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| Titel |
Space-time evolution of electron-beam driven electron holes and their effects on the plasma |
| VerfasserIn |
N. Singh |
| 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 ; 10, no. 1/2 ; Nr. 10, no. 1/2, S.53-63 |
| Datensatznummer |
250007820
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| Publikation (Nr.) |
 copernicus.org/npg-10-53-2003.pdf |
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| Zusammenfassung |
| We report here
further results from the three-dimensional particle-in-cell simulations of
the electron-beam driven electron holes. We focus here on (i) the
transformation of oscillatory waves driven by the electron-beam
instability into electron holes, (ii) the continued evolution and
propagation of electron holes after their formation, including merging of
electron holes, and (iii) the effects of the evolution on the plasma
density and ion velocity distribution function. We find that initially
electron-beam modes with perpendicular wave numbers k^
= 0 and as well as k^ ≠
0 are driven resonantly below the electron plasma frequency of the target
plasma. The modes interact nonlinearly and modulate each other both in
space and time, producing wave structures with finite perpendicular scale
lengths. Nonlinear evolution of such wave structures generates the
electron holes in the simulations. Initially, a large number of electron
holes form in the plasma. Their merging yields continuously a decreasing
number of electron holes. The propagation velocity of the electron holes
evolves dynamically and is affected by their merging. At late times only a
few electron holes are left in the simulation and they decay by emitting
low-frequency electrostatic whistler waves just above the lower hybrid (LH)
frequency vlh . These waves,
which are long structures parallel to the ambient magnetic field B0
and quite short transverse to B0, are associated with
similar structures in the plasma density, producing density filaments. It
turns out that electron-beam driven plasmas, in general, develop such
filaments at some stage of the evolution of the beam-driven waves. In view
of the excitation of the LH waves near vlh,
which could resonate with the ions, an analysis shows that it is possible
to heat transversely the ions in a time scale of a few seconds in the
auroral return current plasma, in which electron holes and transversely
heated ions have been simultaneously observed. |
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