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| Titel |
Propagation of whistler-mode chorus to low altitudes: divergent ray trajectories and ground accessibility |
| VerfasserIn |
J. Chum, O. Santolík |
| 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 ; 23, no. 12 ; Nr. 23, no. 12 (2005-12-23), S.3727-3738 |
| Datensatznummer |
250015436
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| Publikation (Nr.) |
 copernicus.org/angeo-23-3727-2005.pdf |
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| Zusammenfassung |
| We investigate the ray trajectories of nonductedly propagating lower-band
chorus waves with respect to their initial angle θ0, between the wave
vector and ambient magnetic field. Although we consider a wide range of
initial angles θ0, in order to be consistent with recent satellite
observations, we pay special attention to the intervals of initial angles
θ0, for which the waves propagate along the field lines in the source
region, i.e. we mainly focus on waves generated with &theta0 within an
interval close to 0° and on waves generated within an interval close to
the Gendrin angle. We demonstrate that the ray trajectories of waves generated
within an interval close to the Gendrin angle with a wave vector directed
towards the lower L-shells (to the Earth) significantly diverge at the
frequencies typical for the lower-band chorus. Some of these diverging
trajectories reach the topside ionosphere having θ close to 0°; thus, a
part of the energy may leak to the ground at higher altitudes where the field
lines have a nearly vertical direction. The waves generated with different
initial angles are reflected. A small variation of the initial wave normal angle
thus very dramatically changes the behaviour of the resulting ray. Although
our approach is rather theoretical, based on the ray tracing simulation, we
show that the initial angle θ0 of the waves reaching the ionosphere
(possibly ground) is surprisingly close - differs just by several degrees
from the initial angles which fits the observation of magnetospherically
reflected chorus revealed by CLUSTER satellites. We also mention
observations of diverging trajectories on low altitude satellites. |
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