Neutral sheet normal direction determination

One of the important parameters in magnetotail studies is the thickness of the current sheet. The determination of this thickness is subject to many assumptions of the geometry, such as the current sheet normal direction. The minimum variance analysis (MVA) has been widely used in studies of the current sheet in the tail or at the magnetopause with single-satellite magnetometer data. With four Cluster spacecraft, we are able to determine the current sheet normal direction by using the crossing timings. In this study, we perform MVA on selected Cluster neutral sheet crossing cases to determine the normal directions. We compare these MVA normal estimates with the timing-derived normals. We find that both MVA and four spacecraft timing analysis give useful data.