Commonalities between Auroral Arcs and Solar Flares.

Abstract:

  The auroral energy conversion process is compared with its potential realization in the sun during flares. Emphasis is placed on the major similarities and differences between the two. In both cases the energy consumed in accelerating electrons (and ions) is derived from the release of magnetic shear stresses. Secondly, spontaneous propagation of this process is a basic property of both cases. A major difference exists with regard to the spatial and time scales. Because of the high density of the corona in comparison with that of the magnetosphere, they are extremely short. This implies the need for extremely high field-aligned current densities and that the energy conversion process would involve some kind of anomalous resistivity. The energy conversion fronts on the sun would propagate not only transversely to the shear direction but also along the magnetic field. Because of the obliqueness of the fronts, there is no return current problem for the emerging runaway electrons. The described process would most likely be realized just above the transition region and is seemingly in conflict with time-of-flight data indicating acceleration above the loop-top, albeit only for 10% of the observed hard X-ray fluxes.