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| Titel |
Probabilistic model of beam-plasma interaction in the randomly inhomogeneous solar wind |
| VerfasserIn |
Vladimir Krasnoselskikh, Andrii Voshchepynets |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250109833
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| Publikation (Nr.) |
 EGU/EGU2015-9781.pdf |
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| Zusammenfassung |
| We apply the probabilistic model of beam plasma interaction proposed before to electron
beams propagating in the interplanetary plasma taking into account known properties of the
density fluctuations in the solar wind measured aboard ISEE. The new element here with
respect to previous work consists in the calculation of the probability density for density
fluctuations having power law spectra, while previously we used Gaussian probability
distribution. We use the property that for the given frequency the probability distribution of
density fluctuations uniquely determines the probability distribution of phase velocity of
wave. We present the system as discrete consisting of small equal spatial intervals and the
density profile on each small interval is linear. The model is based on general description
of the wave particle interaction on any of these small spatial intervals with linear
profile. We solve equations of motion of a particle under the action of the wave
with the given amplitude and phase in the beginning of the interval. This approach
allows one to estimate variations of the wave’s energy density and particle’s velocity,
depending on the density gradient. The presence of the plasma inhomogeneity results
in the variation of the phase velocity of the wave having known frequency and
causes a spreading of the width of the resonance in the velocity space. Since the
characteristic time of the evolution of the electron distribution function and wave energy is
much longer than the time of the single wave-particle resonant interaction on a
given small interval, we can proceed to the description of the relaxation process
in terms of averaged quantities. We derive a system of equations, similar to the
quasi-linear approximation, but conventional velocity diffusion coefficient Dand
the wave’s growth rate γ are replaced by averaged in phase space making use the
probability distribution of phase velocities and assuming that the interaction on each
interval is independent upon previous interactions. The dependencies of functions
Dand γ are completely determined by the statistical properties of the distribution
function of the amplitudes of the fluctuations. We show, that in the case of solar
wind the relaxation process is determined similarly to Gaussian case by four major
parameters, the beam velocity ratio to thermal velocity of plasma, the dispersion and
amplitude of the fluctuations, and, the width of the beam in the velocity space. We
show that the length of relaxation of the beams can be sufficiently larger than 1AU. |
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