Coupling modes of hydromagnetic oscillations in non-uniform, finite pressure plasmas: Two-fluids model |
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Authors: | Tsutomu Tamao |
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Institution: | Geophysics Research Laboratory, University of Tokyo, Tokyo 113, Japan |
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Abstract: | Within a framework of the two-fluids approximation, basic modes constituting hydromagnetic coupling oscillations in non-uniform, finite-β plasmas are examined. It is shown that the oscillations consist of a coupling between a localized mode and a propagating one, and a strong peak appears at a resonance point. In the case of isothermal plasma (Te = Ti), there are two localized modes, the Alfvén (or drift Alfvén) and the ion drift modes, and a propagating mode being known as the fast magnetosonic wave. Coupling oscillations associated with the Alfvén mode exhibit a nearly incompressible character, whereas those with the ion drift mode are compressional and diamagnetic. Furthermore, the slow magnetosonic wave also couples with the localized mode in the case of Te > Ti. Based on characteristics of these oscillations, the origin of geomagnetic pulsations is discussed in connection with the distribution of plasma parameters in the outer magnetosphere. |
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