R. Guandalini (1), M. Busso (1), S. Ciprini (2,1), G. Silvestro (3), P. Persi (4) ((1) Physics Department, University of Perugia, Italy, (2) Tuorla Observatory, University of Turku, Finland, (3) Department of General Physics, University of Torino, Italy, (4) INAF Institute of Space Astrophysics and Cosmic Physics, Roma, Italy)
