Title

Local structure of Earth's quasi-perpendicular bow shock

Date of Award

Spring 2010

Project Type

Dissertation

Program or Major

Physics

Degree Name

Doctor of Philosophy

First Advisor

Harald Kucharek

Abstract

The multi-satellite mission, Cluster II, provides unique opportunities to study the motion of the Earth's bow shock and related ion populations in the foreshock region. These ion populations are characteristic for specific regions. Commonly these regions are determined by the orientation of the interplanetary magnetic field (IMF) relative to the normal vector of the shock surface. In the parallel regime of the Earth's bow shock the vector is parallel to the IMF whereas in the perpendicular regime the normal vector is perpendicular to the IMF. One of the important reflected ion populations are Field-aligned ion Beams (FABs) which originate at the quasi-perpendicular bow shock. Under the assumption that the local structure consists of a patchwork of "reflectors" at which these FABs originate, we developed a numerical model that allows us to remotely sense the local structure. The obtained wave-like local structure is consistent with 2D hybrid simulation work which has indicated that the local shock structure (ripples) may be controlled by the gyrating ions.

By using this remote sensing method, we investigated the effect of solar wind composition on the local structure of the Earth's bow shock. The density He2+/H+ ratio of solar wind varies 0.001 to 0.2 or even higher. In high He 2+/H+ solar wind, the gyroradius of He2+ may show obvious effects on the spatial scale of local shock structure. The dependence of the spatial scale of local shock structure on the solar wind composition is found.

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