Sample records for radio wave absorption

  1. Synopsis of Mid-latitude Radio Wave Absorption in Europe

    NASA Technical Reports Server (NTRS)

    Torkar, K. M.; Friedrich, M.

    1984-01-01

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

  2. Relations among low ionosphere parameters and high frequency radio wave absorption

    NASA Technical Reports Server (NTRS)

    Cipriano, J. P.

    1973-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Kochetov, A. V.

    2018-05-01

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

  4. On pulsating cosmic /radio/ noise absorption

    NASA Technical Reports Server (NTRS)

    Dangelo, N.

    1981-01-01

    It has been proposed that some absorption events measured on riometers are actually due to backscatter of cosmic radio noise by E-region plasma waves (D'Angelo, 1976, 1978; D'Angelo and Mehta, 1980). Assuming that DC or nearly DC absorption is a viable process, it is shown that it may also be operative in producing pulsations in cosmic noise absorption on riometers, with periods ranging from a few seconds to several minutes.

  5. Looking for radio waves with a simple radio wave detector

    NASA Astrophysics Data System (ADS)

    Sugimoto (Stray Cats), Norihiro

    2011-11-01

    I created a simple device that can detect radio waves in a classroom. In physics classes I tell students that we live in a sea of radio waves. They come from TV, radio, and cell phone signals as well as other sources. Students don't realize this because those electromagnetic waves are invisible. So, I wondered if I could come up with a way to detect the waves and help students to understand them better. Electromagnetic wave meters, which measure intensity of radio waves quantitatively, are commercially available. However, to students most of these are black boxes, and at the introductory level it is more effective to detect radio waves in a simpler way. This paper describes my device and how I have used it in my classes.

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

    NASA Technical Reports Server (NTRS)

    Gnanalingam, S.; Kane, J. A.

    1975-01-01

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

  7. Wave optics-based LEO-LEO radio occultation retrieval

    NASA Astrophysics Data System (ADS)

    Benzon, Hans-Henrik; Høeg, Per

    2016-06-01

    This paper describes the theory for performing retrieval of radio occultations that use probing frequencies in the XK and KM band. Normally, radio occultations use frequencies in the L band, and GPS satellites are used as the transmitting source, and the occultation signals are received by a GPS receiver on board a Low Earth Orbit (LEO) satellite. The technique is based on the Doppler shift imposed, by the atmosphere, on the signal emitted from the GPS satellite. Two LEO satellites are assumed in the occultations discussed in this paper, and the retrieval is also dependent on the decrease in the signal amplitude caused by atmospheric absorption. The radio wave transmitter is placed on one of these satellites, while the receiver is placed on the other LEO satellite. One of the drawbacks of normal GPS-based radio occultations is that external information is needed to calculate some of the atmospheric products such as the correct water vapor content in the atmosphere. These limitations can be overcome when a proper selected range of high-frequency waves are used to probe the atmosphere. Probing frequencies close to the absorption line of water vapor have been included, thus allowing the retrieval of the water vapor content. Selecting the correct probing frequencies would make it possible to retrieve other information such as the content of ozone. The retrieval is performed through a number of processing steps which are based on the Full Spectrum Inversion (FSI) technique. The retrieval chain is therefore a wave optics-based retrieval chain, and it is therefore possible to process measurements that include multipath. In this paper simulated LEO to LEO radio occultations based on five different frequencies are used. The five frequencies are placed in the XK or KM frequency band. This new wave optics-based retrieval chain is used on a number of examples, and the retrieved atmospheric parameters are compared to the parameters from a global European Centre for Medium

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

    DOEpatents

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

    1999-01-01

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

  9. Ionospheric modification by radio waves: An overview and novel applications

    NASA Astrophysics Data System (ADS)

    Kosch, M. J.

    2008-12-01

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

  10. Magnetospheric radio and plasma wave research - 1987-1990

    NASA Technical Reports Server (NTRS)

    Kurth, W. S.

    1991-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  12. The Unified Radio and Plasma wave investigation

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  13. H I absorption in nearby compact radio galaxies

    NASA Astrophysics Data System (ADS)

    Glowacki, M.; Allison, J. R.; Sadler, E. M.; Moss, V. A.; Curran, S. J.; Musaeva, A.; Deng, C.; Parry, R.; Sligo, M. C.

    2017-05-01

    H I absorption studies yield information on both active galactic nucleus (AGN) feeding and feedback processes. This AGN activity interacts with the neutral gas in compact radio sources, which are believed to represent the young or recently re-triggered AGN population. We present the results of a survey for H I absorption in a sample of 66 compact radio sources at 0.040 < z < 0.096 with the Australia Telescope Compact Array. In total, we obtained seven detections, five of which are new, with a large range of peak optical depths (3-87 per cent). Of the detections, 71 per cent exhibit asymmetric, broad (ΔvFWHM > 100 km s-1) features, indicative of disturbed gas kinematics. Such broad, shallow and offset features are also found within low-excitation radio galaxies which is attributed to disturbed circumnuclear gas, consistent with early-type galaxies typically devoid of a gas-rich disc. Comparing mid-infrared colours of our galaxies with H I detections indicates that narrow and deep absorption features are preferentially found in late-type and high-excitation radio galaxies in our sample. These features are attributed to gas in galactic discs. By combining XMM-Newton archival data with 21-cm data, we find support that absorbed X-ray sources may be good tracers of H I content within the host galaxy. This sample extends previous H I surveys in compact radio galaxies to lower radio luminosities and provides a basis for future work exploring the higher redshift universe.

  14. Speckles in interstellar radio-wave scattering

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  15. Information Content in Radio Waves: Student Investigations in Radio Science

    NASA Astrophysics Data System (ADS)

    Jacobs, K.; Scaduto, T.

    2013-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Nina, A.; Čadež, V. M.

    2013-09-01

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

  17. Microwave absorptivity by sulfuric acid in the Venus atmosphere derived from the Venus Express Radio Science Experiment VeRa

    NASA Astrophysics Data System (ADS)

    Oschlisniok, J.; Pätzold, M.; Häusler, B.; Tellmann, S.; Bird, M.; Andert, T.; Remus, S.; Krüger, C.; Mattei, R.

    2011-10-01

    Earth's nearest planetary neighbour Venus is shrouded within a roughly 22 km thick three-layered cloud deck, which is located approximately 48 km above the surface and extends to an altitude of about 70 km. The clouds are mostly composed of sulfuric acid. The latter is responsible for a strong absorption of radio signals at microwaves, which is observed in radio occultation experiments. The absorption of the radio signal intensity is used to determine the abundance of H2SO4. This way a detailed study of the H2SO4 height distribution within the cloud deck is possible. The Venus Express spacecraft is orbiting Venus since 2006. The Radio Science Experiment VeRa onboard probes the atmosphere with radio signals at 3.4 cm (X-Band) and 13 cm (S-Band). Absorptivity profiles of the 3.4 cm radio wave and the resulting vertical sulfuric acid profiles in the cloud region of Venus' atmosphere are presented. The three-layered structure and a distinct latitudinal variation of H2SO4 are observed. Convective atmospheric motions within the equatorial latitudes, which transport absorbing material from lower to higher altitudes, are clearly visible. Results of the Venus Monitoring Camera (VMC) and the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) are compared with the VeRa results.

  18. Full-Wave Radio Characterization of Ionospheric Modification at HAARP

    DTIC Science & Technology

    2015-07-26

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  20. Variance of transionospheric VLF wave power absorption

    NASA Astrophysics Data System (ADS)

    Tao, X.; Bortnik, J.; Friedrich, M.

    2010-07-01

    To investigate the effects of D-region electron-density variance on wave power absorption, we calculate the power reduction of very low frequency (VLF) waves propagating through the ionosphere with a full wave method using the standard ionospheric model IRI and in situ observational data. We first verify the classic absorption curves of Helliwell's using our full wave code. Then we show that the IRI model gives overall smaller wave absorption compared with Helliwell's. Using D-region electron densities measured by rockets during the past 60 years, we demonstrate that the power absorption of VLF waves is subject to large variance, even though Helliwell's absorption curves are within ±1 standard deviation of absorption values calculated from data. Finally, we use a subset of the rocket data that are more representative of the D region of middle- and low-latitude VLF wave transmitters and show that the average quiet time wave absorption is smaller than that of Helliwell's by up to 100 dB at 20 kHz and 60 dB at 2 kHz, which would make the model-observation discrepancy shown by previous work even larger. This result suggests that additional processes may be needed to explain the discrepancy.

  1. Low-frequency radio absorption in Cassiopeia A

    NASA Astrophysics Data System (ADS)

    Arias, M.; Vink, J.; de Gasperin, F.; Salas, P.; Oonk, J. B. R.; van Weeren, R. J.; van Amesfoort, A. S.; Anderson, J.; Beck, R.; Bell, M. E.; Bentum, M. J.; Best, P.; Blaauw, R.; Breitling, F.; Broderick, J. W.; Brouw, W. N.; Brüggen, M.; Butcher, H. R.; Ciardi, B.; de Geus, E.; Deller, A.; van Dijk, P. C. G.; Duscha, S.; Eislöffel, J.; Garrett, M. A.; Grießmeier, J. M.; Gunst, A. W.; van Haarlem, M. P.; Heald, G.; Hessels, J.; Hörandel, J.; Holties, H. A.; van der Horst, A. J.; Iacobelli, M.; Juette, E.; Krankowski, A.; van Leeuwen, J.; Mann, G.; McKay-Bukowski, D.; McKean, J. P.; Mulder, H.; Nelles, A.; Orru, E.; Paas, H.; Pandey-Pommier, M.; Pandey, V. N.; Pekal, R.; Pizzo, R.; Polatidis, A. G.; Reich, W.; Röttgering, H. J. A.; Rothkaehl, H.; Schwarz, D. J.; Smirnov, O.; Soida, M.; Steinmetz, M.; Tagger, M.; Thoudam, S.; Toribio, M. C.; Vocks, C.; van der Wiel, M. H. D.; Wijers, R. A. M. J.; Wucknitz, O.; Zarka, P.; Zucca, P.

    2018-05-01

    Context. Cassiopeia A is one of the best-studied supernova remnants. Its bright radio and X-ray emission is due to shocked ejecta. Cas A is rather unique in that the unshocked ejecta can also be studied: through emission in the infrared, the radio-active decay of 44Ti, and the low-frequency free-free absorption caused by cold ionised gas, which is the topic of this paper. Aims: Free-free absorption processes are affected by the mass, geometry, temperature, and ionisation conditions in the absorbing gas. Observations at the lowest radio frequencies can constrain a combination of these properties. Methods: We used Low Frequency Array (LOFAR) Low Band Antenna observations at 30-77 MHz and Very Large Array (VLA) L-band observations at 1-2 GHz to fit for internal absorption as parametrised by the emission measure. We simultaneously fit multiple UV-matched images with a common resolution of 17″ (this corresponds to 0.25 pc for a source at the distance of Cas A). The ample frequency coverage allows us separate the relative contributions from the absorbing gas, the unabsorbed front of the shell, and the absorbed back of the shell to the emission spectrum. We explored the effects that a temperature lower than the 100-500 K proposed from infrared observations and a high degree of clumping can have on the derived physical properties of the unshocked material, such as its mass and density. We also compiled integrated radio flux density measurements, fit for the absorption processes that occur in the radio band, and considered their effect on the secular decline of the source. Results: We find a mass in the unshocked ejecta of M = 2.95 ± 0.48 M⊙ for an assumed gas temperatureof T = 100 K. This estimate is reduced for colder gas temperatures and, most significantly, if the ejecta are clumped. We measure the reverse shock to have a radius of 114″± 6″ and be centred at 23:23:26, +58:48:54 (J2000). We also find that a decrease in the amount of mass in the unshocked ejecta

  2. Characteristics of coronal shock waves and solar type 2 radio bursts

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  3. X-RAYS FROM A RADIO-LOUD COMPACT BROAD ABSORPTION LINE QUASAR 1045+352 AND THE NATURE OF OUTFLOWS IN RADIO-LOUD BROAD ABSORPTION LINE QUASARS

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

    Kunert-Bajraszewska, Magdalena; Katarzynski, Krzysztof; Siemiginowska, Aneta

    2009-11-10

    We present new results on X-ray properties of radio-loud broad absorption line (BAL) quasars and focus on broadband spectral properties of a high-ionization BAL (HiBAL) compact steep spectrum (CSS) radio-loud quasar 1045+352. This HiBAL quasar has a very complex radio morphology indicating either strong interactions between a radio jet and the surrounding interstellar medium or a possible re-start of the jet activity. We detected 1045+352 quasar in a short 5 ksec Chandra ACIS-S observation. We applied theoretical models to explain spectral energy distribution of 1045+352 and argue that non-thermal, inverse-Compton (IC) emission from the innermost parts of the radio jetmore » can account for a large fraction of the observed X-ray emission. In our analysis, we also consider a scenario in which the observed X-ray emission from radio-loud BAL quasars can be a sum of IC jet X-ray emission and optically thin corona X-ray emission. We compiled a sample of radio-loud BAL quasars that were observed in X-rays to date and report no correlation between their X-ray and radio luminosity. However, the radio-loud BAL quasars show a large range of X-ray luminosities and absorption columns. This is consistent with the results obtained earlier for radio-quiet BAL quasars and may indicate an orientation effect in BAL quasars or more complex dependence between X-ray emission, radio emission, and an orientation based on the radio morphology.« less

  4. Simple simulation training system for short-wave radio station

    NASA Astrophysics Data System (ADS)

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

    2018-04-01

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

  5. The ISPM unified radio and plasma wave experiment

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

  6. Dependence of the Broad Absorption Line Quasar Fraction on Radio Luminosity

    NASA Astrophysics Data System (ADS)

    Shankar, Francesco; Dai, Xinyu; Sivakoff, Gregory R.

    2008-11-01

    We find that the fraction of classical broad absorption line quasars (BALQSOs) among the FIRST radio sources in the Sloan Data Release 3, is 20.5+ 7.3-5.9% at the faintest radio powers detected (L1.4 GHz ~ 1032 erg s-1), and rapidly drops to lesssim8% at L1.4 GHz ~ 3 × 1033 erg s-1. Similarly, adopting the broader absorption index (AI) definition of Trump et al., we find the fraction of radio BALQSOs to be 44+ 8.1-7.8%, reducing to 23.1+ 7.3-6.1% at high luminosities. While the high fraction at low radio power is consistent with the recent near-IR estimates by Dai et al., the lower fraction at high radio powers is intriguing and confirms previous claims based on smaller samples. The trend is independent of the redshift range, the optical and radio flux selection limits, or the exact definition of a radio match. We also find that at fixed optical magnitude, the highest bins of radio luminosity are preferentially populated by non-BALQSOs, consistent with the overall trend. We do find, however, that those quasars identified as AI-BALQSOs but not under the classical definition do not show a significant drop in their fraction as a function of radio power, further supporting independent claims that these sources, characterized by lower equivalent width, may represent an independent class from the classical BALQSOs. We find the balnicity index, a measure of the absorption trough in BALQSOs, and the mean maximum wind velocity to be roughly constant at all radio powers. We discuss several plausible physical models which may explain the observed fast drop in the fraction of the classical BALQSOs with increasing radio power, although none is entirely satisfactory. A strictly evolutionary model for the BALQSO and radio emission phases requires a strong fine-tuning to work, while a simple geometric model, although still not capable of explaining polar BALQSOs and the paucity of FRII BALQSOs, is statistically successful in matching the data if part of the apparent radio

  7. Antenna Construction and Propagation of Radio Waves.

    ERIC Educational Resources Information Center

    Marine Corps Inst., Washington, DC.

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

  8. Plasma and radio waves from Neptune: Source mechanisms and propagation

    NASA Astrophysics Data System (ADS)

    Wong, H. K.

    1994-03-01

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

  9. Plasma and radio waves from Neptune: Source mechanisms and propagation

    NASA Technical Reports Server (NTRS)

    Wong, H. K.

    1994-01-01

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

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

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

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

    2011-11-15

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

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

    PubMed

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

    2017-01-01

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

  12. A Study of Solar Flare Effects on Mid and High Latitude Radio Wave Propagation using SuperDARN.

    NASA Astrophysics Data System (ADS)

    Ruohoniemi, J. M.; Chakraborty, S.; Baker, J. B.

    2017-12-01

    Over the Horizon (OTH) communication is strongly dependent on the state of the ionosphere, which is sensitive to solar X-ray flares. The Super Dual Auroral Radar Network (SuperDARN), whose working principle is dependent on trans-ionospheric radio communication, uses HF radio waves to remotely sense the ionosphere. The backscatter returns from the terrestrial surface (also known as ground-scatter) transit the ionosphere four times and simulate the operation of an HF communications link. SuperDARN backscatter signal properties are altered (strongly attenuated and changes apparent phase) during a sudden ionospheric disturbance following a solar flare, commonly known as Short-Wave Fadeout or SWF. During an SWF the number of SuperDARN backscatter echoes drops suddenly (≈1 min) and sharply, often to near zero, and recovers within 30 minutes to an hour. In this study HF propagation data (SuperDARN backscatter) obtained during SWF events are analyzed for the purpose of validating and improving the performance of HF absorption models, such as, Space Weather Prediction Center (SWPC) D-region Absorption model (DRAP) and CCMC physics based AbbyNormal model. We will also present preliminary results from a physics based model for the mid and high latitude ionospheric response to flare-driven space weather anomalies, which can be used to estimate different physical parameters of the ionosphere such as electron density, collision frequency, absorption coefficients, response time of D-region etc.

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

    DOE PAGES

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

    2016-09-28

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

  14. Force-controlled absorption in a fully-nonlinear numerical wave tank

    NASA Astrophysics Data System (ADS)

    Spinneken, Johannes; Christou, Marios; Swan, Chris

    2014-09-01

    An active control methodology for the absorption of water waves in a numerical wave tank is introduced. This methodology is based upon a force-feedback technique which has previously been shown to be very effective in physical wave tanks. Unlike other methods, an a-priori knowledge of the wave conditions in the tank is not required; the absorption controller being designed to automatically respond to a wide range of wave conditions. In comparison to numerical sponge layers, effective wave absorption is achieved on the boundary, thereby minimising the spatial extent of the numerical wave tank. In contrast to the imposition of radiation conditions, the scheme is inherently capable of absorbing irregular waves. Most importantly, simultaneous generation and absorption can be achieved. This is an important advance when considering inclusion of reflective bodies within the numerical wave tank. In designing the absorption controller, an infinite impulse response filter is adopted, thereby eliminating the problem of non-causality in the controller optimisation. Two alternative controllers are considered, both implemented in a fully-nonlinear wave tank based on a multiple-flux boundary element scheme. To simplify the problem under consideration, the present analysis is limited to water waves propagating in a two-dimensional domain. The paper presents an extensive numerical validation which demonstrates the success of the method for a wide range of wave conditions including regular, focused and random waves. The numerical investigation also highlights some of the limitations of the method, particularly in simultaneously generating and absorbing large amplitude or highly-nonlinear waves. The findings of the present numerical study are directly applicable to related fields where optimum absorption is sought; these include physical wavemaking, wave power absorption and a wide range of numerical wave tank schemes.

  15. Intrinsic, Narrow N V Absorption Reveals a Clumpy Outflow in z < 0.4 Radio-Loud Quasars

    NASA Astrophysics Data System (ADS)

    DeMarcy, Bryan; Serra, Viktoriah; Culliton, Chris; Ganguly, Rajib; Runnoe, Jessie; Charlton, Jane; Eracleous, Michael; Misawa, Toru; Narayanan, Anand

    2018-01-01

    Quasar outflows are often invoked in models for galaxy evolution to inject energy and momentum into the gas in the host galaxy and influence its star formation history. Thus, the study of quasar outflows is essential for understanding galaxy evolution. N V absorption systems within the associated region (|Δv| ≤ 5000 km s-1) of the quasar are thought to be intrinsic since many show evidence for partial covering of the quasar. A recent archival study of quasar spectra taken with COS/G130M or G160M found 39/181 radio-quiet quasars show intrinsic N V absorption, while none of the 31 radio-loud quasars have N V absorption detected (Culliton et al. 2017). Further investigation of these radio-loud quasars showed a clear bias towards compact morphologies as revealed by FIRST 1.4 GHz imaging and comparatively flat radio spectra. This suggests we are viewing more face-on orientations which prevent us from seeing absorption outflows. The cause for such bias within the HST archive is still unknown; however, it could explain the lack of radio-loud intrinsic N V absorption seen by Culliton et al. (2017). Alternatively, the quasar wind structure may be fundamentally different between radio-loud and radio-quiet objects. We used COS/G130M or G160M to obtain rest-frame UV spectra (1195 Å - 1250 Å) of 14 low-redshift SDSS radio-loud quasars which show lobe-dominated FIRST morphologies to distinguish between these possibilities. Intrinsic N V absorption was detected in 6 of our 14 quasars. This suggests the lack of detections in the archival study was a result of an orientation effect/sampling bias rather than to differences in wind structure between radio-loud and radio-quiet quasars. Interestingly, we find significant overlap in radio core fractions between quasars with and without N V detection. Quasars in our sample with N V detection span a range of core fractions from < 0.01 up to 0.89 while those without detected N V range from 0.04 up to 0.93. A laminar outflow with a

  16. Ulysses radio and plasma wave observations in the Jupiter environment

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

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

    ERIC Educational Resources Information Center

    Dombi, Andra; Tunyagi, Arthur; Neda, Zoltan

    2013-01-01

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

  18. Radio Wave Generation by a Collision or Contact between Various Materials

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    In fracture of rock, radio wave emission was found experimentally [1]. This phenomenon could be used to detect a rock fracture during an earthquake or a volcanic activity [2]. The cause of the radio wave is expected to be micro-discharges, which are generated by an inhomogeneous potential distribution around micro-cracks. In order to better understand the phenomena and clarify the cause of radio wave emission, we carried out experiments to detect the emission in the cases of a collision or contact between various materials. We used receiving systems with great sensitivities and sufficient frequency bandwidths at 1 MHz-, 300 MHz-, 2 GHz-, and 18 GHz-bands. The specimen materials are as follows: Steel (2) Brass (3) Copper (4)Small coin (5)Celluloid. We obtained the following results: The signal was detected for the specimen of (1) to (4), but not for (5). The signal is composed of intermittent spikes which include waves with a frequency close to the center frequency of each frequency band. The power is strongest at the lower frequencies among all frequency bands. The more details will be given in the presentation. The origin of radio wave emission from the metal is supposed to be discharges between materials in these experiments. It is surprising that even a small coin can generate a significant amount of radio wave. Accordingly, it is inferred that all amount of charges are discharged through a conductive metal. On the other hand, celluloid did not generate radio wave, though the specimen was sufficiently charged by brushing. It is inferred that a quite localized charge was discharged but the remaining charges were blocked due to poor conductivity. Extending this hypothesis, large-scale contact should have occurred between broken fragments for the radio wave generation in the aforementioned rock fracture experiments. Turbulence of the fragments is a candidate for the explanation. [1] K. Maki et al., "An experimental study of microwave emission from compression

  19. Absorption models for low-frequency variability in compact radio sources

    NASA Technical Reports Server (NTRS)

    Marscher, A. P.

    1979-01-01

    The consequences of the most plausible version of the absorption model for low-frequency variability in compact extragalactic radio sources are considered. The general restrictions placed on such a model are determined, and observational tests are suggested that can be used either to support the model or to discriminate among its various versions. It is shown that low-frequency variability in compact radio sources can be successfully explained by a class of models in which the flux is modulated by changes in free-free optical depth within an intervening ionized medium. Two versions of such a model are distinguished, one involving large changes in optical depth and the other, small changes. It is noted that while absorption effects are capable of causing rapid flux and structural variations at centimetric wavelengths, the models predict detailed behavior that is in direct conflict with observational data.

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

    NASA Technical Reports Server (NTRS)

    Gnanalingam, S.; Kane, J. A.

    1973-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

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

  2. Absorption of acoustic waves by sunspots. II - Resonance absorption in axisymmetric fibril models

    NASA Technical Reports Server (NTRS)

    Rosenthal, C. S.

    1992-01-01

    Analytical calculations of acoustic waves scattered by sunspots which concentrate on the absorption at the magnetohydrodynamic Alfven resonance are extended to the case of a flux-tube embedded in a uniform atmosphere. The model is based on a flux-tubes of varying radius that are highly structured, translationally invariant, and axisymmetric. The absorbed fractional energy is determined for different flux-densities and subphotospheric locations with attention given to the effects of twist. When the flux is highly concentrated into annuli efficient absorption is possible even when the mean magnetic flux density is low. The model demonstrates low absorption at low azimuthal orders even in the presence of twist which generally increases the range of wave numbers over which efficient absorption can occur. Resonance absorption is concluded to be an efficient mechanism in monolithic sunspots, fibril sunspots, and plage fields.

  3. HIghZ: A search for HI absorption in high-redshift radio galaxies

    NASA Astrophysics Data System (ADS)

    Allison, J.; Callingham, J.; Sadler, E.; Wayth, R.; Curran, S.; Mahoney, E.

    2017-01-01

    We will use the unique low-frequency spectral capability of the MWA to carry out a pilot survey for neutral gas in the interstellar medium of the most distant (z>5) radio galaxies in the Universe. Through detection of the HI 21-cm line in absorption we aim to place stringent lower limits on the source redshift, confirming its location in the early Universe. Our sample makes use of the excellent wide-band spectral information available from the recently completed MWA GLEAM survey, from which we have selected a sample of ultra-steep peaked-spectrum radio sources that have a spectral turnover below 300 MHz. These sources should be ideal candidates for high-redshift compact radio galaxies since they have (a) spectral peaks that turnover below 1GHz and (b) very steep (alpha < -1.0) spectral indices that are consistent with the high density environments expected for radio galaxies in the early Universe. Using the MWA, we aim to verify this hypothesis through the detection of significant column densities of cold HI. This pathfinder project will provide important technical information that will inform future absorption surveys both with the MWA and, ultimately, the SKA-LOW telescope.

  4. Density Waves in Saturn's Rings from Cassini Radio Occultations

    NASA Astrophysics Data System (ADS)

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

    2005-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  6. Plasma and radio waves from Neptune: Source mechamisms and propagation

    NASA Technical Reports Server (NTRS)

    Menietti, J. Douglas

    1994-01-01

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

  7. Estimation of Electron Density profile Using the Propagation Characteristics of Radio Waves by S-520-29 Sounding Rocket

    NASA Astrophysics Data System (ADS)

    Itaya, K.; Ishisaka, K.; Ashihara, Y.; Abe, T.; Kumamoto, A.; Kurihara, J.

    2015-12-01

    S-520-29 sounding rocket experiment was carried out at Uchinoura Space Center (USC) at 19:10 JST on 17 August, 2014. The purpose of this sounding rocket experiments is observation of sporadic E layer that appears in the lower ionosphere at near 100km. Three methods were used in order to observe the sporadic E layer. The first method is an optical method that observe the light of metal ion emitted by the resonance scattering in sporadic E layer using the imager. The second method is observation of characteristic of radio wave propagation that the LF/MF band radio waves transmitted from the ground. The third method is measuring the electron density in the vicinity of sounding rocket using the fast Langmuir probe and the impedance probe. We analyze the propagation characteristics of radio wave in sporadic E layer appeared from the results of the second method observation. This rocket was equipped with LF/MF band radio receiver for observe the LF/MF band radio waves in rocket flight. Antenna of LF/MF band radio receiver is composed of three axis loop antenna. LF/MF band radio receiver receives three radio waves of 873kHz (JOGB), 666kHz (JOBK), 60kHz (JJY) from the ground. 873kHz and 60kHz radio waves are transmitting from north side, and 666kHz radio waves are transmitting from the east side to the trajectory of the rocket. In the sounding rocket experiment, LF/MF band radio receiver was working properly. We have completed the observation of radio wave intensity. We analyze the observation results using a Doppler shift calculations by frequency analysis. Radio waves received by the sounding rocket include the influences of Doppler shift by polarization and the direction of rocket spin and the magnetic field of the Earth. So received radio waves that are separate into characteristics waves using frequency analysis. Then we calculate the Doppler shift from the separated data. As a result, 873kHz, 666kHz radio waves are reflected by the ionosphere. 60kHz wave was able to

  8. Observation of quasi-periodic solar radio bursts associated with propagating fast-mode waves

    NASA Astrophysics Data System (ADS)

    Goddard, C. R.; Nisticò, G.; Nakariakov, V. M.; Zimovets, I. V.; White, S. M.

    2016-10-01

    Aims: Radio emission observations from the Learmonth and Bruny Island radio spectrographs are analysed to determine the nature of a train of discrete, periodic radio "sparks" (finite-bandwidth, short-duration isolated radio features) which precede a type II burst. We analyse extreme ultraviolet (EUV) imaging from SDO/AIA at multiple wavelengths and identify a series of quasi-periodic rapidly-propagating enhancements, which we interpret as a fast wave train, and link these to the detected radio features. Methods: The speeds and positions of the periodic rapidly propagating fast waves and the coronal mass ejection (CME) were recorded using running-difference images and time-distance analysis. From the frequency of the radio sparks the local electron density at the emission location was estimated for each. Using an empirical model for the scaling of density in the corona, the calculated electron density was used to obtain the height above the surface at which the emission occurs, and the propagation velocity of the emission location. Results: The period of the radio sparks, δtr = 1.78 ± 0.04 min, matches the period of the fast wave train observed at 171 Å, δtEUV = 1.7 ± 0.2 min. The inferred speed of the emission location of the radio sparks, 630 km s-1, is comparable to the measured speed of the CME leading edge, 500 km s-1, and the speeds derived from the drifting of the type II lanes. The calculated height of the radio emission (obtained from the density) matches the observed location of the CME leading edge. From the above evidence we propose that the radio sparks are caused by the quasi-periodic fast waves, and the emission is generated as they catch up and interact with the leading edge of the CME. The movie associated to Fig. 2 is available at http://www.aanda.org

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

    PubMed

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

    2010-11-01

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

  10. Whistlers, Helicons, Lower Hybrid Waves: the Physics of RF Wave Absorption Without Cyclotron Resonances

    NASA Astrophysics Data System (ADS)

    Pinsker, R. I.

    2014-10-01

    In hot magnetized plasmas, two types of linear collisionless absorption processes are used to heat and drive noninductive current: absorption at ion or electron cyclotron resonances and their harmonics, and absorption by Landau damping and the transit-time-magnetic-pumping (TTMP) interactions. This tutorial discusses the latter process, i.e., parallel interactions between rf waves and electrons in which cyclotron resonance is not involved. Electron damping by the parallel interactions can be important in the ICRF, particularly in the higher harmonic region where competing ion cyclotron damping is weak, as well as in the Lower Hybrid Range of Frequencies (LHRF), which is in the neighborhood of the geometric mean of the ion and electron cyclotron frequencies. On the other hand, absorption by parallel processes is not significant in conventional ECRF schemes. Parallel interactions are especially important for the realization of high current drive efficiency with rf waves, and an application of particular recent interest is current drive with the whistler or helicon wave at high to very high (i.e., the LHRF) ion cyclotron harmonics. The scaling of absorption by parallel interactions with wave frequency is examined and the advantages and disadvantages of fast (helicons/whistlers) and slow (lower hybrid) waves in the LHRF in the context of reactor-grade tokamak plasmas are compared. In this frequency range, both wave modes can propagate in a significant fraction of the discharge volume; the ways in which the two waves can interact with each other are considered. The use of parallel interactions to heat and drive current in practice will be illustrated with examples from past experiments; also looking forward, this tutorial will provide an overview of potential applications in tokamak reactors. Supported by the US Department of Energy under DE-FC02-04ER54698.

  11. A blind green bank telescope millimeter-wave survey for redshifted molecular absorption

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

    Kanekar, N.; Gupta, A.; Carilli, C. L.

    2014-02-10

    We present the methodology for 'blind' millimeter-wave surveys for redshifted molecular absorption in the CO/HCO{sup +} rotational lines. The frequency range 30-50 GHz appears optimal for such surveys, providing sensitivity to absorbers at z ≳ 0.85. It is critical that the survey is 'blind', i.e., based on a radio-selected sample, including sources without known redshifts. We also report results from the first large survey of this kind, using the Q-band receiver on the Green Bank Telescope (GBT) to search for molecular absorption toward 36 sources, 3 without known redshifts, over the frequency range 39.6-49.5 GHz. The GBT survey has amore » total redshift path of Δz ≈ 24, mostly at 0.81 < z < 1.91, and a sensitivity sufficient to detect equivalent H{sub 2} column densities ≳ 3 × 10{sup 21} cm{sup –2} in absorption at 5σ significance (using CO-to-H{sub 2} and HCO{sup +}-to-H{sub 2} conversion factors of the Milky Way). The survey yielded no confirmed detections of molecular absorption, yielding the 2σ upper limit n(z = 1.2) < 0.15 on the redshift number density of molecular gas at column densities N(H{sub 2}) ≳ 3 × 10{sup 21} cm{sup –2}.« less

  12. 10 GHz Standing-Wave Coplanar Stripline on LiNbO3 Crystal for Radio to Optical-Wave Conversion

    NASA Astrophysics Data System (ADS)

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

    2018-04-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  14. Cassini Radio and Plasma Wave Observations at Saturn

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

  15. Modifying the ionosphere with intense radio waves.

    PubMed

    Utlaut, W F; Cohen, R

    1971-10-15

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

  16. Millimeter-wave Absorption Studies of Molecules in Diffuse Clouds

    NASA Astrophysics Data System (ADS)

    Lucas, Robert; Liszt, Harvey S.

    1999-10-01

    With IRAM instruments in the last few years, we have been using compact extragalactic millimeter wave radio sources as background objects to study the absorption spectrum of diffuse interstellar gas at millimeter wavelengths. The molecular content of interstellar gas has turned out to be unexpectedly rich. Simple polyatomic molecules such as HCO+, C2H are quite ubiquitous near the Galactic plane (beta < 15o), and many species are detected in some directions (CO, HCO+, H2CO, HCN, HNC, CN, C2H, C3H2, H2S, CS, HCS+, SO, SiO). Remarkable proportionality relations are found between related species such as HCO+ and OH, or CN, HCN and HNC. The high abundance of some species is still a challenge for current models of diffuse cloud chemistry. A factor of 10 increase in the sensitivity will make such studies achievable in denser clouds, where the chemistry is still more active and where abundances are nowadays only available by emission measurements, and thus subject to uncertainties due to sometimes poorly understood line formation and excitation conditions.

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

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2016-01-01

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

  20. Hybridization-induced broadband terahertz wave absorption with graphene metasurfaces.

    PubMed

    Mou, Nanli; Sun, Shulin; Dong, Hongxing; Dong, Shaohua; He, Qiong; Zhou, Lei; Zhang, Long

    2018-04-30

    Electromagnetic (EM) wave absorption plays a vital role in photonics. While metasurfaces are proposed to absorb EM waves efficiently, most of them exhibit limited bandwidth and fixed functionalities. Here, we propose a broadband and tunable terahertz (THz) absorber based on a graphene-based metasurface, which is constructed by a single layer of closely patterned graphene concentric double rings and a metallic mirror separated by an ultrathin SiO 2 layer. Plasmonic hybridization between two graphene rings significantly enlarges the absorption bandwidth, which can be further tuned by gating the graphene. Moreover, the specific design also makes our device insensitive to the incident angle and polarization state of impinging EM waves. Our results may inspire certain wave-modulation-related applications, such as THz imaging, smart absorber, tunable sensor, etc.

  1. Roles Played by Electrostatic Waves in Producing Radio Emissions

    NASA Technical Reports Server (NTRS)

    Cairns, Iver H.

    2000-01-01

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

  2. Put a Short-Wave Radio in Your Foreign Language Classroom

    ERIC Educational Resources Information Center

    Oksenholt, Svein

    1977-01-01

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

  3. Spatial nonlinear absorption of Alfven waves by dissipative plasma taking account bremsstrahlung

    NASA Astrophysics Data System (ADS)

    Taiurskii, A. A.; Gavrikov, M. B.

    2016-10-01

    We study numerically the nonlinear absorption of a plane Alfven wave falling on the stationary boundary of dissipative plasma. This absorption is caused by such factors as the magnetic viscosity, hydrodynamic viscosity, and thermal conductivity of electrons and ions, bremsstrahlung and energy exchange between plasma components. The relevance of this investigation is due to some works, published in 2011, with regard to the heating mechanism of the solar corona and solar wind generation as a result of the absorption of plasma Alfven waves generated in the lower significantly colder layers of the Sun. Numerical analysis shows that the absorption of Alfven waves occurs at wavelengths of the order of skin depth, in which case the classical MHD equations are inapplicable. Therefore, our research is based on equations of two-fluid magnetohydrodynamics that take into account the inertia of the electrons. The implicit difference scheme proposed here for calculating plane-parallel flows of two-fluid plasma reveals a number of important patterns of absorption and thus allows us to study the dependence of the absorption on the Alfven wave frequency and the electron thermal conductivity and viscosity, as well as to evaluate the depth and the velocity of plasma heating during the penetration of Alfven waves interacting with dissipative plasma.

  4. Multiband coherent perfect absorption in a water-based metasurface.

    PubMed

    Zhu, Weiren; Rukhlenko, Ivan D; Xiao, Fajun; He, Chong; Geng, Junping; Liang, Xianling; Premaratne, Malin; Jin, Ronghong

    2017-07-10

    We design an ultrathin water-based metasurface capable of coherent perfect absorption (CPA) at radio frequencies. It is demonstrated that such a metasurface can almost completely absorb two symmetrically incident waves within four frequency bands, each having its own modulation depth of metasurface absorptivity. Specifically, the absorptivity at 557.2 MHz can be changed between 0.59% and 99.99% via the adjustment of the phase difference between the waves. The high angular tolerance of our metasurface is shown to enable strong CPA at oblique incidence, with the CPA frequency almost independent of the incident angle for TE waves and varying from 557.2 up to 584.2 MHz for TM waves. One can also reduce this frequency from 712.0 to 493.3 MHz while retaining strong coherent absorption by varying the water layer thickness. It is also show that the coherent absorption performance can be flexibly controlled by adjusting the temperature of water. The proposed metasurface is low-cost, biocompatible, and useful for electromagnetic modulation and switching.

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

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Wintucky, Edwin G.

    2014-01-01

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

  6. Electromagnetic Wave Absorption Coating Material with Self-Healing Properties.

    PubMed

    Wang, Ya-Min; Pan, Min; Liang, Xiang-Yong; Li, Bang-Jing; Zhang, Sheng

    2017-12-01

    Electromagnetic wave absorption coatings can effectively minimize electromagnetic radiation and are widely used in the military and civil field. However, even small scratches on the coating can lead to a large decline of absorption ability and bring serious consequences. To enhance the lifetime of electromagnetic wave absorbing coating, a kind of self-healing electromagnetic wave absorbing coating is developed by introducing host-guest interactions between the absorbing fillers and polymer matrix. After being damaged, the cracks on this coating can be healed completely with the aid of small amounts of water. Simultaneously, the electromagnetic absorbing ability of the coating is restored along with the self-healing process. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    NASA Astrophysics Data System (ADS)

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

    2018-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  9. Resonant absorption of electromagnetic waves in transition anisotropic media.

    PubMed

    Kim, Kihong

    2017-11-27

    We study the mode conversion and resonant absorption phenomena occurring in a slab of a stratified anisotropic medium, optical axes of which are tilted with respect to the direction of inhomogeneity, using the invariant imbedding theory of wave propagation. When the tilt angle is zero, mode conversion occurs if the longitudinal component of the permittivity tensor, which is the one in the direction of inhomogeneity in the non-tilted case, varies from positive to negative values within the medium, while the transverse component plays no role. When the tilt angle is nonzero, the wave transmission and absorption show an asymmetry under the sign change of the incident angle in a range of the tilt angle, while the reflection is always symmetric. We calculate the reflectance, the transmittance and the absorptance for several configurations of the permittivity tensor and find that resonant absorption is greatly enhanced when the medium from the incident surface to the resonance region is hyperbolic than when it is elliptic. For certain configurations, the transmittance and absorptance curves display sharp peaks at some incident angles determined by the tilt angle.

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

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

    NASA Astrophysics Data System (ADS)

    Osita, Ibe; Nymphas, E. F.

    2017-10-01

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

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

    NASA Astrophysics Data System (ADS)

    Tsiklauri, D.

    2014-12-01

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

  13. Long-range parametric amplification of THz wave with absorption loss exceeding parametric gain.

    PubMed

    Wang, Tsong-Dong; Huang, Yen-Chieh; Chuang, Ming-Yun; Lin, Yen-Hou; Lee, Ching-Han; Lin, Yen-Yin; Lin, Fan-Yi; Kitaeva, Galiya Kh

    2013-01-28

    Optical parametric mixing is a popular scheme to generate an idler wave at THz frequencies, although the THz wave is often absorbing in the nonlinear optical material. It is widely suggested that the useful material length for co-directional parametric mixing with strong THz-wave absorption is comparable to the THz-wave absorption length in the material. Here we show that, even in the limit of the absorption loss exceeding parametric gain, the THz idler wave can grows monotonically from optical parametric amplification over a much longer distance in a nonlinear optical material until pump depletion. The coherent production of the non-absorbing signal wave can assist the growth of the highly absorbing idler wave. We also show that, for the case of an equal input pump and signal in difference frequency generation, the quick saturation of the THz idler wave predicted from a much simplified and yet popular plane-wave model fails when fast diffraction of the THz wave from the co-propagating optical mixing waves is considered.

  14. [Acoustic detection of absorption of millimeter-band electromagnetic waves in biological objects].

    PubMed

    Polnikov, I G; Putvinskiĭ, A V

    1988-01-01

    Principles of photoacoustic spectroscopy were applied to elaborate a new method for controlling millimeter electromagnetic waves absorption in biological objects. The method was used in investigations of frequency dependence of millimeter wave power absorption in vitro and in vivo in the commonly used experimental irradiation systems.

  15. INVISIBLE ACTIVE GALACTIC NUCLEI. II. RADIO MORPHOLOGIES AND FIVE NEW H i 21 cm ABSORPTION LINE DETECTORS

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

    Yan, Ting; Stocke, John T.; Darling, Jeremy

    2016-03-15

    This is the second paper directed toward finding new highly redshifted atomic and molecular absorption lines at radio frequencies. To this end, we selected a sample of 80 candidates for obscured radio-loud active galactic nuclei (AGNs) and presented their basic optical/near-infrared (NIR) properties in Paper I. In this paper, we present both high-resolution radio continuum images for all of these sources and H i 21 cm absorption spectroscopy for a few selected sources in this sample. A-configuration 4.9 and 8.5 GHz Very Large Array continuum observations find that 52 sources are compact or have substantial compact components with size <0.″5more » and flux densities >0.1 Jy at 4.9 GHz. The 36 most compact sources were then observed with the Very Long Baseline Array at 1.4 GHz. One definite and 10 candidate Compact Symmetric Objects (CSOs) are newly identified, which is a detection rate of CSOs ∼three times higher than the detection rate previously found in purely flux-limited samples. Based on possessing compact components with high flux densities, 60 of these sources are good candidates for absorption-line searches. Twenty-seven sources were observed for H i 21 cm absorption at their photometric or spectroscopic redshifts with only six detections (five definite and one tentative). However, five of these were from a small subset of six CSOs with pure galaxy optical/NIR spectra (i.e., any AGN emission is obscured) and for which accurate spectroscopic redshifts place the redshifted 21 cm line in a radio frequency intereference (RFI)-free spectral “window” (i.e., the percentage of H i 21 cm absorption-line detections could be as high as ∼90% in this sample). It is likely that the presence of ubiquitous RFI and the absence of accurate spectroscopic redshifts preclude H i detections in similar sources (only 1 detection out of the remaining 22 sources observed, 13 of which have only photometric redshifts); that is, H i absorption may well be present but is

  16. Radio observations of atmospheric gravity waves with Callisto

    NASA Astrophysics Data System (ADS)

    Monstein, C.

    2013-12-01

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

  17. Directional Absorption of Parameterized Mountain Waves and Its Influence on the Wave Momentum Transport in the Northern Hemisphere

    NASA Astrophysics Data System (ADS)

    Xu, Xin; Tang, Ying; Wang, Yuan; Xue, Ming

    2018-03-01

    The directional absorption of mountain waves in the Northern Hemisphere is assessed by examination of horizontal wind rotation using the 2.5° × 2.5° European Centre for Medium-Range Weather Forecasts ERA-Interim reanalysis between 2011 and 2016. In the deep layer of troposphere and stratosphere, the horizontal wind rotates by more than 120° all over the Northern Hemisphere primary mountainous areas, with the rotation mainly occurring in the troposphere (stratosphere) of lower (middle to high) latitudes. The rotation of tropospheric wind increases markedly in summer over the Tibetan Plateau and Iranian Plateau, due to the influence of Asian summer monsoonal circulation. The influence of directional absorption of mountain waves on the mountain wave momentum transport is also studied using a new parameterization scheme of orographic gravity wave drag (OGWD) which accounts for the effect of directional wind shear. Owing to the directional absorption, the wave momentum flux is attenuated by more than 50% in the troposphere of lower latitudes, producing considerable orographic gravity wave lift which is normal to the mean wind. Compared with the OGWD produced in traditional schemes assuming a unidirectional wind profile, the OGWD in the new scheme is suppressed in the lower stratosphere but enhanced in the upper stratosphere and lower mesosphere. This is because the directional absorption of mountain waves in the troposphere reduces the wave amplitude in the stratosphere. Consequently, mountain waves are prone to break at higher altitudes, which favors the production of stronger OGWD given the decrease of air density with height.

  18. Preparation and electromagnetic wave absorption of RGO/Cu nanocomposite

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Tian, Xingyou; Zhang, Xian; Li, Shikuo; Shen, Yuhua; Xie, Anjian

    2017-09-01

    We use a facile pyrolysis method to prepare reduced graphene oxide and copper nanocomposite (RGO/Cu) based on it. The product shows an outstanding wave absorption properties. The maximum reflection loss is up to-50.7 dB at 3.8 GHz. The reflection loss of-10 dB (90% power absorption) corresponds to a bandwidth of 11.2 GHz (3.4-14.6 GHz range) for the layer thickness of 2-5 mm. Therefore, it is suggested that the RGO/Cu nanocomposite is also a new kind of lightweight and high-performance EM wave absorbing material.

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

    PubMed

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

    2005-03-11

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

  20. Temperature measurement using ultraviolet laser absorption of carbon dioxide behind shock waves.

    PubMed

    Oehlschlaeger, Matthew A; Davidson, David F; Jeffries, Jay B

    2005-11-01

    A diagnostic for microsecond time-resolved temperature measurements behind shock waves, using ultraviolet laser absorption of vibrationally hot carbon dioxide, is demonstrated. Continuous-wave laser radiation at 244 and 266 nm was employed to probe the spectrally smooth CO2 ultraviolet absorption, and an absorbance ratio technique was used to determine temperature. Measurements behind shock waves in both nonreacting and reacting (ignition) systems were made, and comparisons with isentropic and constant-volume calculations are reported.

  1. When galaxies collide: understanding the broad absorption-line radio galaxy 4C +72.26

    NASA Astrophysics Data System (ADS)

    Smith, D. J. B.; Simpson, C.; Swinbank, A. M.; Rawlings, S.; Jarvis, M. J.

    2010-05-01

    We present a range of new observations of the `broad absorption-line radio galaxy' 4C +72.26 (z ~ 3.5), including sensitive rest-frame ultraviolet integral field spectroscopy using the Gemini/GMOS-N instrument and Subaru/CISCO K-band imaging and spectroscopy. We show that 4C +72.26 is a system of two vigorously star-forming galaxies superimposed along the line of sight separated by ~1300 +/- 200 km s-1 in velocity, with each demonstrating spectroscopically resolved absorption lines. The most active star-forming galaxy also hosts the accreting supermassive black hole which powers the extended radio source. We conclude that the star formation is unlikely to have been induced by a shock caused by the passage of the radio jet, and instead propose that a collision is a more probable trigger for the star formation. Despite the massive starburst, the ultraviolet-mid-infrared spectral energy distribution suggests that the pre-existing stellar population comprises ~1012Msolar of stellar mass, with the current burst only contributing a further ~2 per cent, suggesting that 4C +72.26 has already assembled most of its final stellar mass.

  2. Measuring ionospheric movements using totally reflected radio waves

    NASA Astrophysics Data System (ADS)

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

    1988-02-01

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

  3. Measuring ionospheric movements using totally reflected radio waves

    NASA Astrophysics Data System (ADS)

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

    1988-02-01

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

  4. Atmospheric Waves and Dynamics Beneath Jupiters Clouds from Radio Wavelength Observations

    NASA Technical Reports Server (NTRS)

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

    2017-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1998-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Kitayama, Ken-Ichi

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-12-01

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

  8. Study of plasma-based stable and ultra-wideband electromagnetic wave absorption for stealth application

    NASA Astrophysics Data System (ADS)

    Xuyang, CHEN; Fangfang, SHEN; Yanming, LIU; Wei, AI; Xiaoping, LI

    2018-06-01

    A plasma-based stable, ultra-wideband electromagnetic (EM) wave absorber structure is studied in this paper for stealth applications. The stability is maintained by a multi-layer structure with several plasma layers and dielectric layers distributed alternately. The plasma in each plasma layer is designed to be uniform, whereas it has a discrete nonuniform distribution from the overall view of the structure. The nonuniform distribution of the plasma is the key to obtaining ultra-wideband wave absorption. A discrete Epstein distribution model is put forward to constrain the nonuniform electron density of the plasma layers, by which the wave absorption range is extended to the ultra-wideband. Then, the scattering matrix method (SMM) is employed to analyze the electromagnetic reflection and absorption of the absorber structure. In the simulation, the validation of the proposed structure and model in ultra-wideband EM wave absorption is first illustrated by comparing the nonuniform plasma model with the uniform case. Then, the influence of various parameters on the EM wave reflection of the plasma are simulated and analyzed in detail, verifying the EM wave absorption performance of the absorber. The proposed structure and model are expected to be superior in some realistic applications, such as supersonic aircraft.

  9. Ionospheric Absorption on 1539 Khz in Relation to Solar Ionizing Radiation

    NASA Technical Reports Server (NTRS)

    Boska, J.

    1984-01-01

    Radio wave absorption data on 1539 kHz for the summer period of 1978 to 1980 are considered in relation to variations of solar X-ray and L-alpha radiation. It is shown that under non-flare conditions L-alpha dominates in controlling absorption and that X-rays contribute about 10% to the total absorption. Optimum regression equations show that absorption is proportional to the m-th power of ionizing flux where m 1. The role of correcting L-alpha values, measured by the AE-E satellite, is discussed.

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

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    1987-01-01

    Laboratory measurements were conducted to evaluate properties of atmospheric gases under simulated conditions for the outer planets. A significant addition to this effort was the capability to make such measurements at millimeter wavelengths. Measurements should soon be completed on the millimeter wave absorption from ammonia under Jovian conditions. Also studied will be the feasibility of measuring the microwave and millimeter wave properties of phosphine (PH3) under simulated Jovian conditions. Further analysis and application of the laboratory results to microwave and millimeter wave absorption data for the outer planet, such as Voyager Radio Occultation experiments, will be pursued.

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

    PubMed

    Nakar, Ehud; Piran, Tsvi

    2011-09-28

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

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  14. Development of CIP/graphite composite additives for electromagnetic wave absorption applications

    NASA Astrophysics Data System (ADS)

    Woo, Soobin; Yoo, Chan-Sei; Kim, Hwijun; Lee, Mijung; Quevedo-Lopez, Manuel; Choi, Hyunjoo

    2017-09-01

    In this study, the electromagnetic (EM) wave absorption ability of carbonyl iron powder (CIP)/graphite composites produced by ball milling were studied in a range of 28.5 GHz to examine the effects of the morphology and volume fraction of graphite on EM wave absorption ability. The results indicated that a ball milling technique was effective in exfoliating the graphite and covering it with CIP, thereby markedly increasing the specific surface area of the hybrid powder. The increase in the surface area and hybridization with dielectric loss materials (i.e., graphite) improved EM absorbing properties of CIP in the range of S and X bands. Specifically, the CIP/graphite composite containing 3 wt% graphite exhibited electromagnetic wave absorption of -13 dB at 7 GHz, -21 dB at 5.8 GHz, and -29 dB at 4.3 GHz after 1 h, 8 h, and 16 h of milling, respectively. [Figure not available: see fulltext.

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

    NASA Astrophysics Data System (ADS)

    Huege, Tim; Besson, Dave

    2017-12-01

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

  16. 3.6 cm signal attenuation in Venus' lower and middle atmosphere observed by the Radio Science experiment VeRa onboard Venus Express

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  20. The Radio & Plasma Wave Investigation (RPWI) for JUICE

    NASA Astrophysics Data System (ADS)

    Wahlund, J.-E.

    2013-09-01

    We present the Radio & Plasma Waves Investigation (RPWI) selected for implementation on the JUICE mission. RPWI consists of a highly integrated instrument package that provides a whole set of plasma and fields measurements. The RPWI instrument has outstanding new capabilities not previously available to outer planet missions, and that would address many fundamental planetary science objectives. Specifically, RPWI would be able to study the electro-dynamic influence of the Jovian magnetosphere on the exospheres, surfaces and conducting oceans of Ganymede, Europa and Callisto. RPWI would also be able to monitor the sources of radio emissions from auroral regions of Ganymede and Jupiter, and possibly also from lightning activity in Jupiter's clouds. Moreover, RPWI will search for exhaust plumes from cracks on the icy moons, as well as μm-sized dust and related dust-plasmasurface interaction processes occurring near the icy moons of Jupiter.

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

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

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

    2009-02-13

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

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

    PubMed

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

    2009-02-13

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

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

    ERIC Educational Resources Information Center

    Marine Corps, Washington, DC.

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

  4. Comparison of radio frequency energy absorption in ear and eye region of children and adults at 900, 1800 and 2450 MHz.

    PubMed

    Keshvari, J; Lang, S

    2005-09-21

    The increasing use of mobile communication devices, especially mobile phones by children, has triggered discussions on whether there is a larger radio frequency (RF) energy absorption in the heads of children compared to that of adults. The objective of this study was to clarify possible differences in RF energy absorption in the head region of children and adults using computational techniques. Using the finite-difference time-domain (FDTD) computational method, a set of specific absorption rate (SAR) calculations were performed for anatomically correct adult and child head models. A half-wave dipole was used as an exposure source at 900, 1800 and 2450 MHz frequencies. The ear and eye regions were studied representing realistic exposure scenarios to current and upcoming mobile wireless communication devices. The differences in absorption were compared with the maximum energy absorption of the head model. Four magnetic resonance imaging (MRI) based head models, one female, one adult, two child head models, aged 3 and 7 years, were used. The head models greatly differ from each other in terms of size, external shape and the internal anatomy. The same tissue dielectric parameters were applied for all models. The analyses suggest that the SAR difference between adults and children is more likely caused by the general differences in the head anatomy and geometry of the individuals rather than age. It seems that the external shape of the head and the distribution of different tissues within the head play a significant role in the RF energy absorption.

  5. Atmospheric waves and dynamics beneath Jupiter's clouds from radio wavelength observations

    NASA Astrophysics Data System (ADS)

    Cosentino, Richard G.; Butler, Bryan; Sault, Bob; Morales-Juberías, Raúl; Simon, Amy; de Pater, Imke

    2017-08-01

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

  6. Effect of plasma absorption on dust lattice waves in hexagonal dust crystals

    NASA Astrophysics Data System (ADS)

    Kerong, HE; Hui, CHEN; Sanqiu, LIU

    2018-04-01

    In the present paper, the effect of plasma absorption on lattice waves in 2D hexagonal dust crystals is investigated. The dispersion relations with the effect of plasma absorption are derived. It is found that the temperature effect (electron-to-ion temperature ratio τ) enhances the frequency of the dust lattice waves, while the spatial effect (dimensionless Debye shielding parameter \\tilde{κ }) weakens the frequency of the dust lattice waves. In addition, the system stabilities under the conditions of plasma absorption are studied. It is found that the temperature effect narrows the range of instability, while the spatial effect extends this range. And the range of instability is calculated, i.e. the system will always in the stable state regardless of the value of \\tilde{κ } when τ > 3.5. However, the system will be unstable when τ = 1 and \\tilde{κ }> 4.1.

  7. The radio power reflected from rough and undulating ionospheric surfaces

    NASA Astrophysics Data System (ADS)

    Whitehead, J. D.; From, W. R.; Smith, L. G.

    1984-08-01

    It is shown for both rough and undulating surfaces that the mean radio power reflected by the ionosphere averaged over a sufficiently long time is exactly the same as for a smooth flat surface at the same height provided the sounder is equally sensitive for echoes from all directions. When making radio wave absorption measurements under spread conditions the total integrated power over the whole time the direct echoes are being received must be used but the distance attenuation factor must be calculated from the time of arrival of the first echo.

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

    NASA Astrophysics Data System (ADS)

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

    2017-06-01

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

  9. Research on a new wave energy absorption device

    NASA Astrophysics Data System (ADS)

    Lu, Zhongyue; Shang, Jianzhong; Luo, Zirong; Sun, Chongfei; Zhu, Yiming

    2018-01-01

    To reduce impact of global warming and the energy crisis problems caused by pollution of energy combustion, the research on renewable and clean energies becomes more and more important. This paper designed a new wave absorption device, and also gave an introduction on its mechanical structure. The flow tube model is analyzed, and presented the formulation of the proposed method. To verify the principle of wave absorbing device, an experiment was carried out in a laboratory environment, and the results of the experiment can be applied for optimizing the structure design of output power.

  10. Systems having optical absorption layer for mid and long wave infrared and methods for making the same

    DOEpatents

    Kuzmenko, Paul J

    2013-10-01

    An optical system according to one embodiment includes a substrate; and an optical absorption layer coupled to the substrate, wherein the optical absorption layer comprises a layer of diamond-like carbon, wherein the optical absorption layer absorbs at least 50% of mid wave infrared light (3-5 .mu.m wavelength) and at least 50% of long wave infrared light (8-13 .mu.m wavelength). A method for applying an optical absorption layer to an optical system according to another embodiment includes depositing a layer of diamond-like carbon of an optical absorption layer above a substrate using plasma enhanced chemical vapor deposition, wherein the optical absorption layer absorbs at least 50% of mid wave infrared light (3-5 .mu.m wavelength) and at least 50% of long wave infrared light (8-13 .mu.m wavelength). Additional systems and methods are also presented.

  11. Helicon mode formation and radio frequency power deposition in a helicon-produced plasma

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

    Niemi, K.; Kraemer, M.

    2008-07-15

    Time- and space-resolved magnetic (B-dot) probe measurements in combination with measurements of the plasma parameters were carried out to investigate the relationship between the formation and propagation of helicon modes and the radio frequency (rf) power deposition in the core of a helicon plasma. The Poynting flux and the absorbed power density are deduced from the measured rf magnetic field distribution in amplitude and phase. Special attention is devoted to the helicon absorption under linear and nonlinear conditions. The present investigations are attached to recent observations in which the nonlinear nature of the helicon wave absorption has been demonstrated bymore » showing that the strong absorption of helicon waves is correlated with parametric excitation of electrostatic fluctuations.« less

  12. SDN based millimetre wave radio over fiber (RoF) network

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

    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

  13. Propagation of radio frequency waves through density fluctuations

    NASA Astrophysics Data System (ADS)

    Valvis, S. I.; Papagiannis, P.; Papadopoulos, A.; Hizanidis, K.; Glytsis, E.; Bairaktaris, F.; Zisis, A.; Tigelis, I.; Ram, A. K.

    2017-10-01

    On their way to the core of a tokamak plasma, radio frequency (RF) waves, excited in the vacuum region, have to propagate through a variety of density fluctuations in the edge region. These fluctuations include coherent structures, like blobs that can be field aligned or not, as well as turbulent and filamentary structures. We have been studying the effect of fluctuations on RF propagation using both theoretical (analytical) and computational models. The theoretical results are being compared with those obtained by two different numerical codes ``a Finite Difference Frequency Domain code and the commercial COMSOL package. For plasmas with arbitrary distribution of coherent and turbulent fluctuations, we have formulated an effective dielectric permittivity of the edge plasma. This permittivity tensor is then used in numerical simulations to study the effect of multi-scale turbulence on RF waves. We not only consider plane waves but also Gaussian beams in the electron cyclotron and lower hybrid range of frequencies. The analytical theory and results from simulations on the propagation of RF waves will be presented. Supported in part by the Hellenic National Programme on Controlled Thermonuclear Fusion associated with the EUROfusion Consortium and by DoE Grant DE-FG02-91ER-54109.

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

    NASA Astrophysics Data System (ADS)

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

    2018-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Tsiklauri, David

    2015-04-01

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

  16. Attosecond transient absorption of a bound wave packet coupled to a smooth continuum

    DOE PAGES

    Dahlström, Jan Marcus; Pabst, Stefan; Lindroth, Eva

    2017-10-16

    Here, we investigate the possibility of using transient absorption of a coherent bound electron wave packet in hydrogen as an attosecond pulse characterization technique. In a recent work, we have shown that photoionization of such a coherent bound electron wave packet opens up for pulse characterization with unprecedented temporal accuracy—independent of the atomic structure—with maximal photoemission at all kinetic energies given a wave packet with zero relative phase. Here, we perform numerical propagation of the time-dependent Schrödinger equation and analytical calculations based on perturbation theory to show that the energy-resolved maximal absorption of photons from the attosecond pulse does not uniquely occur at a zero relative phase of the initial wave packet. Instead, maximal absorption occurs at different relative wave packet phases, distributed as a non-monotonous function with a smoothmore » $$-\\pi /2$$ shift across the central photon energy (given a Fourier-limited Gaussian pulse). Similar results are also found in helium. Our finding is surprising, because it implies that the energy-resolved photoelectrons are not mapped one-to-one with the energy-resolved absorbed photons of the attosecond pulse.« less

  17. Attosecond transient absorption of a bound wave packet coupled to a smooth continuum

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

    Dahlström, Jan Marcus; Pabst, Stefan; Lindroth, Eva

    Here, we investigate the possibility of using transient absorption of a coherent bound electron wave packet in hydrogen as an attosecond pulse characterization technique. In a recent work, we have shown that photoionization of such a coherent bound electron wave packet opens up for pulse characterization with unprecedented temporal accuracy—independent of the atomic structure—with maximal photoemission at all kinetic energies given a wave packet with zero relative phase. Here, we perform numerical propagation of the time-dependent Schrödinger equation and analytical calculations based on perturbation theory to show that the energy-resolved maximal absorption of photons from the attosecond pulse does not uniquely occur at a zero relative phase of the initial wave packet. Instead, maximal absorption occurs at different relative wave packet phases, distributed as a non-monotonous function with a smoothmore » $$-\\pi /2$$ shift across the central photon energy (given a Fourier-limited Gaussian pulse). Similar results are also found in helium. Our finding is surprising, because it implies that the energy-resolved photoelectrons are not mapped one-to-one with the energy-resolved absorbed photons of the attosecond pulse.« less

  18. Radio Wave Propagation Handbook for Communication on and Around Mars

    NASA Technical Reports Server (NTRS)

    Ho, Christian; Golshan, Nasser; Kliore, Arvydas

    2002-01-01

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

  19. Laser absorption waves in metallic capillaries

    NASA Astrophysics Data System (ADS)

    Anisimov, V. N.; Arutiunian, R. V.; Bol'Shov, L. A.; Kanevskii, M. F.; Kondrashov, V. V.

    1987-07-01

    The propagation of laser absorption waves in metallic capillaries was studied experimentally and numerically during pulsed exposure to CO2 laser radiation. The dependence of the plasma front propagation rate on the initial air pressure in the capillary is determined. In a broad range of parameters, the formation time of the optically opaque plasma layer is governed by the total laser pulse energy from the beginning of the exposure to the instant screening appears, and is weakly dependent on the pulse shape and gas pressure.

  20. Improved Modeling of Midlatitude D-Region Ionospheric Absorption of High Frequency Radio Signals During Solar X-Ray Flares

    DTIC Science & Technology

    2009-06-01

    a physics-based model which calculates mid - latitude ionospheric electron and ion density profiles for prediction of HF propagation and absorption...greatest in the summer due to longer periods of daylight and ionization. For times not close to sunrise or sunset, mid - latitude ionospheric ...IMPROVED MODELING OF MIDLATITUDE D-REGION IONOSPHERIC ABSORPTION OF HIGH FREQUENCY RADIO SIGNALS DURING SOLAR X-RAY FLARES 1

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  2. High Power Radio Wave Interactions within the D-Region Ionosphere

    NASA Astrophysics Data System (ADS)

    Moore, R. C.

    2014-12-01

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

  3. Evanescent Wave Absorption Based Fiber Sensor for Measuring Glucose Solution Concentration

    NASA Astrophysics Data System (ADS)

    Marzuki, Ahmad; Candra Pratiwi, Arni; Suryanti, Venty

    2018-03-01

    An optical fiber sensor based on evanescent wave absorption designed for measuring glucose solution consentration was proposed. The sensor was made to detect absorbance of various wavelength in the glucose solution. The sensing element was fabricated by side polishing of multimode polymer optical fiber to form a D-shape. The sensing element was immersed in different concentration of glucoce solution. As light propagated through the optical fiber, the evanescent wave interacted with the glucose solution. Light was absorbed by the glucose solution. The larger concentration the glucose solution has, the more the evanescent wave was absorbed in particular wavelenght. Here in this paper, light absorbtion as function of glucose concentration was measured as function of wavelength (the color of LED). We have shown that the proposed sensor can demonstrated an increase of light absorption as function of glucose concentration.

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  5. Searching for Correlated Radio Transients & Gravitational Wave Bursts

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

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

  6. Electromagnetic wave absorption properties of cement based composites using helical carbon fibers as absorbent

    NASA Astrophysics Data System (ADS)

    Xie, Shuai; Wang, Jing; Wang, Wufeng; Hou, Guoyan; Li, Bin; Shui, Zhonghe; Ji, Zhijiang

    2018-02-01

    In order to develop a cement based composites with high electromagnetic (EM) wave absorbing performance, helical carbon fibers (HCFs) were added into the cement matrix as an absorbent. The reflection loss (RL) of the prepared HCFs/cement based composites was studied by arched testing method in the frequency ranges of 1-8 GHz and 8-18 GHz. The results show that the EM wave absorption properties of the cement based composites can be evidently enhanced by the addition of HCFs. The composites with 1.5% HCFs exhibits optimum EM wave absorption performance in the frequency range of 1-8 GHz. However, in 8-18 GHz frequency range, the EM wave absorption performance of the cement composites with 1% HCFs is much better than others. The RL values of the prepared HCFs/cement based composites are less than -5 dB in the whole testing frequency regions, which can be attributed to the strong dielectric loss ability and unique chiral structure of HCFs.

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

    PubMed

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

    2011-06-01

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

  8. Physics of the Geospace Response to Powerful HF Radio Waves

    DTIC Science & Technology

    2012-10-31

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

  9. Millimeter-Wave Absorption as a Quality Control Tool for M-Type Hexaferrite Nanopowders

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

    McCloy, John S.; Korolev, Konstantin A.; Crum, Jarrod V.

    2013-01-01

    Millimeter wave (MMW) absorption measurements have been conducted on commercial samples of large (micrometer-sized) and small (nanometer-sized) particles of BaFe12O19 and SrFe12O19 using a quasi-optical MMW spectrometer and a series of backwards wave oscillators encompassing the 30-120 GHz range. Effective anisotropy of the particles calculated from the resonant absorption frequency indicates lower overall anisotropy in the nano-particles. Due to their high magnetocrystalline anisotropy, both BaFe12O19 and SrFe12O19 are expected to have spin resonances in the 45-55 GHz range. Several of the sampled BaFe12O19 powders did not have MMW absorptions, so they were further investigated by DC magnetization and x-ray diffractionmore » to assess magnetic behavior and structure. The samples with absent MMW absorption contained primarily iron oxides, suggesting that MMW absorption could be used for quality control in hexaferrite powder manufacture.« less

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

    NASA Astrophysics Data System (ADS)

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

    2017-10-01

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

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

    NASA Technical Reports Server (NTRS)

    Kurth, W. S.

    2001-01-01

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

  12. Supporting Structure of the LSD Wave in an Energy Absorption Perspective

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

    Fukui, Akihiro; Hatai, Keigo; Cho, Shinatora

    In Repetitively Pulsed (RP) Laser Propulsion, laser energy irradiated to a vehicle is converted to blast wave enthalpy during the Laser Supported Detonation (LSD) regime. Based on the measured post-LSD electron number density profiles by two-wavelength Mach Zehnder interferometer in a line-focusing optics, electron temperature and absorption coefficient were estimated assuming Local Thermal Equilibrium. A 10J/pulse CO{sub 2} laser was used. As a result, laser absorption was found completed in the layer between the shock wave and the electron density peak. Although the LSD-termination timing was not clear from the shock-front/ionization-front separation in the shadowgraph images, there observed drastic changesmore » in the absorption layer thickness from 0.2 mm to 0.5 mm and in the peak heating rate from 12-17x10{sup 13} kW/m{sup 3} to 5x10{sup 13} kW/m{sup 3} at the termination.« less

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

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    1988-01-01

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

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

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

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

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

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

    NASA Astrophysics Data System (ADS)

    Magdalenic, Jasmina

    2016-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  17. The integrated radio continuum spectrum of M33 - Evidence for free-free absorption by cool ionized gas

    NASA Technical Reports Server (NTRS)

    Israel, F. P.; Mahoney, M. J.; Howarth, N.

    1992-01-01

    We present measurements of the integrated radio continuum flux density of M33 at frequencies between 22 and 610 MHz and discuss the radio continuum spectrum of M33 between 22 MHz and 10 GHz. This spectrum has a turnover between 500 and 900 MHz, depending on the steepness of the high frequency radio spectrum of M33. Below 500 MHz the spectrum is relatively flat. We discuss possible mechanisms to explain this spectral shape and consider efficient free-free absorption of nonthermal emission by a cool (not greater than 1000 K) ionized gas to be a very likely possibility. The surface filling factor of both the nonthermal and the thermal material appears to be small (of order 0.001), which could be explained by magnetic field/density fluctuations in the M 33 interstellar medium. We briefly speculate on the possible presence of a nuclear radio source with a steep spectrum.

  18. Millimeter-wave spectra of the Jovian planets

    NASA Technical Reports Server (NTRS)

    Joiner, Joanna; Steffes, Paul G.

    1991-01-01

    The millimeter wave portion of the electromagnetic spectrum is critical for understanding the subcloud atmospheric structure of the Jovian planets (Jupiter, Saturn, Uranus, and Neptune). This research utilizes a combination of laboratory measurements, computer modeling, and radio astronomical observation in order to obtain a better understanding of the millimeter-wave spectra of the Jovian planets. The pressure broadened absorption from gaseous ammonia (NH3) and hydrogen sulfide (H2S) was measured in the laboratory under simulated conditions for the Jovian atmospheres. Researchers developed new formalisms for computing the absorptivity of gaseous NH3 and H2S based on their laboratory measurements. They developed a radiative transfer and thermochemical model to predict the abundance and distribution of absorbing constituents in the Jovian atmospheres. They used the model to compute the millimeter wave emission from the Jovian planets.

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

    NASA Astrophysics Data System (ADS)

    Kuley, Animesh; Bao, Jian; Lin, Zhihong

    2015-11-01

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

  20. Fabrication process and electromagnetic wave absorption characterization of a CNT/Ni/epoxy nanocomposite.

    PubMed

    Ryu, Seongwoo; Mo, Chan Bin; Lee, Haeshin; Hong, Soon Hyung

    2013-11-01

    Since carbon nanotube (CNT) was first discovered in 1991, it has been considered as a viable type of conductive filler for electromagnetic wave absorption materials in the GHz range. In this paper, pearl-necklace-structure CNT/Ni nano-powders were fabricated by a polyol process as conductive fillers. Compared to synthesized CNT, pearl-necklace Ni-decorated CNT increased the electrical conductivity by an order of 1 due to the enhancement of the Ni-conductive network. Moreover, the decorated Ni particles prevented the agglomeration of CNTs by counterbalancing the Van der Walls interaction between the CNTs. A CNT/Ni nanocomposite showed a homogeneous dispersion in an epoxy-based matrix. This enhanced physical morphology and electrical properties lead to an increase in the loss tangent and reflection loss in the CNT/Ni/Epoxy nanocomposite compared to these characteristics of a CNT/Epoxy nanocomposite in range of 8-12 GHz. The electromagnetic wave absorption properties of CNT/Ni/epoxy nanocomposites will provide enormous opportunities for electronic applications where lightweight EMI shielding or electro-magnetic wave absorption properties are necessary.

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

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    1988-01-01

    Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments and earth-based radio astronomical observations can be used to infer abundances of microwave absorbing atmospheric constituents in those atmospheres, as long as reliable information regarding the microwave absorbing properties of potential constituents is available. The key activity for this grant year has continued to be laboratory measurements of the microwave and millimeter-wave properties of the simulated atmospheres of the outer planets and their satellites. A Fabry-Perot spectrometer system capable of operation from 32 to 41 GHz was developed. Initially this spectrometer was used to complete laboratory measurements of the 7.5 to 9.3 mm absorption spectrum of ammonia. Laboratory measurements were begun at wavelengths near 3.2 mm, where a large number of observations of the emission from the outer planets were made. A description of this system is presented.

  2. Emission, absorption and group delay of microwaves in the atmosphere in relation to water vapour content over the Indian subcontinent

    NASA Technical Reports Server (NTRS)

    Sen, A. K.; Gupta, A. K. D.; Karmakar, P. K.; Barman, S. D.; Bhattacharya, A. B.; Purkait, N.; Gupta, M. K. D.; Sehra, J. S.

    1985-01-01

    The advent of satellite communication for global coverage has apparently indicated a renewed interest in the studies of radio wave propagation through the atmosphere, in the VHF, UHF and microwave bands. The extensive measurements of atmosphere constituents, dynamics and radio meterological parameters during the Middle Atmosphere Program (MAP) have opened up further the possibilities of studying tropospheric radio wave propagation parameters, relevant to Earth/space link design. The three basic parameters of significance to radio propagation are thermal emission, absorption and group delay of the atmosphere, all of which are controlled largely by the water vapor content in the atmosphere, particular at microwave bands. As good emitters are also good absorbers, the atmospheric emission as well as the absorption attains a maximum at the frequency of 22.235 GHz, which is the peak of the water vapor line. The group delay is practically independent of frequency in the VHF, UHF and microwave bands. However, all three parameters exhibit a similar seasonal dependence originating presumably from the seasonal dependence of the water vapor content. Some of the interesting results obtained from analyses of radiosonde data over the Indian subcontinent collected by the India Meteorological Department is presented.

  3. The lower ionosphere response to its disturbances by powerful radio waves

    NASA Astrophysics Data System (ADS)

    Bakhmetieva, N. V.; Frolov, V. L.; Vyakhirev, V. D.; Kalinina, E. E.; Akchurin, A. D.; Zykov, E. Yu.

    2018-04-01

    The paper presents data from some campaigns at Sura heating facility in 2011-1016. The experiments on probing of the artificial disturbed region of the lower ionosphere were carried out at two observation sites. One of them was located near Vasil'sursk 1 km from Sura facility (56.1°N; 46.1°E) and the other site was located at the Observatory (55.85°N; 48.8°E) of Kazan State University, 170 km to the East. Investigation of the features of the disturbed region of the lower ionosphere based on its diagnostics by the methods of the vertical sounding and oblique backscattering is the main goal of this paper. Ionosphere disturbance was fulfilled by the effect of the powerful radio wave of the ordinary or extraordinary polarization emitted by transmitters of the Sura facility with effective radiated power ERP = 50-120 MW at the frequency of 4.3, 4.7 and 5.6 MHz. Pumping waves were emitted with period from 30 s to 15 min. The disturbed region of the ionosphere in Vasil'sursk was probed by the vertical sounding technique using the partial reflexion radar at the frequency of 2.95 and 4.7 MHz. For the oblique sounding of the disturbed region the modified ionosonde Cyclon-M, operating at ten frequencies from 2.01 to 6.51 MHz was used at the Observatory site. On many heating sessions simultaneous variations of the probing partial reflection signals in Vasil'sursk and backscattered signals in Observatory were observed at the height at 40-100 km below the reflection height of the pumping wave. These observations were correlated with the pumping periods of the Sura facility. Possible mechanisms of the appearance of the disturbance in the lower ionosphere and its effect on the probing radio waves are discussed.

  4. Numerical calculations of spectral turnover and synchrotron self-absorption in CSS and GPS radio sources

    NASA Astrophysics Data System (ADS)

    Jeyakumar, S.

    2016-06-01

    The dependence of the turnover frequency on the linear size is presented for a sample of Giga-hertz Peaked Spectrum and Compact Steep Spectrum radio sources derived from complete samples. The dependence of the luminosity of the emission at the peak frequency with the linear size and the peak frequency is also presented for the galaxies in the sample. The luminosity of the smaller sources evolve strongly with the linear size. Optical depth effects have been included to the 3D model for the radio source of Kaiser to study the spectral turnover. Using this model, the observed trend can be explained by synchrotron self-absorption. The observed trend in the peak-frequency-linear-size plane is not affected by the luminosity evolution of the sources.

  5. Reflected ray retrieval from radio occultation data using radio holographic filtering of wave fields in ray space

    NASA Astrophysics Data System (ADS)

    Gorbunov, Michael E.; Cardellach, Estel; Lauritsen, Kent B.

    2018-03-01

    Linear and non-linear representations of wave fields constitute the basis of modern algorithms for analysis of radio occultation (RO) data. Linear representations are implemented by Fourier Integral Operators, which allow for high-resolution retrieval of bending angles. Non-linear representations include Wigner Distribution Function (WDF), which equals the pseudo-density of energy in the ray space. Representations allow for filtering wave fields by suppressing some areas of the ray space and mapping the field back from the transformed space to the initial one. We apply this technique to the retrieval of reflected rays from RO observations. The use of reflected rays may increase the accuracy of the retrieval of the atmospheric refractivity. Reflected rays can be identified by the visual inspection of WDF or spectrogram plots. Numerous examples from COSMIC data indicate that reflections are mostly observed over oceans or snow, in particular over Antarctica. We introduce the reflection index that characterizes the relative intensity of the reflected ray with respect to the direct ray. The index allows for the automatic identification of events with reflections. We use the radio holographic estimate of the errors of the retrieved bending angle profiles of reflected rays. A comparison of indices evaluated for a large base of events including the visual identification of reflections indicated a good agreement with our definition of reflection index.

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

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    1989-01-01

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

  7. The 5-day wave and ionospheric absorption

    NASA Technical Reports Server (NTRS)

    Fraser, G. J.

    1977-01-01

    In a previous paper, Fraser and Thorpe (1976) indicated that the average partial-coherence spectra for three summers and the average for three winters at a southern mid-latitude site had a dominant peak at a period of about six days. This peak in coherence between absorption and temperature is anomalous, and the present paper explains how some of the unexpected coherence features can be explained by the five-day wave described by Geisler and Dickinson (1976) and whose existence in the upper stratosphere was discussed by Rodgers (1976).

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

    NASA Astrophysics Data System (ADS)

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

    2017-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-10-01

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

  10. Characteristic analysis of surface waves in a sensitive plasma absorption probe

    NASA Astrophysics Data System (ADS)

    You, Wei; Li, Hong; Tan, Mingsheng; Liu, Wandong

    2018-01-01

    With features that are simple to construct and a symmetric configuration, the sensitive plasma absorption probe (SPAP) is a dependable probe for industry plasma diagnosis. The minimum peak in the characteristic curve of the coefficient of reflection stems from the surface wave resonance in plasma. We use numerical simulation methods to analyse the details of the excitation and propagation of these surface waves. With this method, the electromagnetic field structure and the resonance and propagation characteristics of the surface wave were analyzed simultaneously using the simulation method. For this SPAP structure, there are three different propagation paths for the propagating plasma surface wave. The propagation characteristic of the surface wave along each path is presented. Its dispersion relation is also calculated. The objective is to complete the relevant theory of the SPAP as well as the propagation process of the plasma surface wave.

  11. Resonant behavior of MHD waves on magnetic flux tubes. IV - Total resonant absorption and MHD radiating eigenmodes

    NASA Technical Reports Server (NTRS)

    Goossens, Marcel; Hollweg, Joseph V.

    1993-01-01

    Resonant absorption of MHD waves on a nonuniform flux tube is investigated as a driven problem for a 1D cylindrical equilibrium. The variation of the fractional absorption is studied as a function of the frequency and its relation to the eigenvalue problem of the MHD radiating eigenmodes of the nonuniform flux tube is established. The optimal frequencies producing maximal fractional absorption are determined and the condition for total absorption is obtained. This condition defines an impedance matching and is fulfilled for an equilibrium that is fine tuned with respect to the incoming wave. The variation of the spatial wave solutions with respect to the frequency is explained as due to the variation of the real and imaginary parts of the dispersion relation of the MHD radiating eigenmodes with respect to the real driving frequency.

  12. Pioneer-Venus radio occultation (ORO) data reduction: Profiles of 13 cm absorptivity

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    1990-01-01

    In order to characterize possible variations in the abundance and distribution of subcloud sulfuric acid vapor, 13 cm radio occultation signals from 23 orbits that occurred in late 1986 and 1987 (Season 10) and 7 orbits that occurred in 1979 (Season 1) were processed. The data were inverted via inverse Abel transform to produce 13 cm absorptivity profiles. Pressure and temperature profiles obtained with the Pioneer-Venus night probe and the northern probe were used along with the absorptivity profiles to infer upper limits for vertical profiles of the abundance of gaseous H2SO4. In addition to inverting the data, error bars were placed on the absorptivity profiles and H2SO4 abundance profiles using the standard propagation of errors. These error bars were developed by considering the effects of statistical errors only. The profiles show a distinct pattern with regard to latitude which is consistent with latitude variations observed in data obtained during the occultation seasons nos. 1 and 2. However, when compared with the earlier data, the recent occultation studies suggest that the amount of sulfuric acid vapor occurring at and below the main cloud layer may have decreased between early 1979 and late 1986.

  13. Absorption and Modification of Lower Hybrid Waves in the Scrape Off Layer

    NASA Astrophysics Data System (ADS)

    Parker, R.; Wallace, G.; Shiraiwa, S.; Baek, S.-G.; Faust, I.

    2015-11-01

    Loss of current drive efficiency of lower hybrid waves at high density in Alcator C-Mod current drive experiments has been attributed, at least in part, to interactions in the SOL. While ray-tracing calculations indicate that collisional absorption and modification of n|| during reflections in the SOL can be significant, their validity can be called into question owing to steep SOL gradients. In order to further quantify these losses, full-wave calculations using a plane-stratified SOL model have been carried out. The results show that the loss resulting from reflections in the SOL can be substantial, with collisional losses accounting for a loss of up to 50% per bounce of the incident wave power. The loss is sensitive to the SOL parameters with the strongest collisional absorption occurring in the case of steep temperature and weak density gradients. Modification of n|| can also be significant when the density gradient and normal to the flux surfaces are not aligned. These effects are less severe for the fast wave since its penetration into the SOL is significantly less than that of the slow wave. Work supported by USDoE awards DE-FC02-99ER54512 and DE-AC02-09CH11466.

  14. Nonlinear interaction of an intense radio wave with ionospheric D/E layer plasma

    NASA Astrophysics Data System (ADS)

    Sodha, Mahendra Singh; Agarwal, Sujeet Kumar

    2018-05-01

    This paper considers the nonlinear interaction of an intense electromagnetic wave with the D/E layer plasma in the ionosphere. A simultaneous solution of the electromagnetic wave equation and the equations describing the kinetics of D/E layer plasma is obtained; the phenomenon of ohmic heating of electrons by the electric field of the wave causes enhanced collision frequency and ionization of neutral species. Electron temperature dependent recombination of electrons with ions, electron attachment to O 2 molecules, and detachment of electrons from O2 - ions has also been taken into account. The dependence of the plasma parameters on the square of the electric vector of the wave E0 2 has been evaluated for three ionospheric heights (viz., 90, 100, and 110 km) corresponding to the mid-latitude mid-day ionosphere and discussed; these results are used to investigate the horizontal propagation of an intense radio wave at these heights.

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

    NASA Astrophysics Data System (ADS)

    Puchkov, V. A.

    2016-09-01

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

  16. Theoretical requirements for broadband perfect absorption of acoustic waves by ultra-thin elastic meta-films

    PubMed Central

    Duan, Yuetao; Luo, Jie; Wang, Guanghao; Hang, Zhi Hong; Hou, Bo; Li, Jensen; Sheng, Ping; Lai, Yun

    2015-01-01

    We derive and numerically demonstrate that perfect absorption of elastic waves can be achieved in two types of ultra-thin elastic meta-films: one requires a large value of almost pure imaginary effective mass density and a free space boundary, while the other requires a small value of almost pure imaginary effective modulus and a hard wall boundary. When the pure imaginary density or modulus exhibits certain frequency dispersions, the perfect absorption effect becomes broadband, even in the low frequency regime. Through a model analysis, we find that such almost pure imaginary effective mass density with required dispersion for perfect absorption can be achieved by elastic metamaterials with large damping. Our work provides a feasible approach to realize broadband perfect absorption of elastic waves in ultra-thin films. PMID:26184117

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  18. Oscillations and Waves in Radio Source of Drifting Pulsation Structures

    NASA Astrophysics Data System (ADS)

    Karlický, Marian; Rybák, Ján; Bárta, Miroslav

    2018-04-01

    Drifting pulsation structures (DPSs) are considered to be radio signatures of the plasmoids formed during magnetic reconnection in the impulsive phase of solar flares. In the present paper we analyze oscillations and waves in seven examples of drifting pulsation structures, observed by the 800 - 2000 MHz Ondřejov Radiospectrograph. For their analysis we use a new type of oscillation maps, which give us much more information as regards processes in DPSs than that in previous analyses. Based on these oscillation maps, made from radio spectra by the wavelet technique, we recognized quasi-periodic oscillations with periods ranging from about 1 to 108 s in all studied DPSs. This strongly supports the idea that DPSs are generated during a fragmented magnetic reconnection. Phases of most the oscillations in DPSs, especially for the period around 1 s, are synchronized ("infinite" frequency drift) in the whole frequency range of DPSs. For longer periods in some DPSs we found that the phases of the oscillations drift with the frequency drift in the interval from -17 to +287 MHz s^{-1}. We propose that these drifting phases can be caused (a) by the fast or slow magnetosonic waves generated during the magnetic reconnection and propagating through the plasmoid, (b) by a quasi-periodic structure in the plasma inflowing to the reconnection forming a plasmoid, and (c) by a quasi-periodically varying reconnection rate in the X-point of the reconnection close to the plasmoid.

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    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

  20. Three-wave mixing in conjugated polymer solutions: Two-photon absorption in polydiacetylenes

    NASA Astrophysics Data System (ADS)

    Chance, R. R.; Shand, M. L.; Hogg, C.; Silbey, R.

    1980-10-01

    Three-wave-mixing spectroscopy is used to determine the dispersive and absorptive parts of a strongly allowed two-photon transition in a series of polydiacetylene solutions. The data analysis yields the energy, width, symmetry assignment, and oscillator strength for the two-photon transition. The data conclusively demonstrate that strong two-photon absorption is a fundamental property of the polydiacetylene backbone. The remarkably large two-photon absorption coefficients are explained by large oscillator strengths for both transitions involved in the two-photon absorption combined with strong one-photon resonance effects. The experimental results are shown to be consistent with a simple theoretical model for the energies and oscillator strengths of the one- and two-photon-allowed transitions.

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

    DTIC Science & Technology

    1982-09-01

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

  2. Magellan radio occultation measurements of atmospheric waves on Venus

    NASA Technical Reports Server (NTRS)

    Hinson, David P.; Jenkins, J. M.

    1995-01-01

    Radio occultation experiments were conducted at Venus on three consecutive orbits of the Magellan spacecraft in October 1991. Each occultation occurred over the same topography (67 deg N, 127 deg E) and at the same local time (22 hr 5 min), but the data are sensitive to zonal variations because the atmosphere rotates significantly during one orbit. Through comparisons between observations and predictions of standard wave theory, we have demonstrated that small-scale oscillations in retrieved temperature profiles as well as scintillations in received signal intensity are caused by a spectrum of vertically propagating internal gravity waves. There is a strong similarity between the intensity scintillations observed here and previous measurements, which pertain to a wide range of locations and experiment dates. This implies that the same basic phenomenon underlies all the observations and hence that gravity waves are a persistent, global feature of Venus' atmosphere. We obtained a fairly complete characterization of a gravity wave that appears above the middle cloud in temperature measurements on all three orbits. The amplitude and vertical wavelength are about 4 K and 2.5 km respectively, at 65 km. A model for radiative damping implies that the wave intrinsic frequency is approximately 2 x 10(exp 4) rad/sec, the corresponding ratio between horizontal and vertical wavelengths is approximately 100. The wave is nearly stationary relative to the surface or the Sun. Radiative attenuation limits the wave amplitude at altitudes above approximately 65 km, leading to wave drag on the mean zonal winds of about +0.4 m/sec per day (eastward). The sign, magnitude, and location of this forcing suggest a possible role in explaining the decrease with height in the zonal wind speed that is believed to occur above the cloud tops. Temperature oscillations with larger vertical wavelengths (5-10 km) were also observed on all three orbits, but we are able unable to interpret these

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

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

    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

  4. Stable high absorption metamaterial for wide-angle incidence of terahertz wave

    NASA Astrophysics Data System (ADS)

    Du, Qiujiao; Zeng, Zuoxun; Xiang, Dong; Lv, Tao; Zhang, Guangyong; Yang, Hongwu

    2014-04-01

    We propose a metamaterial based on metallic Jerusalem cross and cross-wire structures for realizing relatively stable high absorption with respect to the wide angle incidence of both polarized terahertz (THz) waves. Numerical simulations are carried out to verify the proposed absorber. For both transverse electric and transverse magnetic polarizations, absorptions around 0.93 THz reach nearly up to unity under normal incidence and maintain above 97% over a wide incidence angle range. The THz absorber can be easily micro-fabricated due to a thickness about 40 times smaller than operating wavelength. The proposed metamaterial is a promising candidate as absorbing element in THz thermal imager, due to its wide angle, stable high absorption and very thin thickness.

  5. Wide-aperture total absorption of a terahertz wave in a nanoperiodic graphene-based plasmon structure

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

    Polischuk, O. V., E-mail: polischuk.sfire@mail.ru; Melnikova, V. S.; Popov, V. V., E-mail: popov-slava@yahoo.co.uk

    2016-11-15

    The terahertz absorption spectrum in a periodic array of graphene nanoribbons located on the surface of a dielectric substrate with a high refractive index (terahertz prism) is studied theoretically. The total absorption of terahertz radiation is shown to occur in the regime of total internal reflection of the terahertz wave from the periodic array of graphene nanoribbons, at the frequencies of plasma oscillations in graphene, in a wide range of incidence angles of the external terahertz wave even at room temperature.

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

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

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

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

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

    ERIC Educational Resources Information Center

    Hare, Jonathan

    2010-01-01

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

  10. Spiky Fine Structure of Type III-like Radio Bursts in Absorption

    NASA Astrophysics Data System (ADS)

    Chernov, G. P.; Yan, Y. H.; Tan, C. M.; Chen, B.; Fu, Q. J.

    2010-03-01

    An uncommon fine structure in the radio spectrum consisting of bursts in absorption was observed with the Chinese Solar Broadband Radiospectrometer (SBRS) in the frequency range of 2.6 - 3.8 GHz during an X3.4/4B flare on 13 December 2006 in active region NOAA 10930 (S05W33). Usual fine structures in emission such as spikes, zebra stripes, and drifting fibers were observed at the peak of every new flare brightening. Within an hour at the decay phase of the event we observed bursts consisting of spikes in absorption, which pulsated periodically in frequency. Their instantaneous frequency bandwidths were found to be in the 75 MHz range. Moreover, in the strongest Type III-like bursts in absorption, the spikes showed stripes of the zebra-pattern (ZP) that drifted to higher frequencies. All spikes had the duration as short as down to the limit of the instrument resolution of ≈8 ms. The TRACE 195 Å images indicate that the magnetic reconnection at this moment occurred in the western edge of the flare loop arcade. Taking into account the presence of the reverse-drifting bursts in emission, in the course of the restoration of the magnetic structures in the corona, the acceleration of the beams of fast particles must have occurred both upward and downward at different heights. The upward beams will be captured by the magnetic trap, where the loss-cone distribution of fast particles (responsible for the emission of continuum and ZP) were formed. An additional injection of fast particles will fill the loss-cone later, breaking the loss-cone distribution. Therefore, the generation of continuum will be quenched at these moments, which was evidenced by the formation of bursts in absorption.

  11. The Sun Radio Imaging Space Experiment (SunRISE) Mission

    NASA Astrophysics Data System (ADS)

    Lazio, Joseph; Kasper, Justin; Maksimovic, Milan; Alibay, Farah; Amiri, Nikta; Bastian, Tim; Cohen, Christina; Landi, Enrico; Manchester, Ward; Reinard, Alysha; Schwadron, Nathan; Cecconi, Baptiste; Hallinan, Gregg; Hegedus, Alex; Krupar, Vratislav; Zaslavsky, Arnaud

    2017-04-01

    Radio emission from coronal mass ejections (CMEs) is a direct tracer of particle acceleration in the inner heliosphere and potential magnetic connections from the lower solar corona to the larger heliosphere. Energized electrons excite Langmuir waves, which then convert into intense radio emission at the local plasma frequency, with the most intense acceleration thought to occur within 20 RS. The radio emission from CMEs is quite strong such that only a relatively small number of antennas is required to detect and map it, but many aspects of this particle acceleration and transport remain poorly constrained. Ground-based arrays would be quite capable of tracking the radio emission associated with CMEs, but absorption by the Earth's ionosphere limits the frequency coverage of ground-based arrays (ν ≳ 15 MHz), which in turn limits the range of solar distances over which they can track the radio emission (≲ 3RS). The state-of-the-art for tracking such emission from space is defined by single antennas (Wind/WAVES, Stereo/SWAVES), in which the tracking is accomplished by assuming a frequency-to-density mapping; there has been some success in triangulating the emission between the spacecraft, but considerable uncertainties remain. We describe the Sun Radio Imaging Space Experiment (SunRISE) mission concept: A constellation of small spacecraft in a geostationary graveyard orbit designed to localize and track radio emissions in the inner heliosphere. Each spacecraft would carry a receiving system for observations below 25 MHz, and SunRISE would produce the first images of CMEs more than a few solar radii from the Sun. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

  12. The Sun Radio Imaging Space Experiment (SunRISE) Mission

    NASA Astrophysics Data System (ADS)

    Kasper, J. C.; Lazio, J.; Alibay, F.; Amiri, N.; Bastian, T.; Cohen, C.; Landi, E.; Hegedus, A. M.; Maksimovic, M.; Manchester, W.; Reinard, A.; Schwadron, N.; Cecconi, B.; Hallinan, G.; Krupar, V.

    2017-12-01

    Radio emission from coronal mass ejections (CMEs) is a direct tracer of particle acceleration in the inner heliosphere and potential magnetic connections from the lower solar corona to the larger heliosphere. Energized electrons excite Langmuir waves, which then convert into intense radio emission at the local plasma frequency, with the most intense acceleration thought to occur within 20 R_S. The radio emission from CMEs is quite strong such that only a relatively small number of antennas is required to detect and map it, but many aspects of this particle acceleration and transport remain poorly constrained. Ground-based arrays would be quite capable of tracking the radio emission associated with CMEs, but absorption by the Earth's ionosphere limits the frequency coverage of ground-based arrays (nu > 15 MHz), which in turn limits the range of solar distances over which they can track the radio emission (< 3 R_S). The state-of-the-art for tracking such emission from space is defined by single antennas (Wind/WAVES, Stereo/SWAVES), in which the tracking is accomplished by assuming a frequency-to-density mapping; there has been some success in triangulating the emission between the spacecraft, but considerable uncertainties remain. We describe the Sun Radio Imaging Space Experiment (SunRISE) mission concept: A constellation of small spacecraft in a geostationary graveyard orbit designed to localize and track radio emissions in the inner heliosphere. Each spacecraft would carry a receiving system for observations below 25 MHz, and SunRISE would produce the first images of CMEs more than a few solar radii from the Sun. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

  13. Surface wave energy absorption by a partially submerged bio-inspired canopy.

    PubMed

    Nové-Josserand, C; Castro Hebrero, F; Petit, L-M; Megill, W M; Godoy-Diana, R; Thiria, B

    2018-03-27

    Aquatic plants are known to protect coastlines and riverbeds from erosion by damping waves and fluid flow. These flexible structures absorb the fluid-borne energy of an incoming fluid by deforming mechanically. In this paper we focus on the mechanisms involved in these fluid-elasticity interactions, as an efficient energy harvesting system, using an experimental canopy model in a wave tank. We study an array of partially-submerged flexible structures that are subjected to the action of a surface wave field, investigating in particular the role of spacing between the elements of the array on the ability of our system to absorb energy from the flow. The energy absorption potential of the canopy model is examined using global wave height measurements for the wave field and local measurements of the elastic energy based on the kinematics of each element of the canopy. We study different canopy arrays and show in particular that flexibility improves wave damping by around 40%, for which half is potentially harvestable.

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

    NASA Astrophysics Data System (ADS)

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

    2017-12-01

    Breakdown of the neutral atmosphere at ionospheric altitudes can be achieved with high power HF waves that reflect on the bottomside of the ionosphere. For overdense heating (i.e., wave frequency < maximum plasma frequency in the F-layer), the largest electric fields in the plasma are found just below the reflection altitude. There, electromagnetic waves are converted into electron plasma (Langmir) waves and ion acoustic waves. These waves are measured by scattering of the 430 MHz radar at Arecibo to from an enhanced plasma line. The photo-electron excitation of Langmuir waves yields a weaker plasma-line profile that shows the complete electron profile with the radar. Once HF enhanced Langmuir waves are formed, they can accelerate the photo-electron population to sufficient energies for neutral breakdown and enhanced ionization inside the HF Radio Beam. Plasma pancakes are produced because the breakdown process continues to build up plasma on bottom of the breakdown clouds and recombination occurs on the older breakdown plasma at the top of these clouds. Thus, the plasma pancake falls with altitude from the initial HF wave reflection altitude near 250 km to about 160 km where ion-electron recombination prevents the plasma cloud from being sustained by the high power HF. Experiments in March 2017 have produced plasma pancakes with about 100 Mega-Watts effective radiated power 5.1 MHz with the Arecibo HF Facility. Observations using the 430 MHz radar show falling plasma pancakes that disappear at low altitudes and reform at the F-layer critical reflection altitude. Sometimes the periodic and regular falling motion of the plasma pancakes is influenced by Acoustic Gravity Waves (AGW) propagating through the modified HF region. A rising AGW can cause the plasma pancake to reside at nearly constant altitude for 10 to 20 minutes. Dense cavities are also produced by high power radio waves interacting with the F-Layer. These structures are observed with the Arecibo 430 MHz

  15. Whistlers, helicons, and lower hybrid waves: The physics of radio frequency wave propagation and absorption for current drive via Landau damping

    DOE PAGES

    Pinsker, Robert I.

    2015-09-24

    This introductory-level tutorial article describes the application of plasma waves in the lower hybrid range of frequencies for current drive in tokamaks. Wave damping mechanisms in a nearly collisionless hot magnetized plasma are briefly described, and the connections between the properties of the damping mechanisms and the optimal choices of wave properties (mode, frequency, wavelength) are explored. The two wave modes available for current drive in the lower hybrid range of frequencies (LHRF) are described and compared. The terms applied to these waves in different applications of plasma physics are elucidated. Here, the character of the ray paths of thesemore » waves in the LHRF is illustrated in slab and toroidal geometries. An upcoming experiment on one of these two wave modes, the “helicon” or “whistler”, to be carried out on the DIII-D tokamak, is described.« less

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

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

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

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

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

    PubMed

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

    2010-06-18

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

  18. Advanced Sine Wave Modulation of Continuous Wave Laser System for Atmospheric CO2 Differential Absorption Measurements

    NASA Technical Reports Server (NTRS)

    Campbell, Joel F.; Lin, Bing; Nehrir, Amin R.

    2014-01-01

    NASA Langley Research Center in collaboration with ITT Exelis have been experimenting with Continuous Wave (CW) laser absorption spectrometer (LAS) as a means of performing atmospheric CO2 column measurements from space to support the Active Sensing of CO2 Emissions over Nights, Days, and Seasons (ASCENDS) mission.Because range resolving Intensity Modulated (IM) CW lidar techniques presented here rely on matched filter correlations, autocorrelation properties without side lobes or other artifacts are highly desirable since the autocorrelation function is critical for the measurements of lidar return powers, laser path lengths, and CO2 column amounts. In this paper modulation techniques are investigated that improve autocorrelation properties. The modulation techniques investigated in this paper include sine waves modulated by maximum length (ML) sequences in various hardware configurations. A CW lidar system using sine waves modulated by ML pseudo random noise codes is described, which uses a time shifting approach to separate channels and make multiple, simultaneous online/offline differential absorption measurements. Unlike the pure ML sequence, this technique is useful in hardware that is band pass filtered as the IM sine wave carrier shifts the main power band. Both amplitude and Phase Shift Keying (PSK) modulated IM carriers are investigated that exibit perfect autocorrelation properties down to one cycle per code bit. In addition, a method is presented to bandwidth limit the ML sequence based on a Gaussian filter implemented in terms of Jacobi theta functions that does not seriously degrade the resolution or introduce side lobes as a means of reducing aliasing and IM carrier bandwidth.

  19. Waves in the Martian Atmosphere: Results from MGS Radio Occultations

    NASA Technical Reports Server (NTRS)

    Flasar, F. M.; Hinson, D. P.; Tyler, G. L.

    1999-01-01

    Temperatures retrieved from Mars Global Surveyor radio occultations have been searched for evidence of waves. Emphasis has been on the initial series of occultations between 29 deg N and 64 deg S, obtained during the early martian southern summer, L(sub s) = 264 deg - 308 deg. The profiles exhibit an undulatory behavior that is suggestive of vertically propagating waves. wavelengths approximately 10 km are often dominant, but structure on smaller scales is evident. The undulatory structure is most pronounced between latitudes 29 deg N and 10 deg S, usually in regions of "interesting" topography, e.g., in the Tharsis region and near the edge of Syrtis Major. Several temperature profiles, particularly within 30 deg of the equator, exhibit lapse rates that locally become superadiabatic near the 0.4-mbar level or at higher altitudes. This implies that the waves are "breaking" and depositing horizontal momentum into the atmosphere. Such a deposition may play an important role in modulating the atmospheric winds, and characterizing the spatial and temporal distribution of these momentum transfers can provide important clues to understanding how the global circulation is maintained.

  20. Radio and Plasma Wave Observations During Cassini's Grand Finale

    NASA Astrophysics Data System (ADS)

    Kurth, W. S.; Bostrom, R.; Canu, P.; Cecconi, B.; Cornilleau-Wehrlin, N.; Farrell, W. M.; Fischer, G.; Galopeau, P. H. M.; Gurnett, D. A.; Gustafsson, G.; Hospodarsky, G. B.; Lamy, L.; Lecacheux, A.; Louarn, P.; MacDowall, R. J.; Menietti, J. D.; Modolo, R.; Morooka, M.; Pedersen, A.; Persoon, A. M.; Sulaiman, A. H.; Wahlund, J. E.; Ye, S.; Zarka, P. M.

    2017-12-01

    Cassini ends its 13-year exploration of the Saturnian system in 22 high inclination Grand Finale orbits with perikrones falling between the inner edge of the D ring and the upper limits of Saturn's atmosphere. The Cassini Radio and Plasma Wave Science (RPWS) instrument makes a variety of observations in these unique orbits including Saturn kilometric radiation, plasma waves such as auroral hiss associated with Saturn's auroras, dust via impacts with Cassini, and the upper reaches of Saturn's ionosphere. This paper will provide an overview of the RPWS results from this final phase of the Cassini mission with the unique opportunities afforded by the orbit. Based on early Grand Finale orbits, we can already say that the spacecraft has passed through cyclotron maser source regions of the Saturn kilometric radiation a number of times, found only small amounts of micron-sized dust in the equatorial region, and observed highly variable densities of cold plasma of order 1000 cm-3 in the ionosphere at altitudes of a few thousand km.

  1. Ion absorption of the high harmonic fast wave in the National Spherical Torus Experiment

    NASA Astrophysics Data System (ADS)

    Rosenberg, Adam Lewis

    Ion absorption of the high harmonic fast wave in a spherical torus is of critical importance to assessing the viability of the wave as a means of heating and driving current. Analysis of recent NSTX shots has revealed that under some conditions when neutral beam and RF power are injected into the plasma simultaneously, a fast ion population with energy above the beam injection energy is sustained by the wave. In agreement with modeling, these experiments find the RF-induced fast ion tail strength and neutron rate at lower B-fields to be less enhanced, likely due to a larger β profile, which promotes greater off-axis absorption where the fast ion population is small. Ion loss codes find the increased loss fraction with decreased B insufficient to account for the changes in tail strength, providing further evidence that this is an RF interaction effect. Though greater ion absorption is predicted with lower k∥, surprisingly little variation in the tail was observed, along with a neutron rate enhancement with higher k∥. Data from the neutral particle analyzer, neutron detectors, x-ray crystal spectrometer, and Thomson scattering is presented, along with results from the TRANSP transport analysis code, ray-tracing codes HPRT and CURRAY, full-wave code and AORSA, quasilinear code CQL3D, and ion loss codes EIGOL and CONBEAM.

  2. Quasi-periodic Radio Bursts Associated with Fast-mode Waves near a Magnetic Null Point

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

    Kumar, Pankaj; Nakariakov, Valery M.; Cho, Kyung-Suk, E-mail: pankaj.kumar@nasa.gov

    This paper presents an observation of quasi-periodic rapidly propagating waves observed in the Atmospheric Image Assembly (AIA) 171/193 Å channels during the impulsive phase of an M1.9 flare that occurred on 2012 May 7. The instant period was found to decrease from 240 to 120 s, and the speed of the wavefronts was in the range of ∼664–1416 km s{sup −1}. Almost simultaneously, quasi-periodic bursts with similar instant periods, ∼70 and ∼140 s, occur in the microwave emission and in decimetric type IV and type III radio bursts, and in the soft X-ray emission. The magnetic field configuration of themore » flare site was consistent with a breakout topology, i.e., a quadrupolar field along with a magnetic null point. The quasi-periodic rapidly propagating wavefronts of the EUV emission are interpreted as a fast magnetoacoustic wave train. The observations suggest that the fast-mode waves are generated during the quasi-periodic magnetic reconnection in the cusp region above the flare arcade loops. For the first time, we provide evidence of a tadpole wavelet signature at about 70–140 s in decimetric (245/610 MHz) radio bursts, along with the direct observation of a coronal fast-mode wave train in EUV. In addition, at AIA 131/193 Å we observed quasi-periodic EUV disturbances with periods of 95 and 240 s propagating downward at apparent speeds of 172–273 km s{sup −1}. The nature of these downward propagating disturbances is not revealed, but they could be connected to magnetoacoustic waves or periodically shrinking loops.« less

  3. Evidence for ultra-fast outflows in radio-quiet AGNs. I. Detection and statistical incidence of Fe K-shell absorption lines

    NASA Astrophysics Data System (ADS)

    Tombesi, F.; Cappi, M.; Reeves, J. N.; Palumbo, G. G. C.; Yaqoob, T.; Braito, V.; Dadina, M.

    2010-10-01

    Context. Blue-shifted Fe K absorption lines have been detected in recent years between 7 and 10 keV in the X-ray spectra of several radio-quiet AGNs. The derived blue-shifted velocities of the lines can often reach mildly relativistic values, up to 0.2-0.4c. These findings are important because they suggest the presence of a previously unknown massive and highly ionized absorbing material outflowing from their nuclei, possibly connected with accretion disk winds/outflows. Aims: The scope of the present work is to statistically quantify the parameters and incidence of the blue-shifted Fe K absorption lines through a uniform analysis on a large sample of radio-quiet AGNs. This allows us to assess their global detection significance and to overcome any possible publication bias. Methods: We performed a blind search for narrow absorption features at energies greater than 6.4 keV in a sample of 42 radio-quiet AGNs observed with XMM-Newton. A simple uniform model composed by an absorbed power-law plus Gaussian emission and absorption lines provided a good fit for all the data sets. We derived the absorption lines parameters and calculated their detailed detection significance making use of the classical F-test and extensive Monte Carlo simulations. Results: We detect 36 narrow absorption lines on a total of 101 XMM-Newton EPIC pn observations. The number of absorption lines at rest-frame energies higher than 7 keV is 22. Their global probability to be generated by random fluctuations is very low, less than 3 × 10-8, and their detection have been independently confirmed by a spectral analysis of the MOS data, with associated random probability <10-7. We identify the lines as Fe XXV and Fe XXVI K-shell resonant absorption. They are systematically blue-shifted, with a velocity distribution ranging from zero up to ~0.3c, with a peak and mean value at ~0.1c. We detect variability of the lines on both EWs and blue-shifted velocities among different XMM-Newton observations

  4. Enhanced absorption of TM waves in conductive nanoparticles structure

    NASA Astrophysics Data System (ADS)

    Mousa, H. M.; Shabat, M. M.; Ouda, A. K.; Schaadt, D. M.

    2018-05-01

    This paper tackles anti-reflection coating structure for silicon solar cell where conductive nanoparticle (CNP) film is sandwiched between a semi-infinite glass cover and a semi-infinite silicon substrate. The transmission and reflection coefficients are derived by the transfer matrix method and simulated for values of unit cell sizes, gab widths in visible and near-infrared radiation. We also illustrated the dependence of the absorption, transmission and reflection coefficients on several angles of incidence of the transverse magnetic polarized (TM) waves. We found out that reflection decreases by the increase of incident angle to 50∘. If nanoparticles are suitably located and sized at gab width of 3.5 nm, unit cell of 250 nm and CNP layer thickness of 150 nm, the absorptivity of the structure achieves 100%.

  5. Electromagnetic Wave Absorption Property of Graphene with FeO4 Nanoparticles.

    PubMed

    Yang, Cheng; Dai, Shenglong; Zhang, Xiaoyan; Zhao, Tianyu; Yan, Shaojiu; Zhao, Xiuying

    2016-02-01

    Nanomaterials consisting of various ratios of Fe3O4 and graphene (defined C-Fe3O4/GR) were pre- pared by an in situ coordination complex hydro-thermal synthesis method. The structure and morphology of the nanomaterials C-Fe3O4/GR obtained were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and transmission electron microscopy (TEM). It was found that the Fe3O4 nanoparticles distributed on the surfaces of graphene, and had a spinel structure and a uniform chemical phase when the weight ratios of Fe3O4 to graphene oxide (GO) were 9:1 or 9:2. It was suggested that GO had been successfully reduced to graphene and the Fe3O4 nanoparticles were chemically bonded to graphene. The SQUID vibrating sample magnetometer (SQUID-VSM) indicated that the maximum of the saturation magnetization was 83.6 emmicro g(-1) when the mass ratio of Fe3O4 to GO was 9:2. Electromagnetic wave absorption showed that the chemical compound of Fe3O4 and graphene had a better electromagnetic property than the mechanical blend of Fe3O4 and graphene (M-Fe3O4/GR). The C-Fe3O4/GR had a reflection loss larger than -10 dB in the frequency range 12.9-17.0 GHz for an absorber thickness of 3 mm, and a maximum reflection loss of -12.3 dB at 14.8 GHz and a maximum reflection loss of -31.2 dB at 10.5 GHz for an absorber thickness of 10 mm. Theoretical analysis showed that the electromagnetic wave absorption behavior obeyed the quarter-wave principles. These results showed that the C-Fe3O4/GR nanomaterials can meet the requirements for some engineering applications, showing great application potential in electromagnetic wave absorption.

  6. VLF Radio Wave Propagation Across the Day/Night Terminator

    NASA Astrophysics Data System (ADS)

    Burch, H.; Moore, R. C.

    2016-12-01

    In May 2016, a new array of VLF radio receivers was deployed spanning the East Coast of the United States. We present preliminary observations from the array, which was designed in part to track the propagation of the narrowband VLF transmitter signal, NAA (24.0 kHz), down the coast from Cutler, Maine. Amplitude, phase, and polarization observations are compared over multiple days and at different times of year to investigate the dependence of VLF propagation characteristics on solar zenith angle. Measurements are compared to simulations using the Long Wave Propagation Capability code (LWPC) in order to evaluate the accuracy of LWPC's built-in ionosphere model. Efforts to improve the ionosphere model based on observations are discussed.

  7. The mm-wave compact component of AGN

    NASA Astrophysics Data System (ADS)

    Behar, Ehud; Vogel, Stuart; Baldi, Ranieri D.; Smith, Krista L.; Mushotzky, Richard F.

    2018-05-01

    mm-wave emission from Active Galactic Nuclei (AGN) may hold the key to understanding the physical origin of their radio cores. The correlation between radio/mm and X-ray luminosity may suggest a similar physical origin of the two sources. Since synchrotron self absorption decreases with frequency, mm-waves probe smaller length scales than cm-waves. We report on 100 GHz (3 mm) observations with CARMA of 26 AGNs selected from the hard X-ray Swift/BAT survey. 20/26 targets were detected at 100 GHz down to the 1 mJy (3σ) sensitivity, which corresponds to optically thick synchrotron source sizes of 10-4 - 10-3 pc. Most sources show a 100 GHz flux excess with respect to the spectral slope extrapolated from low frequencies. This mm spectral component likely originates from smaller scales than the few-GHz emission. The measured mm sources lie roughly around the Lmm (100 GHz) ˜10-4LX (2-10 keV) relation, similar to a few previously published X-ray selected sources, and hinting perhaps at a common coronal origin.

  8. Studies on absorption of EC waves in assisted startup experiment on FTU

    NASA Astrophysics Data System (ADS)

    Granucci, G.; Ricci, D.; Farina, D.; Figini, L.; Iraji, D.; Tudisco, O.; Ramponi, G.; Bin, W.

    2012-09-01

    Assistance of EC wave for plasma breakdown and current ramp up is the proposed scenario for the ITER case, characterized by low toroidal electric field. The experimental results on many tokamaks clearly indicate the capabilities of the proposed scheme to have a robust breakdown in ITER. The key aspect of this technique is the EC power required, strongly related to the absorption of the wave in the initial stage of plasma formation. This aspect is generally neglected due to the diagnostics difficulties in the plasma formation phase. As a consequence a multi-pass absorption scheme is usually considered reasonable, leading to a strong absorption after many reflections on the walls. The present study exploits the high temporal and spatial resolution of the fast scanning interferometer of FTU together with the measure of residual power obtained by a sniffer probe. The absorbed EC power is calculated considering also the polarization rotation and the subsequent mode conversion after incidence on the internal wall and compared with that derived from experimental data. The resulting EC power distribution can explain differences observed between perpendicular and oblique injection results, indicating future investigations to define ITER power requirements.

  9. Investigation on the energy absorption performance of a fixed-bottom pressure-differential wave energy converter

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

    Babarit, A.; Wendt, F.; Yu, Y. -H.

    2017-04-01

    In this article, we investigate the energy absorption performance of a fixed-bottom pressure-differential wave energy converter. Two versions of the technology are considered: one has the moving surfaces on the bottom of the air chambers whereas the other has the moving surfaces on the top. We developed numerical models in the frequency domain, thereby enabling the power absorption of the two versions of the device to be assessed. It is observed that the moving surfaces on the top allow for easier tuning of the natural period of the system. Taking into account stroke limitations, the design is optimized. Results indicatemore » that the pressure-differential wave energy converter is a highly efficient technology both with respect to energy absorption and selected economic performance indicators.« less

  10. Imaging spectroscopy of solar radio burst fine structures.

    PubMed

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

    2017-11-15

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

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

    NASA Technical Reports Server (NTRS)

    Ho, Christian; Golshan, Nasser

    1999-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2018-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  14. Resonant behaviour of MHD waves on magnetic flux tubes. I - Connection formulae at the resonant surfaces. II - Absorption of sound waves by sunspots

    NASA Technical Reports Server (NTRS)

    Sakurai, Takashi; Goossens, Marcel; Hollweg, Joseph V.

    1991-01-01

    The present method of addressing the resonance problems that emerge in such MHD phenomena as the resonant absorption of waves at the Alfven resonance point avoids solving the fourth-order differential equation of dissipative MHD by recourse to connection formulae across the dissipation layer. In the second part of this investigation, the absorption of solar 5-min oscillations by sunspots is interpreted as the resonant absorption of sounds by a magnetic cylinder. The absorption coefficient is interpreted (1) analytically, under certain simplifying assumptions, and numerically, under more general conditions. The observed absorption coefficient magnitude is explained over suitable parameter ranges.

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

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

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

  16. First tsunami gravity wave detection in ionospheric radio occultation data

    DOE PAGES

    Coïsson, Pierdavide; Lognonné, Philippe; Walwer, Damian; ...

    2015-05-09

    After the 11 March 2011 earthquake and tsunami off the coast of Tohoku, the ionospheric signature of the displacements induced in the overlying atmosphere has been observed by ground stations in various regions of the Pacific Ocean. We analyze here the data of radio occultation satellites, detecting the tsunami-driven gravity wave for the first time using a fully space-based ionospheric observation system. One satellite of the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) recorded an occultation in the region above the tsunami 2.5 h after the earthquake. The ionosphere was sounded from top to bottom, thus providing themore » vertical structure of the gravity wave excited by the tsunami propagation, observed as oscillations of the ionospheric Total Electron Content (TEC). The observed vertical wavelength was about 50 km, with maximum amplitude exceeding 1 total electron content unit when the occultation reached 200 km height. We compared the observations with synthetic data obtained by summation of the tsunami-coupled gravity normal modes of the Earth/Ocean/atmosphere system, which models the associated motion of the ionosphere plasma. These results provide experimental constraints on the attenuation of the gravity wave with altitude due to atmosphere viscosity, improving the understanding of the propagation of tsunami-driven gravity waves in the upper atmosphere. They demonstrate that the amplitude of the tsunami can be estimated to within 20% by the recorded ionospheric data.« less

  17. The mm-wave compact component of an AGN

    NASA Astrophysics Data System (ADS)

    Behar, Ehud; Vogel, Stuart; Baldi, Ranieri D.; Smith, Krista L.; Mushotzky, Richard F.

    2018-07-01

    mm-wave emission from active galactic nuclei (AGNs) may hold the key to understanding the physical origin of their radio cores. The correlation between radio/mm and X-ray luminosity may suggest a similar physical origin of the two sources. Since synchrotron self-absorption decreases with frequency, mm-waves probe smaller length-scales than cm-waves. We report on 100 GHz (3 mm) observations with the Combined Array for Research in Millimeter-wave Astronomy of 26 AGNs selected from the hard X-ray Swift/Burst Alert Telescope survey. 20/26 targets were detected at 100 GHz down to the 1 mJy (3σ) sensitivity, which corresponds to optically thick synchrotron source sizes of 10-4-10-3 pc. Most sources show a 100 GHz flux excess with respect to the spectral slope extrapolated from low frequencies. This mm spectral component likely originates from smaller scales than the few-GHz emission. The measured mm sources lie roughly around the Lmm (100 GHz) ˜10-4LX (2-10 keV) relation, similar to a few previously published X-ray selected sources, and hinting perhaps at a common coronal origin.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  19. Characteristics of absorption and frequency filtration of ULF electromagnetic waves in the ionosphere

    NASA Astrophysics Data System (ADS)

    Prikner, K.

    A statistical method for interpreting data from experimental investigations of vertically-propagating electromagnetic ULF waves in the inhomogeneous magnetoactive ionosphere is considered theoretically. Values are obtained for the transmission, reflection and absorption characteristics of ULF waves in a limited ionospheric layer, in order to describe the relation between the frequency of a wave generated at the earth surface and that of a total wave propagating above the ionospheric layer. This relation is used to express the frequency-selective amplitude filtration of ULF waves in the layer. The method is applied to a model of the night ionosphere of mid-geomagnetic latitudes in the form of a plate 1000 km thick. It is found that the relative characteristics of transmission and amplitude loss in the wave adequately describe the frequency selectiveness and wave filtration capacity of the ionosphere. The method is recommended for studies of the structural changes of wave parameters in ionospheric models.

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

  1. Scattering and absorption of massless scalar waves by Born-Infeld black holes

    NASA Astrophysics Data System (ADS)

    Sanchez, Pablo Alejandro; Bretón, Nora; Bergliaffa, Santiago Esteban Perez

    2018-06-01

    We present the results of a study of the scattering of massless planar scalar waves by a Born-Infeld black hole. The scattering and absorption cross sections are calculated using partial-wave methods. The numerical results are checked by reproducing those of the Reissner-Nordstrom black hole, and also using several approximations, with which our results are in very good agreement. The dependence of these phenomena on the effective potential, the charge of the black hole, and the value of the Born-Infeld parameter is discussed.

  2. Making Waves: Pirate Radio and Popular Music.

    ERIC Educational Resources Information Center

    Jones, Steve

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

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

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

    Miyamoto, Mayu; Imamura, Takeshi; Ando, Hiroki

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

  4. Low Frequency Radio-wave System for subsurface investigation

    NASA Astrophysics Data System (ADS)

    Soldovieri, Francesco; Gennarelli, Gianluca; Kudelya, Anatoliy; Denisov, Alexander

    2015-04-01

    Low frequency radio-wave methods (RWM) allow subsurface investigations in terms of lithological structure characterization, detection of filtration flows of ground water, anthropogenic and natural cavities. In this contribution, we present a RWM that exploits two coils working at frequencies of few MHz as transmitting and receiving antennas. The basic principle of this inductive method is as follows. The primary alternating electromagnetic field radiated by the transmitting coil induces eddy currents in the subsurface mainly due to the conductivity anomalies. These eddy currents generate a secondary (scattered) magnetic field which overlaps to the incident magnetic field and is detected by the receiving coil. Despite the simple operation of the system, the complexity of the electromagnetic scattering phenomenon at hand must be properly modeled to achieve adequate performance. Therefore, an advanced data processing technique, belonging to the class of the inverse scattering approaches, has been developed by the authors in a full 3D geometry. The proposed method allows to deal with data collected on a scanning surface under a dipole inductive profiling (DIP) modality, where the transmitting/receiving coils are moved simultaneously with fixed offset (multi-bistatic configuration). The hardware, called Dipole Inductive Radio-wave System (DIRS), is composed by an electronic unit and transmitting and receiving loop antennas radiating at frequencies of few MHz (2-4 MHz), which are installed on theodolite supports. The compactness of DIRS and its robustness to external electromagnetic interference offers the possibility to perform geophysical research up to the depth of some tens of meters and under several types of ground and water surfaces, vegetation, and weather conditions. The light weight and small size of system (the single antenna with support weights about 5 kg and has a diameter of 0.5m) allows two operators to perform geophysical research without disturbing the

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2018-01-01

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

  7. Resonant absorption and amplification of circularly-polarized waves in inhomogeneous chiral media.

    PubMed

    Kim, Seulong; Kim, Kihong

    2016-01-25

    It has been found that in the media where the dielectric permittivity ε or the magnetic permeability μ is near zero and in transition metamaterials where ε or μ changes from positive to negative values, there occur a strong absorption or amplification of the electromagnetic wave energy in the presence of an infinitesimally small damping or gain and a strong enhancement of the electromagnetic fields. We attribute these phenomena to the mode conversion of transverse electromagnetic waves into longitudinal plasma oscillations and its inverse process. In this paper, we study analogous phenomena occurring in chiral media theoretically using the invariant imbedding method. In uniform isotropic chiral media, right-circularly-polarized and left-circularly-polarized waves are the eigen-modes of propagation with different effective refractive indices n(+) and n(-), whereas in the chiral media with a nonuniform impedance variation, they are no longer the eigenmodes and are coupled to each other. We find that both in uniform chiral slabs where either n(+) or n(-) is near zero and in chiral transition metamaterials where n(+) or n(-) changes from positive to negative values, a strong absorption or amplification of circularly-polarized waves occurs in the presence of an infinitesimally small damping or gain. We present detailed calculations of the mode conversion coefficient, which measures the fraction of the electromagnetic wave energy absorbed into the medium, for various configurations of ε and μ with an emphasis on the influence of a nonuniform impedance. We propose possible applications of these phenomena to linear and nonlinear optical devices that react selectively to the helicity of the circular polarization.

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

    NASA Astrophysics Data System (ADS)

    Kirillovich, Ivan; Gubenko, Vladimir; Pavelyev, Alexander

    Internal gravity waves (IGWs) modulate the structure and circulation of the Earth’s atmosphere, producing quasi-periodic variations in the wind velocity, temperature and density. Similar effects are anticipated for the Venus and Mars since IGWs are a characteristic of stably stratified atmosphere. In this context, an original method for the determination of IGW parameters from a vertical temperature profile measurement in a planetary atmosphere has been developed [Gubenko et al., 2008, 2011, 2012]. This method does not require any additional information not contained in the profile and may be used for the analysis of profiles measured by various techniques. The criterion for the IGW identification has been formulated and argued. In the case when this criterion is satisfied, the analyzed temperature fluctuations can be considered as wave-induced. The method is based on the analysis of relative amplitudes of the wave field and on the linear IGW saturation theory in which these amplitudes are restricted by dynamical (shear) instability processes in the atmosphere. When the amplitude of an internal wave reaches the shear instability threshold, energy is assumed to be dissipated in such a way that the IGW amplitude is maintained at the instability threshold level as the wave propagates upwards. We have extended the developed technique [Gubenko et al., 2008] in order to reconstruct the complete set of wave characteristics including such important parameters as the wave kinetic and potential energy per unit mass and IGW fluxes of the energy and horizontal momentum [Gubenko et al., 2011]. We propose also an alternative method to estimate the relative amplitudes and to extract IGW parameters from an analysis of perturbations of the Brunt-Vaislala frequency squared [Gubenko et al., 2011]. An application of the developed method to the radio occultation (RO) temperature data has given the possibility to identify the IGWs in the Earth's, Martian and Venusian atmospheres and

  9. RADIOACTIVE IRON ABSORPTION BY GASTRO-INTESTINAL TRACT

    PubMed Central

    Hahn, P. F.; Bale, W. F.; Ross, J. F.; Balfour, W. M.; Whipple, G. H.

    1943-01-01

    Iron absorption is a function of the gastro-intestinal mucosal epithelium. The normal non-anemic dog absorbs little iron but chronic anemia due to blood loss brings about considerable absorption—perhaps 5 to 15 times normal. In general the same differences are observed in man (1). Sudden change from normal to severe anemia within 24 hours does not significantly increase iron absorption. As the days pass new hemoglobin is formed. The body iron stores are depleted and within 7 days iron absorption is active, even when the red cell hematocrit is rising. Anoxemia of 50 per cent normal oxygen concentration for 48 hours does not significantly enhance iron absorption. In this respect it resembles acute anemia. Ordinary doses of iron given 1 to 6 hours before radio-iron will cause some "mucosa block"—that is an intake of radio-iron less than anticipated. Many variables which modify peristalsis come into this reaction. Iron given by vein some days before the dose of radio-iron does not appear to inhibit iron absorption. Plasma radio-iron absorption curves vary greatly. The curves may show sharp peaks in 1 to 2 hours when the iron is given in an empty stomach but after 6 hours when the radio-iron is given with food. Duration time of curves also varies widely, the plasma iron returning to normal in 6 to 12 hours. Gastric, duodenal, or jejunal pouches all show very active absorption of iron. The plasma concentration peak may reach a maximum before the solution of iron is removed from the gastric pouch—another example of "mucosa block." Absorption and distribution of radio-iron in the body of growing pups give very suggestive experimental data. The spleen, heart, upper gastro-intestinal tract, marrow, and pancreas show more radio-iron than was expected. The term "physiological saturation" with iron may be applied to the gastro-intestinal mucosal epithelium and explain one phase of acceptance or refusal of ingested iron. Desaturation is a matter of days not hours, whereas

  10. Radio wave heating of the corona and electron precipitation during flares

    NASA Technical Reports Server (NTRS)

    Melrose, D. B.; Dulk, G. A.

    1982-01-01

    Electron-cyclotron masers, excited while energy release is occurring in a flaring magnetic loop, are likely to generate extremely intense radiation at decimeter wavelengths. The energy in the radiation can be comparable with that in the electrons associated with hard X-ray bursts, i.e., a significant fraction of the total energy in the flare. Essentially all of the radio energy is likely to be reabsorbed by gyroresonance absorption, either near the emitting region or at some distance away in neighboring loops. Enhanced diffusion of fast electrons caused by the maser can lead to precipitation at the maximum possible rate, and hence account for hard X-ray emission from the footpoints of the magnetic loops.

  11. Juno Detects a Ham Radio HI from Earth

    NASA Image and Video Library

    2013-12-10

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

  12. Microwave absorption properties of a wave-absorbing coating employing carbonyl-iron powder and carbon black

    NASA Astrophysics Data System (ADS)

    Liu, Lidong; Duan, Yuping; Ma, Lixin; Liu, Shunhua; Yu, Zhen

    2010-11-01

    To prevent serious electromagnetic interference, a single-layer wave-absorbing coating employing complex absorbents composed of carbonyl-iron powder (CIP) and carbon black (CB) with epoxy resin as matrix was prepared. The morphologies of CIP and CB were characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. The electromagnetic parameters of CIP and CB were measured in the frequency range of 2-18 GHz by transmission/reflection technology, and the electromagnetic loss mechanisms of the two particles were discussed, respectively. The microwave absorption properties of the coatings were investigated by measuring reflection loss (RL) using arch method. The effects of CIP ratio, CB content and thickness on the microwave absorption properties were discussed, respectively. The results showed that the higher thickness, CIP or CB content could make the absorption band shift towards the lower frequency range. Significantly, the wave-absorbing coating could be applied in different frequency ranges according to actual demand by controlling the content of CIP or CB in composites.

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

    NASA Astrophysics Data System (ADS)

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

    2017-07-01

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

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

    DTIC Science & Technology

    2016-09-01

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

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

    NASA Astrophysics Data System (ADS)

    Iezekiel, Stavros

    2013-01-01

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

  16. An ultra-small NiFe2O4 hollow particle/graphene hybrid: fabrication and electromagnetic wave absorption property.

    PubMed

    Yan, Feng; Guo, Dong; Zhang, Shen; Li, Chunyan; Zhu, Chunling; Zhang, Xitian; Chen, Yujin

    2018-02-08

    Herein, ultra-small NiFe 2 O 4 hollow particles, with the diameter and wall thickness of only 6 and 1.8 nm, respectively, were anchored on a graphene surface based on the nanoscale Kirkendall effect. The hybrid exhibits an excellent electromagnetic wave absorption property, comparable or superior to that of most reported absorbers. Our strategy may open a way to grow ultra-small hollow particles on graphene for applications in many fields such as eletromagnetic wave absorption and energy storage and conversion.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  18. Variability of Kelvin wave momentum flux from high-resolution radiosonde and radio occultation data

    NASA Astrophysics Data System (ADS)

    Sjoberg, J. P.; Zeng, Z.; Ho, S. P.; Birner, T.; Anthes, R. A.; Johnson, R. H.

    2017-12-01

    Direct measurement of momentum flux from Kelvin waves in the stratosphere remains challenging. Constraining this flux from observations is an important step towards constraining the flux from models. Here we present results from analyses using linear theory to estimate the Kelvin wave amplitudes and momentum fluxes from both high-resolution radiosondes and from radio occultation (RO) data. These radiosonde data are from a contiguous 11-year span of soundings performed at two Department of Energy Atmospheric Radiation Measurement sites, while the RO data span 14 years from multiple satellite missions. Daily time series of the flux from both sources are found to be in quantitative agreement with previous studies. Climatological analyses of these data reveal the expected seasonal cycle and variability associated with the quasi-biennial oscillation. Though both data sets provide measurements on distinct spatial and temporal scales, the estimated flux from each provides insight into separate but complimentary aspects of how the Kelvin waves affect the stratosphere. Namely, flux derived from radiosonde sites provide details on the regional Kelvin wave variability, while the flux from RO data are zonal mean estimates.

  19. Coherent curvature radiation and fast radio bursts

    NASA Astrophysics Data System (ADS)

    Ghisellini, Gabriele; Locatelli, Nicola

    2018-06-01

    Fast radio bursts are extragalactic radio transient events lasting a few milliseconds with a Jy flux at 1 GHz. We propose that these properties suggest a neutron star progenitor, and focus on coherent curvature radiation as the radiation mechanism. We study for which sets of parameters the emission can fulfil the observational constraints. Even if the emission is coherent, we find that self-absorption can limit the produced luminosities at low radio frequencies and that an efficient re-acceleration process is needed to balance the dramatic energy losses of the emitting particles. Self-absorption limits the luminosities at low radio frequency, while coherence favours steep optically thin spectra. Furthermore, the magnetic geometry must have a high degree of order to obtain coherent curvature emission. Particles emit photons along their velocity vectors, thereby greatly reducing the inverse Compton mechanism. In this case we predict that fast radio bursts emit most of their luminosities in the radio band and have no strong counterpart in any other frequency bands.

  20. Microwave Resonator Measurements of Atmospheric Absorption Coefficients: A Preliminary Design Study

    NASA Technical Reports Server (NTRS)

    Walter, Steven J.; Spilker, Thomas R.

    1995-01-01

    A preliminary design study examined the feasibility of using microwave resonator measurements to improve the accuracy of atmospheric absorption coefficients and refractivity between 18 and 35 GHz. Increased accuracies would improve the capability of water vapor radiometers to correct for radio signal delays caused by Earth's atmosphere. Calibration of delays incurred by radio signals traversing the atmosphere has applications to both deep space tracking and planetary radio science experiments. Currently, the Cassini gravity wave search requires 0.8-1.0% absorption coefficient accuracy. This study examined current atmospheric absorption models and estimated that current model accuracy ranges from 5% to 7%. The refractivity of water vapor is known to 1% accuracy, while the refractivity of many dry gases (oxygen, nitrogen, etc.) are known to better than 0.1%. Improvements to the current generation of models will require that both the functional form and absolute absorption of the water vapor spectrum be calibrated and validated. Several laboratory techniques for measuring atmospheric absorption and refractivity were investigated, including absorption cells, single and multimode rectangular cavity resonators, and Fabry-Perot resonators. Semi-confocal Fabry-Perot resonators were shown to provide the most cost-effective and accurate method of measuring atmospheric gas refractivity. The need for accurate environmental measurement and control was also addressed. A preliminary design for the environmental control and measurement system was developed to aid in identifying significant design issues. The analysis indicated that overall measurement accuracy will be limited by measurement errors and imprecise control of the gas sample's thermodynamic state, thermal expansion and vibration- induced deformation of the resonator structure, and electronic measurement error. The central problem is to identify systematic errors because random errors can be reduced by averaging

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

    NASA Astrophysics Data System (ADS)

    Kochetov, Andrey

    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

  2. MALS–NOT: Identifying Radio-bright Quasars for the MeerKAT Absorption Line Survey

    NASA Astrophysics Data System (ADS)

    Krogager, J.-K.; Gupta, N.; Noterdaeme, P.; Ranjan, A.; Fynbo, J. P. U.; Srianand, R.; Petitjean, P.; Combes, F.; Mahabal, A.

    2018-03-01

    We present a preparatory spectroscopic survey to identify radio-bright, high-redshift quasars for the MeerKAT Absorption Line Survey. The candidates have been selected on the basis of a single flux density limit at 1.4 GHz (>200 mJy), together with mid-infrared color criteria from the Wide-field Infrared Survey Explorer. Through spectroscopic observations using the Nordic Optical Telescope, we identify 72 quasars out of 99 candidates targeted. We measure the spectroscopic redshifts based on characteristic, broad emission lines present in the spectra. Of these 72 quasars, 64 and 48 objects are at sufficiently high redshift (z > 0.6 and z > 1.4) to be used for the L-band and UHF-band spectroscopic follow-up with the Square Kilometre Array precursor in South Africa: the MeerKAT.

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

    PubMed

    Tsujimura, Shinichi; Yamagishi, Hiroto; Sankai, Yoshiyuki

    2009-01-01

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

  4. Ionospheric Caustics in Solar Radio Observations

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  5. Radio Jove: Citizen Science for Jupiter Radio Astronomy

    NASA Astrophysics Data System (ADS)

    Higgins, C. A.; Thieman, J.; Reyes, F. J.; Typinski, D.; Flagg, R. F.; Greenman, W.; Brown, J.; Ashcraft, T.; Sky, J.; Cecconi, B.; Garcia, L. N.

    2016-12-01

    The Radio Jove Project (http://radiojove.gsfc.nasa.gov) has been operating as an educational activity for 18 years to introduce radio astronomy activities to students, teachers, and the general public. Participants may build a simple radio telescope kit, make scientific observations, and interact with radio observatories in real-time over the Internet. Recently some of our dedicated citizen science observers have upgraded their systems to better study radio emission from Jupiter and the Sun by adding dual-polarization spectrographs and wide-band antennas in the frequency range of 15-30 MHz. Some of these observations are being used in conjunction with professional telescopes such as the Long Wavelength Array (LWA), the Nancay Decametric Array, and the Ukrainian URAN2 Radio Telescope. In particular, there is an effort to support the Juno Mission radio waves instrument at Jupiter by using citizen science ground-based data for comparison and polarization verification. These data will be archived through a Virtual European Solar and Planetary Access (VESPA) archive (https://voparis-radiojove.obspm.fr/radiojove/welcome) for use by the amateur and professional radio science community. We overview the program and display recent observations that will be of interest to the science community.

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

    NASA Astrophysics Data System (ADS)

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

    2003-04-01

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

  7. Multi-hump potentials for efficient wave absorption in the numerical solution of the time-dependent Schrödinger equation

    NASA Astrophysics Data System (ADS)

    Silaev, A. A.; Romanov, A. A.; Vvedenskii, N. V.

    2018-03-01

    In the numerical solution of the time-dependent Schrödinger equation by grid methods, an important problem is the reflection and wrap-around of the wave packets at the grid boundaries. Non-optimal absorption of the wave function leads to possible large artifacts in the results of numerical simulations. We propose a new method for the construction of the complex absorbing potentials for wave suppression at the grid boundaries. The method is based on the use of the multi-hump imaginary potential which contains a sequence of smooth and symmetric humps whose widths and amplitudes are optimized for wave absorption in different spectral intervals. We show that this can ensure a high efficiency of absorption in a wide range of de Broglie wavelengths, which includes wavelengths comparable to the width of the absorbing layer. Therefore, this method can be used for high-precision simulations of various phenomena where strong spreading of the wave function takes place, including the phenomena accompanying the interaction of strong fields with atoms and molecules. The efficiency of the proposed method is demonstrated in the calculation of the spectrum of high-order harmonics generated during the interaction of hydrogen atoms with an intense infrared laser pulse.

  8. Non-contact radio frequency shielding and wave guiding by multi-folded transformation optics method

    PubMed Central

    Madni, Hamza Ahmad; Zheng, Bin; Yang, Yihao; Wang, Huaping; Zhang, Xianmin; Yin, Wenyan; Li, Erping; Chen, Hongsheng

    2016-01-01

    Compared with conventional radio frequency (RF) shielding methods in which the conductive coating material encloses the circuits design and the leakage problem occurs due to the gap in such conductive material, non-contact RF shielding at a distance is very promising but still impossible to achieve so far. In this paper, a multi-folded transformation optics method is proposed to design a non-contact device for RF shielding. This “open-shielded” device can shield any object at a distance from the electromagnetic waves at the operating frequency, while the object is still physically open to the outer space. Based on this, an open-carpet cloak is proposed and the functionality of the open-carpet cloak is demonstrated. Furthermore, we investigate a scheme of non-contact wave guiding to remotely control the propagation of surface waves over any obstacles. The flexibilities of such multi-folded transformation optics method demonstrate the powerfulness of the method in the design of novel remote devices with impressive new functionalities. PMID:27841358

  9. Parametric study of power absorption from electromagnetic waves by small ferrite spheres

    NASA Technical Reports Server (NTRS)

    Englert, Gerald W.

    1989-01-01

    Algebraic expressions in terms of elementary mathematical functions are derived for power absorption and dissipation by eddy currents and magnetic hysteresis in ferrite spheres. Skin depth is determined by using a variable inner radius in descriptive integral equations. Numerical results are presented for sphere diameters less than one wavelength. A generalized power absorption parameter for both eddy currents and hysteresis is expressed in terms of the independent parameters involving wave frequency, sphere radius, resistivity, and complex permeability. In general, the hysteresis phenomenon has a greater sensitivity to these independent parameters than do eddy currents over the ranges of independent parameters studied herein. Working curves are presented for obtaining power losses from input to the independent parameters.

  10. High intersubband absorption in long-wave quantum well infrared photodetector based on waveguide resonance

    NASA Astrophysics Data System (ADS)

    Zheng, Yuanliao; Chen, Pingping; Ding, Jiayi; Yang, Heming; Nie, Xiaofei; Zhou, Xiaohao; Chen, Xiaoshuang; Lu, Wei

    2018-06-01

    A hybrid structure consisting of periodic gold stripes and an overlaying gold film has been proposed as the optical coupler of a long-wave quantum well infrared photodetector. Absorption spectra and field distributions of the structure at back-side normal incidence are calculated by the finite difference time-domain method. The results indicate that the intersubband absorption can be greatly enhanced based on the waveguide resonance as well as the surface plasmon polariton (SPP) mode. With the optimized structural parameters of the periodic gold stripes, the maximal intersubband absorption can exceed 80%, which is much higher than the SPP-enhanced intersubband absorption (<50%) and about 6 times the one of the standard device. The relationship between the structural parameters and the waveguide resonant wavelength is derived. Other advantages of the efficient optical coupling based on waveguide resonance are also discussed.

  11. Hybridizing polypyrrole chains with laminated and two-dimensional Ti3C2Tx toward high-performance electromagnetic wave absorption

    NASA Astrophysics Data System (ADS)

    Tong, Yuan; He, Man; Zhou, Yuming; Zhong, Xi; Fan, Lidan; Huang, Tingyuan; Liao, Qiang; Wang, Yongjuan

    2018-03-01

    In this study, multilayer sandwich heterostructural Ti3C2Tx MXenes decorated with polypyrrole chains have been synthesized successfully via HF etching treatment and in-situ chemical oxidative polymerization approach. The hybrids were investigated as EM wave absorbers for the first time. It is found that the composites consisting of 25 wt% Ti3C2Tx/PPy hybrids in a paraffin matrix exhibit a minimum reflection loss of -49.2 dB (∼99.99% absorption) at the thickness of 3.2 mm and a maximum effective absorption bandwidth of 4.9 GHz (12.4-17.3 GHz) corresponding to an absorber thickness of 2.0 mm. Additionally, a broad effective absorption bandwidth of 13.7 GHz (4.3-18.0 GHz) can be reached up by adjusting the thickness from 1.5 to 5.0 mm. Furthermore, the highest effective absorption bandwidth of 5.7 GHz can be reached when the mass fraction is 15 wt%. The enhanced comprehensive electromagnetic wave absorption has close correlation with the well-designed heterogeneous multilayered microstructure, generated heterogeneous interfaces, conductive paths, surface functional groups, localized defects and synergistic effect between laminated Ti3C2Tx and conductive polypyrrole network, which significantly improve impedance matching and attenuation abilities. The superior absorbing performance together with strong absorption and broad bandwidth endows the Ti3C2Tx/PPy hybrids with the potential prospect to be advanced EM wave absorbers.

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

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

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

    2010-01-10

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

  13. Facile synthesis of iron oxides/reduced graphene oxide composites: application for electromagnetic wave absorption at high temperature.

    PubMed

    Zhang, Lili; Yu, Xinxin; Hu, Hongrui; Li, Yang; Wu, Mingzai; Wang, Zhongzhu; Li, Guang; Sun, Zhaoqi; Chen, Changle

    2015-03-19

    Iron oxides/reduced graphene oxide composites were synthesized by facile thermochemical reactions of graphite oxide and FeSO4 · 7H2O. By adjusting reaction temperature, α-Fe2O3/reduced graphene oxide and Fe3O4/reduced graphene oxide composites can be obtained conveniently. Graphene oxide and reduced graphene oxide sheets were demonstrated to regulate the phase transition from α-Fe2O3 to Fe3O4 via γ-Fe2O3, which was reported for the first time. The hydroxyl groups attached on the graphene oxide sheets and H2 gas generated during the annealing of graphene oxide are believed to play an important role during these phase transformations. These samples showed good electromagnetic wave absorption performance due to their electromagnetic complementary effect. These samples possess much better electromagnetic wave absorption properties than the mixture of separately prepared Fe3O4 with rGO, suggesting the crucial role of synthetic method in determining the product properties. Also, these samples perform much better than commercial absorbers. Most importantly, the great stability of these composites is highly advantageous for applications as electromagnetic wave absorption materials at high temperatures.

  14. Facile synthesis of iron oxides/reduced graphene oxide composites: application for electromagnetic wave absorption at high temperature

    PubMed Central

    Zhang, Lili; Yu, Xinxin; Hu, Hongrui; Li, Yang; Wu, Mingzai; Wang, Zhongzhu; Li, Guang; Sun, Zhaoqi; Chen, Changle

    2015-01-01

    Iron oxides/reduced graphene oxide composites were synthesized by facile thermochemical reactions of graphite oxide and FeSO4·7H2O. By adjusting reaction temperature, α-Fe2O3/reduced graphene oxide and Fe3O4/reduced graphene oxide composites can be obtained conveniently. Graphene oxide and reduced graphene oxide sheets were demonstrated to regulate the phase transition from α-Fe2O3 to Fe3O4 via γ-Fe2O3, which was reported for the first time. The hydroxyl groups attached on the graphene oxide sheets and H2 gas generated during the annealing of graphene oxide are believed to play an important role during these phase transformations. These samples showed good electromagnetic wave absorption performance due to their electromagnetic complementary effect. These samples possess much better electromagnetic wave absorption properties than the mixture of separately prepared Fe3O4 with rGO, suggesting the crucial role of synthetic method in determining the product properties. Also, these samples perform much better than commercial absorbers. Most importantly, the great stability of these composites is highly advantageous for applications as electromagnetic wave absorption materials at high temperatures. PMID:25788158

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

    PubMed

    Sirav, Bahriye; Seyhan, Nesrin

    2009-01-01

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

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

    DTIC Science & Technology

    1975-03-01

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

  17. Evaluating Temperature Changes of Brain Tissue Due to Induced Heating of Cell Phone Waves.

    PubMed

    Forouharmajd, Farhad; Pourabdian, Siamak; Ebrahimi, Hossein

    2018-01-01

    Worries have recently been increased in the absorption of radiofrequency waves and their destructing effects on human health by increasing use of cell phones (mobile phones). This study performed to determine the thermal changes due to mobile phone radio frequency waves in gray and white brain tissue. This study is an empirical study, where the thermal changes of electromagnetic waves resulted from cell phones (900 MHZ, specific absorption rate for head 1.18 w/kg) on the 15 brain tissue of a cow were analyzed in a compartment with three different thickness of 2 mm, 12 mm, and 22 mm, for 15 min. The Lutron thermometer (model: MT-917) with 0.01°C precision was used for measuring the tissue temperature. For each thickness was measured three times. Data analysis is done by Lutron and MATLAB software packages. In confronting of the tissue with the cell phone, the temperature was increased by 0.53°C in the 2 mm thickness that is the gray matter of the brain, increased by 0.99°C in the 12 mm thickness, and also increased by 0.92°C in the 22 mm thickness. Brain temperature showed higher rates than the base temperature after 15 min of confrontation with cell phone waves in all the three thicknesses. Cell phone radiated radio frequency waves were effective on increasing brain tissue temperature, and this temperature increase has cumulative effect on the tissue, being higher, for some time after the confrontation than the time with no confrontation.

  18. Evaluating Temperature Changes of Brain Tissue Due to Induced Heating of Cell Phone Waves

    PubMed Central

    Forouharmajd, Farhad; Pourabdian, Siamak; Ebrahimi, Hossein

    2018-01-01

    Background: Worries have recently been increased in the absorption of radiofrequency waves and their destructing effects on human health by increasing use of cell phones (mobile phones). This study performed to determine the thermal changes due to mobile phone radio frequency waves in gray and white brain tissue. Methods: This study is an empirical study, where the thermal changes of electromagnetic waves resulted from cell phones (900 MHZ, specific absorption rate for head 1.18 w/kg) on the 15 brain tissue of a cow were analyzed in a compartment with three different thickness of 2 mm, 12 mm, and 22 mm, for 15 min. The Lutron thermometer (model: MT-917) with 0.01°C precision was used for measuring the tissue temperature. For each thickness was measured three times. Data analysis is done by Lutron and MATLAB software packages. Results: In confronting of the tissue with the cell phone, the temperature was increased by 0.53°C in the 2 mm thickness that is the gray matter of the brain, increased by 0.99°C in the 12 mm thickness, and also increased by 0.92°C in the 22 mm thickness. Brain temperature showed higher rates than the base temperature after 15 min of confrontation with cell phone waves in all the three thicknesses. Conclusions: Cell phone radiated radio frequency waves were effective on increasing brain tissue temperature, and this temperature increase has cumulative effect on the tissue, being higher, for some time after the confrontation than the time with no confrontation. PMID:29861880

  19. Diffraction and quantum control of wave functions in nonresonant two-photon absorption

    NASA Astrophysics Data System (ADS)

    Li, Baihong; Pang, Huafeng; Wang, Doudou; Zhang, Tao; Dong, Ruifang; Li, Yongfang

    2018-03-01

    In this study, the nonresonant two-photon absorption process in a two-level atom, induced by a weak chirped pulse, is theoretically investigated in the frequency domain. An analytical expression of the wave function expressed by Fresnel functions is obtained, and the two-photon transition probability (TPTP) versus the integral bandwidth, spectral width, and chirp parameter is analyzed. The results indicate that the oscillation evolution of the TPTP result from quantum diffraction of the wave function, which can be explained by analogy with Fresnel diffraction from a wide slit in the spatial domain. Moreover, the ratio between the real and imaginary parts of the excited state wave function and, hence, the atomic polarization, can be controlled by the initial phase of the excitation pulse. In some special initial phase of the excitation pulse, the wave functions with purely real or imaginary parts can be obtained by measuring the population probability. This work provides a novel perspective for understanding the physical details of the interactions between atoms and chirped light pulses in the multiphoton process.

  20. Coronal mass ejection kinematics deduced from white light (Solar Mass Ejection Imager) and radio (Wind/WAVES) observations

    NASA Astrophysics Data System (ADS)

    Reiner, M. J.; Jackson, B. V.; Webb, D. F.; Mizuno, D. R.; Kaiser, M. L.; Bougeret, J.-L.

    2005-09-01

    White-light and radio observations are combined to deduce the coronal and interplanetary kinematics of a fast coronal mass ejection (CME) that was ejected from the Sun at about 1700 UT on 2 November 2003. The CME, which was associated with an X8.3 solar flare from W56°, was observed by the Mauna Loa and Solar and Heliospheric Observatory (SOHO) Large-Angle Spectrometric Coronograph (LASCO) coronagraphs to 14 R⊙. The measured plane-of-sky speed of the LASCO CME was 2600 km s-1. To deduce the kinematics of this CME, we use the plane-of-sky white light observations from both the Solar Mass Ejection Imager (SMEI) all-sky camera on board the Coriolis spacecraft and the SOHO/LASCO coronagraph, as well as the frequency drift rate of the low-frequency radio data and the results of the radio direction-finding analysis from the WAVES experiment on the Wind spacecraft. In agreement with the in situ observations for this event, we find that both the white light and radio observations indicate that the CME must have decelerated significantly beginning near the Sun and continuing well into the interplanetary medium. More specifically, by requiring self-consistency of all the available remote and in situ data, together with a simple, but not unreasonable, assumption about the general characteristic of the CME deceleration, we were able to deduce the radial speed and distance time profiles for this CME as it propagated from the Sun to 1 AU. The technique presented here, which is applicable to mutual SMEI/WAVES CME events, is expected to provide a more complete description and better quantitative understanding of how CMEs propagate through interplanetary space, as well as how the radio emissions, generated by propagating CME/shocks, relate to the shock and CME. This understanding can potentially lead to more accurate predictions for the onset times of space weather events, such as those that were observed during this unique period of intense solar activity.

  1. A multidisciplinary study of planetary, solar and astrophysical radio emissions

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

  2. Investigation of the effect of Alfven resonance absorption on fast wave current drive in ITER

    NASA Astrophysics Data System (ADS)

    Alava, M. J.; Heikkinen, J. A.; Hellsten, T.

    The use of frequencies below the ion cyclotron frequency of minority ion species or second harmonic of majority species has been proposed for fast wave current drive in order to reduce or to avoid ion cyclotron damping. For these scenarios, the Alfven resonance can appear on the high field side of a tokamak. The presence of this resonance causes parasitic absorption competing with the electron Landau damping and transit time magnetic pumping responsible for the fast wave current drive. In the present study, the mode conversion at the Alfven resonance is shown to be of the order of 5 to 10 percent in the current drive scenarios for the planned International Thermonuclear Experimental Reactor (ITER) experiment. However, if the single pass absorption in the center can be made sufficiently high, the conversion at the Alfven resonance becomes negligible.

  3. Enhanced Photocatalytic Activity of La3+-Doped TiO2 Nanotubes with Full Wave-Band Absorption

    NASA Astrophysics Data System (ADS)

    Xia, Minghao; Huang, Lingling; Zhang, Yubo; Wang, Yongqian

    2018-06-01

    TiO2 nanotubes doped with La3+ were synthesized by anodic oxidation method and the photocatalytic activity was detected by photodegrading methylene blue. As-prepared samples improved the absorption of both ultraviolet light and visible light and have a great enhancement on the photocatalytic activity while contrasting with the pristine TiO2 nanotubes. A tentative mechanism for the enhancement of photocatalytic activity with full wave-band absorption is proposed.

  4. Radio-wave propagation for space communications systems

    NASA Technical Reports Server (NTRS)

    Ippolito, L. J.

    1981-01-01

    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.

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

    PubMed

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

    2011-09-01

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

  6. Balancing Power Absorption and Fatigue Loads in Irregular Waves for an Oscillating Surge Wave Energy Converter

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

    Tom, Nathan M.; Yu, Yi-Hsiang; Wright, Alan D.

    The aim of this paper is to describe how to control the power-to-load ratio of a novel wave energy converter (WEC) in irregular waves. The novel WEC that is being developed at the National Renewable Energy Laboratory combines an oscillating surge wave energy converter (OSWEC) with control surfaces as part of the structure; however, this work only considers one fixed geometric configuration. This work extends the optimal control problem so as to not solely maximize the time-averaged power, but to also consider the power-take-off (PTO) torque and foundation forces that arise because of WEC motion. The objective function of themore » controller will include competing terms that force the controller to balance power capture with structural loading. Separate penalty weights were placed on the surge-foundation force and PTO torque magnitude, which allows the controller to be tuned to emphasize either power absorption or load shedding. Results of this study found that, with proper selection of penalty weights, gains in time-averaged power would exceed the gains in structural loading while minimizing the reactive power requirement.« less

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

    PubMed

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

    2008-09-25

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

  8. Jupiter radio bursts and particle acceleration

    NASA Technical Reports Server (NTRS)

    Desch, Michael D.

    1994-01-01

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

  9. Wavelength dependence in radio-wave scattering and specular-point theory

    NASA Technical Reports Server (NTRS)

    Tyler, G. L.

    1976-01-01

    Radio-wave scattering from natural surfaces contains a strong quasispecular component that at fixed wavelengths is consistent with specular-point theory, but often has a strong wavelength dependence that is not predicted by physical optics calculations under the usual limitations of specular-point models. Wavelength dependence can be introduced by a physical approximation that preserves the specular-point assumptions with respect to the radii of curvature of a fictitious, effective scattering surface obtained by smoothing the actual surface. A uniform low-pass filter model of the scattering process yields explicit results for the effective surface roughness versus wavelength. Interpretation of experimental results from planetary surfaces indicates that the asymptotic surface height spectral densities fall at least as fast as an inverse cube of spatial frequency. Asymptotic spectral densities for Mars and portions of the lunar surface evidently decrease more rapidly.

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

    NASA Technical Reports Server (NTRS)

    Manning, Robert M.

    2008-01-01

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

  11. Evidence for Ultra-Fast Outflows in Radio-Quiet AGNs. 2; Detailed Photoionization Modeling of Fe K-Shell Absorption Lines

    NASA Technical Reports Server (NTRS)

    Tombesi, Francesco; Clapp, M.; Reeves, J. N.; Palumbo, G. G. C.; Braito, V.; Dadina, M.

    2011-01-01

    X-ray absorption line spectroscopy has recently shown evidence for previously unknown Ultra-fast Outflows (UFOs) in radio-quiet AGNs. In the previous paper of this series we defined UFOs as those absorbers with an outflow velocity higher than 10,000km/s and assessed the statistical significance of the associated blue shifted FeK absorption lines in a large sample of 42 local radio-quiet AGNs observed with XMM-Newton. In the present paper we report a detailed curve of growth analysis and directly model the FeK absorbers with the Xstar photo-ionization code. We confirm that the frequency of sources in the radio-quiet sample showing UFOs is >35%. The outflow velocity distribution spans from \\sim10,000km/s (\\sim0.03c) up to \\siml00,000kmis (\\sim0.3c), with a peak and mean value of\\sim42,000km/s (\\sim0.14c). The ionization parameter is very high and in the range log\\xi 3-6 erg s/cm, with a mean value of log\\xi 4.2 erg s/cm. The associated column densities are also large, in the range N_H\\siml0(exp 22)-10(exp 24)/sq cm, with a mean value of N_H\\siml0(exp23)/sq cm. We discuss and estimate how selection effects, such as those related to the limited instrumental sensitivity at energies above 7keV, may hamper the detection of even higher velocities and higher ionization absorbers. We argue that, overall, these results point to the presence of extremely ionized and possibly almost Compton thick outflowing material in the innermost regions of AGNs. This also suggests that UFOs may potentially play a significant role in the expected cosmological feedback from AGNs and their study can provide important clues on the connection between accretion disks, winds and jets.

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

    NASA Astrophysics Data System (ADS)

    Mottez, F.; Zarka, P.

    2014-09-01

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

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

    NASA Astrophysics Data System (ADS)

    Bergman, J. E. S.

    2013-09-01

    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 μm-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.

  14. Space Weather Research in the Equatorial Region: A Philosophical Reinforcement

    NASA Astrophysics Data System (ADS)

    Chukwuma, Victor; Odunaike, Rasaki; Laoye, John

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

  15. Laboratory measurements of microwave and millimeter-wave properties of planetary atmospheric constituents

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    1989-01-01

    Accurate data on microwave and millimeter-wave properties of potential planetary atmospheric constituents is critical for the proper interpretation of radio occultation measurements, and of radio astronomical observations of both continuum and spectral line emissions. Such data is also needed to correct for atmospheric effects on radar studies of surface reflectivity. Since the refractive and absorptive properties of atmospheric constituents often vary drastically from theoretically-predicted profiles, especially under the extreme conditions characteristic of the planetary atmosphere, laboratory measurements under simulated planetary conditions are required. This paper reviews the instrumentation and techniques used for laboratory measurement of the refractivity and absorptivity of atmospheric constituents at wavelengths longward of 1 mm, under simulated planetary conditions (temperature, pressure, and broadening gases). Techniques for measuring both gases and condensates are considered. Also reviewed are the relative accuracies of the various techniques. Laboratory measurements are reviewed which have already been made, and additional measurements which are needed for interpretation of data from Venus and the outer planets, are highlighted.

  16. Wave Phenomena Associated with Interplanetary Shocks

    NASA Astrophysics Data System (ADS)

    Golla, T.; MacDowall, R. J.

    2016-12-01

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

  17. Spacecraft Radio Scintillation and Solar System Exploration

    NASA Technical Reports Server (NTRS)

    Woo, Richard

    1993-01-01

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

  18. Modeling ultrasonic compression wave absorption during the seeded crystallization of copper (II) sulphate pentahydrate from aqueous solution.

    PubMed

    Marshall, Thomas; Challis, Richard E; Holmes, Andrew K; Tebbutt, John S

    2002-11-01

    Ultrasonic compression wave absorption is investigated as a means to monitor the seeded crystallization of copper (II) sulphate pentahydrate from aqueous solution. Simple models are applied to predict crystal yield, crystal size distribution, and the changing nature of the continuous phase. The Allegra-Hawley scattering formulation is used to simulate ultrasonic absorption as crystallization proceeds. Experiments confirm that simulated attenuation is in agreement with measured results.

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

    NASA Astrophysics Data System (ADS)

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

    1985-12-01

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

  20. A Case Study of On-the-fly Wide-field Radio Imaging Applied to the Gravitational Wave Event GW151226

    NASA Astrophysics Data System (ADS)

    Mooley, K. P.; Frail, D. A.; Myers, S. T.; Kulkarni, S. R.; Hotokezaka, K.; Singer, L. P.; Horesh, A.; Kasliwal, M. M.; Cenko, S. B.; Hallinan, G.

    2018-04-01

    We apply a newly developed on-the-fly mosaicing technique on the Jansky Very Large Array (VLA) at 3 GHz in order to carry out a sensitive search for an afterglow from the Advanced LIGO binary black hole merger event GW151226. In three epochs between 1.5 and 6 months post-merger, we observed a 100 deg2 region, with more than 80% of the survey region having an rms sensitivity of better than 150 μJy/beam, in the northern hemisphere with a merger containment probability of 10%. The data were processed in near real time and analyzed to search for transients and variables. No transients were found but we have demonstrated the ability to conduct blind searches in a time-frequency phase space where the predicted afterglow signals are strongest. If the gravitational wave event is contained within our survey region, the upper limit on any late-time radio afterglow from the merger event at an assumed mean distance of 440 Mpc is about 1029 erg s‑1 Hz‑1. Approximately 1.5% of the radio sources in the field showed variability at a level of 30%, and can be attributed to normal activity from active galactic nuclei. The low rate of false positives in the radio sky suggests that wide-field imaging searches at a few Gigahertz can be an efficient and competitive search strategy. We discuss our search method in the context of the recent afterglow detection from GW170817 and radio follow-up in future gravitational wave observing runs.

  1. Coherent coupling between radio frequency, optical, and acoustic waves in piezo-optomechanical circuits

    PubMed Central

    Balram, Krishna C.; Davanço, Marcelo I.; Song, Jin Dong; Srinivasan, Kartik

    2016-01-01

    Optomechanical cavities have been studied for applications ranging from sensing to quantum information science. Here, we develop a platform for nanoscale cavity optomechanical circuits in which optomechanical cavities supporting co-localized 1550 nm photons and 2.4 GHz phonons are combined with photonic and phononic waveguides. Working in GaAs facilitates manipulation of the localized mechanical mode either with a radio frequency (RF) field through the piezo-electric effect, which produces acoustic waves that are routed and coupled to the optomechanical cavity by phononic crystal waveguides, or optically through the strong photoelastic effect. Along with mechanical state preparation and sensitive readout, we use this to demonstrate an acoustic wave interference effect, similar to atomic coherent population trapping, in which RF-driven coherent mechanical motion is cancelled by optically-driven motion. Manipulating cavity optomechanical systems with equal facility through both photonic and phononic channels enables new architectures for signal transduction between the optical, electrical, and mechanical domains. PMID:27446234

  2. Wave propagation and earth satellite radio emission studies

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

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

  3. Cosmology with Gravitational Wave/Fast Radio Burst Associations

    NASA Astrophysics Data System (ADS)

    Wei, Jun-Jie; Wu, Xue-Feng; Gao, He

    2018-06-01

    Recently, some theoretical models predicted that a small fraction of fast radio bursts (FRBs) could be associated with gravitational waves (GWs). In this Letter, we discuss the possibility of using GW/FRB association systems, if they are commonly detected in the future, as a complementary cosmic probe. We propose that upgraded standard sirens can be constructed from the joint measurements of luminosity distances D L derived from GWs and dispersion measures DMIGM derived from FRBs (i.e., the combination D L · DMIGM). Moreover, unlike the traditional standard-siren approach (i.e., the D L method) and the DMIGM method that rely on the optimization of the Hubble constant H 0, this D L · DMIGM method has the advantage of being independent of H 0. Through Monte Carlo simulations, we prove that the D L · DMIGM method is more effective for constraining cosmological parameters than D L or DMIGM separately, and that it enables us to achieve accurate multimessenger cosmology from approximately 100 GW/FRB systems. Additionally, even if GW/FRB associations do not exist, the methodology developed here can still be applied to those GWs and FRBs that occur at the same redshifts.

  4. Wave Forcing of Saturn's Equatorial Oscillation

    NASA Technical Reports Server (NTRS)

    Flasar, F. M.; Schlinder, P. J.; Guerlet, S.; Fouchet, T.

    2011-01-01

    Ground-based measurements and Cassini data from CIRS thermal-infrared spectra and radio-occultation soundings have characterized the spatial structure and temporal behavior of a 15-year equatorial oscillation in Saturn's stratosphere. The equatorial region displays a vertical pattern of alternating warm and cold anomalies and, concomitantly, easterly and westerly winds relative to the cloud-top winds, with a peak-to-peak amplitude of 200 m/s. Comparison of the Cassini data over a four-year period has established that the pattern of mean zonal winds and temperatures descends at a rate of roughly I scale height over 4 years. This behavior is reminiscent of the equatorial oscillations in Earth's middle atmosphere. Here the zonal-mean spatial structure and descending pattern are driven by the absorption of vertically propagating waves. The maximum excursions in the pattern of easterly and westerly winds is determined by the limits of the zonal phase velocities of the waves. Here we report on the characterization of the waves seen in the temperature profiles retrieved from the Cassini radio-occultation soundings. The equatorial profiles exhibit a complex pattern of wavelike structure with dimensions one pressure scale height and smaller. We combine a spectral decomposition with a WKBJ analysis, where the vertical wavelength is assumed to vary slowly with the ambient static stability and doppler-shifted phase velocity of the wave. Use of the temperature and zonal wind maps from CIRS makes this approach viable. On Earth, the wave forcing associated with the equatorial oscillations generates secondary meridional circulations that affect the mean flow and planetary wave ducting well away from the equator. This may relate to the triggering of the recently reported mid-latitude storms on Saturn.

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

    PubMed Central

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

    2008-01-01

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

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

    DTIC Science & Technology

    1982-07-01

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

  7. Influence of synchrotron self-absorption on 21-cm experiments

    NASA Astrophysics Data System (ADS)

    Zheng, Qian; Wu, Xiang-Ping; Gu, Jun-Hua; Wang, Jingying; Xu, Haiguang

    2012-08-01

    The presence of spectral curvature resulting from the synchrotron self-absorption of extragalactic radio sources could break down the spectral smoothness feature. This leads to the premise that the bright radio foreground can be successfully removed in 21-cm experiments that search for the epoch of reionization (EoR). We present a quantitative estimate of the effect of the spectral curvature resulting from the synchrotron self-absorption of extragalactic radio sources on the measurement of the angular power spectrum of the low-frequency sky. We incorporate a phenomenological model, which is characterized by the fraction (f) of radio sources with turnover frequencies in the range of 100-1000 MHz and by a broken power law for the spectral transition around the turnover frequencies νm, into simulated radio sources over a small sky area of 10° × 10°. We compare statistically the changes in their residual maps with and without the inclusion of the synchrotron self-absorption of extragalactic radio sources after the bright sources of S150 MHz ≥100 mJy are excised. Furthermore, the best-fitting polynomials in the frequency domain on each pixel are subtracted. It has been shown that the effect of synchrotron self-absorption on the detection of the EoR depends sensitively on the spectral profiles of the radio sources around the turnover frequencies νm. A hard transition model, described by the broken power law with the turnover of spectral index at νm, would leave pronounced imprints on the residual background and would therefore cause serious confusion with the cosmic EoR signal. However, the spectral signatures on the angular power spectrum of the extragalactic foreground, generated by a soft transition model in which the rising and falling power laws of the spectral distribution around νm are connected through a smooth transition spanning ≥200 MHz in a characteristic width, can be fitted and consequently subtracted by the use of polynomials to an acceptable

  8. Investigation of radio astronomy image processing techniques for use in the passive millimetre-wave security screening environment

    NASA Astrophysics Data System (ADS)

    Taylor, Christopher T.; Hutchinson, Simon; Salmon, Neil A.; Wilkinson, Peter N.; Cameron, Colin D.

    2014-06-01

    Image processing techniques can be used to improve the cost-effectiveness of future interferometric Passive MilliMetre Wave (PMMW) imagers. The implementation of such techniques will allow for a reduction in the number of collecting elements whilst ensuring adequate image fidelity is maintained. Various techniques have been developed by the radio astronomy community to enhance the imaging capability of sparse interferometric arrays. The most prominent are Multi- Frequency Synthesis (MFS) and non-linear deconvolution algorithms, such as the Maximum Entropy Method (MEM) and variations of the CLEAN algorithm. This investigation focuses on the implementation of these methods in the defacto standard for radio astronomy image processing, the Common Astronomy Software Applications (CASA) package, building upon the discussion presented in Taylor et al., SPIE 8362-0F. We describe the image conversion process into a CASA suitable format, followed by a series of simulations that exploit the highlighted deconvolution and MFS algorithms assuming far-field imagery. The primary target application used for this investigation is an outdoor security scanner for soft-sided Heavy Goods Vehicles. A quantitative analysis of the effectiveness of the aforementioned image processing techniques is presented, with thoughts on the potential cost-savings such an approach could yield. Consideration is also given to how the implementation of these techniques in CASA might be adapted to operate in a near-field target environment. This may enable a much wider usability by the imaging community outside of radio astronomy and thus would be directly relevant to portal screening security systems in the microwave and millimetre wave bands.

  9. Balancing Power Absorption and Fatigue Loads in Irregular Waves for an Oscillating Surge Wave Energy Converter: Preprint

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

    Tom, Nathan M.; Yu, Yi-Hsiang; Wright, Alan D.

    The aim of this paper is to describe how to control the power-to-load ratio of a novel wave energy converter (WEC) in irregular waves. The novel WEC that is being developed at the National Renewable Energy Laboratory combines an oscillating surge wave energy converter (OSWEC) with control surfaces as part of the structure; however, this work only considers one fixed geometric configuration. This work extends the optimal control problem so as to not solely maximize the time-averaged power, but to also consider the power-take-off (PTO) torque and foundation forces that arise because of WEC motion. The objective function of themore » controller will include competing terms that force the controller to balance power capture with structural loading. Separate penalty weights were placed on the surge-foundation force and PTO torque magnitude, which allows the controller to be tuned to emphasize either power absorption or load shedding. Results of this study found that, with proper selection of penalty weights, gains in time-averaged power would exceed the gains in structural loading while minimizing the reactive power requirement.« less

  10. LASER PLASMA AND LASER APPLICATIONS: Plasma transparency in laser absorption waves in metal capillaries

    NASA Astrophysics Data System (ADS)

    Anisimov, V. N.; Kozolupenko, A. P.; Sebrant, A. Yu

    1988-12-01

    An experimental investigation was made of the plasma transparency to heating radiation in capillaries when absorption waves propagated in these capillaries as a result of interaction with a CO2 laser pulse of 5-μs duration. When the length of the capillary was in excess of 20 mm, total absorption of the radiation by the plasma was observed at air pressures of 1-100 kPa. When the capillary length was 12 mm, a partial recovery of the transparency took place. A comparison was made with the dynamics and recovery of the plasma transparency when breakdown of air took place near the free surface.

  11. Gigahertz-peaked Spectra Pulsars and Thermal Absorption Model

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

    Kijak, J.; Basu, R.; Lewandowski, W.

    2017-05-10

    We present the results of our radio interferometric observations of pulsars at 325 and 610 MHz using the Giant Metrewave Radio Telescope. We used the imaging method to estimate the flux densities of several pulsars at these radio frequencies. The analysis of the shapes of the pulsar spectra allowed us to identify five new gigahertz-peaked spectra (GPS) pulsars. Using the hypothesis that the spectral turnovers are caused by thermal free–free absorption in the interstellar medium, we modeled the spectra of all known objects of this kind. Using the model, we were able to put some observational constraints on the physicalmore » parameters of the absorbing matter, which allows us to distinguish between the possible sources of absorption. We also discuss the possible effects of the existence of GPS pulsars on future search surveys, showing that the optimal frequency range for finding such objects would be from a few GHz (for regular GPS sources) to possibly 10 GHz for pulsars and radio magnetars exhibiting very strong absorption.« less

  12. Electron-cyclotron wave propagation, absorption and current drive in the presence of neoclassical tearing modes

    NASA Astrophysics Data System (ADS)

    Isliker, Heinz; Chatziantonaki, Ioanna; Tsironis, Christos; Vlahos, Loukas

    2012-09-01

    We analyze the propagation of electron-cyclotron waves, their absorption and current drive when neoclassical tearing modes (NTMs), in the form of magnetic islands, are present in a tokamak plasma. So far, the analysis of the wave propagation and power deposition in the presence of NTMs has been performed mainly in the frame of an axisymmetric magnetic field, ignoring any effects from the island topology. Our analysis starts from an axisymmetric magnetic equilibrium, which is perturbed such as to exhibit magnetic islands. In this geometry, we compute the wave evolution with a ray-tracing code, focusing on the effect of the island topology on the efficiency of the absorption and current drive. To increase the precision in the calculation of the power deposition, the standard analytical flux-surface labeling for the island region has been adjusted from the usual cylindrical to toroidal geometry. The propagation up to the O-point is found to be little affected by the island topology, whereas the power absorbed and the driven current are significantly enhanced, because the resonant particles are bound to the small volumes in between the flux surfaces of the island. The consequences of these effects on the NTM evolution are investigated in terms of the modified Rutherford equation.

  13. Programme of Indian Centre for Space Physics using Very Low Frequency Radio Waves

    NASA Astrophysics Data System (ADS)

    Chakrabarti, Sandip Kumar; Sasmal, Sudipta; Pal, Sujay; Kanta Maji, Surya; Ray, Suman

    Indian Centre for Space Physics conducted two major VLF campaigns all over Indian Sub-continent to study the propagation effects of VLF radio waves. It made multi-receiver observations during solar eclipse. ICSP not only recorded multitudes of solar flares, it also reproduced VLF observation from ab initio calculation. ICSP extended its study to the field of earthquake predictions using signal anomalies and using case by case studies as well as statistical analysis, showed that anomalies are real and more studies are required to understand them. Using earth as a gigantic detector, it detected ionospheric perturbations due to soft gamma-ray repeaters and gamma-ray bursts.

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

  15. Fast Radio Bursts

    NASA Astrophysics Data System (ADS)

    Kaspi, Victoria M.

    2017-01-01

    Fast Radio Bursts (FRBs) are a recently discovered phenomenon consisting of short (few ms) bursts of radio waves that have dispersion measures that strongly suggest an extragalactic and possibly cosmological origin. Current best estimates for the rate of FRBs is several thousand per sky per day at radio frequencies near 1.4 GHz. Even with so high a rate, to date, fewer than 20 FRBs have been reported, with one source showing repeated bursts. In this talk I will describe known FRB properties including what is known about the lone repeating source, as well as models for the origin of these mysterious events. I will also describe the CHIME radio telescope, currently under construction in Canada. Thanks to its great sensitivity and unprecedented field-of-view, CHIME promises major progress on FRBs.

  16. SPATIAL DISTRIBUTIONS OF ABSORPTION, LOCAL SUPPRESSION, AND EMISSIVITY REDUCTION OF SOLAR ACOUSTIC WAVES IN MAGNETIC REGIONS

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

    Chou, D.-Y.; Yang, M.-H.; Zhao Hui

    Observed acoustic power in magnetic regions is lower than the quiet Sun because of absorption, emissivity reduction, and local suppression of solar acoustic waves in magnetic regions. In the previous studies, we have developed a method to measure the coefficients of absorption, emissivity reduction, and local suppression of sunspots. In this study, we go one step further to measure the spatial distributions of three coefficients in two active regions, NOAA 9055 and 9057. The maps of absorption, emissivity reduction, and local suppression coefficients correlate with the magnetic map, including plage regions, except the emissivity reduction coefficient of NOAA 9055 wheremore » the emissivity reduction coefficient is too weak and lost among the noise.« less

  17. The column density distribution of hard X-ray radio galaxies

    NASA Astrophysics Data System (ADS)

    Panessa, F.; Bassani, L.; Landi, R.; Bazzano, A.; Dallacasa, D.; La Franca, F.; Malizia, A.; Venturi, T.; Ubertini, P.

    2016-09-01

    In order to investigate the role of absorption in active galactic nuclei (AGN) with jets, we have studied the column density distribution of a hard X-ray selected sample of radio galaxies, derived from the INTEGRAL/Imager on Board the Integral Satellite (IBIS) and Swift/The Burst Alert Telescope (BAT) AGN catalogues (˜7-10 per cent of the total AGN population). The 64 radio galaxies have a typical FR II radio morphology and are characterized by high 20-100 keV luminosities (from 1042 to 1046 erg s-1) and high Eddington ratios (log LBol/LEdd typically larger than ˜0.01). The observed fraction of absorbed AGN (NH > 1022 cm-2) is around 40 per cent among the total sample, and ˜75 per cent among type 2 AGN. The majority of obscured AGN are narrow-line objects, while unobscured AGN are broad-line objects, obeying to the zeroth-order predictions of unified models. A significant anti-correlation between the radio core dominance parameter and the X-ray column density is found. The observed fraction of Compton thick AGN is ˜2-3 per cent, in comparison with the 5-7 per cent found in radio-quiet hard X-ray selected AGN. We have estimated the absorption and Compton thick fractions in a hard X-ray sample containing both radio galaxies and non-radio galaxies and therefore affected by the same selection biases. No statistical significant difference was found in the absorption properties of radio galaxies and non-radio galaxies sample. In particular, the Compton thick objects are likely missing in both samples and the fraction of obscured radio galaxies appears to decrease with luminosity as observed in hard X-ray non-radio galaxies.

  18. Rational Construction of Uniform CoNi-Based Core-Shell Microspheres with Tunable Electromagnetic Wave Absorption Properties.

    PubMed

    Chen, Na; Jiang, Jian-Tang; Xu, Cheng-Yan; Yan, Shao-Jiu; Zhen, Liang

    2018-02-16

    Core-shell particles with integration of ferromagnetic core and dielectric shell are attracting extensive attention for promising microwave absorption applications. In this work, CoNi microspheres with conical bulges were synthesized by a simple and scalable liquid-phase reduction method. Subsequent coating of dielectric materials was conducted to acquire core-shell structured CoNi@TiO 2 composite particles, in which the thickness of TiO 2 is about 40 nm. The coating of TiO 2 enables the absorption band of CoNi to effectively shift from K u to S band, and endows CoNi@TiO 2 microspheres with outstanding electromagnetic wave absorption performance along with a maximum reflection loss of 76.6 dB at 3.3 GHz, much better than that of bare CoNi microspheres (54.4 dB at 17.8 GHz). The enhanced EMA performance is attributed to the unique core-shell structures, which can induce dipole polarization and interfacial polarization, and tune the dielectric properties to achieve good impedance matching. Impressively, TiO 2 coating endows the composites with better microwave absorption capability than CoNi@SiO 2 microspheres. Compared with SiO 2 , TiO 2 dielectric shells could protect CoNi microspheres from merger and agglomeration during annealed. These results indicate that CoNi@TiO 2 core-shell microspheres can serve as high-performance absorbers for electromagnetic wave absorbing application.

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

    PubMed

    Tsuda, Toshitaka

    2014-01-01

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

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

    PubMed Central

    TSUDA, Toshitaka

    2014-01-01

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

  1. VLBI survey of compact broad absorption line quasars with balnicity index BI = 0

    NASA Astrophysics Data System (ADS)

    Cegłowski, M.; Kunert-Bajraszewska, M.; Roskowiński, C.

    2015-06-01

    We present high-resolution observations, using both the European VLBI Network (EVN) at 1.7 GHz and the Very Long Baseline Array (VLBA) at 5 and 8.4 GHz, to image radio structures of 14 compact sources classified as broad absorption line (BAL) quasars based on the absorption index (AI). All sources but one were resolved, with the majority showing core-jet morphology typical for radio-loud quasars. We discuss in detail the most interesting cases. The high radio luminosities and small linear sizes of the observed objects indicate they are strong young active galactic nuclei. Nevertheless, the distribution of the radio-loudness parameter, log RI, of a larger sample of AI quasars shows that the objects observed by us constitute the most luminous, small subgroup of the AI population. Additionally, we report that for the radio-loudness parameter, the distribution of AI quasars and that for those selected using the traditional balnicity index differ significantly. Strong absorption is connected with lower log RI and thus probably larger viewing angles. Since the AI quasars have on average larger log RI, the orientation can mean that we see them less absorbed. However, we suggest that the orientation is not the only parameter that affects the detected absorption. That the strong absorption is associated with the weak radio emission is equally important and worth exploring.

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

    NASA Astrophysics Data System (ADS)

    Kuznetsov, V. D.

    2015-06-01

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

  3. Full-duplex radio-over-fiber system with tunable millimeter-wave signal generation and wavelength reuse for upstream signal.

    PubMed

    Wang, Yiqun; Pei, Li; Li, Jing; Li, Yueqin

    2017-06-10

    A full-duplex radio-over-fiber system is proposed, which provides both the generation of a millimeter-wave (mm-wave) signal with tunable frequency multiplication factors (FMFs) and wavelength reuse for uplink data. A dual-driving Mach-Zehnder modulator and a phase modulator are cascaded to form an optical frequency comb. An acousto-optic tunable filter based on a uniform fiber Bragg grating (FBG-AOTF) is employed to select three target optical sidebands. Two symmetrical sidebands are chosen to generate mm waves with tunable FMFs up to 16, which can be adjusted by changing the frequency of the applied acoustic wave. The optical carrier is reused at the base station for uplink connection. FBG-AOTFs driven by two acoustic wave signals are experimentally fabricated and further applied in the proposed scheme. Results of the research indicate that the 2-Gbit/s data can be successfully transmitted over a 25-km single-mode fiber for bidirectional full-duplex channels with power penalty of less than 2.6 dB. The feasibility of the proposed scheme is verified by detailed simulations and partial experiments.

  4. Perfect absorption of low-frequency sound waves by critically coupled subwavelength resonant system

    NASA Astrophysics Data System (ADS)

    Long, Houyou; Cheng, Ying; Tao, Jiancheng; Liu, Xiaojun

    2017-01-01

    The perfect absorption (PA) for low-frequency audible sound waves has been achieved by critically coupling the inherent loss factor to the inherent leakage factor of a system, which is constructed by attaching a deep-subwavelength lossy resonant plate (LRP) to a backed rigid wall closely. We have certified it by using the graphical method in the complex frequency plane. By coupling the LRP to an air cavity in front of the rigid wall, the high efficient (>80%) low-frequency broadband absorption is obtained from 99.1 Hz to 294.8 Hz. Here, the thickness of LRP is only 1/13.5 of the relevant wavelength at 294.8 Hz. The impedance analyses further demonstrate that the impedances are perfectly matched between the system and the surrounding background medium at PA.

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  6. FLARE-GENERATED SHOCK WAVE PROPAGATION THROUGH SOLAR CORONAL ARCADE LOOPS AND AN ASSOCIATED TYPE II RADIO BURST

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

    Kumar, Pankaj; Cho, Kyung-Suk; Innes, D. E., E-mail: pankaj@kasi.re.kr

    2016-09-01

    This paper presents multiwavelength observations of a flare-generated type II radio burst. The kinematics of the shock derived from the type II burst closely match a fast extreme ultraviolet (EUV) wave seen propagating through coronal arcade loops. The EUV wave was closely associated with an impulsive M1.0 flare without a related coronal mass ejection, and was triggered at one of the footpoints of the arcade loops in active region NOAA 12035. It was initially observed in the 335 Å images from the Atmospheric Image Assembly with a speed of ∼800 km s{sup −1} and it accelerated to ∼1490 km s{supmore » −1} after passing through the arcade loops. A fan–spine magnetic topology was revealed at the flare site. A small, confined filament eruption (∼340 km s{sup −1}) was also observed moving in the opposite direction to the EUV wave. We suggest that breakout reconnection in the fan–spine topology triggered the flare and associated EUV wave that propagated as a fast shock through the arcade loops.« less

  7. GPS radio occultation simulation experiments for the upcoming Strateole-2 superpressure balloon campaign investigating equatorial waves

    NASA Astrophysics Data System (ADS)

    Haase, J. S.; Cao, B.; Alexander, M. J.; Zhang, W.

    2017-12-01

    Deep tropical convection influences the transport of mass and momentum from the equatorial upper troposphere into the lower stratosphere through the generation and interaction of waves at a broad range of scales. The France-US collaborative Stratéole-2 project will explore equatorial waves in the tropopause region with super-pressure balloons, designed to drift on quasi-Lagrangian trajectories in the lower stratosphere. The Stratéole-2 program will launch 5 balloons from the Seychelles in the Indian Ocean in 2018-2019, and 20 balloons in 2020-2021, each with a flight duration of about 80 days. Five balloons will carry the Radio OCcultation (ROC2) instrument at 20 km altitude to execute a continuous sequence of temperature profiles on either side of the balloon trajectory to sample the equatorial wave field in three dimensions. It will also carry a micro-lidar for detecting cirrus and convective cloud tops. The goals are to describe the horizontal and vertical structure of tropical waves and their impact on cirrus formation and to investigate the relationships of waves to convective clouds. The GPS measurements quantify wave activity by providing precise estimates of balloon velocity and height perturbations due to waves and by providing refractivity profiles that are sensitive to vertical temperature fluctuations caused by waves. We present ray-tracing simulations of the propagation of GPS signals through the Earth's atmosphere, where they will be bent and delayed due to the gradient of atmospheric refractive index. European Centre for Medium-Range Weather Forecasts (ECMWF) analyses are used to construct the refractive index of the equatorial atmosphere, in which abundant atmospheric waves are present. With the known GPS signal geometry, the excess phase/Doppler are simulated that reflect the wave signatures. The resulting refractivity retrievals provide guidance for interpreting the spectral range of waves that the ROC2 instruments are most likely to reveal.

  8. The effect of solar radio bursts on the GNSS radio occultation signals

    NASA Astrophysics Data System (ADS)

    Yue, Xinan; Schreiner, William S.; Kuo, Ying-Hwa; Zhao, Biqiang; Wan, Weixing; Ren, Zhipeng; Liu, Libo; Wei, Yong; Lei, Jiuhou; Solomon, Stan; Rocken, Christian

    2013-09-01

    radio burst (SRB) is the radio wave emission after a solar flare, covering a broad frequency range, originated from the Sun's atmosphere. During the SRB occurrence, some specific frequency radio wave could interfere with the Global Navigation Satellite System (GNSS) signals and therefore disturb the received signals. In this study, the low Earth orbit- (LEO-) based high-resolution GNSS radio occultation (RO) signals from multiple satellites (COSMIC, CHAMP, GRACE, SAC-C, Metop-A, and TerraSAR-X) processed in University Corporation for Atmospheric Research (UCAR) were first used to evaluate the effect of SRB on the RO technique. The radio solar telescope network (RSTN) observed radio flux was used to represent SRB occurrence. An extreme case during 6 December 2006 and statistical analysis during April 2006 to September 2012 were studied. The LEO RO signals show frequent loss of lock (LOL), simultaneous decrease on L1 and L2 signal-to-noise ratio (SNR) globally during daytime, small-scale perturbations of SNR, and decreased successful retrieval percentage (SRP) for both ionospheric and atmospheric occultations during SRB occurrence. A potential harmonic band interference was identified. Either decreased data volume or data quality will influence weather prediction, climate study, and space weather monitoring by using RO data during SRB time. Statistically, the SRP of ionospheric and atmospheric occultation retrieval shows ~4% and ~13% decrease, respectively, while the SNR of L1 and L2 show ~5.7% and ~11.7% decrease, respectively. A threshold value of ~1807 SFU of 1415 MHz frequency, which can result in observable GNSS SNR decrease, was derived based on our statistical analysis.

  9. High temperature measurement of water vapor absorption

    NASA Technical Reports Server (NTRS)

    Keefer, Dennis; Lewis, J. W. L.; Eskridge, Richard

    1985-01-01

    An investigation was undertaken to measure the absorption coefficient, at a wavelength of 10.6 microns, for mixtures of water vapor and a diluent gas at high temperature and pressure. The experimental concept was to create the desired conditions of temperature and pressure in a laser absorption wave, similar to that which would be created in a laser propulsion system. A simplified numerical model was developed to predict the characteristics of the absorption wave and to estimate the laser intensity threshold for initiation. A non-intrusive method for temperature measurement utilizing optical laser-beam deflection (OLD) and optical spark breakdown produced by an excimer laser, was thoroughly investigated and found suitable for the non-equilibrium conditions expected in the wave. Experiments were performed to verify the temperature measurement technique, to screen possible materials for surface initiation of the laser absorption wave and to attempt to initiate an absorption wave using the 1.5 kW carbon dioxide laser. The OLD technique was proven for air and for argon, but spark breakdown could not be produced in helium. It was not possible to initiate a laser absorption wave in mixtures of water and helium or water and argon using the 1.5 kW laser, a result which was consistent with the model prediction.

  10. STEREO/Waves Education and Public Outreach

    NASA Astrophysics Data System (ADS)

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

    2005-05-01

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

  11. Two-photon absorption laser-induced fluorescence measurements of atomic nitrogen in a radio-frequency atmospheric-pressure plasma jet

    NASA Astrophysics Data System (ADS)

    Wagenaars, E.; Gans, T.; O'Connell, D.; Niemi, K.

    2012-08-01

    The first direct measurements of atomic nitrogen species in a radio-frequency atmospheric-pressure plasma jet (APPJ) are presented. Atomic nitrogen radicals play a key role in new plasma medicine applications of APPJs. The measurements were performed with a two-photon absorption laser-induced fluorescence diagnostic, using 206.65 nm laser photons for the excitation of ground-state N atoms and observing fluorescence light around 744 nm. The APPJ was run with a helium gas flow of 1 slm and varying small admixtures of molecular nitrogen of 0-0.7 vol%. A maximum in the measured N concentration was observed for an admixture of 0.25 vol% N2.

  12. Kinetic Simulations of Type II Radio Burst Emission Processes

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  13. X-Ray Absorption Toward the Einstein Ring Source PKS 1830-211

    NASA Technical Reports Server (NTRS)

    Mathur, Smita; Nair, Sunita

    1997-01-01

    PKS 1830-211 is an unusually radio-loud gravitationally lensed quasar. In the radio spectrum, the system appears as two compact, dominant features surrounded by relatively extended radio emission that forms an Einstein ring. As the line of sight to it passes close to our Galactic center, PKS 1830-211 has not been detected in wave bands other than the radio and X-ray so far. Here we present X-ray data of PKS 1830-211 observed with ROSAT Position Sensitive Proportional Counter. The X-ray spectrum shows that absorption in excess of the Galactic contribution is highly likely, which at the redshift of the lensing galaxy (z(sub t)=0.886) corresponds to N(sub H)=3.5((sup 0.6)(sub -0.5))x10(exp 22) atoms sq cm. The effective optical extinction is large, A(sub V)(observed) is greater than or approximately 5.8. When corrected for this additional extinction, the two-point optical to X-ray slope alpha(sub ox) of PKS 1830-211 lies just within the observed range of quasars. It is argued here that both compact images must be covered by the X-ray absorber(s) that we infer to be the lensing galaxy (galaxies). The dust-to-gas ratio along the line of sight within the lensing galaxy is likely to be somewhat larger than for our Galaxy.

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

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

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

  15. Nitric oxide concentration near the mesopause as deduced from ionospheric absorption measurements

    NASA Astrophysics Data System (ADS)

    Lastovicka, J.

    The upper-D-region NO concentration is calculated on the basis of published 2775-kHz-absorption, Lyman-alpha (OSO-5), and X-ray (Solrad-9) data obtained over Central Europe in June-August 1969, 1970, and 1972. Ionization-rate and radio-wave-absorption profiles for solar zenith angles of 60, 70 and 40 deg are computed, presented graphically, and compared with model calculations to derive the NO-concentration correction coefficients necessary to make the Lyman-alpha/X-ray flux ratios of the models of Meira (1971), Baker et al. (1977), Tohmatsu and Iwagami (1976), and Tisone (1973) agree with the observed ratios. Values of the corrected NO concentration include 6.5 and 8.5 x 10 to the 13th/cu m at 78 and 90 km, respectively. The values are shown to be higher than those of standard models but within the range of observed concentrations.

  16. Radio Transients and their Environments

    NASA Astrophysics Data System (ADS)

    Rajwade, Kaustubh

    The interstellar medium is the principal ingredient for star formation and hence, it is necessary to study the properties of the interstellar medium. Radio sources in our Galaxy and beyond can be used as a probe of the intervening medium. In this dissertation, I present an attempt to use radio transients like pulsars and fast radio bursts and their interactions with the environment around them to study interstellar medium. We show that radio emission from pulsars is absorbed by dense ionized gas in their surroundings, causing a turnover in their flux density spectrum that can be used to reveal information about the absorbing medium. We carried out a multi-wavelength observation campaign of PSR B0611+22. The pulsar shows peculiar emission variability that is broadband in nature. Moreover, we show that the flux density spectrum of B0611+22 is unusual which can be attributed to the environment it lies in. We also present predictions of fast radio burst detections from upcoming low frequency surveys. We show that future surveys with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) will be able to detect 1 radio burst per hour even if the radio burst undergoes significant absorption and scattering. Finally, we present our results of pulsar population synthesis to understand the pulsar population in the Galactic Centre (GC) and place conservative upper limits on the GC pulsar population. We obtain an upper limit of 52 CPs and 10,000 MSPs in the GC. The dense, ionized environment of the GC gives us the opportunity to predict the probability of detection by considering scattering and absorption as the principle sources of flux mitigation. Our results suggest that the optimal frequency range for a pulsar survey in the GC is 9-14 GHz. A larger sample of absorbed spectrum pulsars and fast radio bursts will be beneficial not only for the study of emission processes but also for discerning the properties of the material permeating through space.

  17. X-ray absorption radiography for high pressure shock wave studies

    NASA Astrophysics Data System (ADS)

    Antonelli, L.; Atzeni, S.; Batani, D.; Baton, S. D.; Brambrink, E.; Forestier-Colleoni, P.; Koenig, M.; Le Bel, E.; Maheut, Y.; Nguyen-Bui, T.; Richetta, M.; Rousseaux, C.; Ribeyre, X.; Schiavi, A.; Trela, J.

    2018-01-01

    The study of laser compressed matter, both warm dense matter (WDM) and hot dense matter (HDM), is relevant to several research areas, including materials science, astrophysics, inertial confinement fusion. X-ray absorption radiography is a unique tool to diagnose compressed WDM and HDM. The application of radiography to shock-wave studies is presented and discussed. In addition to the standard Abel inversion to recover a density map from a transmission map, a procedure has been developed to generate synthetic radiographs using density maps produced by the hydrodynamics code DUED. This procedure takes into account both source-target geometry and source size (which plays a non negligible role in the interpretation of the data), and allows to reproduce transmission data with a good degree of accuracy.

  18. Solar radio continuum storms

    NASA Technical Reports Server (NTRS)

    1974-01-01

    Radio noise continuum emission observed in metric and decametric wave frequencies is discussed. The radio noise is associated with actively varying sunspot groups accompanied by the S-component of microwave radio emissions. It is shown that the S-component emission in microwave frequencies generally occurs several days before the emission of the noise continuum storms of lower frequencies. It is likely that energetic electrons, 10 to 100 Kev, accelerated in association with the variation of sunspot magnetic fields, are the sources of the radio emissions. A model is considered to explain the relation of burst storms on radio noise. An analysis of the role of energetic electrons on the emissions of both noise continuum and type III burst storms is presented. It is shown that instabilities associated with the electrons and their relation to their own stabilizing effects are important in interpreting both of these storms.

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

    NASA Astrophysics Data System (ADS)

    Hartogh, P.; Ilyushin, Ya. A.

    2016-10-01

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

  20. An absorptive single-pole four-throw switch using multiple-contact MEMS switches and its application to a monolithic millimeter-wave beam-forming network

    NASA Astrophysics Data System (ADS)

    Lee, Sanghyo; Kim, Jong-Man; Kim, Yong-Kweon; Kwon, Youngwoo

    2009-01-01

    In this paper, a new absorptive single-pole four-throw (SP4T) switch based on multiple-contact switching is proposed and integrated with a Butler matrix to demonstrate a monolithic beam-forming network at millimeter waves (mm waves). In order to simplify the switching driving circuit and reduce the number of unit switches in an absorptive SP4T switch, the individual switches were replaced with long-span multiple-contact switches using stress-free single-crystalline-silicon MEMS technology. This approach improves the mechanical stability as well as the manufacturing yield, thereby allowing successful integration into a monolithic beam former. The fabricated absorptive SP4T MEMS switch shows insertion loss less than 1.3 dB, return losses better than 11 dB at 30 GHz and wideband isolation performance higher than 39 dB from 20 to 40 GHz. The absorptive SP4T MEMS switch is integrated with a 4 × 4 Butler matrix on a single chip to implement a monolithic beam-forming network, directing beam into four distinct angles. Array factors from the measured data show that the proposed absorptive SPnT MEMS switch can be effectively used for high-performance mm-wave beam-switching systems. This work corresponds to the first demonstration of a monolithic beam-forming network using switched beams.

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

    PubMed

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

    2013-11-04

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

  2. Thermal electrostatic noise and radio waves spectroscopy (SORBET) on BepiColombo/MMO/PWI

    NASA Astrophysics Data System (ADS)

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

    2003-04-01

    The SORBET experiment is a part of the radio and Plasma Waves Instrument (PWI) onboard BepiColombo/Mercury Magnetospheric Orbiter (MMO), which include remote and in-situ measurements of wave (electromagnetic and electrostatic), for studying the structure and dynamics (regions, boundaries, acceleration, dissipation processes...) of the Hermean magnetosphere/exo-ionosphere system and its interaction with the solar wind. More specific SORBET goals are: - Mapping of (cold) electron density and temperature in the solar wind and Hermean magnetosphere and exo-ionosphere, via the technique of Quasi-Thermal Noise (QTN) spectroscopy (and also analysis of Bernstein modes and upper-hybrid emissions). The quasi-thermal noise is due to the thermal motions of the particles, which produce electrostatic fluctuations. This noise is detected by any sensitive receiver at the ports of an electric antenna immersed in a plasma and can be used to measure in-situ the plasma density, temperature and bulk velocity. The basic reason is that this noise can be formally calculated as a function of both the particle velocity distributions and the antenna geometry. So, conversely, the "spectroscopy" of this noise reveals the local plasma properties. This method is routinely used on Ulysses and Wind spacecrafts in the solar wind or in planetary magnetospheres/ionospheres (Ulysses at Jupiter, Cassini at Venus, Earth and soon at Saturn). This method has the advantage of being relatively immune to spacecraft potential and photoelectrons perturbations. These measurements will provide a fundamental input for the chemistry of cold ionized species (Na...) in Mercury's environment and for the dynamic modelling of the magnetosphere. Corresponding plasma frequencies are expected to be up to 200-300 kHz. Hence the QTN spectrum should be measured up to at least ~2 max(fpe) ~ 600 kHz. -Detection and study of Hermean radio emissions, including possible cyclotron emissions (up to ~10-20 kHz) from mildly energetic

  3. DEMONSTRATION BULLETIN: RADIO FREQUENCY HEATING - IIT RESEARCH INSTITUTE

    EPA Science Inventory

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

  4. Radio signature of magnetic reconnection and bi-directional shock waves in a flare-CME event on April 15, 1998

    NASA Astrophysics Data System (ADS)

    Huang, Guang-Li

    2003-03-01

    A flare-CME event on April 15, 1998 is studied with data of Nobeyama Radio Polarimeters (NoRP) and Heliograph (NoRH), the radio spectrometers of Chinese National Astronomical Observatories (1.0-2.0 GHz and 2.6-2.8 GHz), and the Astrophysical Institute of Postdam (200-800 MHz), as well as the data of YOHKOH, SOHO, BATSE, and GOES. There were strong fluctuations superposed on the initial phase of the BATSE hard X-ray burst, and the radio burst at 1.0-2.0 GHz with a group of type III-like positive and negative frequency drift pairs, which may be interpreted as the process of magnetic reconnection or particle acceleration in corona. A type II-like burst with a series of pulsations at 200-800 MHz followed the maximum phase of the radio and hard X-ray burst, and slowly drifted to lower frequencies with typical zebra feature. After 10 min of that, a similar dynamic spectrum was recorded at 2.6-3.8 GHz, where the type II-like signal drifted to higher frequencies with a series of pulsations and zebra structures. The polarization sense was strongly RCP at 2.6-3.8 GHz, and weakly LCP at 1.0-2.0 GHz, which was confirmed by the observations of NoRP. The radiation mechanism of these pulsations may be caused by the electron cyclotron maser instability. The local magnetic field strength and source height are estimated based on the gyro-synchrotron second harmonic emission. The ambient plasma density is calculated from the YOHKOH/SXT data. The ratio between the electron plasma frequency and gyro-frequency is around 1.3, which corresponds to the reversal value from extraordinary mode (LCP) to ordinary mode (RCP). Moreover, both the time scale and the modularity of an individual pulse increase statistically with the increase in the burst flux, which may be explained by the acceleration process of non-thermal electrons in the shock wave-fronts propagated upward and downward. Therefore, the radio observations may provide an important signature that flare and CME are triggered

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

    NASA Technical Reports Server (NTRS)

    Barrow, C. H.

    1979-01-01

    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.

  6. INSPIRE: A VLF Radio Project for High School Students

    ERIC Educational Resources Information Center

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

    2007-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2018-02-01

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

  8. Towards realization of quantitative atmospheric and industrial gas sensing using THz wave electronics

    NASA Astrophysics Data System (ADS)

    Tekawade, Aniket; Rice, Timothy E.; Oehlschlaeger, Matthew A.; Mansha, Muhammad Waleed; Wu, Kefei; Hella, Mona M.; Wilke, Ingrid

    2018-06-01

    The potential of THz wave electronics for miniaturized non-intrusive sensors for atmospheric, environmental, and industrial gases is explored. A THz wave spectrometer is developed using a radio-frequency multiplier source and a Schottky-diode detector. Spectral absorption measurements were made in a gas cell within a frequency range of 220-330 GHz at room temperature and subatmospheric pressures. Measurements are reported for pure acetonitrile (CH3CN), methanol (CH3OH), and ethanol (C2H5OH) vapors at 5 and 10 Torr and for methanol dilute in the air (0.75-3.0 mol%) at a pressure of 500 Torr. An absorbance noise floor of 10-3 was achieved for a single 10 s scan of the 220-330 GHz frequency domain. Measured absorption spectra for methanol/air agree well at collisional-broadened conditions with spectral simulations carried out using literature spectroscopic parameters. In contrast to the previous submillimeter wave research that has focused on spectral absorbance at extremely low pressures (mTorr), where transitions are in the Doppler limit, and the present study illustrates the applicability of THz electronics for gas sensing at pressures approaching those found in atmospheric and industrial environments.

  9. The Compact Radio Sources in the Nucleus of NGC 1068

    NASA Astrophysics Data System (ADS)

    Roy, A. L.; Colbert, E. J. M.; Wilson, A. S.; Ulvestad, J. S.

    1998-09-01

    We report VLBA images of the nucleus of the Seyfert galaxy NGC 1068 at 1.7, 5, and 15 GHz, with resolutions between 3 and 10 mas (0.2-0.7 pc) and a sensitivity of ~106 K at all three frequencies. Our goals are to study the morphology of the radio emission at subparsec resolution and to investigate thermal gas in the putative obscuring disk or torus and in the narrow-line region clouds through free-free absorption of the radio emission. All four known radio components in the central arcsecond (S2, S1, C, and NE, from south to north) have been detected at either 1.7 or 5 GHz, or both. No radio emission was detected at 15 GHz. Component S1 is probably associated with the active nucleus, with radio emission originating from the inner edge of the obscuring torus according to Gallimore et al. Our observed flux densities at 1.7 and 5 GHz are in agreement with their thermal bremsstrahlung emission model, and we find that the nuclear radiation may be strong enough to heat the gas in S1 to the required temperature of ~4 × 106 K. The bremsstrahlung power would be 0.15(frefl/0.01) times the bolometric luminosity of the nucleus between 1014.6 and 1018.4 Hz (where frefl is the fraction of radiation reflected into our line of sight by the electron-scattering mirror) and so the model is energetically reasonable. We also discuss two other models for S1 that also match the observed radio spectrum: electron scattering by the torus of radio emission from a compact synchrotron self-absorbed source and synchrotron radiation from the torus itself. Components NE and S2 have spectra consistent with optically thin synchrotron emission, without significant absorption. Both of these components are elongated roughly perpendicular to the larger scale radio jet, suggesting that their synchrotron emission is related to transverse shocks in the jet or to bow shocks in the external medium. Component C has a nonthermal spectrum absorbed at low frequency. This absorption is consistent with free

  10. Latest Observations of Interstellar Plasma Waves, Radio Emissions, and Dust Impacts from the Voyager 1 Plasma Wave Instrument

    NASA Astrophysics Data System (ADS)

    Gurnett, D. A.

    2017-12-01

    Voyager 1, which is now 140 AU (Astronomical Units) from the Sun, crossed the heliopause into interstellar space in 2012 at a heliospheric radial distance of 121 AU. Since crossing the heliopause the plasma wave instrument has on several occasions detected plasma oscillations and radio emissions at or near the electron plasma frequency. The most notable of these events occurred in Oct.-Nov. 2012, April-May 2013, Feb.-Nov. 2014, and Sept.-Nov. 2015. Most recently, a very weak emission has been observed at or near the electron plasma frequency through most of 2016. These emissions are all believed to be produced by shock waves propagating into the interstellar medium from energetic solar events. The oscillation frequency of the plasma indicates that the electron density in the interstellar plasma has gradually increased from about 0.06 cm-3 near the heliopause to about 0.12 cm-3 in the most recent data. The plasma wave instrument also continues to detect impacts of what are believed to be interstellar dust grains at an impact rate of a few per year. Comparisons with Ulysses observations of similar interstellar dust near 5 AU suggest that the dust grains have sizes in the range from about 0.1 to 1 micrometer. Although the statistics are poor due to the low count rate, the dust flux observed in the outer heliosphere appears to be as much as a factor of two greater than that observed in the interstellar medium. Since the dust particles are likely to be charged, this increase in the heliosphere suggests that there may be a significant electrodynamic interaction of the dust particles with the heliospheric magnetic field.

  11. Array analysis of electromagnetic radiation from radio transmitters for submarine communication

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  12. Spectral interferometric microscopy reveals absorption by individual optical nanoantennas from extinction phase

    PubMed Central

    Gennaro, Sylvain D.; Sonnefraud, Yannick; Verellen, Niels; Van Dorpe, Pol; Moshchalkov, Victor V.; Maier, Stefan A.; Oulton, Rupert F.

    2014-01-01

    Optical antennas transform light from freely propagating waves into highly localized excitations that interact strongly with matter. Unlike their radio frequency counterparts, optical antennas are nanoscopic and high frequency, making amplitude and phase measurements challenging and leaving some information hidden. Here we report a novel spectral interferometric microscopy technique to expose the amplitude and phase response of individual optical antennas across an octave of the visible to near-infrared spectrum. Although it is a far-field technique, we show that knowledge of the extinction phase allows quantitative estimation of nanoantenna absorption, which is a near-field quantity. To verify our method we characterize gold ring-disk dimers exhibiting Fano interference. Our results reveal that Fano interference only cancels a bright mode’s scattering, leaving residual extinction dominated by absorption. Spectral interference microscopy has the potential for real-time and single-shot phase and amplitude investigations of isolated quantum and classical antennas with applications across the physical and life sciences. PMID:24781663

  13. A Simple Radio Receiver Aids Understanding of Wireless Communication

    ERIC Educational Resources Information Center

    Straulino, S.; Orlando, A.

    2012-01-01

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

  14. Three-Stage InP Submillimeter-Wave MMIC Amplifier

    NASA Technical Reports Server (NTRS)

    Pukala, David; Samoska, Lorene; Man, King; Gaier, Todd; Deal, William; Lai, Richard; Mei, Gerry; Makishi, Stella

    2008-01-01

    A submillimeter-wave monolithic integrated- circuit (S-MMIC) amplifier has been designed and fabricated using an indium phosphide (InP) 35-nm gate-length high electron mobility transistor (HEMT) device, developed at Northrop Grumman Corporation. The HEMT device employs two fingers each 15 micrometers wide. The HEMT wafers are grown by molecular beam epitaxy (MBE) and make use of a pseudomorphic In0.75Ga0.25As channel, a silicon delta-doping layer as the electron supply, an In0.52Al0.48As buffer layer, and an InP substrate. The three-stage design uses coplanar waveguide topology with a very narrow ground-to-ground spacing of 14 micrometers. Quarter-wave matching transmission lines, on-chip metal-insulator-metal shunt capacitors, series thin-film resistors, and matching stubs were used in the design. Series resistors in the shunt branch arm provide the basic circuit stabilization. The S-MMIC amplifier was measured for S-parameters and found to be centered at 320 GHz with 13-15-dB gain from 300-345 GHz. This chip was developed as part of the DARPA Submillimeter Wave Imaging Focal Plane Technology (SWIFT) program (see figure). Submillimeter-wave amplifiers could enable more sensitive receivers for earth science, planetary remote sensing, and astrophysics telescopes, particularly in radio astronomy, both from the ground and in space. A small atmospheric window at 340 GHz exists and could enable ground-based observations. However, the submillimeter-wave regime (above 300 GHz) is best used for space telescopes as Earth s atmosphere attenuates most of the signal through water and oxygen absorption. Future radio telescopes could make use of S-MMIC amplifiers for wideband, low noise, instantaneous frequency coverage, particularly in the case of heterodyne array receivers.

  15. Project Radio JOVE: Hands-On Radio Astronomy for the Classroom

    NASA Astrophysics Data System (ADS)

    Thieman, J. R.; Higgins, C. A.

    2000-10-01

    Radio Jove is a relatively new educational project to involve secondary school students in collecting and analyzing observations of the natural radio emissions of the planet Jupiter and the Sun. Participating students get hands-on experience in gathering and working with space science data. They obtain the data by either building a radio receiver and antenna and making observations with their equipment, or by remotely using professional radio telescopes through the web. They can then compare their results with other schools who had also observed and come to conclusions concerning the nature of the radio sources and how the radio waves propagate to Earth. Thus, they fully follow the method of scientific inquiry used by radio astronomers to study our solar system. (National Science Content Standard A: Science as Inquiry) More than 200 kits have been distributed thus far to schools and individuals as a result of the project. With the coming Cassini flyby of Jupiter we will be advocating a campaign in which many of the schools involved in the project will be observing at times of scientific interest. While Galileo and Cassini are monitoring Jovian radio emissions at lower frequencies, the schools will be observing at frequencies of 20.1 MHz (kit-based observations) or the frequencies available through the professional radio telescopes connected on-line. The aim will be to get a thorough picture of the levels of activity at Jupiter during the flyby period and how the radio signals are received at different observing stations around the world. An archive of observations submitted by the schools will be maintained at Goddard Space Flight Center and there will also be an archive of the professional telescopes data at the University of Florida. We hope that many students will have the feeling of being a part of the planetary exploration program as a result.

  16. Application of temperature-dependent fluorescent dyes to the measurement of millimeter wave absorption in water applied to biomedical experiments.

    PubMed

    Kuzkova, Nataliia; Popenko, Oleksandr; Yakunov, Andrey

    2014-01-01

    Temperature sensitivity of the fluorescence intensity of the organic dyes solutions was used for noncontact measurement of the electromagnetic millimeter wave absorption in water. By using two different dyes with opposite temperature effects, local temperature increase in the capillary that is placed inside a rectangular waveguide in which millimeter waves propagate was defined. The application of this noncontact temperature sensing is a simple and novel method to detect temperature change in small biological objects.

  17. Ionospheric Radio Propagation

    DTIC Science & Technology

    1948-06-25

    fluctuation According to this method the noise figure of a radio noise, generated either in the receiving sys - receiver is a quotient of the ratio of available...Ibmaity @" nabe ) adal 38. So"&UJ Malabo u~aIS. 5 a"), il61 Sudde io o ,disturbances (OLD). 6; absorption elects. 111. &e d"a hashed ~ ~ ~ ~ ~~( Saim. kuiy1

  18. The Infrared-Radio Correlation of Dusty Star Forming Galaxies at High Redshift

    NASA Astrophysics Data System (ADS)

    Lower, Sidney; Vieira, Joaquin Daniel; Jarugula, Sreevani

    2018-01-01

    Far-infrared (FIR) and radio continuum emission in galaxies are related by a common origin: massive stars and the processes triggered during their birth, lifetime, and death. FIR emission is produced by cool dust, heated by the absorption of UV emission from massive stars, which is then re-emitted in the FIR. Thermal free-free radiation emitted from HII regions dominates the spectral energy density (SED) of galaxies at roughly 30 GHz, while non-thermal synchrotron radiation dominates at lower frequencies. At low redshift, the infrared radio correlation (IRC, or qIR) holds as a tight empirical relation for many star forming galaxy types, but until recently, there has not been sensitive enough radio observations to extend this relation to higher redshifts. Many selection biases cloud the results of these analyses, leaving the evolution of the IRC with redshift ambiguous. In this poster, I present CIGALE fitted spectral energy distributions (SEDs) for 24 gravitationally-lensed sources selected in the mm-wave from the South Pole Telescope (SPT) survey. I fit the IRC from infrared and submillimeter fluxes obtained with Herschel, Atacama Pathfinder Experiment (APEX), and SPT and radio fluxes obtained with ATCA at 2.1, 5.5, 9, and 30 GHz. This sample of SPT sources has a spectroscopic redshift range of 2.1

  19. Traveling-wave photodetector

    DOEpatents

    Hietala, V.M.; Vawter, G.A.

    1993-12-14

    The traveling-wave photodetector of the present invention combines an absorptive optical waveguide and an electrical transmission line, in which optical absorption in the waveguide results in a photocurrent at the electrodes of the electrical transmission line. The optical waveguide and electrical transmission line of the electrically distributed traveling-wave photodetector are designed to achieve matched velocities between the light in the optical waveguide and electrical signal generated on the transmission line. This velocity synchronization provides the traveling-wave photodetector with a large electrical bandwidth and a high quantum efficiency, because of the effective extended volume for optical absorption. The traveling-wave photodetector also provides large power dissipation, because of its large physical size. 4 figures.

  20. Traveling-wave photodetector

    DOEpatents

    Hietala, Vincent M.; Vawter, Gregory A.

    1993-01-01

    The traveling-wave photodetector of the present invention combines an absorptive optical waveguide and an electrical transmission line, in which optical absorption in the waveguide results in a photocurrent at the electrodes of the electrical transmission line. The optical waveguide and electrical transmission line of the electrically distributed traveling-wave photodetector are designed to achieve matched velocities between the light in the optical waveguide and electrical signal generated on the transmission line. This velocity synchronization provides the traveling-wave photodetector with a large electrical bandwidth and a high quantum efficiency, because of the effective extended volume for optical absorption. The traveling-wave photodetector also provides large power dissipation, because of its large physical size.

  1. Need a Classroom Stimulus? Introduce Radio Astronomy

    ERIC Educational Resources Information Center

    Derman, Samuel

    2010-01-01

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

  2. Wideband spectrum analysis of ultra-high frequency radio-wave signals due to advanced one-phonon non-collinear anomalous light scattering.

    PubMed

    Shcherbakov, Alexandre S; Arellanes, Adan Omar

    2017-04-20

    We present a principally new acousto-optical cell providing an advanced wideband spectrum analysis of ultra-high frequency radio-wave signals. For the first time, we apply a recently developed approach with the tilt angle to a one-phonon non-collinear anomalous light scattering. In contrast to earlier cases, now one can exploit a regime with the fixed optical wavelength for processing a great number of acoustic frequencies simultaneously in the linear regime. The chosen rutile-crystal combines a moderate acoustic velocity with low acoustic attenuation and allows us wide-band data processing within GHz-frequency acoustic waves. We have created and experimentally tested a 6-cm aperture rutile-made acousto-optical cell providing the central frequency 2.0 GHz, frequency bandwidth ∼0.52  GHz with the frequency resolution about 68.3 kHz, and ∼7620 resolvable spots. A similar cell permits designing an advanced ultra-high-frequency arm within a recently developed multi-band radio-wave acousto-optical spectrometer for astrophysical studies. This spectrometer is intended to operate with a few parallel optical arms for processing the multi-frequency data flows within astrophysical observations. Keeping all the instrument's advantages of the previous schematic arrangement, now one can create the highest-frequency arm using the developed rutile-based acousto-optical cell. It permits optimizing the performances inherent in that arm via regulation of both the central frequency and the frequency bandwidth for spectrum analysis.

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

    ERIC Educational Resources Information Center

    Freeman, J. C.

    1986-01-01

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

  4. World War II Radar and Early Radio Astronomy

    NASA Astrophysics Data System (ADS)

    Smith, G.

    2005-08-01

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

  5. Evanescent wave sensing and absorption analysis of herbal tea floral extracts in the presence of silver metal complexes

    NASA Astrophysics Data System (ADS)

    Priyamvada, V. C.; Radhakrishnan, P.

    2017-06-01

    Fiber optic evanescent wave sensors are used for studying the absorption properties of biochemical samples. The studies give precise information regarding the actual ingredients of the samples. Recent studies report the corrosion of silver in the presence glucose dissolved in water and heated to a temperature of 70°C. Based on this report evanescent absorption studies are carried out in hibiscus herbal tea floral extracts in the presence of silver metal complexes. These studies can also lead to the evaluation of the purity of the herbal tea extract.

  6. Selective coherent perfect absorption in metamaterials

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

    Nie, Guangyu; Shi, Quanchao; Zhu, Zheng

    2014-11-17

    We show multi-band coherent perfect absorption (CPA) in simple bilayered asymmetrically split ring metamaterials. The selectivity of absorption can be accomplished by separately excited electric and magnetic modes in a standing wave formed by two coherent counterpropagating beams. In particular, each CPA can be completely switched on/off by the phase of a second coherent wave. We propose a practical scheme for realizing multi-band coherent perfect absorption of 100% that is allowed to work from microwave to optical frequency.

  7. Al 1s-2p Absorption Spectroscopy of Shock-Wave Heating and Compression in Laser-Driven Planar Foil

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

    Sawada, H.; Regan, S.P.; Radha, P.B.

    Time-resolved Al 1s-2p absorption spectroscopy is used to diagnose direct-drive, shock-wave heating and compression of planar targets having nearly Fermi-degenerate plasma conditions (Te ~ 10–40 eV, rho ~ 3–11 g/cm^3) on the OMEGA Laser System [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. A planar plastic foil with a buried Al tracer layer was irradiated with peak intensities of 10^14–10^15 W/cm^2 and probed with the pseudocontinuum M-band emission from a point-source Sm backlighter in the range of 1.4–1.7 keV. The laser ablation process launches 10–70 Mbar shock waves into the CH/Al/CH target. The Al 1s-2p absorption spectra weremore » analyzed using the atomic physic code PRISMSPECT to infer Te and rho in the Al layer, assuming uniform plasma conditions during shock-wave heating, and to determine when the heat front penetrated the Al layer. The drive foils were simulated with the one-dimensional hydrodynamics code LILAC using a flux-limited (f =0.06 and f =0.1) and nonlocal thermal-transport model [V. N. Goncharov et al., Phys. Plasmas 13, 012702 (2006)]. The predictions of simulated shock-wave heating and the timing of heat-front penetration are compared to the observations. The experimental results for a wide variety of laser-drive conditions and buried depths have shown that the LILAC predictions using f = 0.06 and the nonlocal model accurately model the shock-wave heating and timing of the heat-front penetration while the shock is transiting the target. The observed discrepancy between the measured and simulated shock-wave heating at late times of the drive can be explained by the reduced radiative heating due to lateral heat flow in the corona.« less

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

    NASA Technical Reports Server (NTRS)

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

    2016-01-01

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

  9. Application of Temperature-Dependent Fluorescent Dyes to the Measurement of Millimeter Wave Absorption in Water Applied to Biomedical Experiments

    PubMed Central

    Popenko, Oleksandr

    2014-01-01

    Temperature sensitivity of the fluorescence intensity of the organic dyes solutions was used for noncontact measurement of the electromagnetic millimeter wave absorption in water. By using two different dyes with opposite temperature effects, local temperature increase in the capillary that is placed inside a rectangular waveguide in which millimeter waves propagate was defined. The application of this noncontact temperature sensing is a simple and novel method to detect temperature change in small biological objects. PMID:25435859

  10. The physical basis for absorption of light. [effects on wave functions of gas molecules and atoms

    NASA Technical Reports Server (NTRS)

    Pickett, H. M.

    1979-01-01

    The effects of light absorption on the wave functions of gas-phase molecules and atoms are investigated by high resolution spectral measurements of radiation emerging from a sample. A Stark-modulated sample of methyl fluoride was irradiated at the 102 GHz rotational transition and the emergent radiation was resolved by means of a spectrum analyzer. For signal oscillator frequencies below or above the molecular resonance by one modulation frequency, the amplitudes of the upper and lower modulation sidebands are found to be of nonuniform intensity, which is inconsistent with amplitude modulation. Emission due to polarization is, however, calculated to be consistent with the results observed, indicating that light absorption should be considered as a subtractive stimulated emission.

  11. Astronomers Win Protection for Key Part of Radio Spectrum

    NASA Astrophysics Data System (ADS)

    2000-06-01

    Astronomers using the millimeter-wave region of the radio spectrum have won crucial protection for their science. Dedicated allocations for radio astronomy have been given final approval by the 2,500 delegates to the World Radiocommunication Conference (WRC-00), which recently concluded a month of deliberations in Istanbul, Turkey. Radio services can transmit in these parts of the spectrum as long as they don't hinder astronomers' attempts to catch faint signals from the cosmos. The new allocations represent the culmination of more than three years of cooperative planning by radio astronomers in many countries. Millimeter waves -- high-frequency radio waves -- have come of age as an astronomical tool in the last ten years. They are one of the last technological frontiers for astronomers. WRC-00 has protected for science all the frequencies between 71 and 275 Gigahertz (GHz) that radio astronomers currently use, adding more than 90 GHz of spectrum to the 44 GHz already set aside in this frequency range. As a result, radio astronomy is now allocated most of the frequencies between 71 and 275 GHz that can get through the Earth's atmosphere. "We have formal access to all three atmospheric 'windows', apart from their very edges," said Dr. Tom Gergely of the National Science Foundation, one of the U.S. delegates to WRC-00. The WRC also changed most of the frequencies allocated to satellite downlinks within the 71-275 GHz range to frequencies not used for science. Since no satellites yet operate at these high frequencies, no equipment needs to be altered. "Commercial technologies are just starting to develop above 50 GHz," said Dr. Klaus Ruf, Chairman of the Inter-Union Commission for the Allocation of Frequencies. "The WRC's actions mean that, when they are, radio astronomers should be able to share this part of the spectrum with most terrestrial services." The World Radiocommunication Conference is held every two or three years. Here member countries of the

  12. Parametric Investigation of Holographic Gratings and Optical Phase Conjugation Through Degenerate Four Wave Mixing in Saturable Absorptive/Resonant/Nonresonant Systems

    DTIC Science & Technology

    1991-11-26

    WAVE MIXING IN SATURABLE ABSORPTIVEIRESONANTINONRESONANT SYSTEMS I Final Report Putcha Venkateswarlu November 26, 1991 U.S. ARMY RESEARCH OFFICE GRANT...and Optical Phase Conjugation Through Degenerate Four Wave Mixin2 in Saturable Absorptive/Resonant/Nonresonant System DAAL03-87-G-0078 6. AUTHOR(S) P...author(s) and should not be construed as an official Department of the Army position, policy, or decision, unless so designated by other

  13. ULF radio monitoring network in a seismic area

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

    ULF monitoring is a part of a multidisciplinary network (AeroSolSys) located in Vrancea (Curvature Carpathian Mountains). Four radio receivers (100 kHz - microwave) placed on faults in a high seismic area characterized by deep earthquakes detect fairly weak radio waves. The radio power is recorded in correlation with many other parameters related to near surface low atmosphere phenomena (seismicity, solar radiation, air ionization, electromagnetic activity, radon, CO2 concentration, atmospheric pressure, telluric currents, infrasound, seismo-acoustic emission, meteorological information). We follow variations in the earth's surface propagate radio waves avoiding reflection on ionosphere. For this reason the distance between stations is less than 60 km and the main source of emission is near (Bod broadcasting transmitter for long- and medium-wave radio, next to Brasov city). In the same time tectonic stress affects the radio propagation in air and it could generates ULF waves in ground (LAI coupling). To reduce the uncertainty is necessary to monitor a location for extended periods of time to outline local and seasonal fluctuations. Solar flares do not affect seismic activity but they produce disturbances in telecommunications networks and power grids. Our ULF monitoring correlated with two local magnetometers does not indicate this so far with our receivers. Our analysis was made during magnetic storms with Kp 7 and 8 according to NOAA satellites. To correlate the results we implemented an application that monitors the satellite EUTELSAT latency compared to WiMAX land communication in the same place. ULF band radio monitoring showed that our receiver is dependent on temperature and that it is necessary to introduce a band pass filter in data analysis. ULF data acquisition is performed by Kinemetrics and National Instruments digitizers with a sampling rate of 100 Hz in Miniseed format and then converted into text files with 1 Hz rate for analysis in very low

  14. 140 GHz EC waves propagation and absorption for normal/oblique injection on FTU tokamak

    NASA Astrophysics Data System (ADS)

    Nowak, S.; Airoldi, A.; Bruschi, A.; Buratti, P.; Cirant, S.; Gandini, F.; Granucci, G.; Lazzaro, E.; Panaccione, L.; Ramponi, G.; Simonetto, A.; Sozzi, C.; Tudisco, O.; Zerbini, M.

    1999-09-01

    Most of the interest in ECRH experiments is linked to the high localization of EC waves absorption in well known portions of the plasma volume. In order to take full advantage of this capability a reliable code has been developed for beam tracing and absorption calculations. The code is particularly important for oblique (poloidal and toroidal) injection, when the absorbing layer is not simply dependent on the position of the EC resonance only. An experimental estimate of the local heating power density is given by the jump in the time derivative of the local electron pressure at the switching ON of the gyrotron power. The evolution of the temperature profile increase (from ECE polychromator) during the nearly adiabatic phase is also considered for ECRH profile reconstruction. An indirect estimate of optical thickness and of the overall absorption coefficient is given by the measure of the residual e.m. power at the tokamak walls. Beam tracing code predictions of the power deposition profile are compared with experimental estimates. The impact of the finite spatial resolution of the temperature diagnostic on profile reconstruction is also discussed.

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

    NASA Technical Reports Server (NTRS)

    Dean, Bruce H. (Inventor)

    2013-01-01

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

  16. Layered Structures and Internal Waves in the Ionosphere and Atmosphere as Seen from GPS Occultation Data

    NASA Astrophysics Data System (ADS)

    Pavelyev, Alexander; Pavelyev, Alexander; Gubenko, Vladimir; Wickert, Jens; Liou, Yuei An

    High-precision signals emitted by GPS satellites create favourable conditions both for monitoring of the atmosphere and ionosphere and for investigation of the radio wave propagation effects. Comparative theoretical and experimental analysis of the phase and amplitude variations of the GPS radio-holograms discovered a relationship which relates the refraction attenuation, the phase path excess acceleration and Doppler frequency via a classical dynamics equationtype. The advantages of the introduced relationship consist in: (1) a possibility to separate the layered structure and turbulence contributions to RO signal; (2) a possibility to estimate the absorption in the atmosphere by dividing the refraction attenuations found from amplitude and phase data; (3) a possibility to locate the tangent point in the atmosphere with accuracy in the distance from the standard position of of about ±100 km. The suggested method has a general importance because it may be applied for analysis in the trans-ionospheric satellite-to-Earth links. We showed also that the amplitude variations of GPS occultation signals are very sensitive sensors to the internal waves in the atmosphere. The sensitivity of the amplitude method is inversely proportional to the square of the vertical period of the internal wave, indicating high sensitivity of the amplitude data to the wave structures with small vertical periods in the 0.8-4 km interval. Combined analysis of the amplitude and phase of radio occultation signal allows one to determine with high level of reliability the main characteristics of the atmospheric and ionospheric layeres including the vertical distribution of the refractivity, electron density and their gradients. A possibility exists to measure important parameters of the internal waves: the intrinsic phase speed, the horizontal wind perturbations and, under some assumptions, the intrinsic frequency as functions of height in the atmosphere. A new technique has been applied to

  17. Amateur Planetary Radio Data Archived for Science and Education: Radio Jove

    NASA Astrophysics Data System (ADS)

    Thieman, J.; Cecconi, B.; Sky, J.; Garcia, L. N.; King, T. A.; Higgins, C. A.; Fung, S. F.

    2015-12-01

    The Radio Jove Project is a hands-on educational activity in which students, teachers, and the general public build simple radio telescopes, usually from a kit, to observe single frequency decameter wavelength radio emissions from Jupiter, the Sun, the galaxy, and the Earth usually with simple dipole antennas. Some of the amateur observers have upgraded their receivers to spectrographs and their antennas have become more sophisticated as well. The data records compare favorably to more sophisticated professional radio telescopes such as the Long Wavelength Array (LWA) and the Nancay Decametric Array. Since these data are often carefully calibrated and recorded around the clock in widely scattered locations they represent a valuable database useful not only to amateur radio astronomers but to the professional science community as well. Some interesting phenomena have been noted in the data that are of interest to the professionals familiar with such records. The continuous monitoring of radio emissions from Jupiter could serve as useful "ground truth" data during the coming Juno mission's radio observations of Jupiter. Radio Jove has long maintained an archive for thousands of Radio Jove observations, but the database was intended for use by the Radio Jove participants only. Now, increased scientific interest in the use of these data has resulted in several proposals to translate the data into a science community data format standard and store the data in professional archives. Progress is being made in translating Radio Jove data to the Common Data Format (CDF) and also in generating new observations in that format as well. Metadata describing the Radio Jove data would follow the Space Physics Archive Search and Extract (SPASE) standard. The proposed archive to be used for long term preservation would be the Planetary Data System (PDS). Data sharing would be achieved through the PDS and the Paris Astronomical Data Centre (PADC) and the Virtual Wave Observatory (VWO

  18. MEASUREMENTS OF THE ABSORPTION AND SCATTERING CROSS SECTIONS FOR THE INTERACTION OF SOLAR ACOUSTIC WAVES WITH SUNSPOTS

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

    Zhao, Hui; Chou, Dean-Yi, E-mail: chou@phys.nthu.edu.tw

    The solar acoustic waves are modified by the interaction with sunspots. The interaction can be treated as a scattering problem: an incident wave propagating toward a sunspot is scattered by the sunspot into different modes. The absorption cross section and scattering cross section are two important parameters in the scattering problem. In this study, we use the wavefunction of the scattered wave, measured with a deconvolution method, to compute the absorption cross section σ {sub ab} and the scattering cross section σ {sub sc} for the radial order n = 0–5 for two sunspots, NOAA 11084 and NOAA 11092. Inmore » the computation of the cross sections, the random noise and dissipation in the measured acoustic power are corrected. For both σ {sub ab} and σ {sub sc}, the value of NOAA 11092 is greater than that of NOAA 11084, but their overall n dependence is similar: decreasing with n . The ratio of σ {sub ab} of NOAA 11092 to that of NOAA 11084 approximately equals the ratio of sunspot radii for all n , while the ratio of σ {sub sc} of the two sunspots is greater than the ratio of sunspot radii and increases with n . This suggests that σ {sub ab} is approximately proportional to the sunspot radius, while the dependence of σ {sub sc} on radius is faster than the linear increase.« less

  19. Radio Frequency Interference: Radio Astronomy's Biggest Enemy

    NASA Astrophysics Data System (ADS)

    Acevedo, F.; Ghosh, Tapasi

    1997-12-01

    As technology progresses, the demand for the usage of the electromagnetic spectrum increases with it. The development is so fast and prolific that clean band space for passive users such as Radio Astronomy is becoming ever so scarce. Even though, several spectral bands have been protected for Radio Astronomy by Federal Communication Commission (in the USA) under the recommendations of the International Telecommunication Union (ITU), pressure for making more spectral space commercially usable is extreme. Although these commercial usages make our modern living at all possible, often the extreme vulnerability of passive users are are not fully appreciated, resulting in unwanted emissions (RFI) in the Radio Astronomy Bands. Another source of RFI is the fact that many of the electronic devices used in the observatories themselves generate radio waves. If proper precautions are not taken, these can be received back through the Radio Telescope itself. This problem is referred to as internal RFI. The focus of this paper is the search and diminution of internal RFI in the Arecibo Observatory in Arecibo, Puerto Rico. Using a simple setup of a log-periodic antenna and a Spectrum Analyzer, spectra spanning a frequency range of 100 - 1800 MHZ were recorded in some areas of the Observatory and the new Visitor Center (AOVEF). The measurements disclosed sources of radio emission among some of the digital electronic equipment in the Equipment room and a few displays in the AOVEF. Most prominent of these was a 2.5 MHz comb spanning the entire range of the measurements emitted from the SRENDIP and AOFTM machines. The respective groups were informed and corrective shielding & isolations were implemented immediately. In AOVEF, three displays, some audio-visual equipment, and video/digital cameras used by the visitors were found to be "leaky". In future, the use of such cameras will be prohibited and the exhibits will be screened appropriately.

  20. Radio polarisation measurements of meteor trail echoes with BRAMS

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  1. Free-Free Absorption on Parsec Scales in Seyfert Galaxies

    NASA Astrophysics Data System (ADS)

    Roy, A. L.; Ulvestad, J. S.; Wilson, A. S.; Colbert, E. J. M.; Mundell, C. G.; Wrobel, J. M.; Norris, R. P.; Falcke, H.; Krichbaum, T.

    Seyfert galaxies come in two main types (types 1 and 2) and the difference is probably due to obscuration of the nucleus by a torus of dense molecular material. The inner edge of the torus is expected to be ionized by optical and ultraviolet emission from the active nucleus, and will radiate direct thermal emission (e.g. NGC 1068) and will cause free-free absorption of nuclear radio components viewed through the torus (e.g. Mrk 231, Mrk 348, NGC 2639). However, the nuclear radio sources in Seyfert galaxies are weak compared to radio galaxies and quasars, demanding high sensitivity to study these effects. We have been making sensitive phase referenced VLBI observations at wavelengths between 21 and 2 cm where the free-free turnover is expected, looking for parsec-scale absorption and emission. We find that free-free absorption is common (e.g. in Mrk 348, Mrk 231, NGC 2639, NGC 1068) although compact jets are still visible, and the inferred density of the absorber agrees with the absorption columns inferred from X-ray spectra (Mrk 231, Mrk 348, NGC 2639). We find one-sided parsec-scale jets in Mrk 348 and Mrk 231, and we measure low jet speeds (typically £ 0.1 c). The one-sidedness probably is not due to Doppler boosting, but rather is probably free-free absorption. Plasma density required to produce the absorption is Ne 3 2 105 cm-3 assuming a path length of 0.1 pc, typical of that expected at the inner edge of the obscuring torus.

  2. Air shower measurements with the LOPES radio antenna array

    NASA Astrophysics Data System (ADS)

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

    2009-06-01

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

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

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    1991-01-01

    Laboratory measurements of microwave and millimeter wave properties of the simulated atmosphere of the outer planets and their satellites has continued. One of the focuses is on the development of a radiative transfer model of the Jovian atmosphere at wavelengths from 1 mm to 10 cm. This modeling effort led to laboratory measurements of the millimeter wave opacity of hydrogen sulfide (H2S) under simulated Jovian conditions. Descriptions of the modeling effort, the Laboratory experiment, and the observations are presented. Correlative studies of measurements with Pioneer-Venus radio occultation measurements with longer wavelength emission measurements have provided new ways for characterizing temporal and spatial variations in the abundance of both gases H2SO4 and SO2, and for modeling their roles in the subcloud atmosphere. Laboratory measurements were conducted on 1.35 cm (and 13 cm) opacity of gaseous SO2 and absorptivity of gaseous SO2 at the 3.2 mm wavelength under simulated Venus conditions. Laboratory measurements were completed on millimeter wave dielectric properties of liquid H2SO4, in order to model the effects of the opacity of the clouds of Venus onto millimeter wave emission spectrum.

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

    NASA Astrophysics Data System (ADS)

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

    2018-06-01

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

  5. The radio sources CTA 21 and OF+247: The hot spots of radio galaxies

    NASA Astrophysics Data System (ADS)

    Artyukh, V. S.; Tyul'bashev, S. A.; Chernikov, P. A.

    2013-06-01

    The physical conditions in the radio sources CTA 21 and OF+247 are studied assuming that the low-frequency spectral turnovers are due to synchrotron self-absorption. The physical parameters of the radio sources are estimated using a technique based on a nonuniform synchrotron source model. It is shown that the magnetic-field distributions in the dominant compact components of these radio sources are strongly inhomogeneous. The magnetic fields at the center of the sources are B ˜ 10-1 G, and the fields are two to three orders of magnitude weaker at the periphery. The magnetic field averaged over the compact component is B ˜ 10-3 G, and the density of relativistic electrons is n e ˜ 10-3 cm-3. Assuming that there is equipartition of the energies of the magnetic field and relativistic particles, averaged over the source, < E H > = < E e > ˜ 10-7-10-6 erg cm-3. The energy density of the magnetic field exceeds that of the relativistic electrons at the centers of the radio sources. The derived parameters of CTA 21 and OF+247 are close to those of the hot spots in the radio galaxy Cygnus A. On this basis, it is suggested that CTA 21 and OF+247 are radio galaxies at an early stage of their evolution, when the hot spots (dominant compact radio components) have appeared, and the radio lobes (weak extended components) are still being formed.

  6. Zero-Power Radio Device.

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

    Brocato, Robert W.

    This report describes an unpowered radio receiver capable of detecting and responding to weak signals transmit ted from comparatively long distances . This radio receiver offers key advantages over a short range zero - power radio receiver previously described in SAND2004 - 4610, A Zero - Power Radio Receiver . The device described here can be fabricated as an integrated circuit for use in portable wireless devices, as a wake - up circuit, or a s a stand - alone receiver operating in conjunction with identification decoders or other electroni cs. It builds on key sub - components developed atmore » Sandia National Laboratories over many years. It uses surface acoustic wave (SAW) filter technology. It uses custom component design to enable the efficient use of small aperture antennas. This device uses a key component, the pyroelectric demodulator , covered by Sandia owned U.S. Patent 7397301, Pyroelectric Demodulating Detector [1] . This device is also described in Sandia owned U.S. Patent 97266446, Zero Power Receiver [2].« less

  7. Peering through Jupiter’s clouds with radio spectral imaging

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  8. Wide Field Radio Transient Surveys

    NASA Astrophysics Data System (ADS)

    Bower, Geoffrey

    2011-04-01

    The time domain of the radio wavelength sky has been only sparsely explored. Nevertheless, serendipitous discovery and results from limited surveys indicate that there is much to be found on timescales from nanoseconds to years and at wavelengths from meters to millimeters. These observations have revealed unexpected phenomena such as rotating radio transients and coherent pulses from brown dwarfs. Additionally, archival studies have revealed an unknown class of radio transients without radio, optical, or high-energy hosts. The new generation of centimeter-wave radio telescopes such as the Allen Telescope Array (ATA) will exploit wide fields of view and flexible digital signal processing to systematically explore radio transient parameter space, as well as lay the scientific and technical foundation for the Square Kilometer Array. Known unknowns that will be the target of future transient surveys include orphan gamma-ray burst afterglows, radio supernovae, tidally-disrupted stars, flare stars, and magnetars. While probing the variable sky, these surveys will also provide unprecedented information on the static radio sky. I will present results from three large ATA surveys (the Fly's Eye survey, the ATA Twenty CM Survey (ATATS), and the Pi GHz Survey (PiGSS)) and several small ATA transient searches. Finally, I will discuss the landscape and opportunities for future instruments at centimeter wavelengths.

  9. A Millimeter-Wave Digital Link for Wireless MRI

    PubMed Central

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

    2017-01-01

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

  10. A Millimeter-Wave Digital Link for Wireless MRI.

    PubMed

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

    2017-02-01

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

  11. Spectral Energy Distribution and Radio Halo of NGC 253 at Low Radio Frequencies

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

    Kapińska, A. D.; Staveley-Smith, L.; Meurer, G. R.

    We present new radio continuum observations of NGC 253 from the Murchison Widefield Array at frequencies between 76 and 227 MHz. We model the broadband radio spectral energy distribution for the total flux density of NGC 253 between 76 MHz and 11 GHz. The spectrum is best described as a sum of a central starburst and extended emission. The central component, corresponding to the inner 500 pc of the starburst region of the galaxy, is best modeled as an internally free–free absorbed synchrotron plasma, with a turnover frequency around 230 MHz. The extended emission component of the spectrum of NGCmore » 253 is best described as a synchrotron emission flattening at low radio frequencies. We find that 34% of the extended emission (outside the central starburst region) at 1 GHz becomes partially absorbed at low radio frequencies. Most of this flattening occurs in the western region of the southeast halo, and may be indicative of synchrotron self-absorption of shock-reaccelerated electrons or an intrinsic low-energy cutoff of the electron distribution. Furthermore, we detect the large-scale synchrotron radio halo of NGC 253 in our radio images. At 154–231 MHz the halo displays the well known X-shaped/horn-like structure, and extends out to ∼8 kpc in the z -direction (from the major axis).« less

  12. 47 CFR 32.2231 - Radio systems.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

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

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

    NASA Technical Reports Server (NTRS)

    Scudder, Jack D.

    1992-01-01

    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.

  15. Overview of Solar Radio Bursts and their Sources

    NASA Astrophysics Data System (ADS)

    Golla, Thejappa; MacDowall, Robert J.

    2018-06-01

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

  16. Harmonization based on regulatory science between scientific and commercial radio uses in a case of ultrawideband radio

    NASA Astrophysics Data System (ADS)

    Kohno, Ryuji; Iinatti, Jari; Sameshima, Keiko

    2016-12-01

    Harmonization for scientific and commercial radio uses is one of the unsolved problems in academia, industry, and regulatory bodies. The demands for commercial radio, mobile communications, and broadcasting have significantly increased over the past few decades; therefore, interference has become a major concern. There is an increasing need to prevent such interferences, for example, between commercial radio systems and other potentially sensitive radio systems such as those used for radio astronomy or studies. When discussing the fairness in resolving such conflicts, regulatory science may be a useful multidisciplinary approach as it scientifically investigates the advantages and disadvantages of a new application or technology for conflicts between different stakeholders through a mathematical analysis of risks versus benefits of the given technology. Such an analysis enables fair rules or regulations to be made. In this study, we apply the above-mentioned concept to harmonize the scientific and commercial uses of radio. After a brief introduction to regulatory science, a case study about the coexistence between ultrawideband commercial radio systems and radio astronomy is considered. Finally, a proposal by International Union of Radio Science, Japan, to the Science Council of Japan in the Cabinet Office to establish a "Center for Coexistence and Harmonization of Scientific and Commercial Uses of Radio Waves" is explained.

  17. Full PIC simulations of solar radio emission

    NASA Astrophysics Data System (ADS)

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

    2017-12-01

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

  18. Radio-over-fiber system with octuple frequency optical millimeter-wave signal generation using dual-parallel Mach-Zehnder modulator based on four-wave mixing in semiconductor optical amplifier

    NASA Astrophysics Data System (ADS)

    Zhou, Hui; Zeng, Yuting; Chen, Ming; Shen, Yunlong

    2018-03-01

    We have proposed a scheme of radio-over-fiber (RoF) system employing a dual-parallel Mach-Zehnder modulator (DP-MZM) based on four-wave mixing (FWM) in a semiconductor optical amplifier (SOA). In this scheme, the pump and the signal are generated by properly adjusting the direct current bias, modulation index of the DP-MZM, and the phase difference between the sub-MZMs. Because of the pump and the signal deriving from the same optical wave, the polarization states of the two lightwaves are copolarized. The single-pump FWM is polarization insensitive. After FWM and optical filtering, the optical millimeter-wave with octuple frequency is generated. About 40-GHz RoF system with a 2.5-Gbit / s signal is implemented by numerical simulation; the result shows that it has a good performance after the signal is transmitted over 40-km single-mode fiber. Then, the effects of the SOA's injection current and the carrier-to-sideband ratio on the system performance are discussed by simulation, and the optimum value for the system is obtained.

  19. Balancing Power Absorption and Structural Loading for an Asymmetric Heave Wave-Energy Converter in Regular Waves

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

    Tom, Nathan M.; Madhi, Farshad; Yeung, Ronald W.

    2016-06-24

    The aim of this paper is to maximize the power-to-load ratio of the Berkeley Wedge: a one-degree-of-freedom, asymmetrical, energy-capturing, floating breakwater of high performance that is relatively free of viscosity effects. Linear hydrodynamic theory was used to calculate bounds on the expected time-averaged power (TAP) and corresponding surge restraining force, pitch restraining torque, and power take-off (PTO) control force when assuming that the heave motion of the wave energy converter remains sinusoidal. This particular device was documented to be an almost-perfect absorber if one-degree-of-freedom motion is maintained. The success of such or similar future wave energy converter technologies would requiremore » the development of control strategies that can adapt device performance to maximize energy generation in operational conditions while mitigating hydrodynamic loads in extreme waves to reduce the structural mass and overall cost. This paper formulates the optimal control problem to incorporate metrics that provide a measure of the surge restraining force, pitch restraining torque, and PTO control force. The optimizer must now handle an objective function with competing terms in an attempt to maximize power capture while minimizing structural and actuator loads. A penalty weight is placed on the surge restraining force, pitch restraining torque, and PTO actuation force, thereby allowing the control focus to be placed either on power absorption or load mitigation. Thus, in achieving these goals, a per-unit gain in TAP would not lead to a greater per-unit demand in structural strength, hence yielding a favorable benefit-to-cost ratio. Demonstrative results in the form of TAP, reactive TAP, and the amplitudes of the surge restraining force, pitch restraining torque, and PTO control force are shown for the Berkeley Wedge example.« less

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

    NASA Technical Reports Server (NTRS)

    Steffes, P. G.

    1985-01-01

    Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments and Earth-based radio astronomical observations can be used to infer abundances of microwave absorbing atmospheric constituents in those atmospheres, as long as reliable information regarding the microwave absorbing properties of potential constituents is available. The use of theoretically-derived microwave absorption properties for such atmospheric constituents, or laboratory measurements of such properties under environmental conditions which are significantly different than those of the planetary atmosphere being studied, often lead to significant misinterpretation of available opacity data. Steffes and Eshleman showed that under environmental conditions corresponding to the middle atmosphere of Venus, the microwave absorption due to atmospheric SO2 was 50 percent greater than that calculated from Van Vleck-Weiskopff theory. Similarly, the opacity from gaseous H2SO4 was found to be a factor of 7 greater than theoretically predicted for conditions of the Venus middle atmosphere. The recognition of the need to make such measurements over a range of temperatures and pressures which correspond to the periapsis altitudes of radio occultation experiments, and over a range of frequencies which correspond to both radio occultation experiments and radio astronomical observations, has led to the development of a facility at Georgia Tech which is capable of making such measurements.

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

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

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

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

  2. Al 1s-2p absorption spectroscopy of shock-wave heating and compression in laser-driven planar foil

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

    Sawada, H.; Regan, S. P.; Radha, P. B.

    Time-resolved Al 1s-2p absorption spectroscopy is used to diagnose direct-drive, shock-wave heating and compression of planar targets having nearly Fermi-degenerate plasma conditions (T{sub e}{approx}10-40 eV, {rho}{approx}3-11 g/cm{sup 3}) on the OMEGA Laser System [T. R. Boehly et al., Opt. Commun. 133, 495 (1997)]. A planar plastic foil with a buried Al tracer layer was irradiated with peak intensities of 10{sup 14}-10{sup 15} W/cm{sup 2} and probed with the pseudocontinuum M-band emission from a point-source Sm backlighter in the range of 1.4-1.7 keV. The laser ablation process launches 10-70 Mbar shock waves into the CH/Al/CH target. The Al 1s-2p absorption spectramore » were analyzed using the atomic physic code PRISMSPECT to infer T{sub e} and {rho} in the Al layer, assuming uniform plasma conditions during shock-wave heating, and to determine when the heat front penetrated the Al layer. The drive foils were simulated with the one-dimensional hydrodynamics code LILAC using a flux-limited (f=0.06 and f=0.1) and nonlocal thermal-transport model [V. N. Goncharov et al., Phys. Plasmas 13, 012702 (2006)]. The predictions of simulated shock-wave heating and the timing of heat-front penetration are compared to the observations. The experimental results for a wide variety of laser-drive conditions and buried depths have shown that the LILAC predictions using f=0.06 and the nonlocal model accurately model the shock-wave heating and timing of the heat-front penetration while the shock is transiting the target. The observed discrepancy between the measured and simulated shock-wave heating at late times of the drive can be explained by the reduced radiative heating due to lateral heat flow in the corona.« less

  3. Evidence for Ultra-fast Outflows in Radio-quiet Active Galactic Nuclei. II. Detailed Photoionization Modeling of Fe K-shell Absorption Lines

    NASA Astrophysics Data System (ADS)

    Tombesi, F.; Cappi, M.; Reeves, J. N.; Palumbo, G. G. C.; Braito, V.; Dadina, M.

    2011-11-01

    X-ray absorption line spectroscopy has recently shown evidence for previously unknown Ultra-fast Outflows (UFOs) in radio-quiet active galactic nuclei (AGNs). These have been detected essentially through blueshifted Fe XXV/XXVI K-shell transitions. In the previous paper of this series we defined UFOs as those highly ionized absorbers with an outflow velocity higher than 10,000 km s-1 and assessed the statistical significance of the associated blueshifted absorption lines in a large sample of 42 local radio-quiet AGNs observed with XMM-Newton. The present paper is an extension of that work. First, we report a detailed curve of growth analysis of the main Fe XXV/XXVI transitions in photoionized plasmas. Then, we estimate an average spectral energy distribution for the sample sources and directly model the Fe K absorbers in the XMM-Newton spectra with the detailed Xstar photoionization code. We confirm that the frequency of sources in the radio-quiet sample showing UFOs is >35% and that the majority of the Fe K absorbers are indeed associated with UFOs. The outflow velocity distribution spans from ~10,000 km s-1 (~0.03c) up to ~100,000 km s-1 (~0.3c), with a peak and mean value of ~42,000 km s-1 (~0.14c). The ionization parameter is very high and in the range log ξ ~ 3-6 erg s-1 cm, with a mean value of log ξ ~ 4.2 erg s-1 cm. The associated column densities are also large, in the range N H ~ 1022-1024 cm-2, with a mean value of N H ~ 1023 cm-2. We discuss and estimate how selection effects, such as those related to the limited instrumental sensitivity at energies above 7 keV, may hamper the detection of even higher velocities and higher ionization absorbers. We argue that, overall, these results point to the presence of extremely ionized and possibly almost Compton-thick outflowing material in the innermost regions of AGNs. This also suggests that UFOs may potentially play a significant role in the expected cosmological feedback from AGNs and their study can

  4. Superconducting Ti/TiN Thin Films for mm-Wave Absorption

    NASA Astrophysics Data System (ADS)

    Aliane, A.; Solana, M.; Rabaud, W.; Saminadayar, L.; Agnese, P.; Goudon, V.; Dussopt, L.; Vialle, C.; Baghe, E.; Pocas, S.; Carle, L.; Lio Soon Shun, N.; Becker, S.; Reveret, V.; Rodriguez, L.; Hamelin, A.; Poglitsch, A.; Bounissou, S.; Adami, O.

    2018-04-01

    Polarization-sensitive detectors at 120-500 GHz are required for the observation of the cosmic microwave background radiation. In this paper, superconducting thin films based on Ti/TiN bilayers are developed to be integrated as electromagnetic wave absorbers in suspended cooled silicon bolometers. The critical temperature (T c) is tuned in the range of 600-800 mK through the superconductivity proximity effect between Ti and TiN to optimize the absorption of the incident power while minimizing the heat capacity of the system at low temperature. Ti/TiN bilayer samples are fabricated on silicon with two different thicknesses (100/5 and 300/5 nm). Electrical characterizations at low temperature have been performed and revealed the effect of thermal annealing (20-250 °C) on residual stress, T c, critical magnetic field (H c) and resistance above T c. A physical characterization by X-ray photoelectron spectroscopy provides evidences of oxidized states which may explain these effects.

  5. Enabling technologies for millimeter-wave radio-over-fiber systems in next generation heterogeneous mobile access networks

    NASA Astrophysics Data System (ADS)

    Zhang, Junwen; Yu, Jianjun; Wang, Jing; Xu, Mu; Cheng, Lin; Lu, Feng; Shen, Shuyi; Yan, Yan; Cho, Hyunwoo; Guidotti, Daniel; Chang, Gee-kung

    2017-01-01

    Fifth-generation (5G) wireless access network promises to support higher access data rate with more than 1,000 times capacity with respect to current long-term evolution (LTE) systems. New radio-access-technologies (RATs) based on higher carrier frequencies to millimeter-wave (MMW) radio-over-fiber, and carrier-aggregation (CA) using multi-band resources are intensively studied to support the high data rate access and effectively use of frequency resources in heterogeneous mobile network (Het-Net). In this paper, we investigate several enabling technologies for MMW RoF systems in 5G Het-Net. Efficient mobile fronthaul (MFH) solutions for 5G centralized radio access network (C-RAN) and beyond are proposed, analyzed and experimentally demonstrated based on the analog scheme. Digital predistortion based on memory polynomial for analog MFH linearization are presented with improved EVM performances and receiver sensitivity. We also propose and experimentally demonstrate a novel inter-/intra- RAT CA scheme for 5G Het- Net. The real-time standard 4G-LTE signal is carrier-aggregated with three broadband 60GHz MMW signals based on proposed optical-domain band-mapping method. RATs based on new waveforms have also been studied here to achieve higher spectral-efficiency (SE) in asynchronous environments. Full-duplex asynchronous quasi-gapless carrier aggregation scheme for MMW ROF inter-/intra-RAT based on the FBMC is also presented with 4G-LTE signals. Compared with OFDM-based signals with large guard-bands, FBMC achieves higher spectral-efficiency with better EVM performance at less received power and smaller guard-bands.

  6. Theory of Type 3 and Type 2 Solar Radio Emissions

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  7. Sound absorption characteristics of tree bark and forest floor

    Treesearch

    G. Reethof; O. H. McDaniel; G. M. Heisler

    1977-01-01

    Results of basic research on absorption of sound by tree bark and forest floors are presented. Amount of sound absorption by tree bark was determined by laboratory experiments with bark samples in a standing-wave tube. A modified portable standing-wave tube was used to measure absorption of sound by forest floors with different moisture contents, with and without leaf...

  8. Four Decades of Space-Borne Radio Sounding

    NASA Technical Reports Server (NTRS)

    Benson, Robert F.

    2010-01-01

    A review is given of the 38 rocket, satellite, and planetary payloads dedicated to ionospheric/magnetospheric radio sounding since 1961. Between 1961 and 1995, eleven sounding-rocket payloads from four countries evolved from proof-of-concept flights to sophisticated instruments. Some involved dual payloads, with the sounder transmitter on one and the sounder receiver on the other. The rocket sounders addressed specific space-plasma-wave questions, and provided improved measurements of ionospheric electron-density (N(sub e)) field-aligned irregularities (FAI). Four countries launched 12 ionospheric topside-sounder satellites between 1962 and 1994, and an ionospheric sounder was placed on the Mir Space Station in 1998. Eleven magnetospheric radio sounders, most of the relaxation type, were launched from 1977 to 2000. The relaxation sounders used low-power transmitters, designed to stimulate plasma resonances for accurate local Ne determinations. The latest magnetospheric sounder designed for remote sensing incorporated long antennas and digital signal processing techniques to overcome the challenges posed by low Ne values and large propagation distances. Three radio sounders from three countries were included on payloads to extraterrestrial destinations from 1990 to 2003. The scientific accomplishments of space-borne radio sounders included (1) a wealth of global N(sub e) information on the topside ionosphere and magnetosphere, based on vertical and magnetic-field-aligned N(sub e) profiles; (2) accurate in-situ N(sub e) values, even under low-density conditions; and (3) fundamental advances in our understanding of the excitation and propagation of plasma waves, which have even led to the prediction of a new plasma-wave mode.

  9. Global modeling of the low- and middle-latitude ionospheric D and lower E regions and implications for HF radio wave absorption

    NASA Astrophysics Data System (ADS)

    Siskind, David E.; Zawdie, K. A.; Sassi, F.; Drob, D.; Friedrich, M.

    2017-01-01

    We compare D and lower E region ionospheric model calculations driven by the Whole Atmosphere Community Climate Model (WACCM) with a selection of electron density profiles made by sounding rockets over the past 50 years. The WACCM model, in turn, is nudged by winds and temperatures from the Navy Operational Global Atmospheric Prediction System-Advanced Level Physics High Altitude (NOGAPS-ALPHA). This nudging has been shown to greatly improve the representation of key neutral constituents, such as nitric oxide (NO), that are used as inputs to the ionospheric model. We show that with this improved representation, we greatly improve the comparison between calculated and observed electron densities relative to older studies. At midlatitudes, for both winter and equinoctal conditions, the model agrees well with the data. At tropical latitudes, our results confirm a previous suggestion that there is a model deficit in the calculated electron density in the lowermost D region. We then apply the calculated electron densities to examine the variation of HF absorption with altitude, latitude, and season and from 2008 to 2009. For low latitudes, our results agree with recent studies showing a primary peak absorption in the lower E region with a secondary peak below 75 km. For midlatitude to high latitude, the absorption contains a significant contribution from the middle D region where ionization of NO drives the ion chemistry. The difference in middle- to high-latitude absorption from 2008 to 2009 is due to changes in the NO abundance near 80 km from changes in the wintertime mesospheric residual circulation.

  10. Generating multiple orbital angular momentum vortex beams using a metasurface in radio frequency domain

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    In this paper, an electromagnetic metasurface is designed, fabricated, and experimentally demonstrated to generate multiple orbital angular momentum (OAM) vortex beams in radio frequency domain. Theoretical formula of compensated phase-shift distribution is deduced and used to design the metasurface to produce multiple vortex radio waves in different directions with different OAM modes. The prototype of a practical configuration of square-patch metasurface is designed, fabricated, and measured to validate the theoretical analysis at 5.8 GHz. The simulated and experimental results verify that multiple OAM vortex waves can be simultaneously generated by using a single electromagnetic metasurface. The proposed method paves an effective way to generate multiple OAM vortex waves in radio and microwave wireless communication applications.

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

    NASA Astrophysics Data System (ADS)

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

    2018-05-01

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

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

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

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

    2016-08-20

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

  13. Laboratory Evaluation and Application of Microwave Absorption Properties under Simulated Conditions for Planetary Atmospheres

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    2002-01-01

    Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments, entry probe radio signal absorption measurements, and earth-based or spacecraft-based radio astronomical (emission) observations can be used to infer abundances of microwave absorbing constituents in those atmospheres, as long as reliable information regarding the microwave absorbing properties of potential constituents is available. The use of theoretically-derived microwave absorption properties for such atmospheric constituents, or the use of laboratory measurements of such properties taken under environmental conditions that are significantly different than those of the planetary atmosphere being studied, often leads to significant misinterpretation of available opacity data. Laboratory measurements have shown that the centimeter-wavelength opacity from gaseous phosphine (PH3) under simulated conditions for the outer planets far exceeds that predicted from theory over a wide range of temperatures and pressures. This fundamentally changed the resulting interpretation of Voyager radio occultation data at Saturn and Neptune. It also directly impacts planning and scientific goals for study of Saturn's atmosphere with the Cassini Radio Science Experiment and the Rossini RADAR instrument. The recognition of the need to make such laboratory measurements of simulated planetary atmospheres over a range of temperatures and pressures which correspond to the altitudes probed by both radio occultation experiments and radio astronomical observations, and over a range of frequencies which correspond to those used in both spacecraft entry probe and orbiter (or flyby) radio occultation experiments and radio astronomical observations, has led to the development of a facility at Georgia Tech which is capable of making such measurements. It has been the goal of this investigation to conduct such measurements and to apply the results to a wide range of planetary observations

  14. H i Absorption in the Steep-Spectrum Superluminal Quasar 3C 216.

    PubMed

    Pihlström; Vermeulen; Taylor; Conway

    1999-11-01

    The search for H i absorption in strong compact steep-spectrum sources is a natural way to probe the neutral gas contents in young radio sources. In turn, this may provide information about the evolution of powerful radio sources. The recently improved capabilities of the Westerbork Synthesis Radio Telescope have made it possible to detect a 0.31% (19 mJy) deep neutral atomic hydrogen absorption line associated with the steep-spectrum superluminal quasar 3C 216. The redshift (z=0.67) of the source shifts the frequency of the 21 cm line down to the ultra-high-frequency (UHF) band (850 MHz). The exact location of the H i-absorbing gas remains to be determined by spectral line VLBI observations at 850 MHz. We cannot exclude that the gas might be extended on galactic scales, but we think it is more likely to be located in the central kiloparsec. Constraints from the lack of X-ray absorption probably rule out obscuration of the core region, and we argue that the most plausible site for the H i absorption is in the jet-cloud interaction observed in this source.

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

    NASA Astrophysics Data System (ADS)

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

    1995-12-01

    We present a statistical survey of electron beam signatures that are detected simultaneously at hard X-ray (HXR) and radio wavelengths during solar flares. For the identification of a simultaneous event we require a type III (normal-drifting or reverse-slope-drifting) radio burst that coincides (within ± 1 s) with a significant (≥ 3 σ HXR pulse of similar duration (≥ 1 s). Our survey covers all HXRBS/SMM and BATSE/CGRO flares that were simultaneously observed with the 0.1-1 GHz spectrometer Ikarus or the 0.1-3 GHz spectrometer Phoenix of ETH Zurich during 1980-1993. The major results and conclusions are as follows: 1. We identified 233 HXR pulses (out of 882) to be correlated with type III-like radio bursts: 77% with normal-drifting type III bursts, 34% with reverse-slope (RS)-drifting bursts, and 13% with oppositely drifting (III + RS) burst pairs. The majority of these cases provide evidence for acceleration of bidirectional electron beams. 2. The detailed correlation with type III-like radio bursts suggests that most of the subsecond fluctuations detectable in ≥ 25 keV HXR emission are related to discrete electron injections. This is also supported by the proportionality of the HXR pulse duration with the radio burst duration. The distribution of HXR pulse durations WX is found to have an exponential distribution, i.e., N(WX) ∝ exp (-WX/0.25 s) in the measured range of WX ≍ 0.5-1.5 s. 3. From oppositely drifting radio burst pairs we infer electron densities of ne = 109-1010 cm-3 at the acceleration site. From the absence of a frequency gap between the simultaneous start frequencies of upward and downward drifting radio bursts, we infer an upper limit of L ≤ 2000 km for the extent of the acceleration site and an acceleration time of Δt ≤ 3 ms for the (≥ 5 keV) radio-emitting electrons (in the case of parallel electric fields). 4. The relative timing between HXR pulses and radio bursts is best at the start frequency (of earliest radio detection

  16. Frequency and Thermal Behavior of Acoustic Absorption in ɛ-GaSe Crystals

    NASA Astrophysics Data System (ADS)

    Dzhafarova, S. Z.

    2018-04-01

    The paper presents results of measuring acoustic absorption in ɛ-GaSe crystals. The absorption of a longitudinal wave which propagates normal to the crystal layers, quadratically depends on frequency. However, it does not depend on temperature, i.e. it displays an Akhiezer behavior although its absolute value considerably exceeds the expected. The analysis of the frequency and thermal behavior of absorption of piezoelectric waves propagating along the layers, includes the deduction of contribution made by the interaction between waves and charge carriers. This analysis shows the linear dependence between the lattice absorption of these waves and the frequency. The linear frequency and weak temperature dependences of the acoustic absorption characterize the additional ultra-Akhiezer absorption in glasses. In our case, it can be caused by various polytypes forming in GaSe crystals which differ merely in a mutual arrangement of layers.

  17. Jupiter plasma wave observations: an initial voyager 1 overview.

    PubMed

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

    1979-06-01

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

  18. Ultrafast outflows in radio-loud active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Tombesi, F.; Tazaki, F.; Mushotzky, R. F.; Ueda, Y.; Cappi, M.; Gofford, J.; Reeves, J. N.; Guainazzi, M.

    2014-09-01

    Recent X-ray observations show absorbing winds with velocities up to mildly relativistic values of the order of ˜0.1c in a limited sample of six broad-line radio galaxies. They are observed as blueshifted Fe XXV-XXVI K-shell absorption lines, similarly to the ultrafast outflows (UFOs) reported in Seyferts and quasars. In this work we extend the search for such Fe K absorption lines to a larger sample of 26 radio-loud active galactic nuclei (AGN) observed with XMM-Newton and Suzaku. The sample is drawn from the Swift Burst Alert Telescope 58-month catalogue and blazars are excluded. X-ray bright Fanaroff-Riley Class II radio galaxies constitute the majority of the sources. Combining the results of this analysis with those in the literature we find that UFOs are detected in >27 per cent of the sources. However, correcting for the number of spectra with insufficient signal-to-noise ratio, we can estimate that the incidence of UFOs is this sample of radio-loud AGN is likely in the range f ≃ (50 ± 20) per cent. A photoionization modelling of the absorption lines with XSTAR allows us to estimate the distribution of their main parameters. The observed outflow velocities are broadly distributed between vout ≲ 1000 km s-1 and vout ≃ 0.4c, with mean and median values of vout ≃ 0.133c and vout ≃ 0.117c, respectively. The material is highly ionized, with an average ionization parameter of logξ ≃ 4.5 erg s-1 cm, and the column densities are larger than NH > 1022 cm-2. Overall, these characteristics are consistent with the presence of complex accretion disc winds in a significant fraction of radio-loud AGN and demonstrate that the presence of relativistic jets does not preclude the existence of winds, in accordance with several theoretical models.

  19. Geotechnical sensing using electromagnetic attenuation between radio transceivers

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  20. Radio Heating of Lunar Soil to Release Gases

    NASA Technical Reports Server (NTRS)

    Chui, Talso; Penanen, Konstantin

    2006-01-01

    A report proposes the development of a system to collect volatile elements and compounds from Lunar soil for use in supporting habitation and processing into rocket fuel. Prior exploratory missions revealed that H2, He, and N2 are present in Lunar soil and there are some indications that water ice may also be present. The proposed system would include a shroud that would be placed on the Lunar surface. Inside the shroud would be a radio antenna aimed downward. The antenna would be excited at a suitably high power and at a frequency chosen to optimize the depth of penetration of radio waves into the soil. The radio waves would heat the soil, thereby releasing volatiles bound to soil particles. The escaping volatiles would be retained by the shroud and collected by condensation in a radiatively cooled vessel connected to the shroud. It has been estimated that through radio-frequency heating at a power of 10 kW for one day, it should be possible to increase the temperature of a soil volume of about 1 cubic m by about 200 C -- an amount that should suffice for harvesting a significant quantity of volatile material.

  1. Waves in Space Plasmas (WISP)

    NASA Technical Reports Server (NTRS)

    Calvert, Wynne

    1994-01-01

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

  2. Graphene electrostatic microphone and ultrasonic radio

    PubMed Central

    Zhou, Qin; Zheng, Jinglin; Onishi, Seita; Crommie, M. F.; Zettl, Alex K.

    2015-01-01

    We present a graphene-based wideband microphone and a related ultrasonic radio that can be used for wireless communication. It is shown that graphene-based acoustic transmitters and receivers have a wide bandwidth, from the audible region (20∼20 kHz) to the ultrasonic region (20 kHz to at least 0.5 MHz). Using the graphene-based components, we demonstrate efficient high-fidelity information transmission using an ultrasonic band centered at 0.3 MHz. The graphene-based microphone is also shown to be capable of directly receiving ultrasound signals generated by bats in the field, and the ultrasonic radio, coupled to electromagnetic (EM) radio, is shown to function as a high-accuracy rangefinder. The ultrasonic radio could serve as a useful addition to wireless communication technology where the propagation of EM waves is difficult. PMID:26150483

  3. Generating multiple orbital angular momentum vortex beams using a metasurface in radio frequency domain

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

    Yu, Shixing; Li, Long, E-mail: lilong@mail.xidian.edu.cn, E-mail: gmshi@xidian.edu.cn; Shi, Guangming, E-mail: lilong@mail.xidian.edu.cn, E-mail: gmshi@xidian.edu.cn

    In this paper, an electromagnetic metasurface is designed, fabricated, and experimentally demonstrated to generate multiple orbital angular momentum (OAM) vortex beams in radio frequency domain. Theoretical formula of compensated phase-shift distribution is deduced and used to design the metasurface to produce multiple vortex radio waves in different directions with different OAM modes. The prototype of a practical configuration of square-patch metasurface is designed, fabricated, and measured to validate the theoretical analysis at 5.8 GHz. The simulated and experimental results verify that multiple OAM vortex waves can be simultaneously generated by using a single electromagnetic metasurface. The proposed method paves an effectivemore » way to generate multiple OAM vortex waves in radio and microwave wireless communication applications.« less

  4. Galileo radio science investigations

    NASA Technical Reports Server (NTRS)

    Howard, H. T.; Eshleman, V. R.; Hinson, D. P.; Kliore, A. J.; Lindal, G. F.; Woo, R.; Bird, M. K.; Volland, H.; Edenhoffer, P.; Paetzold, M.

    1992-01-01

    Galileo radio-propagation experiments are based on measurements of absolute and differential propagation time delay, differential phase delay, Doppler shift, signal strength, and polarization. These measurements can be used to study: the atmospheric and ionospheric structure, constituents, and dynamics of Jupiter; the magnetic field of Jupiter; the diameter of Io, its ionospheric structure, and the distribution of plasma in the Io torus; the diameters of the other Galilean satellites, certain properties of their surfaces, and possibly their atmospheres and ionospheres; and the plasma dynamics and magnetic field of the solar corona. The spacecraft system provides linear rather than circular polarization on the S-band downlink signal, the capability to receive X-band uplink signals, and a differential downlink ranging mode. A highly-stable, dual-frequency, spacecraft radio system is developed that is suitable for simultaneous measurements of all the parameters normally attributed to radio waves.

  5. Radio Flares from Gamma-ray Bursts

    NASA Astrophysics Data System (ADS)

    Kopač, D.; Mundell, C. G.; Kobayashi, S.; Virgili, F. J.; Harrison, R.; Japelj, J.; Guidorzi, C.; Melandri, A.; Gomboc, A.

    2015-06-01

    We present predictions of centimeter and millimeter radio emission from reverse shocks (RSs) in the early afterglows of gamma-ray bursts (GRBs) with the goal of determining their detectability with current and future radio facilities. Using a range of GRB properties, such as peak optical brightness and time, isotropic equivalent gamma-ray energy, and redshift, we simulate radio light curves in a framework generalized for any circumburst medium structure and including a parameterization of the shell thickness regime that is more realistic than the simple assumption of thick- or thin-shell approximations. Building on earlier work by Mundell et al. and Melandri et al. in which the typical frequency of the RS was suggested to lie at radio rather than optical wavelengths at early times, we show that the brightest and most distinct RS radio signatures are detectable up to 0.1-1 day after the burst, emphasizing the need for rapid radio follow-up. Detection is easier for bursts with later optical peaks, high isotropic energies, lower circumburst medium densities, and at observing frequencies that are less prone to synchrotron self-absorption effects—typically above a few GHz. Given recent detections of polarized prompt gamma-ray and optical RS emission, we suggest that detection of polarized radio/millimeter emission will unambiguously confirm the presence of low-frequency RSs at early time.

  6. The Soviet contributions towards MAP/WINE

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  7. Voyager 1 Planetary Radio Astronomy Observations Near Jupiter

    NASA Technical Reports Server (NTRS)

    Warwick, J. W.; Pearce, J. B.; Riddle, A. C.; Alexander, J. K.; Desch, M. D.; Kaiser, M. L.; Thieman, J. R.; Carr, T. B.; Gulkis, S.; Boischot, A.

    1979-01-01

    Results are reported from the first low frequency radio receiver to be transported into the Jupiter magnetosphere. Dramatic new information was obtained both because Voyager was near or in Jupiter's radio emission sources and also because it was outside the relatively dense solar wind plasma of the inner solar system. Extensive radio arcs, from above 30 MHz to about 1 MHz, occurred in patterns correlated with planetary longitude. A newly discovered kilometric wavelength radio source may relate to the plasma torus near Io's orbit. In situ wave resonances near closest approach define an electron density profile along the Voyager trajectory and form the basis for a map of the torus. Studies in progress are outlined briefly.

  8. Full-wave reflection of lightning long-wave radio pulses from the ionospheric D region: Comparison with midday observations of broadband lightning signals

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

    We are developing and testing a steep-incidence D region sounding method for inferring profile information, principally regarding electron density. The method uses lightning emissions (in the band 5-500 kHz) as the probe signal. The data are interpreted by comparison against a newly developed single-reflection model of the radio wave's encounter with the lower ionosphere. The ultimate application of the method will be to study transient, localized disturbances of the nocturnal D region, including those instigated by lightning itself. Prior to applying the method to study lightning-induced perturbations of the nighttime D region, we have performed a validation test against more stable and predictable daytime observations, where the profile of electron density is largely determined by direct solar X-ray illumination. This article reports on the validation test. Predictions from our recently developed full-wave ionospheric-reflection model are compared to statistical summaries of daytime lightning radiated waveforms, recorded by the Los Alamos Sferic Array. The comparison is used to retrieve best fit parameters for an exponential profile of electron density in the ionospheric D region. The optimum parameter values are compared to those found elsewhere using a narrowband beacon technique, which used totally different measurements, ranges, and modeling approaches from those of the work reported here.

  9. Sun Radio Interferometer Space Experiment (SunRISE)

    NASA Astrophysics Data System (ADS)

    Kasper, Justin C.; SunRISE Team

    2018-06-01

    The Sun Radio Interferometer Space Experiment (SunRISE) is a NASA Heliophysics Explorer Mission of Opportunity currently in Phase A. SunRISE is a constellation of spacecraft flying in a 10-km diameter formation and operating as the first imaging radio interferometer in space. The purpose of SunRISE is to reveal critical aspects of solar energetic particle (SEP) acceleration at coronal mass ejections (CMEs) and transport into space by making the first spatially resolved observations of coherent Type II and III radio bursts produced by electrons accelerated at CMEs or released from flares. SunRISE will focus on solar Decametric-Hectometric (DH, 0.1 < f < 15 MHz) radio bursts that always are detected from space before major SEP events, but cannot be seen on Earth due to ionospheric absorption. This talk will describe SunRISE objectives and implementation. Presented on behalf of the entire SunRISE team.

  10. Interplanetary Radio Transmission Through Serial Ionospheric and Material Barriers

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

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

    2013-01-01

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

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

    ERIC Educational Resources Information Center

    Feraria, Paulette J.

    2018-01-01

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

  12. Ground and space observations of medium frequency auroral radio emissions

    NASA Astrophysics Data System (ADS)

    Broughton, Matthew C.

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

  13. Phenomena Associated with EIT Waves

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  14. Phenomena Associated With EIT Waves

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  15. Past and future of radio occultation studies of planetary atmospheres

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  16. Solar Phenomena Associated with "EIT Waves"

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2018-05-01

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

  18. Preparation of Reduced Graphene Oxide/MnO Composite and Its Electromagnetic Wave Absorption Performance

    NASA Astrophysics Data System (ADS)

    Yuan, Jiangtao; Li, Kunzhen; Liu, Zhongfei; Jin, Shaowei; Li, Shikuo; Zhang, Hui

    2018-02-01

    The composite containing reduced graphene oxide and MnO nanoparticles (RGO/MnO) has been prepared via a one step pyrolysis method. The MnO nanoparticles were uniformly dispersed on the surface of RGO nanosheets forming MnO/RGO composite. The composite displays a maximum absorption of ‒38.9 dB at 13.5 GHz and the bandwidth of reflection loss corresponding to -10 dB can reach 4.9 GHz (from 11.5 to 16.4 GHz) with a coating layer thickness of only 2 mm. Therefore, the obtained RGO/MnO composite a perfect lightweight and high-performance electromagnetic wave absorbent.

  19. Solar radio emissions: 2D full PIC simulations

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  20. Radio Frequency Signals in Jupiter's Atmosphere

    PubMed

    Lanzerotti; Rinnert; Dehmel; Gliem; Krider; Uman; Bach

    1996-05-10

    During the Galileo probe's descent through Jupiter's atmosphere, under the ionosphere, the lightning and radio emission detector measured radio frequency signals at levels significantly above the probe's electromagnetic noise. The signal strengths at 3 and 15 kilohertz were relatively large at the beginning of the descent, decreased with depth to a pressure level of about 5 bars, and then increased slowly until the end of the mission. The 15-kilohertz signals show arrival direction anisotropies. Measurements of radio frequency wave forms show that the probe passed through an atmospheric region that did not support lightning within at least 100 kilometers and more likely a few thousand kilometers of the descent trajectory. The apparent opacity of the jovian atmosphere increases sharply at pressures greater than about 4 bars.

  1. Computational studies on scattering of radio frequency waves by density filaments in fusion plasmas

    NASA Astrophysics Data System (ADS)

    Ioannidis, Zisis C.; Ram, Abhay K.; Hizanidis, Kyriakos; Tigelis, Ioannis G.

    2017-10-01

    In modern magnetic fusion devices, such as tokamaks and stellarators, radio frequency (RF) waves are commonly used for plasma heating and current profile control, as well as for certain diagnostics. The frequencies of the RF waves range from ion cyclotron frequency to the electron cyclotron frequency. The RF waves are launched from structures, like waveguides and current straps, placed near the wall in a very low density, tenuous plasma region of a fusion device. The RF electromagnetic fields have to propagate through this scrape-off layer before coupling power to the core of the plasma. The scrape-off layer is characterized by turbulent plasmas fluctuations and by blobs and filaments. The variations in the edge density due to these fluctuations and filaments can affect the propagation characteristics of the RF waves—changes in density leading to regions with differing plasma permittivity. Analytical full-wave theories have shown that scattering by blobs and filaments can alter the RF power flow into the core of the plasma in a variety of ways, such as through reflection, refraction, diffraction, and shadowing [see, for example, Ram and Hizanidis, Phys. Plasmas 23, 022504 (2016), and references therein]. There are changes in the wave vectors and the distribution of power-scattering leading to coupling of the incident RF wave to other plasma waves, side-scattering, surface waves, and fragmentation of the Poynting flux in the direction towards the core. However, these theoretical models are somewhat idealized. In particular, it is assumed that there is step-function discontinuity in the density between the plasma inside the filament and the background plasma. In this paper, results from numerical simulations of RF scattering by filaments using a commercial full-wave code are described. The filaments are taken to be cylindrical with the axis of the cylinder aligned along the direction of the ambient magnetic field. The plasma inside and outside the filament is

  2. Method and apparatus for radio frequency ceramic sintering

    DOEpatents

    Hoffman, Daniel J.; Kimrey, Jr., Harold D.

    1993-01-01

    Radio frequency energy is used to sinter ceramic materials. A coaxial waveguide resonator produces a TEM mode wave which generates a high field capacitive region in which a sample of the ceramic material is located. Frequency of the power source is kept in the range of radio frequency, and preferably between 60-80 MHz. An alternative embodiment provides a tunable radio frequency circuit which includes a series input capacitor and a parallel capacitor, with the sintered ceramic connected by an inductive lead. This arrangement permits matching of impedance over a wide range of dielectric constants, ceramic volumes, and loss tangents.

  3. Method and apparatus for radio frequency ceramic sintering

    DOEpatents

    Hoffman, D.J.; Kimrey, H.D. Jr.

    1993-11-30

    Radio frequency energy is used to sinter ceramic materials. A coaxial waveguide resonator produces a TEM mode wave which generates a high field capacitive region in which a sample of the ceramic material is located. Frequency of the power source is kept in the range of radio frequency, and preferably between 60-80 MHz. An alternative embodiment provides a tunable radio frequency circuit which includes a series input capacitor and a parallel capacitor, with the sintered ceramic connected by an inductive lead. This arrangement permits matching of impedance over a wide range of dielectric constants, ceramic volumes, and loss tangents. 6 figures.

  4. Detection of Propagating Fast Sausage Waves through Detailed Analysis of a Zebra-pattern Fine Structure in a Solar Radio Burst

    NASA Astrophysics Data System (ADS)

    Kaneda, K.; Misawa, H.; Iwai, K.; Masuda, S.; Tsuchiya, F.; Katoh, Y.; Obara, T.

    2018-03-01

    Various magnetohydrodynamic (MHD) waves have recently been detected in the solar corona and investigated intensively in the context of coronal heating and coronal seismology. In this Letter, we report the first detection of short-period propagating fast sausage mode waves in a metric radio spectral fine structure observed with the Assembly of Metric-band Aperture Telescope and Real-time Analysis System. Analysis of Zebra patterns (ZPs) in a type-IV burst revealed a quasi-periodic modulation in the frequency separation between the adjacent stripes of the ZPs (Δf ). The observed quasi-periodic modulation had a period of 1–2 s and exhibited a characteristic negative frequency drift with a rate of 3–8 MHz s‑1. Based on the double plasma resonance model, the most accepted generation model of ZPs, the observed quasi-periodic modulation of the ZP can be interpreted in terms of fast sausage mode waves propagating upward at phase speeds of 3000–8000 km s‑1. These results provide us with new insights for probing the fine structure of coronal loops.

  5. Exploration of High Harmonic Fast Wave Heating on the National Spherical Torus Experiment

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

    J.R. Wilson; R.E. Bell; S. Bernabei

    2003-02-11

    High Harmonic Fast Wave (HHFW) heating has been proposed as a particularly attractive means for plasma heating and current drive in the high-beta plasmas that are achievable in spherical torus (ST) devices. The National Spherical Torus Experiment (NSTX) [Ono, M., Kaye, S.M., Neumeyer, S., et al., Proceedings, 18th IEEE/NPSS Symposium on Fusion Engineering, Albuquerque, 1999, (IEEE, Piscataway, NJ (1999), p. 53.)] is such a device. An radio-frequency (rf) heating system has been installed on NSTX to explore the physics of HHFW heating, current drive via rf waves and for use as a tool to demonstrate the attractiveness of the STmore » concept as a fusion device. To date, experiments have demonstrated many of the theoretical predictions for HHFW. In particular, strong wave absorption on electrons over a wide range of plasma parameters and wave parallel phase velocities, wave acceleration of energetic ions, and indications of current drive for directed wave spectra have been observed. In addition HHFW heating has been used to explore the energy transport properties of NSTX plasmas, to create H-mode (high-confinement mode) discharges with a large fraction of bootstrap current and to control the plasma current profile during the early stages of the discharge.« less

  6. First observations of large-scale wave structure and equatorial spread F using CERTO radio beacon on the C/NOFS satellite

    NASA Astrophysics Data System (ADS)

    Thampi, Smitha V.; Yamamoto, Mamoru; Tsunoda, Roland T.; Otsuka, Yuichi; Tsugawa, Takuya; Uemoto, Jyunpei; Ishii, Mamoru

    2009-09-01

    First observations of large-scale wave structure (LSWS) and the subsequent development of equatorial spread F (ESF), using total electron content (TEC) derived from the ground based reception of beacon signals from the CERTO (Coherent Electromagnetic Radio Tomography) radio beacon on board C/NOFS (Communications/Navigation Outage Forecasting System) satellite, are presented. Selected examples of TEC variations, using measurements made during January 2009 from Bac Lieu, Vietnam (9.2°N, 105.6°E geographic, 1.7°N magnetic dip latitude) are presented to illustrate two key findings: (1) LSWS appears to play a more important role in the development of ESF than the post-sunset rise (PSSR) of the F-layer, and (2) LSWS can appear well before E region sunset. Other findings, that LSWS does not have significant zonal drift in the initial stages of growth, and can have zonal wavelengths of several hundred kilometers, corroborate earlier reports.

  7. Modeling the variations of reflection coefficient of Earth's lower ionosphere using very low frequency radio wave data by artificial neural network

    NASA Astrophysics Data System (ADS)

    Ghanbari, Keyvan; Khakian Ghomi, Mehdi; Mohammadi, Mohammad; Marbouti, Marjan; Tan, Le Minh

    2016-08-01

    The ionized atmosphere lying from 50 to 600 km above surface, known as ionosphere, contains high amount of electrons and ions. Very Low Frequency (VLF) radio waves with frequencies between 3 and 30 kHz are reflected from the lower ionosphere specifically D-region. A lot of applications in long range communications and navigation systems have been inspired by this characteristic of ionosphere. There are several factors which affect the ionization rate in this region, such as: time of day (presence of sun in the sky), solar zenith angle (seasons) and solar activities. Due to nonlinear response of ionospheric reflection coefficient to these factors, finding an accurate relation between these parameters and reflection coefficient is an arduous task. In order to model these kinds of nonlinear functionalities, some numerical methods are employed. One of these methods is artificial neural network (ANN). In this paper, the VLF radio wave data of 4 sudden ionospheric disturbance (SID) stations are given to a multi-layer perceptron ANN in order to simulate the variations of reflection coefficient of D region ionosphere. After training, validation and testing the ANN, outputs of ANN and observed values are plotted together for 2 random cases of each station. By evaluating the results using 2 parameters of pearson correlation coefficient and root mean square error, a satisfying agreement was found between ANN outputs and real observed data.

  8. Part-body and multibody effects on absorption of radio-frequency electromagnetic energy by animals and by models of man

    NASA Technical Reports Server (NTRS)

    Gandhi, O. P.; Hagmann, M. J.; Dandrea, J. A.

    1979-01-01

    Fine structure in the whole-body resonant curve for radio-frequency energy deposition in man can be attributed to part-body resonances. As for head resonance, which occurs near 350 MHz in man, the absorptive cross section is nearly three times the physical cross section of the head. The arm has a prominent resonance at 150 MHz. Numerical solutions, antenna theory, and experimental results on animals have shown that whole-body energy deposition may be increased by 50 percent or more because of multiple bodies that are strategically located in the field. Empirical equations for SARs are also presented along with test data for several species of laboratory animals. Barbiturate anesthesia is sufficiently disruptive of thermoregulation that delta Ts of colonic temperature yield energy dose values in several mammals that compare quite favorably with those based on whole-body calorimetry.

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

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    1987-01-01

    Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments and Earth-based radio astronomical observations can be used to infer abundances of microwave absorbing atmospheric constituents in those atmospheres, as long as reliable information regarding the microwave absorping properties of potential constituents is available. The use of theoretically derived microwave absorption properties for such atmospheric constituents, or laboratory measurements of such properties under environmental conditions which are significantly different than those of the planetary atmosphere being studied, often leads to significant misinterpretation of available opacity data. Laboratory measurement of the microwave properties of atmospheric gases under simulated conditions for the outer planets were conducted. Results of these measurements are discussed.

  10. A decametric wavelength radio telescope for interplanetary scintillation observations

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

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

  11. Voyager 1 planetary radio astronomy observations near jupiter.

    PubMed

    Warwick, J W; Pearce, J B; Riddle, A C; Alexander, J K; Desch, M D; Kaiser, M L; Thieman, J R; Carr, T D; Gulkis, S; Boischot, A; Harvey, C C; Pedersen, B M

    1979-06-01

    We report results from the first low-frequency radio receiver to be transported into the Jupiter magnetosphere. We obtained dramatic new information, both because Voyager was near or in Jupiter's radio emission sources and also because it was outside the relatively dense solar wind plasma of the inner solar system. Extensive radio spectral arcs, from above 30 to about 1 megahertz, occurred in patterns correlated with planetary longitude. A newly discovered kilometric wavelength radio source may relate to the plasma torus near Io's orbit. In situ wave resonances near closest approach define an electron density profile along the Voyager trajectory and form the basis for a map of the torus. Detailed studies are in progress and are out-lined briefly.

  12. Decameter-wave radio observations of Jupiter during the 1977 apparition

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

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

  13. Ultra-thin enhanced-absorption long-wave infrared detectors

    NASA Astrophysics Data System (ADS)

    Wang, Shaohua; Yoon, Narae; Kamboj, Abhilasha; Petluru, Priyanka; Zheng, Wanhua; Wasserman, Daniel

    2018-02-01

    We propose an architecture for enhanced absorption in ultra-thin strained layer superlattice detectors utilizing a hybrid optical cavity design. Our detector architecture utilizes a designer-metal doped semiconductor ground plane beneath the ultra-subwavelength thickness long-wavelength infrared absorber material, upon which we pattern metallic antenna structures. We demonstrate the potential for near 50% detector absorption in absorber layers with thicknesses of approximately λ0/50, using realistic material parameters. We investigate detector absorption as a function of wavelength and incidence angle, as well as detector geometry. The proposed device architecture offers the potential for high efficiency detectors with minimal growth costs and relaxed design parameters.

  14. CURIE: Cubesat Radio Interferometry Experiment

    NASA Astrophysics Data System (ADS)

    Sundkvist, D. J.; Saint-Hilaire, P.; Bain, H. M.; Bale, S. D.; Bonnell, J. W.; Hurford, G. J.; Maruca, B.; Martinez Oliveros, J. C.; Pulupa, M.

    2016-12-01

    The CUbesat Radio Interferometry Experiment (CURIE) is a proposed two-element radio interferometer, based on proven and developed digital radio receivers and designed to fit within a Cubesat platform. CURIE will launch as a 6U Cubesat and then separate into two 3U Cubesats once in orbit. CURIE measures radio waves from 0.1-19MHz, which must be measured from space, as those frequencies fall below the cutoff imposed by Earth's ionosphere. The principal science objective for CURIE is to use radio interferometry to study radio burst emissions from solar eruptive events such as flares and coronal mass ejections (CMEs) in the inner heliosphere, providing observations important for our understanding of the heliospheric space weather environment. The influence of space weather can be felt at Earth and other planets, as radiation levels increase and lead to auroral activity and geomagnetic effects. CURIE will be able to determine the location and size of radio burst source regions and then to track their movement outward from the Sun. In addition to the primary objective CURIE will measure the gradients of the local ionospheric density and electron temperature on the spatial scale of a few kilometers, as well as create an improved map of the radio sky at these unexplored frequencies. A space based radio interferometry observatory has long been envisioned, in orbit around the Earth or the Moon, or on the far side of the Moon. Beyond its important science objectives, CURIE will prove that the concept of a dedicated space-based interferometer can be realized by using relatively cheap Cubesats. CURIE will therefore not only provide new important science results but also serve as a pathfinder in the development of new space-based radio observation techniques for helio- and astro-physics.

  15. [Development of innovative methods of electromagnetic field evaluation for portable radio-station].

    PubMed

    Rubtsova, N B; Perov, S Iu; Bogacheva, E V; Kuster, N

    2013-01-01

    The results of portable radio-station "Radiy-301" electromagnetic fields (EMF) emission measurement and specific absorption rate data evaluation has shown that workers' exposure EMF levels may elevate hygienic norms and hereupon can be health risk factor. Possible way of portable radio-station EMF dosimetry enhancement by means of domestic and international approaches harmonization is considered.

  16. MASER: Measuring, Analysing, Simulating low frequency Radio Emissions.

    NASA Astrophysics Data System (ADS)

    Cecconi, B.; Le Sidaner, P.; Savalle, R.; Bonnin, X.; Zarka, P. M.; Louis, C.; Coffre, A.; Lamy, L.; Denis, L.; Griessmeier, J. M.; Faden, J.; Piker, C.; André, N.; Genot, V. N.; Erard, S.; King, T. A.; Mafi, J. N.; Sharlow, M.; Sky, J.; Demleitner, M.

    2017-12-01

    The MASER (Measuring, Analysing and Simulating Radio Emissions) project provides a comprehensive infrastructure dedicated to low frequency radio emissions (typically < 50 to 100 MHz). The four main radio sources observed in this frequency are the Earth, the Sun, Jupiter and Saturn. They are observed either from ground (down to 10 MHz) or from space. Ground observatories are more sensitive than space observatories and capture high resolution data streams (up to a few TB per day for modern instruments). Conversely, space-borne instruments can observe below the ionospheric cut-off (10 MHz) and can be placed closer to the studied object. Several tools have been developed in the last decade for sharing space physcis data. Data visualization tools developed by The CDPP (http://cdpp.eu, Centre de Données de la Physique des Plasmas, in Toulouse, France) and the University of Iowa (Autoplot, http://autoplot.org) are available to display and analyse space physics time series and spectrograms. A planetary radio emission simulation software is developed in LESIA (ExPRES: Exoplanetary and Planetary Radio Emission Simulator). The VESPA (Virtual European Solar and Planetary Access) provides a search interface that allows to discover data of interest for scientific users, and is based on IVOA standards (astronomical International Virtual Observatory Alliance). The University of Iowa also develops Das2server that allows to distribute data with adjustable temporal resolution. MASER is making use of all these tools and standards to distribute datasets from space and ground radio instruments available from the Observatoire de Paris, the Station de Radioastronomie de Nançay and the CDPP deep archive. These datasets include Cassini/RPWS, STEREO/Waves, WIND/Waves, Ulysses/URAP, ISEE3/SBH, Voyager/PRA, Nançay Decameter Array (Routine, NewRoutine, JunoN), RadioJove archive, swedish Viking mission, Interball/POLRAD... MASER also includes a Python software library for reading raw data.

  17. The detectability of radio emission from exoplanets

    NASA Astrophysics Data System (ADS)

    Lynch, C. R.; Murphy, Tara; Lenc, E.; Kaplan, D. L.

    2018-05-01

    Like the magnetised planets in our Solar System, magnetised exoplanets should emit strongly at radio wavelengths. Radio emission directly traces the planetary magnetic fields and radio detections can place constraints on the physical parameters of these features. Large comparative studies of predicted radio emission characteristics for the known population of exoplanets help to identify what physical parameters could be key for producing bright, observable radio emission. Since the last comparative study, many thousands of exoplanets have been discovered. We report new estimates for the radio flux densities and maximum emission frequencies for the current population of known exoplanets orbiting pre-main sequence and main-sequence stars with spectral types F-M. The set of exoplanets predicted to produce observable radio emission are Hot Jupiters orbiting young stars. The youth of these system predicts strong stellar magnetic fields and/or dense winds, which are key for producing bright, observable radio emission. We use a new all-sky circular polarisation Murchison Widefield Array survey to place sensitive limits on 200 MHz emission from exoplanets, with 3σ values ranging from 4.0 - 45.0 mJy. Using a targeted Giant Metre Wave Radio Telescope observing campaign, we also report a 3σ upper limit of 4.5 mJy on the radio emission from V830 Tau b, the first Hot Jupiter to be discovered orbiting a pre-main sequence star. Our limit is the first to be reported for the low-frequency radio emission from this source.

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

    NASA Technical Reports Server (NTRS)

    Gopalswamy, N.; Nitta, N.

    2011-01-01

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

  19. Properties of seismic absorption induced reflections

    NASA Astrophysics Data System (ADS)

    Zhao, Haixia; Gao, Jinghuai; Peng, Jigen

    2018-05-01

    Seismic reflections at an interface are often regarded as the variation of the acoustic impedance (product of seismic velocity and density) in a medium. In fact, they can also be generated due to the difference in absorption of the seismic energy. In this paper, we investigate the properties of such reflections. Based on the diffusive-viscous wave equation and elastic diffusive-viscous wave equation, we investigate the dependency of the reflection coefficients on frequency, and their variations with incident angles. Numerical results at a boundary due to absorption contrasts are compared with those resulted from acoustic impedance variation. It is found that, the reflection coefficients resulted from absorption depend significantly on the frequency especially at lower frequencies, but vary very slowly at small incident angles. At the higher frequencies, the reflection coefficients of diffusive-viscous wave and elastic diffusive-viscous wave are close to those of acoustic and elastic cases, respectively. On the other hand, the reflections caused by acoustic impedance variation are independent of frequency but vary distinctly with incident angles before the critical angle. We also investigate the difference between the seismograms generated in the two different media. The numerical results show that the amplitudes of these reflected waves are attenuated and their phases are shifted. However, the reflections obtained by acoustic impedance contrast, show no significant amplitude attenuation and phase shift.

  20. Artificial optical emissions in the thermosphere induced by powerful radio waves: A review

    NASA Astrophysics Data System (ADS)

    Kosch, M.; Senior, A.; Gustavsson, B.; Grach, S.; Pedersen, T.; Rietveld, M.

    High-power high-frequency radio waves beamed into the ionosphere with O-mode polarization cause plasma turbulence which can accelerate electrons These electrons collide with the F-layer neutrals causing artificial optical emissions identical to natural aurora The brightest optical emissions are O 1D 630 nm with a threshold of 2 eV and O 1S 557 7 nm with a threshold of 4 2 eV The optical emissions give direct evidence of electron acceleration by plasma turbulence as well as their non-Maxwellian energy spectrum HF pumping of the ionosphere also causes electron temperature enhancements but these alone are not sufficient to explain the optical emissions EISCAT plasma-line measurements indicate that the enhanced electron temperatures are consistent with the bulk of the electrons having a Maxwellian energy spectrum Novel discoveries include 1 Very large electron temperature enhancements of several 1000 K which maximise along the magnetic field line direction 2 Ion temperature enhancements of a few 100 K 3 Large ion outflows exceeding 200 m s 4 The F-layer optical emission maximizes sharply near the magnetic zenith with clear evidence of self-focusing 5 The optical emission generally appears below the HF pump reflection altitude as well as the upper-hybrid resonance height 6 The optical emission and HF coherent radar backscatter generally minimize when pumping on the third or higher electron gyro-harmonic frequency suggesting upper-hybrid waves as the primary mechanism 7 The optical emissions and HF coherent backscatter are enhanced on the

  1. Synthesis of u-channelled spherical Fex(CoyNi1-y)100-x Janus colloidal particles with excellent electromagnetic wave absorption performance.

    PubMed

    Li, Hao; Cao, Zhenming; Lin, Jiayao; Zhao, Hui; Jiang, Qiaorong; Jiang, Zhiyuan; Liao, Honggang; Kuang, Qin; Xie, Zhaoxiong

    2018-01-25

    Due to their distinctive structure, inherently anisotropic properties and broad applications, Janus colloidal particles have attracted tremendous attention and it is significant to synthesize high yield Janus colloidal particles in a cost-effective and reliable way. On the other hand, due to the expanded electromagnetic interference problems, it is highly desired to develop excellent electromagnetic wave absorbing materials with an ultra-wide absorption bandwidth for practical application. Herein, a confined liquid-solid redox reaction strategy has been developed to fabricate a series of Fe x (Co y Ni 1-y ) 100-x ternary alloy particles. The as-prepared particles are in the form of u-channelled noncentrosymmetric spheres, one kind of Janus colloidal particles which have been rarely observed. Due to the combination and synergy effects of multi-magnetic metals, the polycrystalline structure and their specific morphology, the as-prepared particles possess multiple magnetic resonance and multiple dielectric relaxation processes, and therefore show excellent electromagnetic wave absorption performances. In particular, the strongest reflection loss (RL) of the Fe 15 (Co 0.2 Ni 0.8 ) 85 Janus colloidal particles is up to -36.9 dB with a thickness of 2.5 mm, and the effective absorption (RL < -10 dB) bandwidth can reach 9.2 GHz (8-17.2 GHz) with a thickness of 2 mm. Such a wide bandwidth has barely been reported for magnetic metal alloys under a single thickness. These results suggest that the Fe x (Co y Ni 1-y ) 100-x Janus particles could be a promising candidate for highly efficient electromagnetic wave absorbing materials for practical application.

  2. Gravity Waves in the Atmosphere of Mars as seen by the Radio Science Experiment MaRS on Mars Express

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

    Gravity waves are atmospheric waves whose restoring force is the buoyancy. They are known to play an essential role in the redistribution of energy, momentum and atmospheric constituents in all stably stratified planetary atmospheres. Possible excitation mechanisms comprise convection in an adjacent atmospheric layer, other atmospheric instabilities like wind shear instabilities, or air flow over orographic obstacles especially in combination with the strong winter jets on Mars. Gravity waves on Mars were observed in the lower atmosphere [1,2] but are also expected to play a major role in the cooling of the thermosphere [3] and the polar warming [4]. A fundamental understanding of the possible source mechanisms is required to reveal the influence of small scale gravity waves on the global atmospheric circulation. Radio occultation profiles from the MaRS experiment on Mars Express [5] with their exceptionally high vertical resolution can be used to study small-scale vertical gravity waves and their global distribution in the lower atmosphere from the planetary boundary layer up to 40 km altitude. Atmospheric instabilities, which are clearly identified in the data, are used to gain further insight into possible atmospheric processes contributing to the excitation of gravity waves. [1] Creasey, J. E., et al.,(2006), Geophys. Res. Lett., 33, L01803, doi:10.1029/2005GL024037. [2]Tellmann, S., et al.(2013), J. Geophys. Res. Planets, 118, 306-320, doi:10.1002/jgre.20058. [3]Medvedev, A. S., et al.(2015), J. Geophys. Res. Planets, 120, 913-927. doi:10.1002/2015JE004802.[4] Barnes, J. R. (1990), J. Geophys. Res., 95, B2, 1401-1421. [5] Pätzold, M., et al. (2016), Planet. Space Sci., 127, 44 - 90.

  3. ORIGIN OF THE COMPLEX RADIO STRUCTURE IN BAL QSO 1045+352

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

    Kunert-Bajraszewska, Magdalena; Gawronski, Marcin P.; Janiuk, Agnieszka

    2010-08-01

    We present new, more sensitive, high-resolution radio observations of a compact broad absorption line (BAL) quasar, 1045+352, made with the EVN+MERLIN at 5 GHz. These observations allowed us to trace the connection between the arcsecond structure and the radio core of the quasar. The radio morphology of 1045+352 is dominated by a knotty jet showing several bends. We discuss possible scenarios that could explain such a complex morphology: galaxy merger, accretion disk instability, precession of the jet, and jet-cloud interactions. It is possible that we are witnessing an ongoing jet precession in this source due to internal instabilities within themore » jet flow; however, a dense environment detected in the submillimeter band and an outflowing material suggested by the X-ray absorption could strongly interact with the jet. It is difficult to establish the orientation between the jet axis and the observer in 1045+352 because of the complex structure. Nevertheless, taking into account the most recent inner radio structure, we conclude that the radio jet is oriented close to the line of sight, which can mean that the opening angle of the accretion disk wind can be large in this source. We also suggest that there is no direct correlation between the jet-observer orientation and the possibility of observing BALs.« less

  4. VLA Detects Unexplained Radio Emission From Three Brown Dwarfs

    NASA Astrophysics Data System (ADS)

    2005-01-01

    Astronomers have discovered three brown dwarfs -- enigmatic objects that are neither stars nor planets -- emitting radio waves that scientists cannot explain. The three newly-discovered radio-emitting brown dwarfs were found as part of a systematic study of nearby brown dwarfs using the National Science Foundation's Very Large Array (VLA) radio telescope. The VLA The Very Large Array CREDIT: NRAO/AUI/NSF (Click on image for VLA gallery) Until 2001, scientists believed that brown dwarfs, which are intermediate in mass between stars and planets, could not emit detectable amounts of radio waves. That year, summer students at the VLA made the first discovery of radio emission from a brown dwarf. Subsequently, as many as a half- dozen more radio-emitting brown dwarfs were discovered. "It clearly had become time to make a systematic study and try to find out just what percentage of brown dwarfs are emitting radio waves," said Rachel Osten, an astronomer at the National Radio Astronomy Observatory (NRAO) in Charlottesville, Virginia. Osten was assisted in the project in the summer of 2004 by Lynnae Quick, a student at North Carolina Agricultural and Technical State University; Tim Bastian, also an astronomer at NRAO; and Suzanne Hawley, an astronomer at the University of Washington. The research team presented their results to the American Astronomical Society's meeting in San Diego, CA. The three new detections of radio-emitting brown dwarfs are just the first results from the systematic study, which aims to observe all the known brown dwarfs within about 45 light-years of Earth. "We want to be able to say definitively just how common radio emission is among brown dwarfs," Osten explained. The study involves observing 65 individual brown dwarfs, so these new detections represent just the beginning of the results expected from the study. Brown dwarfs are too big to be planets but too small to be true stars, as they have too little mass to trigger hydrogen fusion reactions

  5. Solar Type II Radio Bursts and IP Type II Events

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    1992-01-01

    Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments and earth-based radio astronomical observations can be used to infer abundances of microwave absorbing atmospheric constituents in those atmospheres, as long as reliable information regarding the microwave absorbing properties of potential constituents is available. The use of theoretically derived microwave absorption properties for such atmospheric constituents, or using laboratory measurements of such properties under environmental conditions which are significantly different than those of the planetary atmosphere being studied, often leads to significant misinterpretation of available opacity data. The recognition of the need to make such laboratory measurements of simulated planetary atmospheres over a range of temperatures and pressures which correspond to the altitudes probed by both radio occultation experiments and radio astronomical observations, and over a range of frequencies which correspond to those used in both radio occultation experiments and radio astronomical observations, has led to the development of a facility at Georgia Tech which is capable of making such measurements. The goal of this investigation was to conduct such measurements and to apply the results to a wide range of planetary observations, both spacecraft and earth-based, in order to determine the identity and abundance profiles of constituents in those planetary atmospheres.

  7. Measurement of radio emission from extensive air showers with LOPES

    NASA Astrophysics Data System (ADS)

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

    2011-02-01

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

  8. A Deep Space Network Portable Radio Science Receiver

    NASA Technical Reports Server (NTRS)

    Jongeling, Andre P.; Sigman, Elliott H.; Chandra, Kumar; Trinh, Joseph T.; Navarro, Robert; Rogstad, Stephen P.; Goodhart, Charles E.; Proctor, Robert C.; Finley, Susan G.; White, Leslie A.

    2009-01-01

    The Radio Science Receiver (RSR) is an open-loop receiver installed in NASA s Deep Space Network (DSN), which digitally filters and records intermediate-frequency (IF) analog signals. The RSR is an important tool for the Cassini Project, which uses it to measure perturbations of the radio-frequency wave as it travels between the spacecraft and the ground stations, allowing highly detailed study of the composition of the rings, atmosphere, and surface of Saturn and its satellites.

  9. Observations of electron gyroharmonic waves and the structure of the Io torus. [jupiter 1 spacecraft radio astronomy experiment

    NASA Technical Reports Server (NTRS)

    Birmingham, T. J.; Alexander, J. K.; Desch, M. D.; Hubbard, R. F.; Pedersen, B. M.

    1980-01-01

    Narrow-banded emissions were observed by the Planetary Radio Astronomy experiment on the Voyager 1 spacecraft as it traversed the Io plasma torus. These waves occur between harmonics of the electron gyrofrequency and are the Jovian analogue of electrostatic emissions observed and theoretically studied for the terrestrial magnetosphere. The observed frequencies always include the component near the upper hybrid resonant frequency, (fuhr) but the distribution of the other observed emissions varies in a systematic way with position in the torus. A refined model of the electron density variation, based on identification of the fuhr line, is included. Spectra of the observed waves are analyzed in terms of the linear instability of an electron distribution function consisting of isotropic cold electrons and hot losscone electrons. The positioning of the observed auxiliary harmonics with respect to fuhr is shown to be an indicator of the cold to hot temperature ratio. It is concluded that this ratio increases systematically by an overall factor of perhaps 4 or 5 between the inner and outer portions of the torus.

  10. Design and construction of prototype radio antenna for shortest radio wavelengths

    NASA Technical Reports Server (NTRS)

    Leighton, R. B.

    1975-01-01

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

  11. Coherent perfect absorption in deeply subwavelength films in the single-photon regime

    PubMed Central

    Roger, Thomas; Vezzoli, Stefano; Bolduc, Eliot; Valente, Joao; Heitz, Julius J. F.; Jeffers, John; Soci, Cesare; Leach, Jonathan; Couteau, Christophe; Zheludev, Nikolay I.; Faccio, Daniele

    2015-01-01

    The technologies of heating, photovoltaics, water photocatalysis and artificial photosynthesis depend on the absorption of light and novel approaches such as coherent absorption from a standing wave promise total dissipation of energy. Extending the control of absorption down to very low light levels and eventually to the single-photon regime is of great interest and yet remains largely unexplored. Here we demonstrate the coherent absorption of single photons in a deeply subwavelength 50% absorber. We show that while the absorption of photons from a travelling wave is probabilistic, standing wave absorption can be observed deterministically, with nearly unitary probability of coupling a photon into a mode of the material, for example, a localized plasmon when this is a metamaterial excited at the plasmon resonance. These results bring a better understanding of the coherent absorption process, which is of central importance for light harvesting, detection, sensing and photonic data processing applications. PMID:25991584

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

    NASA Astrophysics Data System (ADS)

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

    2017-11-01

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

  13. The Deep Space Network as an instrument for radio science research

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  14. A Radio Astronomy Curriculum for STARLAB

    NASA Astrophysics Data System (ADS)

    Boltuch, D.; Hund, L.; Buck, S.; Fultz, C.; Smith, T.; Harris, R.; Castelaz, M. W.; Moffett, D.; LaFratta, M.; Walsh, L.

    2005-12-01

    We present elements of a curriculum that will accompany the STARLAB module "Sensing the Radio Sky" a portable planetarium program and projection of the radio sky. The curriculum will serve to familiarize high school students to a set of topics in radio astronomy. The curriculum includes lessons and activities addressing several topics related to radio astronomy and the Milky Way that consists of two main resources: a manual and a multimedia website. It is designed to accommodate a wide variety of possible uses and time constraints. The manufacturer of STARLAB, Learning Technologies, Inc. produces a short manual to accompany each presentation for the STARLAB. The "Sensing the Radio Sky" manual we have created includes the mandatory, minimum background information that students need to understand radio astronomy. It briefly discusses waves and electromagnetic radiation, similarities and differences between optical and radio astronomy, probable misconceptions about radio astronomy, how radio images are produced, synchrotron radiation in the Milky Way, and galactic coordinates. It also includes a script that presenters can choose to follow inside the STARLAB, a lesson plan for teachers, and activities for students to complete before and after the STARLAB experience that mirror the scientific method. The multimedia website includes more detailed information about electromagnetic radiation and a more detailed comparison of optical and radio astronomy. It also discusses the life cycles of stars, radiation from a variety of specific sources, and pulsars, as each relates to radio astronomy. The five highly detailed lessons are pulled together in sixth "overview lesson", intended for use by teachers who want to present more than the basic material in the manual, but do not have the classroom time to teach all five of the in-depth lessons. . We acknowledge support from the NSF Internship in Public Science Education Program grant number 0324729.

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

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

    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.

  16. Effects of the morphology of CIPs on microwave absorption behaviors

    NASA Astrophysics Data System (ADS)

    Woo, Soobin; Yoo, Chan-Sei; Kim, Hwijun; Lee, Mijung; Quevedo-Lopez, Manuel; Choi, Hyunjoo

    2017-11-01

    Electromagnetic (EM) wave absorption properties are affected by the thickness and surface area of absorbing materials. In this study, a facile ball-milling process was introduced to effectively reduce the diameter and increase the aspect ratio of carbonyl iron powder (CIP), which is one of the most commercially available EM-absorbing materials. The size, aspect ratio, and consequent surface area of CIP were manipulated by controlling the milling parameters to investigate their effects on EM absorption properties. The results indicated that ball-milled CIPs exhibited better EM wave absorption ability when compared with that of pristine CIPs. However, significant differences in minimum reflection loss values were not observed between CIPs with different morphologies and similar specific surface areas. Hence, both fine and flaky CIPs were considered as beneficial for EM wave absorption.[Figure not available: see fulltext.

  17. Crowd-Sourced Radio Science at Marshall Space Flight Center

    NASA Technical Reports Server (NTRS)

    Fry, C. D.; McTernan, J. K.; Suggs, R. M.; Rawlins, L.; Krause, L. H.; Gallagher, D. L.; Adams, M. L.

    2018-01-01

    August 21, 2017 provided a unique opportunity to investigate the effects of the total solar eclipse on high frequency (HF) radio propagation and ionospheric variability. In Marshall Space Flight Center's partnership with the US Space and Rocket Center (USSRC) and Austin Peay State University (APSU), we engaged citizen scientists and students in an investigation of the effects of an eclipse on the mid-latitude ionosphere. Activities included fieldwork and station-based data collection of HF Amateur Radio frequency bands and VLF radio waves before, during, and after the eclipse to build a continuous record of changing propagation conditions as the moon's shadow marched across the United States. Post-eclipse radio propagation analysis provided insights into ionospheric variability due to the eclipse.

  18. The puzzling case of the radio-loud QSO 3C 186: a gravitational wave recoiling black hole in a young radio source?

    NASA Astrophysics Data System (ADS)

    Chiaberge, M.; Ely, J. C.; Meyer, E. T.; Georganopoulos, M.; Marinucci, A.; Bianchi, S.; Tremblay, G. R.; Hilbert, B.; Kotyla, J. P.; Capetti, A.; Baum, S. A.; Macchetto, F. D.; Miley, G.; O'Dea, C. P.; Perlman, E. S.; Sparks, W. B.; Norman, C.

    2017-04-01

    Context. Radio-loud active galactic nuclei with powerful relativistic jets are thought to be associated with rapidly spinning black holes (BHs). BH spin-up may result from a number of processes, including accretion of matter onto the BH itself, and catastrophic events such as BH-BH mergers. Aims: We study the intriguing properties of the powerful (Lbol 1047 erg s-1) radio-loud quasar 3C 186. This object shows peculiar features both in the images and in the spectra. Methods: We utilize near-IR Hubble Space Telescope (HST) images to study the properties of the host galaxy, and HST UV and Sloan Digital Sky Survey optical spectra to study the kinematics of the source. Chandra X-ray data are also used to better constrain the physical interpretation. Results: HST imaging shows that the active nucleus is offset by 1.3 ± 0.1 arcsec (I.e. 11 kpc) with respect to the center of the host galaxy. Spectroscopic data show that the broad emission lines are offset by -2140 ± 390 km s-1 with respect to the narrow lines. Velocity shifts are often seen in QSO spectra, in particular in high-ionization broad emission lines. The host galaxy of the quasar displays a distorted morphology with possible tidal features that are typical of the late stages of a galaxy merger. Conclusions: A number of scenarios can be envisaged to account for the observed features. While the presence of a peculiar outflow cannot be completely ruled out, all of the observed features are consistent with those expected if the QSO is associated with a gravitational wave (GW) recoiling BH. Future detailed studies of this object will allow us to confirm this type of scenario and will enable a better understanding of both the physics of BH-BH mergers and the phenomena associated with the emission of GW from astrophysical sources.

  19. Exposure to radio-frequency electromagnetic waves alters acetylcholinesterase gene expression, exploratory and motor coordination-linked behaviour in male rats.

    PubMed

    Obajuluwa, Adejoke Olukayode; Akinyemi, Ayodele Jacob; Afolabi, Olakunle Bamikole; Adekoya, Khalid; Sanya, Joseph Olurotimi; Ishola, Azeez Olakunle

    2017-01-01

    Humans in modern society are exposed to an ever-increasing number of electromagnetic fields (EMFs) and some studies have demonstrated that these waves can alter brain function but the mechanism still remains unclear. Hence, this study sought to investigate the effect of 2.5 Ghz band radio-frequency electromagnetic waves (RF-EMF) exposure on cerebral cortex acetylcholinesterase (AChE) activity and their mRNA expression level as well as locomotor function and anxiety-linked behaviour in male rats. Animals were divided into four groups namely; group 1 was control (without exposure), group 2-4 were exposed to 2.5 Ghz radiofrequency waves from an installed WI-FI device for a period of 4, 6 and 8 weeks respectively. The results revealed that WiFi exposure caused a significant increase in anxiety level and affect locomotor function. Furthermore, there was a significant decrease in AChE activity with a concomitant increase in AChE mRNA expression level in WiFi exposed rats when compared with control. In conclusions, these data showed that long term exposure to WiFi may lead to adverse effects such as neurodegenerative diseases as observed by a significant alteration on AChE gene expression and some neurobehavioral parameters associated with brain damage.

  20. The Dynamic Radio Sky: Future Directions at cm/m-Wavelengths

    NASA Astrophysics Data System (ADS)

    Bower, Geoffrey C.; Cordes, J.; Croft, S.; Lazio, J.; Lorimer, D.; McLaughlin, M.

    2009-01-01

    The time domain of the radio wavelength sky has been only sparsely explored. Nevertheless, recent discoveries from limited surveys and serendipitous discoveries indicate that there is much to be found on timescales from nanoseconds to years and at wavelengths from meters to millimeters. These observations have revealed unexpected phenonmena such as rotating radio transients and coherent pulses from brown dwarfs. Additionally, archival studies have revealed an unknown class of radio transients without radio, optical, or high-energy hosts. The current generation of new meter- and centimeter-wave radio telescopes such as the MWA, LWA, PAPER, and ATA will exploit wide fields of view and flexible digital signal processing to systematically explore radio transient parameter space, as well as lay the scientific and technical foundation for the SKA. Known unknowns that will be the target of future transient surveys include orphan gamma-ray burst afterglows, radio supernovae, tidally-disrupted stars, flare stars, and magnetars.

  1. Investigation of the spatial structure and developmental dynamics of near-Earth plasma perturbations under the action of powerful HF radio waves

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

    Belov, A. S., E-mail: alexis-belov@yandex.ru

    2015-10-15

    Results of numerical simulations of the near-Earth plasma perturbations induced by powerful HF radio waves from the SURA heating facility are presented. The simulations were performed using a modified version of the SAMI2 ionospheric model for the input parameters corresponding to the series of in-situ SURA–DEMETER experiments. The spatial structure and developmental dynamics of large-scale plasma temperature and density perturbations have been investigated. The characteristic formation and relaxation times of the induced large-scale plasma perturbations at the altitudes of the Earth’s outer ionosphere have been determined.

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  3. An analytical theory of radio-wave scattering from meteoric ionization - I. Basic equation

    NASA Astrophysics Data System (ADS)

    Pecina, P.

    2016-01-01

    We have developed an analytical theory of radio-wave scattering from ionization of meteoric origin. It is based on an integro-differential equation for the polarization vector, P, inside the meteor trail, representing an analytical solution of the set of Maxwell equations, in combination with a generalized radar equation involving an integral of the trail volume electron density, Ne, and P represented by an auxiliary vector, Q, taken over the whole trail volume. During the derivation of the final formulae, the following assumptions were applied: transversal as well as longitudinal dimensions of the meteor trail are small compared with the distances of the relevant trail point to both the transmitter and receiver and the ratio of these distances to the wavelength of the wave emitted by the radar is very large, so that the stationary-phase method can be employed for evaluation of the relevant integrals. Further, it is shown that in the case of sufficiently low electron density, Ne, corresponding to the case of underdense trails, the classical McKinley's radar equation results as a special case of the general theory. The same also applies regarding the Fresnel characteristics. Our approach is also capable of yielding solutions to the problems of the formation of Fresnel characteristics on trails having any electron density, forward scattering and scattering on trails immersed in the magnetic field. However, we have also shown that the geomagnetic field can be removed from consideration, due to its low strength. The full solution of the above integro-differential equation, valid for any electron volume densities, has been left to subsequent works dealing with this particular problem, due to its complexity.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  5. Computationally Efficient Radio Frequency Source Localization for Radio Interferometric Arrays

    NASA Astrophysics Data System (ADS)

    Steeb, J.-W.; Davidson, David B.; Wijnholds, Stefan J.

    2018-03-01

    Radio frequency interference (RFI) is an ever-increasing problem for remote sensing and radio astronomy, with radio telescope arrays especially vulnerable to RFI. Localizing the RFI source is the first step to dealing with the culprit system. In this paper, a new localization algorithm for interferometric arrays with low array beam sidelobes is presented. The algorithm has been adapted to work both in the near field and far field (only the direction of arrival can be recovered when the source is in the far field). In the near field the computational complexity of the algorithm is linear with search grid size compared to cubic scaling of the state-of-the-art 3-D MUltiple SIgnal Classification (MUSIC) method. The new method is as accurate as 3-D MUSIC. The trade-off is that the proposed algorithm requires a once-off a priori calculation and storing of weighting matrices. The accuracy of the algorithm is validated using data generated by low-frequency array while a hexacopter was flying around it and broadcasting a continuous-wave signal. For the flight, the mean distance between the differential GPS positions and the corresponding estimated positions of the hexacopter is 2 m at a wavelength of 6.7 m.

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  8. Fish-Eye Observing with Phased Array Radio Telescopes

    NASA Astrophysics Data System (ADS)

    Wijnholds, S. J.

    The radio astronomical community is currently developing and building several new radio telescopes based on phased array technology. These telescopes provide a large field-of-view, that may in principle span a full hemisphere. This makes calibration and imaging very challenging tasks due to the complex source structures and direction dependent radio wave propagation effects. In this thesis, calibration and imaging methods are developed based on least squares estimation of instrument and source parameters. Monte Carlo simulations and actual observations with several prototype show that this model based approach provides statistically and computationally efficient solutions. The error analysis provides a rigorous mathematical framework to assess the imaging performance of current and future radio telescopes in terms of the effective noise, which is the combined effect of propagated calibration errors, noise in the data and source confusion.

  9. The effect of dissipative inhomogeneous medium on the statistics of the wave intensity

    NASA Technical Reports Server (NTRS)

    Saatchi, Sasan S.

    1993-01-01

    One of the main theoretical points in the theory of wave propagation in random medium is the derivation of closed form equations to describe the statistics of the propagating waves. In particular, in one dimensional problems, the closed form representation of the multiple scattering effects is important since it contributes in understanding such problems like wave localization, backscattering enhancement, and intensity fluctuations. In this the propagation of plane waves in a layer of one-dimensional dissipative random medium is considered. The medium is modeled by a complex permittivity whose real part is a constant representing the absorption. The one dimensional problem is mathematically equivalent to the analysis of a transmission line with randomly perturbed distributed parameters and a single mode lossy waveguide and the results can be used to study the propagation of radio waves through atmosphere and the remote sensing of geophysical media. It is assumed the scattering medium consists of an ensemble of one-dimensional point scatterers randomly positioned in a layer of thickness L with diffuse boundaries. A Poisson impulse process with density lambda is used to model the position of scatterers in the medium. By employing the Markov properties of this process an exact closed form equation of Kolmogorov-Feller type was obtained for the probability density of the reflection coefficient. This equation was solved by combining two limiting cases: (1) when the density of scatterers is small; and (2) when the medium is weakly dissipative. A two variable perturbation method for small lambda was used to obtain solutions valid for thick layers. These solutions are then asymptotically evaluated for small dissipation. To show the effect of dissipation, the mean and fluctuations of the reflected power are obtained. The results were compared with a lossy homogeneous medium and with a lossless inhomogeneous medium and the regions where the effect of absorption is not

  10. [INVITED] Coherent perfect absorption of electromagnetic wave in subwavelength structures

    NASA Astrophysics Data System (ADS)

    Yan, Chao; Pu, Mingbo; Luo, Jun; Huang, Yijia; Li, Xiong; Ma, Xiaoliang; Luo, Xiangang

    2018-05-01

    Electromagnetic (EM) absorption is a common process by which the EM energy is transformed into other kinds of energy in the absorber, for example heat. Perfect absorption of EM with structures at subwavelength scale is important for many practical applications, such as stealth technology, thermal control and sensing. Coherent perfect absorption arises from the interplay of interference and absorption, which can be interpreted as a time-reversed process of lasing or EM emitting. It provides a promising way for complete absorption in both nanophotonics and electromagnetics. In this review, we discuss basic principles and properties of a coherent perfect absorber (CPA). Various subwavelength structures including thin films, metamaterials and waveguide-based structures to realize CPAs are compared. We also discuss the potential applications of CPAs.

  11. Radiophysical methods of diagnostics the Earth's ionosphere and the underlying earth's surface by remote sensing in the short-wave range of radio waves

    NASA Astrophysics Data System (ADS)

    Belov, S. Yu.; Belova, I. N.

    2017-11-01

    Monitoring of the earth's surface by remote sensing in the short-wave band can provide quick identification of some characteristics of natural systems. This band range allows one to diagnose subsurface aspects of the earth, as the scattering parameter is affected by irregularities in the dielectric permittivity of subsurface structures. This method based on the organization of the monitoring probe may detect changes in these environments, for example, to assess seismic hazard, hazardous natural phenomena such as earthquakes, as well as some man-made hazards and etc. The problem of measuring and accounting for the scattering power of the earth's surface in the short-range of radio waves is important for a number of purposes, such as diagnosing properties of the medium, which is of interest for geological, environmental studies. In this paper, we propose a new method for estimating the parameters of incoherent signal/noise ratio. The paper presents the results of comparison of the measurement method from the point of view of their admissible relative analytical errors. The new method is suggested. Analysis of analytical error of estimation of this parameter allowed to recommend new method instead of standard method. A comparative analysis and shows that the analytical (relative) accuracy of the determination of this parameter new method on the order exceeds the widely-used standard method.

  12. 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)

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

    2013-04-01

    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.

  13. The CHIME Fast Radio Burst Project

    NASA Astrophysics Data System (ADS)

    Kaspi, Victoria M.; CHIME/FRB Collaboration

    2017-01-01

    Fast Radio Bursts are a recently discovered phenomenon consisting of short (few ms) bursts of radio waves that have dispersion measures that strongly suggest an extragalactic and possibly cosmological, but yetunknown, origin. The Canadian Hydrogen Intensity Mapping Experiment was designed to study Baryon Acoustic Oscillations through mapping of redshifted hydrogen, in order to constrain the nature of Dark Energy. CHIME, currently under construction in Penticton, BC in Canada, consists of 4 cylindrical paraboloid reflectors having total collecting area 80 m x 100 m, and will be sensitive in the 400-800 MHz band. With 2048 independent feeds hung along the cylinder axes, CHIME is a transit telescope with no moving parts, but is sensitive to the full ~200 sq. degrees overhead in 1024 formed beams, thanks to the largest correlator ever built. Given CHIME's enormous sensitivity, bandwidth and unprecedented field of view for the radio regime, CHIME will be a superb instrument for studying Fast Radio Bursts, with expected detected event rates of several to several dozen per day, hence promising major progress on the origin and nature of FRBs.

  14. The damping of seismic waves and its determination from reflection seismograms

    NASA Technical Reports Server (NTRS)

    Engelhard, L.

    1979-01-01

    The damping in theoretical waveforms is described phenomenologically and a classification is proposed. A method for studying the Earth's crust was developed which includes this damping as derived from reflection seismograms. Seismic wave propagation by absorption, attenuation of seismic waves by scattering, and dispersion relations are considered. Absorption of seismic waves within the Earth as well as reflection and transmission of elastic waves seen through boundary layer absorption are also discussed.

  15. Laboratory Evaluation and Application of Microwave Absorption Properties Under Simulated Conditions for Planetary Atmospheres

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    1998-01-01

    Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments, entry probe radio signal absorption measurements, and earth-based radio astronomical observations can be used to infer abundances of microwave absorbing constituents in those atmospheres, as long as reliable information regarding the microwave absorbing properties of potential constituents is available. The use of theoretically-derived microwave absorption properties for such atmospheric constituents, or using laboratory measurements of such properties taken under environmental conditions which are significantly different than those of the planetary atmosphere being studied, often leads to significant misinterpretation of available opacity data. For example, laboratory measurements completed recently by Kolodner and Steffes (ICARUS 132, pp. 151-169, March 1998, attached as Appendix A) under this grant (NAGS-4190), have shown that the opacity from gaseous H2SO4 under simulated Venus conditions is best described by a different formalism than was previously used. The recognition of the need to make such laboratory measurements of simulated planetary atmospheres over a range of temperatures and pressures which correspond to the altitudes probed by both spacecraft entry probe and orbiter radio occultation experiments and by radio astronomical observations, and over a range of frequencies which correspond to those used in such experiments, has led to the development of a facility at Georgia Tech which is capable of making such measurements. It has been the goal of this investigation to conduct such measurements and to apply the results to a wide range of planetary observations, both spacecraft and earth-based, in order to determine the identity and abundance profiles of constituents in those planetary atmospheres.

  16. A radio counterpart to a neutron star merger

    NASA Astrophysics Data System (ADS)

    Hallinan, G.; Corsi, A.; Mooley, K. P.; Hotokezaka, K.; Nakar, E.; Kasliwal, M. M.; Kaplan, D. L.; Frail, D. A.; Myers, S. T.; Murphy, T.; De, K.; Dobie, D.; Allison, J. R.; Bannister, K. W.; Bhalerao, V.; Chandra, P.; Clarke, T. E.; Giacintucci, S.; Ho, A. Y. Q.; Horesh, A.; Kassim, N. E.; Kulkarni, S. R.; Lenc, E.; Lockman, F. J.; Lynch, C.; Nichols, D.; Nissanke, S.; Palliyaguru, N.; Peters, W. M.; Piran, T.; Rana, J.; Sadler, E. M.; Singer, L. P.

    2017-12-01

    The gravitational wave event GW170817 was caused by the merger of two neutron stars (see the Introduction by Smith). In three papers, teams associated with the GROWTH (Global Relay of Observatories Watching Transients Happen) project present their observations of the event at wavelengths from x-rays to radio waves. Evans et al. used space telescopes to detect GW170817 in the ultraviolet and place limits on its x-ray flux, showing that the merger generated a hot explosion known as a blue kilonova. Hallinan et al. describe radio emissions generated as the explosion slammed into the surrounding gas within the host galaxy. Kasliwal et al. present additional observations in the optical and infrared and formulate a model for the event involving a cocoon of material expanding at close to the speed of light, matching the data at all observed wavelengths.

  17. Detection of Transionospheric SuperDARN HF Waves by the Radio Receiver Instrument on the enhanced Polar Outflow Probe Satellite

    NASA Astrophysics Data System (ADS)

    Gillies, R. G.; Yau, A. W.; James, H. G.; Hussey, G. C.; McWilliams, K. A.

    2014-12-01

    The enhanced Polar Outflow Probe (ePOP) Canadian small-satellite was launched in September 2013. Included in this suite of eight scientific instruments is the Radio Receiver Instrument (RRI). The RRI has been used to measure VLF and HF radio waves from various ground and spontaneous ionospheric sources. The first dedicated ground transmission that was detected by RRI was from the Saskatoon Super Dual Auroral Radar Network (SuperDARN) radar on Nov. 7, 2013 at 14 MHz. Several other passes over the Saskatoon SuperDARN radar have been recorded since then. Ground transmissions have also been observed from other radars, such as the SPEAR, HAARP, and SURA ionospheric heaters. However, the focus of this study will be on the results obtained from the SuperDARN passes. An analysis of the signal recorded by the RRI provides estimates of signal power, Doppler shift, polarization, absolute time delay, differential mode delay, and angle of arrival. By comparing these parameters to similar parameters derived from ray tracing simulations, ionospheric electron density structures may be detected and measured. Further analysis of the results from the other ground transmitters and future SuperDARN passes will be used to refine these results.

  18. Illuminating Gravitational Waves

    NASA Astrophysics Data System (ADS)

    Kasliwal, Mansi; GROWTH (Global Relay of Observatories Watching Transients Happen) Team

    2018-01-01

    On August 17 2017, for the first time, an electromagnetic counterpart to gravitational waves was detected. Two neutron stars merged and lit up the entire electromagnetic spectrum, from gamma-rays to the radio. The infrared signature vividly demonstrates that neutron star mergers are indeed the long-sought production sites that forge heavy elements by r-process nucleosynthesis. The weak gamma-rays are dissimilar to classical short gamma-ray bursts with ultra-relativistic jets. Instead, by synthesizing a panchromatic dataset, we suggest that break-out of a wide-angle, mildly-relativistic cocoon engulfing the jet elegantly explains the low-luminosity gamma-rays, the high-luminosity ultraviolet-optical-infrared and the delayed radio/X-ray emission. I conclude with the promise of a literally bright and loud future, thanks to even more sensitive survey telescopes and gravitational wave interferometers.

  19. Anomalous Radio-Wave Scattering from Interstellar Plasma Structures

    DTIC Science & Technology

    2001-03-10

    broadening time from the usually expected l~4 scaling law. We brieÑy discuss applications that include scattering of pulses from the Crab pulsar by... pulsars : general È scattering 1. INTRODUCTION Images of scattered radio sources and distorted pulses from pulsars provide some of the most used...distribution of di†racting irregu- larities. Third, observations of the Crab pulsar show anomalous scalings of pulse broadening with frequency. These are

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

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

  1. Interband absorption strength in long-wave infrared type-II superlattices with small and large superlattice periods compared to bulk materials

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

    Vurgaftman, I.; Belenky, G., E-mail: gregory.belenky@stonybrook.edu; Lin, Y.

    The absorption spectra for the antimonide-based type-II superlattices (SLs) for detection in the long-wave infrared (LWIR) are calculated and compared to the measured data for SLs and bulk materials with the same energy gap (HgCdTe and InAsSb). We include the results for the metamorphic InAsSb{sub x}/InAsSb{sub y} SLs with small periods as well as the more conventional strain-balanced InAs/Ga(In)Sb and InAs/InAsSb SLs on GaSb substrates. The absorption strength in small-period metamorphic SLs is similar to the bulk materials, while the SLs with an average lattice constant matched to GaSb have significantly lower absorption. This is because the electron-hole overlap inmore » the strain-balanced type-II LWIR SLs occurs primarily in the hole well, which constitutes a relatively small fraction of the total thickness.« less

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

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

  3. DIFFUSIVE SHOCK ACCELERATION SIMULATIONS OF RADIO RELICS

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

    Kang, Hyesung; Ryu, Dongsu; Jones, T. W., E-mail: kang@uju.es.pusan.ac.kr, E-mail: ryu@canopus.cnu.ac.kr, E-mail: twj@msi.umn.edu

    2012-09-01

    Recent radio observations have identified a class of structures, so-called radio relics, in clusters of galaxies. The radio emission from these sources is interpreted as synchrotron radiation from GeV electrons gyrating in {mu}G-level magnetic fields. Radio relics, located mostly in the outskirts of clusters, seem to associate with shock waves, especially those developed during mergers. In fact, they seem to be good structures to identify and probe such shocks in intracluster media (ICMs), provided we understand the electron acceleration and re-acceleration at those shocks. In this paper, we describe time-dependent simulations for diffusive shock acceleration at weak shocks that aremore » expected to be found in ICMs. Freshly injected as well as pre-existing populations of cosmic-ray (CR) electrons are considered, and energy losses via synchrotron and inverse Compton are included. We then compare the synchrotron flux and spectral distributions estimated from the simulations with those in two well-observed radio relics in CIZA J2242.8+5301 and ZwCl0008.8+5215. Considering that CR electron injection is expected to be rather inefficient at weak shocks with Mach number M {approx}< a few, the existence of radio relics could indicate the pre-existing population of low-energy CR electrons in ICMs. The implication of our results on the merger shock scenario of radio relics is discussed.« less

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

    PubMed

    Larsen, Jerrie A; Overstreet, Julia

    2008-01-01

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

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

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

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

    1961-07-01

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

  6. Coincident bursts of auroral kilometric radiation and VLF emissions associted with a type 3 solar radio noise event

    NASA Technical Reports Server (NTRS)

    Rosenberg, T. J.; Singh, S.; Wu, C. S.; Labelle, J.; Treumann, R. A.; Inan, U. S.; Lanzerotti, L. J.

    1995-01-01

    This paper examines an isolated magnetospheric VLF/radio noise event that is highly suggestive of the triggering of terrestrial auroral kilometric radiation (AKR) bu solar type III radio emission and of a close relation between AKR and broadband hiss. The solar type III burst was measured on polar HF riometers and was coincident with local dayside VLF/LF noise emission bursts at South Pole station. It was also coincident with AKR bursts detected onthe AMPTE/IRM satellite, at the same magnetic local time as South Pole. On the basis of the close association of AKR and VLF bursts, and from geometric considerations relating to wave propagation, it is likely that the AKR source was on the dayside and on field lines near South Pole station. The general level of geomagnetic activity was very low. However, an isolated magnetic impulse event (MIE) accompanied by a riometer absorption pulse was in progress when all of the VLF/radio noise bursts occurred. The very close association of the typew III burst at HF with the AKR is consistent with external stimulation of the AKR, is different, more immediate,triggering process than that implied by Calvert (1981) is invoked. It is suggested here that some of the HF solar radiant energy may decay into waves with frequences comparable to those of the AKR by paraetric excitation or some other process, thus providing the few background photons required for the generation of AKR by the WU and Lee (1979) cyclotron maser instability. The AKR, perhaps by modifying the magnetospheric electron velocity distribution, might have produced the observed VLF emissions. Alternatively, the VLF emissions may have arisen from the same anisotropic and unstable electron distribution function responsible for the AKR.

  7. Status of the radio technique for cosmic-ray induced air showers

    NASA Astrophysics Data System (ADS)

    Schröder, Frank G.

    2016-10-01

    Radio measurements yield calorimetric information on the electromagnetic shower component around the clock. However, until recently it was not clear whether radio measurements can compete in accuracy with established night-time techniques like air-Cherenkov or air-fluorescence detection. Due to recent progress in the radio technique as well as in the understanding of the emission mechanisms, the performance of current radio experiments has significantly improved. Above 100 PeV, digital, state-of-the-art antenna arrays achieve a reconstruction accuracy for the energy similar to that of other techniques, and can provide an independent measurement of the absolute energy scale. Furthermore, radio measurements are sensitive to the mass composition of the primary particles: First, the position of the shower maximum can be reconstructed from the radio signal. Second, in combination with muon detectors the measurement of the electromagnetic component provides complementary information on the primary mass. Since the radio footprint is huge for inclined showers, and the radio signal does not suffer absorption in the atmosphere, future radio arrays either focus on inclined showers at the highest energy, or on ultra-high precision measurements with extremely dense arrays. This proceeding reviews the current status of radio experiments and simulations as well as future plans.

  8. Subbarrier absorption in a stationary superlattice

    NASA Technical Reports Server (NTRS)

    Arutyunyan, G. M.; Nerkararyan, K. V.

    1984-01-01

    The calculation of the interband absorption coefficient was carried out in the classical case, when the frequency of light was assumed to bind two miniband subbarrier states of different bands. The influence of two dimensional Mott excitons on this absorption was studied and a comparison was made with the experiment. All of these considerations were done taking into account the photon wave vector (the phase spatial heterogeneity). The basic traits of the energy spectra of superlattice semiconductors, their kinetic and optical properties, and possible means of electromagnetic wave intensification were examined. By the density matrix method, a theory of electrical and electromagnetic properties of superlattices was suggested.

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

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

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

    2006-07-12

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

  10. The role of depressed metabolism in increased radio resistance

    NASA Technical Reports Server (NTRS)

    Musacchia, X. J.

    1972-01-01

    Studies are presented of the physiology of depressed metabolism, radio-resistance in depressed metabolic states, comparative aspects of depressed metabolism, and gastrointestinal responses to ionizing radiation. Specific data cover helium-cold induced hypothermia in white rats and hamsters, and radiation responses and intestinal absorption in the gerbil.

  11. Properties of Langmuir wave bursts associated with magnetic holes

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  12. A Novel Cost-effective OFDM WDM-PON Radio Over Fiber System Employing FBG to Generate Optical mm-wave

    NASA Astrophysics Data System (ADS)

    Nguyen, HoangViet

    2015-03-01

    We have investigated and demonstrated a novel scheme to generate 2.5 Gbit/s 64 QAM orthogonal frequency division multiplexing (OFDM) signals for Radio Over Fiber (ROF) systems. We employ Fiber Bragg Grating (FBG) because the repetitive frequency of the RF source and the bandwidth of the optical modulator are largely reduced and the architecture of the ROF system is simpler. Wavelength-Division-Multiplexed Passive Optical Network (WDM-PON) has been considered as a promising solution for future broadband access networks. Principle of WDM-PON access network compatible with OFDM-ROF systems is investigated. This novel scheme which has multiple double-frequency technique to generate mm-wave signal to carry OFDM signals is a practical scheme to be applied for future broadband access networks.

  13. Radio interferometry: Techniques for Geodesy. [conference

    NASA Technical Reports Server (NTRS)

    1980-01-01

    Progress in the development and application of radio interferometry as a tool for geophysical research is reported and discussed. Among the topics reviewed are: Surveys of is the Seventies, Movements, Terrestrial and Celestial, Degrees Kelvin and Degrees of Phase, the Mark 3 VLBI System, Waves of the Future and other Emissions, and Adherence and Coherence in Networks, and Plans.

  14. Dynamic Leidenfrost temperature on micro-textured surfaces: Acoustic wave absorption into thin vapor layer

    NASA Astrophysics Data System (ADS)

    Jerng, Dong Wook; Kim, Dong Eok

    2018-01-01

    The dynamic Leidenfrost phenomenon is governed by three types of pressure potentials induced via vapor hydrodynamics, liquid dynamic pressure, and the water hammer effect resulting from the generation of acoustic waves at the liquid-vapor interface. The prediction of the Leidenfrost temperature for a dynamic droplet needs quantitative evaluation and definition for each of the pressure fields. In particular, the textures on a heated surface can significantly affect the vapor hydrodynamics and the water hammer pressure. We present a quantitative model for evaluating the water hammer pressure on micro-textured surfaces taking into account the absorption of acoustic waves into the thin vapor layer. The model demonstrates that the strength of the acoustic flow into the liquid droplet, which directly contributes to the water hammer pressure, depends on the magnitude of the acoustic resistance (impedance) in the droplet and the vapor region. In consequence, the micro-textures of the surface and the increased spacing between them reduce the water hammer coefficient ( kh ) defined as the ratio of the acoustic flow into the droplet to total generated flow. Aided by numerical calculations that solve the laminar Navier-Stokes equation for the vapor flow, we also predict the dynamic Leidenfrost temperature on a micro-textured surface with reliable accuracy consistent with the experimental data.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  16. Waves in Motion

    NASA Astrophysics Data System (ADS)

    McGourty, L.; Rideout, K.

    2005-12-01

    "Waves in Motion" This teaching unit was created by Leslie McGourty and Ken Rideout under the Research Experience for Teachers (RET) program at MIT Haystack Observatory during the summer of 2005. The RET program is funded by a grant from the National Science Foundation. The goals of this teaching unit are to deepen students' understanding about waves, wave motion, and the electromagnetic spectrum as a whole. Specifically students will comprehend the role radio waves play in our daily lives and in the investigation of the universe. The lessons can be used in a high school physics, earth science or astronomy curriculum. The unit consists of a series of interlocking lectures, activities, and investigations that can be used as stand alone units to supplement a teacher's existing curriculum, as an independent investigation for a student, or as a long exploration into radio astronomy with a theme of waves in space: how and where they carry their information. Special emphasis is given to the Relativity theories in honor of the "World Year of Physics" to celebrate Einstein's 1905 contributions. The lessons are currently being implemented at the high school level, the preliminary results of which will be presented. At the end of the academic year, the units will be evaluated and updated, reflecting student input and peer review after which they will be posted on the internet for teachers to use in their classrooms.

  17. Thomson Thick X-Ray Absorption in a Broad Absorption Line Quasar, PG 0946+301.

    PubMed

    Mathur; Green; Arav; Brotherton; Crenshaw; deKool; Elvis; Goodrich; Hamann; Hines; Kashyap; Korista; Peterson; Shields; Shlosman; van Breugel W; Voit

    2000-04-20

    We present a deep ASCA observation of a broad absorption line quasar (BALQSO) PG 0946+301. The source was clearly detected in one of the gas imaging spectrometers, but not in any other detector. If BALQSOs have intrinsic X-ray spectra similar to normal radio-quiet quasars, our observations imply that there is Thomson thick X-ray absorption (NH greater, similar1024 cm-2) toward PG 0946+301. This is the largest column density estimated so far toward a BALQSO. The absorber must be at least partially ionized and may be responsible for attenuation in the optical and UV. If the Thomson optical depth toward BALQSOs is close to 1, as inferred here, then spectroscopy in hard X-rays with large telescopes like XMM would be feasible.

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  19. Indoor radio measurement and planning for UMTS/HSDPA with antennas

    NASA Astrophysics Data System (ADS)

    Eheduru, Marcellinus

    Over the last decade, mobile communication networks have evolved tremendously with a key focus on providing high speed data services in addition to voice. The third generation of mobile networks in the form of Universal Mobile Telecommunications System (UMTS) is already offering revolutionary mobile broadband experience to its users by deploying High Speed Downlink Packet Access (HSDPA) as its packet-data technology. With data speeds up to 14.4 Mbps and ubiquitous mobility, HSDPA is anticipated to become a preferred broadband access medium for end-users via mobile phones, laptops etc. While majority of these end-users are located indoors most of the time, approximately 70-80% of the HSDPA traffic is estimated to originate from inside buildings. Thus for network operators, indoor coverage has become a necessity for technical and business reasons. Macro-cellular (outdoor) to indoor coverage is a natural inexpensive way of providing network coverage inside the buildings. However, it does not guarantee sufficient link quality required for optimal HSDPA operation. On the contrary, deploying a dedicated indoor system may be far too expensive from an operator's point of view. In this thesis, the concept is laid for the understanding of indoor radio wave propagation in a campus building environment which could be used to plan and improve outdoor-to-indoor UMTS/HSDPA radio propagation performance. It will be shown that indoor range performance depends not only on the transmit power of an indoor antenna, but also on the product's response to multipath and obstructions in the environment along the radio propagation path. An extensive measurement campaign will be executed in different indoor environments analogous to easy, medium and hard radio conditions. The effects of walls, ceilings, doors and other obstacles on measurement results would be observed. Chapter one gives a brief introduction to the evolution of UMTS and HSDPA. It goes on to talk about radio wave propagation

  20. Radio evidence for shock acceleration of electrons in the solar corona

    NASA Technical Reports Server (NTRS)

    Cane, H. V.; Stone, R. G.; Fainberg, J.; Steinberg, J. L.; Hoang, S.; Stewart, R. T.

    1981-01-01

    It is pointed out that the new class of kilometer-wavelength solar radio bursts observed with the ISEE-3 Radio Astronomy Experiment occurs at the reported times of type II events, which are indicative of a shock wave. An examination of records from the Culgoora Radio Observatory reveals that the associated type II bursts have fast drift elements emanating from them; that is, a herringbone structure is formed. It is proposed that this new class of bursts is a long-wavelength continuation of the herringbone structure, and it is thought probable that the electrons producing the radio emission are accelerated by shocks. These new events are referred to as shock-accelerated events, and their characteristics are discussed.

  1. Laboratory Evaluation and Application of Microwave Absorption Properties Under Simulated Conditions for Planetary Atmospheres

    NASA Technical Reports Server (NTRS)

    Steffes, Paul G.

    1997-01-01

    Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments and earth-based radio astronomical observations can be used to infer abundances of microwave absorbing constituents in those atmospheres, as long as reliable information regarding the microwave absorbing properties of potential constituents is available. The use of theoretically-derived microwave absorption properties for such atmospheric constituents, or using laboratory measurements of such properties under environmental conditions which are significantly different than those of the planetary atmosphere being studied, often leads to significant misinterpretation of available opacity data. Laboratory measurements completed under this grant (NAGW-533), have shown that the opacity from, SO2 under simulated Venus conditions is best described by a different lineshape than was previously used in theoretical predictions. The recognition of the need to make such laboratory measurements of simulated planetary atmospheres over a range of temperatures and pressures which correspond to the altitudes probed by both radio occultation experiments and radio astronomical observations, and over a range of frequencies which correspond to those used in both radio occultation experiments and radio astronomical observations, has led to the development of a facility at Georgia Tech which is capable of making such measurements. It has been the goal of this investigation to conduct such measurements and to apply the results to a wide range of planetary observations, both spacecraft and earth-based, in order to determine the identity and abundance profiles of constituents in those planetary atmospheres.

  2. Lunar Radio_phase Ranging in Chinese Lunar Lander Mission for Astrometry

    NASA Astrophysics Data System (ADS)

    Ping, Jinsong; Meng, Qiao; Li, Wenxiao; Wang, Mingyuan; Wang, Zhen; Zhang, Tianyi; Han, Songtao

    2015-08-01

    The radio tracking data in lunar and planetary missions can be directly applied for scientific investigation. The variations of phase and of amplitude of the radio carrier wave signal linked between the spacecraft and the ground tracking antenna are used to deduce the planetary atmospheric and ionospheric structure, planetary gravity field, mass, ring, ephemeris, and even to test the general relativity. In the Chinese lunar missions, we developed the lunar and planetary radio science receiver to measure the distance variation between the tracking station-lander by means of open loop radio phase tracking. Using this method in Chang’E-3 landing mission, a lunar radio_phase ranging (LRR) technique was realized at Chinese deep space tracking stations and astronomical VLBI stations with H-maser clocks installed. Radio transponder and transmitter had been installed on the Chang’E-3/4. Transponder will receive the uplink S/X band radio wave transmitted from the two newly constructed Chinese deep space stations, where the high quality hydrogen maser atomic clocks have been used as local time and frequency standard. The clocks between VLBI stations and deep space stations can be synchronized to UTC standard within 20 nanoseconds using satellite common view methods. In the near future there will be a plan to improve this accuracy to 5 nanoseconds or better, as the level of other deep space network around world. In the preliminary LRR experiments of Chang'E-3, the obtained 1sps phase ranging observables have a resolution of 0.2 millimeter or better, with a fitting RMS about 2~3 millimeter, after the atmospheric and ionospheric errors removed. This method can be a new astrometric technique to measure the Earth tide and rotation, lunar orbit, tides and liberation, by means of solo observation or of working together with Lunar Laser Ranging. After differencing the ranging, we even obtained 1sps doppler series of 2-way observables with resolution of 0.07mm/second, which can

  3. Dispersive Evolution of Nonlinear Fast Magnetoacoustic Wave Trains

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

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

    2017-10-01

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

  4. Nonlinear, relativistic Langmuir waves in astrophysical magnetospheres

    NASA Technical Reports Server (NTRS)

    Chian, Abraham C.-L.

    1987-01-01

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

  5. Advances in solar radio astronomy

    NASA Technical Reports Server (NTRS)

    Kundu, M. R.

    1982-01-01

    The status of the observations and interpretations of the sun's radio emission covering the entire radio spectrum from millimeter wavelengths to hectometer and kilometer wavelengths is reviewed. Emphasis is given to the progress made in solar radio physics as a result of recent advances in plasma and radiation theory. It is noted that the capability now exists of observing the sun with a spatial resolution of approximately a second of arc and a temporal resolution of about a millisecond at centimeter wavelengths and of obtaining fast multifrequency two-dimensional pictures of the sun at meter and decameter wavelengths. A summary is given of the properties of nonflaring active regions at millimeter, centimeter, and meter-decameter wavelengths. The properties of centimeter wave bursts are discussed in connection with the high spatial resolution observations. The observations of the preflare build-up of an active region are reviewed. High spatial resolution observations (a few seconds of arc to approximately 1 arcsec) are discussed, with particular attention given to the one- and two-dimensional maps of centimeter-wavelength burst sources.

  6. Absorption of sound by tree bark

    Treesearch

    G. Reethof; L. D. Frank; O. H. McDaniel

    1976-01-01

    Laboratory tests were conducted with a standing wave tube to measure the acoustic absorption of normally incident sound by the bark of six species of trees. Twelve bark samples, 10 cm in diameter, were tested. Sound of seven frequencies between 400 and 1600 Hz was used in the measurements. Absorption was generally about 5 percent; it exceeded 10 percent for only three...

  7. In-situ growth of AuNPs on WS2@U-bent optical fiber for evanescent wave absorption sensor

    NASA Astrophysics Data System (ADS)

    Zhang, Suzhen; Zhao, Yuefeng; Zhang, Chao; Jiang, Shouzhen; Yang, Cheng; Xiu, Xianwu; Li, Chonghui; Li, Zhen; Zhao, Xiaofei; Man, Baoyuan

    2018-05-01

    The sensitivity of the evanescent wave absorption sensor is always a hot topic which has been attracted researchers' discussion. It is still a challenge for developing the effective sensor to sensitively detect some biochemical molecules solution in a simple and low-cost way. In this paper, an evanescent wave absorption (EWA) sensor has been presented based on the U-bent multimode fiber coated with tungsten disulfide (WS2) film and in-situ growth of gold nanoparticles (AuNPs) for the detection of ethanol solution and sodium chloride (NaCl) solution. Benefitted from the effective light coupling produced between U-bent probe and AuNPs, we attained the optimal size of the AuNPs by changing the reaction time between WS2 and tetrachloroauric acid (HAuCl4). With the AuNPs/WS2@U-bent optical fiber, we discussed the behaviors of EWA sensor, such as sensitivity, reproducibility, fast response-recovery time and stability. The sensitivity (△A/△C) of the proposed AuNPs/WS2@U-bent optical fiber EWA sensor is 0.65 for the detection of the ethanol solution. Besides, the AuNPs/WS2@U-bent optical fiber EWA sensor exhibits high sensitivity in detection of the sodium chloride (NaCl), which can reach 1.5 when the proposed sensor was immersed into NaCl solution. Our work demonstrates that the U-bent optical fiber EWA sensor may have promising applications in testing the solution of concentration.

  8. The Radio Plasma Imager Investigation on the IMAGE Spacecraft

    NASA Technical Reports Server (NTRS)

    Reinisch, Bodo W.; Haines, D. M.; Bibl, K.; Cheney, G.; Galkin, I. A.; Huang, X.; Myers, S. H.; Sales, G. S.; Benson, R. F.; Fung, S. F.

    1999-01-01

    Radio plasma imaging uses total reflection of electromagnetic waves from plasmas whose plasma frequencies equal the radio sounding frequency and whose electron density gradients are parallel to the wave normals. The Radio Plasma Imager (RPI) has two orthogonal 500-m long dipole antennas in the spin plane for near omni-directional transmission. The third antenna is a 20-m dipole. Echoes from the magnetopause, plasmasphere and cusp will be received with three orthogonal antennas, allowing the determination of their angle-of-arrival. Thus it will be possible to create image fragments of the reflecting density structures. The instrument can execute a large variety of programmable measuring programs operating at frequencies between 3 kHz and 3 MHz. Tuning of the transmit antennas provides optimum power transfer from the 10 W transmitter to the antennas. The instrument can operate in three active sounding modes: (1) remote sounding to probe magnetospheric boundaries, (2) local (relaxation) sounding to probe the local plasma, and (3) whistler stimulation sounding. In addition, there is a passive mode to record natural emissions, and to determine the local electron density and temperature by using a thermal noise spectroscopy technique.

  9. A New Peak of Leonids observed by Radio Technics

    NASA Astrophysics Data System (ADS)

    Suzuki, K.; Maegawa, K.; Minagawa, Y.

    Radio meteor observations with amateur ham radio wave have been carried out in Japan since August, 1996, by using forward-scattered meteor echoes of VHF radio waves (53.75MHz, 50W, CW) transmitted in Sabae, Fukui prefecture. A strong activity of Leonids was observed between 22h and 01h on November 16/17 (UT), 1996. The hourly rate of long duration echoes reached over 50 times larger than in non-shower period and 1.2 to 1.5 times larger than that at the normal maximum of Leonids, respectively. This enhanced activity occurred at a solar longitude (SL) of 234.95 plus or minus 0.05 degrees (2000.0 eq.), and is probably different from normal peak of Leonids at 235.45 plus or minus 0.05 degrees(2000.0 eq.) observed in 1990's. A corresponding peak in 1995 was also reported by visual meteor observation by many observers in Japan. The ascending node of Comet Tempel-Tuttle in 1966 was at 235.11 degrees in SL, and is closer to the new peak than the normal one (at 235.45 degrees in SL).

  10. Seismic signatures of carbonate caves affected by near-surface absorptions

    NASA Astrophysics Data System (ADS)

    Rao, Ying; Wang, Yanghua

    2015-12-01

    The near-surface absorption within a low-velocity zone generally has an exponential attenuation effect on seismic waves. But how does this absorption affect seismic signatures of karstic caves in deep carbonate reservoirs? Seismic simulation and analysis reveals that, although this near-surface absorption attenuates the wave energy of a continuous reflection, it does not alter the basic kinematic shape of bead-string reflections, a special seismic characteristic associated with carbonate caves in the Tarim Basin, China. Therefore, the bead-strings in seismic profiles can be utilized, with a great certainty, for interpreting the existence of caves within the deep carbonate reservoirs and for evaluating their pore spaces. Nevertheless, the difference between the central frequency and the peak frequency is increased along with the increment in the absorption. While the wave energy of bead-string reflections remains strong, due to the interference of seismic multiples generated by big impedance contrast between the infill materials of a cave and the surrounding carbonate rocks, the central frequency is shifted linearly with respect to the near-surface absorption. These two features can be exploited simultaneously, for a stable attenuation analysis of field seismic data.

  11. 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)

    Schmitter, E. D.

    2014-11-01

    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.

  12. Planetary radio astronomy: Earth, giant planets, and beyond

    NASA Astrophysics Data System (ADS)

    Rucker, H. O.; Panchenko, M.; Weber, C.

    2014-11-01

    The magnetospheric phenomenon of non-thermal radio emission is known since the serendipitous discovery of Jupiter as radio planet in 1955, opening the new field of "Planetary Radio Astronomy". Continuous ground-based observations and, in particular, space-borne measurements have meanwhile produced a comprehensive picture of a fascinating research area. Space missions as the Voyagers to the Giant Planets, specifically Voyager 2 further to Uranus and Neptune, Galileo orbiting Jupiter, and now Cassini in orbit around Saturn since July 2004, provide a huge amount of radio data, well embedded in other experiments monitoring space plasmas and magnetic fields. The present paper as a condensation of a presentation at the Kleinheubacher Tagung 2013 in honour of the 100th anniversary of Prof. Karl Rawer, provides an introduction into the generation mechanism of non-thermal planetary radio waves and highlights some new features of planetary radio emission detected in the recent past. As one of the most sophisticated spacecraft, Cassini, now in space for more than 16 years and still in excellent health, enabled for the first time a seasonal overview of the magnetospheric variations and their implications for the generation of radio emission. Presently most puzzling is the seasonally variable rotational modulation of Saturn kilometric radio emission (SKR) as seen by Cassini, compared with early Voyager observations. The cyclotron maser instability is the fundamental mechanism under which generation and sufficient amplification of non-thermal radio emission is most likely. Considering these physical processes, further theoretical investigations have been started to investigate the conditions and possibilities of non-thermal radio emission from exoplanets, from potential radio planets in extrasolar systems.

  13. Radio and white-light observations of coronal transients

    NASA Technical Reports Server (NTRS)

    Dulk, G. A.

    1980-01-01

    Optical, radio and X-ray evidence of violent mass motions in the corona has existed for some years but only recently have the form, nature, frequency and implication of the transients become obvious. In this paper the observed properties of coronal transients are reviewed, with concentration on the white-light and radio manifestations. The classification according to speeds seems to be meaningful, with the slow transients having thermal emissions at radio wavelengths and the fast ones nonthermal. The possible mechanisms involved in the radio bursts are then discussed and estimates of various forms of energy are reviewed. It appears that the magnetic energy transported from the sun by the transient exceeds that of any other form, and that magnetic forces dominate in the dynamics of the motions. The conversion of magnetic energy into mechanical energy, by expansion of the field, provides a possible driving force for the coronal and interplanetary shock waves.

  14. The History and Evolution of Young and Distant Radio Sources

    NASA Astrophysics Data System (ADS)

    Collier, Jordan

    dense gas and dust in their environment; 2) prematurely dying radio sources; 3) recurrent radio galaxies. Their convex spectrum is generally thought to be caused by Synchrotron Self Absorption (SSA), an internal process in which the same population of electrons is responsible for the synchrotron emission and self-absorption. However, recent studies have shown that the convex spectrum may be caused by Free-Free Absorption (FFA), an external process in which an inhomogeneous screen absorbs the synchrotron emission. The majority of GPS and CSS samples consist of Jy-level and therefore, high-luminosity sources. VLBI images show that GPS and CSS sources typically have double-lobed, edge-brightened morphologies on mas scales, appearing as scaled down versions of Fanaroff-Riley Class II (FR II) galaxies. Recently, two low-luminosity GPS sources were found to have jet-brightened morphologies, which appeared as scaled down versions of Fanaroff-Riley Class I (FR I) galaxies. From this, it was proposed that there exists a morphology-luminosity break analogous to the FR I/II break and that low-luminosity GPS and CSS sources are the compact counterparts of FR I galaxies. However, this hypothesis remains unconfirmed, since very few samples of low-luminosity GPS and CSS sources exist. We conclude that, despite being historically favoured, single inhomogeneous SSA is not the dominant form of absorption amongst a large fraction of GPS and CSS sources. We find that FFA provides a good model for the majority of the spectra with observable turnovers, suggesting an inhomogeneous and clumpy ambient medium. Furthermore, we conclude that the majority of our GPS and CSS sources are young and evolving and may undergo recurrent activity over small time scales. We conclude that a very small fraction of GPS and CSS sources consists of frustrated, dying or restarted radio galaxies. (Abstract shortened by ProQuest.).

  15. PNNL Expert Doug McMakin Discusses Millimeter Wave Technology

    ScienceCinema

    McMakin, Doug

    2018-02-13

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

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

    NASA Astrophysics Data System (ADS)

    Yu, Shixing; Li, Long; Shi, Guangming

    2016-08-01

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

  17. Evolution and Spectrum of the Radio Emission of Tycho's Supernova Remnant

    NASA Astrophysics Data System (ADS)

    Vinyaikin, E. N.

    2018-02-01

    The radio spectrum of Tycho's Supernova Remnant is constructed at frequencies 12.6-143 000 MHz for epoch 2010.3, taking into account the secular decrease in the radio flux density of the remnant at the rate d = -(0.46 ± 0.03)%/year: S_ν ^{3C10} (t = 2010.3) = (43.1 ± 1.8 Jy)(ν [GHz])^{ - (0.592 ± 0.019) + (0.041 ± 0.012)log (ν [GHz])} . The spectrum has positive curvature. The presence of a low-frequency turnover in the spectrum of the radio source 3C10 with its maximum at 7.7 MHz is predicted, due to absorption in the interstellar medium in the direction toward the source.

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

    NASA Astrophysics Data System (ADS)

    Zhang, Zheng

    2017-10-01

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

  19. Full-duplex radio over fiber link with colorless source-free base station based on single sideband optical mm-wave signal with polarization rotated optical carrier

    NASA Astrophysics Data System (ADS)

    Ma, Jianxin

    2016-07-01

    A full-duplex radio-over fiber (RoF) link scheme based on single sideband (SSB) optical millimeter (mm)-wave signal with polarization-rotated optical carrier is proposed to realize the source-free colorless base station (BS), in which a polarization beam splitter (PBS) is used to abstract part of the optical carrier for conveying the uplink data. Since the optical carrier for the uplink does not bear the downlink signal, no cross-talk from the downlink contaminates the uplink signal. The simulation results demonstrate that both down- and up-links maintain good performance. The mm-wave signal distribution network based on the proposed full duplex fiber link scheme can use the uniform source-free colorless BSs, which makes the access system very simpler.

  20. Experimental observation of left polarized wave absorption near electron cyclotron resonance frequency in helicon antenna produced plasma

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

    Barada, Kshitish K.; Chattopadhyay, P. K.; Ghosh, J.

    2013-01-15

    Asymmetry in density peaks on either side of an m = +1 half helical antenna is observed both in terms of peak position and its magnitude with respect to magnetic field variation in a linear helicon plasma device [Barada et al., Rev. Sci. Instrum. 83, 063501 (2012)]. The plasma is produced by powering the m = +1 half helical antenna with a 2.5 kW, 13.56 MHz radio frequency source. During low magnetic field (B < 100 G) operation, plasma density peaks are observed at critical magnetic fields on either side of the antenna. However, the density peaks occurred at differentmore » critical magnetic fields on both sides of antenna. Depending upon the direction of the magnetic field, in the m = +1 propagation side, the main density peak has been observed around 30 G of magnetic field. On this side, the density peak around 5 G corresponding to electron cyclotron resonance (ECR) is not very pronounced, whereas in the m = -1 propagation side, very pronounced ECR peak has been observed around 5 G. Another prominent density peak around 12 G has also been observed in m = -1 side. However, no peak has been observed around 30 G on this m = -1 side. This asymmetry in the results on both sides is explained on the basis of polarization reversal of left hand polarized waves to right hand polarized waves and vice versa in a bounded plasma system. The density peaking phenomena are likely to be caused by obliquely propagating helicon waves at the resonance cone boundary.« less