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| Titel |
Whistler-Langmuir oscillitons and their relation to auroral hiss |
| VerfasserIn |
K. Sauer, R. D. Sydora |
| 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 ; 29, no. 10 ; Nr. 29, no. 10 (2011-10-05), S.1739-1753 |
| Datensatznummer |
250017102
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| Publikation (Nr.) |
 copernicus.org/angeo-29-1739-2011.pdf |
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| Zusammenfassung |
| A new type of oscilliton (soliton with superimposed spatial oscillations) is
described which arises in plasmas if the electron cyclotron frequency
Ωe is larger than the electron plasma frequency ωe, which is a typical situation for auroral regions in planetary
magnetospheres. Both high-frequency modes of concern, the Langmuir and the
whistler wave, are completely decoupled if they propagate parallel to the
magnetic field. However, for oblique propagation two mixed modes are created
with longitudinal and transverse electric field components. The lower mode
(in the literature commonly called the whistler mode, e.g. Gurnett et al.,
1983) has whistler wave characteristics at small wave numbers and
asymptotically transforms into the Langmuir mode. As a consequence of the
coupling between these two modes, with different phase velocity dependence,
a maximum in phase velocity appears at finite wave number. The occurrence of
such a particular point where phase and group velocity coincide creates the
condition for the existence of a new type of oscillating nonlinear
stationary structure, which we call the whistler-Langmuir (WL) oscilliton.
After determining, by means of stationary dispersion theory, the parameter
regime in which WL oscillitons exist, their spatial profiles are calculated
within the framework of cold (non-relativistic) fluid theory.
Particle-in-cell (PIC) simulations are used to demonstrate the formation of
WL oscillitons which seem to play an important role in understanding
electron beam-excited plasma radiation that is observed as auroral hiss in
planetary magnetospheres far away from the source region. |
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