The Inner Structure of STEVE-Linked SAID

We found the inner electromagnetic structure of subauroral ion drifts (SAID) in the SAID-STEVE events documented by the Swarm spacecraft and numerically simulated the ionospheric feedback instability (IFI) development for one of the four similar events. Good quantitative agreement of the modeling results with the observed features shows that the ionospheric feedback mechanism captures their basic underlying physics. Simulations require nonlinear saturation of the IFI-generated dispersive Alfven waves. That is, a strong driving field of STEVE-linked SAID with a deep density trough leads to a nonlinear system of dispersive Alfven waves coupled with the density perturbation and parallel electric fields. As shown earlier, these fields produce the suprathermal electron population and energy balance necessary for the STEVE and Picket Fence radiation. Therefore, our results predict their inner structure.