We thank K. Tsiganis and M. Georgoulis for many helpful discussions on several issues. We also thank G. Einaudi for stimulating discussions on MHD aspects of flares, and the referee A.L. MacKinnon for useful comments. The work of H. Isliker was partly supported by a grant of the Swiss National Science Foundation (NF grant nr. 8220-046504).
© European Southern Observatory (ESO) 2000
Online publication: December 5, 2000