Ionospheric Footprints of Detached Magnetotail Interchange Heads

Pritchett and Coroniti (2011, https://doi.org/10.1029/2011GL047527, 2013, https://doi.org/10.1029/2012JA018143) have predicted that the kinetic ballooning/interchange instability (BICI) can provoke reconnection onsets that lead to detached azimuthally thin earthward intrusions (heads) of depleted plasma tubes when beta(eq) <= 100. Such detached BICI heads would be seen as localized earthward-propagating dipolarization fronts. Using Time History of Events and Macroscale Interactions during Substorms observations in the plasma sheet at X-GSM approximate to -11R(E) and conjugate All-Sky Imager and magnetometer networks observations on the ground, we show four examples when prominent dipolarization fronts with moderate earthward flows were observed amidst azimuthally drifting interchange heads and concurrently with the ionospheric current intensifications near Time History of Events and Macroscale Interactions during Substorms footprints and auroral bright spots originating from dimmer azimuthal beads/rays. These events support the idea that some of the BICI heads detach from the region with reversed radial gradient of B-Z due to local reconnection. The detached BICI heads propagate earthward-driving ionospheric pseudo-breakups. Plain Language Summary The Earth's magnetotail periodically accumulates energy in form of the magnetic flux in the tail lobes and dumps the energy as fast earthward and tailward plasma flows, which are produced by magnetic reconnection. Yet there is no consensus on what magnetotail processes may lead to reconnection. Examples of multiprobe space observations are used to reveal the possible process that might be important for azimuthally localized reconnection in the tail that leads to pseudo-breakups in aurora and local ionospheric current systems. The examples show the appearance of earthward-propagating reconnection (dipolarization) fronts amidst azimuthally propagating clumps of more dipolar field lines that were produced by an instability which was predicted to lead to localized reconnection by earlier plasma computer simulations. The conjugate ground auroral and magnetic field observations support the reconnection fronts' origin hypothesis.