

Jianping Yao; Xiupu Zhang; Raman Kashyap; Ke Wu

2006-01-01

123

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

SciTech Connect

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

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

2013-06-13

124

Circular Polarization Induced by Scintillation in a Magnetized Medium  

E-print Network

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

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

2000-06-30

125

Scintillation Monitoring Using Asymmetry Index  

NASA Astrophysics Data System (ADS)

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

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

126

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

SciTech Connect

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

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

2009-02-13

127

A mid-latitude scintillation model  

Microsoft Academic Search

Radiowave scintillation in the presence of ionospheric disturbances has the potential to disrupt numerous transionospheric radio and radar systems. This report describes development of a model characterizing the plasma density irregularities that produce scintillation in the naturally disturbed mid latitude F layer. The model will be incorporated into Program WBMOD, which includes subroutines for computing both link geometry and scintillation

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

1986-01-01

128

Atmospheric and ionospheric phenomena related to anomalous VHF-band radio wave transmissions beyond the line of sight  

NASA Astrophysics Data System (ADS)

We have monitored anomalous VHF-band radio wave transmissions received beyond the line of sight prior to earthquakes since 2003 in Hokkaido, northern Japan, to determine the relationship between anomalous transmission of VHF-band radio waves and impending earthquakes. Anomalous VHF-band radio waves were recorded before some medium and large earthquakes of magnitude 4 or higher. Radio waves transmitted from a specific FM radio station are considered to have been scattered in the atmosphere, allowing the radio waves to be received by an observation station beyond the line of sight of the transmitter. One hypothesis to explain the pre-earthquake anomalous radio transmissions is that radon gas emanates from the surface as a result of increasing fluid pressure during the preparation process of an earthquake. The radon release increases the density of small ions and the atmospheric conductivity and decreases the atmospheric electric field in the lower atmosphere. To confirm the process, we monitored the atmospheric electric field at the VHF radio wave monitoring site. Variations in the atmospheric electric field accompanied by anomalous radio wave transmissions were observed at times. Additionally, larger anomalous transmission may be caused by the sporadic E layer of the ionosphere in the early summer season. The sporadic E anomalies overlap anomalies associated with earthquakes and can be distinguished as a distinct feature.

Mogi, T.; Kakinami, Y.; Moriya, T.

2013-12-01

129

Dielectric Effect on the Radio-Frequency Characteristics of a Rectangular Waveguide Grating Traveling Wave Tube  

NASA Astrophysics Data System (ADS)

A new type of partial-dielectric-loaded rectangular waveguide grating slow-wave structure (SWS) for millimeter wave traveling wave tube (TWT) is presented in this paper. The radio-frequency characteristics including the dispersion properties, the longitudinal electric field distribution and the beam-wave coupling impedance of this structure are analyzed. The results show that the dispersion of the rectangular waveguide grating circuit is weakened, the phase velocity is reduced and the position of the maximum E z is basically invariant after partially filling the dielectric materials in the rectangular waveguide grating SWS. Although the coupling impedance decreases a little, it still keeps above 40 ?.

Lu, Zhigang; Gong, Yubin; Wei, Yanyu; Wang, Wenxiang

2006-08-01

130

A Forecasting Ionospheric Real-time Scintillation Tool (FIRST)  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

131

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

132

Modeling and scientific application of scintillation results  

NASA Astrophysics Data System (ADS)

At many locations around the world, observations have been made of ionospherically imposed radio wave scintillations. There is, therefore, a need for an orderly means to assemble the data. Computer-based models intended for application to transionospheric communication systems provide such a scientifically useful repository of information. The present study is concerned with an attempt to illustrate such models with the aid of a particular model which was developed during a period of several years. This model resides now in a computer code called WBMOD. Attention is given to the elements of a scientifically useful model, the employed modelling approach, and the characteristics of the current model.

Fremouw, E. J.; Secan, J. A.

1984-06-01

133

The Abundance of X-Shaped Radio Sources II. Implications for the Gravitational Wave Background  

E-print Network

Coalescence of super massive black holes (SMBH's) in galactic mergers is potentially the dominant contributor to the low frequency gravitational wave background (GWB). It was proposed by Merritt and Ekers (2002) that X-shaped radio galaxies are signposts of such coalescences, and that their abundance might be used to predict the magnitude of the gravitational wave background. In Roberts et al. (2015) we present radio images of all 52 X-shaped radio source candidates out of the sample of 100 selected by Cheung (2007) for which archival VLA data were available. These images indicate that at most 21% of the candidates might be genuine X-shaped radio sources that were formed by a restarting of beams in a new direction following a major merger. This suggests that fewer than 1.3% of extended radio sources appear to be candidates for genuine axis reorientations, much smaller than the 7% suggested by Leahy and Parma (1992). Thus the associated gravitational wave background may be substantially smaller than previous e...

Roberts, David H; Subrahmanyan, Ravi

2015-01-01

134

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

NASA Astrophysics Data System (ADS)

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

Huebner, Christof; Kottmeier, Christoph; Brandelik, Alexander

2011-06-01

135

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

136

LETTER doi:10.1038/nature13029 Optical detection of radio waves through a  

E-print Network

.Efficientup-conversionofradio-frequency signals to anopticalcarrier wouldenable their transmission through optical fibres instead of throughLETTER doi:10.1038/nature13029 Optical detection of radio waves through a nanomechanical transducer­5 or optical fields6,7 . Here we demonstrate a room-temperature optoelec- tromechanical transducer with both

Cai, Long

137

A Direct-Reading Radio-Wave-Reflection-Type Absolute Altimeter for Aeronautics  

Microsoft Academic Search

Various theoretical and experimental researches have been carried out to indicate the absolute altitude of aircraft with respect to the ground by radio-wave-reflection methods. By using a new principle, frequency modulation (FM), the following results have been obtained: 1. Completely continuous indication of altitude by a steady pointer and dial is easily accomplished and altitude variations occurring during time intervals

S. Matsuo

1938-01-01

138

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

139

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

140

Isotropic approximation errors in geometrical-optical description of ionospheric propagation of radio waves  

NASA Astrophysics Data System (ADS)

Isotropic approximation, i.e. neglect of magnetic field effects, is widely used to simplify the geometrical optics description of ionospheric propagation of radio waves. However, this description under certain conditions may produce a significant error. In this study, ray traycing is performed to examine an isotropic approximation error in relation to operating frequency and radiation angles.

Laryunin, O. A.; Kurkin, V. I.

2014-11-01

141

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

Microsoft Academic Search

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

W. E. Gordon

1958-01-01

142

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

143

An investigation of methods for improving models of ionospheric plasma-density irregularities and radio-frequency scintillation  

NASA Astrophysics Data System (ADS)

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 first year, which includes construction of the modeling database, development of a new format for the internal representation of the irregularity strength, and development of new models for the diurnal, latitudinal, seasonal, and longitudinal variations in the equatorial region.

Secan, James A.; Bussey, Robert M.; Fremouw, Edward J.; Reinleitner, Lee A.

1993-03-01

144

An investigation of methods for improving models of ionospheric plasma-density irregularities and radio-frequency scintillation  

NASA Astrophysics Data System (ADS)

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 for the high latitude (auroral and polar cap) region.

Secan, James A.; Bussey, Robert M.

1993-11-01

145

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

146

Radio wave propagation experiments to probe the ionosphere  

NASA Technical Reports Server (NTRS)

Ionospheric bias corrections associated with radio tracking of spacecraft depend on the following measuring techniques for integrated electron content: (1) Faraday rotation measurements from an earth synchronous satellite; (2) ranging measurements at two frequencies; and (3) group and phase velocity measurements obtained from tracking data. The extraction of the integrated electron content directly from tracking data is achieved by comparison of range-rate measurements based on Doppler shift with differentiated range measurements based on tone delay. This method is most desirable because the measured corrections pertain directly to the spacecraft whose orbit is being determined and can be used in near earth as well as deep space tracking data.

Schmid, P. E.

1972-01-01

147

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

NASA Astrophysics Data System (ADS)

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

Golla, T.; MacDowall, R. J.

2013-12-01

148

Inconsistency of Ulysses Millisecond Langmuir Spikes with Wave Collapse in Type 3 Radio Sources  

NASA Technical Reports Server (NTRS)

Recent Ulysses observations of millisecond spikes superposed on broader Langmuir wave packets in type 3 radio sources are compared quantitatively with constraints from the theory of wave collapse. It is found that both the millisecond spikes and the wave packets have fields at least 10 times too small to be consistent with collapse, contrary to previous interpretations in terms of this process. Several alternative explanations are considered and it is argued that the spikes should be interpreted as either non-collapse phenomena or observational artifacts. To the extent the observations are representative, this rules out theories for type 3 bursts at approx. 1 - 4 AU that rely on collapse.

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

1995-01-01

149

Radio Wave 'Messengers' of Periodic Gravitational Radiation and the Problem of Gravitationally Induced Nonlinearity in Electrodynamic Systems  

E-print Network

We discuss a gravitationally induced nonlinearity in hierarchic systems. We consider the generation of extremely low-frequency radio waves with a frequency of the periodic gravitational radiation; the generation is due to an induced nonlinear self-action of electromagnetic radiation in the vicinity of the gravitational-radiation source. These radio waves are a fundamentally new type of response of an electrodynamic system to gravitational radiation. That is why we here use an unconventional term: radio-wave messengers of periodic gravitational radiation.

A. B. Balakin; Z. G. Murzakhanov; G. V. Kisun'ko

2005-11-10

150

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

NASA Astrophysics Data System (ADS)

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

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

151

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

Microsoft Academic Search

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

E. M. Warrington; D. R. Siddle

152

Timing noise of radio pulsars and implications to neutron star's interior structure and gravitational wave detection  

NASA Astrophysics Data System (ADS)

Abstract: Radio pulsars are the most stable natural clocks in the universe, yet timing irregularities or noises can still be substantial when the times of arrivals of their pulses are fitted with some well accepted spin-down models or templates of pulsars. In this talk, I will review our recent work on modeling the timing noises of radio pulsars. Our model includes a long-term power-law decay modulated by periodic oscillations of the surface magnetic fields of neutron stars. Our model can explain the statistical properties of their timing noises. We find that the spin-down evolutions of young and old pulsars are dominated by the power-law decay and periodic oscillations, respectively. By applying our model to the individual spin-down evolutions of several well-measured radio pulsars, we find evidence for Hall drifts and Hall waves in the crusts of neutron stars. The relaxation behaviors of both classical and slow glitches can also be modeled as evolution of their surface magnetic fields, but with opposite trends. Finally we also attempt to improve the sensitivity of detecting gravitational waves with pulsars by applying our model to reduce the timing residuals of millisecond radio pulsars. Our main publications related to this talk are: 2012, ApJ, 757, 153; 2012, ApJ, 761, 102; 2013, ApJ, 778, 31; arXiv:1307.6413, 1312.3049.

Zhang, Shuang-Nan; Xie, Yi

153

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

PubMed

Mergers of neutron-star/neutron-star binaries are strong sources of gravitational waves. They can also launch subrelativistic and mildly relativistic outflows and are often assumed to be the sources of short ?-ray bursts. An electromagnetic signature that persisted for weeks to months after the event would strengthen any future claim of a detection of gravitational waves. Here we present results of calculations showing that the interaction of mildly relativistic outflows with the surrounding medium produces radio flares with peak emission at 1.4 gigahertz that persist at detectable (submillijansky) levels for weeks, out to a redshift of 0.1. Slower subrelativistic outflows produce flares detectable for years at 150 megahertz, as well as at 1.4 gigahertz, from slightly shorter distances. The radio transient RT 19870422 (ref. 11) has the properties predicted by our model, and its most probable origin is the merger of a compact neutron-star/neutron-star binary. The lack of radio detections usually associated with short ?-ray bursts does not constrain the radio transients that we discuss here (from mildly relativistic and subrelativistic outflows) because short ?-ray burst redshifts are typically >0.1 and the appropriate timescales (longer than weeks) have not been sampled. PMID:21964342

Nakar, Ehud; Piran, Tsvi

2011-10-01

154

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

155

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

156

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

Microsoft Academic Search

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

M. Ashrafi; K. Kaila; B. Isham

2007-01-01

157

High resolution of electromagnetic waves in time-varying radio channels  

Microsoft Academic Search

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

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

1997-01-01

158

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

159

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

E-print Network

ON THE BRIGHTNESS AND WAITING-TIME DISTRIBUTIONS OF A TYPE III RADIO STORM OBSERVED BY STEREO.S.A. ON THE BRIGHTNESS AND WAITING-TIME DISTRIBUTIONS OF A TYPE III RADIO STORM OBSERVED BY STEREO/WAVES J. P. Eastwood1 to the quasi-continuous, bursty emission of electron beams onto open field lines above active regions

California at Berkeley, University of

160

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

NASA Technical Reports Server (NTRS)

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

Kurth, W. S.

2001-01-01

161

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

E-print Network

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

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

2009-01-01

162

Radio Remnants of Compact Binary Mergers - the Electromagnetic Signal that will follow the Gravitational Waves  

E-print Network

The question "what is the observable electromagnetic (EM) signature of a compact binary merger?" is an intriguing one with crucial consequences to the quest for gravitational waves (GW). Compact binary mergers are prime sources of GW, targeted by current and next generation detectors. Numerical simulations have demonstrated that these mergers eject energetic sub-relativistic (or even relativistic) outflows. This is certainly the case if the mergers produce short GRBs, but even if not, significant outflows are expected. The interaction of such outflows with the surround matter inevitably leads to a long lasting radio signal. We calculate the expected signal from these outflows (our calculations are also applicable to short GRB orphan afterglows) and we discuss their detectability. We show that the optimal search for such signal should, conveniently, take place around 1.4 GHz. Realistic estimates of the outflow parameters yield signals of a few hundred $\\mu$Jy, lasting a few weeks, from sources at the detection horizon of advanced GW detectors. Followup radio observations, triggered by GW detection, could reveal the radio remnant even under unfavorable conditions. Upcoming all sky surveys can detect a few dozen, and possibly even thousands, merger remnants at any give time, thereby providing robust merger rate estimates even before the advanced GW detectors become operational. In fact, the radio transient RT 19870422 fits well the overall properties predicted by our model and we suggest that its most probable origin is a compact binary merger radio remnant.

Ehud Nakar; Tsvi Piran

2011-02-04

163

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

164

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

165

Whistler-mode wave-injection experiments in the plasmasphere with a radio sounder  

NASA Astrophysics Data System (ADS)

Whistler-mode wave-injection experiments with a high-altitude radio sounder offer an opportunity to greatly extend the observing power of satellites such as imager for magnetopause-to-aurora global exploration (IMAGE) when the satellite is within or near the plasmasphere or at low altitudes over the polar regions. We use as an example the radio plasma imager (RPI) instrument on IMAGE, which includes crossed 500-m electric antennas in the spin plane and a 20-m antenna along the spin axis (for reception only). The 500-m antennas approach a half-wavelength at whistler-mode frequencies in the 3-30kHz range and should have a radiation efficiency of 1-10%. The wave power within ~100km of the transmitter should be greater than that produced by wave injection from the ground-based very low-frequency (VLF) transmitter at Siple, Antarctica, thus making possible experiments on wave-particle energy and momentum exchange. We use ray tracings along a sample IMAGE orbit (polar, apogee ~8RE) to show the conditions under which transmitted signals may return to the satellite as echoes, following reflection, or be observed by satellites of opportunity, such as EXOS-D. We find that ground reception of transmitted signals should be possible as a result of a linear mode conversion process in regions of ionospheric irregularities. We discuss the determination of wave-normal angles of returning signals, which will aid in identifying the signal path and obtaining information on plasma boundaries and irregularities. The science topics that may be addressed include: (1) investigation of the nonlinear process by which weak coherent waves excite VLF emissions; (2) probing plasmaspheric density structure, including plasmaspheric density cavities, field aligned waveducts, density irregularities in the plasmapause region, and the ionospheric density structure where conversion of whistler-mode wave energy to quasi-electrostatic lower hybrid (LHR) waves (and vice versa) can take place.

Sonwalkar, V. S.; Chen, X.; Harikumar, J.; Carpenter, D. L.; Bell, T. F.

2001-07-01

166

Computational strategy for modeling radio wave propagation in lossy circular waveguides  

SciTech Connect

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

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

2008-01-01

167

Dispersion Effects in Millimeter-Wave Fiber-Radio Systems Employing Direct-Sequence Code Division Multiple Access  

NASA Astrophysics Data System (ADS)

We investigate the impact of fiber chromatic dispersion on the performance of an externally modulated millimeter-wave fiber-radio system incorporating a broadband radio direct-sequence code division multiple access (DS-CDMA) scheme. In particular, we investigate the effect of dispersion on DS-CDMA signals with regard to CDMA code rate, center frequency, and modulator chirp. We show that the spreading of the signal spectrum using DS-CDMA can result in significant reductions in data amplitude variations normally experienced in externally modulated millimeter-wave fiber-radio systems. We also demonstrate the successful transmission of a 10-Mb/s data channel over a 39-GHz fiber-radio link employing DS-CDMA and consisting of 25 km of standard optical fiber and a 1-m radio link.

Smith, G. H.; Nirmalathas, A.; Yates, J.; Novak, D.

1999-04-01

168

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

169

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

170

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

171

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

172

Ion Acoustic Wave Frequencies and Onset Times During Type 3 Solar Radio Bursts  

NASA Technical Reports Server (NTRS)

Conflicting interpretations exist for the low-frequency ion acoustic (S) waves often observed by ISEE 3 in association with intense Langmuir (L) waves in the source regions of type III solar radio bursts near 1 AU. Two indirect lines of observational evidence, as well as plasma theory, suggest they are produced by the electrostatic (ES) decay L yields L(PRIME) + S. However, contrary to theoretical predictions, an existing analysis of the wave frequencies instead favors the electromagnetic (EM) decays L yields T + S, where T denotes an EM wave near the plasma frequency. This conflict is addressed here by comparing the observed wave frequencies and onset times with theoretical predictions for the ES and EM decays, calculated using the time-variable electron beam and magnetic field orientation data, rather than the nominal values used previously. Field orientation effects and beam speed variations are shown analytically to produce factor-of-three effects, greater than the difference in wave frequencies predicted for the ES and EM decays; effects of similar magnitude occur in the events analyzed here. The S-wave signals are extracted by hand from a sawtooth noise background, greatly improving the association between S waves and intense L waves. Very good agreement exists between the time-varying predictions for the ES decay and the frequencies of most (but not all) wave bursts. The waves occur only after the ES decay becomes kinematically allowed, which is consistent with the ES decay proceeding and producing most of the observed signals. Good agreement exists between the EM decay's predictions and a significant fraction of the S-wave observations while the EM decay is kinematically allowed. The wave data are not consistent, however, with the EM decay being the dominant nonlinear process. Often the observed waves are sufficiently broadband to overlap simultaneously the frequency ranges predicted for the ES and EM decays. Coupling the dominance of the ES decay with this frequency overlap provides support for a previous suggestion that fundamental emission occurs when the EM decay is stimulated by the ES decay product waves. The periods in which the ES and EM decays produce observable S waves are consistent with the observed and (independently) predicted times of fundamental and harmonic radio emission. This supports interpretation of fundamental emission as stimulated EM decay and harmonic emission as the coalescence L + L(prime) yields T of beam-generated L waves and L(prime) waves produced by the ES decay, where T denotes an electromagnetic wave at twice the plasma frequency. Analysis of the electron beam data reveals that the time-varying beam speed is consistent with ballistic beam propagation with minimal energy loss, implying that the beam propagates in a state close to time- and volume-averaged marginal stability. This confirms a central tenet of the stochastic growth theory for type III bursts.

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

1995-01-01

173

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

174

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

175

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

176

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

SciTech Connect

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

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

1998-11-01

177

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

178

Discovery of Millimeter-Wave Excess Emission in Radio-Quiet Active Galactic Nuclei  

E-print Network

The physical origin of radio emission in Radio Quiet Active Galactic Nuclei (RQ AGN) remains unclear, whether it is a downscaled version of the relativistic jets typical of Radio Loud (RL) AGN, or whether it originates from the accretion disk. The correlation between 5 GHz and X-ray luminosities of RQ AGN, which follows $L_R = 10^{-5}L_X$ observed also in stellar coronae, suggests an association of both X-ray and radio sources with the accretion disk corona. Observing RQ AGN at higher (mm-wave) frequencies, where synchrotron self absorption is diminished, and smaller regions can be probed, is key to exploring this association. Eight RQ AGN, selected based on their high X-ray brightness and variability, were observed at 95 GHz with the CARMA and ATCA telescopes. All targets were detected at the $1-10$ mJy level. Emission excess at 95~GHz of up to $\\times 7$ is found with respect to archival low-frequency steep spectra, suggesting a compact, optically-thick core superimposed on the more extended structures that...

Behar, Ehud; Laor, Ari; Horesh, Assaf; Stevens, Jamie; Tzioumis, Tasso

2015-01-01

179

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

Microsoft Academic Search

The Coordinated Radio, Electron, and Waves Experiment (CREWE) was designed to determine density, bulk velocity and temperature of the electrons for the NASA Comet Rendezvous and Asteroid Flyby Spacecraft, to define the MHD-SW IMF flow configuration; to clarify the role of impact ionization processes, to comment on the importance of anomalous ionization phenomena (via wave particle processes), to quantify the

Jack D. Scudder

1992-01-01

180

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

NASA Technical Reports Server (NTRS)

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

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

1995-01-01

181

Intensity Scintillations in Planetary Rings Occultation: Theory  

Microsoft Academic Search

We use the classical diffraction screen approach to develop a theoretical foundation for investigation of the intensity scintillations observed during stellar occultation of the Voyager spacecraft by Saturn's rings (Showalter and Nicholson, Icarus 87, 285-306, 1990). The formulation is guided by procedures developed for analysis of scintillations of stars observed through the turbulent Earth atmosphere and of natural radio sources

Essam A. Marouf

1998-01-01

182

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.

183

Scintillation Mathematics  

E-print Network

, in particular, when low margin systems are employed. #15; Various models of scintillation have been proposed, with an elevation angle of 40 � . #15; The sampling rate was 18.66 Hz, sufficient for a detailed study of tropospheric scintillation. #15; The data has been divided into rain and non­rain periods by using a radiometer

Baxter, Paul D.

184

Transmission and reception of high fidelity sound in buildings using surface transverse wave based 1 GHz FM radio  

Microsoft Academic Search

A new system application of shear horizontal (SH) acoustic wave devices as extended cavity high-𝒬 surface transverse wave (STW) resonators, low-𝒬 surface skimming bulk wave (SSBW) resonators, and SSBW\\/STW combined mode resonator filters (CMRFs) is presented. Frequency modulated (FM) microtransmitters are implemented in a 1-GHz multichannel local area radio network (LARN) for wireless transmission and reception of high-fidelity sound in

I. D. Avramov

1992-01-01

185

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

NASA Technical Reports Server (NTRS)

We recommend to use the dayside Martian ionosphere as a reflector for global communication, because the dayside ionosphere has stable density peak and usable critic frequency. This is very crucial for the future Mars ground to around communication. The dayside ionosphere has been well modeled as a Chapman layer. We suggest to perform the Martian nightside ionospheric modeling study. Because the nightside ionosphere has very little measurements available, we propose to drop a digital ionosond instrument into the Mars surface for data collection. Even though the Martian tropospheric radio refractivity has small value, it still can cause the ray bending and multipath effects. We recommend to perform an accurate calculation on excess phase and group delays (range and time delays). Other effects, such as range rate errors, appearance angle deviation, defocusing loss on Mars, etc. are also needed to be estimated. Ice depolarization effects due to Martian clouds on radio waves is unknown yet, which is expected to be small, because lower optical depth and thinner layer of cloud: Total Martian atmospheric gaseous attenuation is expected to be less than 1 dB on microwaves band, because the Martian atmosphere has very low concentration in uncondensed H2O and O2. An accurate calculation for zenith opacity requires the information about scale heights of H2O and O2 distribution. An accurate water vapor altitude profile at Mars is not available yet. Under the normal condition, CO2 and N2 gases do not have electric or magnetic dipoles and do not absorb electromagnetic energy from the waves. However, they may generate the dipoles through a collision and interact with waves under a high density condition and absorb electromagnetic waves in the infrared and visible band. Dust storm is most dominant factor to the radio wave attenuation. Large Martian dust storm can cause at least 3 dB or higher loss to Ka band wave. For a normal dust storm, the attenuation is about 1 dB. The attenuation much depends on dust mass loading, dust size distribution, etc. Most large dust storm occur in the southern hemisphere during later spring and early summer when the southern hemisphere become suddenly hot.

Ho, Christian; Golshan, Nasser

1999-01-01

186

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

NSDL National Science Digital Library

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

Kevin Wise

2007-04-01

187

Ion Heating in Field-Reversed Configuration by Radio-Frequency Waves  

NASA Astrophysics Data System (ADS)

A simple modeling of the recent experiment on plasma heating by radio-frequency (rf) waves in the field-reversed configuration (FRC) is made. In the FRC Injection Experiment device the ion heating by rf pulse was observed. Present analysis indicates that the heating can be explained by the Doppler broadening of the ion cyclotron resonance in the low magnetic field device. These results support the suggestion that the direct heating of the ion majority near the fundamental ion cyclotron frequency should be efficient in low field configurations.

Svidzinski, V. A.; Prager, S. C.

2003-12-01

188

Application of four wave mixing in precise radio frequency dissemination via optical fiber link  

NASA Astrophysics Data System (ADS)

We report on a new phase noise detection technique for radio frequency (RF) dissemination based on transferring mode locked laser pulses via optical fiber. The proposed approach is insusceptible to optical fiber interconnection reflection by combining optical frequency comb (OFC) expansion generated by four wave mixing (FWM) in dispersion shifted fiber (DSF) and wavelength division multiplexing (WDM) technique. An experimental system based on a fiber link of 100km was demonstrated. The measured fractional stability was 1.5×10-13 at 1s and 1.7×10-16 at 1000s.

Lu, Xing; Lv, Zhiqiang; Chen, Xing; Gong, Zibo; Shi, Kebin

2014-09-01

189

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

190

Radio Astronomy  

NSDL National Science Digital Library

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

Tenenbaum, David

191

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

Microsoft Academic Search

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

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

1998-01-01

192

Transmission of millimeter-wave signals in a fiber-radio system using a unitraveling-carrier waveguide photodiode  

Microsoft Academic Search

We employ a unitraveling-carrier waveguide photodiode (UTC-WGPD) to construct a fiber-radio remote base station without a millimeter-wave amplifier. BER characteristics of the fiber-radio system do not degrade when the UTC-WGPD is used even at a high optical input level of 10 dBm. We achieved error-free transmission of BPSK data over a 20-km standard fiber and a distance of 1 m

T. Ohno; S. Fukushima; Y. Doi; Y. Muramoto; Y. Matsuoka

2000-01-01

193

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

NASA Astrophysics Data System (ADS)

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

Kirillovich, Ivan; Gubenko, Vladimir; Pavelyev, Alexander

194

An equatorial scintillation model  

NASA Astrophysics Data System (ADS)

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

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

1985-09-01

195

SDN based millimetre wave radio over fiber (RoF) network  

NASA Astrophysics Data System (ADS)

This paper introduces software-defined, millimeter Wave (mm-Wave) networks with Radio over Fiber (RoF) for the delivery of gigabit connectivity required to develop fifth generation (5G) mobile. This network will enable an effective open access system allowing providers to manage and lease the infrastructure to service providers through unbundling new business models. Exploiting the inherited benefits of RoF, complete base station functionalities are centralized at the edges of the metro and aggregation network, leaving remote radio heads (RRHs) with only tunable filtering and amplification. A Software Defined Network (SDN) Central Controller (SCC) is responsible for managing the resource across several mm-Wave Radio Access Networks (RANs) providing a global view of the several network segments. This ensures flexible resource allocation for reduced overall latency and increased throughput. The SDN based mm-Wave RAN also allows for inter edge node communication. Therefore, certain packets can be routed between different RANs supported by the same edge node, reducing latency. System level simulations of the complete network have shown significant improvement of the overall throughput and SINR for wireless users by providing effective resource allocation and coordination among interfering cells. A new Coordinated Multipoint (CoMP) algorithm exploiting the benefits of the SCC global network view for reduced delay in control message exchange is presented, accounting for a minimum packet delay and limited Channel State Information (CSI) in a Long Term Evolution-Advanced (LTE-A), Cloud RAN (CRAN) configuration. The algorithm does not require detailed CSI feedback from UEs but it rather considers UE location (determined by the eNB) as the required parameter. UE throughput in the target sector is represented using a Cumulative Distributive Function (CDF). The drawn characteristics suggest that there is a significant 60% improvement in UE cell edge throughput following the application, in the coordinating cells, of the new CoMP algorithm. Results also show a further improvement of 36% in cell edge UE throughput when eNBs are centralized in a CRAN backhaul architecture. The SINR distribution of UEs in the cooperating cells has also been evaluated using a box plot. As expected, UEs with CoMP perform better demonstrating an increase of over 2 dB at the median between the transmission scenarios.

Amate, Ahmed; Milosavljevic, Milos; Kourtessis, Pandelis; Robinson, Matthew; Senior, John M.

2015-01-01

196

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

SciTech Connect

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

Citrone, P.J.

1991-01-01

197

Effect of variations of the electric field and charged-particle precipitation on the characteristics of short-wave radio signals on an auroral radio path  

Microsoft Academic Search

Data concerning the inclined sounding of the auroral ionosphere by short waves on the Linakhamari-Umba path (400 km long) during November-December 1982 are analyzed along with measurements of variations of the electric field and hard-electron fluxes. It is shown that the effects of variations of the electric field and electron fluxes on the amplitude of scattered radio signals at different

B. V. Tkachenko; A. O. Melnikov; V. K. Ridler; L. L. Lazutin; A. K. Dudakov

1985-01-01

198

Phototransistors based on InP HEMTs and their applications to millimeter-wave radio-on-fiber systems  

Microsoft Academic Search

Phototransistors based on InP high electron-mobility transistors (HEMTs) are investigated for millimeter-wave radio-on-fiber system applications. By clarifying the photodetection mechanism in InP HEMTs, the phototransistor internal gain is determined. We present their use as millimeter-wave harmonic optoelectronic mixers and characterize them at the 60-GHz band. In order to evaluate the InP HEMT optoelectronic mixer performance, internal conversion gain is introduced

Chang-Soon Choi; Hyo-Soon Kang; Woo-Young Choi; Dae-Hyun Kim; Kwang-Seok Seo

2005-01-01

199

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

NASA Astrophysics Data System (ADS)

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

Balakrishnan, G.

2015-03-01

200

The Radio & Plasma Wave Investigation (RPWI) for JUICE - Instrument Concept and Capabilities  

NASA Astrophysics Data System (ADS)

We present the concept and capabilities of the Radio & Plasma Waves Investigation (RPWI) instrument for the JUICE mission. The RPWI instrument provides measurements of plasma, electric- and magnetic field fluctuations from near DC up to 45 MHz. The RPWI sensors are four Langmuir probes for low temperature plasma diagnostics and electric field measurements, a three-axis searchcoil magnetometer for low-frequency magnetic field measurements, and a three-axial radio antenna, which operates from 80 kHz up to 45 MHz and thus gives RPWI remote sensing capabilities.. In addition, active mutual impedance measurements are used to diagnose the in situ plasma. The RPWI instrument is unique as it provides vector field measurements in the whole frequency range. This makes it possible to employ advanced diagnostics techniques, which are unavailable for scalar measurements. The RPWI instrument has thus outstanding new capabilities not previously available to outer planet missions, which and enables RPWI to address many fundamental planetary science objectives, such as the electrodynamic influence of the Jovian magnetosphere on the exospheres, surfaces and conducting oceans of Ganymede, Europa, and Callisto. RPWI will also be able to investigate the sources of radio emissions from auroral regions of Ganymede and Jupiter, in detail and with unprecedented sensitivity, and possibly also lightning. Moreover, RPWI can search for exhaust plumes from cracks on the icy moons, as well as ?m-sized dust and related dust-plasmasurface interaction processes occurring near the icy moons of Jupiter. The top-level blockdiagram of the RPWI instrument is shown here. A detailed technical description of the RPWI instrument will be given.

Bergman, J. E. S.

2013-09-01

201

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

SciTech Connect

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

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

2013-06-10

202

Radio-Frequency Downstream Plasma Production by Surface-Wave in a Very High-Permittivity Material Discharge Tube  

NASA Astrophysics Data System (ADS)

A novel method of radio-frequency surface-wave plasma production is proposed, with a particular interest in use of a very high permittivity material discharge tube. A discharge tube of TiCa-TiMg composite, which has the permittivity of 140, is employed to produce SF6 plasma by the 13.56 MHz radio-frequency power. The axial distribution of optical emission lines of fluorine shows a rapid decay, more than 5 times faster than that in quartz tube. This is because the speed of the surface-wave is reduced in a condition of very high permittivity. It is concluded that the method is innovative in use of radio-frequency power to produce downstream plasma with a very high permittivity discharge tube.

Fujiwara, Kazuya; Endo, Masakatsu; Ikeda, Yasushi; Suzuki, Tsutomu; Yanagisawa, Michihiko; Shindo, Haruo

2005-03-01

203

Optical DSB signal based mm-wave fiber-radio system using external modulation technique: ultimate performance  

Microsoft Academic Search

Optical DSB signal based mm-wave fiber-radio access system is theoretically studied. The laser phase noise effect can be eliminated simultaneously by overcoming the fiber dispersion effect, and the ASE-signal beat noise can also be reduced

Ken-ichi Kitayama

1999-01-01

204

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

Microsoft Academic Search

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

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

2008-01-01

205

A DWDM MM-wave fiber-radio system by optical frequency interleaving for high spectral efficiency  

Microsoft Academic Search

We propose a simple method for fully utilizing optical bandwidth of DWDM millimeter-wave fiber-radio systems by optical frequency interleaving. Preliminary experiment with the channel separation of only 10 GHz showed the interchannel-crosstalk induced power penalty of 2.7 dB

Hiroyuki Toda; Tsukasa Yamashita; Ken-ichi Kitayama; Toshiaki Kuri

2002-01-01

206

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 ...

207

Thermal response of the F region ionosphere in artificial modification experiments by HF radio waves  

NASA Technical Reports Server (NTRS)

The thermal response of the nighttime F region ionosphere to local heating by HF radio waves has been observed with the incoherent scatter radar at Arecibo, Puerto Rico. The observations consist of high-resolution space and time variation of the electron temperature as a high-power HF transmitter is switched on and off with a period 240 s. As soon as the HF transmitter is turned on, the electron temperature begins to rise rapidly in a narrow altitude region near 300 km, below the F2 layer peak. The electron temperature perturbation subsequently spreads over a broader altitude region. The observations are compared with the anticipated thermal response of the ionosphere based on numerical solutions of the coupled time-dependent heat conduction equations for the electron and composite ion gases and are found to be in good agreement over the entire altitude region covered by the observations.

Mantas, G. P.; Lahoz, C. H.; Carlson, H. C., Jr.

1981-01-01

208

Association of corotating magnetic sector structure with Jupiters decameter-wave radio emissions  

NASA Technical Reports Server (NTRS)

Chree (superposed epoch) analyses of Jupiter's decameter-wave radio emission taken from the new Thieman (1979) catalog show highly significant correlation with solar activity indicated by the geomagnetic Ap index. The correlation effects can be explained in terms of corotating interplanetary magnetic sector features. At times when the solar wind velocity is relatively low, about 300 to 350 km/s, a sector boundary can encounter the Earth and Jupiter almost simultaneously during the period immediately before opposition. After opposition this will not normally occur as the solar wind velocities necessary are too low. The correlation effects are much enhanced for the three apparitions of 1962-1964 during which a relatively stable and long-lived sector pattern was present. Chree analyses for this period indicate periodicities, approximately equal to half the solar rotation period, in the Jupiter data.

Barrow, C. H.

1979-01-01

209

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

PubMed

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

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

2012-05-01

210

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

211

Scintillating Stars  

NSDL National Science Digital Library

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

Bob Riddle

2003-02-01

212

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

NASA Technical Reports Server (NTRS)

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

Simons, Rainee N.; Wintucky, Edwin G.

2014-01-01

213

Size of the VELA Pulsar's Radio Emission Region: 500 Kilometers  

Microsoft Academic Search

We use interstellar scattering of the Vela pulsar to determine the size of its emission region. We find that radio-wave scattering in the Vela supernova remnant broadens the source by 3.3 +\\/- 0.2 mas x 2.0 +\\/- 0.1 mas, with the major axis at a position angle of 92 deg +\\/- 10 deg. From the modulation of the pulsar's scintillation,

C. R. Gwinn; M. J. Ojeda; M. C. Britton; J. E. Reynolds; D. L. Jauncey; E. A. King; P. M. McCulloch; J. E. J. Lovell; C. S. Flanagan; D. P. Smits; R. A. Preston; D. L. Jones

1997-01-01

214

The apparent source size of type III radio bursts: Preliminary results by the STEREO/WAVES instruments  

NASA Astrophysics Data System (ADS)

The S/WAVES instrument onboard the STEREO spacecraft measures electromagnetic waves in the solar wind. This unique project allows us to investigate properties of type III and type II radio bursts related to solar flares and propagation of coronal mass ejections (CMEs) in the interplanetary medium, respectively. We have focused on the High Frequency Receiver (HFR a part of the STEREO/WAVES instrument) which covers the frequency range 125 kHz~16.025 MHz. We present first results of a goniopolarimetric inversion for an extended source using the Singular Value Decomposition technique (SVD). We show a joint observation (including the WIND spacecraft) of the single type III radio burst connected with the X flare as a preliminary example of estimation of the apparent source size and its position.

Krupar, V.; Maksimovic, M.; Santolik, O.; Cecconi, B.; Nguyen, Q. N.; Hoang, S.; Goetz, K.

2010-03-01

215

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

216

Radio-wave propagation in the non-Gaussian interstellar medium  

E-print Network

Radio waves propagating from distant pulsars in the interstellar medium (ISM), are refracted by electron density inhomogeneities, so that the intensity of observed pulses fluctuates with time. The theory relating the observed pulse time-shapes to the electron-density correlation function has developed for 30 years, however, two puzzles have remained. First, observational scaling of pulse broadening with the pulsar distance is anomalously strong; it is consistent with the standard model only when non-uniform statistics of electron fluctuations along the line of sight are assumed. Second, the observed pulse shapes are consistent with the standard model only when the scattering material is concentrated in a narrow slab between the pulsar and the Earth. We propose that both paradoxes are resolved at once if one assumes stationary and uniform, but non-Gaussian statistics of the electron-density distribution. Such statistics must be of Levy type, and the propagating ray should exhibit a Levy flight. We propose that a natural realization of such statistics may be provided by the interstellar medium with random electron-density discontinuities. We develop a theory of wave propagation in such a non-Gaussian random medium, and demonstrate its good agreement with observations. The qualitative introduction of the approach and the resolution of the anomalous-scaling paradox was presented earlier in [PRL 91, 131101 (2003); ApJ 584, 791 (2003)].

Stanislav Boldyrev; Carl R. Gwinn

2005-08-02

217

Global and seasonal distribution of gravity wave activity in Mars' lower atmosphere derived from MGS radio occultation data  

NASA Astrophysics Data System (ADS)

Temperature profiles from Mars Global Surveyor (MGS) radio occultation measurements reveal vertical wave structures assumed to be atmospheric gravity waves in Mars' lower atmosphere. For each vertical temperature profile derived from a radio occultation measurement, wave energy density is calculated, and results are locally averaged to derive a global distribution of gravity wave activity. Global distributions are determined for all values of solar longitude and for solar longitudes corresponding to northern summer and winter to show seasonality and for vertical wavelengths less than 10 km to remove the contribution from thermal tides, which dominate in the Martian tropics at larger vertical wavelengths. The global energy density patterns show significant wave activity over the tropics and the mountainous Tharsis region averaged over all seasons and enhanced activity in northern summer compared to winter. For the most part, the observed data does not correlate well with the orographic forcing schemes used to model gravity waves in general circulation models for Mars, suggesting that wave sources other than orography play an important role on Mars.

Creasey, John E.; Forbes, Jeffrey M.; Hinson, David P.

2006-01-01

218

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

SciTech Connect

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

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

2012-03-15

219

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

PubMed

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

Balakrishnan, G

2015-03-01

220

Interstellar scintillations of pulsar radiation.  

PubMed

Time fluctuations in the intensity of pulsed radiation from CP 0834, CP 1133, AP 1237, and CP 1919 have been investigated. Power spectra, modulation indices, frequency distributions, and decorrelation frequencies are consistent with scintillation theory. If it is assumed that these scintillations are due to irregularities in the interstellar medium that travel at a velocity of 20 kilometers per second, the irregularities have a scale size on the order of 10(4) kilometers and a distance from the earth of approximately 70 parsecs. These interstellar scintillations would not have been observed if the apparent angular diameters of the pulsars were larger than 0.3 X 10(-5) second of arc, and they would cause even a point radio source to have an apparent angular diameter of approximately 10(-3) second of arc at 318 megahertz. PMID:17744967

Lang, K R

1969-12-12

221

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

222

Simulation of GPS Scintillation and TEC Using Rocket Borne Ionospheric Density Measurements  

NASA Astrophysics Data System (ADS)

Scintillations in trans-ionospheric radio signals arise as the signal propagates through naturally occurring plasma irregularities. If the receiver, satellite, or ionospheric irregularities are in motion, a time series of signal fading and phase fluctuations will occur at the receiver. It is well known that diffraction of the radio phase front produces amplitude and phase fluctuations even at GPS frequencies. Significant progress in scintillation modeling has been made since the dawn of the space age, with most of the efforts focused on statistically characterizing the plasma structure and radio wave fluctuations. In an attempt to better relate measured scintillations to the physical processes that cause them, we present results from modeling scintillation using a standard phase-screen approach but with electron density distributions measured from rocket borne Langmuir probes as input to model. The result of our model is simulated GPS phase and amplitude for a receiver on the ground, which we compare to actual GPS measurements from the Italian INGV network in the region. The ICI-2 Rocket was launched into moderate cusp irregularities on Dec 5, 2008, and measured three regions of F-region density fluctuation that appear consistent with the F-region gradient drift instability. These fluctuations caused modeled S4 of 0.2 and sigma phi of 0.1 consistent with nearby GPS measurements. One of the unexpected results of this work is that we find that the weak scintillations can cause non-physical fluctuations in TEC that peak at values as high as 2 TECU (~20 cm range error) and appear as TEC micropulsations, when indeed they are merely differenced diffraction patterns from two frequencies. This finding will be of interest to both practical GPS applications and scientists interested in using GPS to measure physical micropulsations.

Dyrud, L.; Murr, D.; Moen, J. I.; Alfonsi, L.

2010-12-01

223

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

224

Scintillation camera  

SciTech Connect

Photomultiplier tubes for converting photons converted from radiant rays by a scintillator into electric signals are severally connected to preamplifiers. The outputs of the preamplifiers are connected to weighting resistors through nonlinear amplifying circuits. The nonlinear amplifying circuit nonlinearly amplifies the output signals of each two adjacent preamplifiers in accordance with the correlation between the output signals of the preamplifiers, thereby producing two output signals.

Tomita, Y.

1981-06-16

225

Development of a portable system for checking radioactive sources using long wave radio frequency identification.  

PubMed

A portable system for automatically checking radioactive sources stored in lead containers at low temperatures was developed in order to prevent the discharging of orphan sources and contaminated materials from a controlled area to the general public. A radio frequency identification (RFID) system using a long wave in a frequency range of 125 kHz was composed of identification tags, a reader, a notebook computer, and software. ID tags without batteries were devised by using integrated circuits with an electrically erasable programmable read-only memory of 250 bytes and antennas. This software consisted of operating and maintenance functions. The read range of the ID tags was adjusted to around 5 cm in order to avoid accidental contamination and for discriminating the multiple sources. A water layer of 6.9 cm had no influence on communication between the ID tags and the reader. The data of the ID tags stored at +4, -20, and -80 degrees C were precisely read 4 mo later. The influence of lead was completely removed by separating the ID tags more than 1.6 cm from the lead. A reader can exactly identify the data of the ID tags within 6.0 cm at a velocity less than 9.0 cm s(-1). Performance of the software was verified using mock data. Nine lists concerning registered, disposed, and missing sources, etc., were displayed on the computer monitor and printed out. An RFID system using long waves proved to be applicable for routinely checking radioactive sources. PMID:17293692

Mori, K; Deji, S; Ito, S; Saze, T; Nishizawa, K

2007-03-01

226

CORISS Observations of Ionospheric Scintillation  

NASA Astrophysics Data System (ADS)

Rapid fluctuations in radio occultation (RO) signal to noise ratios and phase can signify the presence of fine scale ionospheric density irregularities along the occultation ray path. While such signatures are clearly identifiable in 1 Hz observations that are typically made at ionospheric tangent altitudes, high-rate (50 Hz) data is required to sample the full range of irregularity scale sizes responsible for L-band scintillation. At times the presence of intermediate-scale ionospheric structures can also be inferred from RO limb TEC and inverted electron density profiles, even when amplitude scintillations are not present. We present results of scintillation analysis of the first year of data from the CORISS instrument on the C/NOFS satellite, together with preliminary comparisons to scintillation data from overflights of the Air Force Research Laboratory’s ground-based SCINDA receivers that illustrate the characteristics of equatorial irregularities. Differences between scintillation indices derived from 1 Hz and 50 Hz observations will be discussed.

Straus, P. R.; Bishop, R. L.; Caton, R. G.; Groves, K. M.; Carrano, C. S.

2009-12-01

227

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

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

Asymptotic methods of calculating the propagation of centimeter radio waves in the atmosphere in space-space paths  

Microsoft Academic Search

Asymptotic methods of calculating the propagation of centimeter radio waves in a neutral atmosphere in space-space paths are\\u000a considered. The methods are based on the technique of Fourier integral operators. The approximations that allow the representation\\u000a of the corresponding operators as compositions of nonlinear coordinate changes, multiplications by reference signals, and\\u000a Fourier transformations are constructed. The approximations are based on

M. E. Gorbunov; K. B. Lauritsen

2007-01-01

230

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

E-print Network

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

Paris-Sud XI, Université de

231

Optical Tandem Single-Sideband-Based WDM Interface for Millimeter-Wave Fiber-Radio Multisector Antenna Base Station  

Microsoft Academic Search

We propose and demonstrate a spectrally efficient wavelength division multiplexed (WDM) optical interface for millimeter-wave radio access networks with the capability of being integrated within a standard 100-GHz WDM infrastructure. The proposed WDM optical interface is realized by the use of a multiport optical circulator in conjunction with fiber Bragg grating filters. The interface supports demultiplexing of wavelength-interleaved optical tandem

Prasanna Gamage; Ampalavanapillai Nirmalathas; Christina Lim; Dalma Novak; Rodney Waterhouse

2009-01-01

232

Relativistic blast-wave model for the rapid flux variations of AO 0235+164 and other compact radio sources  

NASA Technical Reports Server (NTRS)

A relativistic blast-wave version of a signal-screen model is developed which can adequately explain the details of the flux-density and structural variations of compact extragalactic radio sources. The relativistic motion implied by flux variations is analyzed with respect to the synchrotron spectrum of the BL Lac object AO 0235+164 observed during outbursts, and a signal-screen model for rapidly expanding shells produced by ultrarelativistic blast waves is examined. The approximate observed structure of the blast wave at three stages in its evolution is illustrated, each stage is described, and the model is applied to the flux density outburst in AO 0235+164 observed in late 1975. The results show that a relativistic blast-wave model can in general reproduce the main features of the observed flux variations in compact sources. Some problems with the proposed model are briefly discussed.

Marscher, A. P.

1978-01-01

233

The application of the WKB approximation to the calculation of the scattering of radio waves from overdense meteor trains  

NASA Astrophysics Data System (ADS)

The possibility of describing the scattering of radio waves at normal incidence from intense meteor trains by a short wavelength approximation is investigated. The electromagnetic fields are expanded in cylindrical waves and the Wentzel-Kramers-Brillouin (WKB) approximation is applied to the individual differential equations for the partial waves. The results are confirmed by applying the phase integral method to ingoing and outgoing cylindrical waves as described by Hankel functions in the Debye-Watson representation. The use of WKB or phase integral method is illustrated by calculating the magnitude of the reflection coefficient for initial line densities of 10 exp 15, 10 exp 16, and 10 exp 17 per m. The results obtained are compared with the predictions of the metallic cylinder model (MCM), the only model available for the estimation of echo durations from overdense trains. This model is found to be reasonable for backscatter, but in general gives poor results when applied to forward scatter.

Jones, W.

1992-11-01

234

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

Microsoft Academic Search

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

M. Dryer; A. Maxwell

1979-01-01

235

Radio frequency radiation of millimeter wave length: potential occupational safety issues relating to surface heating.  

PubMed

Currently, technology is being developed that makes use of the millimeter wave (MMW) range (30-300 GHz) of the radio frequency region of the electromagnetic spectrum. As more and more systems come on line and are used in everyday applications, the possibility of inadvertent exposure of personnel to MMWs increases. To date, there has been no published discussion regarding the health effects of MMWs; this review attempts to fill that void. Because of the shallow depth of penetration, the energy and, therefore, heat associated with MMWs will be deposited within the first 1-2 mm of human skin. MMWs have been used in states of the former Soviet Union to provide therapeutic benefit in a number of diverse disease states, including skin disorders, gastric ulcers, heart disease and cancer. Conversely, the possibility exists that hazards might be associated with accidental overexposure to MMWs. This review attempts to critically analyze the likelihood of such acute effects as burn and eye damage, as well as potential long-term effects, including cancer. PMID:10647983

Ryan, K L; D'Andrea, J A; Jauchem, J R; Mason, P A

2000-02-01

236

Radio Ghosts  

E-print Network

We investigate the possibility that patches of old radio plasma (`radio ghosts') of former radio galaxies form a second distinct phase of the inter-galactic medium (IGM), not mixed with the thermal gas. The separation of this phase from the ambient gas and its resistance against eroding turbulent forces is given by magnetic fields, which are expected to be roughly in pressure equilibrium with the surrounding medium. Since patches of this plasma are largely invisible in the radio we use the term `radio ghost' to characterize their nature. Possibilities and difficulties of different detection strategies of ghosts are discussed. These involve radio emission, cosmic microwave background (CMB) and starlight Comptonization, and Faraday rotation. Re-activation of the electron population in shock waves of cosmological structure formation, which seems to lead to the cluster radio relic phenomena. We discuss the role radio ghosts can have: They are able to store relativistic particles for cosmological times, but are al...

Ensslin, T A

1999-01-01

237

Global ionospheric effects of geomagnetic storm on May 2-3, 2010 and their influence on HF radio wave propagation  

NASA Astrophysics Data System (ADS)

In this work we have investigated the global ionospheric response to geomagnetic storm on May 2-3, 2010 using GSM TIP (Global Self-consistent Model of the Thermosphere, Ionosphere and Protonosphere) simulation results. In the GSM TIP storm time model runs, several input parameters such as cross-polar cap potential difference and R2 FAC (Region 2 Field-Aligned Currents) varied as a function of the geomagnetic activity AE-index. Current simulation also uses the empirical model of high-energy particle precipitation by Zhang and Paxton. In this model, the energy and energy flux of precipitating electrons depend on a 3 hour Kp-index. We also have included the 30 min time delay of R2 FAC variations with respect to the variations of cross-polar cap potential difference. In addition, we use the ground-based ionosonde data for comparison our model results with observations. We present an analysis of the physical mechanisms responsible for the ionospheric effects of geomagnetic storms. The obtained simulation results are used by us as a medium for HF radio wave propagation at different latitudes in quiet conditions, and during main and recovery phase of a geomagnetic storm. To solve the problem of the radio wave propagation we used Zakharov's (I. Kant BFU) model based on geometric optics. In this model the solution of the eikonal equation for each of the two normal modes is reduced using the method of characteristics to the integration of the six ray equation system for the coordinates and momentum. All model equations of this system are solved in spherical geomagnetic coordinate system by the Runge-Kutta method. This model was tested for a plane wave in a parabolic layer. In this study, the complex refractive indices of the ordinary and extraordinary waves at ionospheric heights was calculated for the first time using the global first-principal model of the thermosphere-ionosphere system that describes the parameters of an inhomogeneous anisotropic medium during a geomagnetic storm. A comparison of the ordinary and extraordinary modes of HF radio ray paths in quiet and disturbed conditions has been done. We considered in more detail the features of the radio ray paths in the presence of F3 layer in the equatorial ionosphere, the main ionospheric trough and tongue of ionization at high latitudes. It is shown that the results obtained with use of radio propagation and GSM TIP models adequately describe HF radio ray paths in the Earth's ionosphere and can be used in applications. These investigations were carried out at financial support of Russian Foundation for Basic Research (RFBR) - Grant # 12-05-31217 and RAS Program 22.

Kotova, Daria; Klimenko, Maxim; Klimenko, Vladimir; Zakharov, Veniamin

2013-04-01

238

The Equatorial Scintillations and Space Weather Effects on its Generation during Geomagnetic Storms  

NASA Astrophysics Data System (ADS)

Great diversity of the ionospheric phenomena leads to a variety of irregularity types with spatial size from many thousands of kilometers to few centimeters and lifetimes from days to fractions of second. Since the ionosphere strongly influences the propagation of radio waves, signal distortions caused by these irregularities affect short-wave transmissions on Earth, transiono-spheric satellite communications and navigation. In this work the solar wind and the equatorial ionosphere parameters, Kp, Dst, AU, AL indices characterized contribution of different mag-netospheric and ionospheric currents to the H-component of geomagnetic field are examined to test the space weather effect on the generation of ionospheric irregularities producing VLF scintillations. According to the results of the current statistical studies, one can predict scintil-lations from Aarons' criteria using the Dst index, which mainly depicts the magnetospheric ring current field. To amplify Aarons' criteria or to propose new criteria for predicting scintillation characteristics is the question. In the present phase of the experimental investigations of elec-tron density irregularities in the ionosphere new ways are opened up because observations in the interaction between the solar wind -magnetosphere -ionosphere during magnetic storms have progressed greatly. We have examined scintillation relation to magnetospheric and ionospheric currents and show that the factor, which presents during magnetic storms to fully inhibit scin-tillation, is the positive Bz-component of the IMF. During the positive Bz IMF F layer cannot raise altitude where scintillations are formed. The auroral indices and Kp do better for the prediction of the ionospheric scintillations at the equator. The interplanetary magnetic field data and models can be used to explain the relationship between the equatorial ionospheric parameters, h'F, foF2, and the equatorial geomagnetic variations with the polar ionosphere cur-rents and the solar wind. Taking into account the time delay between the solar wind and the ionosphere phenomena, the relationship between the solar wind and the ionosphere parameters can be used for predicting of scintillations.

Biktash, Lilia

239

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

NASA Technical Reports Server (NTRS)

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

Manning, Robert M.

2008-01-01

240

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

241

A Investigation of the Polar Electrojet Current System Using Radio Wave Heating of the Lower Ionosphere  

NASA Astrophysics Data System (ADS)

The HIgh Power Auroral Stimulation (HIPAS) heating facility has been used to modulate D-region ionospheric currents at high latitudes, producing extremely low frequency (ELF) radio wave emissions. The behavior of these ionospheric currents can be deduced from a comprehensive study of the ELF signals received at a local field site. This document examines the relationship between the ELF magnetic field strength measured on the ground and the intensity of an overhead electrojet current. The mapping of the polar electrojet current from the E region down through the D region, where it can then be modulated by the heater beam, is investigated. A finite difference solution to the electrojet mapping problem is presented in which arbitrary conductivity profiles can be specified. Results have been obtained using a simple Cowling model of the electrojet. These results indicate that for an electrojet flowing at an altitude of 110 km with a scale size in excess of 100 km, the mapping of the horizontal current density can be completely characterized in terms of the Pedersen and Hall conductivities. This indicates that the mapping becomes independent of scale sizes which exceed 100 km. The downward mapping of the electrojet current and associated electric field in the presence of ionospheric conductivity irregularities has been studied. It was demonstrated that D region conductivity irregularities do not significantly change the downward mapping of ionospheric electric fields. However, these conductivity irregularities were found to have a major influence upon the downward mapping of ionospheric currents. A promising new diagnostic technique, for studying ionospheric D region currents, has been implemented using the HIPAS facility. This technique involves HF beam steering for localized ELF generation in the mapped region below electrojets. Beam steering has been used to deduce the strength and current distribution of the polar electrojet, and for charting the movements of overhead currents.

Werner, Douglas Henry

242

The Standing Wave Phenomenon in Radio Telescopes; Frequency Modulation of the WSRT Primary Beam  

E-print Network

Inadequacies in the knowledge of the primary beam response of current interferometric arrays often form a limitation to the image fidelity. We hope to overcome these limitations by constructing a frequency-resolved, full-polarization empirical model for the primary beam of the Westerbork Synthesis Radio Telescope (WSRT). Holographic observations, sampling angular scales between about 5 arcmin and 11 degrees, were obtained of a bright compact source (3C147). These permitted measurement of voltage response patterns for seven of the fourteen telescopes in the array and allowed calculation of the mean cross-correlated power beam. Good sampling of the main-lobe, near-in, and far-side-lobes out to a radius of more than 5 degrees was obtained. A robust empirical beam model was detemined in all polarization products and at frequencies between 1322 and 1457 MHz with 1 MHz resolution. Substantial departures from axi-symmetry are apparent in the main-lobe as well as systematic differences between the polarization properties. Surprisingly, many beam properties are modulated at the 5 to 10% level with changing frequency. These include: (1) the main beam area, (2) the side-lobe to main-lobe power ratio, and (3) the effective telescope aperture. These semi-sinusoidsal modulations have a basic period of about 17 MHz, consistent with the natural 'standing wave' period of a 8.75 m focal distance. The deduced frequency modulations of the beam pattern were verified in an independent long duration observation using compact continuum sources at very large off-axis distances. Application of our frequency-resolved beam model should enable higher dynamic range and improved image fidelity for interferometric observations in complex fields. (abridged)

Attila Popping; Robert Braun

2007-12-14

243

Midlatitude scintillation model. Technical report, 1 November 1985-31 October 1986  

Microsoft Academic Search

Radiowave scintillation in the presence of ionospheric disturbances has the potential to disrupt numerous transionospheric radio and radar systems. This report describes development of a model characterizing the plasma density irregularities that produce scintillation in the naturally disturbed mid-latitude F layer. The model will be incorporated into Program WBMOD, which includes subroutines for computing both link geometry and scintillation indices,

R. E. Robins; J. A. Secan; E. J. Fremouw

1986-01-01

244

On The Brightness and Waiting-Time Distributions of a Type III Radio Storm Observed By Stereo/Waves  

NASA Astrophysics Data System (ADS)

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

Eastwood, J. P.; Wheatland, M. S.; Hudson, H. S.; Krucker, S.; Bale, S. D.; Maksimovic, M.; Goetz, K.; Bougeret, J.-L.

2010-01-01

245

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

SciTech Connect

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

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

2010-01-10

246

On the Brightness and Waiting-time Distributions of a Type III Radio Storm observed by STEREO/WAVES  

E-print Network

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

Eastwood, J P; Hudson, H S; Krucker, S; Bale, S D; Maksimovic, M; Goetz, K; Bougeret, J -L

2009-01-01

247

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

NASA Astrophysics Data System (ADS)

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

Tanikawa, Takahiro; Chiba, Masami; Kamijo, Toshio; Yabuki, Fumiaki; Yasuda, Osamu; Akiyama, Hidetoshi; Chikashige, Yuichi; Kon, Tadashi; Shimizu, Yutaka; Utsumi, Michiaki; Fujii, Masatoshi

2012-11-01

248

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

SciTech Connect

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

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

2012-11-12

249

Measurements of Antenna Surface for a Millimeter-Wave Space Radio Telescope II; Metal Mesh Surface for Large Deployable Reflector  

E-print Network

Large deployable antennas with a mesh surface woven by fine metal wires are an important technology for communications satellites and space radio telescopes. However, it is difficult to make metal mesh surfaces with sufficient radio-frequency (RF) performance for frequencies higher than millimeter waves. In this paper, we present the RF performance of metal mesh surfaces at 43 GHz. For this purpose, we developed an apparatus to measure the reflection coefficient, transmission coefficient, and radiative coefficient of the mesh surface. The reflection coefficient increases as a function of metal mesh surface tension, whereas the radiative coefficient decreases. The anisotropic aspects of the reflection coefficient and the radiative coefficient are also clearly seen. They depend on the front and back sides of the metal mesh surface and the rotation angle. The transmission coefficient was measured to be almost constant. The measured radiative coefficients and transmission coefficients would cause significant degr...

Kamegai, Kazuhisa

2012-01-01

250

Climatology of GNSS ionospheric scintillation at high latitudes  

NASA Astrophysics Data System (ADS)

Under perturbed conditions caused by intense solar wind magnetosphere coupling, the ionosphere may become highly turbulent and irregularities, typically enhancements or depletions of the electron density embedded in the ambient ionosphere, can form. Such irregularities cause diffraction effects, mainly due to the random fluctuations of the refractive index of the ionosphere, on the satellites signals passing through them and consequent perturbations may cause GNSS navigation errors and outages, abruptly corrupting its performance. Due to the morphology of the geomagnetic field, whose lines are almost vertical at high latitude, polar areas are characterized by the presence of significant ionospheric irregularities having scale sizes ranging from hundreds of kilometers down to a few centimeters and with highly dynamic structures. The understanding of the effect of such phenomena is important, not only in preparation for the next solar cycle (24), whose maximum is expected in 2012, but also for a deeper comprehension of the dynamics of the high-latitude ionosphere. We analyze the fluctuations in the carrier frequency of the radio waves received on the ground, commonly referred to as ionospheric amplitude and phase scintillations, to investigate the physical processes causing them. The phase scintillations on GNSS signals are likely caused by ionospheric irregularities of scale size of hundreds of meters to few kilometers. The amplitude scintillations on GNSS signals are caused by ionospheric irregularities of scale size smaller than the Fresnel radius, which is of the order of hundreds of meters for GNSS signals, typically embedded into the patches. The Istituto Nazionale di Geofisica e Vulcanologia (INGV) and the Institute of Engineering Surveying and Space Geodesy (IESSG) of the University of Nottingham manage the same kind of GISTM (GPS Ionospheric Scintillation and TEC Monitor) receivers over the European high and mid latitude regions and over Antarctica. The GISTM receivers consist of NovAtel OEM4 dual-frequency receivers with special firmware specifically able to compute in near real time the amplitude and the phase scintillation from the GPS L1 frequency signals, and the ionospheric TEC (Total Electron Content) from the GPS L1 and L2 carrier phase signals. From this ground-based network, we are able to capture the dynamics of ionospheric plasma in a wide latitudinal range, from auroral to cusp/cap regions, considering the contribution of both hemispheres, in a bi-polar framework. The data collection started in 2001 and is still in progress. The results, obtained by statistically analyzing a large data sample over a wide period, show the effect of ionospheric disturbances on the GNSS signals, evidencing the different contributions of the auroral and the cusp/cap ionosphere and highlighting possible scintillation scenarios over polar regions.

Spogli, L.; Alfonsi, L.; de Franceschi, G.; Romano, V.; Aquino, M.; Dodson, A.; Mitchell, C. N.

2009-12-01

251

Multiplexing of millimeter-wave signals for fiber-radio links by direct modulation of a two-mode locked Fabry-Pe´rot laser  

Microsoft Academic Search

In this paper, we introduce generation of multiplexed signals on the millimeter-wave bands for fiber-radio systems where an optical millimeter-wave generator is based on a two-mode locked Fabry-Pe´rot (FP) slave laser, whose injection current is directly modulated by a signal source. We qualitatively consider the distortion of the millimeter-wave signals from the FP slave laser. The distortion components on the

Masahiro Ogusu; Keizo Inagaki; Yoshihiko Mizuguchi; Takashi Ohira

2004-01-01

252

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

NASA Astrophysics Data System (ADS)

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

Forte, B.

2012-08-01

253

Asymptotic methods of calculating the propagation of centimeter radio waves in the atmosphere in space-space paths  

NASA Astrophysics Data System (ADS)

Asymptotic methods of calculating the propagation of centimeter radio waves in a neutral atmosphere in space-space paths are considered. The methods are based on the technique of Fourier integral operators. The approximations that allow the representation of the corresponding operators as compositions of nonlinear coordinate changes, multiplications by reference signals, and Fourier transformations are constructed. The approximations are based on a technical procedure using a linearized canonical transform. This approach makes it possible to devise fast numerical algorithms. Numerical simulations are conducted with the use of realistic global gridded fields of meteorological parameters including the turbulence. The numerical simulations show high accuracy and efficiency of the proposed methods.

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

2007-12-01

254

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

255

A survey of key-enabling components for remote millimetric wave generation in radio over fiber networks  

NASA Astrophysics Data System (ADS)

Radio over fiber systems have emerged as a cost effective solution for future multigigabit wireless networks operating at millimetric bands. Such networks are composed of three subsystems: central station, optical distribution network, and base stations, whose performance and architecture rely on key-enabling components. This issue is particularly significant for components located at the central station since it is there where the downlink optical signal is generated, which after detection in a simple base station, results in the desired mm-wave signal. This paper reviews the state-of-the-art components required in the most relevant remote mm-wave generation techniques, such as high-speed analog lasers, broad-bandwidth modulators, multiwavelength sources, and narrow-linewidth lasers, giving special attention to their performance in terms of reconfigurability, energy efficiency, and integrability. The different technologies for each key-enabling component are presented and compared, proposing the most promising candidates and some future research opportunities.

Aldaya, Ivan; Beas, Joaquín; Castañón, Gerardo; Campuzano, Gabriel; Aragón-Zavala, Alejandro

2013-07-01

256

A Multiple-Scan Focusing Method for Radio Frequency Bulk Acoustic Wave Device Observation by Laser Probe System  

NASA Astrophysics Data System (ADS)

This paper proposes a focusing method based on multiple scanning of a device surface to be observed, which is particularly-suitable for a fast-mechanical-scanning and phase-sensitive laser probe for radio frequency (RF) surface and bulk acoustic wave (SAW/BAW) devices. When high spatial resolution is required for the observation, one needs an objective lens of large magnifying power with extremely shallow focal depth. Accordingly, an uneven surface and tiny inclination of a BAW device cause acquired images a considerable defocus, by which it is difficult to obtain precise and reliable field quantities related to acoustic waves in the device. The proposed method is shown to be most effective in avoiding this sort of defocus and able to focus the entire surface. By this method, for example, we could clearly observe power leakage in an FBAR structure.

Nan Wu,; Ken-ya Hashimoto,; Tatsuya Omori,; Masatsune Yamaguchi,

2010-07-01

257

Comparison of the FSI and CT retrieval methods based on simulations from a radio occultation wave optics simulator  

NASA Astrophysics Data System (ADS)

GPS/MET and CHAMP experiments showed that measurements of GPS (Global Positioning System) radio signals by a satellite in a low-Earth orbit (LEO) are a valuable source of information about meteorological parameters such as refractivity, temperature, pressure, and water vapour. Until recently, processing signals in multipath zones was considered a very significant problem. In our work we compare two methods, which are capable of disentangling multiple rays in multipath regions in the lower troposphere: 1) the Canonical Transform (CT) method and 2) the Full Spectrum Inversion Method (FSI), which was recently introduced. We show that these methods are closely related and can be explained from two view points: 1) both methods apply a Fourier transform-like operator to the entire radio occultation signal, and the derivative of the phase of transformed signal is the used for the computation of bending angles, 2) they can be explained from signal processing view point as the location of multiple tones constituting the complete signal. An advantage of FSI is that it is computationally simple and thus easy to implement. We investigated the relative performance of the two methods in simulations using a wave optics propagator. We used simple analytical models of the atmospheric refractivity as well as radio sonde data in order to reproduce complex multipath situations. The simulations as well as analytical estimations indicate that a resolution of 50 m can be obtained.

Benzon, H.-H.; Gorbunov, M. E.; Jensen, A. S.; Lohmann, M. S.; Nielsen, A. S.

2003-04-01

258

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

259

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

PubMed Central

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

TSUDA, Toshitaka

2014-01-01

260

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

NASA Astrophysics Data System (ADS)

Spangler and Reynolds compared H-alpha intensities, measured using the Wisconsin Fabry-Perot interferometer, with radio-wave scattering sizes of eight extragalactic sources along low-latitiude lines of sight. They find that some correlation exists between scattering and H-alpha intensity, as one might expect. However, the H-alpha observations were made with a 50(') beam size; higher resolution observations might provide a more accurate measure of the intensity along the scattering line of sight. We made sensitive, arcminute resolution H-alpha images of the same fields to upgrade the accuracy of their results. We find that many of their measured H-alpha intensities are accurate, but some of the higher intensities are biased upward by the presence of clumped emission. Appropriate reduction of these large intensities increases the degree of correlation between scattering and H-alpha intensity, thus strengthening their original conclusions. This work is a first step towards using our spectral-line imaging system for a more extensive study of the relationship between the warm ionized medium and scattering of radio waves. This research was supported by NSF grant AST-9319670 and a grant from the Horton Foundation to Virginia Tech.

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

1995-12-01

261

Seismo-electromagnetic phenomenon in terms of 3D vector problem of subionospheric radio wave propagation across the solar terminator  

NASA Astrophysics Data System (ADS)

This paper presents a further development of mathematical model, an asymptotic theory and an appropriate numerical algorithm to study the vector VLF point source field propagation problem within the non-uniform Earth-ionosphere waveguide. It is the sequential development of our previous article [Soloviev, O.V., Hayakawa, M., Ivanov, V.I., Molchanov, O.A., 2004. Seismo-electromagnetic phenomenon in the atmosphere in terms of 3D subionospheric radio wave propagation problem. Phys. Chem. Earth 29, 639-647. doi:10.1016/j.pce.2003.10.002]. We have taken into account 3D local anisotropic ionosphere inhomogeneity over the ground of the solar terminator transition. The local ionosphere inhomogeneity, whose centre is situated above the model earthquake, is simulated by a bell-shaped tensor impedance perturbation of the ionospheric waveguide wall. The various propagation paths, which cut across the terminator line at different angles, have been investigated. Numerical results show that the emergence of the local ionosphere inhomogeneity on the radio wave propagation across the solar terminator path deforms the curves of field amplitude and phase diurnal variations in accord with the experimental observational data.

Soloviev, O. V.; Hayakawa, M.; Molchanov, O. A.

262

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

E-print Network

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

Sukanta Panda; Subhendra Mohanty; Padmanabhan Janardhan; Oscar Stål

2007-08-13

263

Ionospheric scintillation studies  

NASA Technical Reports Server (NTRS)

The diffracted field of a monochromatic plane wave was characterized by two complex correlation functions. For a Gaussian complex field, these quantities suffice to completely define the statistics of the field. Thus, one can in principle calculate the statistics of any measurable quantity in terms of the model parameters. The best data fits were achieved for intensity statistics derived under the Gaussian statistics hypothesis. The signal structure that achieved the best fit was nearly invariant with scintillation level and irregularity source (ionosphere or solar wind). It was characterized by the fact that more than 80% of the scattered signal power is in phase quadrature with the undeviated or coherent signal component. Thus, the Gaussian-statistics hypothesis is both convenient and accurate for channel modeling work.

Rino, C. L.; Freemouw, E. J.

1973-01-01

264

Scintillators and applications thereof  

DOEpatents

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

Williams, Richard T.

2014-07-15

265

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

ERIC Educational Resources Information Center

This article describes one of the first developments and deployment of radio for distance learning and education in Canada, beginning in the early 1920s. Anticipating a recent initiative of public-private partnerships, the impetus, infrastructure, and initial programs were provided by a large corporation. Description of the system, its purpose,…

Buck, George H.

2006-01-01

266

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

267

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

268

Receiving and transmitting light-like radio waves: Antenna effect in arrays of aligned carbon nanotubes  

Microsoft Academic Search

We present optical measurements of random arrays of aligned carbon nanotubes, and show that the response is consistent with conventional radio antenna theory. We first demonstrate the polarization effect, the suppression of the reflected signal when the electric field of the incoming radiation is polarized perpendicular to the nanotube axis. Next, we observe the interference colors of the reflected light

Y. Wang; K. Kempa; B. Kimball; J. B. Carlson; G. Benham; W. Z. Li; T. Kempa; J. Rybczynski; A. Herczynski; Z. F. Ren

2004-01-01

269

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

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

270

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

271

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

272

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

273

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

Microsoft Academic Search

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

M. E. Gorbunov; K. B. Lauritsen

2004-01-01

274

Cyclotron wave instability in the corona and origin of solar radio emission with fine structure  

Microsoft Academic Search

The longitudinal waves (Bernstein modes and plasma waves near the hybrid frequency) in a mixture of equilibrium coronal plasma and a small group of energetic electrons are investigated. The energetic electrons have a nonequilibrium momentum distribution inherent in trapped particles. The frequency dependence of the cyclotron instability increments is studied. Attention is paid to a significant role of the relativistic

V. V. Zheleznyakov; E. Ya. Zlotnik

1975-01-01

275

Radio Ghosts  

E-print Network

We investigate the possibility that patches of old radio plasma (`radio ghosts') of former radio galaxies form a second distinct phase of the inter-galactic medium (IGM), not mixed with the thermal gas. The separation of this phase from the ambient gas and its resistance against eroding turbulent forces is given by magnetic fields, which are expected to be roughly in pressure equilibrium with the surrounding medium. Since patches of this plasma are largely invisible in the radio we use the term `radio ghost' to characterize their nature. Possibilities and difficulties of different detection strategies of ghosts are discussed. These involve radio emission, cosmic microwave background (CMB) and starlight Comptonization, and Faraday rotation. Re-activation of the electron population in shock waves of cosmological structure formation, which seems to lead to the cluster radio relic phenomena. We discuss the role radio ghosts can have: They are able to store relativistic particles for cosmological times, but are also able to release them under the influence of very strong turbulence. This might happen during a major merger event of clusters of galaxies. The released relativistic proton population could produce the observed radio halos of some cluster of galaxies via hadronic reactions with the background gas leading to the production of secondary electrons and positrons. Destroyed ghosts, mixed with the IGM can help to magnetize it. Finally, the strong field strength within ghosts should have a significant impact on the propagation of extragalactic high energy cosmic rays.

Torsten A. Ensslin

1999-06-11

276

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

277

Primary and secondary scintillation measurements in a xenon Gas Proportional Scintillation Counter  

E-print Network

NEXT is a new experiment to search for neutrinoless double beta decay using a 100 kg radio-pure high-pressure gaseous xenon TPC. The detector requires excellent energy resolution, which can be achieved in a Xe TPC with electroluminescence readout. Hamamatsu R8520-06SEL photomultipliers are good candidates for the scintillation readout. The performance of this photomultiplier, used as VUV photosensor in a gas proportional scintillation counter, was investigated. Initial results for the detection of primary and secondary scintillation produced as a result of the interaction of 5.9 keV X-rays in gaseous xenon, at room temperature and at pressures up to 3 bar, are presented. An energy resolution of 8.0% was obtained for secondary scintillation produced by 5.9 keV X-rays. No significant variation of the primary scintillation was observed for different pressures (1, 2 and 3 bar) and for electric fields up to 0.8 V cm-1 torr-1 in the drift region, demonstrating negligible recombination luminescence. A primary scintillation yield of 81 \\pm 7 photons was obtained for 5.9 keV X-rays, corresponding to a mean energy of 72 \\pm 6 eV to produce a primary scintillation photon in xenon.

L. M. P. Fernandes; E. D. C. Freitas; M. Ball; J. J. Gómez-Cadenas; C. M. B. Monteiro; N. Yahlali; D. Nygren; J. M. F. dos Santos

2010-09-15

278

Internal wave activity in the polar atmospheric regions during 2006 - 2009 revealed by COSMIC radio occultation data  

NASA Astrophysics Data System (ADS)

The satellite mission Formosat-3/COSMIC (Constellation Observing System for Meteorology, Ionosphere and Climate) consists of six micro-satellites, and each of them has four GPS-antennas. It was launched in April 2006, orbiting around the Earth at approximately 800 km. The primary scientific goal of the mission is to demonstrate the value of near-real-time radio occultation (RO) observations in improving operational numerical weather predictions (NWP). The goal is readily shown by assimilating the measurements of atmospheric parameters into used NWP-models. These parameters include density, temperature, pressure and relative humidity fields in the atmosphere. An analysis of their geographic and seasonal distributions is necessary to the understanding of the energy and momentum transfer and the reaction of the polar atmosphere in response to global warming. This task is especially important as the Polar Regions are very sensitive to the change in global temperature and it may be a major cause of global sea level rising. In this work, a statistical analysis of the internal gravity wave (IGW) activity in polar atmospheric regions (latitudes more than 60º) using Formosat-3/COSMIC RO temperature data collected from July 2006 to March 2009 has been performed. Geographic and seasonal distributions of the IGW potential energy (wave activity indicator) in the altitude interval from 15 to 35 km have been determined and analyzed. The obtained results show that the wave activity in the polar atmosphere is strong in winter and spring. The potential energy of IGWs in spring is largest in Antarctic atmospheric region, while it is largest in winter in Arctic region. The wave potential energy increases with altitude up to 35 km in the atmosphere of both Earth’s hemispheres. In Antarctic region, internal waves with high potential energy occur in the atmosphere over the Antarctic Peninsula. In Arctic region, a high wave activity is mainly observed over North Atlantic Ocean (Iceland) and Scandinavian Peninsula. In this work, the results of an analysis of the wave activity and factors influencing upon it in the polar stratosphere of Arctic and Antarctic have been presented and discussed. A statistical analysis of the IGW activity in Polar Regions (latitudes more than 60º) of the Earth’s atmosphere using Formosat-3/COSMIC RO temperature data collected from July 2006 to March 2009 is performed. Geographic and seasonal distributions of the IGW potential energy per unit mass (wave activity indicator) in the altitude interval from 15 to 35 km are determined and analyzed. This work was partially supported by the RFBR grant 13-02-00526-? and Program 22 of the RAS Presidium.

Kirillovich, Ivan; Gubenko, Vladimir; Pavelyev, Alexander; Liou, Yuei-An

279

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

NASA Technical Reports Server (NTRS)

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

Scudder, Jack D.

1992-01-01

280

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

281

Scintillator reflective layer coextrusion  

DOEpatents

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

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

2001-01-01

282

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

NASA Astrophysics Data System (ADS)

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

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

283

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

284

Measuring solar wind velocity with spacecraft phase scintillations  

NASA Technical Reports Server (NTRS)

The measurement of spacecraft phase scintillations with a coherent dual-frequency radio system permits solar-wind velocity measurements based on multiple-station phase scintillations. Advantages of measuring solar-wind velocity on the basis of multiple-station phase scintillations are discussed with respect to amplitude scintillations. These advantages include the ability to carry out observations closer to the sun, a much wider range of possible baselines, a lower S/N ratio for long-baseline phase measurements, and a wider range of antenna sizes and receiver noise temperatures. NASA antennas particularly suitable for these measurements are identified, and observations with the coherent S/X radio system aboard various NASA spacecraft intended for deep-space missions are proposed.

Woo, R.

1977-01-01

285

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

NASA Astrophysics Data System (ADS)

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 of coaxial step-disc-loaded structure is the broadest. The calculation results show that increasing the step width and decreasing the step thickness can improve the bandwidth.

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

2005-03-01

286

Millimeter-wave InP\\/InGaAs HPT optoelectronic mixers and their application to 60GHz bi-directional radio-on-fiber systems  

Microsoft Academic Search

We demonstrate the use of InP\\/InGaAs heterojunction phototransistors as optoelectronic mixers for bi-directional millimeter-wave band radio-on-fiber systems. For downlink transmission, optically transmitted IF signals are frequency up-converted to millimeter-wave band signals in InP HPT optoelectronic mixer with remotely-fed optical local oscillator (LO) signals. Uplink signals at millimeter-wave band are applied to the base port of InP HPT and frequency down-converted

Chang-Soon Choi; Jae-Young Kim; Woo-Young Choi; Hideki Kamitsuna; Minoru Ida; Kenji Kurishima

2005-01-01

287

CIGALA: an FP7 innovative activity to tackle the threat of Ionospheric Scintillation to GNSS operations in Latin America  

NASA Astrophysics Data System (ADS)

Drifting ionospheric electron density irregularities may lead to the scintillation of transionospheric radio waves, as in the case of signals broadcast from artificial satellites. Scintillations can not only degrade signal quality but also cause receiver loss of lock on GNSS satellites, therefore posing a major threat to GNSS based applications demanding high levels of accuracy, availability and integrity, including EGNOS-based applications notably in low latitude areas. The problem is particularly acute in Latin America and will be further amplified with the next solar maximum, predicted for 2013. The CIGALA (Concept for Ionospheric Scintillation Mitigation for Professional GNSS in Latin America) project, led by Septentrio NV and co-funded by the European GNSS Supervisory Authority (GSA) through the European 7th Framework Program, will tackle this problem. The aim of the CIGALA project is to develop ionospheric scintillation mitigation countermeasures to be implemented in Septentrio's professional multi-frequency multi-constellation GNSS receivers and tested in Latin America. The project will leverage research and development activities coordinated between European and Brazilian experts and will involve a wide scale ionospheric measurement and test campaigns that will be conducted in Brazil with the support of several local academic and industrial partners. Details on the objectives, current status, and workflow of the project will be presented and discussed.

Francisco Galera Monico, João.; Bougard, Bruno; Sleewaegen, Jean-Marie; Willems, Tom; Saüt, Carine; Aquino, Marcio; de Franceschi, Giorgiana; Ferreira da Silva, Elcia; Forte, Biagio; Wernik, Andrzej W.

2010-05-01

288

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

289

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

290

Numerical modelling of VLF radio wave propagation through earth-ionosphere waveguide and its application to sudden ionospheric disturbances  

E-print Network

In this thesis, we theoretically predict the normal characteristics of Very Low Frequency (3~30 kHz) radio wave propagation through Earth-ionosphere waveguide corresponding to normal behavior of the D-region ionosphere. We took the VLF narrow band data from the receivers of Indian Centre for Space Physics (ICSP) to validate our models. Detection of sudden ionospheric disturbances (SIDs) are common to all the measurements. We apply our theoretical models to infer the D-region characteristics and to reproduce the observed VLF signal behavior corresponding to such SIDs. We develop a code based on ray theory to simulate the diurnal behavior of VLF signals over short propagation paths (2000~3000 km). The diurnal variation from this code are comparable to the variation obtained from a more general Long Wave Propagation Capability (LWPC) code which is based on mode theory approach. We simulate the observational results obtained during the Total Solar Eclipse of July 22, 2009 in India. We also report and simulate a h...

Pal, Sujay

2015-01-01

291

The Propagation of Radio Waves over the Surface of the Earth and in the Upper Atmosphere  

Microsoft Academic Search

Simple formulas and graphs are given which represent the ground-wave field intensity at the surface of the earth as radiated from a short vertical antenna at the surface of the earth. The theory is compared to some experimental results reported by other investigators to determine its range of application. The diffraction formula given is theoretically valid only at the lower

K. A. Norton

1936-01-01

292

GEMS: Invisible Universe: The Electromagnetic Spectrum from Radio Waves to Gamma Rays  

NSDL National Science Digital Library

This guide introduces students to the mystery of gamma-ray bursts as a gateway and motivation for gaining fundamental understandings of waves and the different wavelengths of the electromagnetic spectrum. At the same time, students gain current insight into issues in modern astronomy and space science. In this five-activity unit, students consider how our everyday world and the cosmos look when they are observed in other wavelengths. With the mystery of gamma-ray bursts as a motivation, the students gain the prerequisite knowledge and ideas that can lead to understanding the mystery, which is only now being solved. These precursor concepts come into play as students learn about: waves and wave motion (Activity 1); invisible waves (Activity 2); the entire electromagnetic spectrum (Activity 3); distances to celestial objects (Activity 4); and then gain a sense of the huge amounts of energy that can be released in cosmic events and learn how astronomers plan to further investigate the mystery of gamma-ray bursts (Activity 5). Images used in Activity 4 can also be downloaded from the accompanying Website.

2002-01-01

293

Shifting scintillator neutron detector  

DOEpatents

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

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

2014-03-04

294

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

295

Disks, young stars, and radio waves: the quest for forming planetary systems  

E-print Network

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

Claire J. Chandler; Debra S. Shepherd

2008-01-24

296

A novel scheme to implement duplex 60-GHz radio-over-fiber link with 20-GHz double-sideband optical millimeter-wave transmitted along the fiber  

NASA Astrophysics Data System (ADS)

A duplex radio-over-fiber (RoF) link with a novel scheme to generate 60-GHz millimeter (mm)-wave using 20 GHz double sideband (DSB) optical mm-wave with signal carried only by its optical carrier is investigated. In the RoF downlink, the modulation frequency to generate the DSB optical mm-wave is reduced greatly. The theoretical analysis and numerical simulation show that this scheme cannot only eliminate the code form distortion caused by the time shifting of the sidebands, but also reduce the influence of the fading effect as the DSB optical mm-wave signal is transmitted along the fiber. Based on the scheme, the duplex RoF link with the frequency up- (down-) conversion of the down- (up-) link mm-wave signal is built and the uplink transmission performance is analyzed theoretically.

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

2009-03-01

297

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

298

Radio Telescopes  

NASA Astrophysics Data System (ADS)

``Radio Telescopes" starts with a brief historical introduction from Jansky's1931 discovery of radio emission from the Milky Way through the development ofradio telescope dishes and arrays to aperture synthesis imaging. It includessufficient basics of electromagnetic radiation to provide some understanding of thedesign and operation of radio telescopes. The criteria such as frequencyrange, sensitivity, survey speed, angular resolution, and field of view thatdetermine the design of radio telescopes are introduced. Because it is soeasy to manipulate the electromagnetic waves at radio frequencies, radiotelescopes have evolved into many different forms, sometimes with "wire"structures tuned to specific wavelengths, which look very different from anykind of classical telescope. To assist astronomers more familiar with otherwavelength domains, the appendix A.1. includes a comparison of radioand optical terminology. Some of the different types of radio telescopesincluding the filled aperture dishes, electronically steered phased arrays, andaperture synthesis radio telescopes are discussed, and there is a sectioncomparing the differences between dishes and arrays. Some of the morerecent developments including hierarchical beam forming, phased arrayfeeds, mosaicing, rotation measure synthesis, digital receivers, and longbaseline interferometers are included. The problem of increasing radiofrequency interference is discussed, and some possible mitigation strategies areoutlined.

Ekers, Ron; Wilson, Thomas L.

299

The detection of coronal mass ejections in the interplanetary medium using scintillation observations  

NASA Astrophysics Data System (ADS)

Daily observations of scintillating radio sources obtained from July 2011 through June 2012 on the Big Scanning Antenna of the P.N. Lebedev Physical Institute at 111 MHz using a 16 beams system are analyzed. Variations in the observed scintillation indices are compared with data on solar X-ray flares and geomagnetic disturbances. Comparison of the observed scintillation indices on successive days enables the detection of most propagating disturbances associated with coronal events of class M5.0 and higher.

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

2014-09-01

300

Equatorial scintillation model. Technical report, 1 February 1983-30 April 1985  

Microsoft Academic Search

Radiowave scintillation in the presence of natural and\\/or high-altitude nuclear disturbances has the potential to disrupt numerous transionospheric radio and radar systems. This report develops a model characterizing the plasma-density irregularities that produce scintillation in the naturally disturbed equatorial F layer. The model is incorporated into Program WBMOD along with subroutines for computing both link geometry and scintillation indices, the

E. J. Fremouw; R. E. Robins

1985-01-01

301

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

302

Statistics of ionospheric scintillation occurrence over European high latitudes  

NASA Astrophysics Data System (ADS)

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

Sreeja, V.; Aquino, M.

2014-12-01

303

A study of GPS ionospheric scintillations observed at Guilin  

NASA Astrophysics Data System (ADS)

The occurrence of strong ionospheric scintillations with S4>=0.2 was studied using global positioning system (GPS) measurements at Guilin (25.29°N, 110.33°E; geomagnetic: 15.04°N, 181.98°E), a station located near the northern crest of equatorial anomaly in China. The results are presented for data collected from January 2007 to December 2008. The results show that amplitude scintillations occurred only during the first five months of the considered years. Nighttime amplitude scintillations, observed mainly in the south of Guilin, always occurred with phase scintillations, total electron content (TEC) depletions, and Rate Of change of TEC (ROT) fluctuations. However, TEC depletions and ROT fluctuations were weak during daytime amplitude scintillations, and daytime amplitude scintillations usually occurred in most of the azimuth directions. GPS scintillation/TEC observations recorded at Guilin and signal-to-noise-ratio measurements obtained from GPS-COSMIC radio occultation indicate that nighttime and daytime scintillations are very likely caused by ionospheric F region irregularities and sporadic E, respectively.

Zou, Yuhua; Wang, Dongli

2009-12-01

304

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

305

Radio wave diffraction during the passage of an acoustic shock through a sporadic E layer  

SciTech Connect

Bistatic HF Doppler measurements of the ionospheric disturbance arising from a large ground-level chemical explosion have revealed a peculiar HF return which begins at large positive Doppler (greater than +5 Hz) and linearly evolves to large negative Doppler (less than -5 Hz). Various pieces of evidence in the data suggest that an HF wave which is diffracted from the intersection of the acoustic shock and an extensive plane of sporadic E ionization at 110 km was observed. From these measurements the horizontal trace velocity of the locus of intersection is estimated. 16 references.

Jacobson, A.R.; Carlos, R.C.; Argo, P.E.; Rickel, D.G.

1986-08-01

306

Formation of ultrashort radio pulses in a traveling wave tube with a drift space  

NASA Astrophysics Data System (ADS)

The effectiveness of ultrashort-pulse formation in a TWT with a continuous helical slow-wave structure (SWS) is compared with that of a TWT with a drift space. The comparison is carried out on the basis of numerical simulation in the framework of nonstationary nonlinear theory. It is shown that the introduction of substantially long drift leads to a significant improvement in the formation conditions of long-duration, high-amplitude pulses. The effect of SWS section lengths and desynchronization parameters on the pulse-formation processes is investigated.

Luk'ianchikov, A. V.; Shkol'Nikov, V. G.

1987-11-01

307

Integrated Software for Image Processing in Radio Frequency Surface and Bulk Acoustic Wave Laser Probe System  

NASA Astrophysics Data System (ADS)

In this paper, we describe the development of an integrated software environment for the image processing of complex data captured using a phase-sensitive surface and bulk acoustic wave (SAW/BAW) laser probe system. The developed software displays the amplitude and phase images of the acquired results and a motion movie of the field pattern. Prior to fast Fourier transform (FFT) and/or inverse FFT (IFFT) operation, we can extract or withdraw specific data in x-y or ?x-?y space by using the mouse on the image. Using the software with a graphical user interface, efficient diagnosis of SAW/BAW devices is made possible.

Wu, Nan; Hashimoto, Ken-ya; Kashiwa, Keisuke; Omori, Tatsuya; Yamaguchi, Masatsune

2009-08-01

308

A circuit model for nonlinear simulation of radio-frequency filters using bulk acoustic wave resonators.  

PubMed

This paper describes a circuit model for the analysis of nonlinearity in the filters based on radiofrequency (RF) bulk acoustic wave (BAW) resonators. The nonlinear output is expressed by a current source connected parallel to the linear resonator. Amplitude of the nonlinear current source is programmed proportional to the product of linear currents flowing in the resonator. Thus, the nonlinear analysis is performed by the common linear analysis, even for complex device structures. The analysis is applied to a ladder-type RF BAW filter, and frequency dependence of the nonlinear output is discussed. Furthermore, this analysis is verified through comparison with experiments. PMID:18467229

Ueda, Masanori; Iwaki, Masafumi; Nishihara, Tokihiro; Satoh, Yoshio; Hashimoto, Ken-ya

2008-04-01

309

Robust GPS carrier tracking under ionospheric scintillation  

NASA Astrophysics Data System (ADS)

Small scale irregularities present in the ionosphere can induce fast and unpredictable fluctuations of Radio Frequency (RF) signal phase and amplitude. This phenomenon, known as scintillation, can degrade the performance of a GPS receiver leading to cycle slips, increasing the tracking error and also producing a complete loss of lock. In the most severe scenarios, if the tracking of multiple satellites links is prevented, outages in the GPS service can also occur. In order to render a GPS receiver more robust under scintillation, particular attention should be dedicated to the design of the carrier tracking stage, that is the receiver's part most sensitive to these types of phenomenon. This paper exploits the reconfigurability and flexibility of a GPS software receiver to develop a tracking algorithm that is more robust under ionospheric scintillation. For this purpose, first of all, the scintillation level is monitored in real time. Indeed the carrier phase and the post correlation terms obtained by the PLL (Phase Locked Loop) are used to estimate phi60 and S4 [1], the scintillation indices traditionally used to quantify the level of phase and amplitude scintillations, as well as p and T, the spectral parameters of the fluctuations PSD. The effectiveness of the scintillation parameter computation is confirmed by comparing the values obtained by the software receiver and the ones provided by a commercial scintillation monitoring, i.e. the Septentrio PolarxS receiver [2]. Then the above scintillation parameters and the signal carrier to noise density are exploited to tune the carrier tracking algorithm. In case of very weak signals the FLL (Frequency Locked Loop) scheme is selected in order to maintain the signal lock. Otherwise an adaptive bandwidth Phase Locked Loop (PLL) scheme is adopted. The optimum bandwidth for the specific scintillation scenario is evaluated in real time by exploiting the Conker formula [1] for the tracking jitter estimation. The performance of the proposed tracking scheme is assessed by using both simulated and real data. Real data have been collected in Vietnam by using a USRP (Universal Software Radio Peripheral) N210 front end connected to a rubidium oscillator. Selected events are exploited in order to challenge the algorithm with strong phase and amplitude variations. Moreover, simulated data have been collected by using the prototype of a digital front end developed by Novatel, namely the 'Firehose'. Since the latter includes a TCXO oscillator, the proposed tracking scheme is also opportunely modified to take in account the clock error contribution. References 1. R.S., Conker, M. B. El-Arini, C. J. Hegarty, and T. Hsiao, Modelling the effects of ionospheric scintillation on GPS/satellite-based augmentation system availability. Radio Sci., 38, 1, 1001, doi: 10.1029/2000RS002604, 2003. 2. B. Bougard et al, 'CIGALA: Challenging the Solar Maximum in Brazil with PolaRxS,' ION GNSS, Portland, Sept. 2011.

Susi, M.; Andreotti, M.; Aquino, M. H.; Dodson, A.

2013-12-01

310

GPS and ionospheric scintillations  

NASA Astrophysics Data System (ADS)

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, interruption is caused by fading of the in-phase and quadrature signals, making the determination of phase by a tracking loop impossible. Degradation occurs when phase scintillations introduce ranging errors or when loss of tracking and failure to acquire signals increases the dilution of precision. GPS scintillations occur most often near the magnetic equator during solar maximum, but they can occur anywhere on Earth during any phase of the solar cycle. In this article we review the subject of GPS and ionospheric scintillations for scientists interested in space weather and engineers interested in the impact of scintillations on GPS receiver design and use.

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

2007-09-01

311

Measurement of the amplitude and phase fluctuation spectrum of satellite signals in the case of the action of high-power radio waves on the ionosphere  

Microsoft Academic Search

Artificial ionospheric irregularities produced by high-power radio-frequency heating were investigated by measuring signals from NNSSA satellites at the coherent frequencies 150 and 400 MHz. Spectral processing of the data indicates the existence of two spectrum types of artificial irregularities excited by high-power short waves: (1) a spectrum with a monotonic power dependence and (2) a spectrum with a peak in

F. I. Vybornov; L. M. Erukhimov; G. P. Komrakov; V. I. Kosolapenko; V. A. Kriazhev

1986-01-01

312

Electromagnetic Waves Attenuation due to Rain: A Prediction Model for Terrestrial or L.O.S SHF and EHF Radio Communication Links  

Microsoft Academic Search

Because of the interest raised for SHF and EHF radio communications, the attenuation of electromagnetic waves by rain will\\u000a always constitute a major concern for telecommunication engineers and scientists. The rain attenuation prediction models exposed\\u000a in literature calculate the attenuation related to a given rain rate or else to a given percentage of time. The new model\\u000a proposed in this

Fidèle Moupfouma

2009-01-01

313

CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: Radio-Frequency Characteristics of a Printed Rectangular Helix Slow-Wave Structure  

Microsoft Academic Search

A new type of printed rectangular helix slow-wave structure (SWS) is investigated using the field-matching method and the electromagnetic integral equations at the boundaries. The radio-frequency characteristics including the dispersion equation and the coupling impedance for transverse antisymmetric (odd) modes of this structure are analysed. The numerical results agree well with the results obtained by the EM simulation software HFSS.

Cheng-Fang Fu; Yan-Yu Wei; Wen-Xiang Wang; Yu-Bin Gong

2008-01-01

314

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

315

Physiological effects of 2.8 GHz radio-frequency radiation: a comparison of pulsed and continuous-wave radiation.  

PubMed

Ketamine-anesthetized female Sprague-Dawley rats were exposed individually to far-field 2.8 GHz continuous wave (CW) and pulsed (2 microseconds, 500 pps) radio-frequency radiation (RFR) at average power densities of 30, 45, and 60 mW/cm2 [specific absorption rates (SAR) of 8.4, 12.6, and 16.8 W/kg, respectively] and to pulsed RFR at 75 mW/cm2 (SAR = 21 W/kg). Intermittent exposures were conducted to repeatedly increase colonic temperature from 38.5 to 39.5 degrees C. Colonic, tympanic, and subcutaneous temperatures, electrocardiogram, respiratory rate, and arterial blood pressure were continuously monitored and recorded. The time required to effect a 1 degree C colonic temperature increase varied inversely with the average power density used during exposure; however, the rate of cooling was independent of the heating rate. During pulsed irradiation, heart rate increased significantly at average power densities above 30 mW/cm2; heart rate increase during CW exposure was not significant. Heart rate returned to baseline when exposure was discontinued. Blood pressure and respiratory rate did not significantly change during irradiation. Pulsed RFR exposure caused a significantly greater increase in subcutaneous and tympanic temperatures than did CW exposure; however, no significant difference was noted between the effects of CW or pulsed RFR upon the rats' colonic temperature responses (heating and cooling time), heart rate, blood pressure, and respiratory rate. PMID:3193341

Frei, M; Jauchem, J; Heinmets, F

1988-01-01

316

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

NASA Astrophysics Data System (ADS)

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

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

2006-09-01

317

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

NASA Astrophysics Data System (ADS)

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

Vagula, Mary; Harkless, Ryan

2013-05-01

318

Interferometric observation of over-horizon and ionospheric VHF radio waves associated with earthquakes.  

NASA Astrophysics Data System (ADS)

Recently it has been found that the perturbations in the atmosphere and ionosphere take place in association with earthquakes (Hayakawa and Molchanov, 2002 Monograph). Fukumoto et al. (2001) have found that the over-horizon VHF waves (FM broadcasting signals) are occasionally observed prior to an earthquake, and their VHF direction finding has indicated that the reception of those over-horizon VHF signal is due to the perturbation in the atmosphere. Additionally Takano et al. (2001) have found that the TV VHF signals in the South-East Asia (like Thailand and China) are often received in Japan in possible association with earthquakes. In order to investigate the mechanism of those VHF anomalous signals, we have developed an interferometric measurement for those VHF signals to determine their direction of arrival (incident (elevation) angle and azmuthal angle (bearing)). We first describe our interferometer system, then show some preliminary observational data, and followed by the future system.

Gotoh, T.; Hayakawa, M.

2004-12-01

319

Bulk acoustic wave approach to wideband radio-frequency spectrum analysis  

NASA Astrophysics Data System (ADS)

The need to process the ever increasing number of exotic signals simultaneously, is a major motivation to develop efficient Bulk Acoustic Wave (BAW) processors. In devices using active input arrays it is important that the phased transducers not only operate over a wideband but also steer the BAWs efficiently over a large angular span. Wideband, spurious free beam-steering of an input transducer array that is fabricated using dielectric well technology is demonstrated. Operation of BAW spectrum analyzers based on active input arrays is modeled, where various issues of importance such as anisotropy and mode conversion are taken into consideration. Acoustic beam profiles are measured via Bragg scattering of focused laser beams. The experiments demonstrate channelization of RF signals in a LiNbO3 device, and validate a theoretical diffraction model that is based on Huygen's principle.

Sabet-Peyman, F.; Chau, K.; Dwelle, R.

1987-01-01

320

Tunable Radio-Frequency Filters Using Acoustic Wave Resonators and Variable Capacitors  

NASA Astrophysics Data System (ADS)

In this paper, we describe possible configurations for tunable filters based on RF surface or bulk acoustic wave (SAW/BAW) technologies. The frequency tuning is made possible by variable capacitors (VCs) connected to SAW/BAW resonators in the ladder-type filter configuration. First, it is shown that the passband edges can be controlled by one VC connected to each resonator. Second, it is discussed that the width and location of a passband can be controlled flexibly by two VCs connected to each resonator both in parallel and in series. Finally, the SAW filters with the proposed configuration are fabricated on a Cu-grating/15°YX-LiNbO3 substrate structure, and the tuning capability is demonstrated.

Komatsu, Tomoya; Hashimoto, Ken-ya; Omori, Tatsuya; Yamaguchi, Masatsune

2010-07-01

321

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

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

322

Broadband meter-wavelength observations of ionospheric scintillation  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

323

Waves  

NSDL National Science Digital Library

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

Mrs. Petersen

2014-05-27

324

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

325

A mid-latitude scintillation model  

NASA Astrophysics Data System (ADS)

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

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

1986-10-01

326

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

327

Improvement of the scintillation-irregularity model in WBMOD  

Microsoft Academic Search

The descriptive model of scintillation-producing irregularities in the F layer contained in Program WBMOD has been improved, along with other aspects of the code. Improvements include use of magnetic local time for modeling high-latitude boundaries, correction of a subtle error in calculating the scan velocity of the radio line of sight, simplification of the orbit calculation, and implementation of an

J. A. Secan; E. J. Fremouw

1983-01-01

328

Tackling ionospheric scintillation threat to GNSS in Latin America  

NASA Astrophysics Data System (ADS)

Scintillations are rapid fluctuations in the phase and amplitude of transionospheric radio signals which are caused by small-scale plasma density irregularities in the ionosphere. In the case of the Global Navigation Satellite System (GNSS) receivers, scintillation can cause cycle slips, degrade the positioning accuracy and, when severe enough, can even lead to a complete loss of signal lock. Thus, the required levels of availability, accuracy, integrity and reliability for the GNSS applications may not be met during scintillation occurrence; this poses a major threat to a large number of modern-day GNSS-based applications. The whole of Latin America, Brazil in particular, is located in one of the regions most affected by scintillations. These effects will be exacerbated during solar maxima, the next predicted for 2013. This paper presents initial results from a research work aimed to tackle ionospheric scintillation effects for GNSS users in Latin America. This research is a part of the CIGALA (Concept for Ionospheric Scintillation Mitigation for Professional GNSS in Latin America) project, co-funded by the EC Seventh Framework Program and supervised by the GNSS Supervisory Authority (GSA), which aims to develop and test ionospheric scintillation countermeasures to be implemented in multi-frequency, multi-constellation GNSS receivers.

Veettil Sreeja, Vadakke; Aquino, Marcio; Forte, Biagio; Elmas, Zeynep; Hancock, Craig; de Franceschi, Giorgiana; Alfonsi, Lucilla; Spogli, Luca; Romano, Vincenzo; Bougard, Bruno; Francisco Galera Monico, Joao; Wernik, Andrzej W.; Sleewaegen, Jean-Marie; Cantó, Andrea; Ferreira da Silva, Elcia

2011-11-01

329

A Generic Receiver Tracking Model for GPS Ionospheric Amplitude Scintillation  

NASA Astrophysics Data System (ADS)

Ionospheric scintillations result in rapid variations in phase and amplitude of the radio signal, which propagates through the ionosphere. Depending on the temporal and spatial situation, the scintillation can represent a problem in the availability and precision of the Global Navigation Satellite Systems (GNSS). Scintillations affect the receiver performance, specially the tracking loop level. Depending on the scintillation level, the receiver might increase the measurement errors or even can lead to a loss of lock of the carrier and code loops. In extreme cases, the scintillation can result in full disrupting of the receiver. In this work we introduce a generic model to evaluate the effects of ionospheric amplitude scintillation on GPS receiver tracking loops. This model is based on ?-? distribution, which can be seen as a generalized fading model, that includes a variety of distributions such as Gamma, Nakagami-m, Exponential, Weibull, one-sided Gaussian and Rayleigh. Differently from the model based only on Nakagami-m, this one is not limited to S4< 0,71 which allows using it to predict amplitude scintillation effects for stronger scenarios. The estimation of ?-? coefficients, the empirical parameterization based on field measurements and the typical values estimated based on observations made during the last solar maximum are presented and discussed.

Paula, E. R.; Moraes, A. D.; Perrella, W. J.; Galera Monico, J. F.

2012-12-01

330

Characterization of ionospheric amplitude scintillations using wavelet entropy detrended GNSS data  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

331

Radio Astronomy Radio astronomy  

E-print Network

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

Metchev, Stanimir

332

Pulsed and continuous wave acrylic acid radio frequency plasma deposits: plasma and surface chemistry.  

PubMed

Plasma polymers have been formed from acrylic acid using a pulsed power source. An on-pulse duration of 100 micros was used with a range of discharge off-times between 0 (continuous wave) and 20,000 micros. X-ray photoelectron spectroscopy (XPS) has been used in combination with trifluoroethanol (TFE) derivatization to quantify the surface concentration of the carboxylic acid functionality in the deposit. Retention of this functionality from the monomer varied from 2% to 65%. When input power was expressed as the time-averaged energy per monomer molecule, E(mean), the deposit chemistry achieved could be described using a single relationship for all deposition conditions. Deposition rates were monitored using a quartz crystal microbalance, which revealed a range from 20 to 200 microg m(-2) s(-1), and these fell as COOH functional retention increased. The flow rate was found to be the major determinant of the deposition rate, rather than being uniquely defined by E(mean), connected to the rate at which fresh monomer enters the system in the monomer deficient regime. The neutral species were collected in a time-averaged manner. As the energy delivered per molecule in the system (E(mean)) decreased, the amount of intact monomer increased, with the average neutral mass approaching 72 amu as E(mean) tends to zero. No neutral oligomeric species were detected. Langmuir probes have been used to determine the temporal evolution of the density and temperature of the electrons in the plasma and the plasma potential adjacent to the depositing film. It has been found that even 500 micros into the afterglow period that ionic densities are still significant, 5-10% of the on-time density, and that ion accelerating sheath potentials fall from 40 V in the on-time to a few volts in the off-time. We have made the first detailed, time- and energy-resolved mass spectrometry measurements in depositing acrylic acid plasma. These have allowed us to identify and quantify the positive ion species in the acrylic acid plasma during both the on- and the off- periods. The relative intensities of oligomeric species of the type [nM + H]+ as large as n = 3 were observed to increase in the off-time suggesting vapor phase polymerization after power input to the plasma was ceased. The energy distribution functions of these ions demonstrated that they were produced in the plasma in both the on- and the off-times. This remarkable observation contradicts the assumptions usually made when speculating on pulsed plasma that ions have very short lifetimes, although it is anticipated that radicals still have significantly longer lifetimes, estimated from calculation to be in excess of 1 ms. The increase in average positive ion mass during the off-period can be related to the lower mobility of the heavier components, reducing their relative loss to surfaces, and the polymer chain growth in the gas phase due to the ion-neutral collisions. The implications of these observations are discussed in light of polymerization mechanisms proposed from continuous acrylic acid and millisecond pulsing plasmas. PMID:17388498

Voronin, Sergey A; Zelzer, Mischa; Fotea, Catalin; Alexander, Morgan R; Bradley, James W

2007-04-01

333

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

334

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

335

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

336

MEXART. Interplanetary Scintillation Array in Mexico in the IHY2007  

NASA Astrophysics Data System (ADS)

The Mexican Array Radio Telescope (MEXART) consists of a 64x64 (4096) full wavelength dipole antenna array, operating at 140 MHz, occupying 9,500 square meters (70 m x 140 m) to carry out interplanetary scintillation (IPS) observations. This is a dedicated radio array for IPS observations located in the state of Michoacan (350 km north-west from Mexico City, lat. 19^ 48' N, long. 101^ 41' W and 1964 m above sea level). We report the system testings, radio source measurements and the collaboration plans for the International Heliophysical Year 2007.

Gonzalez-Esparza, A.; Andrade, E.; Carrillo, A.; Kurtz, S.; Jeyakumar, S.; Perez-Enriquez, R.; Sierra, P.; Vazquez, S.; Manoharan, P.

2006-12-01

337

MEXART. Interplanetary Scintillation Array in Mexico in the IHY2007  

NASA Astrophysics Data System (ADS)

The Mexican Array Radio Telescope MEXART consists of a 64x64 4096 full wavelength dipole antenna array operating at 140 MHz occupying 9 500 square meters 70 m x 140 m to carry out interplanetary scintillation IPS observations This is a dedicated radio array for IPS observations located in the state of Michoacan 350 km north-west from Mexico City lat 19° 48 N long 101° 41 W and 1964 m above sea level We report the system testings radio source measurements and the collaboration plans for the International Heliophysical Year 2007

Gonzalez-Esparza, A.; Carrillo, A.; Andrade, E.; Jeyakumar, S.; Perez-Enriquez, R.; Kurtz, S.

338

Radio Galaxies.  

ERIC Educational Resources Information Center

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

Downes, Ann

1986-01-01

339

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

340

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)

Wuhan 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

341

A gravity wave analysis near to the Andes Range from GPS radio occultation data and mesoscale numerical simulations: Two case studies  

NASA Astrophysics Data System (ADS)

Global maps of potential wave energy per unit mass, recently performed with the Global Positioning System (GPS) Radio Occultation (RO) technique and different satellite missions (CHAMP and SAC-C since 2001, GRACE and COSMIC since 2006) revealed in Argentina, at the eastern side of the highest Andes Mountains, a considerable wave activity (WA) in comparison with other extra-tropical regions. The main gravity wave (GW) sources in this natural laboratory are deep convection (mainly during late Spring and Summer), topographic forcing and geostrophic adjustment. The mesoscale numerical WRF (Weather Research and Forecasting) 2.1.2 model was used to simulate the atmospheric parameters during two representative RO events showing apparent intense WA in this region. The significance of the relative position of the RO lines of sight, the line of tangent points and GW phase surfaces during each event is discussed in relation with the apparent WA detected. The GPS RO technique may not be by itself reliable enough to quantify and locate WA of single events. Nevertheless, it should be considered a useful tool to observe the global WA from statistical studies. We also discuss the relative contribution of high and medium intrinsic frequency mountain waves regularly observed, coexisting with inertio gravity waves, their origin and propagation characteristics.

Llamedo, P.; de la Torre, A.; Alexander, P.; Luna, D.; Schmidt, T.; Wickert, J.

2009-08-01

342

A refracting radio telescope  

Microsoft Academic Search

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

Paul Bernhardt; A. V. da Rosa

1977-01-01

343

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

344

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

NASA Astrophysics Data System (ADS)

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

Ma, Jianxin; Li, Yanjie

2015-01-01

345

Geomagnetic Control of Satellite Scintillations  

Microsoft Academic Search

Satellite scintillations may be divided into three basic types- (1) low-angle scintil- lations of both tropospheric and ionospheric origin; (2) clouds or patches of ionization con- raining irregularities iiicluding sporadic E; and (3) precipitation scintillation occurring for the most part at heights of 300 to 500 kin. The third type is discin detail; the hypothesis is advanced that this basic

J. Aarons; J. Mullen; Sunanda Basu

1963-01-01

346

Position Reconstruction in Scintillation Detectors  

E-print Network

Chapter 5 Position Reconstruction in Scintillation Detectors Borexino is one of a new generation of position reconstruction for scintillator-based, unsegmented detectors, and the spatial resolutions that may the 201 #12;Chapter 5. Position Reconstruction in Scintillation Detectors 202 detector [55, 63

347

Measurements of an Antenna Surface for a Millimeter-Wave Space Radio Telescope. II. Metal Mesh Surface for Large Deployable Reflector  

NASA Astrophysics Data System (ADS)

Large deployable antennas with a mesh surface woven by fine metal wires are an important technology for communications satellites and space radio telescopes. However, it is difficult to make metal mesh surfaces with sufficient radio-frequency (RF) performance for frequencies higher than millimeter waves. In this paper, we present the RF performance of metal mesh surfaces at 43 GHz. For this purpose, we developed an apparatus to measure the reflection coefficient, transmission coefficient, and radiative coefficient of the mesh surface. The reflection coefficient increases as a function of the metal mesh surface tension, whereas the radiative coefficient decreases. The anisotropic aspects of the reflection coefficient and the radiative coefficient are also clearly seen. They depend on the front and back sides of the metal mesh surface and the rotation angle. The transmission coefficient was measured to be almost constant. The measured radiative coefficients and transmission coefficients would cause significant degradation of the system noise temperature. In addition, we carried out an astronomical observation of a well-known SiO maser source, R Cas, by using a metal mesh mirror on the NRO 45-m radio telescope Coudé system. The metal mesh mirror considerably increases the system noise temperature, and slightly decreases the peak antenna temperature. These results are consistent with laboratory measurements.

Kamegai, Kazuhisa; Tsuboi, Masato

2013-02-01

348

Radio Interferometric Geolocation Miklos Maroti  

E-print Network

Radio Interferometric Geolocation Mikl´os Mar´oti P´eter V¨olgyesi Sebesty´en D´ora Branislav.kusy, akos.ledeczi}@vanderbilt.edu ABSTRACT We present a novel radio interference based sensor local- ization method for wireless sensor networks. The technique relies on a pair of nodes emitting radio waves

Maróti, Miklós

349

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

350

New Lutetium Silicate Scintillators  

Microsoft Academic Search

Cerium-doped lutecium orthosilicate (LSO) is the most promising scintillator discovered in almost five decades. It exhibits a unique combination of important properties for x and gamma-ray spectroscopy: high density, fast decay, and large light yield. However, the practical use of LSO is hindered by difficulties related to its fabrication as a single crystal by the Czochralski method. We report on

Eric Bescher; S. R. Robson; J. D. Mackenzie; B. Patt; J. Iwanczyk; E. J. Hoffman

2000-01-01

351

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

352

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

353

Subionospheric VLF/LF radio waves propagation characteristics before, during and after the Sofia, Bulgaria Mw=5.6 earthquake occurred on 22 May 2012  

NASA Astrophysics Data System (ADS)

In 2009, INFREP, a network of VLF (20-60 kHz) and LF (150-300 kHz) radio receivers, was put into operation in Europe having as principal goal, the study of disturbances produced by the earthquakes on the propagation properties of these signals. On May 22nd, 2012 an earthquake with Mw=567 occurred in Bulgaria, near Sofia, inside the "sensitive" area of the INFREP VLF/LF electromagnetic network. The data collected on different frequencies, during April-May 2012 were studied using different methods of analysis: daily correlation methods, spectral approaches and terminator time techniques, in order to find out possible connections between the seismic activity and the subionospheric propagation properties of radio waves. The studies were performed with the help of a specially designed LabVIEW application, which accesses the VLF/LF receiver through internet. This program opens the receiver's web-page and automatically retrieves the list of data files to synchronize the user-side data with the receiver's data. Missing zipped files are also automatically downloaded. The application performs primary, statistical correlation and spectral analysis, appends daily files into monthly and annual files and performs 3D colour-coded maps with graphic representations of VLF and LF signals' intensities versus the minute-of-the-day and the day-of-the-month, facilitating a near real-time observation of VLF and LF electromagnetic waves' propagation. Another feature of the software is the correlation of the daily recorded files for the studied frequencies by overlaying the 24 hours radio activity and taking into account the sunrise and sunset. Data are individually processed (spectral power, correlations, differentiation, filtered using bandpass, lowpass, highpass). JTFA spectrograms (Cone-Shaped Distribution CSD, Gabor, Wavelet, short-time Fourier transform STFT, Wigner-Ville Distribution WVD, Choi-Williams Distribution CWD) are used, too.

Moldovan, Iren Adelina; Emilian Toader, Victorin; Nenovski, Petko; Biagi, Pier Francesco; Maggipinto, Tommaso; Septimiu Moldovan, Adrian; Ionescu, Constantin

2013-04-01

354

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

355

On the possibility of producing artificial ionization and polar aurora in the ionosphere by radio-waves emitted from the ground  

NASA Astrophysics Data System (ADS)

In 1938 Prof. V. A. Bailey demonstrated by calculations that some resonance may occur between electrons and a wave as the frequency of this wave varies around the local gyrofrequency, fh. A radio-wave having a frequency equal to the gyrofrequency is called a, gyro-wave. The resonance increases the collision frequency in the low ionosphere by an appreciable amount (I). There are two principal consequencies of the resonance: If a second wave unmodulated passes through the ionosphere region where the gyro-wave acts, an interaction is found between these two waves. This phenomenon is called gyrointeraction and was demonstrated experimentally. If the radiowave is a gyro-wave, with a carrier frequency varying around the local gyrofrequency and is powerful it could produce in the ionosphere an artificial aurora or airglow. The powerful gyro-wave would reduce strongly the electric voltage of the region illuminated by the gyro-wave as to generate an electrical discharge. Moreover with a suitable system of 800 aerial and with a power of 500 kW or of 1,000,000 kW it would be possible to generate an artificial aurora between 60 and 88 km in the ionosphere. Starting form the experiments of H. A. Wilson and D. M. Myers with high-frequency discharges on the lines developed by J. S Towsend and his associates, Bailey developed his theory. These experiments, made by Wilson and Myers, showed that the electric discharges can occur in the air when in the uniform column z/p the ratio of the electric force z to the gas pressure p is approximately 16. It is possible therefore to conclude that two of the necessary conditions for producing electrons and light, are satisfied when E/p 16. An investigation was made in 1959 of the possible increases of both the collision frequencies and the electron density N caused by a powerful extraordinary circular gyrowave in the nocturnal lower-E-region and in the daytime D-region. The principal process then freshly introduced was the attachment of the electrons to molecules in some collisions. According to this new thory the power density requirement for the excitations of an artificial airglow by means of gyrowaves were reconsidered.

Cutolo, Mario; Argenziano, Angela

1989-04-01

356

Wave represents displacement Wave represents pressure Source -Sound Waves  

E-print Network

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

Colorado at Boulder, University of

357

Direct Access to Plasma Resonance in Ionospheric Radio Experiments  

Microsoft Academic Search

The concept of linear conversion of radio waves into electrostatic (ES) waves is adapted to ionospheric radio heating experiments. It is identified as access to the plasma resonance through the radio window. By means of existing heating facilities, large concentrations of electrostatic wave energy can be generated. The ES waves are confined to a restricted region in space, horizontally displaced

Einar Mjølhus; Tor FlÅ

1984-01-01

358

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

SciTech Connect

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

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

2011-05-15

359

Modification of the high latitude F region of the ionosphere by X-mode powerful HF radio waves: Experimental results from multi-instrument diagnostics  

NASA Astrophysics Data System (ADS)

We present the experimental results for strong plasma modifications induced by the X-mode powerful HF radio waves injected towards the magnetic zenith into the high latitude F region of the ionosphere. A large number of experiments in the course of Russian EISCAT heating campaigns were conducted in 2009 - 2013 under different background conditions in a wide heater frequency range from 4 to 8 MHz. The EISCAT UHF incoherent scatter radar at Tromsø, the CUTLASS (SuperDARN) HF coherent radar in Finland, SEE receiver at Tromsø, the HF Doppler equipment near St. Petersburg, and the EISCAT ionosonde (dynasonde) were used as diagnostic instruments. The results show that the X-mode HF pump wave can generate: (1) strong small-scale artificial field aligned irregularities (AFAIs); (2) HF-induced plasma and HF-enhanced ion lines (HFPLs and HFILs) from UHF radar spectra; (3) strong electron density enhancements along magnetic field line in a wide altitude range; (4) spectral components (few tens of Hz) in the Doppler spectra of the heater signal measured at a distance of 1200 km from the Tromsø HF heating facility. The experimental results obtained points to the strong magnetic zenith effect due to self-focusing powerful HF radio wave with X-mode polarization. For heater frequencies in the range of about 4 - 6 MHz the mentioned above phenomena are generated when the heater frequency is equal or above the ordinary-mode critical frequency (foF2). Under high background electron density and the heater frequencies used of 6.5 - 8.0 MHz, the strong X-mode HF-induced phenomena were observed both when the heater frequency is equal or above the foF2 and the heater frequency is below the foF2.

Blagoveshchenskaya, Nataly; Rietveld, Michael; Haggstrom, Ingemar; Borisova, Tatiana; Yeoman, Tim

360

86 IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, VOL. 47, NO. 1, JANUARY 1999 Diffraction of Radio Waves from Arbitrary  

E-print Network

- grated which accurately represent the effects of various terrain features on electromagnetic wave incidence at various oblique angles are shown. Effects of varying the impedance transition shape are shown Waves from Arbitrary One-Dimensional Surface Impedance Discontinuities Kamal Sarabandi, Senior Member

Sarabandi, Kamal

361

Characteristics of ionospheric scintillation measured using GPS receivers onboard the COSMIC satellites  

NASA Astrophysics Data System (ADS)

GPS radio occultation and orbit determination receivers onboard six COSMIC satellites have been enabled to measure amplitude scintillation of the L-band signals. The measurements fill large gaps of spatial coverage, particularly over oceans, and significantly augment our capacity of measuring ionospheric irregularities from space. This paper presents an analysis of the scintillation data collected under low solar activity conditions during last few years. The long-term data collection over the globe helps to draw interesting characteristics, which are partially consistent with the known morphology of ionospheric scintillation obtained from ground-based measurements in different regions, but also different in many aspects. The differences are examined in detail to address ionospheric scintillation and irregularities measured from space compared with ground-based measurements. It is attempted in this analysis to derive a guide line to distinguish spaceborne and ground-based measurements of ionospheric scintillation.

Pi, X.; Mannucci, A. J.

2010-12-01

362

Variations in the ionospheric wave perturbation spectrum during periodic heating of the plasma by high-power high-frequency radio waves  

Microsoft Academic Search

We present the results of spectral analysis of temporal variations in the Doppler frequency shift of the ionosphere-reflected\\u000a signals from a high-frequency vertical ionospheric sounding radar located near the city of Kharkov in the days of exposure\\u000a of the ionospheric plasma to the high-power radio emission of the Sura facility (Nizhny Novgorod) and in the reference day\\u000a in the absence

L. F. Chernogor; V. L. Frolov; G. P. Komrakov; V. F. Pushin

2011-01-01

363

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

364

Excitation of guided ELF-VLF waves through modification of the F{sub 2} ionospheric layer by high-power radio waves  

SciTech Connect

The possibility of controlled excitation of ELF-VLF electromagnetic waves through modification of the F{sub 2} ionospheric layer by high-power high-frequency emission is demonstrated in a natural experiment by using the Sura midlatitude heating facility. The excited low-frequency waves can be used to explore the near-Earth space and stimulate the excitation of a magnetospheric maser.

Markov, G. A.; Belov, A. S.; Komrakov, G. P. [Lobachevsky State University (Russian Federation); Parrot, M. [Environmental Physics and Chemistry Laboratory (France)

2012-03-15

365

Polarization-Independent Integrated Demultiplexer for DWDM 60GHz Millimeter-Wave-Band Radio-Over-Fiber Systems  

Microsoft Academic Search

We investigate the polarization dependence of an integrated demultiplexer for a dense wavelength-division-multiplexed system that uses an optical-frequency-interleaving technique. In the integrated demultiplexer, a suppression ratio of more than 22 dB against adjacent channels is measured. The integrated demultiplexer presents a polarization dependence of less than 0.1 dB, enabling access points for radio-over-fiber networks truly polarization-independent.

J. J. Vegas Olmos; Toshiaki Kuri; Ken-Ichi Kitayama

2008-01-01

366

On the second order statistics for GPS ionospheric scintillation modeling  

NASA Astrophysics Data System (ADS)

Equatorial 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

367

Characterization of the Ionospheric Scintillations at High Latitude using GPS Signal  

NASA Astrophysics Data System (ADS)

Transionospheric radio signals experience both amplitude and phase variations as a result of propagation through a turbulent ionosphere; this phenomenon is known as ionospheric scintillations. As a result of these fluctuations, Global Positioning System (GPS) receivers lose track of signals and consequently induce position and navigational errors. Therefore, there is a need to study these scintillations and their causes in order to not only resolve the navigational problem but in addition develop analytical and numerical radio propagation models. In order to quantify and qualify these scintillations, we analyze the probability distribution functions (PDFs) of L1 GPS signals at 50 Hz sampling rate using the Canadian High arctic Ionospheric Network (CHAIN) measurements. The raw GPS signal is detrended using a wavelet-based technique and the detrended amplitude and phase of the signal are used to construct probability distribution functions (PDFs) of the scintillating signal. The resulting PDFs are non-Gaussian. From the PDF functional fits, the moments are estimated. The results reveal a general non-trivial parabolic relationship between the normalized fourth and third moments for both the phase and amplitude of the signal. The calculated higher-order moments of the amplitude and phase distribution functions will help quantify some of the scintillation characteristics and in the process provide a base for forecasting, i.e. develop a scintillation climatology model. This statistical analysis, including power spectra, along with a numerical simulation will constitute the backbone of a high latitude scintillation model.

Mezaoui, H.; Hamza, A. M.; Jayachandran, P. T.

2013-12-01

368

Radio Science in Africa  

NASA Astrophysics Data System (ADS)

Radio science activities covered by URSI (International Radio Science Union) are briefly reviewed. They encompass the knowledge and study of all aspects of electromagnetic fields and waves in a wide frequency range running from micro pulsation 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 Photonics, electromagnetic environment and interference, wave propagation and remote sensing, ionospheric radio and propagation, waves in plasmas, radio astronomy, and electromagnetics in biology and medicine. The main radio science activities conducted by the URSI national Committees of South Africa, Egypt and Nigeria, and by African radio scientists groups gathered in GIRGEA (Groupe International de Recherche en Géophysique Europe Afrique) are reviewed. The emphasis is put on the activities developed in the context of the IHY programme and of the SCINDA network for forecasting ionospheric irregularities that adversely impact communication and navigation systems in the low latitude regions.

Lefeuvre, Francois; Mc Kinnel, Lee-Anne; Chukwuma, Victor; Amory-Mazaudier, Christine

2010-05-01

369

Automatic recognition of type III solar radio bursts in STEREO/WAVES data for onboard real-time and archived data processing  

NASA Astrophysics Data System (ADS)

Type III radio bursts are produced near the local electron plasma frequency and/or near its harmonic by fast electrons ejected from the solar active regions and moving through the corona and solar wind. These bursts have dynamic spectra with frequency rapidly falling with time. This paper presents two new methods developed to detect type III bursts automatically in the data from High Frequency Receiver (HFR) of the STEREO/WAVES radio instrument onboard the STEREO spacecraft. The first technique is applicable to the low-frequency band (HFR-1: 125 kHz to 1.975 MHz) only. This technique can possibly be implemented in onboard satellite software aimed at preliminary detection of bursts and identification of time intervals with relatively high solar activity. In the second technique the bursts are detected in both the low-frequency band and the high-frequency band (HFR-2: 2.025 MHz to 16.025 MHz), with the computational burden being higher by 1 order of magnitude as compared with that for the first technique. Preliminary tests of the method show that the performance of the first technique is quite high, PdL=72%±3%. The performance of the second technique is considerably higher, PdL+H=81%±1%, while the number of false alarms does not exceed 10% for one daily spectrum.

Lobzin, V. V.; Cairns, Iver H.; Zaslavsky, A.

2014-02-01

370

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

NASA Astrophysics Data System (ADS)

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

Schmitter, E. D.

2014-11-01

371

Improving the sensitivity of gravitational wave detection by applying a magnetic field evolution model to high cadence observational data of millisecond radio pulsars  

NASA Astrophysics Data System (ADS)

Radio pulsars are the most stable natural clocks in the universe, yet their timing noises can still be substantial when the times of arrivals of their pulses are fitted with some well accepted spin-down models or templates of pulsars. We have recently developed a model of the magnetic field evolution of neutron stars, which includes a long-term power-law decay modulated by periodic oscillations of the surface magnetic fields of neutron stars. Our model can explain the statistical properties of their timing noises. We find that the spin-down evolutions of young and old pulsars are dominated by the power-law decay and periodic oscillations, respectively. By applying this model to fit the high cadence observational data of millisecond radio pulsars with the Monte-Carlo Markov Chain method, we are able to improve the sensitivity of gravitational wave detection, because their timing residuals are reduced substantially. In the mean time, accurate parameters of pulsars' spi-down and magnetic fields are also obtained.

Zhang, Shuang-Nan; Yi, Shuxu

372

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

SciTech Connect

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

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

2012-07-01

373

Investigation of scintillator and fibre light in plastic scintillation dosimetry  

Microsoft Academic Search

Plastic scintillation dosimetry is a new and promising method of measuring dose in a radiation therapy beam. In this dosimetry system, the light signal produced in a miniature scintillator is transmitted to a photomultiplier tube via fiber optic cables. This system offers many advantages over conventional dosimetry methods, but an undesired radiation induced light signal is produced in the optical

Steven Francis Deboer

1993-01-01

374

Analysis of radio wave propagation for ISM 2.4 GHz Wireless Sensor Networks in inhomogeneous vegetation environments.  

PubMed

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

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

2014-01-01

375

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

PubMed Central

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

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

2014-01-01

376

Width of Radio-Loud and Radio-Quiet CMEs  

E-print Network

In the present paper we report on the difference in angular sizes between radio-loud and radio-quiet CMEs. For this purpose we compiled these two samples of events using Wind/WAVES and SOHO/LASCO observations obtained during 1996-2005. It is shown that the radio-loud CMEs are almost two times wider than the radio-quiet CMEs (considering expanding parts of CMEs). Furthermore we show that the radio-quiet CMEs have a narrow expanding bright part with a large extended diffusive structure. These results were obtained by measuring the CME widths in three different ways.

G. Michalek; N. Gopalswamy; H. Xie

2007-10-24

377

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

378

MEXART observations at 140 MHz: Calibration to perform the Interplanetary Scintillation (IPS) technique  

NASA Astrophysics Data System (ADS)

The Mexican Array Radio Telescope (MEXART) is an array of 64 X 64 dipoles, covering 9600 square meters, located in Michoacan, Mexico at a latitude of 19° and 101° longitude. The telescope has 16 beams at different declinations to detect stellar radio sources at 140 MHz in a declination range of -40° to 80°. We report the sensitivity of the instrument, by using a list of radio sources characterized at 140 MHz. We also present an analysis of the scintillation index versus the elongation angle for some IPS radio sources.

Villanueva, P.; Mejia Ambriz, J. C.; Gonzalez-Esparza, A.; Aguilar-Rodriguez, E.; Carrillo Vargas, A.; Andrade Mascote, E.

2010-12-01

379

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

380

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

381

RECENT ADVANCES IN SCINTILLATION COUNTERS  

Microsoft Academic Search

Scintillation counters have allowed since the beginning a great variety ; of measurements due to the flexibility of their use. Numerous improvements have ; been made and they have presently a prominent place among radiation detectors. ; It is shown how, by technical improvements, in both laboratory and industry, the ; scintillation counter has become an instrument currently used in

Koechlin

1959-01-01

382

Free liquid scintillation counting bibliography  

SciTech Connect

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

NONE

1996-12-31

383

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

384

Extruding plastic scintillator at Fermilab  

SciTech Connect

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

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

2003-10-31

385

Scintillation light transport and detection  

NASA Astrophysics Data System (ADS)

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

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

1987-08-01

386

Scintillation light transport and detection  

SciTech Connect

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

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

1986-08-01

387

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

E-print Network

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

Sun, Jing

388

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

SciTech Connect

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

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

2009-02-15

389

The impact of grating dispersion on transmission performance in a millimeter-wave fiber-radio system  

Microsoft Academic Search

The authors investigate the impact of fiber Bragg grating (FBG) dispersion when used as an optical filter to generate optical single sideband with carrier (OSSB + C) modulation to mitigate fiber chromatic dispersion effects in a millimeter-wave fiber-wireless system. Experimental results show that significant power penalties can occur due to grating dispersion across the bandwidth of the transmitted data. These

C. Marra; A. Nirmalathas; D. Novak; C. Lim; L. Reekie; J. A. Besley; N. J. Baker

2002-01-01

390

A global analysis of wave potential energy in the lower stratosphere derived from 5 years of GPS radio occultation data with CHAMP  

NASA Astrophysics Data System (ADS)

This paper presents the first results of the global long-term potential energy and mean potential energy per unit mass associated to wave activity (WA) in the lower and middle stratosphere, obtained from Global Positioning System radio occultation (GPS-RO) temperature profiles, retrieved during the last 5 years from the CHAMP (CHAllenging Minisatellite Payload) satellite. We excluded temperature variations corresponding to the wavelike character of the Quasi Biennial oscillation (QBO). Possible limitations and distortions expected from our analysis are pointed out. Systematic annual and interannual features, clearly evidenced through 5 years of observations as a function of height, latitude and time are shown. We confirm some previously reported characteristics, in particular interannual requiring a sufficiently long period of observation, in addition to others not reported yet. In particular, a general stronger (weaker) wave activity is observed associated to apparent vertical wavelengths longer (shorter) than 4 km. The tropical/extratropical signatures decrease/increase with increasing altitude. At equatorial latitudes, WA interannual enhancements, related to QBO, are observed just below zonal wind zero contours corresponding to westerly shears. A significant decrease of WA is seen where the zonal wind is minimum. Both at equatorial and middle latitudes, an increased WA appears close above the TP, following its annual height oscillation and above 30 km height. At higher latitudes, a systematic annual variation of WA is observed, exhibiting stronger enhancements in winter SH respect to NH, but in SH, taking place during late winter and early spring. This enhanced WA, associated during 2002 to the stratospheric warming observed in that year, appears here as a systematic annual stratospheric feature. Its intensity increases with altitude, from 25 to 35 km. Inertio-gravity waves generated by geostrophic adjustment during the maximum of the southern polar vortex (polar night jet) between late August and mid- September, could constitute a main source of this WA enhancement.

de la Torre, A.; Schmidt, T.; Wickert, J.

2006-12-01

391

Climatology of ionospheric scintillations and TEC trend over the Ugandan region  

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

392

Correlation analysis between ionospheric scintillation levels and receiver tracking performance  

NASA Astrophysics Data System (ADS)

Rapid fluctuations in the amplitude and phase of a transionospheric radio signal caused by small scale plasma density irregularities in the ionosphere are known as scintillation. Scintillation can seriously impair a GNSS (Global Navigation Satellite Systems) receiver tracking performance, thus affecting the required levels of availability, accuracy and integrity, and consequently the reliability of modern day GNSS based applications. This paper presents an analysis of correlation between scintillation levels and tracking performance of a GNSS receiver for GPS L1C/A, L2C and GLONASS L1, L2 signals. The analyses make use of data recorded over Presidente Prudente (22.1°S, 51.4°W, dip latitude ˜12.3°S) in Brazil, a location close to the Equatorial Ionisation Anomaly (EIA) crest in Latin America. The study presents for the first time this type of correlation analysis for GPS L2C and GLONASS L1, L2 signals. The scintillation levels are defined by the amplitude scintillation index, S4 and the receiver tracking performance is evaluated by the phase tracking jitter. Both S4 and the phase tracking jitter are estimated from the post correlation In-Phase (I) and Quadra-Phase (Q) components logged by the receiver at a high rate. Results reveal that the dependence of the phase tracking jitter on the scintillation levels can be represented by a quadratic fit for the signals. The results presented in this paper are of importance to GNSS users, especially in view of the forthcoming high phase of solar cycle 24 (predicted for 2013).

Sreeja, V.; Aquino, M.; Elmas, Z. G.; Forte, B.

2012-06-01

393

Ionospheric scintillation over Antarctica during the storms of 2010  

NASA Astrophysics Data System (ADS)

At the present time our knowledge of the Earth's ionosphere is dominated by measurements from the Northern Hemisphere. In spite of recent evidence indicating unexplained differences in the ionospheres from the two hemispheres, there is still very little information from the ionosphere over the Southern oceans and the Antarctic. Although the Antarctic is rather sparsely instrumented for ionospheric study, over the past decade increasing numbers of geodetic GPS receivers have been deployed there and more recently several groups have installed specialist GPS equipment for monitoring scintillation. In January 2010 a project commenced that involved the remote deployment of equipment at 81 degrees and 89 degrees South geographic. The objective of the fieldwork was to deploy GPS receiving equipment that would for the first time take simultaneous measurements of total electron content (TEC), plasma velocity and ionospheric scintillation at remote locations across the Antarctic. The paper reports on the results from the first year of data collection throughout three ionospheric storms. The first storm shows a multitude of small-scale ionospheric irregularities over the auroral and polar regions while the high-latitude ionosphere is in partial darkness. TEC is observed entering the polar cap and being broken up into a patch in a region of strong phase scintillation. The second and third storms occur in the deep Antarctic winter and show far less in the way of TEC in the polar cap; nevertheless they show strong evidence of phase scintillation and irregularities observed from multiple instruments across the polar region. The results provide new evidence for the importance of particle precipitation in causing phase scintillation in the polar regions on low-elevation GPS signals. It is anticipated that this will be useful input in forming a realistic statistical model of the irregularities in the high-latitude ionosphere that are responsible for phase and amplitude scintillation on a variety of radio signals.

Mitchell, C.; Kinrade, J.; Yin, P.; Smith, N.; Bust, G. S.; Weatherwax, A. T.; Rose, M.; Maxfield, D.; Jarvis, M. J.

2011-12-01

394

Intuitive model for the scintillations of a partially coherent beam.  

PubMed

An intuitive model for the scintillation index of a partially coherent beam is developed in which essentially the only critical parameter is the properly defined Fresnel number equal to the ratio of the "working" aperture area to the area of the Fresnel zone. The model transpired from and is supported by numerical simulations using Rytov method for weak fluctuations regime and Tatarskii turbulence spectrum with inner scale. The ratio of the scintillation index of a partially coherent beam to that of a plane wave displays a characteristic minimum, the magnitude of which and its distance from the transmitter are easily explained using the intuitive model. A theoretical asymptotic is found for the scintillation index of a source with decreasing coherence at this minimum. PMID:25607199

Efimov, Anatoly

2014-12-29

395

Empirical modelling of equatorial ionospheric scintillation  

Microsoft Academic Search

A computer-based model of ionospheric scintillations has been developed by Fremouw (socalled the WBMOD model) to give a mean scintillation index for a given set of observing conditions. The WBMOD model incorporates some of the scintillation observations made with the DNA wideband satellite. A comparison is made between the scintillation morphology observed at an equatorial station Ooty with the one

P. K. Pasricha; B. M. Reddy

1986-01-01

396

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

397

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

398

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

399

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

400

Radio telescopes  

Microsoft Academic Search

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

J. Findlay

1964-01-01

401

Detrend effect on the scalograms of GPS power scintillation  

NASA Astrophysics Data System (ADS)

The study of amplitude scintillation on GPS radio links is usually done after detrending the time series of the transmitted power so to define scintillations as the chaotic fluctuation around a unitary value. In a sense, the choice of how to detrend the time series is part of the definition of scintillation. Here we analyse how far the continuous wavelet analysis of the detrended signal is influenced by the choice of detrending. This study is done using amplitude raw data from the GPS receivers held by INGV and the University of Bath in the Northern polar region, with a sampling time of 0.02 s. Three detrending procedures are considered: a fifth degree polynomial detrending, a high-pass filter with detrending period as twice the length of the time series considered, and a high-pass filter with detrending period determined via some statistical criterion. We show that there exists a "threshold time scale" of about half minute under which the differences between the scalograms from the signals detrended in the three ways are very small. This is not changed by applying the same detrending procedures to the segment of length reduced to one-third. Consequences in terms of scintillation definition and practical applications are given.

Materassi, Massimo; Alfonsi, Lucilla; De Franceschi, Giorgiana; Romano, Vincenzo; Mitchell, Cathryn; Spalla, Paolo

2009-06-01

402

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

NASA Astrophysics Data System (ADS)

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

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

403

Radio-quiet neutron star 1E 1207.4-5209: a possible strong gravitational-wave source.  

PubMed

There are four puzzles on 1E 1207.4-5209: (1) The characteristic age of the pulsar is much higher than the estimated age of the supernova remnant; (2) the magnetic field inferred from spin down is significantly different from the value obtained from the cyclotron absorption lines; (3) the spinning down of the pulsar is nonmonotonic; (4) the magnitude of the frequency's first derivative varies significantly and its sign is also variable. The third puzzle can be explained by a wide binary system, with orbital period from 0.2 to 6 yr. This Letter proposes that all four puzzles can be explained naturally by an ultracompact binary with an orbital period between 0.5 and 3.3 min. With the shortest orbital period and a close distance of 2 kpc, the characteristic amplitude of gravitational waves is h approximately 3 x 10(-21). It would be an excellent source for gravitational-wave detectors such as the Laser Interferometer Space Antenna. PMID:16486332

Gong, Biping

2005-12-31

404

Small-area fiber-coupled scintillation camera for imaging beta-ray distributions intraoperatively  

Microsoft Academic Search

A small area, imaging, scintillation probe is being developed for locating small amounts of radio-labeled malignant tissue during surgery. Preliminary in brain surgery, avoiding the removal of excess tissue is a priority. It is possible to locate the main body of a brain tumor both before and during surgery, but once the bulk of the tumor is excised the identification

L. R. MacDonald; Martin P. Tornai; C. S. Levin; Muzaffer Atac; David B. Cline; Eric G. Hoffman

1995-01-01

405

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 is described. 11 figures.

McCollum, T.; Spector, G.B.

1994-03-29

406

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

407

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

408

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.

409

SNO+ Scintillator Purification and Assay  

Microsoft Academic Search

We describe the R&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

R. Ford; M. Chen; O. Chkvorets; D. Hallman; E. Vázquez-Jáuregui

2011-01-01

410

SNO+ Scintillator Purification and Assay  

Microsoft Academic Search

We describe the R&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

R. Ford; M. Chen; O. Chkvorets; D. Hallman; E. Va´zquez-Ja´uregui

2011-01-01

411

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

412

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

413

Comparisons of COSMIC and C/NOFS GPS Occultation Ionospheric Scintillation Measurements with Ground-based Radar and VHF Measurements  

NASA Astrophysics Data System (ADS)

Ionospheric irregularities are known to cause scintillation of trans-ionospheric radio signals and can affect space-based UHF/VHF communications, causing outages, and degrading GPS accuracy and precision. Current capability for characterizing and predicting ionospheric scintillation utilizes a network of ground-based receivers to detect scintillation and then extrapolate for short-term forecasts. Practical limits on deploying the ground receivers limits the accuracy and spatial coverage one can achieve with this approach. A more global approach is to use a set of space-based satellites equipped with GPS receivers, such as the COSMIC satellite constellation, to measure scintillations observed during so-called occultations with GPS satellites. In this paper the signal-to-noise values of GPS L1 signals received on the COSMIC and C/NOFS satellites for the portions of the occultations that are not affected by the terrestrial atmosphere are examined to help identify areas of ionospheric scintillation. Three years of S4 scintillation index values from COSMIC occultations are compared with near-zenith ground-based VHF S4 scintillation measurements from the AFRL SCIntillation Network Decision Aid (SCINDA) network stations. The data are correlated to ascertain the viability of using space-based scintillation measurements to characterize and predict scintillation to ground-based receivers. Several days of COSMIC and C/NOFS data are compared with each other and the ALTAIR radar located on Kwajalein Atoll, Marshall Islands to examine how occultation geometry affects observed scintillation and also to verify techniques that provide an upper bound on the spatial location of the ionospheric irregularities contributing to scintillations observed in the occultations.

Ruggiero, F. H.; Groves, K. M.; Straus, P. R.; Caton, R. G.; Starks, M. J.; Tanyi, K. L.; Verlinden, M.

2009-12-01

414

Electromagnetic waves  

NSDL National Science Digital Library

These pages, part of From Stargazers to Starships, explain electromagnetic waves and sunlight. Information inlcudes physiological and spectral color, spectral lines, the electromagnetic field work by Maxwell, the discovery of radio waves by Hertz, and photons and Einsteins relation. Stargazers also has detailed lesson plans accompanying these sections.

David P. Stern

2004-09-23

415

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

416

Extruded plastic scintillator including inorganic powders  

DOEpatents

A method for producing a plastic scintillator is disclosed. A plurality of nano-sized particles and one or more dopants can be combined with a plastic material for the formation of a plastic scintillator thereof. The nano-sized particles, the dopant and the plastic material can be combined within the dry inert atmosphere of an extruder to produce a reaction that results in the formation of a plastic scintillator thereof and the deposition of energy within the plastic scintillator, such that the plastic scintillator produces light signifying the detection of a radiative element. The nano-sized particles can be treated with an inert gas prior to processing the nano-sized particles, the dopant and the plastic material utilizing the extruder. The plastic scintillator can be a neutron-sensitive scintillator, x-ray sensitive scintillator and/or a scintillator for the detection of minimum ionizing particles.

Bross, Alan D.; Mellott, Kerry L.; Pla-Dalmau, Anna

2006-06-27

417

PMT calibration of a scintillation detector using primary scintillation  

NASA Astrophysics Data System (ADS)

We have studied the calibration of PMTs in scintillation detectors, inducing single electron response on the PMT from primary scintillation produced by x-ray interaction. The results agree with those obtained by the commonly used single electron response (SER) method, which uses LED light pulses to induce the PMT SER. The use of the primary scintillation for PMT calibration will be convenient in situations where the PMT is already in situ, when it becomes difficult or even impossible to apply the SER method, e.g. in commercial sealed scintillator/PMT devices. Furthermore, we have experimentally investigated the possibility of fitting the high-charge tail of the PMT SER pulse-height distribution to an exponential function, inferring the PMT gain from the inverse of the exponent. The results of the exponential fit method agree with those obtained by the SER method for pulse-height distributions resulting from an average number of around 1.0 photoelectrons reaching the first dynode per light/scintillation pulse. The SER method has higher precision and, therefore, is used in a larger number of applications. Nevertheless, the exponential fit method will be useful in situations where the single photoelectron peak is under the background or noise peak and it may present an alternative, simple way, for relative gain calibration of PMT arrays as well as for monitoring the PMT gain variations.

Freitas, E. D. C.; Fernandes, L. M. P.; Yahlali, N.; Pérez, J.; Álvarez, V.; Borges, F. I. G.; Camargo, M.; Cárcel, S.; Cebrián, S.; Cervera, A.; Conde, C. A. N.; Dafni, T.; Díaz, J.; Esteve, R.; Ferrario, P.; Ferreira, A. L.; Gehman, V. M.; Goldschmidt, A.; Gómez, H.; Gómez-Cadenas, J. J.; González Díaz, D.; Gutiérrez, R. M.; Hauptman, J.; Hernando Morata, J. A.; Herrera, D. C.; Irastorza, I. G.; Labarga, L.; Laing, A.; Liubarsky, I.; Lopez-March, N.; Lorca, D.; Losada, M.; Luzón, G.; Marí, A.; Martín-Albo, J.; Martínez, A.; Martínez Lema, G.; Miller, T.; Monrabal, F.; Monserrate, M.; Mora, F. J.; Moutinho, L. M.; Muñoz Vidal, J.; Nebot Guinot, M.; Nygren, D.; Oliveira, C. A. B.; Pérez, J.; Pérez Aparicio, J. L.; Querol, M.; Renner, J.; Ripoll, L.; Rodríguez, A.; Rodríguez, J.; Santos, F. P.; Dos Santos, J. M. F.; Seguí, L.; Serra, L.; Shuman, D.; Simón, A.; Sofka, C.; Sorel, M.; Toledo, J. F.; Torrent, J.; Tsamalaidze, Z.; Veloso, J. F. C. A.; Villar, J. A.; Webb, R.; White, J.; Monteiro, C. M. B.

2015-02-01

418

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

419

LORA: A scintillator array for LOFAR to measure extensive air showers  

E-print Network

The measurement of the radio emission from extensive air showers, induced by high-energy cosmic rays is one of the key science projects of the LOFAR radio telescope. The LOfar Radboud air shower Array (LORA) has been installed in the core of LOFAR in the Netherlands. The main purpose of LORA is to measure the properties of air showers and to trigger the read-out of the LOFAR radio antennas to register extensive air showers. The experimental set-up of the array of scintillation detectors and its performance are described.

S. Thoudam; S. Buitink; A. Corstanje; J. E. Enriquez; H. Falcke; W. Frieswijk; J. R. Hörandel; A. Horneffer; M. Krause; A. Nelles; P. Schellart; O. Scholten; S. ter Veen; M. van den Akker

2014-08-19

420

LORA: A scintillator array for LOFAR to measure extensive air showers  

NASA Astrophysics Data System (ADS)

The measurement of the radio emission from extensive air showers, induced by high-energy cosmic rays, is one of the key science projects of the LOFAR radio telescope. The LOfar Radboud air shower Array (LORA) has been installed in the core of LOFAR in the Netherlands. The main purpose of LORA is to measure the properties of air showers and to trigger the read-out of the LOFAR radio antennas to register extensive air showers. The experimental set-up of the array of scintillation detectors and its performance are described.

Thoudam, S.; Buitink, S.; Corstanje, A.; Enriquez, J. E.; Falcke, H.; Frieswijk, W.; Hörandel, J. R.; Horneffer, A.; Krause, M.; Nelles, A.; Schellart, P.; Scholten, O.; ter Veen, S.; van den Akker, M.

2014-12-01

421

Turbulence in deep radio occultations  

NASA Technical Reports Server (NTRS)

The effects of turbulence in the focal region of spherical or weakly oblate refracting bodies on the evolute flashes associated with the crossing of the evolute of the planetary limb by an occulted spacecraft are investigated. The approximate theory of focal evolutes in oblate refractivity fields developed by Eshleman et al. (1979) is combined with a generalized weak scattering scintillation theory that includes the effect of focusing around a curved limb to obtain expressions for the scintillation index and power spectrum. Results are then applied to the radio observations of the crossing of the focal evolute of Jupiter by Voyager 1, in which no flash was detected, and to the effects of the solar coronal plasma on the gravitational lens of the sun.

Haugstad, B. S.

1981-01-01

422

Cognitive radio: Making software radios more personal  

Microsoft Academic Search

Software radios are emerging as platforms for multiband multimode personal communications systems. Radio etiquette is the set of RF bands, air interfaces, protocols, and spatial and temporal patterns that moderate the use of the radio spectrum. Cognitive radio extends the software radio with radio-domain model-based reasoning about such etiquettes. Cognitive radio enhances the flexibility of personal services through a Radio

Joseph Mitola; Gerald Quentin Maguire Jr.

1999-01-01

423

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

424

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

425

Scintillation at two optical frequencies.  

PubMed

Stellar scintillation data were obtained on a single night at a variety of zenith distances and azimuths, using a photon-counting photometer recording at 100 Hz simultaneously at wavelengths of 0.475 microm and 0.870 microm. Orientable apertures of 42-cm diam separated by 1 m were used to establish the average upper atmosphere wind direction and velocity. Dispersion in the earth's atmosphere separate the average optical paths at the two wavelengths, permitting a reconstruction of the spatial cross-correlation function for scintillations, independent of assumptions about differential fluid motions. Although there is clear evidence of a complicated velocity field, scintillation power was predominantly produced by levels at pressures of 130 +/- 30 mbar. The data are not grossly inconsistent with layers of isotropic Kolmogorov turbulence, but there is some evidence for deviation from the Kolmogorov spectral index and/or anisotropy. PMID:20333125

Hubbard, W B; Reitsema, H J

1981-09-15

426

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

427

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

428

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

429

Development of radiation hard scintillators  

SciTech Connect

Substantial improvements have been made in the radiation hardness of plastic scintillators. Cylinders of scintillating materials 2.2 cm in diameter and 1 cm thick have been exposed to 10 Mrads of gamma rays at a dose rate of 1 Mrad/h in a nitrogen atmosphere. One of the formulations tested showed an immediate decrease in pulse height of only 4% and has remained stable for 12 days while annealing in air. By comparison a commercial PVT scintillator showed an immediate decrease of 58% and after 43 days of annealing in air it improved to a 14% loss. The formulated sample consisted of 70 parts by weight of Dow polystyrene, 30 pbw of pentaphenyltrimethyltrisiloxane (Dow Corning DC 705 oil), 2 pbw of p-terphenyl, 0.2 pbw of tetraphenylbutadiene, and 0.5 pbw of UVASIL299LM from Ferro.

Markley, F.; Woods, D.; Pla-Dalmau, A.; Foster, G. (Fermi National Accelerator Lab., Batavia, IL (United States)); Blackburn, R. (Michigan Univ., Nuclear Reactor Lab., Ann Arbor, MI (United States))

1992-05-01

430

Nanophosphor composite scintillator with a liquid matrix  

DOEpatents

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

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

2010-03-16

431

3D Printing of Scintillating Materials  

E-print Network

We demonstrate, for the first time, the applicability of 3D printing technique to the manufacture of scintillation detectors. We report of a formulation, usable in stereolithographic printing, that exhibits scintillation efficiency on the order of 30\\% of that of commercial polystyrene based scintillators. We discuss the applicability of these techniques and propose future enhancements that will allow tailoring the printed scintillation detectors to various application.

Mishnayot, Y; Cooperstein, I; Magdassi, S; Ron, G

2014-01-01

432

3D Printing of Scintillating Materials  

E-print Network

We demonstrate, for the first time, the applicability of 3D printing technique to the manufacture of scintillation detectors. We report of a formulation, usable in stereolithographic printing, that exhibits scintillation efficiency on the order of 30\\% of that of commercial polystyrene based scintillators. We discuss the applicability of these techniques and propose future enhancements that will allow tailoring the printed scintillation detectors to various application.

Y. Mishnayot; M. Layani; I. Cooperstein; S. Magdassi; G. Ron

2014-06-15

433

Hygroscopicity Evaluation of Halide Scintillators  

SciTech Connect

A collaborative study of relative hygroscopicity of anhydrous halide scintillators grown at various laboratories is presented. We have developed a technique to evaluate moisture sensitivity of both raw materials and grown crystals, in which the moisture absorption rate is measured using a gravimetric analysis. Degradation of the scintillation performance was investigated by recording gamma-ray spectra and monitoring the photopeak position, count rate and energy resolution. The accompanying physical degradation of the samples exposed to ambient atmosphere was photographically recorded as well. The results were compared with ben

Zhuravleva, M [The University of Tennessee] [The University of Tennessee; Stand, L [The University of Tennessee] [The University of Tennessee; Wei, H [The University of Tennessee] [The University of Tennessee; Hobbs, C. L. [University of Tennessee, Knoxville (UTK)] [University of Tennessee, Knoxville (UTK); Boatner, Lynn A [ORNL] [ORNL; Ramey, Joanne Oxendine [ORNL] [ORNL; Burger, Arnold [Fisk University, Nashville] [Fisk University, Nashville; Rowe, E [Fisk University, Nashville] [Fisk University, Nashville; Bhattacharya, P. [Fisk University, Nashville] [Fisk University, Nashville; Tupitsyn, E [Fisk University, Nashville] [Fisk University, Nashville; Melcher, Charles L [University of Tennessee, Knoxville (UTK)] [University of Tennessee, Knoxville (UTK)

2014-01-01

434

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

435

Ionospheric scintillations at L & C bands  

Microsoft Academic Search

This paper addresses the problem of ionospheric scintillations at L and C bands. The results of a L band scintillation measurement campaign are presented. The receivers used during this campaign were located in the five regions of the globe allowing to exhibit latitudinal and longitudinal dependence. Comparison with modeling has been done concurrently. The results presented for C band scintillations

Yannick Béniguel; J.-P. Adam; R. Prieto-Cerdeira; B. Arbesser-Rastburg

2009-01-01

436

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