Affiliation: | (1) Department of Physics, University of Southampton, Southampton, SO17 1BJ, UK;(2) Max-Planck-Institut für Extraterrestische Physik, Garching, D-85740, Germany;(3) Department of Physics, University of Oulu, Oulu, FIN-90570, Finland;(4) Present address: Space Sciences Laboratory, University of California, Berkeley |