A Numerical Study of Particle Acceleration in the Magnetosphere

概要

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In order to obtain the quantitative result for wave-particle interaction within the complicated magnetospheric configuration, the Fermi acceleration of energetic electrons trapped within the dipole magnetic field due to the interaction with a large-amplitude hydromagnetic pulse is numerically analysed, under the condition of the magnetic moment conservation. Associated with the geomagnetic sudden commencement, if this pulse propagates from the equator to high latitudes along the particular field line multiple head-on collisions of the particle with the moving pulse yield the net acceleration and secular lowering of the mirror point, until the mirror point is overtaken by the pulse. Assuming a model distribution of the plasma density and Poynting flux conservation of the pulse during its propagation, the motion of an interacting electron is determined in detail for various initial equatorial pitch angle. It is shown that the acceleration by this process is most effective for trapped particles near the equator. From results of the present numerical study, however, we cannot expect the appreciable particle precipitation associated with the geomagnetic ssc by only consideration of the Fermi process, and other more intense acceleration mechanism will be necessary in the real magnetosphere.
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