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| Titel |
The "step feature" of suprathermal ion distributions: a discriminator between acceleration processes? |
| VerfasserIn |
H. J. Fahr  , H. Fichtner |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 30, no. 9 ; Nr. 30, no. 9 (2012-09-05), S.1315-1319 |
| Datensatznummer |
250017264
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| Publikation (Nr.) |
 copernicus.org/angeo-30-1315-2012.pdf |
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| Zusammenfassung |
| The discussion of exactly which process is causing the preferred build-up of
v−5-power law tails of the velocity distribution of suprathermal
particles in the solar wind is still ongoing. Criteria allowing one to
discriminate between the various suggestions that have been made would be
useful in order to clarify the physics behind these tails. With this study, we
draw the attention to the so-called "step feature" of the velocity
distributions and offer a criterion that allows one to distinguish between
those scenarios that employ velocity diffusion, i.e. second-order Fermi
processes, which are prime candidates in the present debate. With an
analytical approximation to the self-consistently obtained velocity diffusion
coefficient, we solve the transport equation for suprathermal particles. The
numerical simulation reveals that this form of the diffusion coefficient
naturally leads to the step feature of the velocity distributions. This
finding favours – at least in regions of the appearance of the step feature
(i.e. for heliocentric distances up to about 11 AU and at lower energies) –
the standard velocity diffusion as a consequence of the particle's
interactions with the plasma wave turbulence as opposed to that caused by
velocity fluctuation-induced compressions and rarefactions. |
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