The AMICIST auroral sounding rocket: A comparison of transverse ion acceleration mechanisms

Recent auroral sounding rocket data illustrate the relative significance of two transverse acceleration of ion (TAI) mechanisms for initiating nightside auroral ion outflow. First, the new data from this two payload mission show clearly that for lower hybrid solitary wave events, a) these individual events are spatially localized to scales approximately 100 m wide perpendicular to B, and b) the probability of occurrence of the events is greatest at times of maximum VLF wave intensity. Second, ion acceleration by broadband, low frequency electrostatic waves is observed in a 30 km wide region at the poleward edge of the arc. The fluxes from this and other sounding rockets are shown to be consistent with DE‐1 and Freja outflow measurements, indicating that the AMICIST observations show the low altitude, microphysical signatures of nightside auroral outflow from TAI.