Affiliation: | Centre for Plasma Astrophysics, Department of Mathematics, K. U. Leuven, Celestijnenlaan 200B, Leuven 3001, Belgium;S. N. Bose National Centre for Basic Sciences, JD Block, Sector-III, Salt Lake, Kolkata 700098, India;Centre for Space Physics, P61, Southend Garden, Calcutta 700084, India |