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| Titel |
Role of resonance broadening vs ion trapping in the microturbulence triggered within the foot of a supercritical quasiperpendicular shock |
| VerfasserIn |
Laurent Muschietti, Bertrand Lembège |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250076322
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| Zusammenfassung |
| Recent 1D PIC simulations [Muschietti and Lembège, 2013] have been used to analyze
in detail the wave activity within the foot region of a supercritical perpendicular
shock, This turbulence is ascribed to the electron cyclotron drift instability (ECDI)
excited by the relative drift of the reflected ion beam versus the electrons (electron
Bernstein type instability). It is characterized, in the linear stage, by discrete bands of
emission at the gyro-harmonics in agreement with wave dispersion theory. However,
in the late nonlinear stage, we show that the power spectra is characterized by a
dominant emission at the first gyro-harmonic mainly. This unexpected result does
not reflect a «standard» inverse cascade process (shift of power spectra from high
k-modes to lower k-modes), but rather results from two complementary wave damping
processes: (i) trapping of the reflected ion beam, and (ii) resonance broadening.
The latter acts to demagnetize the electrons in the dispersion relation. It initially
applies to very high k-modes (kÏe >> 1) and progressively, as time evolves, to
lower k-modes, invalidating the existence of all gyro-harmonics, except the first
one. A parametric study will be also presented in order to estimate the impact of
each process on the wave emission in the nonlinear stage. Finally, results will be
compared with previous works dedicated to the microturbulence within the shock front
region. |
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