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| Titel |
Closure of multi-fluid and kinetic equations for cyclotron-resonant interactions of solar wind ions with Alfvén waves |
| VerfasserIn |
E. Marsch |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1023-5809
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| Digitales Dokument |
URL |
| Erschienen |
In: Nonlinear Processes in Geophysics ; 5, no. 2 ; Nr. 5, no. 2, S.111-120 |
| Datensatznummer |
250002327
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| Publikation (Nr.) |
 copernicus.org/npg-5-111-1998.pdf |
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| Zusammenfassung |
| Based on quasilinear theory, a closure scheme for
anisotropic multi-component fluid equations is developed for the wave-particle
interactions of ions with electromagnetic Alfvén and ion-cyclotron waves propagating
along the mean magnetic field. Acceleration and heating rates are calculated. They may be
used in the multi-fluid momentum and energy equations as anomalous transport terms. The
corresponding evolution equation for the average wave spectrum is established, and the
effective growth/damping rate for the spectrum is calculated. Given a simple power-law
spectrum, an anomalous collision frequency can be derived which depends on the slope and
average intensity of the spectrum, and on the gyrofrequency and the differential motion
(with respect to the wave frame) of the actual ion species considered. The wave-particle
interaction terms attain simple forms resembling the ones for collisional friction and
temperature anisotropy relaxation (due to pitch angle scattering) with collision rates
that are proportional to the gyrofrequency but diminished substantially by the relative
wave energy or the fluctuation level with respect the background field. In addition, a set
of quasilinear diffusion equations is derived for the reduced (with respect to the
perpendicular velocity component) velocity distribution functions (VDFs), as they occur in
the wave dispersion equation and the related dielectric function for parallel propagation.
These reduced VDFs allow one to describe adequately the most prominent observed features,
such as an ion beam and temperature anisotropy, in association with the resonant
interactions of the particles with the waves on a kinetic level, yet have the advantage of
being only dependent upon the parallel velocity component. |
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