DYNAMICAL DEFORMATION OF HELIOSPHERIC CURRENT SHEET BY INTERPLANETARYMAGNETIC CLOUDS

A significant fraction of the energies emitted by the sun is conveyed by coronal mass ejections, which are very likely to appear as interpla netary magnetic clouds in the heliosphere. The helical field lines in a magnetic cloud are kept untangled to the surrounding spiral field li nes, which permeate the solar wind in the heliosphere, by a polarizati on current induced on the magnetic cloud's periphery. The induced curr ent and the current carried by a passing magnetic cloud may exert larg e forces on the currents of heliospheric current sheet, which interfac es oppositely directed spiral field lines. Severe deformation of the h eliospheric current sheet, which depends also on the latter's configur ation, may change significantly the orientation of the interplanetary magnetic field in the vicinity of the passing magnetic cloud. The tran sitory deformation of the heliospheric current sheet may incur a large southward component in the interplanetary magnetic field. Such a sout hward component, when incident on the earth's magnetosphere, may trigg er efficient transfer of energies from the solar wind to the magnetosp here.