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Sample records for radio emission dendrites

  1. Triggered Jovian radio emissions

    NASA Technical Reports Server (NTRS)

    Calvert, W.

    1985-01-01

    Certain Jovian radio emissions seem to be triggered from outside, by much weaker radio waves from the sun. Recently found in the Voyager observations near Jupiter, such triggering occurs at hectometric wavelengths during the arrival of solar radio bursts, with the triggered emissions lasting sometimes more than an hour as they slowly drifted toward higher frequencies. Like the previous discovery of similar triggered emissions at the earth, this suggests that Jupiter's emissions might also originate from natural radio lasers.

  2. Stellar radio emission (Review)

    NASA Astrophysics Data System (ADS)

    Zhelezniakov, V. V.

    The current understanding of the radio-emission characteristics of 'ordinary' main sequence stars as well as giants and supergiants is examined. Particular consideration is given to radio emission from supergiants, Young T Tauri stars, magnetic Ap stars, flare stars of UV Ceti type, Alpha Sco, and RS CVn objects. It is noted that the study of stellar radio emission is in its initial stage. Further progress in this area depends on successes in finding new radio sources, associated, for example, with magnetic stars, and on an intensified investigation of the frequency spectra and polarization of already-discovered radio stars. It is also noted that, although the current knowledge of solar physics can help in understanding stellar radio emission, models and ideas developed for solar conditions should not be mechanically transferred to other stars by a simple change in scale.

  3. Decimetric radio dot emissions

    NASA Astrophysics Data System (ADS)

    Mészárosová, H.; Karlický, M.; Sawant, H. S.; Fernandes, F. C. R.; Cecatto, J. R.; de Andrade, M. C.

    2008-11-01

    Context: We study a rare type of solar radio bursts called decimetric dot emissions. Aims: In the period 1999-2001, 20 events of decimetric dot emissions observed by the Brazilian Solar Spectroscope (BSS) in the frequency range 950-2640 MHz are investigated statistically and compared with radio fine structures of zebras and fibers. Methods: For the study of the spectral characteristics of the dot emissions we use specially developed Interactive Data Language (IDL) software called BSSView and basic statistical methods. Results: We have found that the dm dot emissions, contrary to the fine structures of the type IV bursts (i.e. zebras, fibers, lace bursts, spikes), are not superimposed on any background burst emission. In the radio spectrum, in most cases the dot emissions form chains that appear to be arranged in zebra patterns or fibers. Because some zebras and fibers, especially those observed with high time and high spectral resolutions, also show emission dots (but superimposed on the background burst emission), we compared the spectral parameters of the dot emissions with the dots being the fine structure of zebras and fibers. For both these dots, similar spectral characteristics were found. Some similarities of the dot emissions can be found also with the lace bursts and spikes. For some events the dot emissions show structural evolution from patterns resembling fibers to patterns resembling zebras and vice versa, or they evolve into fully chaotic patterns. Conclusions: For the first time, we present decimetric dot emissions that appear to be arranged in zebra patterns or fibers. We propose that these emissions are generated by the plasma emission mechanism at the locations in the solar atmosphere where the double resonance condition is fulfilled.

  4. Stellar radio emission

    NASA Technical Reports Server (NTRS)

    Bookbinder, Jay A.

    1988-01-01

    This paper presents an overview of the various radiation mechanisms believed to play a role in stellar radio emission. The radio emission from most stars is nonthermal and is generally due to mildly relativistic electrons with energies from a few keV to over 10 MeV. Magnetic fields play a crucial role both in accelerating the electrons to the requisite energies and in mediating the emission mechanism. They also play a fundamental role in creating the velocity anisotropies that are necessary for the operation of some of the coherent emission mechanisms. Coherent emission is seen most commonly on the M dwarfs, rarely on the RS CVns, and has yet to be detected for any other class of star. These coherent processes are best studied by means of their dynamic spectra; such studies are now just getting underway.

  5. Radio emission from supernovae.

    NASA Astrophysics Data System (ADS)

    Weiler, K. W.; Panagia, N.; Sramek, R. A.; Van Dyk, S. D.; Stockdale, C. J.; Williams, C. L.

    Study of radio supernovae over the past 30 years includes more than three dozen detected objects and more than 150 upper limits. From this work it is possible to identify classes of radio properties, demonstrate conformance to and deviations from existing models, estimate the density and structure of the circumstellar material and, by inference, the evolution of the presupernova stellar wind, and reveal the last stages of stellar evolution before explosion. Along with reviewing these general properties of the radio emission from supernovae, we present our extensive observations of the radio emission from supernova (SN) 1993J in M 81 (NGC 3031) made with the Very Large Array and other radio telescopes. The SN 1993J radio emission evolves regularly in both time and frequency, and the usual interpretation in terms of shock interaction with a circumstellar medium (CSM) formed by a pre-supernova stellar wind describes the observations rather well considering the complexity of the phenomenon. However: 1) The highest frequency measurements at 85 - 110 GHz at early times (<40 days) are not well fitted by the parameterization which describes the cm wavelength measurements. 2) At a time ˜3100 days after shock breakout, the decline rate of the radio emission steepens from (t+beta ) beta ˜ -0.7 to beta ˜ -2.7 without change in the spectral index (nu +alpha ; alpha ˜ -0.81). This decline is best described not as a power-law, but as an exponential decay with an e-folding time of ˜ 1100 days. 3) The best overall fit to all of the data is a model including both non-thermal synchrotron self-absorption (SSA) and a thermal free-free absorbing (FFA) components at early times, evolving to a constant spectral index, optically thin decline rate, until a break in that decline rate at day ˜3100, as mentioned above.

  6. Radio Emission from Supernovae

    NASA Astrophysics Data System (ADS)

    Weiler, Kurt W.; Panagia, Nino; Sramek, Richard A.; van Dyk, Schuyler D.; Williams, Christopher L.; Stockdale, Christopher J.; Kelley, Matthew T.

    2007-10-01

    Study of radio supernovae over the past 27 years includes more than three dozen detected objects and more than 150 upper limits. From this work it is possible to identify classes of radio properties, demonstrate conformance to and deviations from existing models, estimate the density and structure of the circumstellar material and, by inference, the evolution of the presupernova stellar wind, and reveal the last stages of stellar evolution before explosion. It is also possible to detect ionized hydrogen along the line of sight, to demonstrate binary properties of the presupernova stellar system, and to detect clumpiness of the circumstellar material. Along with reviewing these general properties of the radio emission from supernovae, we present our extensive observations of the radio emission from supernova (SN) 1993J in M 81 (NGC 3031) made with the Very Large Array and other radio telescopes. The SN 1993J radio emission evolves regularly in both time and frequency, and the usual interpretation in terms of shock interaction with a circumstellar medium (CSM) formed by a pre-supernova stellar wind describes the observations rather well considering the complexity of the phenomenon. However: 1) The highest frequency measurements at 85-110 GHz at early times (<40 days) are not well fitted by the parameterization which describes the cm wavelength measurements rather well. 2) At mid-cm wavelengths there is often deviation from the fitted radio light curves, particularly near the peak flux density, and considerable shorter term deviations in the declining portion when the emission has become optically thin. 3) At a time ~3100 days after shock breakout, the decline rate of the radio emission steepens from (t+β)β~-0.7 to β~-2.7 without change in the spectral index (ν+αα~-0.81). However, this decline is best described not as a power-law, but as an exponential decay starting at day ~3100 with an e-folding time of ~1100 days. 4) The best overall fit to all of the data is

  7. Solar radio emission

    NASA Technical Reports Server (NTRS)

    Goldman, M. V.; Smith, D. F.

    1981-01-01

    Active areas of both observational and theoretical research in which rapid progress is being made are discussed. These include: (1) the dynamic spectrum or frequency versus time plot; (2) physical mechanisms in the development of various types of bursts; (3) microwave type 1, 2, 3, and moving type 4 bursts; (4) bursts caused by trapped electrons; (5) physics of type 3bursts; (6) the physics of type 2 bursts and their related shocks; (7) the physics of both stationary and moving traps and associated type 1 and moving type 4 bursts; and (8) the status of the field of solar radio emission.

  8. CONSTRAINING RADIO EMISSION FROM MAGNETARS

    SciTech Connect

    Lazarus, P.; Kaspi, V. M.; Dib, R.; Champion, D. J.; Hessels, J. W. T.

    2012-01-10

    We report on radio observations of five magnetars and two magnetar candidates carried out at 1950 MHz with the Green Bank Telescope in 2006-2007. The data from these observations were searched for periodic emission and bright single pulses. Also, monitoring observations of magnetar 4U 0142+61 following its 2006 X-ray bursts were obtained. No radio emission was detected for any of our targets. The non-detections allow us to place luminosity upper limits of L{sub 1950} {approx}< 1.60 mJy kpc{sup 2} for periodic emission and L{sub 1950,single} {approx}< 7.6 Jy kpc{sup 2} for single pulse emission. These are the most stringent limits yet for the magnetars observed. The resulting luminosity upper limits together with previous results are discussed, as is the importance of further radio observations of radio-loud and radio-quiet magnetars.

  9. Phenomenology of magnetospheric radio emissions

    NASA Technical Reports Server (NTRS)

    Carr, T. D.; Desch, M. D.; Alexander, J. K.

    1983-01-01

    Jupiter has now been observed over 24 octaves of the radio spectrum, from about 0.01 MHz to 300,000 MHz. Its radio emissions fill the entire spectral region where interplanetary electromagnetic propagation is possible at wavelengths longer than infrared. Three distinct types of radiation are responsible for this radio spectrum. Thermal emission from the atmosphere accounts for virtually all the radiation at the high frequency end. Synchrotron emission from the trapped high-energy particle belt deep within the inner magnetosphere is the dominant spectral component from about 4000 to 40 MHz. The third class of radiation consists of several distinct components of sporadic low frequency emission below 40 MHz. The decimeter wavelength emission is considered, taking into account the discovery of synchrotron emission, radiation by high-energy electrons in a magnetic field, and the present status of Jovian synchrotron phenomenology. Attention is also given to the decameter and hectometer wavelength emission, and emissions at kilometric wavelengths.

  10. Radio Emission from Supernovae

    SciTech Connect

    Weiler, Kurt W.; Panagia, Nino; Sramek, Richard A.; Van Dyk, Schuyler D.; Stockdale, Christopher J.; Kelley, Matthew T.

    2009-05-03

    Study of radio supernovae over the past 27 years includes more than three dozen detected objects and more than 150 upper limits. From this work it is possible to identify classes of radio properties, demonstrate conformance to and deviations from existing models, estimate the density and structure of the circumstellar material and, by inference, the evolution of the presupernova stellar wind, and reveal the last stages of stellar evolution before explosion. It is also possible to detect ionized hydrogen along the line of sight, to demonstrate binary properties of the presupernova stellar system, and to detect dumpiness of the circumstellar material.

  11. Venus - Global surface radio emissivity

    NASA Technical Reports Server (NTRS)

    Ford, P. G.; Pettengill, G. H.

    1983-01-01

    Observations of thermal radio emission from the surface of Venus, made by the Pioneer Venus radar mapper at a wavelength of 17 cm, show variations that are dominated by changes in surface emissivity. The regions of lowest emissivity (0.54 + or - 0.05 for the highland areas of Aphrodite Terra and Theia Mons) correspond closely to regions of high radar reflectivity reported earlier. These results support the inference of inclusions of material with high electrical conductivity in the surface rock of these areas.

  12. Radio emission from supernova remnants

    NASA Astrophysics Data System (ADS)

    Dubner, Gloria; Giacani, Elsa

    2015-09-01

    The explosion of a supernova releases almost instantaneously about 10^{51} ergs of mechanic energy, changing irreversibly the physical and chemical properties of large regions in the galaxies. The stellar ejecta, the nebula resulting from the powerful shock waves, and sometimes a compact stellar remnant, constitute a supernova remnant (SNR). They can radiate their energy across the whole electromagnetic spectrum, but the great majority are radio sources. Almost 70 years after the first detection of radio emission coming from an SNR, great progress has been achieved in the comprehension of their physical characteristics and evolution. We review the present knowledge of different aspects of radio remnants, focusing on sources of the Milky Way and the Magellanic Clouds, where the SNRs can be spatially resolved. We present a brief overview of theoretical background, analyze morphology and polarization properties, and review and critically discuss different methods applied to determine the radio spectrum and distances. The consequences of the interaction between the SNR shocks and the surrounding medium are examined, including the question of whether SNRs can trigger the formation of new stars. Cases of multispectral comparison are presented. A section is devoted to reviewing recent results of radio SNRs in the Magellanic Clouds, with particular emphasis on the radio properties of SN 1987A, an ideal laboratory to investigate dynamical evolution of an SNR in near real time. The review concludes with a summary of issues on radio SNRs that deserve further study, and analysis of the prospects for future research with the latest-generation radio telescopes.

  13. Radio emission from AM Herculis

    NASA Technical Reports Server (NTRS)

    Bastian, T. S.; Dulk, G. A.; Chanmugam, G.

    1985-01-01

    Observations of the quiescent microwave emission of the magnetic cataclysmic variable AM Herculis are presented. The emission, which declined from a mean value of 0.58 mJy at 4.9 GHz to about 0.3 mJy, in rough coincidence with the entry of AM Herculis into an optical low state (mid-1983), is explained in terms of optically thick gyrosynchrotron emission. It is noted that the observation of a coherent outburst at 4.9 GHz, interpreted as the result of a cyclotron maser on the red dwarf secondary, indicates that the secondary is magnetized. Possible implications are briefly explored. Comparisons between this system and other stellar continuum radio sources are made.

  14. X-ray and radio core emission in radio quasars

    NASA Technical Reports Server (NTRS)

    Kembhavi, A.; Feigelson, E. D.; Singh, K. P.

    1986-01-01

    In order to investigate the physical relationship between X-ray and radio core emission in radio-selected quasars, 35 radio quasars have been observed with the VLA at 6 and 20 cm. The sample was chosen from a list of radio quasars with known X-ray luminosity but poorly known radio properties. Including data gathered from the literature, radio core detections or upper limits at 6 cm have been obtained for 127 radio quasars which have published Einstein X-ray data. A statistical association is sought between radio core luminosity and X-ray luminosity, and it is found that there is a strong correlation. The slope of the relation of L(x) to L(Gamma)-alpha is alpha = 0.71 + or - 0.07 for unresolved quasars with flat radio spectra. The slope decreases as quasars with extended radio regions are considered. This is traced to the presence of radio emission which is unrelated to the X-ray emission, in the presently unresolved cores of quasars.

  15. Synthesis and field emission properties of Cu dendritic nanostructures

    NASA Astrophysics Data System (ADS)

    Xu, Jianwen; Yu, Ke; Zhu, Ziqiang

    2010-03-01

    Cu dendritic nanostructures were synthesized on ITO glass substructure by electrochemical deposition. SEM images showed that these Cu dendritic nanostuctures revealed a clear and well-defined dendritic fractal structure with a pronounced trunk and highly ordered branches distributed on both sides of the trunk. The diffusion-limited aggregation (DLA) model was used to explain the fractal growth of Cu dendritic nanostructures. Field emission properties of these Cu dendritic nanostructures were measured, which have possessed good performance with the turn-on field of 7.5 V/μm (defined as the electric field required to be detected at a current density of 0.1 mA/cm 2) and the field enhancement factor β of 1094.

  16. Radio emission in peculiar galaxies

    NASA Technical Reports Server (NTRS)

    Demellorabaca, Dulia F.; Abraham, Zulema

    1990-01-01

    During the last decades a number of surveys of peculiar galaxies have been carried out and accurate positions become available. Since peculiarities are a possible evidence of radio emission (Wright, 1974; Sulentic, 1976; Stocke et al., 1978), the authors selected a sample of 24 peculiar galaxies with optical jet-like features or extensions in different optical catalogues, mainly the Catalogue of Southern Peculiar Galaxies and Associations (Arp and Madore, 1987) and the ESO/Uppsala Survey of the ESO(B) Atlas (Lauberts, 1982) for observation at the radio continuum frequency of 22 GHz. The sample is listed in a table. Sol (1987) studied this sample and concluded that the majority of the jet-like features seem to admit an explanation in terms of interactive galaxies with bridges and/or tails due to tidal effects. Only in a few cases do the jets seem to be possibly linked to some nuclear activity of the host galaxy. The observations were made with the 13.7m-radome enclosed Itapetinga Radiotelescope (HPBW of 4.3 arcmin), in Brazil. The receiver was a 1 GHz d.s.b. super-heterodine mixer operated in total-power mode, with a system temperature of approximately 800 K. The observational technique consisted in scans in right ascention, centralized in the optical position of the galaxy. The amplitude of one scan was 43 arcmin, and its duration time was 20 seconds. The integration time was at least 2 hours (12 ten-minute observations) and the sensibility limit adopted was an antenna temperature greater than 3 times the r.m.s. error of the baseline determination. Virgo A was used as the calibrator source. Three galaxies were detected for the first time as radio sources and four other known galaxies at low frequencies had their flux densities measured at 22 GHz. The results for these sources are presented.

  17. On the origin of radio emission in radio quiet quasars

    NASA Astrophysics Data System (ADS)

    Laor, Ari; Behar, Ehud

    The radio emission in radio loud quasars (RLQs) originates in a jet carrying relativistic electrons. In radio quiet quasars (RQQs) the radio emission is ˜ 103 times weaker, relative to other bands. Its origin is not clearly established yet, but it is often speculated to arise from a weak jet. Here we show that there is a tight relation between L_R and L_X for RQQs, with L_R/L_X˜ 10-5, based on the optically selected Palomar-Green (PG) quasars, with nearly complete X-ray and radio detections (avoiding biases and selection effects). Coronally active stars also show a tight relation between L_R and L_X with L_R/L_X˜ 10-5 (the Güdel & Benz relation), which together with correlated variability indicates that stellar coronae are magnetically heated. The X-ray emission of quasars most likely originates from a hot accretion disk corona, and since RQQs follow the Güdel & Benz relation, it is natural to associate their radio emission with coronal emission as well. The tight relation between L_R and L_X may simply reflect the equality of accretion disk coronal heating by magnetically generated relativistic electrons (producing L_R), and coronal cooling by Compton scattering (producing L_X). This suggestion can be tested by looking for correlated X-ray and radio variability patterns, such as the Neupert effect, displayed by stellar coronae.

  18. Radio emissions from RHESSI TGFs

    NASA Astrophysics Data System (ADS)

    Mezentsev, Andrey; Østgaard, Nikolai; Gjesteland, Thomas; Albrechtsen, Kjetil; Cummer, Steven

    2016-04-01

    The discovery of bursts of energetic photons coming out to space from the Earth's atmosphere, referred to as terrsetrial gamma-ray flashes (TGFs), has stimulated research activity investigating different aspects of the TGF generation and accompanying processes. Two models of the TGF production are nowadays competing to explain the observations of the TGFs and related phenomena. One of the models involves the feedback mechanism enhancing the production rate of the runaway electrons in the ambient electric field of a thundercloud. Another model considers runaway electrons accelerated in the strong local electric field in front of the upward propagating negative leader of the +IC. We performed a detailed analysis of RHESSI TGFs detected between August 2004 and September 2015. It was reported that the RHESSI satellite clock has a systematic error of ˜ 1.8 ms, but the exact value remained unknown, also it was unclear if this systematic clock error is changing with time or not. We compared RHESSI TGFs with the world wide lightning location network (WWLLN) database and found the distribution of the time delays between the TGF peak times and associated WWLLN detections. This distribution allowed us to find the value of the RHESSI systematic clock offset with the microsecond accuracy level. Also we found that this offset experienced two changes: in August 2005 and in October 2013, which was confirmed by two independent ways. We found that in case of double TGFs WWLLN detection corresponds to the second TGF of the pair. VLF magnetic field recordings from the Duke University also attribute radio sferics to the second TGF, exhibiting no detectable radio emission during the first TGFs of the TGF pairs. We have proposed a possible scenario that is consistent with the observations. This scenario supports the leader-based model of the TGF generation. Spectral characteristics of 77 sferics recorded by the Duke University VLF sensors and related to the RHEESI TGFs show that maximal

  19. Modeling of radio emissions from Neptune

    NASA Astrophysics Data System (ADS)

    Menietti, J. D.; Curran, D. B.

    We have developed a plasma model of the Neptunian magnetosphere that includes a density cavity centered on the L=6 magnetic field line. Assuming the O8 magnetic field model, we have performed ray tracing of smooth radio emission from Neptune, and the results generally support the findings of Ladreiter et al. (1991), but differ in details of the source locations. In addition, we have examined source locations of bursty radio emission that are consistent with propagation at small wave normal angles as hypothesized for the temperature anisotropic beam instability (TABI) (Winglee et al., 1992). The source locations are adjacent (complementary) to the sources of the smooth radio emission. Using previously developed plasma and magnetic field models for Uranus, we have performed a similar study of bursty radio emissions. Again the source locations appear to be adjacent to the source regions of smooth radio emission, consistent with the TABI.

  20. Models of Uranium continuum radio emission

    NASA Technical Reports Server (NTRS)

    Romig, Joseph H.; Evans, David R.; Sawyer, Constance B.; Schweitzer, Andrea E.; Warwick, James W.

    1987-01-01

    Uranium continuum radio emission detected by the Voyager 2 Planetary Radio Astronomy experiment during the January 1986 encounter is considered. The continuum emissions comprised four components (equatorial emissions, anomaly emissions, strong nightside emissions, and weak nightside emissions) associated with different sources. The equatorial emissions appeared most prominently during the days before closest approach and extended from 40 kHz or below to about 120 kHz. The anomaly emissions were seen about 12 hours before closest approach and extended to about 250 kHz. The agreement found between Miranda's phase and strong radio emission at 20.4 kHz, just after closest approach, suggests intense dynamic activity on the Miranda L shell.

  1. Non-thermal radio emission from Saturn

    NASA Technical Reports Server (NTRS)

    Warwick, J. W.

    1978-01-01

    Direct, strong evidence for non-thermal radio emission from Saturn exists in the hectometric data observed by Imp 6. The planet has been tentatively identified as a decametric source, but the most sensitive and most recent data fail to confirm this. At metric or decimetric wavelengths Saturn has no non-thermal emission like Jupiter's synchrotron sources. Finally, a comparative study of Earth and Jupiter radio emissions suggests lightning discharges.

  2. Coherent emission in fast radio bursts

    NASA Astrophysics Data System (ADS)

    Katz, J. I.

    2014-05-01

    The fast (ms) radio bursts reported by Lorimer et al. Science 318, 777 (2007) and Thornton et al. Science 341, 53 (2013) have extremely high brightness temperatures if at the inferred cosmological distances. This implies coherent emission by "bunches" of charges. Fast radio bursts, like the giant pulses of the Crab pulsar, display banded spectra that may be harmonics of plasma frequency emission by plasma turbulence and are inconsistent with emission by charge distributions moving relativistically. We model the emission region as a screen of half-wave dipole radiators resonant around the frequencies of observation, the maximally bright emission mechanism of nonrelativistic charges, and calculate the implied charge bunching. From this we infer the minimum electron energy required to overcome electrostatic repulsion. If fast radio bursts are the counterparts of Galactic events, their Galactic counterparts may be detected from any direction above the horizon by radio telescopes in their far sidelobes or by small arrays of dipoles.

  3. Quasar emission lines, radio structures and radio unification

    NASA Astrophysics Data System (ADS)

    Jackson, Neal; Browne, I. W. A.

    2013-02-01

    Unified schemes of radio sources, which account for different types of radio active galactic nucleus in terms of anisotropic radio and optical emission, together with different orientations of the ejection axis to the line of sight, have been invoked for many years. Recently, large samples of optical quasars, mainly from the Sloan Digital Sky Survey (SDSS), together with large radio samples, such as Faint Images of the Radio Sky at Twenty cm (FIRST), have become available. These hold the promise of providing more stringent tests of unified schemes but, compared to previous samples, lack high-resolution radio maps. Nevertheless, they have been used to investigate unified schemes, in some cases yielding results which appear inconsistent with such theories. Here we investigate using simulations how the selection effects to which such investigations are subject can influence the conclusions drawn. In particular, we find that the effects of limited resolution do not allow core-dominated radio sources to be fully represented in the samples, that the effects of limited sensitivity systematically exclude some classes of sources and the lack of deep radio data make it difficult to decide to what extent closely separated radio sources are associated. Nevertheless, we conclude that relativistic unified schemes are entirely compatible with the current observational data. For a sample selected from SDSS and FIRST which includes weak-cored triples we find that the equivalent width of the [O III] emission line decreases as core dominance increases, as expected, and also that core-dominated quasars are optically brighter than weak-cored quasars.

  4. Solar emission levels at low radio frequencies

    NASA Technical Reports Server (NTRS)

    Erickson, W. C.

    1990-01-01

    Solar radio emission could seriously interfere with observations made by a low frequency (1 to 10 MHz) array in space. International Sun-Earth Explorer (ISEE-3) radio data were used to determine solar emission level. The results indicate that solar emission should seriously disturb less than ten percent of the data, even during the years of solar maximum. Thus it appears that solar emission should not cause a disastrous loss of data. The information needed to design procedures to excise solar interference from the data produced by any low-frequency array is provided.

  5. Transient pulsed radio emission from a magnetar.

    PubMed

    Camilo, Fernando; Ransom, Scott M; Halpern, Jules P; Reynolds, John; Helfand, David J; Zimmerman, Neil; Sarkissian, John

    2006-08-24

    Anomalous X-ray pulsars (AXPs) are slowly rotating neutron stars with very bright and highly variable X-ray emission that are believed to be powered by ultra-strong magnetic fields of >10(14) G, according to the 'magnetar' model. The radio pulsations that have been observed from more than 1,700 neutron stars with weaker magnetic fields have never been detected from any of the dozen known magnetars. The X-ray pulsar XTE J1810-197 was revealed (in 2003) as the first AXP with transient emission when its luminosity increased 100-fold from the quiescent level; a coincident radio source of unknown origin was detected one year later. Here we show that XTE J1810-197 emits bright, narrow, highly linearly polarized radio pulses, observed at every rotation, thereby establishing that magnetars can be radio pulsars. There is no evidence of radio emission before the 2003 X-ray outburst (unlike ordinary pulsars, which emit radio pulses all the time), and the flux varies from day to day. The flux at all radio frequencies is approximately equal--and at >20 GHz XTE J1810-197 is currently the brightest neutron star known. These observations link magnetars to ordinary radio pulsars, rule out alternative accretion models for AXPs, and provide a new window into the coronae of magnetars. PMID:16929292

  6. Radio emissions and the heliospheric termination shock

    NASA Technical Reports Server (NTRS)

    Zank, G. P.; Cairns, I. H.; Donohue, D. J.; Matthaeus, W. H.

    1994-01-01

    With the Voyager spacecrafts' discovery of low-frequency radio emissions from the depths of the outer heliosphere has come the realization that the boundaries between our heliosphere and the local interstellar medium have been detected. A model is presented here that can account for the observed radio emissions, based upon a termination shock modified by the dynamical effect of galactic and anomalous cosmic rays. Frequency and time domain properties of both continuum and transient radio events are explained, and new estimates for the distance to the termination shock (approximately 60-70 astronomical units) and the heliopause (less than or approximately 90 AU) are given.

  7. Nonthermal Radio Emission and the HR Diagram

    NASA Technical Reports Server (NTRS)

    Gibson, D. M.

    1985-01-01

    Perhaps the most reliable indicator of non-radiative heating/momentum in a stellar atmosphere is the presence of nonthermal radio emission. To date, 77 normal stellar objects have been detected and identified as nonthermal sources. These stellar objects are tabulated herein. It is apparent that non-thermal radio emission is not ubiquitous across the HR diagram. This is clearly the case for the single stars; it is not as clear for the binaries unless the radio emission is associated with their late-type components. Choosing to make this association, the single stars and the late-type components are plotted together. The following picture emerges: (1) there are four locations on the HR diagram where non-thermal radio stars are found; (2) the peak incoherent 5 GHz luminosities show a suprisingly small range for stars within each class; (3) the fraction of stellar energy that escapes as radio emission can be estimated by comparing the integrated maximum radio luminosity to the bolometric luminosity; (4) there are no apparent differences in L sub R between binaries with two cool components, binaries with one hot and one cool component, and single stars for classes C and D; and (5) The late-type stars (classes B, C, and D) are located in parts of the HR diagram where there is reason to suspect that the surfaces of the stars are being braked with respect to their interiors.

  8. Io control of Jovian radio emission

    NASA Technical Reports Server (NTRS)

    Desch, M. D.

    1980-01-01

    The possibility of Io controlling Jovian decametric radio emission, particularly in the region below 22 MHz, is discussed. Results of a two-year survey at 26.3 at 26.3 MHz are presented which demonstrate the control of Io over a high-intensity storm component of the radio emission and the independence of a weak radio component from the phase of Io, as was observed at lower frequencies. It is thus hypothesized that Io control is a flux-dependent rather than a frequency-dependent phenomenon, and results of analyses at 18 and 10 MHz which support this hypothesis are presented. The apparent correlation between frequency and Io control is thus shown to result from a selection effect due to the increase of non-Io emission with decreasing frequency and relative antenna detection threshold. This result implies a contiguous Io-controlled source region extending out several Jovian radii along the Io flux tube.

  9. Control of Jovian Radio Emission by Callisto

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.; Gurnett, D. A.; Christopher, I.

    2001-01-01

    Galileo has been in orbit around Jupiter since December 1995 and a large database has been collected. We present the results of a survey of the plasma wave data for the frequency range 2.0 MHz to 5.6 MHz, the low frequency decametric (DAM) emissions. While the control of a portion of the radio emission by the moon lo is well known, and Ganymede control has been more recently indicated, we report that a small but significant portion of DAM emission is seen to be correlated with the orbital phase of Callisto. While the occurrence rate of emission controlled by Ganymede and Callisto is considerably less than for lo, the power levels can be nearly the same. We estimate the power of the Callisto-dependent emission to be approx. 70% of the Io-dependent radio emission and about the same as the Ganymede-dependent radio emission. This result indicates an Alfven current system associated with Callisto, and thus a significant interaction of the magnetosphere of Callisto with that of Jupiter as is believed to exist for both lo and Ganymede.

  10. Radio emission from chemically peculiar stars

    NASA Technical Reports Server (NTRS)

    Linsky, Jeffrey L.; Drake, Stephen A.; Bastian, T. S.

    1992-01-01

    In five VLA observing runs the initial survey of radio emission from magnetic Bp-Ap stars by Drake et al. is extended to include a total of 16 sources detected at 6 cm out of 61 observed, giving a detection rate of 26 percent. Of these stars, three are also detected at 2 cm, four at 3.6 cm, and five at 20 cm. The 11 new stars detected as radio sources have spectral types B5-A0 and are He-weak and Si-strong. No classical (SrCrEu-type) Ap stars have yet been detected. The 16 detected sources show a wide range of radio luminosities with the early-B He-S stars on average 20 times more radio luminous than the late-B He-W stars and 1000 times more luminous than Theta Aurigae. Multifrequency observations indicate flat spectra in all cases. Four stars have a detectable degree of circular polarization at one or more frequencies. It is argued that the radio-emitting CP (chemically peculiar) stars form a distinct class of radio stars that differs from both the hot star wind sources and the active late-type stars. The observed properties of radio emission from these stars may be understood in terms of optically thick gyrosynchrotron emission from a nonthermal distribution of electrons produced in a current sheet far from the star. In this model the electrons travel along magnetic fields to smaller radii and higher magnetic latitudes where they mirror and radiate microwave radiation.

  11. Possible radio emission mechanism for pulsars

    NASA Technical Reports Server (NTRS)

    Kovalev, Y. A.

    1979-01-01

    A mathematical model is presented and discussed as a possible mechanism to describe radio emission from pulsars. The model determines that the magnetic field in the neutron proton electron (npe) layer of a neutron star results from a quasistationary eddy current of superconducting and normal protons relative to normal electrons, which generates radio emission by the Josephson effect. The radiation propagates in the magnetically active medium, from the optically thick npe layer to the magnetosphere through breaks in the crust. As a result, hot radio spots form on the surface of the star, and a radiation pattern forms near the magnetic poles, the cross section of which gives the observed pulse structure. Due to the specific properties of the mechanism, variations of the quasistationary current are converted to amplitude frequency variations of the radiation spectrum. Variations of the fine structure of the spectrum pulse amplitude and spectral index, as well as their correlation are discussed.

  12. Detection of radio continuum emission from Procyon

    NASA Technical Reports Server (NTRS)

    Drake, Stephen A.; Simon, Theodore; Brown, Alexander

    1993-01-01

    We have detected the F5 IV-V star Procyon as a weak and variable 3.6 cm radio continuum source using the VLA. The inferred radio luminosity is similar to, though some-what higher than, the X-band luminosity of the active and flaring sun. The 33 micro-Jy flux density level at which we detected Procyon on four of five occasions is close to the 36 micro-Jy radio flux density expected from a model in which the radio emission consists of two components: optically thick 'stellar disk' emission with a 3.6 cm brightness temperature of 20,000 K that is 50 percent larger than the solar value, and optically thin coronal emission with an emission measure the same as that indicated by Einstein and EXOSAT X-ray flux measurements in 1981 and 1983. The maximum mass-loss rate of a warm stellar wind is less than 2 x 10 exp -11 solar mass/yr. An elevated flux density of 115 micro-Jy observed on a single occasion provides circumstantial evidence for the existence of highly localized magnetic fields on the surface of Procyon.

  13. Radio emission physics in the Crab pulsar

    NASA Astrophysics Data System (ADS)

    Eilek, Jean A.; Hankins, Timothy H.

    2016-06-01

    We review our high-time-resolution radio observations of the Crab pulsar and compare our data to a variety of models for the emission physics. The Main Pulse and the Low Frequency Interpulse come from regions somewhere in the high-altitude emission zones (caustics) that also produce pulsed X-ray and -ray emission. Although no emission model can fully explain these two components, the most likely models suggest they arise from a combination of beam-driven instabilities, coherent charge bunching and strong electromagnetic turbulence. Because the radio power fluctuates on a wide range of time scales, we know the emission zones are patchy and dynamic. It is tempting to invoke unsteady pair creation in high-altitude gaps as the source of the variability, but current pair cascade models cannot explain the densities required by any of the likely models. It is harder to account for the mysterious High Frequency Interpulse. We understand neither its origin within the magnetosphere nor the striking emission bands in its dynamic spectrum. The most promising models are based on analogies with solar zebra bands, but they require unusual plasma structures which are not part of our standard picture of the magnetosphere. We argue that radio observations can reveal much about the upper magnetosphere, but work is required before the models can address all of the data.

  14. Radio emission physics in the Crab pulsar

    NASA Astrophysics Data System (ADS)

    Eilek, Jean A.; Hankins, Timothy H.

    2016-06-01

    > We review our high-time-resolution radio observations of the Crab pulsar and compare our data to a variety of models for the emission physics. The Main Pulse and the Low Frequency Interpulse come from regions somewhere in the high-altitude emission zones (caustics) that also produce pulsed X-ray and -ray emission. Although no emission model can fully explain these two components, the most likely models suggest they arise from a combination of beam-driven instabilities, coherent charge bunching and strong electromagnetic turbulence. Because the radio power fluctuates on a wide range of time scales, we know the emission zones are patchy and dynamic. It is tempting to invoke unsteady pair creation in high-altitude gaps as the source of the variability, but current pair cascade models cannot explain the densities required by any of the likely models. It is harder to account for the mysterious High Frequency Interpulse. We understand neither its origin within the magnetosphere nor the striking emission bands in its dynamic spectrum. The most promising models are based on analogies with solar zebra bands, but they require unusual plasma structures which are not part of our standard picture of the magnetosphere. We argue that radio observations can reveal much about the upper magnetosphere, but work is required before the models can address all of the data.

  15. Elliptically polarized bursty radio emissions from Jupiter

    NASA Technical Reports Server (NTRS)

    Reiner, M. J.; Desch, M. D.; Kaiser, M. L.; Manning, R.; Fainberg, J.; Stone, R. G.

    1995-01-01

    We report a new component of Jovian radio emission observed by the Ulysses spacecraft when Ulysses was at high Jovigraphic latitudes (greater than or approximately = 30 deg north or south of the Jovian magnetic equator). This bursty high-latitude emission is elliptically polarized in the right-hand sense when observed from northern latitudes and in the left-hand sense when observed from southern latitudes, consistent with extraordinary mode. The orientation of the polarization ellipse is observed to systematically vary with time relative to the observer. It is argued that the elliptically-polarized nature of the emission is intrinsic to the source region.

  16. Control of Jovian Radio Emission by Ganymede

    NASA Technical Reports Server (NTRS)

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

    1998-01-01

    Galileo has been in orbit around Jupiter since December 1995. We present the results of a survey of the data for the frequency range 3.2 MHz to 5.6 MHz, the low-frequency decametric (DAM) emissions. While the control of a portion of the radio emission by the moon Io is well-known, we report that a small but significant portion of low-frequency DAM emission is seen to be correlated with the orbital phase of Ganymede. This result is in agreement with other recent results indicating a significant interaction of the magnetosphere of Ganymede with that of Jupiter.

  17. Calculation of the radio emission from EAS

    NASA Technical Reports Server (NTRS)

    Allan, H. R.; Sun, M. P.; Crannell, C. J.; Hough, J. H.; Shutie, P. F.

    1975-01-01

    Time-varying features of an electron-photon cascade are considered, particularly those associated with radio emission. The cosmic ray shower is represented as a superposition of collinear 10 GeV electron-photon cascades launched at different heights in the atmosphere. Actual simulations are performed for only 10 cascades at each of 40 heights and the results are scaled to represent the total number of cascades required. The apparent angular motions of the cascade particles as detected by antennas located at various positions up to 300 m from the shower axis are simulated. The radio pulse waveform and the corresponding frequency spectrum are obtained from these motions.

  18. Cross-Correlations in Quasar Radio Emission

    NASA Astrophysics Data System (ADS)

    Nefedyev, Yuri; Panischev, Oleg; Demin, Sergey

    The main factors forming the complex evolution of the accretive astrophysical systems are nonlinearity, intermittency, nonstationarity and also collective phenomena. To discover the dynamic processes in these objects and to detain understanding their properties we need to use all the applicable analyzing methods. Here we use the Flicker-Noise Spectroscopy (FNS) as a phenomenological approach to analyzing and parameterizing the auto- and cross-correlations in time series of astrophysical objects dynamics. As an example we consider the quasar flux radio spectral density at frequencies 2.7 GHz and 8.1 GHz. Data have been observed by Dr. N. Tanizuka (Laboratory for Complex Systems Analysis, Osaka Prefecture University) in a period of 1979 to 1988 (3 309 days). According to mental habits quasar is a very energetic and distant active galactic nucleus containing a supermassive black hole by size 10-10,000 times the Schwarzschild radius. The quasar is powered by an accretion disc around the black hole. The accretion disc material layers, moving around the black hole, are under the influence of gravitational and frictional forces. It results in raising the high temperature and arising the resonant and collective phenomena reflected in quasar emission dynamics. Radio emission dynamics of the quasar 0215p015 is characterized by three quasi-periodic processes, which are prevalent in considering dynamics. By contrast the 1641p399's emission dynamics have not any distinguish processes. It means the presence of high intermittency in accretive modes. The second difference moment allows comparing the degree of manifesting of resonant and chaotic components in initial time series of the quasar radio emission. The comparative analysis shows the dominating of chaotic part of 1641p399's dynamics whereas the radio emission of 0215p015 has the predominance of resonant component. Analyzing the collective features of the quasar radio emission intensity demonstrates the significant

  19. DIFFUSE RADIO EMISSION IN ABELL 754

    SciTech Connect

    Kale, Ruta; Dwarakanath, K. S. E-mail: dwaraka@rri.res.in

    2009-07-10

    We present a low-frequency study of the diffuse radio emission in the galaxy cluster A754. We present a new 150 MHz image of the galaxy cluster A754 made with the Giant Metrewave Radio Telescope and discuss the detection of four diffuse features. We compare the 150 MHz image with the images at 74, 330, and 1363 MHz; one new diffuse feature is detected. The flux density upper limits at 330 and 1363 MHz imply a synchrotron spectral index, {alpha}>2 (S {proportional_to} {nu}{sup -{alpha}}), for the new feature. The 'west relic' detected at 74 MHz is not detected at 150 MHz and is thus consistent with its nondetection at 1363 MHz and 330 MHz. Integrated spectra of all the diffuse features are presented. The fourth diffuse feature is located along the proposed merger axis in A754 and 0.7 Mpc away from the peak of X-ray emission; we refer to it as a relic. We have made use of the framework of the adiabatic compression model to obtain spectra. We show that the spectrum of the fourth diffuse feature is consistent with that of a cocoon of a radio galaxy lurking for about 9 x 10{sup 7} yr; no shock compression is required. The other three diffuse emission have spectra steeper than 1.5 and could be cocoons lurking for longer time. We discuss other possibilities such as shocks and turbulent reacceleration being responsible for the diffuse emission in A754.

  20. Radio Emissions from the Outer Heliosphere

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.; Kurth, W. S.

    1996-01-01

    For nearly fifteen years the Voyager 1 and 2 spacecraft have been detecting an unusual radio emission in the outer heliosphere in the frequency range from about 2 to 3 kHz. Two major events have been observed, the first in 1983-84 and the second in 1992-93. In both cases the onset of the radio emission occurred about 400 days after a period of intense solar activity, the first in mid-July 1982, and the second in May-June 1991. These two periods of solar activity produced the two deepest cosmic ray Forbush decreases ever observed. Forbush decreases are indicative of a system of strong shocks and associated disturbances propagating outward through the heliosphere. The radio emission is believed to have been produced when this system of shocks and disturbances interacted with one of the outer boundaries of the heliosphere, most likely in the vicinity of the the heliopause. The emission is believed to be generated by the shock-driven Langmuir-wave mode conversion mechanism, which produces radiation at the plasma frequency (f(sub p)) and at twice the plasma frequency (2f(sub p)). From the 400-day travel time and the known speed of the shocks, the distance to the interaction region can be computed, and is estimated to be in the range from about 110 to 160 AU.

  1. Models of Neptune's smooth recurrent radio emission

    NASA Technical Reports Server (NTRS)

    Sawyer, Constance

    1993-01-01

    The quantitative response of the Planetary Radio Astronomy (PRA) instrument to a wave with polarization ellipse of arbitrary shape and orientation, arriving at the antennas from any direction, can be determined. This capability is used to model the time variation of intensity and circular polarization over a range of radio frequencies for proposed radio-source locations and emission characteristics at Neptune. At frequencies below 400 kHz the observed variation of intensity, polarization, and phase are closely simulated in an offset tilted dipole magnetic field by conjugate sources at midlatitude with filled emission cones. The phase of emission at higher frequencies is reproduced by sources at lower latitude. Modeled wide-cone emission does not reach the spacecraft at the observed phase nor have the polarization sense observed before closest approach. Source-surface maps of apparent polarization for the period before closest approach when instrumental response is especially sensitive to source location is presented. The method is capable of extension to more realistic models of the magnetic field.

  2. AGN coronal emission models - I. The predicted radio emission

    NASA Astrophysics Data System (ADS)

    Raginski, I.; Laor, Ari

    2016-06-01

    Accretion discs in active galactic nucleus (AGN) may be associated with coronal gas, as suggested by their X-ray emission. Stellar coronal emission includes radio emission, and AGN corona may also be a significant source for radio emission in radio quiet (RQ) AGN. We calculate the coronal properties required to produce the observed radio emission in RQ AGN, either from synchrotron emission of power-law (PL) electrons, or from cyclosynchrotron emission of hot mildly relativistic thermal electrons. We find that a flat spectrum, as observed in about half of RQ AGN, can be produced by corona with a disc or a spherical configuration, which extends from the innermost regions out to a pc scale. A spectral break to an optically thin power-law emission is expected around 300-1000 GHz, as the innermost corona becomes optically thin. In the case of thermal electrons, a sharp spectral cut-off is expected above the break. The position of the break can be measured with very long baseline interferometry observations, which exclude the cold dust emission, and it can be used to probe the properties of the innermost corona. Assuming equipartition of the coronal thermal energy density, the PL electrons energy density, and the magnetic field, we find that the energy density in a disc corona should scale as ˜R-1.3, to get a flat spectrum. In the spherical case the energy density scales as ˜R-2, and is ˜4 × 10-4 of the AGN radiation energy density. In Paper II we derive additional constraints on the coronal parameters from the Gudel-Benz relation, Lradio/LX-ray ˜ 10- 5, which RQ AGN follow.

  3. Analysis and Modeling of Jovian Radio Emissions Observed by Galileo

    NASA Technical Reports Server (NTRS)

    Menietti, J. D.

    2003-01-01

    Our studies of Jovian radio emission have resulted in the publication of five papers in refereed journals, with three additional papers in progress. The topics of these papers include the study of narrow-band kilometric radio emission; the apparent control of radio emission by Callisto; quasi-periodic radio emission; hectometric attenuation lanes and their relationship to Io volcanic activity; and modeling of HOM attenuation lanes using ray tracing. A further study of the control of radio emission by Jovian satellites is currently in progress. Abstracts of each of these papers are contained in the Appendix. A list of the publication titles are also included.

  4. Coronal Mass Ejections and Solar Radio Emissions

    NASA Technical Reports Server (NTRS)

    Gopalswamy, Nat

    2010-01-01

    Coronal mass ejections (CMEs) have important connections to various types of radio emissions from the Sun. The persistent noise storm radiation (type I storm at metric wavelengths, type III storms at longer wavelengths) can be clearly interrupted by the occurrence of a CME in the active region that produces the storm. Sometimes the noise storm completely disappears and other times, it reappears in the active region. Long-lasting type III bursts are associated with CME eruption, thought to be due to the reconnection process taking place beneath the erupting CME. Type II bursts are indicative of electron acceleration in the CME-driven shocks and hence considered to be the direct response of the CME propagation in the corona and interplanetary medium. Finally type IV bursts indicate large-scale post-eruption arcades containing trapped electrons that produce radio emission. This paper summarizes some key results that connect CMEs to various types of radio emission and what we can learn about particle acceleration in the corona) and interplanetary medium. Particular emphasis will be placed on type If bursts because of their connection to interplanetary shocks detected in situ.

  5. Polarization model applied to Uranian radio emission

    NASA Astrophysics Data System (ADS)

    Sawyer, C. B.; Neal, K. L.; Warwick, J. W.

    1991-04-01

    The total power and the degree of circular polarization as measured by the Planetary Radio Astronomy experiments on the Voyager spacecraft are modeled. For a source near the electron cyclotron frequency, the degree of circular polarization is determined by the angle between the wave vector and the field. It is shown that the observed strong circular polarization of Uranian smooth low-frequency (SLF) can be modeled as emission that is beamed along the direction of the magnetic field in a filled cone. The main observational constraints of SLF emission from Uranus are met by conjugate sources at about 21 deg from the magnetic equator.

  6. ARCADE 2 Observations of Galactic Radio Emission

    NASA Technical Reports Server (NTRS)

    Kogut, A.; Fixsen, D. J.; Levin, S. M.; Limon, M.; Lubin, P. M.; Mirel, P.; Seiffert, M.; Singal, J.; Villela, T.; Wollack, E.; Wuensche, C. A.

    2010-01-01

    We use absolutely calibrated data from the Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE 2) flight in July 2006 to model Galactic emission at frequencies 3, 8, and 10 GHz. The spatial structure in the data is consistent with a superposition of free-free and synchrotron emission. Emission with spatial morphology traced by the Haslam 408 MHz survey has spectral index beta_synch = -2.5 +/- 0.1, with free-free emission contributing 0.10 +/- 0.01 of the total Galactic plane emission in the lowest ARCADE 2 band at 3.15 GHz. We estimate the total Galactic emission toward the polar caps using either a simple plane-parallel model with csc|b| dependence or a model of high-latitude radio emission traced by the COBE/FIRAS map of CII emission. Both methods are consistent with a single power-law over the frequency range 22 MHz to 10 GHz, with total Galactic emission towards the north polar cap T_Gal = 0.498 +/- 0.028 K and spectral index beta = -2.55 +/- 0.03 at reference frequency 0.31 GHz. The well calibrated ARCADE 2 maps provide a new test for spinning dust emission, based on the integrated intensity of emission from the Galactic plane instead of cross-correlations with the thermal dust spatial morphology. The Galactic plane intensity measured by ARCADE 2 is fainter than predicted by models without spinning dust, and is consistent with spinning dust contributing 0.4 +/- 0.1 of the Galactic plane emission at 23 GHz.

  7. Discovery of radio emission from AE Aquarii

    SciTech Connect

    Bookbinder, J.A.; Lamb, D.Q.

    1987-12-01

    VLA 1.4-GHz and 4.9-GHz observations of six DQ Her cataclysmic variables, obtained in the C/D hybrid configuration with 50-MHz bandwidth, 7-sec time resolution, and limiting flux density about 200 microJy on July 21, 1984, are reported. Variable radio emission with time scale less than 5 min, circular polarization less than 15 percent, and flux density 3-5 mJy at 1.4 GHz and 8-16 mJy at 4.9 GHz is detected from AE Aqr. This emission is tentatively attributed to synchrotron emission from mildly relativistic electrons, powered by the MHD torque coupling the magnetic white dwarf to either (1) a secondary with a strong magnetic field or (2) an accretion disk. 20 references.

  8. Discovery of radio emission from AE Aquarii

    NASA Technical Reports Server (NTRS)

    Bookbinder, J. A.; Lamb, D. Q.

    1987-01-01

    VLA 1.4-GHz and 4.9-GHz observations of six DQ Her cataclysmic variables, obtained in the C/D hybrid configuration with 50-MHz bandwidth, 7-sec time resolution, and limiting flux density about 200 microJy on July 21, 1984, are reported. Variable radio emission with time scale less than 5 min, circular polarization less than 15 percent, and flux density 3-5 mJy at 1.4 GHz and 8-16 mJy at 4.9 GHz is detected from AE Aqr. This emission is tentatively attributed to synchrotron emission from mildly relativistic electrons, powered by the MHD torque coupling the magnetic white dwarf to either (1) a secondary with a strong magnetic field or (2) an accretion disk.

  9. DETECTION OF RADIO EMISSION FROM FIREBALLS

    SciTech Connect

    Obenberger, K. S.; Taylor, G. B.; Dowell, J.; Henning, P. A.; Schinzel, F. K.; Stovall, K.; Hartman, J. M.; Ellingson, S. W.; Helmboldt, J. F.; Wilson, T. L.; Kavic, M.; Simonetti, J. H.

    2014-06-20

    We present the findings from the Prototype All-Sky Imager, a back end correlator of the first station of the Long Wavelength Array, which has recorded over 11,000 hr of all-sky images at frequencies between 25 and 75 MHz. In a search of this data for radio transients, we have found 49 long-duration (10 s of seconds) transients. Ten of these transients correlate both spatially and temporally with large meteors (fireballs), and their signatures suggest that fireballs emit a previously undiscovered low frequency, non-thermal pulse. This emission provides a new probe into the physics of meteors and identifies a new form of naturally occurring radio transient foreground.

  10. The Radio Wave Emission from Sgr A*

    NASA Astrophysics Data System (ADS)

    Beaklini, Pedro Paulo Bonetti

    2008-10-01

    SgrA* is a compact radio source, with radius smaller than 1 AU. Its position is coincident with the dynamic center of a star cluster that orbits the 4 million solar mass supermassive black hole found in the center of the Milky Way. SgrA* is surrounded by a complex of HII regions, with complex morphology, named SgrA. The variability of the SgrA* emission was observed at different wavelengths, as radio, infrared and X-rays, with timescales that range from hours to months. Recent observations using interferometric techniques have detected a quasiperiodicity in the radio light curve from SgrA*. In our work, we present the result of 43 GHz observations obtained with the Itapetinga radiotelescope, located in Atibaia, which aimed to detect this variability and verify the existence of a periodicity. Sgr B2, an HII complex near SgrA*, was used as a calibrator to eliminate any extrinsic variability. The obtained light curve is consistent with previous results reported in the literature, confirming the increase in the amplitude of the variability with frequency. Particularly, daily variability was found that is compatible with what was reported at 7 mm using VLBI techniques. The expected 106 days periodicity was not found in our data by the Jurkevich statistic method, which instead indicated the existence of a 90 day period. However, the superposition of the 7 mm data on a 106 day look similar to what was found from the 1.3 cm observations. Considering that the observations at 7 mm do not cover all the phases in the full cycle, more observations are needed to confirm the existence of a periodicity in the light curve.

  11. 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.

  12. Phenomenology of Neptune's radio emissions observed by the Voyager planetary radio astronomy experiment

    NASA Technical Reports Server (NTRS)

    Pedersen, B. M.; Lecacheux, A.; Zarka, P.; Aubier, M. G.; Kaiser, M. L.; Desch, M. D.

    1992-01-01

    The Neptune flyby in 1989 added a new planet to the known number of magnetized planets generating nonthermal radio emissions. We review the Neptunian radio emission morphology as observed by the planetary radio astronomy experiment on board Voyager 2 during a few weeks before and after closest approach. We present the characteristics of the two observed recurrent main components of the Neptunian kilometric radiation, i.e., the 'smooth' and the 'bursty' emissions, and we describe the many specific features of the radio spectrum during closest approach.

  13. U. radio emission from quiescent filaments

    NASA Technical Reports Server (NTRS)

    Lang, Kenneth R.

    1989-01-01

    Full-disk Very Large Array (VLA) synthesis maps of the quiet Sun indicate that filaments can be seen in emission at 91.6 cm wavelength; they are detected in absorption at shorter microwave wavelengths. The 91.6 cm emission has a brightness temperature of T sub B = 3 x 10(exp 5) K. It is hotter, wider and longer than the underlying filament detected at H alpha wavelengths, but the similarity between the shape, position, elongation and orientation of the radio and optical features suggests their close association. The 91.6 cm emission is attributed to the thermal-bremsstrahlung of a hot transition sheath that envelopes the H alpha filament and acts as an interface between the cool, dense H alpha filament and the hotter, rarefied corona. The transition sheath is seen in emission because of the lower optical depth of the corona at 90 cm wavelength, and the width of this sheet is 10(exp 9) cm. A power law gradient in pressure provides a better match to the observations than a constant pressure model; definitive tests of theoretical models await simultaneous multi-wavelength studies of filaments at different observing angles. When the thermal bremsstrahlung is optically thin, the magnetic field strength in the transition sheath can be inferred from the observed circular polarization. Variable physical parameters of the sheath, such as width, electron density, and electron temperature, can explain controversial reports of the detection of, or the failure to detect, the meter-wavelength counterpart of H alpha filaments.

  14. Neptune's non-thermal radio emissions - Phenomenology and source locations

    NASA Technical Reports Server (NTRS)

    Rabl, Gerald K. F.; Ladreiter, H.-P.; Rucker, Helmut O.; Kaiser, Michael L.

    1992-01-01

    During the inbound and the outbound leg of Voyager 2's encounter with Neptune, the Planetary Radio Astronomy (PRA) experiment aboard the spacecraft detected short radio bursts at frequencies within the range of about 500-1300 kHz, and broad-banded smoothly varying emission patterns within the frequency range from about 40-800 kHz. Both emissions can be described in terms of a period of 16.1 hours determining Neptune's rotation period. Furthermore, just near closest approach, a narrow-banded smoothly varying radio component was observed occurring between 600 and 800 kHz. After giving a brief overview about some general characteristics of Neptune's nonthermal radio emission, the source locations of Neptune's emission components are determined, using an offset tilted dipole model for Neptune's magnetic field. Assuming that the emission originates near the electron gyrofrequency a geometrical beaming model is developed in order to fit the observed emission episodes.

  15. Amalthea's Modulation of Jovian Decametric Radio Emission

    NASA Astrophysics Data System (ADS)

    Arkhypov, Oleksiy V.

    2006-08-01

    Institute of Radio Astronomy, National Academy of Sciences of Ukraine, Kharkiv, Ukraine Amalthea is the largest body after Galilean satellites near Jupiter. An anomaly in Jovian synchrotron radiation has been found just on the Amalthea magnetic shell (de Pater, Schulz & Brecht 1997). It has been suggested that Amalthea's motion through Jupiter's magnetic field induces Alfvén or whistler wings or electrostatic high-frequency waves which lead to the pitch angle scattering. It is reasonable to search for another effect of these processes: magnetospheric inhomogeneities which could be found via scattering of Jovian decametric radio emission (DAM). Such scattering on field-aligned inhomogeneities in the Io plasma torus is known as "modulation lanes" in DAM dynamic spectra. To search for analogous Amalthea's modulation, the positions and frequency drift of about 600 lanes are measured on the UFRO spectra of DAM. The special 3D algorithm is used for localization of field-aligned magnetospheric inhomogeneities by the frequency drift of modulation lanes. It is found that about 4% of the lanes are clustered near Amalthea's magnetic shell. There are two such clusters near longitudes of 123°≤λ[III]≤140° and 284°≤λ[III]≤305°, which coincide with the regions of maximum compression of fresh plasma due to rotating magnetic field of Jupiter (where ∂(B^2)/∂λ[III]) is maximal). The Amalthea modulation could explain the enigmatic "hf-lanes" (Genova, Aubier & Lecacheux 1981). The found magnetospheric formations are a new argument for the ice nature of Amalthea which has the density less than that of water (Anderson et al. 2005). Anderson J.D. et al. 2005, Science, 308, 5726, pp. 1291-1293. de Pater I., Schulz M., Brecht S.H. 1997, J. Geophys. Res., 102, A10, pp. 22043-22064. Genova F., Aubier M.G., Lecacheux A. 1981, Astron. and Astrophys. 104, 2, pp. 229-239.

  16. Solar wind control of Jupiter's hectometric radio emission

    NASA Technical Reports Server (NTRS)

    Barrow, C. H.; Desch, M. D.

    1989-01-01

    Radio, plasma, and magnetic field data obtained by Voyager 1 and Voyager 2 were used to examine the manner in which the Jovian hectometric radio emission (HOM) is controlled by the solar wind. Using the method of superposed epochs, it was found that the higher energy HOM is correlated with the IMF as well as with the solar wind density and pressure. However, unlike the Io-independent decametric radio emission (Non-Io DAM), the HOM displayed no correlation with the solar wind velocity, although this radio component appear to be also influenced by the IMF. The results suggest separate HOM amd Non-Io DAM sources.

  17. RADIO AND GAMMA-RAY PULSED EMISSION FROM MILLISECOND PULSARS

    SciTech Connect

    Du, Y. J.; Chen, D.; Qiao, G. J.

    2013-01-20

    Pulsed {gamma}-ray emission from millisecond pulsars (MSPs) has been detected by the sensitive Fermi space telescope, which sheds light on studies of the emission region and its mechanism. In particular, the specific patterns of radio and {gamma}-ray emission from PSR J0101-6422 challenge the popular pulsar models, e.g., outer gap and two-pole caustic models. Using the three-dimensional annular gap model, we have jointly simulated radio and {gamma}-ray light curves for three representative MSPs (PSR J0034-0534, PSR J0101-6422, and PSR J0437-4715) with distinct radio phase lags, and present the best simulated results for these MSPs, particularly for PSR J0101-6422 with complex radio and {gamma}-ray pulse profiles, and for PSR J0437-4715 with a radio interpulse. We have found that both the {gamma}-ray and radio emission originate from the annular gap region located in only one magnetic pole, and the radio emission region is not primarily lower than the {gamma}-ray region in most cases. In addition, the annular gap model with a small magnetic inclination angle instead of an 'orthogonal rotator' can account for the MSPs' radio interpulse with a large phase separation from the main pulse. The annular gap model is a self-consistent model not only for young pulsars but also MSPs, and multi-wavelength light curves can be fundamentally explained using this model.

  18. On the proposed triggering of Jovian radio emissions

    NASA Astrophysics Data System (ADS)

    Desch, M. D.; Kaiser, M. L.

    1985-09-01

    Calvert (1985) has proposed that solar type III radio bursts can trigger the onset of certain Jovian hectometer wavelength emissions. The authors show, using the data obtained by the Voyager Planetary Radio Astronomy experiment, that this triggering hypothesis is not supported statistically. Furthermore, the authors question the causality of this proposed triggering because much of the Jovian hectometer emission is due to a quasi-continuous radio source rotating, in lighthouse fashion, with Jupiter. Thus, an observed "onset" of emission is simply a function of the observer's position in local time around Jupiter.

  19. On the proposed triggering of Jovian radio emissions

    NASA Technical Reports Server (NTRS)

    Desch, M. D.; Kaiser, M. L.

    1985-01-01

    Calvert (1985) has proposed that a solar type III radio bursts can trigger the onset of certain Jovian hectometer wavelength emissions. It is shown, using the data obtained by the Voyager Planetary Radio Astronomy experiment, that this triggering hypothesis is not supported statistically. Furthermore, the causality of this proposed triggering is questioned because much of the Jovian hectometer emission is due to a quasi-continuous radio source rotating, in lighthouse fashion, with Jupiter. Thus, an observed 'onset' of emission is simply a function of the observer's position in local time around Jupiter.

  20. Correlation of radio and gamma emissions in lightning initiation.

    PubMed

    Gurevich, A V; Antonova, V P; Chubenko, A P; Karashtin, A N; Mitko, G G; Ptitsyn, M O; Ryabov, V A; Shepetov, A L; Shlyugaev, Yu V; Thu, W M; Vildanova, L I; Zybin, K P

    2013-10-18

    The results of simultaneous radio and gamma emission measurements during thunderstorms are presented. A gamma detector situated at the height 3840 m and two radio detectors of Tien-Shan Mountain Scientific Station (altitude 3340 m) registered intensive gamma flashes and radio pulses during the time of lightning initiation. The radio-gamma correlation grows abruptly at the initial moment (a few hundred microseconds), and the correlation coefficient reaches 0.9-0.95. The gamma-energy spectrum measured during lightning initiation is close to the characteristic spectrum of runaway breakdown. Radio pulses observed at the same time have highest amplitudes. Combined observation of gamma and radio emissions confirm the conception of lightning initiation due to multiple simultaneous electric discharges at hydrometeors stimulated and synchronized by low-energy electrons generated in the runaway breakdown process. PMID:24182272

  1. Fossil shell emission in dying radio loud AGNs

    NASA Astrophysics Data System (ADS)

    Kino, M.; Ito, H.; Kawakatu, N.; Orienti, M.; Nagai, H.; Wajima, K.; Itoh, R.

    2016-02-01

    We investigate shell emission associated with dying radio loud AGNs. First, based on our recent work by Ito et al. (2015), we describe the dynamical and spectral evolution of shells after stopping the jet energy injection. We find that the shell emission overwhelms that of the radio lobes soon after stopping the jet energy injection because fresh electrons are continuously supplied into the shell via the forward shock, while the radio lobes rapidly fade out without jet energy injection. We find that such fossil shells can be a new class of target sources for SKA telescope. Next, we apply the model to the nearby radio source 3C84. Then, we find that the fossil shell emission in 3C84 is less luminous in the radio band while it is bright in the TeV γ-ray band and can be detectable by CTA. Data from STELLA

  2. Analysis of Jovian decamteric data: Study of radio emission mechanisms

    NASA Technical Reports Server (NTRS)

    Staelin, D. H.; Rosenkranz, P. W.; Arias, T. A.; Garnavich, P. N.; Hammerschlag, R.

    1986-01-01

    This research effort involved careful examination of Jovian radio emission data below 40 MHz, with emphasis on the informative observations of the Planetary Radio Astronomy experiment (PRA) on the Voyager 1 and 2 spacecraft. The work is divided into three sections, decametric arcs, decametric V bursts, and hectometric modulated spectral activity (MSA).

  3. Radio emissions from terrestrial planets around white dwarfs

    NASA Astrophysics Data System (ADS)

    Willes, A. J.; Wu, K.

    2005-03-01

    Terrestrial planets in close orbits around magnetic white dwarf stars are potential electron-cyclotron maser sources, by analogy to planetary radio emissions generated from the electrodynamic interaction between Jupiter and the Galilean moons. We present predictions of radio flux densities and the number of detectable white-dwarf/terrestrial-planet systems, and discuss a scenario for their formation.

  4. Neptune radio emission in dipole and multipole magnetic fields

    NASA Technical Reports Server (NTRS)

    Sawyer, C. B.; King, N. V.; Romig, J. H.; Warwick, J. W.

    1995-01-01

    We study Neptune's smooth radio emission in two ways: we simulate the observations and we then consider the radio effects of Neptune's magnetic multipoles. A procedure to deduce the characteristics of radio sources observed by the Planetary Radio Astronomy experiment minimizes limiting assumptions and maximizes use of the data, including quantitative measurement of circular polarization. Study of specific sources simulates time variation of intensity and apparent polarization of their integrated emission over an extended time period. The method is applied to Neptune smooth recurrent emission (SRE). Time series are modeled with both broad and beamed emission patterns, and at two frequencies which exhibit different time variation of polarization. These dipole-based results are overturned by consideration of more complex models of Neptune's magnetic field. Any smooth emission from the anticipated auroral radio source is weak and briefly observed. Dominant SRE originates complex fields at midlatitude. Possible SRE source locations overlap that of 'high-latitude' emission (HLE) between +(out) and -(in) quadrupoles. This is the first identification of multipolar magnetic structure with a major source of planetary radio emission.

  5. Satellite Emission Radio Interferometric Earth Surveying (SERIES). [astrometry

    NASA Technical Reports Server (NTRS)

    Macdoran, P. F.

    1980-01-01

    Existing satellite radio emissions of the global positioning system were exploited as a resource for cost effective high accuracy geodetic measurements. System applications were directed toward crustal dynamics and earthquake research.

  6. Evidence for solar wind control of Saturn radio emission

    NASA Technical Reports Server (NTRS)

    Desch, M. D.

    1982-01-01

    Using data collected by the Voyager 1 and 2 spacecraft in 1980 and 1981, strong evidence is presented for a direct correlation between variations in the solar wind at Saturn and the level of activity of Saturn's nonthermal radio emission. Correlation coefficients of 57 to 58% are reached at lag times of 0 to 1 days between the arrival at Saturn of high pressure solar wind streams and the onset of increased radio emission. The radio emission exhibits a long-term periodicity of 25 days, identical to the periodicity seen in the solar wind at this time and consistent with the solar rotation period. The energy coupling efficiency between the solar wind with the Saturn radio emission is estimated and compared with that for Earth.

  7. Near Earth space sporadic radio emission busts occurring during sunrise

    NASA Technical Reports Server (NTRS)

    Dudnik, A. V.; Zaljubovsky, I. I.; Kartashev, V. M.; Lasarev, A. V.; Shmatko, E. S.

    1985-01-01

    During the period of low solar activity at sunrise the effect of sporadic high frequency near Earth space radio emission was experimentally discovered at middle latitudes. The possible mechanism of its origin is discussed.

  8. Evidence for extended radio emission surrounding RX Puppis

    NASA Technical Reports Server (NTRS)

    Hollis, J. M.; Oliversen, R. J.; Michalitsianos, A. G.; Kafatos, M.

    1986-01-01

    Evidence for an approximately 1-arcsec extended structure in 6 cm continuum emission emanating from the symbiotic star system RX Puppis is reported. Hourly continuum flux changes were not detected as suggested in previous radio experiments by others. The observations indicate that the predominant nature of the radio emission is thermal and consistent with an optically thick stellar wind emanating from the symbiotic star system. The results presented here are discussed with regard to other similar stellar binary systems.

  9. The Radio Emission Of Radio Quiet Quasars - A New Working Hypothesis

    NASA Astrophysics Data System (ADS)

    Laor, Ari; Behar, E.

    2009-12-01

    What is the origin of radio emission in radio quiet Active Galactic Nuclei? In radio loud AGN the answer is clear, jet emission. In RQ AGN, which are 103 times weaker, the answer is not established yet, but it is commonly thought to originate in a weak jet. RQ AGN display a significant correlation between the radio luminosity (LR) and X-ray luminosity (LX), with LR 10-5 LX. A very similar correlation, known as the Guedel-Benz relation, holds for coronally active stars. The Guedel-Benz relation strongly suggests that stellar coronae are magnetically heated. In AGN the X-ray emission is also thought to originate in a magnetically heated corona, and thus it is natural to associate their radio emission with coronal activity as well. The radio emission may thus serve as a probe for physical processes in AGN coronae, as it does in stellar coronae. I will discuss some predictions, based on this hypothesis, on the likely radio spectrum, its variability, and its relation to the X-ray variability.

  10. Characterizing the radio continuum emission from intense starburst galaxies

    NASA Astrophysics Data System (ADS)

    Galvin, T. J.; Seymour, N.; Filipović, M. D.; Tothill, N. F. H.; Marvil, J.; Drouart, G.; Symeonidis, M.; Huynh, M. T.

    2016-09-01

    The intrinsic thermal (free-free) and non-thermal (synchrotron) emission components that comprise the radio continuum of galaxies represent unique, dust-free measures of star formation rates (SFR). Such high SFR galaxies will dominate the deepest current and future radio surveys. We disentangle the thermal and non-thermal emission components of the radio continuum of six ultraluminous infrared galaxies (LFIR > 1012.5 L⊙) at redshifts of 0.2 ≤ z ≤ 0.5 and 22 IR selected galaxies. Radio data over a wide frequency range (0.8 < ν < 10 GHz) are fitted with a star-forming galaxy model comprising of thermal and non-thermal components. The luminosities of both radio continuum components are strongly correlated to the 60 μm luminosity across many orders of magnitude (consistent with the far-IR to radio correlation). We demonstrate that the spectral index of the radio continuum spectral energy distribution is a useful proxy for the thermal fraction. We also find that there is an increase in mean and scatter of the thermal fraction with FIR to radio luminosity ratio which could be influenced by different time-scales of the thermal and non-thermal emission mechanisms.

  11. Analysis of Jovian decametric data: Study of radio emission mechanisms

    NASA Technical Reports Server (NTRS)

    Staelin, D. H.; Arias, T. A.; Garnavich, P. M.; Rosenkranz, P. W.

    1985-01-01

    The Voyager 1 and Voyager 2 Planetary Radio Astronomy Experiments (PRA) have produced the finest set of Jovian decametric radio emission data ever obtained. Jovian decametric L-burst and S-burst arcs were characterized and the data reconciled with models for the radio emission geometry and mechanisms. The first major results involve comparisons of the distribution of arc separations with longitudes. The identification and analyses of systematic variations in the PRA data have yielded interesting results, but only the most obvious features of the data were examined. Analyses of the PRA data were extended with the use of new 6-Sec formats that are more sensitive to the S-bursts.

  12. Diffuse Radio Emission in the Galaxy Cluster Abell 754

    NASA Astrophysics Data System (ADS)

    Kale, R.; Dwarakanath, K. S.

    2009-09-01

    We present a low frequency (<1.4GHz) study of the diffuse radio halo and relic emission in the galaxy cluster Abell 0754. Images at 150 MHz made using the Giant Metrewave Radio Telescope (GMRT) revealed 4 diffuse features; 3 of which are new. Images at 330 and 1363 MHz were created using archival data from the GMRT and the VLA respectively. These yield synchrotron spectral indices, α (S ∝ν-α), steeper than 2 for the new features. Adiabatic compression of fossil radio galaxy cocoon by shocks can lead to the formation of radio relics (Ensslin & Gopal-Krishna, 2001). In the framework of this model we find that the relic in A754 can be explained as a lurking cocoon of a radio galaxy; no shock compression is required to produce this emission. The implications of this result to the merger scenario in A754 are discussed.

  13. Affirmation of triggered Jovian radio emissions and their attribution to corotating radio lasers

    NASA Technical Reports Server (NTRS)

    Calvert, W.

    1985-01-01

    It is argued that the original statistical evidence for the existence of triggered radio emissions and corotating radio lasers on Jupiter remains valid notwithstanding the critique of Desch and Kaiser (1985). The Voyager radio spectrograms used to identify the triggered emissions are analyzed and the results are discussed. It is shown that the critique by Desch and Kaiser is unjustified because it is not based on the original event criteria, i.e., the correlation between the occurrence of Jovian auroral kilometric radiation and fast-drift type III solar bursts in the same frequency.

  14. On the origin of radio emission in radio-quiet quasars

    NASA Astrophysics Data System (ADS)

    Laor, Ari; Behar, Ehud

    2008-10-01

    The radio emission in radio-loud quasars originates in a jet carrying relativistic electrons. In radio-quiet quasars (RQQs) the relative radio emission is ~103 times weaker, and its origin is not established yet. We show here that there is a strong correlation between the radio luminosity (LR) and X-ray luminosity (LX) with LR ~ 10-5 LX, for the radio-quiet Palomar-Green (PG) quasar sample. The sample is optically selected, with nearly complete radio and X-ray detections, and thus this correlation cannot be due to direct selection biases. The PG quasars lie on an extension of a similar correlation noted by Panessa et al., for a small sample of nearby low-luminosity type 1 active galactic nuclei (AGN). A remarkably similar correlation, known as the Güdel-Benz relation, where LR/LX ~ 10-5, holds for coronally active stars. The Güdel-Benz relation, together with correlated stellar X-ray and radio variability, implies that the coronae are magnetically heated. We therefore raise the possibility that AGN coronae are also magnetically heated, and that the radio emission in RQQ also originates in coronal activity. If correct, then RQQ should generally display compact flat cores at a few GHz due to synchrotron self-absorption, while at a few hundred GHz we should be able to see directly the X-ray emitting corona, and relatively rapid and large amplitude variability, correlated with the X-ray variability, is likely to be seen. We also discuss possible evidence that the radio and X-ray emission in ultraluminous X-ray sources and Galactic black holes may be of coronal origin as well.

  15. X-RAY EMISSION FROM OPTICALLY SELECTED RADIO-INTERMEDIATE AND RADIO-LOUD QUASARS

    SciTech Connect

    Miller, B. P.; Brandt, W. N.; Schneider, D. P.; Wu Jianfeng; Gibson, R. R.; Steffen, A. T. E-mail: niel@astro.psu.edu E-mail: jfwu@astro.psu.edu E-mail: rgibson@astro.washington.edu

    2011-01-01

    We present the results of an investigation into the X-ray properties of radio-intermediate and radio-loud quasars (RIQs and RLQs, respectively). We combine large, modern optical (e.g., SDSS) and radio (e.g., FIRST) surveys with archival X-ray data from Chandra, XMM-Newton, and ROSAT to generate an optically selected sample that includes 188 RIQs and 603 RLQs. This sample is constructed independently of X-ray properties but has a high X-ray detection rate (85%); it provides broad and dense coverage of the l-z plane, including at high redshifts (22% of objects have z = 2-5), and it extends to high radio-loudness values (33% of objects have R* = 3-5, using logarithmic units). We measure the 'excess' X-ray luminosity of RIQs and RLQs relative to radio-quiet quasars (RQQs) as a function of radio loudness and luminosity, and parameterize the X-ray luminosity of RIQs and RLQs both as a function of optical/UV luminosity and also as a joint function of optical/UV and radio luminosity. RIQs are only modestly X-ray bright relative to RQQs; it is only at high values of radio loudness (R* {approx}> 3.5) and radio luminosity that RLQs become strongly X-ray bright. We find no evidence for evolution in the X-ray properties of RIQs and RLQs with redshift (implying jet-linked IC/CMB emission does not contribute substantially to the nuclear X-ray continuum). Finally, we consider a model in which the nuclear X-ray emission contains both disk/corona-linked and jet-linked components and demonstrate that the X-ray jet-linked emission is likely beamed but to a lesser degree than applies to the radio jet. This model is used to investigate the increasing dominance of jet-linked X-ray emission at low inclinations.

  16. ON THE ORIGIN OF RADIO EMISSION FROM MAGNETARS

    SciTech Connect

    Szary, Andrzej; Melikidze, George I.; Gil, Janusz

    2015-02-10

    Magnetars are the most magnetized objects in the known universe. Powered by the magnetic energy, and not by the rotational energy as in the case of radio pulsars, they have long been regarded as a completely different class of neutron stars. The discovery of pulsed radio emission from a few magnetars weakened the idea of a clean separation between magnetars and normal pulsars. We use the partially screened gap (PSG) model to explain radio emission of magnetars. The PSG model requires that the temperature of the polar cap is equal to the so-called critical value, i.e., the temperature at which the thermal ions outflowing from the stellar surface screen the acceleration gap. We show that a magnetar has to fulfill the temperature, power, and visibility conditions in order to emit radio waves. First, in order to form PSG, the residual temperature of the surface has to be lower than the critical value. Second, since the radio emission is powered by the rotational energy, it has to be high enough to enable heating of the polar cap by backstreaming particles to the critical temperature. Finally, the structure of the magnetic field has to be altered by magnetospheric currents in order to widen a radio beam and increase the probability of detection. Our approach allows us to predict whether a magnetar can emit radio waves using only its rotational period, period derivative, and surface temperature in the quiescent mode.

  17. Spontaneous Radio Frequency Emissions from Natural Aurora. Chapter 4

    NASA Technical Reports Server (NTRS)

    LaBelle, J.

    2009-01-01

    At high latitudes, suitably sensitive radio experiments tuned below 5 MHz detect up to three types of spontaneous radio emissions from the Earth s ionosphere. In recent years, ground-based and rocket-borne experiments have provided strong evidence for theoretical explanations of the generation mechanism of some of these emissions, but others remain unexplained. Achieving a thorough understanding of these ionospheric emissions, accessible to ground-based experiments, will not only bring a deeper understanding of Earth s radio environment and the interactions between waves and particles in the ionosphere but also shed light on similar spontaneous emissions occurring elsewhere in Earth s environment as well as other planetary and stellar atmospheres.

  18. The Far-Infrared Emission of Radio Loud and Radio Quiet Quasars

    NASA Technical Reports Server (NTRS)

    Polletta, M.; Courvoisier, T. J.-L.; Wilkes, B. J.; Hooper, E. J.

    2000-01-01

    Continuum observations at radio, millimeter, infrared and soft X-ray energies are presented for a sample of 22 quasars, consisting of flat and steep spectrum radio loud, radio intermediate and radio quiet objects. The primary observational distinctions, among the different kinds of quasars in the radio and IR energy domains are studied using large observational datasets provided by ISOPHOT on board the Infrared Space Observatory, by the IRAM interferometer, by the sub-millimetre array SCUBA on JCMT, and by the European Southern Observatory (ESO) facilities IRAC1 on the 2.2 m telescope and SEST. The spectral energy distributions of all quasars from radio to IR energies are analyzed and modeled with non-thermal and thermal spectral components. The dominant mechanism emitting in the far/mid-IR is thermal dust emission in all quasars, with the exception of flat spectrum radio loud quasars for which the presence of thermal IR emission remains rather uncertain, since it is difficult to separate it from the bright non-thermal component. The dust is predominantly heated by the optical/ultraviolet radiation emitted from the external components of the AGN. A starburst contributes to the IR emission at different levels, but always less than the AGN (<= 27%). The distribution of temperatures, sizes, masses, and luminosities of the emitting dust are independent of the quasar type.

  19. Physics of radio emission in gamma-ray pulsars

    NASA Astrophysics Data System (ADS)

    Petrova, S. A.

    2016-02-01

    > Propagation of radio emission in a pulsar magnetosphere is reviewed. The effects of polarization transfer, induced scattering and reprocessing to high energies are analysed with a special emphasis on the implications for the gamma-ray pulsars. The possibilities of the pulsar plasma diagnostics based on the observed radio pulse characteristics are also outlined. As an example, the plasma number density profiles obtained from the polarization data for the Vela and the gamma-ray millisecond pulsars J1446-4701, J1939+2134 and J1744-1134 are presented. The number densities derived tend to be the highest/lowest when the radio pulse leads/lags the gamma-ray peak. In the PSR J1939+2134, the plasma density profiles for the main pulse and interpulse appear to fit exactly the same curve, testifying to the origin of both radio components above the same magnetic pole and their propagation through the same plasma flow in opposite directions. The millisecond radio pulse components exhibiting flat position angle curves are suggested to result from the induced scattering of the main pulse by the same particles that generate gamma rays. This is believed to underlie the wide-sense radio/gamma-ray correlation in the millisecond pulsars. The radio quietness of young gamma-ray pulsars is attributed to resonant absorption, whereas the radio loudness to the radio beam escape through the periphery of the open field line tube.

  20. Dynamic Spectra Predicted for 2-3 Khz Radio Emission

    NASA Astrophysics Data System (ADS)

    Mitchell, Jeremy J.; Cairns, Iver H.; Robinson, Peter A.

    Radio emissions observed at 2-3 kHz by the Voyager spacecraft occur when global merged interaction regions (GMIRs) reach the heliopause. The radiation is thought to occur when a GMIR enters a region close to the heliopause where the electron speed distribution is primed with a superthermal tail produced by lower hybrid drive. Previously this priming mechanism was combined with a theory for type II solar radio bursts to predict the flux of radio emission in the outer heliosphere. Here this theory is extended in two ways. First theoretical arguments regarding the availability of Langmuir and ion sound waves are used to determine whether emission occurs via three wave processes or processes involving wave scattering off thermal ions (STI). New expressions for conversion efficiencies into radio emission associated with STI are then implemented where appropriate. Second dynamic spectra are calculated for the radio emission generated by shock from the inner solar wind to beyond the heliopause. The results are then compared with existing Voyager observations.

  1. On Polarization of the Zebra Pattern in Solar Radio Emission

    NASA Astrophysics Data System (ADS)

    Zlotnik, E. Y.; Zaitsev, V. V.; Altyntsev, A. T.

    2014-01-01

    The problem of strong polarization of the zebra-type fine structure in solar radio emission is discussed. In the framework of the plasma mechanism of radiation at the levels of the double plasma resonance, the polarization of the observed radio emission may be due to a difference in rates of plasma wave conversion into ordinary and extraordinary waves or different conditions of escaping of these waves from the source. In a weakly anisotropic plasma which is a source of the zebra-pattern with rather large harmonic numbers, the degree of polarization of the radio emission at twice the plasma frequency originating from the coalescence of two plasma waves is proportional to the ratio of the electron gyrofrequency to the plasma frequency, which is a small number and is negligible. Noticeable polarization can therefore arise only if the observed radio emission is a result of plasma wave scattering by ions (including induced scattering) or their coalescence with low-frequency waves. In this case, the ordinary mode freely leaves the source, but the extraordinary mode gets into the decay zone and does not exit from the source. As a result, the outgoing radio emission can be strongly polarized as the ordinary mode. Possible reasons for the polarization of the zebra pattern in the microwave region are discussed.

  2. Satellite emission radio interferometric earth surveying series - GPS geodetic system

    NASA Technical Reports Server (NTRS)

    Macdoran, P. F.

    1979-01-01

    A concept called SERIES (satellite emissions radio interferometric earth surveying) which makes use of GPS (global positioning system) radio transmissions without any satellite modifications, is described. Through the use of very long baseline interferometry (VLBI) and its calibration methods, 0.5 to 3 cm three dimensional baseline accuracy can be achieved over distances of 2 to 200 km respectively, with only 2 hours of on-site data acquisition. Attention is given to such areas as: the radio flux equivalent of GPS transmissions, synthesized delay precision, transmission and frequency subsystem requirements, tropospheric and ionospheric errors. Applications covered include geodesy and seismic tectonics.

  3. The relation between infrared and radio emission in spiral galaxies

    NASA Technical Reports Server (NTRS)

    Helou, George

    1991-01-01

    A remarkable correlation between the far infrared and the radio continuum emission of star forming galaxies was one of the early results based on IRAS data, and has remained one of the most intriguing. Recent work has extended the correlation to early type galaxies, revealing a slightly different ratio in lenticulars. When radio and infrared maps of disk galaxies are compared, the radio disks appear systematically more diffuse. This has been interpreted as a manifestation of the diffusion of cosmic-ray electrons, and has allowed a fresh look at the behavior of magnetic fields and cosmic rays in spiral galaxies, and at their relation to the rest of the interstellar medium.

  4. Source localization of Jupiter's Io dependent radio emissions

    NASA Technical Reports Server (NTRS)

    Aubier, Monique G.; Genova, Francoise; Calvert, Wynne

    1988-01-01

    The peak frequencies of the Io-dependent part of the Jovian emissions are compared with the surface gyrofrequency determined from Jovian magnetic models in order to localize the source of Jovian radio emissions. The bulk of the Io-controlled emissions was found to be delayed by up to 70 deg of equatorial longitude from the predicted instantaneous position of the Io flux tube, with the L and S emissions both displaying this same unexpected behavior. It is suggested that the source of these emissions is delayed substantially with respect to Io either as an Alfven-wave delay or because of errors in the magnetic field models.

  5. Analysis of Uranian radio emissions, Uranus Data Analysis Program (UDAP)

    NASA Technical Reports Server (NTRS)

    Calvert, W.

    1991-01-01

    Progress under this grant has included identifying certain new radio emission components and determining the source location of both these and the two major Uranian radio emission (the SHF and bursty components) by a unique new statistical minimization technique. This new source location technique has subsequently also been applied at Neptune, with considerable success. New radio spectrograms have been prepared to clarify the behavior of such emissions, using both the usual 48-second, log-averaged data and the original 6-second PRA data, the latter showing a number of interesting new features. Also, a plasmasphere was discovered at Uranus, auroral plasma cavities were discovered at both Uranus and Neptune, and it was found that the currently-accepted rotation period for Uranus is in error by a small amount.

  6. A model for radio emission from solar coronal shocks

    SciTech Connect

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

    2014-05-01

    Solar coronal shocks are very common phenomena in the solar atmosphere and are believed to be the drivers of solar type II radio bursts. However, the microphysical nature of these emissions is still an open question. This paper proposes that electron cyclotron maser (ECM) emission is responsible for the generation of radiation from the coronal shocks. In the present model, an energetic ion beam accelerated by the shock first excites the Alfvén wave (AW), then the excited AW leads to the formation of a density-depleted duct along the foreshock boundary of the shock. In this density-depleted duct, the energetic electron beam produced via the shock acceleration can effectively excite radio emission by ECM instability. Our results show that this model may potentially be applied to solar type II radio bursts.

  7. Possible radio emission from Uranus at 0.5 MHz

    NASA Technical Reports Server (NTRS)

    Brown, L. W.

    1975-01-01

    Radio emission from the direction of Uranus was detected in data from the radio astronomy experiment on the IMP-6 spacecraft. Previously, emission from the direction of Jupiter and Saturn was observed by the IMP-6 at a number of frequencies near 1 MHz during the period April 1971 to October 1972. These radio bursts were identified in the IMP-6 data through an analysis of the phase of the observed modulated signal detected from the spinning dipole antenna. This technique was applied to the direction of the planet Uranus with possible positive results. Over the approximately 500 days of data, three to six bursts with unique spectral characteristics were found. Identification with Uranus is confused by the likely presence of low level terrestrial and solar emission. The observed events persisted less than three minutes and are strongest in intensity near 0.5 MHz.

  8. STEADY AND TRANSIENT RADIO EMISSION FROM ULTRACOOL DWARFS

    SciTech Connect

    Osten, Rachel A.; Phan-Bao, N.; Hawley, Suzanne L.; Reid, I. Neill; Ojha, Roopesh E-mail: pbngoc@asiaa.sinica.edu.tw E-mail: inr@stsci.edu

    2009-08-01

    We present the results of multi-frequency radio observing campaigns designed to elucidate the nature of radio emission from very low mass stars. We detect radio emission in an additional two epochs of the ultracool dwarf binary LP 349-25, finding that the observed emission is broad band and steady on timescales between 10 s and 10.7 hr, as well as on timescales of 0.6 and 1.6 years. This system is unusual for ultracool dwarfs with detectable radio emission, in exhibiting a lack of any large-scale variability, particularly the bursting (periodic or aperiodic) behavior exhibited by the other objects with detectable levels of radio emission. We explore the constraints that the lack of variability on long- and short-timescales, and flat spectral index, imply about the radio-emitting structures and mechanism. The temporal constraints argue for a high latitude emitting region with a large inclination so that it is always in view, and survives for at least 0.6 years. Temporal constraints also limit the plasma conditions, implying that the electron density be n{sub e} < 4 x 10{sup 5} cm{sup -3} and B< 130 G in order not to see time variations due to collisional or radiative losses from high-energy particles. The observations and constraints provided by them are most compatible with a nonthermal radio emission mechanism, likely gyrosynchrotron emission from a spatially homogeneous or inhomogeneous source. This indicates that, similar to behaviors noted for chromospheric, transition region, and coronal plasmas in ultracool dwarfs, the magnetic activity patterns observed in active higher mass stars can survive to the substellar boundary. We also present new epochs of multi-frequency radio observations for the ultracool dwarfs 2MASS 05233822-140322 and 2MASS14563831-2809473(=LHS 3003); each has been detected in at least one previous epoch but are not detected in the epochs reported here. The results here suggest that magnetic configurations in ultracool dwarfs can be long

  9. 3D modelling of stellar auroral radio emission

    NASA Astrophysics Data System (ADS)

    Leto, P.; Trigilio, C.; Buemi, C. S.; Umana, G.; Ingallinera, A.; Cerrigone, L.

    2016-06-01

    The electron cyclotron maser is the coherent emission process that gives rise to the radio lighthouse effect observed in the hot magnetic chemically peculiar star CU Virginis. It has also been proposed to explain the highly circularly polarized radio pulses observed in some ultracool dwarfs with spectral type earlier than M7. Coherent events of this kind resemble auroral radio emission from the magnetized planets of the Solar system. In this article, we present a three-dimensional model able to simulate the timing and profile of the pulses emitted by those stars characterized by a dipolar magnetic field by following the hypothesis of the laminar source model, used to explain the beaming of terrestrial auroral kilometric radiation. This model proves to be a powerful tool with which to understand the auroral radio emission phenomenon, allowing us to derive some general conclusions about the effects of the model's free parameters on the features of coherent pulses and to learn more about the detectability of such pulsed radio emission.

  10. Detection of exomoons through observation of radio emissions

    SciTech Connect

    Noyola, J. P.; Satyal, S.; Musielak, Z. E. E-mail: ssatyal@uta.edu

    2014-08-10

    In the Jupiter-Io system, the moon's motion produces currents along the field lines that connect it to Jupiter's polar regions. The currents generate and modulate radio emissions along their paths via the electron-cyclotron maser instability. Based on this process, we suggest that such modulation of planetary radio emissions may reveal the presence of exomoons around giant planets in exoplanetary systems. A model explaining the modulation mechanism in the Jupiter-Io system is extrapolated and used to define criteria for exomoon detectability. A cautiously optimistic scenario of the possible detection of such exomoons around Epsilon Eridani b and Gliese 876 b is provided.

  11. Fine spectral structures in Jovian decametric radio emission observed by ground-based radio telescope.

    NASA Astrophysics Data System (ADS)

    Panchenko, M.; Brazhenko, A. I.; Shaposhnikov, V. E.; Konovalenko, A. A.; Rucker, H. O.

    2014-04-01

    Jupiter with the largest planetary magnetosphere in the solar system emits intense coherent non-thermal radio emission in a wide frequency range. This emission is a result of a complicated interaction between the dynamic Jovian magnetosphere and energetic particles supplying the free energy from planetary rotation and the interaction between Jupiter and the Galilean moons. Decametric radio emission (DAM) is the strongest component of Jovian radiation observed in a frequency range from few MHz up to 40 MHz. This emission is generated via cyclotron maser mechanism in sources located along Jovian magnetic field lines. Depending on the time scales the Jovian DAMexhibits different complex spectral structures. We present the observations of the Jovian decametric radio emission using the large ground-based radio telescope URAN- 2 (Poltava, Ukraine) operated in the decametric frequency range. This telescope is one of the largest low frequency telescopes in Europe equipped with high performance digital radio spectrometers. The antenna array of URAN-2 consists of 512 crossed dipoles with an effective area of 28 000m2 and beam pattern size of 3.5 x 7 deg. (at 25 MHz). The instrument enables continuous observations of the Jovian radio during long period of times. Jovian DAM was observed continuously since Sep. 2012 (depending on Jupiter visibility) with relatively high time-frequency resolution (4 kHz - 100ms) in the broad frequency range (8-32MHz). We have detected a big amount of the fine spectral structures in the dynamic spectra of DAM such as trains of S-bursts, quasi-continuous narrowband emission, narrow-band splitting events and zebra stripe-like patterns. We analyzed mainly the fine structures associated with non-Io controlled DAM. We discuss how the observed narrowband structures which most probably are related to the propagation of the decametric radiation in the Jupiter's ionosphere can be used to study the plasma parameters in the inner Jovian magnetosphere.

  12. Discussing the processes constraining the Jovian synchrotron radio emission's features

    NASA Astrophysics Data System (ADS)

    Santos-Costa, Daniel; Bolton, Scott J.

    2008-03-01

    Our recent analysis and understanding of the Jovian synchrotron radio emission with a radiation-belt model is presented. In this work, the electron population is determined by solving the Fokker-Planck diffusion equation and considering different physical processes. The results of the modeling are first compared to in situ particle data, brightness distributions, radio spectrum, and beaming curves to verify the simulated particle distributions. The dynamics of high-energy electrons in Jupiter's inner magnetosphere and their related radio emission are then examined. The results demonstrate that the Jovian moons set the extension and intensity of the synchrotron emission's brightness distribution along the magnetic equator. Simulations show that moons and dust both control the transport toward the planet by significantly reducing the abundance of particles constrained to populate, near the equator and inside 1.8 Jovian radii, the innermost region of the magnetosphere. Due to interactions with dust and synchrotron mechanism, radiation-belt electrons are moved along field lines, between Metis (1.79 Jovian radii) and Amalthea (2.54 Jovian radii), toward high latitudes. The quantity of particles transported away from the equator is sufficient to produce measurable secondary radio emissions. Among all the phenomena acting in the inner magnetosphere, the moons (Amalthea and Thebe) are the primary moderator for the radiation's intensity at high latitudes. Moon losses also affect the characteristics of the total radio flux with longitude. The sweeping effect amplifies the 10-h modulation of the beaming curve's amplitude while energy resonances occurring near Amalthea and Thebe belong to phenomena adjusting it to the right level. Interactions with dust do not significantly constrain radio spectrum features. Resonances near Amalthea and Thebe are responsible for the Jovian radio spectrum's particular slope.

  13. Radio Emissions from Plasma with Electron Kappa-Distributions

    NASA Astrophysics Data System (ADS)

    Fleishman, G. D.; Kuznetsov, A. A.

    2015-12-01

    Gregory Fleishman (New Jersey Institute of Technology, Newark, USA)Alexey Kuznetsov (Institute of Solar-Terrestrial Physics, Irkutsk, Russia), Currently there is a concern about the ability of the classical thermal (Maxwellian) distribution to describe quasisteady-state plasma in the solar atmosphere, including active regions. In particular, other distributions have been proposed to better fit observations, for example, kappa-distributions. If present, these distributions will generate radio emissions with different observable properties compared with the classical gyroresonance (GR) or free-free emission, which implies a way of remotely detecting these kappa distributions in the radio observations. Here we present analytically derived GR and free-free emissivities and absorption coefficients for the kappa-distribution, and discuss their properties, which are in fact remarkably different from the classical Maxwellian plasma. In particular, the radio brightness temperature from a gyrolayer increases with the optical depth τ for kappa-distribution. This property has a remarkable consequence allowing a straightforward observational test: the GR radio emission from the non-Maxwellian distributions is supposed to be noticeably polarized even in the optically thick case, where the emission would have strictly zero polarization in the case of Maxwellian plasma. This offers a way of remote probing the plasma distribution in astrophysical sources, including solar active regions as a vivid example. In this report, we present analytical formulae and computer codes to calculate the emission parameters. We simulate the gyroresonance emission under the conditions typical of the solar active regions and compare the results for different electron distributions. We discuss the implications of our findings for interpretation of radio observations. This work was supported in part by NSF grants AGS-1250374 and AGS-1262772, NASA grant NNX14AC87G to New Jersey Institute of Technology

  14. Mean and extreme radio properties of quasars and the origin of radio emission

    SciTech Connect

    Kratzer, Rachael M.; Richards, Gordon T.

    2015-02-01

    We investigate the evolution of both the radio-loud fraction (RLF) and (using stacking analysis) the mean radio loudness of quasars. We consider how these properties evolve as a function of redshift and luminosity, black hole (BH) mass and accretion rate, and parameters related to the dominance of a wind in the broad emission-line region. We match the FIRST source catalog to samples of luminous quasars (both spectroscopic and photometric), primarily from the Sloan Digital Sky Survey. After accounting for catastrophic errors in BH mass estimates at high redshift, we find that both the RLF and the mean radio luminosity increase for increasing BH mass and decreasing accretion rate. Similarly, both the RLF and mean radio loudness increase for quasars that are argued to have weaker radiation line driven wind components of the broad emission-line region. In agreement with past work, we find that the RLF increases with increasing optical/UV luminosity and decreasing redshift, while the mean radio loudness evolves in the exact opposite manner. This difference in behavior between the mean radio loudness and the RLF in L−z may indicate selection effects that bias our understanding of the evolution of the RLF; deeper surveys in the optical and radio are needed to resolve this discrepancy. Finally, we argue that radio-loud (RL) and radio-quiet (RQ) quasars may be parallel sequences, but where only RQ quasars at one extreme of the distribution are likely to become RL, possibly through slight differences in spin and/or merger history.

  15. Multi-Spacecraft Observations of Saturn Kilometric Radio Emission

    NASA Technical Reports Server (NTRS)

    MacDowall, R. J.; Hess, R. A.

    2011-01-01

    Saturn kilometric radiation (SKR) is the auroral radio emission of Saturn, which has been observed by Voyager 1 & 2, Cassini, and Ulysses. Ulysses is able to detect the intense intervals of SKR from distances up to 10 AU, because of its long antennas (72 m tip-to-tip) and sensitive radio receivers. Studies of SKR by A. Lecacheux gave the surprising result that the periodicity of SKR varied with time; it was not locked to a planetary rotation of Saturn. This result has been confirmed by Cassini radio observations. Here, we compare Ulysses and Cassini observations of SKR to constrain a mode! for the SKR emission geometry. SpecifIcally, we examine the question - are the brighter sources of 5KR fixed in Saturn longitude or local time? The results have significant consequences for our understanding of SKR and its varying periodicity

  16. CURVATURE-DRIFT INSTABILITY FAILS TO GENERATE PULSAR RADIO EMISSION

    SciTech Connect

    Kaganovich, Alexander; Lyubarsky, Yuri

    2010-10-01

    The curvature-drift instability has long been considered as a viable mechanism for pulsar radio emission. We reconsidered this mechanism by finding an explicit solution describing the propagation of short electromagnetic waves in a plasma flow along curved magnetic field lines. We show that even though the waves could be amplified, the amplification factor remains very close to unity; therefore, this mechanism is unable to generate high brightness temperature emission from initial weak fluctuations.

  17. ON THE EVOLUTION OF THE CORES OF RADIO SOURCES AND THEIR EXTENDED RADIO EMISSION

    SciTech Connect

    Yuan Zunli; Wang Jiancheng

    2012-01-10

    The work in this paper aims at determining the evolution and possible co-evolution of radio-loud active galactic nuclei (AGNs) and their cores via their radio luminosity functions (i.e., total and core RLFs, respectively). Using a large combined sample of 1063 radio-loud AGNs selected at low radio frequency, we investigate the RLF at 408 MHz of steep-spectrum radio sources. Our results support a luminosity-dependent evolution. Using core flux density data of the complete sample 3CRR, we investigate the core RLF at 5.0 GHz. Based on the combined sample with incomplete core flux data, we also estimate the core RLF using a modified factor of completeness. Both results are consistent and show that the comoving number density of radio cores displays a persistent decline with redshift, implying a negative density evolution. We find that the core RLF is obviously different from the total RLF at the 408 MHz band which is mainly contributed by extended lobes, implying that the cores and extended lobes could not be co-evolving at radio emission.

  18. On the Evolution of the Cores of Radio Sources and Their Extended Radio Emission

    NASA Astrophysics Data System (ADS)

    Yuan, Zunli; Wang, Jiancheng

    2012-01-01

    The work in this paper aims at determining the evolution and possible co-evolution of radio-loud active galactic nuclei (AGNs) and their cores via their radio luminosity functions (i.e., total and core RLFs, respectively). Using a large combined sample of 1063 radio-loud AGNs selected at low radio frequency, we investigate the RLF at 408 MHz of steep-spectrum radio sources. Our results support a luminosity-dependent evolution. Using core flux density data of the complete sample 3CRR, we investigate the core RLF at 5.0 GHz. Based on the combined sample with incomplete core flux data, we also estimate the core RLF using a modified factor of completeness. Both results are consistent and show that the comoving number density of radio cores displays a persistent decline with redshift, implying a negative density evolution. We find that the core RLF is obviously different from the total RLF at the 408 MHz band which is mainly contributed by extended lobes, implying that the cores and extended lobes could not be co-evolving at radio emission.

  19. Quasar feedback and the origin of radio emission in radio-quiet quasars

    NASA Astrophysics Data System (ADS)

    Zakamska, Nadia L.; Greene, Jenny E.

    2014-07-01

    We analyse Sloan Digital Sky Survey spectra of 568 obscured luminous quasars. The [O III] λ5007 Å emission line shows blueshifts and blue excess, indicating that some of the narrow-line gas is undergoing an organized outflow. The velocity width containing 90 per cent of line power ranges from 370 to 4780 km s-1, suggesting outflow velocities up to ˜2000 km s-1, and is strongly correlated with the radio luminosity among the radio-quiet quasars. We propose that radio emission in radio-quiet quasars is due to relativistic particles accelerated in the shocks within the quasar-driven outflows; star formation in quasar hosts is insufficient to explain the observed radio emission. The median radio luminosity of the sample of νLν[1.4 GHz] = 1040 erg s-1 suggests a median kinetic luminosity of the quasar-driven wind of Lwind = 3 × 1044 erg s-1, or about 4 per cent of the estimated median bolometric luminosity Lbol = 8 × 1045 erg s-1. Furthermore, the velocity width of [O III] is positively correlated with mid-infrared luminosity, which suggests that outflows are ultimately driven by the radiative output of the quasar. Emission lines characteristic of shocks in quasi-neutral medium increase with the velocity of the outflow, which we take as evidence of quasar-driven winds propagating into the interstellar medium of the host galaxy. Quasar feedback appears to operate above the threshold luminosity of Lbol ˜ 3 × 1045 erg s-1.

  20. Periodic Bursts of Jovian Non-Io Decametric Radio Emission

    NASA Technical Reports Server (NTRS)

    Panchenko, M.; Rucker, H O.; Farrell, W. M.

    2013-01-01

    During the years 2000-2011 the radio instruments onboard Cassini, Wind and STEREO spacecraft have Recorded a large amount of the Jovian decametric radio emission (DAM). In this paper we report on the analysis of the new type of Jovian periodic radio bursts recently revealed in the decametric frequency range. These bursts, which are non-Io component of DAM, are characterized by a strong periodic reoccurrence over several Jovian days with a period approx. = 1:5% longer than the rotation rate of the planet's magnetosphere (System III). The bursts are typically observed between 4 and 12 MHz and their occurrence probability has been found to be significantly higher in the sector of Jovian Central Meridian Longitude between 300 deg. and 60 deg. (via 360 deg.). The stereoscopic multispacecraft observations have shown that the radio sources of the periodic bursts radiate in a non-axisymmetric hollow cone-like pattern and sub-corotate with Jupiter remaining active during several planet's rotations. The occurrence of the periodic non-Io DAM bursts is strongly correlated with pulses of the solar wind ram pressure at Jupiter. Moreover the periodic bursts exhibit a tendency to occur in groups every approx. 25 days. The polarization measurements have shown that the periodic bursts are right hand polarized radio emission associated with the Northern magnetic hemisphere of Jupiter. We suggest that periodic non-Io DAM bursts may be connected with the interchange instability in Io plasma torus triggered by the solar wind.

  1. Periodic bursts of Jovian non-Io decametric radio emission

    PubMed Central

    Panchenko, M.; Rucker, H.O.; Farrell, W.M.

    2013-01-01

    During the years 2000–2011 the radio instruments onboard Cassini, Wind and STEREO spacecraft have recorded a large amount of the Jovian decametric radio emission (DAM). In this paper we report on the analysis of the new type of Jovian periodic radio bursts recently revealed in the decametric frequency range. These bursts, which are non-Io component of DAM, are characterized by a strong periodic reoccurrence over several Jovian days with a period ≈1.5% longer than the rotation rate of the planet's magnetosphere (System III). The bursts are typically observed between 4 and 12 MHz and their occurrence probability has been found to be significantly higher in the sector of Jovian Central Meridian Longitude between 300° and 60° (via 360°). The stereoscopic multispacecraft observations have shown that the radio sources of the periodic bursts radiate in a non-axisymmetric hollow cone-like pattern and sub-corotate with Jupiter remaining active during several planet's rotations. The occurrence of the periodic non-Io DAM bursts is strongly correlated with pulses of the solar wind ram pressure at Jupiter. Moreover the periodic bursts exhibit a tendency to occur in groups every ∼25 days. The polarization measurements have shown that the periodic bursts are right hand polarized radio emission associated with the Northern magnetic hemisphere of Jupiter. We suggest that periodic non-Io DAM bursts may be connected with the interchange instability in Io plasma torus triggered by the solar wind. PMID:23585696

  2. Periodic bursts of Jovian non-Io decametric radio emission.

    PubMed

    Panchenko, M; Rucker, H O; Farrell, W M

    2013-03-01

    During the years 2000-2011 the radio instruments onboard Cassini, Wind and STEREO spacecraft have recorded a large amount of the Jovian decametric radio emission (DAM). In this paper we report on the analysis of the new type of Jovian periodic radio bursts recently revealed in the decametric frequency range. These bursts, which are non-Io component of DAM, are characterized by a strong periodic reoccurrence over several Jovian days with a period [Formula: see text] longer than the rotation rate of the planet's magnetosphere (System III). The bursts are typically observed between 4 and 12 MHz and their occurrence probability has been found to be significantly higher in the sector of Jovian Central Meridian Longitude between 300° and 60° (via 360°). The stereoscopic multispacecraft observations have shown that the radio sources of the periodic bursts radiate in a non-axisymmetric hollow cone-like pattern and sub-corotate with Jupiter remaining active during several planet's rotations. The occurrence of the periodic non-Io DAM bursts is strongly correlated with pulses of the solar wind ram pressure at Jupiter. Moreover the periodic bursts exhibit a tendency to occur in groups every [Formula: see text] days. The polarization measurements have shown that the periodic bursts are right hand polarized radio emission associated with the Northern magnetic hemisphere of Jupiter. We suggest that periodic non-Io DAM bursts may be connected with the interchange instability in Io plasma torus triggered by the solar wind. PMID:23585696

  3. New observations of the low frequency interplanetary radio emissions

    NASA Technical Reports Server (NTRS)

    Kurth, W. S.; Gurnett, D. A.

    1991-01-01

    Recent Voyager 1 observations reveal reoccurrences of the low frequency interplanetary radio emissions. Three of the new events are weak transient events which rise in frequency from the range of 2-2.5 kHz to about 3 kHz with drift rates of approximately 1.5 kHz/year. The first of the transient events begins in mid-1989 and the more recent pair of events both were first detected in late 1991. In addition, there is an apparent onset of a 2-kHz component of the emission beginning near day 70 of 1991. The new transient emissions are barely detectable on Voyager 1 and are below the threshold of detectability on Voyager 2, which is less sensitive than Voyager 1. The new activity provides new opportunities to test various theories of the triggering, generation, and propagation of the outer heliospheric radio emissions and may signal a response of the source of the radio emissions to the increased solar activity associated with the recent peak in the solar cycle.

  4. Merger Activity and Radio Emission Within A2061

    NASA Astrophysics Data System (ADS)

    Bailey, Avery; Sarazin, Craig L.; Clarke, Tracy E.; Chatzikos, Marios; Hogge, Taylor; Wik, Daniel R.; Rudnick, Lawrence; Farnsworth, Damon; Van Weeren, Reinout J.; Brown, Shea

    2015-01-01

    Abell 2061 is a galaxy cluster located in the Corona Borealis Supercluster that boasts radio and X-ray structures indicative of a merger. A2061 is located at a redshift z = .0784, contains two brightest cluster galaxies, and has another cluster (A2067) about 2.5 Mpc to the NE, falling towards it. Within A2061, there exists an elongated structure of soft X-ray emission extending to the NE of cluster's center (referred to as the 'Plume') along with a hard X-ray shock region (the 'Shock') located just NE of the cluster's center. Previous observations in the radio have indicated the presence of a extended, central radio halo/relic accompanying the cluster's main X-ray emission but with slight NE displacement and further NE extension. Also emitting in the radio, to the SW of A2061, is a radio relic. The X-ray structures of A2061 were previously examined in 2009 by a Chandra observation. Here we present the results of an August 2013 XMM-Newton observation of the cluster. This XMM-Newton observation, imaged by three detectors, covers a greater field of view with a longer exposure (48.6 ks) than the previous Chandra observation. We will present images and spectra of various regions of the cluster. In addition, we will discuss the dynamics of the cluster, the nature of the Plume, Shock and other features, and origin of the central diffuse radio halo/relic and SW radio relic. These X-ray observations will also be compared to a numerical simulation from the Simulation Library of Astrophysics cluster Mergers (SLAM).

  5. Analysis of Jovian low frequency radio emissions

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.

    1985-01-01

    The density of ions in the Io plasma torus and the scattering of these ions by low frequency electromagnetic emissions detected by Voyager 1 were studied. The ion density profile was investigated using whistler dispersion measurements provided by the Voyager plasma instrument. The scale height and absolute density of H+ ions in the vicinity of the plasma torus were determined by combining the measured plasma densities with the whistler dispersion measurements. A theoretical analysis of the modes of propagation of low frequency electromagnetic emissions in the torus was undertaken. Polarization reversal effects and rough estimates of the ion diffusion coefficient were utilized. Numerical evaluation of the ion diffusion coefficients in the torus were made using the observed Voyager 1 wave intensities. Results show that the observed wave intensities produce significant ion diffusion effects in the ion torus.

  6. Shocks in nova outflows. II. Synchrotron radio emission

    NASA Astrophysics Data System (ADS)

    Vlasov, Andrey; Vurm, Indrek; Metzger, Brian D.

    2016-08-01

    The discovery of GeV gamma-rays from classical novae indicates that shocks and relativistic particle acceleration are energetically key in these events. Further evidence for shocks comes from thermal keV X-ray emission and an early peak in the radio light curve on a timescale of months with a brightness temperature which is too high to result from freely expanding photo-ionized gas. Paper I developed a one dimensional model for the thermal emission from nova shocks. This work concluded that the shock-powered radio peak cannot be thermal if line cooling operates in the post-shock gas at the rate determined by collisional ionization equilibrium. Here we extend this calculation to include non-thermal synchrotron emission. Applying our model to three classical novae, we constrain the amplification of the magnetic field ɛB and the efficiency ɛe of accelerating relativistic electrons of characteristic Lorentz factor γ ˜ 100. If the shocks are radiative (low velocity v_sh ≲ 1000 km s-1) and cover a large solid angle of the nova outflow, as likely characterize those producing gamma-rays, then values of ɛe ˜ 0.01 - 0.1 are required to achieve the peak radio brightness for ɛB = 10-2. Such high efficiencies exclude secondary pairs from pion decay as the source of the radio-emitting particles, instead favoring the direct acceleration of electrons at the shock. If the radio-emitting shocks are instead adiabatic (high velocity), as likely characterize those responsible for the thermal X-rays, then much higher brightness temperatures are possible, allowing the radio-emitting shocks to cover a smaller outflow solid angle.

  7. Virtual observatory tools and amateur radio observations supporting scientific analysis of Jupiter radio emissions

    NASA Astrophysics Data System (ADS)

    Cecconi, Baptiste; Hess, Sebastien; Le Sidaner, Pierre; Savalle, Renaud; Stéphane, Erard; Coffre, Andrée; Thétas, Emmanuel; André, Nicolas; Génot, Vincent; Thieman, Jim; Typinski, Dave; Sky, Jim; Higgins, Chuck; Imai, Masafumi

    2016-04-01

    In the frame of the preparation of the NASA/JUNO and ESA/JUICE (Jupiter Icy Moon Explorer) missions, and the development of a planetary sciences virtual observatory (VO), we are proposing a new set of tools directed to data providers as well as users, in order to ease data sharing and discovery. We will focus on ground based planetary radio observations (thus mainly Jupiter radio emissions), trying for instance to enhance the temporal coverage of jovian decametric emission. The data service we will be using is EPN-TAP, a planetary science data access protocol developed by Europlanet-VESPA (Virtual European Solar and Planetary Access). This protocol is derived from IVOA (International Virtual Observatory Alliance) standards. The Jupiter Routine Observations from the Nancay Decameter Array are already shared on the planetary science VO using this protocol, as well as data from the Iitate Low Frquency Radio Antenna, in Japan. Amateur radio data from the RadioJOVE project is also available. The attached figure shows data from those three providers. We will first introduce the VO tools and concepts of interest for the planetary radioastronomy community. We will then present the various data formats now used for such data services, as well as their associated metadata. We will finally show various prototypical tools that make use of this shared datasets.

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

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

  9. On Io's control of Jovian decametric radio emissions

    NASA Technical Reports Server (NTRS)

    Winglee, R. M.

    1986-01-01

    Io's control of Jovian decametric radio emission (DAM) has been attributed to Io distorting the electron distribution in the inner Jovian magnetosphere. Observations of Faraday rotation in DAM are used to determine the properties of the electron distribution before and after its interaction with Io. It is shown that there is an enhancement in the density of the energetic component in the Io plasma torus correlated with certain Jovian longitude. Io's interaction with this energetic component can produce heating of this component. The Io-controlled emission is attributed to enhanced emission from the heated electrons moving down the field lines to Jupiter.

  10. Source characteristics of Jovian narrow-band kilometric radio emissions

    NASA Astrophysics Data System (ADS)

    Reiner, M. J.; Fainberg, J.; Stone, R. G.; Kaiser, M. L.; Desch, M. D.; Manning, R.; Zarka, P.; Pedersen, B.-M.

    1993-07-01

    New observations of Jovian narrow-band kilometric (nKOM) radio emissions were made by the Unified Radio and Plasma Wave (URAP) experiment on the Ulysses spacecraft during the Ulysses-Jupiter encounter in early February 1992. These observations have demonstrated the unique capability of the URAP instrument for determining both the direction and polarization of nKOM radio sources. An important result is the discovery that nKOM radio emission originates from a number of distinct sources located at different Jovian longitudes and at the inner and outermost regions of the Io plasma torus. These sources have been tracked for several Jovian rotations, yielding their corotational lags, their spatial and temporal evolution, and their radiation characteristics at both low latitudes far from Jupiter and at high latitudes near the planet. Both right-hand and left-hand circularly polarized nKOM sources were observed. The polarizations observed for sources in the outermost regions of the torus seem to favor extraordinary mode emission.

  11. Zebra spectral structures in Jovian decametric radio emissions

    NASA Astrophysics Data System (ADS)

    Rošker, S.; Panchenko, M.; Rucker, H. O.; Brazhenko, A. I.

    2015-10-01

    Jupiter with the largest planetary magnetosphere in the solar system emits intense coherent non-thermal radiation in a wide frequency range. This emission is a result of complicated interactions between the dynamic Jovian magnetosphere and energetic particles supplying free energy from planetary rotation and the interaction between Jupiter and the Galilean moon Io. Decametric radio emission (DAM) is the strongest component of Jovian radiation observed in a frequency range from a few MHz up to 40 MHz. Depending on the time scales the Jovian DAM exhibits different complex spectral structures. Recent observations of the Jovian decametric radio emission using the large ground-based radio telescope URAN-2 (Poltava, Ukraine) enabled the detection of fine spectral structures, specifically zebra stripe-like patterns, never reported before in the Jovian decametric wavelength regime (Figure 1). In this presentation we describe and analyse these new observations by investigating the characteristics of the Jovian decametric zebra patterns. On basis of these findings the possible mechanism of wave generation is discussed and in particular the value of the determination of local plasma densities within the Jovian magnetosphere by remote radio sensing is emphasized.

  12. Scientists Detect Radio Emission from Rapidly Rotating Cosmic Dust Grains

    NASA Astrophysics Data System (ADS)

    2001-11-01

    Astronomers have made the first tentative observations of a long-speculated, but never before detected, source of natural radio waves in interstellar space. Data from the National Science Foundation's 140 Foot Radio Telescope at the National Radio Astronomy Observatory in Green Bank, W.Va., show the faint, tell-tale signals of what appear to be dust grains spinning billions of times each second. This discovery eventually could yield a powerful new tool for understanding the interstellar medium - the immense clouds of gas and dust that populate interstellar space. The NRAO 140 Foot Radio Telescope The NRAO 140-Foot Radio Telescope "What we believe we have found," said Douglas P. Finkbeiner of Princeton University's Department of Astrophysics, "is the first hard evidence for electric dipole emission from rapidly rotating dust grains. If our studies are confirmed, it will be the first new source of continuum emission to be conclusively identified in the interstellar medium in nearly the past 20 years." Finkbeiner believes that these emissions have the potential in the future of revealing new and exciting information about the interstellar medium; they also may help to refine future studies of the Cosmic Microwave Background Radiation. The results from this study, which took place in spring 1999, were accepted for publication in Astrophysical Journal. Other contributors to this paper include David J. Schlegel, department of astrophysics, Princeton University; Curtis Frank, department of astronomy, University of Maryland; and Carl Heiles, department of astronomy, University of California at Berkeley. "The idea of dust grains emitting radiation by rotating is not new," comments Finkbeiner, "but to date it has been somewhat speculative." Scientists first proposed in 1957 that dust grains could emit radio signals, if they were caused to rotate rapidly enough. It was believed, however, that these radio emissions would be negligibly small - too weak to be of any impact to

  13. Radio emission from magnetic exoplanets: GMRT observations and results

    NASA Astrophysics Data System (ADS)

    Majid, W.; Winterhalter, D.; Kuiper, T.; Lazio, J.

    2011-10-01

    Massive extrasolar planets are expected to emit, in analogy with Jupiter and Saturn, detectable radio emission at low frequencies. We have carried out a series of observations of known extrasolar planetary systems at 150 MHz with the Giant Meterwave Radio Telescope (GMRT) in both interferometric and phased array modes. We will describe our observing campaign, target list, and preliminary results from studies of dynamic spectra. As low frequency observations are plagued with RFI, we will focus on observing strategies and analysis techniques to minimize, identify and remove RFI effects from dynamic spectra. We will also briefly discuss prospects for similar searches with future instruments such as LOFAR, the LWA, and the SKA instruments.

  14. RFID Transponders' Radio Frequency Emissions in Aircraft Communication and Navigation Radio Bands

    NASA Technical Reports Server (NTRS)

    Nguyen, Truong X.; Ely, Jay J.; Williams, Reuben A.; Koppen, Sandra V.; Salud, Maria Theresa P.

    2006-01-01

    Radiated emissions in aircraft communication and navigation bands are measured from several active radio frequency identification (RFID) tags. The individual tags are different in design and operations. They may also operate in different frequency bands. The process for measuring the emissions is discussed, and includes tag interrogation, reverberation chamber testing, and instrument settings selection. The measurement results are described and compared against aircraft emission limits. In addition, interference path loss for the cargo bays of passenger aircraft is measured. Cargo bay path loss is more appropriate for RFID tags than passenger cabin path loss. The path loss data are reported for several aircraft radio systems on a Boeing 747 and an Airbus A320.

  15. Amalthea's modulation of Jovian decametric radio emission

    NASA Astrophysics Data System (ADS)

    Arkhypov, O. V.; Rucker, H. O.

    2007-05-01

    Most modulation lanes in dynamic spectra of Jovian decametric emission (DAM) are formed by radiation scattering on field-aligned inhomogeneities in the Io plasma torus. The positions and frequency drift of hundreds of lanes have been measured on the DAM spectra from UFRO archives. A special 3D algorithm is used for localization of field-aligned magnetospheric inhomogeneities by the frequency drift of modulation lanes. It is found that some lanes are formed near the magnetic shell of the satellite Amalthea mainly at longitudes of 123°≤λ_III≤140° (north) and 284°≤λ_III≤305° (south). These disturbances coincide with regions of plasma compression by the rotating magnetic field of Jupiter. Such modulations are found at other longitudes too (189° to 236°) with higher sensitivity. Amalthea's plasma torus could be another argument for the ice nature of the satellite, which has a density less than that of water.

  16. Amalthea's modulation of Jovian decametric radio emission

    NASA Astrophysics Data System (ADS)

    Arkhypov, O. V.; Rucker, H. O.

    2007-08-01

    Most modulation lanes in dynamic spectra of Jovian decametric emission (DAM) are formed by radiation scattering on field-aligned inhomogeneities in the Io plasma torus. The positions and frequency drift of hundreds of lanes have been measured on the DAM spectra from UFRO archives. A special 3D algorithm is used for localization of field-aligned magnetospheric inhomogeneities by the frequency drift of modulation lanes. It is found that some lanes are formed near the magnetic shell of the satellite Amalthea mainly at longitudes of 123 to 140 deg. (north; III 1965 system) and 284 to 305 deg. (south). These disturbances coincide with regions of plasma compression by the rotating magnetic field of Jupiter. Such modulations are found at other longitudes too (189 to 236 deg.) with higher sensitivity. Amalthea's plasma torus could be another argument for the ice nature of the satellite, which has a density less than that of water.

  17. ELECTRON-BEAM-INDUCED RADIO EMISSION FROM ULTRACOOL DWARFS

    SciTech Connect

    Yu, S.; Doyle, J. G.; Kuznetsov, A.; Hallinan, G.; Antonova, A.; MacKinnon, A. L.; Golden, A.

    2012-06-10

    We present the numerical simulations for an electron-beam-driven and loss-cone-driven electron-cyclotron maser (ECM) with different plasma parameters and different magnetic field strengths for a relatively small region and short timescale in an attempt to interpret the recent discovered intense radio emission from ultracool dwarfs. We find that a large amount of electromagnetic (EM) field energy can be effectively released from the beam-driven ECM, which rapidly heats the surrounding plasma. A rapidly developed high-energy tail of electrons in velocity space (resulting from the heating process of the ECM) may produce the radio continuum depending on the initial strength of the external magnetic field and the electron beam current. Both significant linear polarization and circular polarization of EM waves can be obtained from the simulations. The spectral energy distributions of the simulated radio waves show that harmonics may appear from 10 to 70{nu}{sub pe} ({nu}{sub pe} is the electron plasma frequency) in the non-relativistic case and from 10 to 600{nu}{sub pe} in the relativistic case, which makes it difficult to find the fundamental cyclotron frequency in the observed radio frequencies. A wide frequency band should therefore be covered by future radio observations.

  18. Unknown radio emission at about 3 MHz recorded in Norway

    NASA Astrophysics Data System (ADS)

    Farges, T.; Blanc, E.; Strand, E.

    2012-04-01

    A wideband electric field antenna has been installed in Norway (at Hessdalen, 62°41' North and 11°12' East). A signal of 50 ms is automatically recorded every 5 s in order to monitor the spectral variations from 1 kHz to 5 MHz. Signals have been acquired during more than one year from September 2010 to December 2011. The measured electromagnetic spectrum is very similar to other spectra commonly measured in other places in the World. It shows emissions in numerous bands at fixed frequencies corresponding to radio transmissions in VLF, LF, MF and HF bands. However, one emission is quite different and arouses our curiosity. We find a quasi-continuous radio emission at a frequency varying from 2.7 to more than 3.4 MHz with a mean value of 3.0 MHz. The bandwidth is quite large (about 40 kHz) while it is about 9 kHz for all the other radio emissions at frequencies higher than 100 kHz. During the night, the frequency is relatively stable at about 3.1 MHz while during day-time a frequency shift of 200-300 kHz is often observed. These variations can be quick (few tens of minutes) or slow (several hours). Moreover, the emission disappears during day-time, the disappearance duration depending on the daylight duration. From November to the end of March, there is almost no disappearance while in April disappearances are more frequent and longer. From May to July, the emission disappears systematically during day-time from 6:00 UT to 20:00 UT. At the sunrise time the emission frequency suddenly decreases and systematically disappears when it reaches a threshold value (from 2.7 to 2.85 MHz). The emission (frequency and duration) is not influenced by the magnetic storms. We will show in the paper statistical results and some hypothesis on the mechanism which can produce this radio emission.

  19. Physical Analysis of the Jovian Synchrotron Radio Emission

    NASA Astrophysics Data System (ADS)

    Santos-Costa, D.; Bolton, S. J.; Levin, S. M.; Thorne, R. M.

    2006-12-01

    We present results of our recent investigation of the Jovian synchrotron emission based on a particle transport code. The features of the two-dimensional brightness distributions, radio spectra and beaming curves are correlated to the different phenomena driven the dynamics of the electron radiation belts. The adiabatic invariant theory was used for performing this analysis work. The theoretical approach first enabled us to describe the electron radiation belts by modeling the interactions between high-energy trapped particles and plasmas, neutrals, moons, dust and magnetic field. Then radio observations were used to discuss the computed particle distributions in the inner magnetosphere of Jupiter. The simulated brightness mappings were compared with VLA observations made at two wavelengths (20 and 6 cm). The beaming curve comparisons at 13-cm wavelength were performed for different epochs in order to evaluate the dependence of the model to the geometric factor De. The computed radio spectra were discussed with measurements made in the [0.5-20] GHz radio band. The simulation results match the different remote observations very well and thus allowed us to study the phenomenology of the Jovian synchrotron radio emission. The analysis of the Jovian synchrotron emission demonstrates that during the inward particle transport, local losses associated with the Jovian moons set the extension and intensity of the synchrotron radiation along the magnetic equator. Close to the planet, trapped electrons suffer from the interactions with dust and magnetic field, resulting in the transport of particles toward the high latitudes. The quantity of particles transported away from the equator is sufficient to produce the measurable secondary radio emissions. The simulations show that the moon sweeping effect controls both the transport toward the planet and at high latitudes by reducing the abundance of particles constrained to populate the regions out of the equator. Among the

  20. Virtual Observatory tools and Amateur Radio Observations Supporting Scientific Analysis of Jupiter Radio Emissions

    NASA Astrophysics Data System (ADS)

    Cecconi, B.; Hess, S. L. G.; Le Sidaner, P.; Savalle, R.; Erard, S.; Coffre, A.; Thétas, E.; André, N.; Génot, V.; Thieman, J.; Typinski, D.; Sky, J.; Higgins, C.

    2015-10-01

    In the frame of the preparation of the NASA/JUNO and ESA/JUICE (Jupiter Icy Moon Explorer) missions, and the development of a planetary sciences virtual observatory (VO), we are proposing a new set of tools directed to data providers as well as users, in order to ease data sharing and discovery. We will focus on ground based planetary radio observations (thus mainly Jupiter radio emissions), trying for instance to enhance the temporal coverage of jovian decametric emission. The data service we will be using is EPN-TAP, a planetary science data access protocol developed by Europlanet-VESPA (Virtual European Solar and Planetary Access). This protocol is derived from IVOA (International Virtual Observatory Alliance) standards. The Jupiter Routine Observations from the Nancay Decameter Array are already shared on the planetary science VO using this protocol. Amateur radio data from the RadioJOVE project is also available. We will first introduce the VO tools and concepts of interest for the planetary radioastronomy community. We will then present the various data formats now used for such data services, as well as their associated metadata. We will finally show various prototypical tools that make use of this shared datasets. A preliminary study based on January-February 2014 data will also be presented

  1. Escaping radio emission from pulsars: Possible role of velocity shear

    SciTech Connect

    Mahajan, S.M. |; Machabeli, G.Z.; Rogava, A.D. |

    1997-01-01

    It is demonstrated that the velocity shear, intrinsic to the e{sup +}e{sup {minus}} plasma present in the pulsar magnetosphere, can efficiently convert the nonescaping longitudinal Langmuir waves (produced by some kind of a beam or stream instability) into propagating (escaping) electromagnetic waves. It is suggested that this shear induced transformation may be the basic mechanism needed for the eventual generation of the observed pulsar radio emission.

  2. Jovian longitudinal control of Io-related radio emissions

    NASA Technical Reports Server (NTRS)

    Dessler, A. J.; Hill, T. W.

    1979-01-01

    A theoretical model is proposed to explain the control of Io-related radio emissions by Jupiter's rotational phase. The model is based on the hypothesis that the radio emissions are generated by Birkeland currents flowing between Io and the Jovian ionosphere. Specifically, it is suggested that the precipitation of radiation-belt electrons within a certain range of Jovian longitudes produces a restricted region of enhanced ionization and correspondingly enhanced conductivity in Jupiter's ionosphere and that the Io-Jupiter Birkeland current and the associated radio emissions are dramatically increased when Io's flux tube encounters this sector of enhanced ionization in Jupiter's ionosphere. The magnitude of the current is found to be about 100,000 A at most Jovian longitudes because of ionospheric resistance. It is estimated that within the favored longitudinal sector electron precipitation produces an enhancement of this current by one to three orders of magnitude. The model predictions are compared with observations made during the Pioneer 10 and 11 flybys, and satisfactory agreement is obtained.

  3. Detection of 610-MHz radio emission from hot magnetic stars

    NASA Astrophysics Data System (ADS)

    Chandra, P.; Wade, G. A.; Sundqvist, J. O.; Oberoi, D.; Grunhut, J. H.; ud-Doula, A.; Petit, V.; Cohen, D. H.; Oksala, M. E.; David-Uraz, A.

    2015-09-01

    We have carried out a study of radio emission from a small sample of magnetic O- and B-type stars using the Giant Metrewave Radio Telescope, with the goal of investigating their magnetospheres at low frequencies. These are the lowest frequency radio measurements ever obtained of hot magnetic stars. The observations were taken at random rotational phases in the 1390 and the 610 MHz bands. Out of the eight stars, we detect five B-type stars in both the 1390 and the 610 MHz bands. The three O-type stars were observed only in the 1390 MHz band, and no detections were obtained. We explain this result as a consequence of free-free absorption by the free-flowing stellar wind exterior to the confined magnetosphere. We also study the variability of individual stars. One star - HD 133880 - exhibits remarkably strong and rapid variability of its low-frequency flux density. We discuss the possibility of this emission being coherent emission as reported for CU Vir by Trigilio et al.

  4. Radio emission from the magnetic equator of Uranus

    NASA Technical Reports Server (NTRS)

    Kaiser, M. L.; Desch, M. D.; Connerney, J. E. P.

    1989-01-01

    The major observational characteristics of the smooth, narrow bandwidth component of Uranus' radio emissions are well described by sources radiating near the local electron gyrofrequency, confined to the magnetic equatorial plane and encircling the planet at radial distances of approximately 2 to 3 R(U). The most intense emission appears to be generated in association with the epsilon ring at 2.0 R(U) radial distance. A cold electron density of less than or equal to 4/cu cm are inferred in this region.

  5. Radio emission from the magnetic equator of Uranus

    SciTech Connect

    Kaiser, M.L.; Desch, M.D.; Connerney, J.E.P. )

    1989-03-01

    The major observational characteristics of the smooth, narrow bandwidth component of Uranus' radio emissions are well described by sources radiating near the local electron gyrofrequency, confined to the magnetic equatorial plane and encircling the plant at radial distances of approximately 2 to 3 R{sub v}. The most intense emission appears to be generated in association with the {var epsilon} ring at 2.0 R{sub v} radial distance. The authors infer a cold electron density of {le} 4 cm{sup {minus}3} in this region.

  6. Natural radio emission of Jupiter as interferences for radar investigations of the icy satellites of Jupiter

    NASA Astrophysics Data System (ADS)

    Cecconi, B.; Hess, S.; Hérique, A.; Santovito, M. R.; Santos-Costa, D.; Zarka, P.; Alberti, G.; Blankenship, D.; Bougeret, J. L.; Bruzzone, L.; Kofman, W.

    2011-10-01

    Radar instruments are part of the core payload of the two Europa Jupiter System Mission (EJSM) spacecraft: NASA-led Jupiter Europa Orbiter (JEO) and ESA-led Jupiter Ganymede Orbiter (JGO). At this point of the project, several frequency bands are under study for radar, which ranges between 5MHz and 50MHz. Part of this frequency range overlaps with that of the natural Jovian radio emissions, which are very intense in the decametric range, below 40 MHz. Radio observations above 40 MHz are free of interferences, whereas below this threshold, careful observation strategies have to be investigated. We present a review of spectral intensity, variability and sources of these radio emissions. As the radio emission are strongly beamed, it is possible to model the visibility of the radio emissions, as seen from the vicinity of Europa or Ganymede. We have investigated Io-related radio emissions as well as radio emissions related to the auroral oval. We also review the radiation belts synchrotron emission characteristics. We present radio sources visibility products (dynamic spectra and radio source location maps, on still frames or movies), which can be used for operation planning. This study clearly shows that a deep understanding of the natural radio emissions at Jupiter is necessary to prepare the future EJSM radar instrumentation. We show that this radio noise has to be taken into account very early in the observation planning and strategies for both JGO and JEO. We also point out possible synergies with RPW (Radio and Plasma Waves) instrumentations.

  7. Natural radio emission of Jupiter as interferences for radar investigations of the icy satellites of Jupiter

    NASA Astrophysics Data System (ADS)

    Cecconi, B.; Hess, S.; Hérique, A.; Santovito, M. R.; Santos-Costa, D.; Zarka, P.; Alberti, G.; Blankenship, D.; Bougeret, J.-L.; Bruzzone, L.; Kofman, W.

    2012-02-01

    Radar instruments are part of the core payload of the two Europa Jupiter System Mission (EJSM) spacecraft: NASA-led Jupiter Europa Orbiter (JEO) and ESA-led Jupiter Ganymede Orbiter (JGO). At this point of the project, several frequency bands are under study for radar, which ranges between 5 and 50 MHz. Part of this frequency range overlaps with that of the natural jovian radio emissions, which are very intense in the decametric range, below 40 MHz. Radio observations above 40 MHz are free of interferences, whereas below this threshold, careful observation strategies have to be investigated. We present a review of spectral intensity, variability and sources of these radio emissions. As the radio emissions are strongly beamed, it is possible to model the visibility of the radio emissions, as seen from the vicinity of Europa or Ganymede. We have investigated Io-related radio emissions as well as radio emissions related to the auroral oval. We also review the radiation belts synchrotron emission characteristics. We present radio sources visibility products (dynamic spectra and radio source location maps, on still frames or movies), which can be used for operation planning. This study clearly shows that a deep understanding of the natural radio emissions at Jupiter is necessary to prepare the future EJSM radar instrumentation. We show that this radio noise has to be taken into account very early in the observation planning and strategies for both JGO and JEO. We also point out possible synergies with RPW (Radio and Plasma Waves) instrumentations.

  8. Radio emission from the nova-like variable AC Cancri and the symbiotic variable AG Draconis

    SciTech Connect

    Torbett, M.V.; Campbell, B.

    1987-07-01

    Radio emission at 6 cm has been detected from the nova-like cataclysmic variable AC Cnc and the symbiotic variable AG Dra. The AC Cnc observation constitutes the first radio detection in this class of objects. The AG Dra source is probably resolved and appears to show asymmetric, extended structure. The radio emission can best be explained by thermal bremsstrahlung. 26 references.

  9. RELATIVISTIC MODEL ON PULSAR RADIO EMISSION AND POLARIZATION

    SciTech Connect

    Kumar, D.; Gangadhara, R. T. E-mail: ganga@iiap.res.in

    2012-02-20

    We have developed a relativistic model for pulsar radio emission and polarization by taking into account a detailed geometry of emission region, rotation, and modulation. The sparks activity on the polar cap leads to plasma columns in the emission region and modulated emission. By considering relativistic plasma bunches streaming out along the rotating dipolar field lines as a source of curvature radiation, we have deduced the polarization state of the radiation field in terms of the Stokes parameters. We have simulated a set of typical pulse profiles and analyzed the role of viewing geometry, rotation, and modulation in the pulsar polarization profiles. Our simulations explain most of the diverse behaviors of polarization generally found in pulsar radio profiles. We show that both the 'antisymmetric' and 'symmetric' types of circular polarization are possible within the framework of curvature radiation. We also show that the 'kinky' nature in the polarization position angle traverses might be due to the rotation and modulation effects. The phase lag of the polarization position angle inflection point relative to the phase of core peak depends upon the rotationally induced asymmetry in the curvature of source trajectory and modulation.

  10. Radio Emission from Red-giant Hot Jupiters

    NASA Astrophysics Data System (ADS)

    Fujii, Yuka; Spiegel, David S.; Mroczkowski, Tony; Nordhaus, Jason; Zimmerman, Neil T.; Parsons, Aaron R.; Mirbabayi, Mehrdad; Madhusudhan, Nikku

    2016-04-01

    When planet-hosting stars evolve off the main sequence and go through the red-giant branch, the stars become orders of magnitudes more luminous and, at the same time, lose mass at much higher rates than their main-sequence counterparts. Accordingly, if planetary companions exist around these stars at orbital distances of a few au, they will be heated up to the level of canonical hot Jupiters and also be subjected to a dense stellar wind. Given that magnetized planets interacting with stellar winds emit radio waves, such “Red-Giant Hot Jupiters” (RGHJs) may also be candidate radio emitters. We estimate the spectral auroral radio intensity of RGHJs based on the empirical relation with the stellar wind as well as a proposed scaling for planetary magnetic fields. RGHJs might be intrinsically as bright as or brighter than canonical hot Jupiters and about 100 times brighter than equivalent objects around main-sequence stars. We examine the capabilities of low-frequency radio observatories to detect this emission and find that the signal from an RGHJ may be detectable at distances up to a few hundred parsecs with the Square Kilometer Array.

  11. Radio Emission from Red-Giant Hot Jupiters

    NASA Technical Reports Server (NTRS)

    Fujii, Yuka; Spiegel, David S.; Mroczkowski, Tony; Nordhaus, Jason; Zimmerman, Neil T.; Parsons, Aaron R.; Mirbabayi, Mehrdad; Madhusudhan, Nikku

    2016-01-01

    When planet-hosting stars evolve off the main sequence and go through the red-giant branch, the stars become orders of magnitudes more luminous and, at the same time, lose mass at much higher rates than their main sequence counterparts. Accordingly, if planetary companions exist around these stars at orbital distances of a few au, they will be heated up to the level of canonical hot Jupiters and also be subjected to a dense stellar wind. Given that magnetized planets interacting with stellar winds emit radio waves, such "Red-Giant Hot Jupiters" (RGHJs) may also be candidate radio emitters. We estimate the spectral auroral radio intensity of RGHJs based on the empirical relation with the stellar wind as well as a proposed scaling for planetary magnetic fields. RGHJs might be intrinsically as bright as or brighter than canonical hot Jupiters and about 100 times brighter than equivalent objects around main-sequence stars. We examine the capabilities of low-frequency radio observatories to detect this emission and find that the signal from an RGHJ may be detectable at distances up to a few hundred parsecs with the Square Kilometer Array.

  12. Predicting Changes in the Radio Emission Fluxes of Extragalactic Sources

    NASA Astrophysics Data System (ADS)

    Sukharev, A. L.; Ryabov, M. I.; Donskikh, G. I.

    2016-06-01

    Data from long-term monitoring with the 26-m University of Michigan radio telescope at a frequency of 14.5 GHz (1974-2011) is used to predict changes in the radio emission fluxes from the extragalactic sources 3C273, 3C120, 3C345, 3C446, 3C454.3, OJ287, OT081, and BLLac. The predictions are based on data on the major periods of variability and their durations obtained by wavelet analysis. The radio emission fluxes from the sources 3C345, 3C446, and 3C454.3, which have complicated variabilities, are predicted using an autoregression linear prediction method. This yields a forecast of the flux variations extending up to 5 years. Harmonic prediction is used for another group of sources, BLLac, OJ287, and OT081, with rapid variability. This approach yielded forecasts extending 4-9 years. For the sources 3C273 and 3C120, which have stable long periods, the harmonic method was also used and yielded a forecast extending up to 16 years. The reliability of the prediction was confirmed by independent observational data from the MOJAVE program for 2011-2015.

  13. Saturn radio emission and the solar wind - Voyager-2 studies

    SciTech Connect

    Desch, M.D.; Rucker, H.O.

    1985-01-01

    Voyager 2 data from the Plasma Science experiment, the Magnetometer experiment and the Planetary Radio Astronomy experiment were used to analyze the relationship between parameters of the solar wind/interplanetary medium and the nonthermal Saturn radiation. Solar wind and interplanetary magnetic field properties were combined to form quantities known to be important in controlling terrestrial magnetospheric processes. The Voyager 2 data set used in this investigation consists of 237 days of Saturn preencounter measurements. However, due to the immersion of Saturn and the Voyager 2 spacecraft into the extended Jupiter magnetic tail, substantial periods of the time series were lacking solar wind data. To cope with this problem a superposed epoch method (CHREE analysis) was used. The results indicate the superiority of the quantities containing the solar wind density in stimulating the radio emission of Saturn - a result found earlier using Voyager 1 data - and the minor importance of quantities incorporating the interplanetary magnetic field. 10 references.

  14. Cloud-to-stratosphere lightning discharges - A radio emission model

    NASA Technical Reports Server (NTRS)

    Farrell, W. M.; Desch, M. D.

    1992-01-01

    Recent observations of rare cloud-to-stratospheric lightning discharges suggest the events are inherently 'slow-rising', with the emitted energy reaching peak values in about 10 milliseconds. Applying a dipole radiation model, it is demonstrated that the emitted radio wave energy from such slow-rising events is strongest below about 50 Hz, and possesses a significant rolloff at higher frequencies. In the analysis, various current distributions are considered in order to determine the effect on the radio spectrum. Near 10 kHz, the emission from cloud-to-stratospheric lightning is significantly reduced as compared to the typical cloud-to-ground return stroke, with amplitudes as much as 50 dB lower. This result may explain the lack of detection of VLF signals from recently observed long-lasting discharge events.

  15. Saturn radio emission and the solar wind - Voyager-2 studies

    NASA Technical Reports Server (NTRS)

    Desch, M. D.; Rucker, H. O.

    1985-01-01

    Voyager 2 data from the Plasma Science experiment, the Magnetometer experiment and the Planetary Radio Astronomy experiment were used to analyze the relationship between parameters of the solar wind/interplanetary medium and the nonthermal Saturn radiation. Solar wind and interplanetary magnetic field properties were combined to form quantities known to be important in controlling terrestrial magnetospheric processes. The Voyager 2 data set used in this investigation consists of 237 days of Saturn preencounter measurements. However, due to the immersion of Saturn and the Voyager 2 spacecraft into the extended Jupiter magnetic tail, substantial periods of the time series were lacking solar wind data. To cope with this problem a superposed epoch method (CHREE analysis) was used. The results indicate the superiority of the quantities containing the solar wind density in stimulating the radio emission of Saturn - a result found earlier using Voyager 1 data - and the minor importance of quantities incorporating the interplanetary magnetic field.

  16. Chromospheric evaporation and decimetric radio emission in solar flares

    NASA Technical Reports Server (NTRS)

    Aschwanden, Markus J.; Benz, Arnold O.

    1995-01-01

    We have discovered decimetric signatures of the chromospheric evaporation process. Evidence for the radio detection of chromospheric evaporation is based on the radio-inferred values of (1) the electron density, (2) the propagation speed, and (3) the timing, which are found to be in good agreement with statistical values inferred from the blueshifted Ca XIX soft X-ray line. The physical basis of our model is that free-free absorption of plasma emission is strongly modified by the steep density gradient and the large temperature increase in the upflowing flare plasma. The steplike density increase at the chromospheric evaporation front causes a local discontinuity in the plasma frequency, manifested as almost infinite drift rate in decimetric type III bursts. The large temperature increase of the upflowing plasma considerably reduces the local free-free opacity (due to the T(exp -3/2) dependence) and thus enhances the brightness of radio bursts emitted at the local plasma frequency near the chromospheric evaporation front, while a high-frequency cutoff is expected in the high-density regions behind the front, which can be used to infer the velocity of the upflowing plasma. From model calculations we find strong evidence that decimetric bursts with a slowly drifting high-frequency cutoff are produced by fundamental plasma emission, contrary to the widespread belief that decimetric bursts are preferentially emitted at the harmonic plasma level. We analyze 21 flare episodes from 1991-1993 for which broadband (100-3000 MHz) radio dynamic spectra from Pheonix, hard X-ray data from (BATSE/CGRO) and soft X-ray data from Burst and Transient Source Experiment/Compton Gamma Ray Observatory (GOES) were available.

  17. Radio emission from dusty galaxies observed by AKARI

    NASA Astrophysics Data System (ADS)

    Pepiak, A.; Pollo, A.; Takeuchi, T. T.; Solarz, A.; Jurusik, W.

    2014-10-01

    We probe radio-infrared correlation for two samples of extragalactic sources from the local Universe from the AKARI All-Sky Catalogue. The first, smaller sample (1053 objects) was constructed by the cross-correlation of the AKARI/FIS All-Sky Survey Bright Source Catalogue, the AKARI IRC All-Sky Survey Point Source Catalogue and the NRAO VLA Sky Survey, i.e. it consists of sources detected in the mid- and far-infrared by AKARI, and at the 1.4 GHz radio frequency by NRAO. The second, larger sample (13,324 objects) was constructed by the cross-correlation of only the AKARI/FIS All-Sky Survey Bright Source Catalogue and the NRAO VLA Sky Survey, i.e. it consists of sources detected in the far-infrared and radio, without a condition to be detected in the mid-infrared. Additionally, all objects in both samples were identified as galaxies in the NED and/or SIMBAD databases, and a part of them is known to host active galactic nuclei (AGNs). For the present analysis, we have restricted our samples only to sources with known redshift z. In this paper, we analyse the far-infrared-radio correlation for both of these samples. We compare the ratio of infrared and radio emission from normal star-forming dusty galaxies and AGNs in both samples. For the smaller sample we obtained =2.14 for AGNs and =2.27 for normal galaxies, while for the larger sample =2.15 for AGNs and =2.22 for normal galaxies. An average value of the slope in both samples is ~2.2, which is consistent with the previous measurements from the literature.

  18. Confirmation of Pulsed Radio Emission from the Pulsar J1907+0919 (Shitov Radio Pulsar, SGR 1900+14)

    NASA Astrophysics Data System (ADS)

    Glushak, A. P.; Losovsky, B. Ya.; Dumsky, D. V.

    2015-10-01

    Observations at a frequency of 111 MHz with the Large Phased Array at the Pushchino Radio Astronomy Observatory of the Astro Space Center of the P.N. Lebedev Physical Institute confirm the pulsed radio emission of the X-ray pulsar J1907+0919 that is a counterpart of the magnetar SGR 1900+14. Its pulsed radio emission was discovered earlier by Shitov (1999). A flux density periodogram is built. A new spin period P = 5.22756(42) s and flux density 50± 5~mJy are measured at the Epoch 56834.6 MJD. A value of the pulsar radio emission spectral index is estimated as < -4.3. This radio spectrum is one of the steepest among the spectra of known pulsars.

  19. DARK MATTER AND SYNCHROTRON EMISSION FROM GALACTIC CENTER RADIO FILAMENTS

    SciTech Connect

    Linden, Tim; Hooper, Dan; Yusef-Zadeh, Farhad

    2011-11-10

    The inner degrees of the Galactic center contain a large population of filamentary structures observed at radio frequencies. These so-called non-thermal radio filaments (NRFs) trace magnetic field lines and have attracted significant interest due to their hard (S{sub v} {proportional_to}{nu}{sup -0.1{+-}0.4}) synchrotron emission spectra. The origin of these filaments remains poorly understood. We show that the electrons and positrons created through the annihilations of a relatively light ({approx}5-10 GeV) dark matter particle with the cross section predicted for a simple thermal relic can provide a compelling match to the intensity, spectral shape, and flux variation of the NRFs. Furthermore, the characteristics of the dark matter particle necessary to explain the synchrotron emission from the NRFs are consistent with those required to explain the excess {gamma}-ray emission observed from the Galactic center by the Fermi Large Area Telescope, as well as the direct detection signals observed by CoGeNT and DAMA/LIBRA.

  20. Possible radio emission from Uranus at 0.5 MHz

    NASA Technical Reports Server (NTRS)

    Brown, L. W.

    1976-01-01

    Radio emission from the direction of Uranus has been detected in data from the Goddard radio astronomy experiment on the IMP-6 spacecraft. Previously, emission from the direction of Jupiter and Saturn had been observed by IMP-6 at a number of frequencies near 1 MHz and were identified through an analysis of the phase of the observed modulated signal detected from the spinning dipole antenna. This technique was applied to the direction of Uranus with possible positive results. Over the approximately 500 days of data, three to six bursts with unique spectral characteristics have been found. The events persisted less than 3 minutes and are strongest in intensity near 0.5 MHz. Identification with Uranus is confused by the likely presence of low-level terrestrial and solar emission. Because of the unfavorable angular separation of earth and Uranus, there is a possibility that the bursts are atypical terrestrial magnetospheric phenomena, although the uniqueness of the set of events indicates the probable detection of radiation from Uranus.

  1. Dark Matter and Synchrotron Emission from Galactic Center Radio Filaments

    SciTech Connect

    Linden, Tim; Hooper, Dan; Yusef-Zadeh, Farhad

    2011-11-10

    The inner degrees of the Galactic center contain a large population of filamentary structures observed at radio frequencies. These so-called non-thermal radio filaments (NRFs) trace magnetic field lines and have attracted significant interest due to their hard (S_v ~ -0.1 +/- 0.4) synchrotron emission spectra. The origin of these filaments remains poorly understood. We show that the electrons and positrons created through the annihilations of a relatively light (~5-10 GeV) dark matter particle with the cross section predicted for a simple thermal relic can provide a compelling match to the intensity, spectral shape, and flux variation of the NRFs. Furthermore, the characteristics of the dark matter particle necessary to explain the synchrotron emission from the NRFs is consistent with those required to explain the excess gamma-ray emission observed from the Galactic center by the Fermi-LAT, as well as the direct detection signals observed by CoGeNT and DAMA/LIBRA.

  2. 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.

  3. Kinetic Simulations of Solar Type II Radio Burst Emission Processes

    SciTech Connect

    Ganse, Urs; Burkart, Thomas; Spanier, Felix; Vainio, Rami

    2010-03-25

    Using our kinetic Particle-in-Cell simulation code, we have examined the behavior of different plasma modes in the environment close to a CME shock front, with special focus on the modes that may contribute to the formation of type II radio bursts. Apart from electron velocity spectra, numerical dispersion plots obtained from simulation data allow for analysis of wave modes in the simulated plasma, especially showing growth and damping of these modes over time. These plots reveal features at 2omega{sub p} which are not predicted by linear wave theory, that may be results of nonlinear three wave interaction processes as theoretically predicted for type II emission processes.

  4. Pulsed Radio Emission from PSR J1119-6127 disappeared

    NASA Astrophysics Data System (ADS)

    Burgay, M.; Possenti, A.; Kerr, M.; Esposito, P.; Rea, N.; Zelati, F. Coti; Israel, G. L.; Johnston, S.

    2016-07-01

    We have searched for pulsed radio emission from the direction of the known high magnetic field pulsar PSR J1119-6127 (spin period of 409 ms, magnetic field intensity at surface of about 4 x 10^13 G, spin-down age of about 1700 yr, embedded in the supernova remnant SNR G292.2-0.5), which showed bursts similar to those typical of the Soft Gamma Repeaters (SGR) at 13:02:07.91 UT on 27 July 2016 (Younes et al,GCN Circular #19735) and at 01:27:51 UT on 28 July 2016 (Kennea et al,Atel #9274).

  5. Diffuse radio emission from clusters in the MareNostrum Universe simulation

    NASA Astrophysics Data System (ADS)

    Hoeft, M.; Brüggen, M.; Yepes, G.; Gottlöber, S.; Schwope, A.

    2008-12-01

    Large-scale diffuse radio emission is observed in some clusters of galaxies. There is ample of evidence that the emission has its origin in synchrotron losses of relativistic electrons that have been accelerated in cluster mergers. In a cosmological simulation, we estimate the radio emission of structure formation shocks as follows: introducing a novel approach to identify strong shock fronts in an smoothed particle hydrodynamics (SPH) simulation, we determine the Mach number as well as the downstream density and temperature in the MareNostrum Universe simulation which has 2 × 10243 particles in a 500h-1Mpc box. Then, we estimate the radio emission using the formalism derived in Hoeft & Brüggen to produce artificial radio maps of massive clusters and to derive a luminosity function of diffuse radio sources. Several of our clusters show radio objects with similar morphology to observed large-scale radio relics, whereas about half of the clusters show only very little radio emission. In agreement with observational findings, the maximum diffuse radio emission of our clusters depends strongly on their X-ray temperature. We find that the so-called accretion shocks cause only very little radio emission. We conclude that a moderate efficiency of shock acceleration, namely ξe = 0.005, and moderate magnetic fields in the region of the relics, namely 0.07-0.8μG are sufficient to reproduce the number density and luminosity of radio relics.

  6. Correlation of pulsar radio emission spectrum with peculiarities of particle acceleration in a polar gap

    SciTech Connect

    Kontorovich, V. M. Flanchik, A. B.

    2013-01-15

    The analytical expression for the frequency of radio emission intensity maximum in pulsars with free electron emission from the stellar surface has been found. Peculiarities of the electron acceleration in a polar gap are considered. The correlation between the high-frequency cutoff and low-frequency turnover in the radio emission spectrum of pulsars known from observations has been explained.

  7. Chromospheric Evaporation and Decimetric Radio Emission in Solar Flares

    NASA Technical Reports Server (NTRS)

    Aschwanden, Markus J.; Benz, Arnold O.

    1995-01-01

    We have discovered decimetric signatures of the chromospheric evaporation process. Evidence for the radio detection of chromospheric evaporation is based on the radio-inferred values of (1) the electron density, (2) the propagation speed, and (3) the timing, which are found to be in good agreement with statistical values inferred from the blueshifted Ca xix soft X-ray line. The physical basis of our model is that free-free absorption of plasma emission is strongly modified by the steep density gradient and the large temperature increase in the upflowing flare plasma. The steplike density increase at the chromospheric evaporation front causes a local discontinuity in the plasma frequency, manifested as almost infinite drift rate in decimetric type III bursts. The large temperature increase of the upflowing plasma considerably reduces the local free-free opacity (due to the T-(exp -3/2) dependence) and thus enhances the brightness of radio bursts emitted at the local plasma frequency near the chromospheric evaporation front, while a high-frequency cutoff is expected in the high-density regions behind the front, which can be used to infer the velocity of the upflowing plasma. From model calculations we find strong evidence that decimetric bursts with a slowly drifting high-frequency cutoff are produced by fundamental plasma emission, contrary to the widespread belief that decimetric bursts are preferentially emitted at the harmonic plasma level. We analyzed 21 flare episodes from 1991-1993 for which broadband (100-3000 MHz) radio dynamic spectra from Phoenix, hard X-ray data from BATSE/CGRO, and soft X-ray data from GOES were available. We detected slowly drifting high-frequency cutoffs between 1.1 and 3.0 GHz, with drift rates of -41 +/- 32 MHz/s, extending over time intervals of 24 +/- 23 s. Developing a density model for type III-emitting flare loops based on the statistically observed drift rate of type III bursts by Alvarez & Haddock, we infer velocities of up to

  8. Tracking the CME-driven shock wave on 2012 March 5 and radio triangulation of associated radio emission

    SciTech Connect

    Magdalenić, J.; Marqué, C.; Mierla, M.; Zhukov, A. N.; Rodriguez, L.; Krupar, V.; Maksimović, M.; Cecconi, B.

    2014-08-20

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

  9. Radio continuum and far-infrared emission of spiral galaxies: Implications of correlations

    NASA Technical Reports Server (NTRS)

    Rengarajan, T. N.; Iyengar, K. V. K.

    1990-01-01

    Researchers present a study extending the correlation seen between radio continuum and far-infrared emissions from spiral galaxies to a lower frequency of 408 MHz and also as a function of radio spectral index. The tight correlation seen between the two luminosities is then used to constrain several parameters governing the emissions such as the changes in star formation rate and mass function, frequency of supernovae that are parents of the interstellar electrons and factors governing synchrotron radio emission.

  10. Optical emission study of radio-frequency excited toluene plasma.

    PubMed

    Lee, Szetsen; Liu, Shiao-Jun; Liang, Rui-Ji

    2008-12-25

    UV-visible emission spectra of radio-frequency (rf) excited toluene plasma were studied. Benzyl radicals as well as toluene monomer and excimer were observed in toluene plasma. It was found that the intensities, peak positions, and linewidths of monomer and excimer emission bands exhibit strong dependence on rf power and plasma processing time. This can be ascribed to photochemical reactions in plasma. Gas-chromatographic analysis of the deposition products from toluene plasma indicated that the main component was bibenzyl. Spectroscopic evidence has shown that the bibenzyl molecule was formed by the coupling reaction between two benzyl radicals in plasma. The spectroscopic characteristics of toluene monomer and excimer are correlated with a kinetic model in plasma. PMID:19049320

  11. Radio emission from AM Herculis-type binaries

    NASA Technical Reports Server (NTRS)

    Chanmugam, G.; Dulk, G. A.

    1982-01-01

    A VLA search for 4.9 GHz radiation from the magnetic cataclysmic variable AM Her, along with the similar EF Eri binary, has led to the discovery of AM Her radio emission having a flux density of 0.67 + or - 0.052 mJy, where 1 mJy is equal to 10 to the -29th W/sq m per Hz. Neither AM Her circular polarization nor EF Eri were detected. The AM Her data are shown to be consistent with a model in which radiation is due to geosynchrotron emission from electrons of energies of a few hundred keV, which are trapped in the magnetosphere of the white dwarf element of the cataclysmic variable.

  12. Considerations on the radio emission from extended air showers

    NASA Astrophysics Data System (ADS)

    Conti, E.; Sartori, G.

    2016-05-01

    The process of radio emission from extended air showers produced by high energy cosmic rays has reached a good level of comprehension and prediction. It has a coherent nature, so the emitted power scales quadratically with the energy of the primary particle. Recently, a laboratory measurement has revealed that an incoherent radiation mechanism exists, namely, the bremsstrahlung emission. In this paper we expound why bremsstrahlung radiation, that should be present in showers produced by ultra high energy cosmic rays, has escaped detection so far, and why, on the other side, it could be exploited, in the 1–10 GHz frequency range, to detect astronomical γ-rays. We propose an experimental scheme to verify such hypothesis, which, if correct, would deeply impact on the observational γ-ray astronomy.

  13. The sources of Uranus' dominant nightside radio emissions

    NASA Technical Reports Server (NTRS)

    Kaiser, M. L.; Desch, M. D.; Curtis, S. A.

    1987-01-01

    The broad-bandwidth radio emission detected by Voyager 2 over the nightside of Uranus is examined. It is concluded that the source location of the smooth component is consistent with emission originating near the electron gyrofrequency from a small set of field lines whose foot points lie near the Uranomagnetic southern (dark) pole. The source centroid is at L = 11.5, and extends in latitude between about L = 8 and L = 25. This deduced source region is primarily on closed field lines that pass through the outer radiation belt and have their opposite foot points near the Uranomagnetic northern pole (near the present epoch terminator). The source location of the bursty component is less well defined but is consistent with the set of open field lines which map down to the region surrounding the planet's south magnetic dipole tip.

  14. 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.

  15. Radio emission of sea surface at centimeter wavelengths and is fluctuations

    NASA Technical Reports Server (NTRS)

    Tseytlin, N. M.; Shutko, A. M.; Zhislin, G. M.

    1981-01-01

    The eigen thermal radio emission of the sea was examined as well as the agitated surface of the sea when the reflection (scattering) is similar in nature to diffused scattering. The contribution of this emission to the total emission of the sea is practically constant in time, and the time fluctuations of the radio emissions of the sea are basically determined only by a change in the eigen emission of the sea, connected with the agitation.

  16. AURORAL RADIO EMISSION FROM STARS: THE CASE OF CU VIRGINIS

    SciTech Connect

    Trigilio, Corrado; Leto, Paolo; Umana, Grazia; Buemi, Carla S.; Leone, Francesco

    2011-09-20

    CU Virginis is a rapidly rotating Magnetic Chemically Peculiar star with at present unique characteristics as a radio emitter. The most intriguing one is the presence of intense, 100% circularly polarized radiation ascribed to a cyclotron maser. Each time the star rotates, this highly beamed emission points two times toward the Earth, like a pulsar. We observed CU Vir in 2010 April with the Expanded Very Large Array in two bands centered at 1450 and 1850 MHz. We covered nearly the whole rotational period, confirming the presence of the two pulses at a flux density up to 20 mJy. Dynamical spectra, obtained with unprecedented spectral and temporal sensitivity, allow us to clearly see the different time delays as a function of frequency. We interpret this behavior as a propagation effect of the radiation inside the stellar magnetosphere. The emerging scenario suggests interesting similarities with the auroral radio emission from planets, in particular with the Auroral Kilometric Radiation from Earth, which originates at few terrestrial radii above the magnetic poles and was only recently discovered to be highly beamed. We conclude that the magnetospheres of CU Vir, Earth, and other planets, maybe also exoplanets, could have similar geometrical and physical characteristics in the regions where the cyclotron maser is generated. In addition, the pulses are perfect 'markers' of the rotation period. This has given us for the first time the possibility to measure with extraordinary accuracy the spin-down of a star on or near the main sequence.

  17. Sharing Planetary Radio Emission Dataset in the Virtual Observatory

    NASA Astrophysics Data System (ADS)

    Cecconi, B.; Hess, S.; Le Sidaner, P.; Erard, S.; Coffre, A.; Thétas, E.; André, N.; Jacquey, C.

    2013-09-01

    In the double frame of the preparation of the ESA-led JUICE mission and the development of a planetary sciences virtual observatory (VO), we are proposing a new set of tools directed to data providers as well as users, in order to ease data sharing and discovery. We will focus on ground based planetary radio observations (thus mainly Jupiter radio emissions), trying for instance to enhance the temporal coverage of jovian decametric emission. The data service we will be using is EPN-TAP, a planetary science data access protocol developed by Europlanet/IDIS (Integrated and Distributed Information Service). This protocol is derived from IVOA (International Virtual Observatory Alliance) standards. The Jupiter Routine Observations from the Nançay Decameter Array are already shared on the planetary science VO using this protocol. We will first introduce the VO tools and concepts of interest for the planetary radioastronomy community. We will then present the various data formats now used for such data services, as well as their associated metadata. We will finally show various prototypical tools that make use of this shared datasets.

  18. Sharing Planetary Radio Emission Dataset in the Virtual Observatory

    NASA Astrophysics Data System (ADS)

    Cecconi, B.; Hess, S.; Le Sidaner, P.; Coffre, A.; Thetas, E.; andre, N.

    2013-12-01

    In the double frame of the preparation of the ESA-led JUICE mission and the development of a planetary sciences virtual observatory (VO), we are proposing a new set of tools directed to data providers as well as users, in order to ease data sharing and discovery. We will focus on ground based planetary radio observations (thus mainly Jupiter radio emissions), trying for instance to enhance the temporal coverage of jovian decametric emission. The data service we will be using is EPN-TAP, a planetary science data access protocol developed by Europlanet/IDIS (Integrated and Distributed Information Service). This protocol is derived from IVOA (International Virtual Observatory Alliance) standards. The Jupiter Routine Observations from the Nançay Decameter Array are already shared on the planetary science VO using this protocol. We will first introduce the VO tools and concepts of interest for the planetary radioastronomy community. We will then present the various data formats now used for such data services, as well as their associated metadata. We will finally show various prototypical tools that make use of this shared datasets.

  19. Sharing Planetary Radio Emission Dataset in the Virtual Observatory

    NASA Astrophysics Data System (ADS)

    Cecconi, Baptiste; Le Sidaner, Pierre; Hess, Sebastien; Girard, Julien; Thetas, Emmanuel; Coffre, Andree; Malapert, Jean-Christophe; Genot, Vincent

    In the double frame of the preparation of the ESA-led JUICE mission and the development of a planetary sciences virtual observatory (VO), we are proposing a new set of tools directed to data providers as well as users, in order to ease data sharing and discovery. We will focus on ground based planetary radio observations (thus mainly Jupiter radio emissions), trying for instance to enhance the temporal coverage of jovian decametric emission. The data service we will be using is EPN-TAP, a planetary science data access protocol developed by Europlanet/IDIS (Integrated and Distributed Information Service). This protocol is derived from IVOA (International Virtual Observatory Alliance) standards. The Jupiter Routine Observations from the Nançay Decameter Array are already shared on the planetary science VO using this protocol. We will first introduce the VO tools and concepts of interest for the planetary radioastronomy community. We will then present the various data formats now used for such data services, as well as their associated metadata. We will finally show various prototypical tools that make use of this shared datasets.

  20. Sharing Planetary Radio Emission Dataset in the Virtual Observatory

    NASA Astrophysics Data System (ADS)

    Cecconi, Baptiste; Hess, Sebastien; Le Sidaner, Pierre; Erard, Stéphane; Coffre, Andrée; Thétas, Emmanuel; André, Nicolas; Jacquey, Christian

    2013-04-01

    In the double frame of the preparation of the ESA-led JUICE mission and the development of a planetary sciences virtual observatory (VO), we are proposing a new set of tools directed to data providers as well as users, in order to ease data sharing and discovery. We will focus on ground based planetary radio observations (thus mainly Jupiter radio emissions), trying for instance to enhance the temporal coverage of jovian decametric emission. The data service we will be using is EPN-TAP, a planetary science data access protocol developed by Europlanet/IDIS (Integrated and Distributed Information Service). This protocol is derived from IVOA (International Virtual Observatory Alliance) standards. The Jupiter Routine Observations from the Nançay Decameter Array are already shared on the planetary science VO using this protocol. We will first introduce the VO tools and concepts of interest for the planetary radioastronomy community. We will then present the various data formats now used for such data services, as well as their associated metadata. We will finally show various prototypical tools that make use of this shared datasets.

  1. In situ observations of medium frequency auroral radio emissions

    NASA Astrophysics Data System (ADS)

    Broughton, M.; Labelle, J. W.; Pfaff, R. F.; Parrot, M.; Yan, X.; Burchill, J. K.

    2013-12-01

    The auroral ionosphere is a region rich with plasma waves that can be studied both in space and on the ground. These waves may mediate energy exchange between particle populations and provide information about the local plasma properties and boundaries. Auroral medium frequency (MF) burst is an impulsive radio emission observed at ground-level from 1.3-4.5 MHz that is associated with local substorm onset. There have been two recent reports of impulsive, broadband, MF waves at high latitudes. Burchill and Pfaff [2005] reported observations from the FAST satellite of impulsive, broadband, MF and low frequency (LF) radio waves. Using data from the DEMETER satellite, Parrot et al. [2009] surveyed MF waves caused by lightning. This study did show a high-latitude population of MF waves. We investigate whether the waves observed by these two satellites are related to auroral MF burst. Using FAST satellite burst mode electric field data from high-latitude (> 60 degrees magnetic), low-altitude (< 1000 km) intervals of moderate to large geomagnetic activity (Kp > 3) from 1996-2002, we have found forty-four examples of impulsive MF waves, all of which are associated with impulsive LF waves. Although MF burst and the waves observed by FAST have similar spectral signatures, they have different magnetic local time dependencies, which suggests that they may be unrelated. A study of MF waves observed at high latitude by DEMETER is ongoing. In situ observations of MF burst could provide crucial information about this heretofore unexplained natural radio emission.

  2. Are supernovae radio sources - A search for radio emission from young supernova remnants

    NASA Technical Reports Server (NTRS)

    Brown, R. L.; Marscher, A. P.

    1978-01-01

    A search has been conducted for radio emission at 11 and 3.7 cm from 46 recent supernovae having accurately determined positions and ages of a few months to 79 years. None of these supernovae was detected at a flux density greater than 5-10 mJy. These negative results cannot be explained by internal absorption and are thus due to intrinsically weak synchrotron emission in young supernova remnants. There are two possibilities: either (1) relativistic particles are accelerated not by the supernova outburst but by processes occurring much later (at least about 75 years) in the remnant or (2) the magnetic field in the young remnants evolves very slowly, in proportion to the inverse square root of time, so that its value in the remnants observed was no more than about 0.002 gauss. The constraints the observations place on these possibilities and on the energy in cosmic rays in young remnants are discussed. Gamma-ray observations at times of no more than about 1 year following an outburst will allow one to discriminate between the two alternative explanations of the radio results.

  3. Search for Cyclotron-maser Radio Emission from Extrasolar Planets

    NASA Astrophysics Data System (ADS)

    Dulk, G. A.; Leblanc, Y.; Bastian, T. S.

    1997-07-01

    There is reason to believe that extrasolar planets and/or brown dwarfs of mass about 1 to 50 M_J have magnetic fields, that they emit extremely intense cyclotron-maser radiation at metric wavelengths, and that this radiation may be detectable with sensitive radio telescopes like the VLA. The radiation is emitted at the electron cyclotron frequency, and has been detected from Earth, Jupiter, Saturn, Uranus and Neptune, from the Sun, from flare stars, and close binaries. The frequency range of cyclotron maser radiation is fixed by the magnetic field strength on the object. To be detected at, say 0.33 GHz, the required field strength is 118 G, which is intermediate between the 14 G field of Jupiter and the ~ 1000 G field of stellar active regions. An estimation of the flux density of the expected radiation can be made from an interpolation between Jupiter's radio emission (10(10) mJy at 5 AU) and that of nearby red dwarf stars ( ~ 100 mJy at 3 pc). Thus the flux from a planet or brown dwarf 3 to 30 times massive than Jupiter is plausibly 1 to 10 mJy, easily detectable with the VLA. If emission is detected, several important parameters about the planet can be deduced: the strength of its magnetic field, the period of its rotation, and the possible existence of a moon such as Jupiter's Io. Possible means of distinguishing stellar maser emissions from those of planets include: 1) Temporal variations and spectra differ from stars to planets. 2) The polarization is likely to be 100% circular or elliptical for planets, but not for stars. We have searched for exoplanet radio emission with 60 hours of observations with the VLA during November 1996. The observed stars with giant planets or brown dwarfs included 51 Peg, 70 Vir, 47 UMa, 55 CnC, Tau Boo, Gl 229, and HD 114762. We will present the method of observation, the limitations due to confusion and background noise, and the results.

  4. Polarized radio emission from extensive air showers measured with LOFAR

    SciTech Connect

    Schellart, P.; Buitink, S.; Corstanje, A.; Enriquez, J.E.; Falcke, H.; Hörandel, J.R.; Krause, M.; Nelles, A.; Rachen, J.P.; Veen, S. ter; Thoudam, S.

    2014-10-01

    We present LOFAR measurements of radio emission from extensive air showers. We find that this emission is strongly polarized, with a median degree of polarization of nearly 99%, and that the angle between the polarization direction of the electric field and the Lorentz force acting on the particles, depends on the observer location in the shower plane. This can be understood as a superposition of the radially polarized charge-excess emission mechanism, first proposed by Askaryan and the geomagnetic emission mechanism proposed by Kahn and Lerche. We calculate the relative strengths of both contributions, as quantified by the charge-excess fraction, for 163 individual air showers. We find that the measured charge-excess fraction is higher for air showers arriving from closer to the zenith. Furthermore, the measured charge-excess fraction also increases with increasing observer distance from the air shower symmetry axis. The measured values range from (3.3± 1.0)% for very inclined air showers at 25 m to (20.3± 1.3)% for almost vertical showers at 225 m. Both dependencies are in qualitative agreement with theoretical predictions.

  5. Two component model for X-ray emission of radio selected QSO's

    NASA Technical Reports Server (NTRS)

    Isobe, T.; Feigelson, E. D.; Singh, K. P.; Kembhavi, A.

    1986-01-01

    Using a large database of radio, optical, and x ray luminosities of AGNs with survival analysis, it was found that the x ray emission of the radio selected quasars has two components. One is related to the optical luminosity and the other is related to the radio luminosity.

  6. The ATCA REXCESS Diffuse Emission Survey (ARDES) - I. Detection of a giant radio halo and a likely radio relic

    NASA Astrophysics Data System (ADS)

    Shakouri, S.; Johnston-Hollitt, M.; Pratt, G. W.

    2016-07-01

    We present the results of the radio halo survey of 16 REXCESS southern clusters up to a redshift of 0.2 with the Australia Telescope Compact Array (ATCA) at 1.4 and 2.1 GHz. This cluster sample called the ATCA REXCESS Diffuse Emission Survey (ARDES) includes clusters in a wide range of X-ray luminosities and is morphologically unbiased. We find two diffuse radio sources in the clusters RXCJ2234.5-3744 (Abell 3888) and RXCJ0225.1-2928. The diffuse radio emission in RXCJ2234.5-3744 is a giant radio halo and the diffuse emission in RXCJ0225.1-2928 is a peculiar radio relic candidate. The radio halo has a spectral index of α = -1.48 ± 0.14 and the K-corrected P1.4 is 1.9 ± 0.2 × 1024 W Hz-1. The properties of the detected halo are consistent with both the current P1.4-LX and P1.4-YSZ correlations. The putative radio relic is located approximately 1 Mpc from the cluster in a filament and has a physical extent of 346 ± 20 kpc and a power of P1.4 = 3.3 ± 0.8 × 1023 W Hz-1, which places it in the lower power region of currently known relics.

  7. Using Radio Emissions to Understand Solar Particle Events

    NASA Astrophysics Data System (ADS)

    Cane, H. V.; Richardson, I. G.; Erickson, W.

    2014-12-01

    Streams of low energy electrons propagating from the low corona out along open field lines into the heliosphere produce radio emissions that drift rapidly to successively lower frequencies (type III bursts). The presence of type III bursts allows particles detected in situ to be traced back to their associated solar events. This includes high energy ions which are nearly always accompanied by low energy electrons that generate type III bursts. By examining hundreds of type III radio bursts observed by the WAVES instrument on WIND that accompany energetic particle increases, a number of insights into the origins of these particle increases and particle propagation have been obtained and will be discussed. These insights include the presence of flare particles in the majority of particle events and the existence of cross-field transport in the interplanetary medium. A new result is that there are small Fe-rich increases observed by the EPACT instrument on WIND that are not associated with co-temporal flares (i.e., there are no accompanying type III bursts) meaning that the association rate of Fe-rich "impulsive" events with coronal mass ejections is more than 90%.

  8. Factors controlling the occurrence of the Jovian decametric radio emission

    NASA Astrophysics Data System (ADS)

    Zaitsev, V. V.; Shaposhnikov, V. E.; Rucker, H. O.

    The statistical analysis of occurrence of Io-related Jovian decametric radio (DAM) emission shows that the occurrence of the emission increase when Io is in the longitude range 120° -300° (Io's longitude in the frame III). Another result of the statistical analysis is a predominance of DAM emission sources in the northern hemisphere of Jupiter. We show that these phenomena are the result of the joint effect of two factors - the variation of the efficiency of particle acceleration in the ionosphere of the satellite Io and the variation of the broadening of the angular spectrum of accelerated particles during their pass through Io's plasma torus depending on Io's longitude. The planes of the rotational, magnetic and centrifugal (for Io's torus) equators do not coincide. As a result the magnetic field near the satellite Io, which determines the accelerated particle efficiency [1], changes periodically. The most effective acceleration takes place in the longitude range 120° ≤ λIo ≤ 300° . Just in this longitude range the satellite Io appears to be "screened" by the plasma torus of the southern hemisphere. Making their way to the southern hemisphere, the particles are scattered in the torus plasma 2° , within which they and withdrawn from a narrow range of pitch-angles ∆θ0 can reach the southern hemisphere [2]. Therefore in the mentioned longitude range northern sources of DAM emission should be concentrated. At the same time in the longitude range, where the "screening" effect of the plasma torus in the southern direction is negligible, the efficiency of the accelerated mechanism is essentially smaller due to the decrease of the magnetic field near Io. Therefore the southern sources turn to be weaker and are located mainly outside the longitude range, where the emission from the northern sources predominates. Since the emission from the northern sources predominates, the active longitudes are determined basically by this emission and are in the range 120

  9. Type II solar radio bursts predicted by 3-D MHD CME and kinetic radio emission simulations

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    Impending space weather events at Earth are often signaled by type II solar radio bursts. These bursts are generated upstream of shock waves driven by coronal mass ejections (CMEs) that move away from the Sun. We combine elaborate three-dimensional (3-D) magnetohydrodynamic predictions of realistic CMEs near the Sun with a recent analytic kinetic radiation theory in order to simulate two type II bursts. Magnetograms of the Sun are used to reconstruct initial solar magnetic and active region fields for the modeling. STEREO spacecraft data are used to dimension the flux rope of the initial CME, launched into an empirical data-driven corona and solar wind. We demonstrate impressive accuracy in time, frequency, and intensity for the two type II bursts observed by the Wind spacecraft on 15 February 2011 and 7 March 2012. Propagation of the simulated CME-driven shocks through coronal plasmas containing preexisting density and magnetic field structures that stem from the coronal setup and CME initiation closely reproduce the isolated islands of type II emission observed. These islands form because of a competition between the growth of the radio source due to spherical expansion and a fragmentation of the radio source due to increasingly radial fields in the nose region of the shock and interactions with streamers in the flank regions of the shock. Our study provides strong support for this theory for type II bursts and implies that the physical processes involved are understood. It also supports a near-term capability to predict and track these events for space weather predictions.

  10. On the elliptical polarization of Jupiter's decametric radio emission

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    The origin of the 100 percent elliptical polarization of Jupiter's decametric radio emission is investigated. The transfer of polarized radiation when coupling of the Stokes parameters is important is studied, and it is found, in agreement with earlier authors, that the density in and near the source region must be so low that the polarization remains fixed along the ray path. The polarization of the cyclotron maser radiation in these circumstances is determined, and it is found that the dispersion relation of the rarefied plasma composed of energetic, anisotropic electrons is like that in the vacuum. It is also found that the growth rate is sufficient to saturate the maser and account for the observed brightness temperature. Possible sources of plasma in and near the source region in Jupiter's inner, polar magnetosphere are considered.

  11. Jovian radio emission below 5 mHz

    NASA Technical Reports Server (NTRS)

    Evans, D. R.

    1983-01-01

    The GS2 and GS3 operational modes of the planetary radio astronomy experiment on the Voyager 1 spacecraft are described as well as the dynamic spectra obtained. Repeated pulses of unpolarized emission (P bursts) recorded by GS2 were studied and attempts were made to correlate their occurrences, which have sudden onset and conclusion, with features in the GS3 dynamic spectra. The influence of the phase of any of the Galilean satellites or the subspacecraft system 3 longitude on P bursts was also investigated. Tables show Voyage 1 GS2 frequencies, high quality Jovian P bursts, and the geometry and pulse repetition frequency of the P burst groups. Plotted bursts are included.

  12. Analysis of Jovian decametric data: Study of radio emission mechanisms

    NASA Technical Reports Server (NTRS)

    Staelin, D. H.; Arias, T. A.

    1985-01-01

    Data gathered by the Voyager 1 and Voyager 2 Planetary Radio Astronomy Experiments (PRA) are unique in many ways including their frequency range, time resolution, polarization information and geometric characteristics. Studies of rapidly varying phenomena have thus far been hampered by paper display techniques which require large amounts of paper to exploit the full PRA time resolution. A software package capable of effectively displaying full 6s resolution PRA dynamic spectra on a high quality video monitor while compensating for the aforementioned variations was developed. The most striking phenomena revealed by the new display techniques is called Modulated Spectral Activity (MSA) because of its appearance in dynamic spectra as a series at least two parallel emission bands which drift back and forth in frequency on time scales of tens of seconds. In an attempt to locate and understand the MSA source mechanism, a catalogue has been compiled of the start and end of all known MSA events.

  13. The relationship of storm severity to directionally resolved radio emissions

    NASA Technical Reports Server (NTRS)

    Johnson, R. O.; Bushman, M. L.; Sherrill, W. M.

    1980-01-01

    Directionally resolved atmospheric radio frequency emission data were acquired from thunderstorms occurring in the central and southwestern United States. In addition, RF sferic tracking data were obtained from hurricanes and tropical depressions occurring in the Gulf of Mexico. The data were acquired using a crossed baseline phase interferometer operating at a frequency of 2.001 MHz. The received atmospherics were tested for phase linearity across the array, and azimuth/elevation angles of arrival were computed in real time. A histogram analysis of sferic burst count versus azimuth provided lines of bearing to centers of intense electrical activity. Analysis indicates a consistent capability of the phase linear direction finder to detect severe meteorological activity to distances of 2000 km from the receiving site. The technique evidences the ability to discriminate severe storms from nonsevere storms coexistent in large regional scale thunderstorm activity.

  14. The magnetoionic modes and propagation properties of auroral radio emissions

    NASA Technical Reports Server (NTRS)

    Calvert, Wynne; Hashimoto, Kozo

    1990-01-01

    The nature of the magnetoionic wave modes which accompany the aurora is clarified here by a detailed analysis, using multiple techniques, of DE 1 auroral radio observations. All four of the possible magnetoionic wave modes are found to occur, apparently emitted from two different source regions on the same auroral field line. AKR originates primarily in the X mode near the electron cyclotron frequency, and is frequently also accompanied by a weaker O-mode component from the same location. The next most prominent auroral emission is the W-mode auroral hiss originating from altitudes always well below the DE 1 satellite at frequencies below the local cyclotron frequency. The previously reported Z-mode auroral radiation was also detected, but from sources also below the satellite at the poleward edge of the cavity, and not from the expected AKR source at the cyclotron frequency.

  15. Solar wind control of Jupiter's decametric radio emission

    NASA Technical Reports Server (NTRS)

    Barrow, C. H.; Genova, F.; Desch, M. D.

    1986-01-01

    Observations of the solar wind close to Jupiter are compared with the decametric radio emission (DAM), using data recorded by Voyager 1 and Voyager 2 during 1979. The Non-Io DAM, recorded by both spacecraft and combined using the superposed epoch technique, is found to correlate with the solar wind density and velocity, as well as with the interplanetary magnetic field (IMF) magnitude. In agreement with earlier work using ground-based observations, there are indications that the Non-Io DAM is somehow associated with magnetic sector structure although the precise details of the relationship are still not known and it is not clear if this is a fundamental effect or some secondary effect of intercorrelation.

  16. Radio emission signature of Saturn immersions in Jupiter's magnetic tail

    NASA Technical Reports Server (NTRS)

    Desch, M. D.

    1983-01-01

    During the interval from about May through August 1981, when Voyager 2 was inbound to Saturn, the Planetary Radio Astronomy instrument measured repeated, dramatic decreases in the intensity of the Saturn Kilometric Radiation (SKR). The emission dropouts averaged two orders of magnitude below mean energy levels and varied from about 1 to 10 Saturn rotations in duration. Comparison with pre-Saturn encounter Voyager 1 observations (June to November, 1980) shows that the SKR dropouts were unique to the Voyager 2 observing interval, consistent with the closer proximity of Saturn to Jupiter's distant magnetotail in 1981. Further, the dropouts occurred on the average at times when Voyager 2 is known to have been within or near Jupiter's magnetic tail.

  17. Herringbone bursts associated with type II solar radio emission

    NASA Technical Reports Server (NTRS)

    Cairns, I. H.; Robinson, R. D.

    1987-01-01

    Detailed observations of the herringbone (HB) fine structure on type II solar radio bursts are presented. Data from the Culgoora radiospectrograph, radiometer and radioheliograph are analyzed. The characteristic spectral profiles, frequency drift rates and exciter velocities, fluxes, source sizes, brightness temperatures, and polarizations of individual HB bursts are determined. Correlations between individual bursts within the characteristic groups of bursts and the properties of the associated type II bursts are examined. These data are compatible with HB bursts being radiation at multiples of the plasma frequency generated by electron streams accelerated by the type II shock. HB bursts are physically distinct phenomena from type II and type III bursts, differing significantly in emission processes and/or source conditions; this conclusion indicates that many of the presently available theoretical ideas for HB bursts are incorrect.

  18. Direct evidence for solar wind control of Jupiter's hectometer-wavelength radio emission

    NASA Technical Reports Server (NTRS)

    Desch, M. D.; Barrow, C. H.

    1984-01-01

    Observations of the solar wind close to Jupiter by the Voyager 1 and Voyager 2 spacecraft in 1978 and 1979 are compared with the hectometer-wavelength radio emission from the planet. A significant positive correlation is found between variations in the solar wind plasma density at Jupiter and the level of Jovian radio emission output. During the 173-day interval studied for the Voyager 2 data the radio emission displayed a long-term periodicity of about 13 days, identical to that shown by the solar wind density at Jupiter and consistent with the magnetic sector structure association already proposed for ground-based observations of the decameter-wavelength emission.

  19. Direct evidence for solar wind control of Jupiter's hectometer-wavelength radio emission

    NASA Technical Reports Server (NTRS)

    Desch, M. D.; Barrow, C. H.

    1984-01-01

    Observations of the solar wind close to Jupiter, by the Voyager 1 and Voyager 2 spacecraft in 1978 and 1979, are compared with the hectometer wavelength radio emission from the planet. A significant positive correlation is found between variations in the solar wind plasma density at Jupiter and the level of Jovian radio emission output. During the 173-day interval studied for the Voyager 2 data, the radio emission displayed a long term periodicity of about 13 days, identical to that shown by the solar wind density at Jupiter and consistent with the magnetic sector structure association already proposed for groundbased observations of the decameter wavelength emission.

  20. The source location of certain Jovian decametric radio emissions

    NASA Technical Reports Server (NTRS)

    Calvert, W.

    1983-01-01

    Evidence is presented which supports the concept that certain of the Jovian decametric radio waves originate as northern hemisphere extraordinary mode cyclotron emissions. The wave signals received by Voyager 1 near 10 MHz shortly after the closest approach to Jupiter were found to exhibit cusps in the fringe pattern which can be attributed to Faraday rotation in the Io plasma torus. At nearly the same time, the wave polarization near 1 MHz was found to exhibit a sudden reversal of its rotation sense, indicating that the wave path for those frequencies had also become perpendicular to the magnetic field at the spacecraft. It was determined that the waves came from the northern hemisphere at progressively lower altitudes with increasing frequency, and if the source is assumed to be associated with an L = 6 field line, the emission appears to have occurred near the source cyclotron frequency somewhere in the local midnight sector. The evidence indicates that the source is at the Io flux tube and that the emitted wave mode must have been extraordinary. In addition, the emitted wave polarization must have been substantially noncircular which would require a low plasma density near the source, much like that which occurs with auroral kilometric radiation at the earth.

  1. Modeling of the Intracloud Lightning Discharge Radio Emission

    NASA Astrophysics Data System (ADS)

    Iudin, D. I.; Iudin, F. D.; Hayakawa, M.

    2015-08-01

    This paper aims at analyzing the broadband part of electromagnetic emission from thunderclouds in a frequency range of tens of kilohertz to hundreds of megahertz. A model of the intracloud lightning discharge formation is presented. The lightning formation is described as a stochastic growth of the branching discharge channels, which is determined by the electrostatic field. The dynamics of the electric field and of the charge distribution over the lightning structure is calculated deterministically. The effect of the initial charge density in the cloud and the parameters of the conducting channels on spatio-temporal characteristics of the currents and structure of the lightning discharge is studied. The discharge radio emission is calculated by summing up the radiation fields of each channel at the observation point. The standard model for a separate discharge current is adopted, and the electromagnetic radiation in the far zone is estimated. It is found that the obtained frequency spectra exhibit a universal power-law behavior. The results of the modeling agree with known experimental data.

  2. Outer heliospheric radio emissions. II - Foreshock source models

    NASA Technical Reports Server (NTRS)

    Cairns, Iver H.; Kurth, William S.; Gurnett, Donald A.

    1992-01-01

    Observations of LF radio emissions in the range 2-3 kHz by the Voyager spacecraft during the intervals 1983-1987 and 1989 to the present while at heliocentric distances greater than 11 AU are reported. New analyses of the wave data are presented, and the characteristics of the radiation are reviewed and discussed. Two classes of events are distinguished: transient events with varying starting frequencies that drift upward in frequency and a relatively continuous component that remains near 2 kHz. Evidence for multiple transient sources and for extension of the 2-kHz component above the 2.4-kHz interference signal is presented. The transient emissions are interpreted in terms of radiation generated at multiples of the plasma frequency when solar wind density enhancements enter one or more regions of a foreshock sunward of the inner heliospheric shock. Solar wind density enhancements by factors of 4-10 are observed. Propagation effects, the number of radiation sources, and the time variability, frequency drift, and varying starting frequencies of the transient events are discussed in terms of foreshock sources.

  3. Costs of controlling emissions from the manufacture of silicon photovoltaic cells using dendritic web technology

    SciTech Connect

    Wilenitz, I.

    1983-11-01

    Detailed analyses were conducted to determine environmental control costs associated with the production of silicon dendritic web photovoltaic (PV) cells. In these analyses (i) likely manufacturing processing steps were identified, (ii) material inputs and uncontrolled material outputs were estimated, (iii) need for and capability of environmental control equipment were examined, and (iv) capital and operation and maintenance costs for environmental controls for integrated and disaggregated plant designs were estimated. These estimates were developed for a hypothetical facility with a yearly output of PV cells capable of producing 10 MWp. Analysis suggested that the annualized incremental environmental control costs, based on capital recovery over a 10 year plant life, would be 1.4 cents and 2.8 cents per watt for integrated and disaggregated plant designs, respectively. Capital costs ranged from 50% to 55% (integrated) and 36% to 40% (disaggregated) of the estimated costs; the ranges reflected differences in assumed real discount rates. Because of the small emission flows projected, treatment equipment to be used, for the most part, represents the smallest size readily available from equipment manufacturers. Consequently, larger emission flows could be accommodated without additional capital costs. Total control costs are small in comparison with current production costs for silicon photovoltaic devices ($5/watt), but may be of greater importance at projected production cost of $0.5 to 1.0/watt. These conclusions may not apply to other material or process options.

  4. Offset, tilted dipole models of Uranian smooth high-frequency radio emission

    NASA Technical Reports Server (NTRS)

    Schweitzer, Andrea E.; Romig, Joseph H.; Evans, David R.; Sawyer, Constance B.; Warwick, James W.

    1990-01-01

    The smooth high-frequency (SHF) component of the radio emission detected during the Voyager 2 encounter with Uranus (January 1986) is studied. An offset tilted dipole (OTD) investigation of the SHF emission at L shells is carried out within the range of the bursty source locations. A viable high L shell model is presented. It is suggested that Miranda, which reaches a minimum L shell at L = 5, may be related to the timing of several types of radio emissions.

  5. Radio Galaxies.

    ERIC Educational Resources Information Center

    Downes, Ann

    1986-01-01

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

  6. Radio Emissions Precursors of Impulsive Phase of Solar Flares Recorded by CALLISTO-BR

    NASA Astrophysics Data System (ADS)

    Fernandes, Francisco; Cunha-Silva, Rafael; Galdino, Marcela; Sodré, Zuleika

    2016-07-01

    A solar flare consists in an eruptive process and involves a sudden release of energy generated by processes carried on from instabilities in the magnetic configuration at solar atmosphere, generating emissions at different wavelengths. Usually, the pre-flare phase presents an increasing of soft X-ray, ultraviolet and radio emissions. In this work, we present a survey of solar radio emission recorded in metric wavelengths (45 - 250 MHz) by CALLISTO-BR spectrograph, belong to the e-Callisto network, associated with pre-flare phase of solar X-rays flares. A sample of 281 radio emissions was analyzed, and 120 were identified as precursor emissions of X-rays flares. The main results of the statistics can be summarized as: (a) 55% of the precursor radio emissions start less than 60 minutes before the beginning of the associated X-ray flare and about 20% start less than 20 minutes before the X-ray emission; (b) 27% of flares with precursor emissions are classified as B class, 61% of C class, and less than 22% of M class. No precursors radio emissions were associated with X class flare; (c) about 42% of radio precursor emissions are of type III bursts and 33% have complex morphology, as drifting pulsating structures. Analysis of global emission trends recorded during the precursor phase of the C4.8 flare of February 15, 2011 (14:32-14:51 UT) is also presented. The occurrence of radio emission during the pre-impulsive phase of a solar flare suggests the presence of plasma turbulence in the active region, since during the impulsive phase, when the energy is released, occur the heating of the plasma and increasing of soft X-ray emission as identified in the event analyzed. The results are presented and discussed.

  7. WFPC2 LRF Imaging of Emission-Line Nebulae in 3CR Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Privon, G. C.; O'Dea, C. P.; Baum, S. A.; Axon, D. J.; Kharb, P.; Buchanan, C. L.; Sparks, W.; Chiaberge, M.

    2008-04-01

    We present Hubble Space Telescope WFPC2 Linear Ramp Filter images of high surface brightness emission lines (either [O II], [O III], or H α + [N II]) in 80 3CR radio sources. We overlay the emission-line images on high-resolution VLA radio images (eight of which are new reductions of archival data) in order to examine the spatial relationship between the optical and radio emission. We confirm that the radio and optical emission-line structures are consistent with weak alignment at low redshift (z < 0.6) except in the compact steep-spectrum (CSS) radio galaxies where both the radio source and the emission-line nebulae are on galactic scales and strong alignment is seen at all redshifts. There are weak trends for the aligned emission-line nebulae to be more luminous and for the emission-line nebula size to increase with redshift and/or radio power. The combination of these results suggests that there is a limited but real capacity for the radio source to influence the properties of the emission-line nebulae at these low redshifts (z < 0.6). Our results are consistent with previous suggestions that both mechanical and radiant energy are responsible for generating alignment between the radio source and emission-line gas. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 05-26555. These observations are associated with program 5957.

  8. The connection between the 15 GHz radio and gamma-ray emission in blazars

    NASA Astrophysics Data System (ADS)

    Max-Moerbeck, W.; Richards, J. L.; Hovatta, T.; Pavlidou, V.; Pearson, T. J.; Readhead, A. C. S.; King, O. G.; Reeves, R.

    2015-03-01

    Since mid-2007 we have carried out a dedicated long-term monitoring programme at 15 GHz using the Owens Valley Radio Observatory 40 meter telescope (OVRO 40m). One of the main goals of this programme is to study the relation between the radio and gamma-ray emission in blazars and to use it as a tool to locate the site of high energy emission. Using this large sample of objects we are able to characterize the radio variability, and study the significance of correlations between the radio and gamma-ray bands. We find that the radio variability of many sources can be described using a simple power law power spectral density, and that when taking into account the red-noise characteristics of the light curves, cases with significant correlation are rare. We note that while significant correlations are found in few individual objects, radio variations are most often delayed with respect to the gamma-ray variations. This suggests that the gamma-ray emission originates upstream of the radio emission. Because strong flares in most known gamma-ray-loud blazars are infrequent, longer light curves are required to settle the issue of the strength of radio-gamma cross-correlations and establish confidently possible delays between the two. For this reason continuous multiwavelength monitoring over a longer time period is essential for statistical tests of jet emission models.

  9. Fluorescent dendritic organogels based on 2-(2'-hydroxyphenyl)benzoxazole: emission enhancement and multiple stimuli-responsive properties.

    PubMed

    Chen, Hui; Feng, Yu; Deng, Guo-Jun; Liu, Zhi-Xiong; He, Yan-Mei; Fan, Qing-Hua

    2015-07-27

    A new highly efficient and versatile poly(benzyl ether) dendritic organogelator HPB-G1 with 2-(2'-hydroxyphenyl)benzoxazole (HPB) at the focal point has been designed and synthesized. HPB-G1 can form stable organogels toward various apolar and polar organic solvents. Further studies revealed that intermolecular multiple π-π stacking interactions are the main driving forces for the formation of the organogels. Notably, dendron HPB-G1 exhibited a significantly enhanced emission in the gel state in contrast to weak emission in solution. Most interestingly, these dendritic organogels exhibited multiple stimuli-responsive behaviors upon exposure to environmental stimuli, including temperature, sonication, shear stress, and the presence of anions, metal cations, acids/bases, thus leading to reversible sol-gel phase transitions. PMID:26095320

  10. EMISSION PATTERNS OF SOLAR TYPE III RADIO BURSTS: STEREOSCOPIC OBSERVATIONS

    SciTech Connect

    Thejappa, G.; Bergamo, M.; MacDowall, R. J. E-mail: mbergamo@umd.edu

    2012-02-01

    Simultaneous observations of solar type III radio bursts obtained by the STEREO A, B, and WIND spacecraft at low frequencies from different vantage points in the ecliptic plane are used to determine their directivity. The heliolongitudes of the sources of these bursts, estimated at different frequencies by assuming that they are located on the Parker spiral magnetic field lines emerging from the associated active regions into the spherically symmetric solar atmosphere, and the heliolongitudes of the spacecraft are used to estimate the viewing angle, which is the angle between the direction of the magnetic field at the source and the line connecting the source to the spacecraft. The normalized peak intensities at each spacecraft R{sub j} = I{sub j} /{Sigma}I{sub j} (the subscript j corresponds to the spacecraft STEREO A, B, and WIND), which are defined as the directivity factors are determined using the time profiles of the type III bursts. It is shown that the distribution of the viewing angles divides the type III bursts into: (1) bursts emitting into a very narrow cone centered around the tangent to the magnetic field with angular width of {approx}2 Degree-Sign and (2) bursts emitting into a wider cone with angular width spanning from {approx} - 100 Degree-Sign to {approx}100 Degree-Sign . The plots of the directivity factors versus the viewing angles of the sources from all three spacecraft indicate that the type III emissions are very intense along the tangent to the spiral magnetic field lines at the source, and steadily fall as the viewing angles increase to higher values. The comparison of these emission patterns with the computed distributions of the ray trajectories indicate that the intense bursts visible in a narrow range of angles around the magnetic field directions probably are emitted in the fundamental mode, whereas the relatively weaker bursts visible to a wide range of angles are probably emitted in the harmonic mode.

  11. PREDICTION OF TYPE II SOLAR RADIO BURSTS BY THREE-DIMENSIONAL MHD CORONAL MASS EJECTION AND KINETIC RADIO EMISSION SIMULATIONS

    SciTech Connect

    Schmidt, J. M.; Cairns, Iver H.; Hillan, D. S.

    2013-08-20

    Type II solar radio bursts are the primary radio emissions generated by shocks and they are linked with impending space weather events at Earth. We simulate type II bursts by combining elaborate three-dimensional MHD simulations of realistic coronal mass ejections (CMEs) at the Sun with an analytic kinetic radiation theory developed recently. The modeling includes initialization with solar magnetic and active region fields reconstructed from magnetograms of the Sun, a flux rope of the initial CME dimensioned with STEREO spacecraft observations, and a solar wind driven with averaged empirical data. We demonstrate impressive accuracy in time, frequency, and intensity for the CME and type II burst observed on 2011 February 15. This implies real understanding of the physical processes involved regarding the radio emission excitation by shocks and supports the near-term development of a capability to predict and track these events for space weather prediction.

  12. Upper limits on gravitational wave emission from 78 radio pulsars

    NASA Astrophysics Data System (ADS)

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

    2007-08-01

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

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

    NASA Astrophysics Data System (ADS)

    Johnson, M. D.; Gwinn, C. R.; Demorest, P.

    2012-10-01

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

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

    SciTech Connect

    Johnson, M. D.; Gwinn, C. R.; Demorest, P. E-mail: cgwinn@physics.ucsb.edu

    2012-10-10

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

  15. Search for X-ray emission from the radio lobes of Scorpius X-1

    NASA Astrophysics Data System (ADS)

    Geldzahler, Barry; Hertz, Paul

    1987-11-01

    Images obtained with the low-energy imaging telescope on board the European X-Ray Astronomy Satellite have been searched for X-ray emission from the radio lobes of Sco X-1. After the scattered photons from the image of the central X-ray source in Sco X-1 are taken into account, no significant additional X-ray flux from the radio lobes can be detected above the background. The 3 sigma upper limit is less than 0.7 micro-Jy for the northeast radio lobe and less than 1.0 micro-J for the southwest radio lobe. This eliminates the embedded source model of Kundt and Gopal-Krishna as a viable model of the radio emission. These limits are three orders of magnitude too high to constrain models of synchrotron or inverse Compton X-ray emission.

  16. NEW LIMITS ON RADIO EMISSION FROM X-RAY DIM ISOLATED NEUTRON STARS

    SciTech Connect

    Kondratiev, V. I.; McLaughlin, M. A.; Lorimer, D. R.; Burgay, M.; Possenti, A.; Turolla, R.; Popov, S. B.; Zane, S. E-mail: maura.mclaughlin@mail.wvu.edu E-mail: burgay@ca.astro.it E-mail: roberto.turolla@pd.infn.it E-mail: sergepolar@gmail.com

    2009-09-01

    We have carried out a search for radio emission at 820 MHz from six X-ray dim isolated neutron stars (XDINSs) with the Robert C. Byrd Green Bank Radio Telescope. No transient or pulsed emission was found using fast folding, fast Fourier transform, and single-pulse searches. The corresponding flux limits are about 0.01 mJy for pulsed emission, depending on the integration time for the particular source and assuming a duty cycle of 2%, and 20 mJy for single dispersed pulses. These are the most sensitive limits to date on radio emission from XDINSs. There is no evidence for isolated radio pulses, as seen in a class of neutron stars known as rotating radio transients. Our results imply that either the radio luminosities of these objects are lower than those of any known radio pulsars, or they could simply be long-period nearby radio pulsars with high magnetic fields beaming away from the Earth. To test the latter possibility, we would need around 40 similar sources to provide a 1{sigma} probability of at least one of them beaming toward us. We also give a detailed description of our implementation of the Fast Folding Algorithm.

  17. Sharing Low Frequency Radio Emissions in the Virtual Observatory: Application for JUNO-Ground-Radio Observations Support.

    NASA Astrophysics Data System (ADS)

    Cecconi, B.; Savalle, R.; Zarka, P. M.; Anderson, M.; Andre, N.; Coffre, A.; Clarke, T.; Denis, L.; Ebert, R. W.; Erard, S.; Genot, V. N.; Girard, J. N.; Griessmeier, J. M.; Hess, S. L.; Higgins, C. A.; Hobara, Y.; Imai, K.; Imai, M.; Kasaba, Y.; Konovalenko, A. A.; Kumamoto, A.; Kurth, W. S.; Lamy, L.; Le Sidaner, P.; Misawa, H.; Nakajo, T.; Orton, G. S.; Ryabov, V. B.; Sky, J.; Thieman, J.; Tsuchiya, F.; Typinski, D.

    2015-12-01

    In the frame of the preparation of the NASA/JUNO and ESA/JUICE (Jupiter Icy Moon Explorer) missions, and the development of a planetary sciences virtual observatory (VO), we are proposing a new set of tools directed to data providers as well as users, in order to ease data sharing and discovery. We will focus on ground based planetary radio observations (thus mainly Jupiter radio emissions), trying for instance to enhance the temporal coverage of jovian decametric emission. The data service we will be using is EPN-TAP, a planetary science data access protocol developed by Europlanet-VESPA (Virtual European Solar and Planetary Access). This protocol is derived from IVOA (International Virtual Observatory Alliance) standards. The Jupiter Routine Observations from the Nancay Decameter Array are already shared on the planetary science VO using this protocol, as well as data from the Iitate Low Frquency Radio Antenna, in Japan. Amateur radio data from the RadioJOVE project is also available. The attached figure shows data from those three providers. We will first introduce the VO tools and concepts of interest for the planetary radioastronomy community. We will then present the various data formats now used for such data services, as well as their associated metadata. We will finally show various prototypical tools that make use of this shared datasets.

  18. Ultraviolet and Radio Emission from the Northern Middle Lobe of Centaurus A

    NASA Technical Reports Server (NTRS)

    Neff, Susan

    2009-01-01

    We present deep GALEX ultraviolet (135 - 280 nm) images of the Northern Middle Lobe (NML) of the nearby radio galaxy Centaurus A. We find that the ultraviolet emission appears to have a complex interaction with soft X-ray, H-alpha emission, and radio emission, which should help constrain various models of energy transport in the NML. We also present new 90cm VLA images of the NML. The radio morphology at this wavelength is indicative of a more complex system than either a straightforward flaring jet (Morganti et al. 1999) or a bubble with trailing stem (Saxton et al. 2001). New limits are placed on the lack of radio emission from any corresponding southern counterpart to the NML.

  19. Radio emission from extensive air showers as a method for cosmic-ray detection

    SciTech Connect

    Kalmykov, N. N.; Konstantinov, A. A.; Engel, R.

    2010-07-15

    At the present time, radio emission from extensive air showers (EASs) is being considered as a new promising method for detecting cosmic rays of energy in the region E{sub 0} > 5 x 10{sup 16} eV. Radio emission from an EAS whose development is simulated by the Monte Carlo method is calculated here. The field of radio emission from an EAS is calculated on the basis of two representations of a shower: that as a set of individual particles and that as a continuous set of currents. The sensitivity of radio emission to EAS parameters in the frequency range 10-100 MHz is investigated. The results can be used to analyze experiments that being presently performed (CODALEMA and LOPES) and those that are being planned for the future.

  20. Radio-Quiet Quasars in the VIDEO Survey: Evidence for AGN-powered radio emission below 1 mJy

    NASA Astrophysics Data System (ADS)

    White, Sarah; Jarvis, Matt; Haeussler, Boris; Maddox, Natasha

    2015-01-01

    Several lines of evidence suggest that the interaction between active galactic nucleus (AGN) activity and star formation is responsible for the co-evolution of black hole mass with galaxy bulge mass. Therefore studying this interplay is crucial to our understanding of galaxy formation and evolution. The new generation of radio surveys are able to play a key role in this area, as both processes produce radio emission.We use a combination of optical and near-infrared photometry to select a sample of 72 quasars from the VISTA Deep Extragalactic Observations (VIDEO) Survey, over 1 deg2. The depth of VIDEO allows us to study very low accretion rates and/or lower-mass black holes. 26% of the candidate quasar sample has been spectroscopically confirmed using the Southern African Large Telescope and the VIMOS VLT Deep Survey. We then use a radio-stacking technique to sample below the nominal flux-density threshold of existing Very Large Array data at 1.4 GHz. In agreement with other work, we show that a power-law fit to the radio number counts is inadequate, with an upturn in the counts being observed at these faint luminosities. Previous authors attribute this to an emergent star-forming population. However, by comparing radio emission from our quasars with that from a control sample of galaxies, we suggest that this emission is predominantly caused by accretion activity. Further support for an AGN origin is provided by a comparison of two independent estimates of star formation rate. These findings have important implications for modelling radio populations below 1 mJy, which is necessary for the development of the Square Kilometre Array.

  1. Searches for correlated X-ray and radio emission from X-ray burst sources

    NASA Technical Reports Server (NTRS)

    Johnson, H. M.; Catura, R. C.; Lamb, P. A.; White, N. E.; Sanford, P. W.; Hoffman, J. A.; Lewin, W. H. G.; Jernigan, J. G.

    1978-01-01

    The NRAO Green Bank interferometer has been used to monitor MXB 1730-335 and MXB 1837+05 during periods when 68 X-ray bursts were detected by X-ray observations. No significant radio emission was detected from these objects, or from MXB 1820-30 and MXB 1906+00, which emitted no bursts throughout the simultaneous observations. The data place upper limits on radio emission from these objects in the 2695 and 8085 MHz bands.

  2. LATE-TIME RADIO EMISSION FROM X-RAY-SELECTED TIDAL DISRUPTION EVENTS

    SciTech Connect

    Bower, Geoffrey C.; Cenko, S. Bradley; Silverman, Jeffrey M.; Bloom, Joshua S.; Metzger, Brian D.

    2013-02-15

    We present new observations with the Karl G. Jansky Very Large Array of seven X-ray-selected tidal disruption events (TDEs). The radio observations were carried out between 9 and 22 years after the initial X-ray discovery, and thus probe the late-time formation of relativistic jets and jet interactions with the interstellar medium in these systems. We detect a compact radio source in the nucleus of the galaxy IC 3599 and a compact radio source that is a possible counterpart to RX J1420.4+5334. We find no radio counterparts for five other sources with flux density upper limits between 51 and 200 {mu}Jy (3{sigma}). If the detections truly represent late radio emission associated with a TDE, then our results suggest that a fraction, {approx}> 10%, of X-ray-detected TDEs are accompanied by relativistic jets. We explore several models for producing late radio emission, including interaction of the jet with gas in the circumnuclear environment (blast wave model), and emission from the core of the jet itself. Upper limits on the radio flux density from archival observations suggest that the jet formation may have been delayed for years after the TDE, possibly triggered by the accretion rate dropping below a critical threshold of {approx}10{sup -2}-10{sup -3} M-dot {sub Edd}. The non-detections are also consistent with this scenario; deeper radio observations can determine whether relativistic jets are present in these systems. The emission from RX J1420.4+5334 is also consistent with the predictions of the blast wave model; however, the radio emission from IC 3599 is substantially underluminous, and its spectral slope is too flat, relative to the blast wave model expectations. Future radio monitoring of IC 3599 and RX J1420.4+5334 will help to better constrain the nature of the jets in these systems.

  3. A Giant Radio Flare from Cygnus X-3 with Associated Gamma-Ray Emission

    NASA Technical Reports Server (NTRS)

    Corbel, S.; Dubus, G.; Tomsick, J. A.; Szostek, A.; Corbet, R. H. D.; Miller-Jones, J. C. A.; Richards, J. L.; Pooley, G.; Trushkin, S.; Dubois, R.; Hill, A. B.; Kerr, M.; Max-Moerbeck, W.; Readhead, A. C. S.; Bodaghee, A.; Tudose, V.; Parent, D.; Wilms, J.; Pottschmidt, K.

    2012-01-01

    With frequent flaring activity of its relativistic jets, Cygnus X-3 (Cyg X-3) is one of the most active microquasars and is the only Galactic black hole candidate with confirmed high energy gamma-ray emission, thanks to detections by Fermi/LAT and AGILE. In 2011, Cyg X-3 was observed to transit to a soft X-ray state, which is known to be associated with high-energy gamma-ray emission. We present the results of a multiwavelength campaign covering a quenched state, when radio emission from Cyg X-3 is at its weakest and the X-ray spectrum is very soft. A giant (approx 20 Jy) optically thin radio flare marks the end of the quenched state, accompanied by rising non-thermal hard X-rays. Fermi/LAT observations (E greater than or equal 100 MeV) reveal renewed gamma-ray activity associated with this giant radio flare, suggesting a common origin for all non-thermal components. In addition, current observations unambiguously show that the gamma-ray emission is not exclusively related to the rare giant radio flares. A 3-week period of gamma-ray emission is also detected when Cyg X-3 was weakly flaring in radio, right before transition to the radio quenched state. No gamma rays are observed during the one-month long quenched state, when the radio flux is weakest. Our results suggest transitions into and out of the ultrasoft X-ray (radio quenched) state trigger gamma-ray emission, implying a connection to the accretion process, and also that the gamma-ray activity is related to the level of radio flux (and possibly shock formation), strengthening the connection to the relativistic jets.

  4. Systematic Search of the Nearest Stars for Exoplanetary Radio Emission: Preliminary results from LOFAR

    NASA Astrophysics Data System (ADS)

    Winterhalter, Daniel; Knapp, Mary

    2016-04-01

    Radio observations have been used as a tool to search for exoplanets since before the confirmed discovery of the first extrasolar planet. To date, neither targeted observations of known exoplanets nor surveys have produced definitive detections of exoplanetary radio emission. We present the framework for, and initial results from, a blind radio survey of the nearest star systems for exoplanetary radio emission. The very closest stars were chosen to minimize the dilution of potential radio signals by distance and thereby increase the probability of a detection. The goal of this survey is to obtain, at minimum, physically meaningful upper limits on radio emission from (or modulated by) substellar companions of the nearest stars. The target selection criteria for this survey are restricted to distance, observability for LOFAR and the VLA, and data quality metrics only. Stellar properties are not considered because preconceptions about the types of systems most likely to exhibit radio emission have not been observationally confirmed and may be incorrect. Two survey targets, GJ 411 and GJ 725A/B, have been observed with the LOFAR telescope LBA (30-75 MHz) system. A series of 4 2-hour integrations and 1 3-hour integration were made for each target of a period of approximately 2 weeks. Additional observations are underway with LOFAR as well as the VLA. Preliminary results from the first LOFAR observations are presented.

  5. Diffuse radio emission in the complex merging galaxy cluster Abell2069

    NASA Astrophysics Data System (ADS)

    Drabent, A.; Hoeft, M.; Pizzo, R. F.; Bonafede, A.; van Weeren, R. J.; Klein, U.

    2015-03-01

    Context. Galaxy clusters with signs of a recent merger in many cases show extended diffuse radio features. This emission originates from relativistic electrons that suffer synchrotron losses due to the intracluster magnetic field. The mechanisms of particle acceleration and the properties of the magnetic field are still poorly understood. Aims: We search for diffuse radio emission in galaxy clusters. Here, we study the complex galaxy cluster Abell 2069, for which X-ray observations indicate a recent merger. Methods: We investigate the cluster's radio continuum emission by deep Westerbork Synthesis Radio Telescope (WSRT) observations at 346 MHz and Giant Metrewave Radio Telescope (GMRT) observations at 322 MHz. Results: We find an extended diffuse radio feature roughly coinciding with the main component of the cluster. We classify this emission as a radio halo and estimate its lower limit flux density at 25 ± 9 mJy. Moreover, we find a second extended diffuse source located at the cluster's companion and estimate its flux density at 15 ± 2 mJy. We speculate that this is a small halo or a mini-halo. If true, this cluster is the first example of a double-halo in a single galaxy cluster.

  6. 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.

  7. The birthplace of planetary radio astronomy: The Seneca, Maryland observatory 50 years after Burke and Franklin's Jupiter radio emission discovery.

    NASA Astrophysics Data System (ADS)

    Garcia, L. N.; Thieman, J. R.; Higgins, C. A.

    2004-12-01

    Burke and Franklin's discovery of radio emissions from Jupiter in 1955 effectively marked the birth of the field of planetary radio astronomy. The discovery was made near Seneca, Maryland using the Department of Terrestrial Magnetism/Carnegie Institution of Washington's Mills Cross Array. Fifty years later there is very little evidence of this 96-acre X-shaped array of dipoles still in existence, nor evidence of any of the other antennas used at this site. The site, now known as the McKee Besher Wildlife Management Area, is owned by the State of Maryland Department of Natural Resources. Radio Jove, a NASA/GSFC education and public outreach project, will recognize the 50th anniversary of this discovery through an historic reenactment using their receiver and dual-dipole array system. Our search through the DTM/CIW archives, our visit to the site to look for evidence of this array, and other efforts at commemorating this anniversary will be described.

  8. RFID Transponders' RF Emissions in Aircraft Communication and Navigation Radio Bands

    NASA Technical Reports Server (NTRS)

    Nguyen, Truong X.; Ely, Jay J.; Koppen Sandra V.; Fersch, Mariatheresa S.

    2008-01-01

    Radiated emission data in aircraft communication and navigation bands are presented for several active radio frequency identification (RFID) tags. The individual tags are different in design, operation and transmitting frequencies. The process for measuring the tags emissions in a reverberation chamber is discussed. Measurement issues dealing with tag interrogation, low level measurement in the presence of strong transmissions, and tags low duty factors are discussed. The results show strong emissions, far exceeding aircraft emission limits and can be of potential interference risks.

  9. Shock-powered radio emission from V5589 Sagittarii (Nova Sgr 2012 #1)

    NASA Astrophysics Data System (ADS)

    Weston, Jennifer H. S.; Sokoloski, J. L.; Chomiuk, Laura; Linford, Justin D.; Nelson, Thomas; Mukai, Koji; Finzell, Tom; Mioduszewski, Amy; Rupen, Michael P.; Walter, Frederick M.

    2016-08-01

    Since the Fermi discovery of γ-rays from novae, one of the biggest questions in the field has been how novae generate such high-energy emission. Shocks must be a fundamental ingredient. Six months of radio observations of the 2012 Nova V5589 Sgr with the VLA and 15 weeks of X-ray observations with Swift/XRT show that the radio emission consisted of: (1) a shock-powered, non-thermal flare; and (2) weak thermal emission from 10-5 M⊙ of freely expanding, photoionized ejecta. Absorption features in the optical spectrum and the peak optical brightness suggest that V5589 Sgr lies 4 kpc away (3.2-4.6 kpc). The shock-powered flare dominated the radio light curve at low frequencies before day 100. The spectral evolution of the radio flare, its high radio brightness temperature, the presence of unusually hard (kTx > 33 keV) X-rays, and the ratio of radio to X-ray flux near radio maximum all support the conclusions that the flare was shock-powered and non-thermal. Unlike most other novae with strong shock-powered radio emission, V5589 Sgr is not embedded in the wind of a red-giant companion. Based on the similar inclinations and optical line profiles of V5589 Sgr and V959 Mon, we propose that shocks in V5589 Sgr formed from collisions between a slow flow with an equatorial density enhancement and a subsequent faster flow. We speculate that the relatively high speed and low mass of the ejecta led to the unusual radio emission from V5589 Sgr, and perhaps also to the non-detection of γ-rays.

  10. Shock-powered radio emission from V5589 Sagittarii (Nova Sgr 2012 #1)

    NASA Astrophysics Data System (ADS)

    Weston, Jennifer H. S.; Sokoloski, J. L.; Chomiuk, Laura; Linford, Justin D.; Nelson, Thomas; Mukai, Koji; Finzell, Tom; Mioduszewski, Amy; Rupen, Michael P.; Walter, Frederick M.

    2016-08-01

    Since the Fermi discovery of $\\gamma$-rays from novae, one of the biggest questions in the field has been how novae generate such high-energy emission. Shocks must be a fundamental ingredient. Six months of radio observations of the 2012 nova V5589 Sgr with the VLA and 15 weeks of X-ray observations with Swift/XRT show that the radio emission consisted of: 1) a shock-powered, non-thermal flare; and 2) weak thermal emission from $10^{-5}$ M$_\\odot$ of freely expanding, photoionized ejecta. Absorption features in the optical spectrum and the peak optical brightness suggest that V5589 Sgr lies 4 kpc away (3.2-4.6 kpc). The shock-powered flare dominated the radio light curve at low frequencies before day 100. The spectral evolution of the radio flare, its high radio brightness temperature, the presence of unusually hard ($kT_x > 33$ keV) X-rays, and the ratio of radio to X-ray flux near radio maximum all support the conclusions that the flare was shock-powered and non-thermal. Unlike most other novae with strong shock-powered radio emission, V5589 Sgr is not embedded in the wind of a red-giant companion. Based on the similar inclinations and optical line profiles of V5589 Sgr and V959 Mon, we propose that shocks in V5589 Sgr formed from collisions between a slow flow with an equatorial density enhancement and a subsequent faster flow. We speculate that the relatively high speed and low mass of the ejecta led to the unusual radio emission from V5589 Sgr, and perhaps also to the non-detection of $\\gamma$-rays.

  11. The radio emission from the ultraluminous far-infrared galaxy NGC 6240

    NASA Technical Reports Server (NTRS)

    Colbert, Edward J. M.; Wilson, Andrew S.; Bland-Hawthorn, Jonathan

    1994-01-01

    We present new radio observations of the 'prototypical' ultraluminous far-infrared galaxy NGC 6240, obtained using the Very Large Array (VLA) at lambda = 20 cm in B-configuration and at lambda = 3.6 cm in A-configuration. These data, along with those from four previous VLA observations, are used to perform a comprehensive study of the radio emission from NGC 6240. Approximately 70% (approximately 3 x 10(exp 23) W/Hz) of the total radio power at 20 cm originates from the nuclear region (approximately less than 1.5 kpc), of which half is emitted by two unresolved (R approximately less than 36 pc) cores and half by a diffuse component. The radio spectrum of the nuclear emission is relatively flat (alpha approximately equals 0.6; S(sub nu) proportional to nu(exp -alpha). The supernova rate required to power the diffuse component is consistent with that predicted by the stellar evolution models of Rieke et al. (1985). If the radio emission from the two compact cores is powered by supernova remnants, then either the remnants overlap and form hot bubbles in the cores, or they are very young (approximately less than 100 yr.) Nearly all of the remaining 30% of the total radio power comes from an 'armlike' region extending westward from the nuclear region. The western arm emission has a steep spectrum (alpha approximately equals 1.0), suggestive of aging effects from synchrotron or inverse-Compton losses, and is not correlated with starlight; we suggest that it is synchrotron emission from a shell of material driven by a galactic superwind. Inverse Compton scattering of far-infrared photons in the radio sources is expected to produce an X-ray flux of approximately 2 - 6 x 10(exp -14) ergs/s/sq cm in the 2 - 10 keV band. No significant radio emission is detected from or near the possible ultramassive 'dark core'.

  12. Highlighting the history of French radio astronomy. 1: Nordmann's attempt to observe solar radio emission in 1901

    NASA Astrophysics Data System (ADS)

    Débarbat, Suzanne; Lequeux, James; Orchiston, Wayne

    2007-03-01

    Soon after the discovery of radio waves by Hertz in 1886 the idea that the Sun must emit this radiation was suggested. A number of scientists from different nations then attempted to detect this emission, and one of these was the French astronomer, Charles Nordmann. This paper provides biographical Information an Nordmann before discussing his attempt to detect solar emisson in 1901 and the reasons he was unsuccessful.

  13. Solar Radio Emission as a Prediction Technique for Coronal Mass Ejections' registration

    NASA Astrophysics Data System (ADS)

    Sheiner, Olga; Fridman, Vladimir

    2016-07-01

    The concept of solar Coronal Mass Ejections (CMEs) as global phenomenon of solar activity caused by the global magnetohydrodynamic processes is considered commonly accepted. These processes occur in different ranges of emission, primarily in the optical and the microwave emission being generated near the surface of the sun from a total of several thousand kilometers. The usage of radio-astronomical data for CMEs prediction is convenient and promising. Actually, spectral measurements of solar radio emission cover all heights of solar atmosphere, sensitivity and accuracy of measurements make it possible to record even small energy changes. Registration of the radio emission is provided by virtually all-weather ground-based observations, and there is the relative cheapness to obtain the corresponding information due to a developed system of monitoring observations. On the large statistical material there are established regularities of the existence of sporadic radio emission at the initial stage of CMEs' formation and propagation in the lower layers of the solar atmosphere during the time interval from 2-3 days to 2 hours before registration of CMEs on coronagraph. In this report we present the prediction algorithm and scheme of short-term forecasting developed on the base of statistical analysis regularities of solar radio emission data prior to "isolated" solar Coronal Mass Ejections registered in 1998, 2003, 2009-2013.

  14. Is lightning a possible source of the radio emission on HAT-P-11b?

    NASA Astrophysics Data System (ADS)

    Hodosán, G.; Rimmer, P. B.; Helling, Ch.

    2016-09-01

    Lightning induced radio emission has been observed on Solar system planets. There have been many attempts to observe exoplanets in the radio wavelength, however, no unequivocal detection has been reported. Lecavelier des Etangs et al. carried out radio transit observations of the exoplanet HAT-P-11b, and suggested that a small part of the radio flux can be attributed to the planet. Here, we assume that this signal is real, and study if this radio emission could be caused by lightning with similar energetic properties like in the Solar system. We find that a lightning storm with 3.8 × 106 times larger flash densities than the Earth-storms with the largest lightning activity is needed to produce the observed signal from HAT-P-11b. The optical emission of such thunderstorm would be comparable to that of the host star. We show that HCN produced by lightning chemistry is observable 2-3 yr after the storm, which produces signatures in the L (3.0-4.0 μm) and N (7.5-14.5 μm) infrared bands. We conclude that it is unlikely that the observed radio signal was produced by lightning, however, future, combined radio and infrared observations may lead to lightning detection on planets outside the Solar system.

  15. COMPARATIVE ANALYSIS OF TWO FORMATION SCENARIOS OF BURSTY RADIO EMISSION FROM ULTRACOOL DWARFS

    SciTech Connect

    Kuznetsov, A. A.; Doyle, J. G.; Yu, S.; Hallinan, G.; Antonova, A.; Golden, A.

    2012-02-10

    Recently, a number of ultracool dwarfs have been found to produce periodic radio bursts with high brightness temperature and polarization degree; the emission properties are similar to the auroral radio emissions of the magnetized planets of the solar system. We simulate the dynamic spectra of radio emission from ultracool dwarfs. The emission is assumed to be generated due to the electron-cyclotron maser instability. We consider two source models: the emission caused by interaction with a satellite and the emission from a narrow sector of active longitudes; the stellar magnetic field is modeled by a tilted dipole. We have found that for the dwarf TVLM 513-46546, the model of the satellite-induced emission is inconsistent with observations. On the other hand, the model of emission from an active sector is able to reproduce qualitatively the main features of the radio light curves of this dwarf; the magnetic dipole seems to be highly tilted (by about 60 Degree-Sign ) with respect to the rotation axis.

  16. Long-duration Coherent Radio Emission from the dMe Star Proxima Centauri

    NASA Astrophysics Data System (ADS)

    Slee, O. B.; Willes, A. J.; Robinson, R. D.

    The Australia Telescope and Anglo-Australian Telescope were used in May 2000 to record the radio and optical emissions from the dMe flare star Proxima Centauri. Eight bright optical flares over a two-day interval resulted in no detectable excess short-term radio emission at 1.38 and 2.50GHz. However, a slowly declining 1.38GHz emission over the two-day interval was nearly 100% right circular polarised and was restricted to a relatively narrow bandwidth with total intensity (I) and circular polarisation (V) varying significantly over the 104MHz receiver bandwidth. These are the first observations to show that highly-polarised narrowband flare star emission can persist for several days. This signature is attributed to sources of coherent radio emission in the star's corona. Similarities with various solar radio emissions are discussed; however, it is not possible with the existing observations to distinguish between fundamental plasma emission and electron-cyclotron maser emission as the responsible mechanism.

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

    SciTech Connect

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

  18. 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. PMID:19257596

  19. A Study of Nonthermal X-Ray and Radio Emission from the O Star 9 Sgr

    NASA Technical Reports Server (NTRS)

    Waldron, Wayne L.; Corcoran, Michael F.; Drake, Stephen A.

    1999-01-01

    The observed X-ray and highly variable nonthermal radio emission from OB stars has eluded explanation for more than 18 years. The most favorable model of X-ray production in these stars (shocks) predicts both nonthermal radio and X-ray emission. The nonthermal X-ray emission should occur above 2 keV and the variability of this X-ray component should also be comparable to the observed radio variability. To test this scenario, we proposed an ASC/VLA monitoring program to observe the OB star, 9 Sgr, a well known nonthermal, variable radio source and a strong X-ray source. We requested 625 ks ASCA observations with a temporal spacing of approximately 4 days which corresponds to the time required for a density disturbance to propagate to the 6 cm radio free-free photosphere. The X-ray observations were coordinated with 5 multi-wavelength VLA observations. These observations represent the first systematic attempt to investigate the relationship between the X-ray and radio emission in OB stars.

  20. Multi-parameter Correlation of Jovian Radio Emissions with Solar Wind and Interplanetary Magnetic Field Data

    NASA Astrophysics Data System (ADS)

    MacDowall, R. J.; Golla, T.; Reiner, M. J.; Farrell, W. M.

    2015-12-01

    Variability of the numerous varieties of Jovian radio emission has been associated with aspects of solar wind (SW) and interplanetary magnetic field (IMF) parameters outside the magnetosphere. Here we demonstrate multiple-parameter correlations that relate each of several Jovian emissions, including bKOM and quasi-periodic bursts, to the SW and IMF impacting the Jovian magnetosphere. The data used are from the Ulysses spacecraft with radio data from the Unified Radio and Plasma wave (URAP) instrument, which provides high-quality remote radio observations of the Jovian emissions. The URAP observations are correlated with SW and IMF data from the relevant instruments on Ulysses, propagated to the nose of the Jovian magnetosphere with a sophisticated code. Because the aphelion of the Ulysses orbit was at the Jovian distance from the Sun, Ulysses spent ample time near Jupiter in 1991-1992 and 2003-2004, which are the intervals analyzed. Our results can be inverted such that radio observations by a Jovian orbiter, such as Cassini or Juno, are able to identify SW/IMF changes based on the behavior of the radio emissions.

  1. The Annular Gap: Gamma-Ray & Radio Emission of Pulsars

    NASA Astrophysics Data System (ADS)

    Qiao, G. J.; Du, Y. J.; Han, J. L.; Xu, R. X.

    2013-01-01

    Pulsars have been found more than 40 years. Observations from radio to gamma-rays present abundant information. However, the radiation mechanism is still an open question. It is found that the annular gap could be formed in the magnetosphere of pulsars (neutron stars or quark stars), which combines the advantages of the polar cap, slot gap and outer gap models. It is emphasized that observations of some radio pulsars, normal and millisecond gamma-ray pulsars (MSGPs) show that the annular gap would play a very important role. Here we show some observational and theoretical evidences about the annular gap. For example, bi-drifting sub-pulses; radio and gamma-ray millisecond pulsars and so on.

  2. Search for Radio Emission from HD80606b: a Highly Eccentric Exoplanet

    NASA Astrophysics Data System (ADS)

    Knapp, M.; Winterhalter, D.; Lazio, J.; Majid, W.; Kuiper, T.; Farrell, W. M.; Spitler, L.

    2014-12-01

    Exoplanetary radio emission is a potential goldmine of information about a wider sample of planetary interiors, dynamos, and magnetospheres than our solar system provides. To date, however, radio searches for exoplanetary radio emission have been unsuccessful likely because the observing frequencies are too high. Using the relatively new Low Frequency Array (LOFAR), we present analyses of observations of the highly eccentric Jovian exoplanet HD80606b during five epochs before and after the planet's periastron. All of the gas giants in the solar system, as well as the Earth, exhibit magnetospheric radio emission due to the electron cyclotron maser instability. The power of this emission is modulated by the solar wind intensity. HD80606b is in a highly eccentric (e=0.93) orbit with a 111 day period. As the planet passes from apastron (0.88 AU) to periastron (0.03 AU), it experiences widely varying stellar wind conditions which should lead to variable radio emission with the highest power corresponding to periastron passage. HD80606b has been observed previously with the VLA at 325 MHz and 1425 MHz by Lazio et. al (2010), but LOFAR's lower frequency range (30-75 MHz) and high sensitivity is better suited to Jovian-type radio emissions. The LOFAR observations were made 48 hours and 18 hours pre-periastron, plus 18 and 48 hours post-periastron to capture the predicted strongest emission, and near apastron to provide a baseline level. The data are analyzed for both time-dependent and frequency dependent emission at each of the five observation epochs. This work presents the ongoing analysis of the data. 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.

  3. Quantitative prediction of type II solar radio emission from the Sun to 1 AU

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    Coronal mass ejections (CMEs) are frequently associated with shocks and type II solar radio bursts. Despite involving fundamental plasma physics and being the archetype for collective radio emission from shocks, type II bursts have resisted detailed explanation for over 60 years. Between 29 November and 1 December 2013 the two widely separated spacecraft STEREO A and B observed a long lasting, intermittent, type II radio burst from ≈4 MHz to 30 kHz (harmonic), including an intensification when the CME-driven shock reached STEREO A. We demonstrate the first accurate and quantitative simulation of a type II burst from the high corona (near 11 solar radii) to 1 AU for this event with a combination of a data-driven three-dimensional magnetohydrodynamic simulation for the CME and plasma background and an analytic quantitative kinetic model for the radio emission.

  4. An Analysis of Interplanetary Solar Radio Emissions Associated with a Coronal Mass Ejection

    NASA Astrophysics Data System (ADS)

    Krupar, V.; Eastwood, J. P.; Kruparova, O.; Santolik, O.; Soucek, J.; Magdalenić, J.; Vourlidas, A.; Maksimovic, M.; Bonnin, X.; Bothmer, V.; Mrotzek, N.; Pluta, A.; Barnes, D.; Davies, J. A.; Martínez Oliveros, J. C.; Bale, S. D.

    2016-05-01

    Coronal mass ejections (CMEs) are large-scale eruptions of magnetized plasma that may cause severe geomagnetic storms if Earth directed. Here, we report a rare instance with comprehensive in situ and remote sensing observations of a CME combining white-light, radio, and plasma measurements from four different vantage points. For the first time, we have successfully applied a radio direction-finding technique to an interplanetary type II burst detected by two identical widely separated radio receivers. The derived locations of the type II and type III bursts are in general agreement with the white-light CME reconstruction. We find that the radio emission arises from the flanks of the CME and are most likely associated with the CME-driven shock. Our work demonstrates the complementarity between radio triangulation and 3D reconstruction techniques for space weather applications.

  5. Source location of the smooth high-frequency radio emissions from Uranus

    NASA Technical Reports Server (NTRS)

    Farrell, W. M.; Calvert, W.

    1989-01-01

    The source location of the smooth high-frequency radio emissions from Uranus has been determined. Specifically, by fitting the signal dropouts which occurred as Voyager traversed the hollow center of the emission pattern to a symmetrical cone centered on the source magnetic field direction at the cyclotron frequency, a southern-hemisphere (nightside) source was found at approximately 56 deg S, 219 deg W. The half-angle for the hollow portion of the emission pattern was found to be 13 deg.

  6. On Using Solar Radio Emission to Probe Interiors of Asteroids and Comets

    NASA Astrophysics Data System (ADS)

    Winebrenner, D. P.; Gary, D. E.; Sahr, J. D.; Asphaug, E. I.

    2015-12-01

    Asteroids, comets and other primitive solar system bodies are key sources of information on the early solar system, on volatiles and organics delivered to the terrestrial planets, and on processes of planetary formation now observed in operation around other stars. Whether asteroids (in various size classes) are rubble piles or monolithic, and whether any porosity or internal voids contain volatiles, are first-order questions for understanding the delivery of volatiles to the early Earth, and for assessing impact hazards. Information on bulk composition aids discrimination between types and origins of primitive bodies, .e.g., the degree of aqueous alteration and bound-water content of carbonaceous chondrite bodies, and the volatile mass fraction of comets. Radar and radio methods can provide direct information on bulk composition, micro- and macro-porosity, body-scale internal structure, and on whether voids in rocky materials are volatile- or vacuum-filled. Such methods therefore figure prominently in current missions to primitive bodies (e.g., CONSERT) and in a variety of proposed missions. Radio transmitters necessary for conventional methods, however, add considerably to spacecraft mass and power requirements. Moreover, at many wavelengths most useful for radio sounding, powerful radio emission from the Sun strongly interferes with conventional signals. Here we present initial results from an investigation of how solar radio emission could serve as a natural resource for probing interiors of primitive bodies, rather than as interference. We briefly review methods for using stochastic radio illumination (aka noise radar methods), and illustrate the characteristics of solar radio emission relevant to mission design (e.g., observed intervals between emission events of specified intensity for different points in the solar cycle). We then discuss methods for selecting and interpreting observations in terms of interior properties, for bodies is different size classes

  7. ON THE ORIGIN OF THE RADIO EMISSION OF Sw 1644+57

    SciTech Connect

    Barniol Duran, Rodolfo; Piran, Tsvi E-mail: tsvi.piran@mail.huji.ac.il

    2013-06-20

    We apply relativistic equipartition synchrotron arguments to the puzzling radio emission of the tidal disruption event candidate Sw 1644+57. We find that regardless of the details of the equipartition scenario considered, the energy required to produce the observed radio (i.e., energy in the magnetic field and radio emitting electrons) must increase by a factor of {approx}20 during the first 200 days. It then saturates. This energy increase cannot be alleviated by a varying geometry of the system. The radio data can be explained by the following. (1) An afterglow like emission of the X-ray emitting narrow relativistic jet. The additional energy can arise here from a slower moving material ejected in the first few days that gradually catches up with the slowing down blast wave. However, this requires at least {approx}4 Multiplication-Sign 10{sup 53} erg in the slower moving outflow. This is much more than the energy of the fast moving outflow that produced the early X-rays and it severely constrains the overall energy budget. (2) Alternatively, the radio may arise from a mildly relativistic and quasi-spherical outflow. Here, the energy available for radio emission increases with time, reaching at least {approx}10{sup 51} erg after 200 days. This scenario requires, however, a second separate X-ray emitting collimated relativistic component. Given these results, it is worthwhile to consider alternative models in which the energy of the magnetic field and/or of the radio emitting electrons increases with time without having a continuous energy supply to the blast wave. This can happen, for example, if the energy is injected initially mostly in one form (Poynting flux or baryonic) and it is gradually converted to the other form, leading to a strong time-varying deviation from equipartition. Another intriguing possibility is that a gradually decreasing inverse Compton cooling modifies the synchrotron emission and leads to an increase of the available energy in the radio

  8. Radio Monitoring of the Periodically Variable IR Source LRLL 54361: No Direct Correlation between the Radio and IR Emissions

    NASA Astrophysics Data System (ADS)

    Forbrich, Jan; Rodríguez, Luis F.; Palau, Aina; Zapata, Luis A.; Muzerolle, James; Gutermuth, Robert A.

    2015-11-01

    LRLL 54361 is an infrared source located in the star-forming region IC 348 SW. Remarkably, its infrared luminosity increases by a factor of 10 over roughly one week every 25.34 days. To understand the origin of these remarkable periodic variations, we obtained sensitive 3.3 cm JVLA radio continuum observations of LRLL 54361 and its surroundings in six different epochs: three of them during the IR-on state and three during the IR-off state. The radio source associated with LRLL 54361 remained steady and did not show a correlation with the IR variations. We suggest that the IR is tracing the results of fast (with a timescale of days) pulsed accretion from an unseen binary companion, while the radio traces an ionized outflow with an extent of ∼100 AU that smooths out the variability over a period of the order of a year. The average flux density measured in these 2014 observations, 27 ± 5 μJy, is about a factor of two less than that measured about 1.5 years before, 53 ± 11 μJy, suggesting that variability in the radio is present, but over larger timescales than in the IR. We discuss other sources in the field, in particular two infrared/X-ray stars that show rapidly varying gyrosynchrotron emission.

  9. Updated modeling of Io and non-Io Radio Auroral Emissions of Jupiter

    NASA Astrophysics Data System (ADS)

    Louis, C.; Lamy, L.; Zarka, P.; Cecconi, B.; Hess, S.

    2015-10-01

    The radio auroral emissions produced by the Jupiter's magnetosphere between a few kHz and 40MHz, the most intense of our Solar System, are known since half a century, but they still drive many questions, and their deepened study is one of the main aim of the JUNO missions (arrival in July 2016). Jovian auroral radio emissions are thought to be produced through the Cyclotron Maser Instability (CMI), from non-maxwellian weakly relativistic electrons gyrating along high-latitude magnetic fields lines (Zarka, 1998). These emissions divide in different spectral components, driven or not by the moon Io. The origin and the relationship between kilometric, hectometric and decametric non-Io emissions in particular remains poorly understood. To investigate these emissions, we simulated numerical dynamic spectra with the most recent version of the ExPRES code - Exoplanetary and Planetary Radio Emission Simulator, available at http://maser.obspm.fr - already used to successfully model Io decametric and Saturn's kilometric arcshaped emissions (Hess et al., 2008, Lamy et al., 2008) and predict exoplanetary radio emissions (Hess et al., 2011). Such simulations bring direct constraints on the locus of active magnetic field lines and on the nature of CMI-unstable electrons (Hess et al., submitted). We validated the new theoretical calculation of the beaming angle used by ExPRES, which now includes refraction at the source. We then built updated simulations of Io and non-Io emissions which were compared to the radio observations acquired by the Cassini spacecraft (Jupiter flyby in 2000) and the Nançay decameter array (routines observations of Jupiter).

  10. Nonthermal Radio Emission from Hot Star Winds: Its Origin and Physical Implications

    NASA Technical Reports Server (NTRS)

    Chen, Wan; White, Richard L.

    1994-01-01

    Nonthermal radio emission has been observed from some of the most luminous hot star winds. It is understood to be synchrotron radiation of the relativistic electrons in the winds. To understand how the electrons are accelerated to such high energies and to correctly explain the observed radio flux and spectra require an exhaustive investigation of all the relevant physical processes involved and possibly point to a complex wind structure. In this paper we discuss the logical path toward a comprehensive model of the nonthermal radio emission from hot star winds. Based on the available observational data and fundamental theoretical considerations, we found that the only physically viable and self-consistent scenario is: the nonthermal radio emission is synchrotron radiation of relativistic electrons (left right harpoon) the electrons are accelerated by shocks via the first-order Fermi mechanism (left right harpoon) the acceleration has to be in situ in the radio emitting region (left right harpoon) the shocks formed at the base of the winds have to propagate to beyond the radio photosphere.

  11. Nonthermal radio emission from hot star winds: Its origin and physical implications

    NASA Technical Reports Server (NTRS)

    Chen, Wan; White, Richard L.

    1994-01-01

    Nonthermal radio emission has been observed from some of the most luminous hot star winds. It is understood to be synchrotron radiation of the relativistic electrons in the winds. To understand how the electrons are accelerated to such high energies and to correctly explain the observed radio flux and spectra require an exhaustive investigation of all the relevant physical processes involved and possibly point to a complex wind structure. In this paper we discuss the logical path toward a comprehensive model of the nonthermal radio emission from hot star winds. Based on the available observational data and fundamental theoretical considerations, we found that the only physically viable and self-consistent scenario is: the nonthermal radio emission is synchrotron radiation of relativistic electrons the electrons are accelerated by shocks via the first-order Fermi mechanism the acceleration has to be in situ in the radio emitting region and the shocks formed at the base of the winds have to propagate to beyond the radio photosphere.

  12. Sampling Studies Of Quasars, Radio-loud Galaxies, & Radio-quiet Galaxies -- Searching For The Cause Of Radio Emission

    NASA Astrophysics Data System (ADS)

    Coldwell, G.; Salois, Amee; Soechting, I.; Smith, M.

    2011-01-01

    Comparing the environments of Radio-Loud Galaxies, Radio-Quiet Galaxies, and Quasars offers an opportunity to study the evolution of these objects. Our samples have been carefully chosen from Data Release 7 of the Sloan Digital Sky Survey, which also includes samples studied in the FIRST survey, and have been cut to determine the best possible results. Our study includes three samples. The Quasar sample currently contains 69 objects, the Radio-Loud Galaxy (RLG) sample has 1,335 objects, and the Radio-Quiet Galaxy (RQG) sample contains 2,436 objects (any updates will be given at the meeting). A number of trims were made to produce (smaller) samples with characteristics suited for precise results. By comparing the environments of these three samples we will be able to see any similarities or differences between them. If similarities are detected it suggests that the central object has evolved according to 'nature' - in an isolated manner with little environmental feedback, which may or may not have an effect on its evolution, as supposed by Coldwell et al. (2009). If differences are detected it suggests that the central object has evolved according to `nurture’ and that the environment may have played an important role in the development of their properties. We employ similar procedures used by Coldwell et al. (2009) in their study of blue and red AGNs. Upon the completion of an accurate sample, future work will be pursued studying a number of properties of the environments including studies of: the stellar masses, star formation rates, sersic morphologies, as well as densities and ages of the environments.

  13. Control of Jupiter's Radio Emission and Aurorae by the Solar Wind

    NASA Technical Reports Server (NTRS)

    Gurnett, D. A.; Kurth, W. S.; Hospodarsky, G. B.; Persoon, A. M.; Zarka, P.; Lecacheux, A.; Bolton, S. J.; Desch, . D.; Farrell, W. W.; Kaiser, M. L.

    2002-01-01

    Radio emissions from Jupiter provided the first evidence that this giant planet has a strong magnetic field and a large magnetosphere. Jupiter also has polar aurorae, which are similar in many respects to Earth's aurorae. The radio emissions are believed to be generated along the high-latitude magnetic field lines by the same electrons that produce the aurorae, and both the radio emission in the hectometric frequency range and the aurorae vary considerably. The origin of the variability, however, has been poorly understood. Here we report simultaneous observations using the Cassini and Galileo spacecraft of hectometric radio emissions and extreme ultraviolet auroral emissions from Jupiter. Our results show that both of these emissions are triggered by interplanetary shocks propagating outward from the Sun. When such a shock arrives at Jupiter, it seems to cause a major compression and reconfiguration of the magnetosphere, which produces strong electric fields and therefore electron acceleration along the auroral field lines, similar to the processes that occur during geomagnetic storms at the Earth.

  14. Simulation of radio emission from air showers in atmospheric electric fields

    SciTech Connect

    Buitink, S.; Huege, T.; Falcke, H; Kuijpers, J.

    2010-02-25

    We study the effect of atmospheric electric fields on the radio pulse emitted by cos- mic ray air showers. Under fair weather conditions the dominant part of the radio emission is driven by the geomagnetic field. When the shower charges are accelerated and deflected in an electric field additional radiation is emitted. We simulate this effect with the Monte Carlo code REAS2, using CORSIKA-simulated showers as input. In both codes a routine has been implemented that treats the effect of the electric field on the shower particles. We find that the radio pulse is significantly altered in background fields of the order of ~100 V/cm and higher. Practically, this means that air showers passing through thunderstorms emit radio pulses that are not a reliable measure for the shower energy. Under other weather circumstances significant electric field effects are expected to occur rarely, but nimbostratus clouds can harbor fields that are large enough. In general, the contribution of the electric field to the radio pulse has polarization properties that are different from the geomagnetic pulse. In order to filter out radio pulses that have been affected by electric field effects, radio air shower experiments should keep weatherinformation and perform full polarization measurements of the radio signal.

  15. Bright radio emission from an ultraluminous stellar-mass microquasar in M 31.

    PubMed

    Middleton, Matthew J; Miller-Jones, James C A; Markoff, Sera; Fender, Rob; Henze, Martin; Hurley-Walker, Natasha; Scaife, Anna M M; Roberts, Timothy P; Walton, Dominic; Carpenter, John; Macquart, Jean-Pierre; Bower, Geoffrey C; Gurwell, Mark; Pietsch, Wolfgang; Haberl, Frank; Harris, Jonathan; Daniel, Michael; Miah, Junayd; Done, Chris; Morgan, John S; Dickinson, Hugh; Charles, Phil; Burwitz, Vadim; Della Valle, Massimo; Freyberg, Michael; Greiner, Jochen; Hernanz, Margarita; Hartmann, Dieter H; Hatzidimitriou, Despina; Riffeser, Arno; Sala, Gloria; Seitz, Stella; Reig, Pablo; Rau, Arne; Orio, Marina; Titterington, David; Grainge, Keith

    2013-01-10

    A subset of ultraluminous X-ray sources (those with luminosities of less than 10(40) erg s(-1); ref. 1) are thought to be powered by the accretion of gas onto black holes with masses of ∼5-20M cicled dot, probably by means of an accretion disk. The X-ray and radio emission are coupled in such Galactic sources; the radio emission originates in a relativistic jet thought to be launched from the innermost regions near the black hole, with the most powerful emission occurring when the rate of infalling matter approaches a theoretical maximum (the Eddington limit). Only four such maximal sources are known in the Milky Way, and the absorption of soft X-rays in the interstellar medium hinders the determination of the causal sequence of events that leads to the ejection of the jet. Here we report radio and X-ray observations of a bright new X-ray source in the nearby galaxy M 31, whose peak luminosity exceeded 10(39) erg s(-1). The radio luminosity is extremely high and shows variability on a timescale of tens of minutes, arguing that the source is highly compact and powered by accretion close to the Eddington limit onto a black hole of stellar mass. Continued radio and X-ray monitoring of such sources should reveal the causal relationship between the accretion flow and the powerful jet emission. PMID:23235823

  16. Time-scales of close-in exoplanet radio emission variability

    NASA Astrophysics Data System (ADS)

    See, V.; Jardine, M.; Fares, R.; Donati, J.-F.; Moutou, C.

    2015-07-01

    We investigate the variability of exoplanetary radio emission using stellar magnetic maps and 3D field extrapolation techniques. We use a sample of hot Jupiter hosting stars, focusing on the HD 179949, HD 189733 and τ Boo systems. Our results indicate two time-scales over which radio emission variability may occur at magnetized hot Jupiters. The first is the synodic period of the star-planet system. The origin of variability on this time-scale is the relative motion between the planet and the interplanetary plasma that is corotating with the host star. The second time-scale is the length of the magnetic cycle. Variability on this time-scale is caused by evolution of the stellar field. At these systems, the magnitude of planetary radio emission is anticorrelated with the angular separation between the subplanetary point and the nearest magnetic pole. For the special case of τ Boo b, whose orbital period is tidally locked to the rotation period of its host star, variability only occurs on the time-scale of the magnetic cycle. The lack of radio variability on the synodic period at τ Boo b is not predicted by previous radio emission models, which do not account for the co-rotation of the interplanetary plasma at small distances from the star.

  17. Gamma-ray Burst Reverse Shock Emission in Early Radio Afterglows

    NASA Astrophysics Data System (ADS)

    Resmi, Lekshmi; Zhang, Bing

    2016-07-01

    Reverse shock (RS) emission from gamma-ray bursts is an important tool in investigating the nature of the ejecta from the central engine. If the magnetization of the ejecta is not high enough to suppress the RS, a strong RS emission component, usually peaking in the optical/IR band early on, would provide an important contribution to early afterglow light curve. In the radio band, synchrotron self-absorption may suppress early RS emission and also delay the RS peak time. In this paper, we calculate the self-absorbed RS emission in the radio band under different dynamical conditions. In particular, we stress that the RS radio emission is subject to self-absorption in both RSs and forward shocks (FSs). We calculate the ratio between the RS to FS flux at the RS peak time for different frequencies, which is a measure of the detectability of the RS emission component. We then constrain the range of physical parameters for a detectable RS, in particular the role of magnetization. We notice that unlike optical RS emission which is enhanced by moderate magnetization, moderately magnetized ejecta do not necessarily produce a brighter radio RS due to the self-absorption effect. For typical parameters, the RS emission component would not be detectable below 1 GHz unless the medium density is very low (e.g., n < 10‑3 cm‑3 for the interstellar medium and A * < 5 × 10‑4 for wind). These predictions can be tested using the afterglow observations from current and upcoming radio facilities such as the Karl G. Jansky Very Large Array, the Low-Frequency Array, the Five Hundred Meter Aperture Spherical Telescope, and the Square Kilometer Array.

  18. Radio-continuum Emission from Magellanic Clouds Planetary Nebulae

    NASA Astrophysics Data System (ADS)

    Filipovic, Miroslav

    2015-08-01

    Comparison of recent Australia Telescope Compact Array (ATCA) / Parkes mosaic surveys of the Magellanic Clouds (MCs) with positions of known planetary nebulae (PNe) have revealed a total of about 50 radio counterparts. Six (15) Small Magellanic Cloud (SMC) candidates were found in 5~GHz surveys, while ~35 were found in the Large Magellanic Cloud (LMC). Followup high resolution ATCA observations at 6 and 3 cm (4" and 2" beams, respectively) reveal that these sources are located within 1" of their optical counterparts. They are extended with higher than expected flux densities. Complimentary optical PNe spectra have typical electron temperatures and densities. Estimates of nebular ionized mass, based on these elevated radio flux densities, suggest they may be the result of significant circumstellar envelopes. These envelopes may have been formed from winds ejected from high mass (up to 8 solar) progenitor stars.

  19. Radio emission evolution of nonstationary sources in the Hedgehog model

    NASA Technical Reports Server (NTRS)

    Kovalev, Y. A.; Mikhaylutsa, V. P.

    1980-01-01

    Correlations are obtained for numerical calculation of flux F sub v and polarized radiation intensity of a cloud of arbitrary geometry, consisting of ultrarelativistic electrons that dissipate in a radial magnetic field of the nucleus at a random angle to the observer. It is possible that some of the variable extragalactic objects that were previously described by the Shklovskiy model are young formations in the examined model. Radio astronomical observations would permit a determination of their distance, age, and lifetime.

  20. Searching towards the Galactic Centre region for pulsed radio emission

    NASA Astrophysics Data System (ADS)

    Toomey, Lawrence; Johnston, Simon; Hobbs, George; Bhat, Ramesh; Shannon, Ryan

    2014-10-01

    A search of archival Parkes survey data has uncovered a source similar to that of a radio pulsar, however the detection DM indicates that it may be either the closest pulsar ever discovered, or simply a case of mistaken identity and is in fact an RFI event that closely mimics that of a pulsar signal. We would like to propose a grid search of the location of this source, at 3 available frequency bands, in order to determine its nature.

  1. Variable Radio Emission from Nova V5588 Sgr

    NASA Astrophysics Data System (ADS)

    Krauss, M. I.; Chomiuk, L.; Sokoloski, J. L.; Rupen, M. P.; Mioduszewski, A. J.; Roy, N.; O'Brien, T. J.; Bode, M. F.; Eyres, S. P. S.

    2011-08-01

    The EVLA Nova Team reports additional radio flux measurements of the classical nova V5588 Sgr (IAUC #9203, CBET #2707) which indicate significant variability. Observations taken 66 days after the initial discovery of this nova yield non-detections at 5.9 and 33.1 GHz; the derived upper limits are significantly lower than our previously reported detections on day 48 (ATel #3397).

  2. Searches for gamma ray emission from radio pulsars

    NASA Technical Reports Server (NTRS)

    Thompson, D. J.; Bertsch, D. L.; Hartman, R. C.; Hunter, S. D.

    1983-01-01

    Searches were made for pulsed high energy (E 35 MeV) gamma radiation from 43 pulsars using the SAS-2 data base and radio parameters. No positive results were found, and the upper limits are consistent with the concept that gamma ray production efficiency increases with increasing apparent age. Two limits suggest that efficiency cannot be a simple function of apparent age beyond 10,000,000 years.

  3. Detection of Nonthermal Radio Emission from a Polar coronal mass ejection

    NASA Astrophysics Data System (ADS)

    Gopalswamy, Nat; Reiner, Mike J.; Makela, Pertti; Yashiro, Seiji; Akiyama, Sachiko

    2016-07-01

    High-latitude coronal mass ejections from the polar crown region are generally of low energy and hence thought to be not responsible for driving shocks. However, the eruption of such CMEs are associated with weak post eruption arcades suggesting that particle acceleration does happen in the reconnection region beneath the erupting filaments. An unusually fast CME erupted from the southern polar crown on 1999 June 14 observed by the Large Angle and Spectrometric Coronagraph (LASCO) on board the Solar and Heliospheric Observatory (SOHO) mission. The post eruption arcade was observed by the Soft X-ray Telescope on board the Yohkoh mission and the Extreme-ultraviolet imaging Telescope (EIT) on board SOHO. A diffuse radio emission was observed below 1 MHz by the Radio and Plasma Wave experiment (WAVES) on board the Wind spacecraft. The good temporal association between the radio burst and the CME suggests that the CME must be the source of energy for the radio emission. The drift rate of the radio burst was much smaller than that of a typical interplanetary type II burst. We suggest that the radio burst is produced by a flank of the CME-driven shock passing through a streamer located close to the east limb of the Sun. Such an interaction is likely to have caused the slow drift of the burst because the shock flank passes roughly parallel to the solar surface in the flank region. The enhanced density in the streamer makes the local Alfven speed lower, making the shock sufficiently strong to accelerate a few keV electrons that lead to the radio emission. The diffuse feature also contains a series of spikes, which suggest possible escape of nonthermal electrons along open field lines. We use the radio direction finding to confirm the results. This result has important implications for particle acceleration by shock flanks, where the geometry is expected to be quasi-perpendicular.

  4. COMPLEX DIFFUSE RADIO EMISSION IN THE MERGING PLANCK ESZ CLUSTER A3411

    SciTech Connect

    Van Weeren, R. J.; Fogarty, K.; Jones, C.; Forman, W. R.; Kraft, R. P.; Murray, S. S.; Clarke, T. E.; Brueggen, M.; Lal, D. V.; Roettgering, H. J. A.

    2013-06-01

    We present Very Large Array (VLA) radio and Chandra X-ray observations of the merging galaxy cluster A3411. For the cluster, we find an overall temperature of 6.4{sup +0.6}{sub -1.0} keV and an X-ray luminosity of 2.8 {+-} 0.1 Multiplication-Sign 10{sup 44} erg s{sup -1} between 0.5 and 2.0 keV. The Chandra observation reveals the cluster to be undergoing a merger event. The VLA observations show the presence of large-scale diffuse emission in the central region of the cluster, which we classify as a 0.9 Mpc size radio halo. In addition, a complex region of diffuse, polarized emission is found in the southeastern outskirts of the cluster along the projected merger axis of the system. We classify this region of diffuse emission as a radio relic. The total extent of this radio relic is 1.9 Mpc. For the combined emission in the cluster region, we find a radio spectral index of -1.0 {+-} 0.1 between 74 MHz and 1.4 GHz. The morphology of the radio relic is peculiar, as the relic is broken up into five fragments. This suggests that the shock responsible for the relic has been broken up due to interaction with a large-scale galaxy filament connected to the cluster or other substructures in the intracluster medium. Alternatively, the complex morphology reflects the presence of electrons in fossil radio bubbles that are re-accelerated by a shock.

  5. The ATLAS3D Project - XXXI. Nuclear radio emission in nearby early-type galaxies

    NASA Astrophysics Data System (ADS)

    Nyland, Kristina; Young, Lisa M.; Wrobel, Joan M.; Sarzi, Marc; Morganti, Raffaella; Alatalo, Katherine; Blitz, Leo; Bournaud, Frédéric; Bureau, Martin; Cappellari, Michele; Crocker, Alison F.; Davies, Roger L.; Davis, Timothy A.; de Zeeuw, P. T.; Duc, Pierre-Alain; Emsellem, Eric; Khochfar, Sadegh; Krajnović, Davor; Kuntschner, Harald; McDermid, Richard M.; Naab, Thorsten; Oosterloo, Tom; Scott, Nicholas; Serra, Paolo; Weijmans, Anne-Marie

    2016-05-01

    We present the results of a high-resolution, 5 GHz, Karl G. Jansky Very Large Array study of the nuclear radio emission in a representative subset of the ATLAS3D survey of early-type galaxies (ETGs). We find that 51 ± 4 per cent of the ETGs in our sample contain nuclear radio emission with luminosities as low as 1018 W Hz-1. Most of the nuclear radio sources have compact (≲25-110 pc) morphologies, although ˜10 per cent display multicomponent core+jet or extended jet/lobe structures. Based on the radio continuum properties, as well as optical emission line diagnostics and the nuclear X-ray properties, we conclude that the majority of the central 5 GHz sources detected in the ATLAS3D galaxies are associated with the presence of an active galactic nucleus (AGN). However, even at subarcsecond spatial resolution, the nuclear radio emission in some cases appears to arise from low-level nuclear star formation rather than an AGN, particularly when molecular gas and a young central stellar population is present. This is in contrast to popular assumptions in the literature that the presence of a compact, unresolved, nuclear radio continuum source universally signifies the presence of an AGN. Additionally, we examine the relationships between the 5 GHz luminosity and various galaxy properties including the molecular gas mass and - for the first time - the global kinematic state. We discuss implications for the growth, triggering, and fuelling of radio AGNs, as well as AGN-driven feedback in the continued evolution of nearby ETGs.

  6. The Connection between the Radio Jet and the Gamma-ray Emission in the Radio Galaxy 3C 120

    NASA Astrophysics Data System (ADS)

    Casadio, Carolina; Gómez, José L.; Grandi, Paola; Jorstad, Svetlana G.; Marscher, Alan P.; Lister, Matthew L.; Kovalev, Yuri Y.; Savolainen, Tuomas; Pushkarev, Alexander B.

    2015-08-01

    We present the analysis of the radio jet evolution of the radio galaxy 3C 120 during a period of prolonged γ-ray activity detected by the Fermi satellite between 2012 December and 2014 October. We find a clear connection between the γ-ray and radio emission, such that every period of γ-ray activity is accompanied by the flaring of the millimeter very long baseline interferometry (VLBI) core and subsequent ejection of a new superluminal component. However, not all ejections of components are associated with γ-ray events detectable by Fermi. Clear γ-ray detections are obtained only when components are moving in a direction closer to our line of sight. This suggests that the observed γ-ray emission depends not only on the interaction of moving components with the millimeter VLBI core, but also on their orientation with respect to the observer. Timing of the γ-ray detections and ejection of superluminal components locate the γ-ray production to within ∼0.13 pc from the millimeter VLBI core, which was previously estimated to lie about 0.24 pc from the central black hole. This corresponds to about twice the estimated extension of the broad line region, limiting the external photon field and therefore suggesting synchrotron self Compton as the most probable mechanism for the production of the γ-ray emission. Alternatively, the interaction of components with the jet sheath can provide the necessary photon field to produced the observed γ-rays by Compton scattering.

  7. Radio imaging of synchrotron emission associated with a CME on the 14th of August 2010

    NASA Astrophysics Data System (ADS)

    Bain, H. M.; Krucker, S.; Raftery, C. L.; Saint-Hilaire, P.

    2012-12-01

    Radio observations can be used to identify sources of electron acceleration within flares and CMEs. In a small number of events, radio imaging has revealed the presence of synchrotron emission from nonthermal electrons in the expanding loops of the CME (Bastian et al. (2001), Maia et al. (2007) and Démoulin et al. (2012)). Events in which the synchrotron emission is sufficiently bright to be identified in the presence of plasma emission from radio bursts, which are prevalent at meter wavelengths, are infrequent. Using radio images from the Nançay Radioheliograph (NRH) we present observations of synchrotron emission associated with a CME which occurred on the 14th of August 2010. Using context observations from the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory, the SWAP instrument onboard Proba2, the LASCO coronograph onboard SOHO and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), we follow the propagation of the CME out to 2-3 solar radii and characterize the associated electron distribution. We find that the synchrotron emission is cospatial with the CME core.

  8. DETECTION OF RADIO EMISSION FROM THE HYPERACTIVE L DWARF 2MASS J13153094-2649513AB

    SciTech Connect

    Burgasser, Adam J.; Melis, Carl; Zauderer, B. Ashley; Berger, Edo

    2013-01-01

    We report the detection of radio emission from the unusually active L5e + T7 binary 2MASS J13153094-2649513AB made with the Australian Telescope Compact Array. Observations at 5.5 GHz reveal an unresolved source with a continuum flux of 370 {+-} 50 {mu}Jy, corresponding to a radio luminosity of L{sub rad} = {nu}L{sub {nu}} = (9 {+-} 3) Multiplication-Sign 10{sup 23} erg s{sup -1} and log{sub 10} L{sub rad}/L{sub bol} = -5.44 {+-} 0.22. No detection is made at 9.0 GHz to a 5{sigma} limit of 290 {mu}Jy, consistent with a power-law spectrum S{sub {nu}}{proportional_to}{nu}{sup -{alpha}} with {alpha} {approx}> 0.5. The emission is quiescent, with no evidence of variability or bursts over three hours of observation, and no measurable polarization (V/I < 34%). 2MASS J1315-2649AB is one of the most radio-luminous ultracool dwarfs detected in quiescent emission to date, comparable in strength to other cool sources detected in outburst. Its detection indicates no decline in radio flux through the mid-L dwarfs. It is unique among L dwarfs in having strong and persistent H{alpha} and radio emission, indicating the coexistence of a cool, neutral photosphere (low electron density) and a highly active chromosphere (high electron density and active heating). These traits, coupled with the system's mature age and substellar secondary, make 2MASS J1315-2649AB an important test for proposed radio emission mechanisms in ultracool dwarfs.

  9. Beamed and Unbeamed X-Ray Emission in FR1 Radio Galaxies

    NASA Technical Reports Server (NTRS)

    Worrall, Diana M.

    2000-01-01

    The research exploited ROSAT's sensitivity, together with its spatial and spectral resolution, to separate X-ray emission components in the sources. Prior to ROSAT, the dominant X-ray emission mechanism in radio galaxies as a class was unclear, with correlations between the X-ray and radio emission used on one hand to argue for a nuclear origin for the X-rays, and on the other hand for a thermal origin. Our observations (normally between 10 and 25 ks in length) routinely detected the target sources, and demonstrated that both resolved (thermal) and unresolved X-ray emission are typically present. Highlights of our work included two of the first detections of high-power radio galaxies at high redshift, 3C 280 and 3C 220.1. When combined with the work of two other groups, we find that of the 38 radio galaxies at z > 0.6 in the 3CRR sample, 12 were observed in ROSAT pointed observations and 9 were detected with the four most significant detections exhibiting source extent, including 3C 280 and 3C 220.1. Moreover, we discovered extended emission around five 3CRR quasars at redshift greater than about 0.4, one of which is at z > 0.6. Unification predicts that the X-ray environments of powerful radio galaxies and quasars should be similar, and our results show that powerful radio sources are finding some of the highest-redshift X-ray clusters known to date, pointing to deep gravitational potential wells early in the Universe.

  10. Beamed and Unbeamed X-ray Emission in FR1 Radio Galaxies

    NASA Technical Reports Server (NTRS)

    Worrall, Diana M.

    1997-01-01

    There is good evidence for X-ray emission associated with AGN jets which are relativistically boosted towards the observer. But to what jet radius does such X-ray emission persist? To attempt to answer this question one can look at radio galaxies; their cores are sufficiently X-ray faint that any unbeamed X-ray emission in the vicinity of the central engine must be obscured. The jets of such sources are at unfavourable angles for relativistic boosting, and so their relatively weak X-ray emission must be carefully separated from the plateau of resolved X-ray emission from a hot interstellar, intragroup, or intracluster medium on which they are expected to sit. This paper presents results arguing that jet X-ray emission is generally detected in radio galaxies, even those of low intrinsic power without hot spots. The levels of emission suggest an extrapolated radio to soft X-ray spectral index, alpha(sub tao x) of about 0.85 at parsec to perhaps kiloparsec distances from the cores.