21 September 2012
Venue: GO Jones Room 410
The possibility that electrons could be accelerated by inertial Alfven waves to hard X-ray-emitting energies in the low solar corona during flares is investigated theoretically. This investigation is prompted in part by recent microwave observations indicating that the coronal magnetic field is strong enough that the Alfven velocity cA above active regions could be of the order of a tenth of the speed of light or more; electrons can be accelerated to velocities in excess of cA on collisionless timescales via reflection by a single inertial Alfven wave pulse. The fraction of particles accelerated is a sensitive function of the initial electron temperature and the transverse length scale δx of the shear Alfven wave pulse; under typical pre-flare coronal conditions, a significant fraction of the electron population can be accelerated if δx is of the order of a few metres or less. Possible applications of this acceleration mechanism to non-solar astrophysical plasmas are also briefly discussed.
We will be taking the speaker to lunch at the Greedy Cow. Please gather in the G.O. Jones lobby at 12:20pm to depart together.