MMS Spacecraft Observation of Near Tail Thin Current Sheets: Their Locations, Conditions for Formation and Relation to Geomagnetic Activity

Abstract:

During the commissioning phase of the MMS mission, when the apogee (~12Re) of MMS orbit swept from the pre-midnight to the dusk section of the magnetosphere, the four spacecraft probed the dynamic region of the near-Earth magnetotail. The MMS fleet encountered many structures with unambiguously small-scale spatial gradient in magnetic field (comparable to the separation of the fleet), indicating the existence of very thin current sheets in this near-tail region. During this commissioning phase, the MMS spacecraft were in a string of pearls configuration, not ideally suitable for “curlometer” determination of the current density. Thus the current density and thickness of the sheets are only roughly determined using reasonable assumptions. In this study we correlate the current sheet’s location and thickness with solar wind conditions and the ground magnetic field records.