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  • 1
    Electronic Resource
    Electronic Resource
    A role of cosmic rays in generation of radio and optical radiation by plasma mechanisms (1987)
    Springer
    Astrophysics and space science 132 (1987), S. 213-248 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The radiation of ultrarelativistic particles is examined in a quasi-uniform magnetic field superimposed by a wide spectrum of magnetic, electric, and electron density inhomogeneities created in a turbulent plasma. The radiation spectrum from a particle of a given energy is shown to acquire a high-frequency power-law tail with the same spectral index as the index ν of small-scale turbulence. For a power-law spectrum of ultrarelativistic electrons, dN(ℰ)/dℰ ~ ℰ−ξ, with a cut-off at some energy ℰmax, the radiation spectrum consists of a few power-law ranges; the radiation intensity may suffer jumps at frequencies which separate these ranges. In the high-frequency range the spectral index ν is determined by small-scale magnetic and electric fields. At intermediate frequencies the main contribution comes from the synchrotron radiation in a large-scale field; the radiation spectrum has an index α=(ζ−1)/2. The same index may be produced by large-scale Langmuir waves. At lower frequencies the radiation spectrum increases owing to the transition radiation caused by electron density fluctuations; in this case the spectral index is equal to ζ+1−ν. The possibility of diagnostics of high-frequency cosmic plasma turbulence from radiation of high-energy particles is discussed. It is shown that the proposed theory may explain some features in the spectra of several cosmic objects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00641755
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  • 2
    Electronic Resource
    Electronic Resource
    Nonlinear treatment for solar radio spikes (1994)
    Springer
    Solar physics 153 (1994), S. 367-388 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We emphasize that a nonlinear treatment is required to realize the diagnostic potentiality of solar spiky emission. The observational constraints including the latest data on the harmonic structure, degree, and sense of polarization are discussed. A set of coupled equations for energy density of high-frequency normal modes of a magneto-active plasma involving the most important nonlinear effects within the three-wave approximation is deduced. The equations include both previously known and new effects. The qualitative evaluations of the equations obtained have provided a few new findings: (i) quasi-linear relaxation of fast electrons on quasi-potential waves (ω_) occurs in a characteristic time scale of the order of 10 ms if the frequency,f, is about 1 GHz; (ii) the stimulated scattering of the transverse waves on the background plasma particles is shown to be important if the brightness temperature of the spiky emission exceeds 1015–1016 K; (iii) the Raman scattering of the transverse waves on background plasma density inhomogeneities may suppress the electron cyclotron maser instability if 〈Δn e 2 〉/n e 2 ≳ 3 × (10−4–10−5).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00712511
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  • 3
    Electronic Resource
    Electronic Resource
    Nonlinear treatment for solar radio spikes (1994)
    Springer
    Solar physics 153 (1994), S. 389-402 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Linear (temporal and spatial) growth rates of high-frequency normal modes are calculated when an unstable fast electron population with a two-side loss cone and power-law energetic distribution exists in a magnetized plasma. The dominant mode is shown to be: fundamentalX-mode ifY =ω pe/ω Be 〈 0.2∓0.3,lh-mode if 0.2∓0.3 〈Y 〈 0.5∓0.8, fundamentalZ-mode if 0.5∓0.8 〈Y 〈 0.9 for a broad energetic spectrum of electrons (10 keV≲E ≲ 200 keV). These modes are generated by different groups of fast electrons. The results presented can be used for further study of nonlinear effects in ECM problems including quasilinear relaxation of the instability. From the obtained dependence of the growth rates on the bandwidth of the electron spectrum we predict that the spiky emission should have no correlation with electron gamma-ray Bremsstrahlung, contrary to the correlation with hard X-ray emission. We find that the growth rates can grow with the decrease of the electron distribution anisotropy (in a certain range of the anisotropy parameter value). This behaviour explains naturally a super-exponential (gaussian) rise phase of the spikes discovered in observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00712512
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  • 4
    Electronic Resource
    Electronic Resource
    Radio signature of fragmented electron injection into a coronal loop (1994)
    Springer
    Solar physics 153 (1994), S. 403-417 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract High-time-resolution observations of an unusual event of 1991 November 17, 07:04 UT at 2.5 and 2.85 GHz are presented. The event demonstrates sophisticated tine time structure including sudden reductions and quasi-periodic pulsations about various ‘zero’ levels. It is shown that the sudden reductions (≈30–100 ms) can be produced with upward-injected 〉 100 keV electron beams filling the loss-cone. In such a case the acceleration is proceeding in a dense plasma layer with number densityn 〉 2.5 × 1010 cm−3. The shortest time scale of the fragmented injection isт inj min ≈ 30 ms. Several different pulsating regimes arising due to the wave-particle and wave-wave interactions are considered. A theoretical mechanism with the nonlinear oscillations of Langmuir waves at the different steady-state levels provides the best agreement with the observed pulsations. The reduced steady-state level of the second train of pulsations is connected with the long (quasi-continuous) injection of electrons filling the loss-cone, which reduced the wave energy level. Physical parameters of the radio source were obtained. On the other hand, ECM nonlinear pulsations seem to be responsible for the radio pulsations observed in dMe stars.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00712513
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  • 5
    Electronic Resource
    Electronic Resource
    On the harmonic structure of solar radio spikes (1994)
    Springer
    Solar physics 154 (1994), S. 361-369 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This paper analyzes the frequency structure of the bands of electron-cyclotron maser instability. The calculations show that each term of the series describing the growth rate provides a double-peak structure, if we accept a nonthermal electron distribution with a ‘two-side’ loss-cone. The ratio of central frequencies is found to be non-integer in general case. We conclude that the harmonic structure of solar radio spikes observed in a number of events can be imitated by electron-cyclotron maser emission of mildly relativistic electrons with a power-law momentum distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00681104
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  • 6
    Electronic Resource
    Electronic Resource
    On polarization of transition bremsstrahlung in a weakly gyrotropic plasma (1995)
    Springer
    Radiophysics and quantum electronics 38 (1995), S. 577-580 
    Details
    ISSN: 1573-9120
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The degree of polarization of transition bremsstrahlung (TBS) is calculated in a plasma with weak gyrotropy. The cases of weak and strong Faraday rotation in a radiation source are discussed. The distribution of polarization is shown to have no azimuthal symmetry, if the particle gyroradius is larger than the source size. We calculate the polarization degree of TBS for an ensemble of fast particles and show that polarization exceeds the respective value for transition radiation in the presence of nonthermal inhomogeneities of the plasma density.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01037838
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  • 7
    Electronic Resource
    Electronic Resource
    Transition radio emission of mildly relativistic particles (1994)
    Springer
    Space science reviews 68 (1994), S. 243-244 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report new calculations of transition radiation spectra which are correct for arbitrary energy of a particle at all frequencies down to plasma frequency. The importance of the emission mechanism for solar flares are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00749145
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  • 8
    Electronic Resource
    Electronic Resource
    Microwave burst of November 17, 1991: Evidence of fragmented particle injection into a coronal loop (1994)
    Springer
    Space science reviews 68 (1994), S. 205-210 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The unusual event of November 17, 1991 07:04 UT, observed at 2.5 and 2.85 GHz, is analysed. The event reveals the sophisticated superfine time structure including sudden reductions and quasi-periodic pulsations. We shown that the sudden reductions (≈30–100 ms) can be driven by upward injected ≳100 keV electron beams filling the losscone of the coronal magnetic trap. The nonlinear oscillations of Langmuir waves provide the best fit for the pulsation observed. A reduced steady-state level of the pulsation phase is connected with quasi-continuous injection of electrons. The physical parameters of the radio source are found for the event.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00749139
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  • 9
    Electronic Resource
    Electronic Resource
    Theory of synchrotron radiation in the presence of random magnetic and electric fields (1987)
    Springer
    Radiophysics and quantum electronics 30 (1987), S. 260-267 
    Details
    ISSN: 1573-9120
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01033953
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  • 10
    Electronic Resource
    Electronic Resource
    On the saturation of electron-cyclotron masers in solar flares (1992)
    Springer
    Solar physics 139 (1992), S. 387-399 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We consider the relaxation of an unstable distribution of fast non-relativistic electrons. Langmuir turbulence generated by the electrons is found to determine the saturation of an electron-cyclotron maser. The important role of nonlinear processes in Langmuir and electromagnetic waves is shown. The characteristic saturation time is about 1 ms. It is shown that both cyclotron maser emission and the transformation of plasma waves to transverse ones can be essential in the formation of observable radio spectra from solar flares.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00159160
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