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| Titel |
Electron pitch-angle diffusion in the radiation belts: effects of whistler waves oblique propagation. |
| VerfasserIn |
A. Artemyev, O. Agapitov, H. Breuillard, V. Krasnoselskikh, G. Rolland |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250058561
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| Zusammenfassung |
| The major difficulty in the modeling of the radiation belts dynamics is related with our
restricted knowledge of the probability distribution of whistler wave intensity and
wave-vector directions upon various parameters: frequency, magnetic latitude, L-shell, et. We
use statistical analysis of ten years (2001-2009) measurements of wave characteristics by
Cluster STAFF-SA to establish the wave-vectors distribution upon magnetic latitudes. These
distributions represent an important step in the development of the more precise
procedures for the diffusion coefficients evaluation. We present hereafter the study of the
pitch-angle diffusion of electrons in the outer radiation belt. The propagation direction
of magnetospherically generated whistler waves (chorus waves generated in the
vicinity of the geomagnetic equator) rapidly deflects from the magnetic field with the
increase of latitude. The width of the distribution and consequently the variance
increases also. We take into account obtained distributions of the angle mean value
and variance to calculate pitch-angle diffusion coefficients for various latitudes
and eventually to determine the diffusion rates by averaging over electron bounce
oscillations. The diffusion coefficients obtained using of these new procedures are
compared with those calculated under assumption of whistler parallel propagation with
constant value of variance. We show that the increase of the angle mean value and the
variance of the wave vector distribution with latitude results in significant growth
of the pitch-angle diffusion rates. This growth is related to significant increase of
the contribution of high order cyclotron resonances to electron diffusion at large
latitudes, which is most efficient for electrons with small equatorial pitch-angles. |
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