[1] Taras Shevchenko Natl Univ Kyiv, 60 Volodymyrska St, UA-01601 Kiev, Ukraine
[2] Natl Acad Sci Ukraine & State Space, Space Res Inst, 40 Glushkov Ave 4-1, UA-03680 Kiev, Ukraine
[3] Univ Sheffield, Sch Math & Stat, Plasma Dynam Grp, Sheffield, England
[4] Ludwig Maximilians Univ Munchen, Geophys Dept Earth & Environm Sci, Munich, Germany