Midlatitude sub‐auroral ionospheric small scale structure during a magnetic storm

We develop a model for small scale structure in the midlatitude sub‐auroral polarization stream (SAPS)‐driven density trough ionosphere during a magnetic storm. We include the effects of ring current precipitation, parallel currents, rapid subauroral ion drifts, storm‐induced neutral winds, ion temperature and density gradients. We find that ionospheric density, electric field, ion and electron temperature irregularities can be driven in the stormtime SAPS‐driven density trough (1) wall region from the ion temperature gradient convective instability, which is driven by density and ion temperature gradients, in concert with the gradient‐drift instability and (2) central region from an ion frictional heating instability which is driven by strong ion convection.