Azimuthal and latitudinal changes of the near-Earth magnetotail current sheet structure during multiple dipolarizations of a substorm

Using data from fleet of spacecraft in the near-Earth night-side magnetosphere, we study the three-dimensional evolution of the magnetotail current sheet following the expansion phase onset of a moderate substorm (AL ~-450 nT) after 09:10 UT, April 10, 2020.  Magnetotail disturbances are observed by GOES 17 and Cluster in the midnight region.  During this substorm the BepiColombo spacecraft traversed the premidnight region duskward at 9-11 RE downtail during its Earth Flyby.  The four Cluster satellites, which were separated mainly in north-south direction, crossed the inner magnetosphere successively from north to south. They enable us to monitor the vertical (latitudinal) structure and the sequential changes of the magnetotail current sheet until the end of the recovery phase of the substorm, around 11 UT.  Multiple dipolarizations and multiple transient field-aligned currents (FAC) were observed by Cluster.  The first dipolarization around the onset, which was detected by GOES 17 in the geosychronous region, was accompanied by a plasma sheet expansion observed by the two leading Cluster 3 and 4 satellites. BepiColombo in the premidnight region observed continuous thinning of the current sheet, a typical signature of the growth phase, accompanied by a couple of transient magnetic signatures indicating flux rope and/or TCR formation around the onset.  Cluster 1 detected the most intense FAC associated with the dipolarization event starting around 10 UT, when the two BepiColombo MPO and MIO spacecraft observed dipolarization and energetic particle injection. These observations indicate the duskward and tailward expansion in the course of multiple dipolarizations.  Using the unique dataset from the multi-point observations, we examine the structure of the large-scale current sheet and analyze the embedded transient intense field-aligned current disturbances. By also comparing with an empirical magnetic field model, we obtain the changes of the near-Earth magnetotail structure during the multiple dipolarization event.