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  • 1
    Electronic Resource
    Electronic Resource
    Non-linear wave coupling, a potential mechanism for harmonic microwave radiation during solar flares
    Amsterdam : Elsevier
    Vistas in Astronomy 31 (1988), S. 55-58 
    Details
    ISSN: 0083-6656
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0083-6656(88)90174-2
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  • 2
    Electronic Resource
    Electronic Resource
    Bestimmung des Leistungsspektrums der statistischen Verstärkungsschwankungen von Mikrowellenverstärkern (1969)
    Springer
    Zeitschrift für angewandte Mathematik und Physik 20 (1969), S. 584-584 
    Details
    ISSN: 1420-9039
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01595069
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  • 3
    Electronic Resource
    Electronic Resource
    Transient phenomena in the energetic behind-the-limb solar flare of september 29, 1989 (1996)
    Springer
    Astrophysics and space science 243 (1996), S. 209-213 
    Details
    ISSN: 1572-946X
    Keywords: Flare ; CME ; Post-Eruption Energy Release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The powerful cosmic ray flare of Sept. 29, 1989 occurred behind the limb and was observed over a wide spectral range. The analysis of optical, radio, and other relevant data suggest two phases of energy release. After an impulsive phase a prolonged post eruption energy release occurred in an extended region of the corona following the eruption of a large coronal mass ejection (CME). This phase is responsible for numerous coronal and interplanetary phenomena including the ground-level increase of cosmic rays.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00644057
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Dynamics of energetic electrons in a solar flare loop and the flattening of its millimeter-wavelength radio emission spectrum (1996)
    Springer
    Radiophysics and quantum electronics 39 (1996), S. 971-977 
    Details
    ISSN: 1573-9120
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A comparison of predictions by the dynamical trap- plus- precipitation model of broadband microwave bursts and the empirical data on intensive solar flares at centimeter and millimeter wavelengths is presented. The main finding of the data analysis and model calculations is the spectral flattening throughout the entire burst duration. This effect occurs always in the decay phase of the flux peaks at frequencies well above the spectrum peak frequency and is independent of the burst duration. It was found that in some bursts the flux maxima at the higher frequencies are delayed compared to the maxima at the lower frequencies. These effects can be interpreted as being a consequence of the hardening of the electron energy spectrum in the decay phase of the burst.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02250975
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  • 5
    Electronic Resource
    Electronic Resource
    Evidence for a common source of fragmented decimeter emission and meter wave type II bursts in some solar type IV bursts (1994)
    Springer
    Space science reviews 68 (1994), S. 211-216 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The paper presents facts of relevance for flare particle acceleration and shock wave excitation in the solar corona from a detailed analysis of meter wave (40–800 MHz OSRA Tremsdorf spectrograms) and microwave data (3.1–50 GHz polarimeter records Bern University) of several type IV bursts. We argue for a slowly uprising (about 0.1 of the local Alfvén speed) quasi-periodically acting (1...3 min period) accelerator in the 1011...109 cm−3 density region. It produces particles emitting patches of fragmented decimetric/metric radio emission. One of the quasi-periodically appearing patches is associated with the microwave burst emission, the same (or a later, lower frequency one) immediately preceeds the meter wave type II burst lanes. Therefore the onset of the patch source seems to induce also the MHD-like disturbance which can steepen to the type II burst emitting shock. In some events the fragmented patches in the frequency-time plane show a linear spreading toward lower and higher frequencies. This can be a signature of an accelerated movement. Our interpretation of the data allows to understand some of the timing and location problems between the type II shockfront and other CME or flare components.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00749140
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Evidence of harmonic microwave radiation during solar flares (1987)
    Springer
    Solar physics 111 (1987), S. 181-188 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract First observational evidence of harmonic radiation at microwave frequencies during solar bursts is presented for the event of April 28, 1983. The recordings between 3.1 and 19.6 GHz show a typical continuum with a spectral maximum near 5.2 GHz. Superimposed fine structures with durations in the order of some seconds exhibit a very unusual spectral behaviour. Narrow-banded intensity peaks appeared at 5.2 and 11.8 GHz which were barely visible at 3.1, 8.4 and 19.6 GHz. These structures can be interpreted as harmonic emission. Harmonic radio emission can be generated either by plasma radiation, gyroradiation, electron-cyclotron maser or by nonlinear conversion processes. However, all of those mechanisms require extreme assumptions on the source and the ambient plasma in order to account for the observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00145451
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Hard X-ray and radio emission at the onset of great solar flares (1987)
    Springer
    Solar physics 111 (1987), S. 225-233 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A study of the onset phase often great hard X-ray bursts is presented. It is shown from hard X-ray and radio observations in different wavelength ranges that the energization of the electrons proceeds on a global time-scale of some tens of seconds. In nine of the bursts two phases of emission can be distinguished during the onset phase: the pre-flash phase, during which emission up to an energy limit ranging from some tens of keV to 200 keV is observed, followed ten to some tens of seconds later by the flash phase, where the count rate in all detector channels rises simultaneously to within some seconds. For two of the events strong γ-ray line emission is observed and is shown to start close to the onset of the flash phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00145455
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Observations and interpretation of solar flares at microwave frequencies (1988)
    Springer
    Solar physics 118 (1988), S. 155-183 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The physical processes responsible for microwave emission in solar flares are outlined, and examples of how microwave observations have been interpreted in terms of physical parameters are described. Selected results obtained during Solar Cycle 21 with the microwave observatories dedicated to synoptic observations of the Sun are summarized. The status and future plans for these facilities at Bern and in Japan are presented. Also discussed are the instrument capabilities required at microwave frequencies to achieve the objectives of a future facility for high-energy solar physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00148592
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    Paper (German National Licenses)
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  • 9
    Electronic Resource
    Electronic Resource
    A multibeam antenna for solar MM-wave burst observations with high spatial and temporal resolution (1992)
    Springer
    Solar physics 142 (1992), S. 157-170 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In this paper a new method for the determination of the position of microwave burst sources on the Sun, its implementation and first observational results, are presented. The 13.7 m antenna at Itapetinga with a five-channel receiver operating at 48 GHz and with a time resolution of 1 ms is used. Five horn antennas clustered around the focus of the Cassegrain reflector provide 5 beams diverging by about 2′. This configuration allows the observation of different parts of an active region and the determination of the center of the burst position with an accuracy of 5″ to 20″ depending on the angular distance relative to the antenna axis. The field of view is ≈ 2′ by ≈ 4′. The time resolution of 1 ms is suitable to search for fast structures at 48 GHz. A total bandwidth of 400 MHz is used in order to achieve a sensitivity of 0.04 s.f.u. sufficient for the detection of weak bursts. First observational results of the flare on May 11, 1991 show a well-located source position during all stages.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00156639
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  • 10
    Electronic Resource
    Electronic Resource
    Evaporation causes flare-related radio burst continuum depressions (1993)
    Springer
    Solar physics 145 (1993), S. 151-168 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We study the active region NOAA 6718 and the development of a (2N, M3.6) flare in radio and Hα. Due to our knowledge of the magnetic field structure in the active region we are able to associate the different radio flare burst components with the stages in the Hα flare evolution. A discussion of the data in terms of chromospheric flare kernel heating reveals that in the present case the observed flare-related radio burst continuum switch-off is caused by the penetration of hot, ablated gas into the coronal radio source.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00627991
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