Context: The common ﬂare scenario comprises an acceleration site in the corona and particle transport to the
chromosphere. With the currently available satellites it has become possible to disentangle the two processes of acceleration and transport and study the particle propagation in ﬂare loops in detail, as well as compare them to theory.
Aims: The goal of this work is a quantitative comparison of ﬂare hard X-ray spectra observed with RHESSI to theoretical predictions. This allows to distinguish acceleration from transport and to explore the nature of transport effects.
Methods: Data from the RHESSI satellite have been used both in full sun spectroscopy as well as in imaging spectroscopy. Coronal source and footpoint spectra of well observed limb events were analyzed and quantitatively compared to theoretical predictions. New concepts are introduced to existing models in order to solve the discrepancy between the observations and predictions.
Results: The standard thin-thick target solar ﬂare model cannot explain the observations in all events. In the here presented events, propagation effects in the form of non-collisional energy loss are of importance to explain the observations. We show that those energy losses can be interpreted by an electric ﬁeld in the ﬂare loop. One event suggests particle propagation or acceleration in lower than
average density in the coronal source.
Conclusions: We ﬁnd observational evidence for an electric ﬁeld in ﬂare loops caused by return currents.
Authors: Marina Battaglia, Arnold O. Benz
Publication Status: A&A, in press
Last Modified: 2008-06-11 00:47