[1] Univ Leicester, Dept Phys & Astron, Radio & Space Plasma Phys Grp, Leicester, Leics, England
[2] European Space Agcy, ESTEC Sci Support Off, Noordwijk, Netherlands
[3] Inst Rech Astrophys & Planetol, Toulouse, France
[4] Ist Nazl Astrofis INAF, IAPS, Rome, Italy
[5] Abdus Salam Int Ctr Theoret Phys ICTP, Telecommun ICT Dev Lab, Str Costiera 11, I-34151 Trieste, Italy
[6] Univ Complutense Madrid, Dept Fis Tierra Astron & Astrofis 1, E-28040 Madrid, Spain
[7] UCM, CSIC, Inst Geociencias, Madrid, Spain