We thank Horst Balthasar for providing clarifications regarding the computation of the confidence levels and Tom Bogdan and Jürgen Staude for helpful comments. SOHO is a cooperative mission between ESA and NASA. This work has been partly supported by the Swiss National Science Fundation, grant No. 21-45083.95, and by a grant from ETH Zürich.
© European Southern Observatory (ESO) 1998
Online publication: June 26, 1998