Small-Scale Anti-Parallel Field-Aligned Currents and Plasma Density Dips:Signatures of the″Alfvenic Shocks″ (Recent Results of Studies on Solar Terrestrial Physics Part 4)

“Electrostatic Shocks” and field-aligned currents are associated with discrete auroral arcs and low-altitude particle acceleration. We show that accounting for the two new elements with respect to the previous “static” and “Alfven wave” models, namely the transverse wave-guide for shear Alfven waves and plasma density dip in the center of the structure, is necessary in order to explain the basic features of this phenomenon. The characteristics dimensions of the structure correspond to the “stirring scales” of the auroral turbulence.