Solar photospheric albedo as a probe of angular distribution of energetic particles

E.P. Kontar, J.C. Brown

Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ, U.K.

In the ``standard model'' of solar flares, electrons are accelerated in the corona and stream downwards along magnetic field lines into the dense chromosphere where they collisionally radiate hard X-rays (HXRs). Here we present a technique which allows us to use a single HXR spectrum to determine an effectively stereoscopic electron distribution. Considering the Sun's surface to act as a ``Compton mirror'' allows us to look at emitting electrons from behind, providing vital information on downward-propagating particles. Using this technique we determine the electron spectra of two solar flares observed by RHESSI. The results reveal surprisingly near-isotropic electron distributions, which contrast strongly with the standard model with strong downward electron beaming.