A GENERALIZATION OF THE MINIMUM-VARIANCE ANALYSIS METHOD

In order to determine the normal direction of the magnetopause, the mi nimum variance analysis technique is frequently used: it is applied to the magnetic field data of a magnetopause crossing observed by a sate llite, and provides the direction along which the magnetic field varia tion is minimum. In this study we propose a method to extend naturally the framework of the minimum variance analysis so that it includes al l continuity conditions across a planar magnetopause, so that we could use all physical quantities observed by the spacecraft. We first exte nd it to the electric field: we discuss how to determine the normal di rection and the speed of the magnetopause along the normal by using bo th the magnetic and electric field data. We next discuss the full exte nsion to all continuity conditions across the magnetopause. Finally, w e discuss how to extend our method further so that it can deal with th e magnetopause which is accelerating. A discussion of application to o bservations will appear separately.