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| Titel |
High frequency ion sound waves associated with Langmuir waves in type III radio burst source regions |
| VerfasserIn |
G. Thejappa, R. J. MacDowall |
| 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 ; 11, no. 3 ; Nr. 11, no. 3 (2004-09-21), S.411-420 |
| Datensatznummer |
250009246
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| Publikation (Nr.) |
 copernicus.org/npg-11-411-2004.pdf |
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| Zusammenfassung |
| Short wavelength ion sound waves (2-4kHz) are detected
in association with the
Langmuir waves (~15-30kHz)
in the source regions of
several local type III radio
bursts. They are most probably not due to
any
resonant wave-wave interactions
such as the
electrostatic decay instability because
their
wavelengths are much shorter than those of Langmuir waves.
The Langmuir waves occur as
coherent field structures with
peak intensities exceeding
the Langmuir collapse thresholds. Their
scale sizes are of the order of
the wavelength of an ion sound wave.
These Langmuir wave field characteristics
indicate that the observed short wavelength ion sound waves are most probably
generated during the thermalization of the burnt-out cavitons left behind by
the Langmuir collapse.
Moreover, the peak intensities of the observed short wavelength ion sound
waves are comparable to the expected intensities of those
ion sound waves radiated by
the burnt-out cavitons.
However, the speeds of the electron beams derived from the frequency drift
of type III radio bursts are too slow to satisfy the needed adiabatic ion
approximation. Therefore, some non-linear process such as the induced
scattering on thermal ions most probably pumps the beam excited Langmuir
waves towards the lower wavenumbers, where the adiabatic ion approximation
is justified. |
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