Dynamical Deformation of Heliospheric Current Sheet by Interplanetary Magnetic Clouds.

A significant fraction of the energies emitted by the sun is conveyed by coronal mass ejections, which are very likely to appear as interplanetary magnetic clouds in the heliosphere. The helical field lines in a magnetic cloud are kept untangled to the surrounding spiral field lines, which permeate the solar wind in the heliosphere, by a polarization current induced on the magnetic cloud's periphery. The induced current and the current carried by a passing magnetic cloud may exert large forces on the currents of heliospheric current sheet, which interfaces oppositely directed spiral field lines. Severe deformation of the heliospheric current sheet, which depends also on the latter's configuration, may change significantly the orientation of the interplanetary magnetic field in the vicinity of the passing magnetic cloud. The transitory deformation of the heliospheric current sheet may incur a large southward component in the interplanetary magnetic field. Such a southward component, when incident on the earth's magnetosphere, may trigger efficient transfer of energies from the solar wind to the magnetosphere.