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The Physics Of The Hynamical Evolution Of Electron Firehose Reflection

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In the present paper, we considered the dynamical evolution of protons and electrons in response to parallel electron firehose instability excitation. Even though the free energy source for the instability is provided by excessive electron temperature anisotropy, because of the fact that unstable modes operate in low frequency range, the protons respond to the instability excitation as well. Kinetic instabilities driven by electron and proton temperature anisotropies, of which the present electron firehose instability is a part, are known to play significant roles in regulating the temperature anisotropy upper bound as the solar wind expands out into the interplanetary space from its solar source. In the present paper, we employed…show more content…
The proton behavior, on the other hand, exhibited somewhat poorer agreement. The wave intensity calculation showed a qualitatively good agreement especially for early times, but depending on the input parameters, quasilinear theory may predict lower or higher saturation intensity. We also discussed possible cause(s) of various discrepancies, but in an overall sense, we conclude that the so-called macroscopic quasilinear method maybe a useful first-order tool, but with obvious caveats. In particular, it was shown that the parallel proton firehose instability leads to the formation of parallel proton tail, which the simple bi-Maxwellian model cannot explain. (-- removed HTML --) (-- removed HTML --) Before we conclude the present paper, we reiterate that the obliquely propagating electron firehose mode is known to possess much higher growth rate than the strictly parallel counterpart. Linear theory of parallel and oblique firehose modes have been carried out in the literature, (-- removed HTML --) (-- removed HTML --) 24–34 (-- removed HTML --) (-- removed HTML --) and simulations of these unstable modes have also been carried out in the literature. (-- removed HTML --) (-- removed HTML --) 35–38 (-- removed HTML --) (-- removed HTML --) In this regard, one may question the value of the present work. However, we should point out that simulations are strictly speaking, numerical experiments, which must be interpreted in terms of and
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