1. Department of Physics and Astronomy; University of Iowa; Iowa City Iowa USA
2. LESIA, Observatoire de Paris; Meudon Cedex France
3. Department of Geophysics, Graduate School of Science; Tohoku University; Sendai Japan
4. Physics and Astronomy; University of Leicester; Leicester UK
5. Institute of Atmospheric Physics; Prague Czech Republic
6. Faculty of Mathematics and Physics; Charles University; Prague Czech Republic