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  • 1
    Electronic Resource
    Electronic Resource
    RADIO EMISSION FROM SOLAR FLARES (1998)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Astronomy and Astrophysics 36 (1998), S. 131-188 
    Details
    ISSN: 0066-4146
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Physics
    Notes: Abstract Radio emission from solar flares offers a number of unique diagnostic tools to address long-standing questions about energy release, plasma heating, particle acceleration, and particle transport in magnetized plasmas. At millimeter and centimeter wavelengths, incoherent gyrosynchrotron emission from electrons with energies of tens of kilo electron volts to several mega electron volts plays a dominant role. These electrons carry a significant fraction of the energy released during the impulsive phase of flares. At decimeter and meter wavelengths, coherent plasma radiation can play a dominant role. Particularly important are type III and type III-like radio bursts, which are due to upward- and downward-directed beams of nonthermal electrons, presumed to originate in the energy release site. With the launch of Yohkoh and the Compton Gamma-Ray Observatory, the relationship between radio emission and energetic photon emissions has been clarified. In this review, recent progress on our Dunderstanding of radio emission from impulsive flares and its relation to X-ray emission is discussed, as well as energy release in flare-like phenomena (microflares, nanoflares) and their bearing on coronal heating.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.astro.36.1.131
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  • 2
    Electronic Resource
    Electronic Resource
    Ultra-relativistic electrons in Jupiter's radiation belts (2002)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 415 (2002), S. 987-991 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Ground-based observations have shown that Jupiter is a two-component source of microwave radio emission: thermal atmospheric emission and synchrotron emission from energetic electrons spiralling in Jupiter's magnetic field. Later in situ measurements confirmed the existence of Jupiter's ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/415987a
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  • 3
    Electronic Resource
    Electronic Resource
    First dynamic spectra of stellar microwave flares (1987)
    [s.l.] : Nature Publishing Group
    Nature 326 (1987), S. 678-680 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] We used the Very Large Array (VLA) on 28 June 1986 in 16 channel spectral line mode centred at 1,415 MHz. The 50-MHz bandwidth was divided into 15 channels of 3.125-MHz width; the sixteenth channel was reserved for recording the integral flux over the inner 37.5 MHz of the bandwidth. The array was ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/326678a0
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  • 4
    Electronic Resource
    Electronic Resource
    First millimetric detections of AE Aquarii (1994)
    Springer
    Space science reviews 68 (1994), S. 291-292 
    Details
    ISSN: 1572-9672
    Keywords: accretion, accretion disks ; binaries ; novae, cataclysmic variables ; radio continuum: stars ; stars: individual (AE Aquarii)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report the first millimetric detections of the magnetic cataclysmic variable AE Aquarii, accompanied by contemporaneous microwave observations. These data show that the time-averaged spectrum is well fit by a power-law which extends to mm wavelengths. We suggest that the spectrum is consistent with that expected from a superposition of flare-like events.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00749154
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  • 5
    Electronic Resource
    Electronic Resource
    Joint radio and soft x-ray imaging of an ‘anemone’ active region (1996)
    Springer
    Solar physics 163 (1996), S. 99-120 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Very Large Array and the Soft X-ray Telescope (SXT) aboard the Yohkoh satellite jointly observed the rapid growth and decay of a so-called ‘anemone’ active region on 3–6 April, 1992 (AR 7124). The VLA obtained maps of the AR 7124 at 1.5, 4.7, and 8.4 GHz. In general, discrete coronal loop systems are rarely resolved at 1.5 GHz wavelengths because of limited brightness contrast due to optical depth effects and wave scattering. Due to its unusual anemone-like morphology, however, several discrete loops or loop systems are resolved by both the VLA at 1.5 GHz and the SXT in AR 7124. Using extrapolations of the photospheric field and the radio observations at 4.7 and 8.4 GHz, we find that the microwave emission is the result of gyroresonance emission from a hot, rarefied plasma, at the second and/or third harmonic. The decimetric source is complex -1.5 GHz emission from the leading part of AR 7124 is due to free-free emission, while that in the trailing part of the active region is dominated by gyroresonance emission. We also examine an interesting case of a discrete radio loop with no soft X-ray (SXR) emission adjacent to a hot SXR loop. This observation clearly shows the multithermal nature of the solar corona.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00165459
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  • 6
    Electronic Resource
    Electronic Resource
    Radio observations of the M8.1 solar flare of 23 June, 1988: Evidence for energy transport by thermal processes (1992)
    Springer
    Solar physics 139 (1992), S. 357-385 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Very Large Array (VLA) and the frequency agile interferometer at the Owens Valley Radio Observatory (OVRO) were used to observe the M8.1 flare of 23 June, 1988. The VLA obtained images prior to and during the flare at 333 MHz, and at 1.5 and 4.7 GHz. The frequency agile interferometer at Owens Valley obtained interferometer amplitude and total power spectra of the flare at 45 frequencies between 1 and 18 GHz. The observations were supplemented by radiometer measurements made by the USAF RSTN network site at Palehua, HI, by GOES soft X-ray observations, by USAF SOON Hα filtergrams, and by a KPNO photospheric magnetogram. The radio data reveal a wide variety of phenomena, including: (i) a multiply impulsive microwave burst that is essentially thermal in character; (ii) stationary discrete components at 1.5 GHz, associated temporally and spatially with distant brightenings in Ha; (iii) a dynamical component at 1.5 GHz associated with hot plasma moving subsonically into the corona; (iv) the appearance of intense, short-lived, decimetric burst activity near the lead sunspot in the active region at 1.5 GHz, indicative of a high degree of inhomogeneity in the source. The unusually complete radio coverage allows us to investigate the transport of energy from the initial site to sites of distant Hα brightenings. The transport of energy appears to be most consistent with slow, thermal processes, rather than rapid transport by nonthermal electron beams.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00159159
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  • 7
    Electronic Resource
    Electronic Resource
    Stellar dynamic spectroscopy (1982)
    Springer
    Solar physics 113 (1982), S. 289-290 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The dynamic spectrum, a three dimensional record of the radio intensity as a function both of time and frequency, has long been used as a probe of plasma processes in the solar corona. Beginning with the work of Wild and McCready (1950) dynamic spectroscopy has been used to distinguish between the multitude of radio wave emitting phenomena which occur in the solar corona and to infer the physical mechanisms responsible. Stellar dynamic spectroscopy has always been a tantalizing prospect. The vast body of experience with solar dynamic spectroscopy would prove invaluable in interpreting stellar dynamic spectra. Further, the new parameter regimes presented by stellar coronas would allow further insight to be gained in the physical processes at work in stellar coronas. Recently, Bastian and Bookbinder (1987) used the Very Large Array The National Radio Astronomy Observatory is operated by Associated Universities, Inc. under contract with the National Science Foundation. in spectral line mode at 1.4 GHz with a bandwidth of 50 MHz to obtain the first dynamic spectra of nearby flare stars. The spectral resolution was 3.125 MHz and the temporal resolution was 5 s. While the relative bandwidth was less than ideal (δν/ν ∼ 5%), the spectra so obtained were sufficient to show the presence of narrowband structure in a radio outburst from the well-known dMe flare star UV Ceti. Several efforts are now underway to obtain stellar dynamic spectra, of both RS CVn binaries and dMe flare stars, with higher degrees of spectral and temporal resolution. Among these are use of a 1024 channel correlator with the 1000' telescope at Arecibo and use of the Berkeley Fast Pulsar Search Machine (Kulkarni et al. 1984) with the Green Bank 140' telescope.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00147709
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  • 8
    Electronic Resource
    Electronic Resource
    Radio emission from flare stars (1990)
    Springer
    Solar physics 130 (1990), S. 265-294 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Observations of radio emission from flare stars are reviewed, including surveys of flare stars in the solar neighborhood and in stellar associations, studies of quiescent emission, and continuum and spectral studies of radio burst emission. The radio observations are placed in an observational context provided by soft X-ray, UV, and optical observations. It is stressed that, as is the case for the latter wavelength regimes, observations of rado bursts on flare stars are qualitatively similar to those on the Sun, albeit in a dramatically scaled-up fashion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00156794
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  • 9
    Electronic Resource
    Electronic Resource
    Location of type I radio continuum and bursts on Yohkoh soft X-ray maps (1995)
    Springer
    Solar physics 160 (1995), S. 151-169 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A solar type I noise storm was observed on 30 July, 1992 with the radio spectrometer Phoenix of ETH Zürich, the Very Large Array (VLA) and the soft X-ray (SXR) telescope on board theYohkoh satellite. The spectrogram was used to identify the type I noise storm. In the VLA images at 333 MHz a fully left circular polarized (100% LCP) continuum source and several highly polarized (70% to 100% LCP) burst sources have been located. The continuum and the bursts are spatially separated by about 100″ and apparently lie on different loops as outlined by the SXR. Continuum and bursts are separated in the perpendicular direction to the magnetic field configuration. Between the periods of strong burst activities, burst-like emissions are also superimposed on the continuum source. There is no obvious correlation between the flux density of the continuum and the bursts. The burst sources have no systematic motion, whereas the the continuum source shows a small drift of ≈ 0.2″ min−1 along the X-ray loop in the long-time evolution. The VLA maps at higher frequency (1446 MHz) show no source corresponding to the type I event. The soft X-ray emission measure and temperature were calculated. The type I continuum source is located (in projection) in a region with enhanced SXR emission, a loop having a mean density of 〈n e〉 = (1.5 ± 0.4) × 109 cm−3 and a temperature ofT = (2.1 ± 0.1) × 106 K. The centroid positions of the left and right circularly polarized components of the burst sources are separated by 15″–50″ and seem to be on different loops. These observations contradict the predictions of existing type I theories.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00679102
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  • 10
    Electronic Resource
    Electronic Resource
    Stellar flares (1994)
    Springer
    Space science reviews 68 (1994), S. 261-274 
    Details
    ISSN: 1572-9672
    Keywords: Stars: Activity ; Stars: Flare ; Radio Continuum: Stars ; X-Rays: Stars
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Radio and X-ray observations of stellar flares provide the most direct probes of energy relaase particle acceleration, and energy transport on stars other than the Sun. In this review, the observational basis for our understanding of the flare phenomenon on other stars is briefly described and outstanding interpretive and theoretical issues are discussed. I shall confine my attention to objects which are “solar-like”, to the extent that they possess deep convective envelopes and display activity which is presumed to be magnetic in origin. These include pre-main sequence objects, classical flare stars, and close binaries. Future directions are briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00749152
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