Simultaneous Geotail and Wind observations of reconnection at the subsolar and tail flank magnetopause

Abstract

We report a fortuitous two‐spacecraft conjunction when Geotail and Wind observed the occurrence of reconnection simultaneously at the subsolar and dawn tail flank magnetopause during stable By dominated IMF. Furthermore, bi‐directional jets were observed by Geotail which indicate the presence of an X‐line in the subsolar region. These observations are consistent with the presence of a tilted X‐line hinged near the subsolar point and spanning the entire dayside (from subsolar to XGSE = −10 RE) magnetopause, as expected from component reconnection. In addition, our observations do not reveal any thickening of the boundary layer down the flanks, the plasma boundary layer being confined to the reconnecting magnetopause current layer. This suggests that reconnection dominates over diffusive entry or Kelvin‐Helmholtz instability at the low latitude magnetopause even when the IMF clock angle is 90°.