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41.
Magnetosonic waves near the harmonics of proton cyclotron frequency can become unstable in the presence of oxygen ions in the ring current. For cos θ = 0 (θ being the angle between the wave vector and the geomagnetic field) the growth rates are peaked at some optimum value of the oxygen ion density, whereas for cos θ ≠ 0 they are reduced with the increase of oxygen ion density. The presence of hot oxygen ions can generate instability near the harmonics of oxygen cyclotron frequency. The growth rates are enhanced with the increase of cos θ. This mechanism can generate discrete spectrum of ELF hiss beyond the plasmapause. 相似文献
42.
G. S. Lakhina 《Solar physics》1977,52(1):153-162
The ordinary mode can frequently become unstable in the solar wind at 1 AU provided the ratio of halo to core electrons density does not exceed the value 0.05. The growth rates corresponding to the average conditions are typically 10
P (
P being the proton cyclotron frequency). Because of low threshold for onset of instability for
C
1 (where
C
is the transverse beta for the core electrons), the mode is expected to play an important role in regulating the solar wind heat flux at 1 AU. 相似文献
43.
G. S. Lakhina 《Astrophysics and Space Science》1987,133(2):203-218
The pick up cometary ion distributions are shown to excite Alfvénic mode instabilities, slow ion-acoustic mode instability and a lower hybrid instability during solar wind-comet interaction. The growth rates of all these instabilities become larger as the comet is approached. The lower hybrid instability is shown to account for the low-frequency 0–300 Hz electrostatic turbulence observed near comet Halley. The Alfvén modes can grow to large amplitudes and become modulationally unstable, in the presence of low-frequency density fluctuations, going over to envelope Alfvén solitons. A model consisting of a gas of Alfvén solitons is suggested to explain the hydromagnetic turbulence observed near comet Halley and comet Giacobini-Zinner. 相似文献
44.
Hot electrons injected during solar flares at the top of coronal loops interact with the cooler chromospheric plasma and excite lower hybrid (LH) instabilty. The saturation electric fields due to LH instability can be of the order of a few hundred V cm–1. Such high electric fields can stochastically accelerate protons and other minor ions. The heavier ions are preferentially accelerated by this stochastic process. 相似文献
45.
46.
The effect of collisions on electrostatic instabilities driven by gravity and density gradients perpendicular to the ambient magnetic field is studied. Electron collisions tend to stabilize the short wavelength (ky?i ? 1, where ky is the perpendicular wavenumber of the instability and ?i is the ion Larmor radius) kinetic interchange mode. In the presence of weak ion-ion collisions, this mode gets converted into an unmagnetized ion interchange mode which has maximum growth rate one order smaller than that of the collisionless mode. On the other hand, electron collisions can excite a long wavelength resistive interchange mode in a wide wavenumber regime () with growth rates comparable to that of the collisional Rayleigh-Taylor mode. The results may be relevant to some of the spread F irregularities. 相似文献