Dawn-dusk scale of dipolarization front in the Earth’s magnetotail: multi-cases study

Abstract

We analyze three dipolarization front (DF) events to investigate their dawn-dusk scales in the Earth’s magnetotail using the Cluster measurements in year 2007, when the spacecraft separation is about 1.8 Re (Re is the Earth’s radius) and is appropriate for investigating the DF scale. Based on the Minimum Variance Analysis (MVA) and the general shape of the DF, we found that Cluster detected the center and the flank (or just beyond the flank) of DF in the same event. This means that the scale of DF is about 3.6 Re in the dawn-dusk direction, larger than that reported in previous studies. Using the semicircle function to fit the observations, we got the dawn-dusk scale of ∼3.2–3.6 Re, consistent with the rough estimation. Considering large separation among the spacecraft, the timing analysis cannot be used to obtain the normal of DF and the propagation velocity along the normal. One should be careful when performing timing analysis of DF using the Cluster data, and have to carry on MVA analysis to check the normal of DF before do timing analysis.