Plasma waves and instabilities

Abstract. In nonstationary, strong inhomogeneous or open plasmas particle orbits are rather complicated. If the nonstationary time scale is smaller than the gyration period, if the inhomogeneity scale is smaller than the gyration radius, i.e. at magnetic plasma boundaries, or if the plasma has sources and sinks in phase space, then nongyrotropic distribution functions occur. The stability of such plasma configurations is studied in the framework of linear dispersion theory. In an open plasma nongyrotropy drives unstable waves parallel and perpendicular to the background magnetic field, whereas in the gyrotropic limit the plasma is stable. In nonstationary plasmas nongyrotropy drives perpendicular unstable waves only. Temporal modulation couples a seed mode with its side lobes and thus it renders unstable wave growth more difficult. As an example of an inhomogeneous plasma a magnetic halfspace is discussed. In a layer with thickness of the thermal proton gyroradius a nongyrotropic distribution is formed which may excite unstable parallel and perpendicular propagating waves.Key words. Interplanetary physics (plasma waves and turbulence) · Ionosphere (plasma waves and instabilities) · Magnetospheric physics (plasma waves and instabilities)

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Nonstationary pearl pulsations as a signature of magnetospheric disturbances

Annales Geophysicae ◽

10.1007/s00585-000-0517-9 ◽

2000 ◽

Vol 18 (5) ◽

pp. 517-522 ◽

Cited By ~ 3

Author(s):

F. Z. Feygin ◽

N. G. Kleimenova ◽

O. A. Pokhotelov ◽

M. Parrot ◽

K. Prikner ◽

...

Keyword(s):

Electric Field ◽

Plasma Waves ◽

Magnetic Activity ◽

Magnetospheric Physics ◽

Central Frequency ◽

Plasma Waves And Instabilities ◽

Magnetospheric Configuration And Dynamics ◽

Diurnal Distribution ◽

Magnetospheric Configuration

Abstract. We analyse long-lasting (several hours) Pc1 pearl pulsations with decreasing, increasing or constant central frequencies. We show that nonstationary pearl events (those with either decreasing or increasing central frequency) are observed simultaneously with increasing auroral magnetic activity at the nightside magnetosphere while the stationary events (constant central frequency) correspond to quiet magnetic conditions. Events with decreasing central frequency are observed mostly in the late morning and daytime whereas events with increasing central frequency appear either early in the morning or in the afternoon. We explain the diurnal distribution of the nonstationary pearl pulsations in terms of proton drifts depending on magnetic activity, and evaluate the magnetospheric electric field based on the variation of the central frequency of pearl pulsations.Key words: Magnetospheric physics (magnetospheric configuration and dynamics; plasma waves and instabilities)

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