Magnetospheric Current Sheets and Boundary Layers

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This research program is concerned with some of the physical processes that occur in thin electrical current sheets and plasma boundary layers in the Earth's magnetosphere. Special emphasis is placed on the magnetopause current layer, which forms the outer boundary of the magnetosphere and separates it from the rapidly streaming solar wind, and the adjacent boundary layers which contain plasma of solar-wind origin that has penetrated the magnetopause. These boundary layers are magnetically connected to the auroral-zone ionosphere and thus provide an important channel for the transport of solar-wind energy from the outer reaches of the magnetosphere to the ionosphere where it is dissipated. A second area of emphasis is the current sheet in the geomagnetic tail and the adjacent plasma sheet boundary layers which play an important role in magnetic storms and substorms. In both of these locations the magnetic-field reconnection process is believed to occur and to be of dominant importance. For this reason, the primary focus of the research is to study reconnection, both at the magnetopause and in the magnetotail. Steady and nonsteady reconnection will be examined by use of spacecraft data, analytical modeling, and computer simulation. A secondary focus of the project is a study of the structure and stability of the low-latitude boundary layer, located just inside the equatorial magnetopause, and its coupling to the auroral ionosphere via field-aligned currents and associated field-aligned potential drops in which particles may be accelerated to kilovolt energies.