October 21, 2011, 12:00 pm - 1:00 pm

October 21, 12:00 pm - 1:00 pm

Solar Auroras

Dr. Gerhard Haerendel, Max Planck Institute for Extraterrestrial Physics, Garching, Germany

In this talk I analyze the implications of an acceleration model for solar electrons following the basic auroral mechanism. Hot plasma assembling at the loop top during flare reconnection emits Alfvén waves which carry electromagnetic energy towards the chromosphere, where it is partially absorbed and partially reflected. The absorbed fraction leads to evaporation of chromospheric matter. Interference of the reflected waves generates small-scale structures in the evaporation flow. Where the transverse scales are sufficiently narrow, currents become supercritical and subject to anomalous resistivity and dissipation. Field-parallel potential drops of tens of kV can thus be generated as the main channel to convert magnetic energy into kinetic energy of electrons and ions. The narrow energy conversion volumes expand rapidly transverse to and along the field lines extracting much of the stored energy in a matter of one second. It is postulated that thousands of such “arcs” exist simultaneously during the impulsive flare phase.