Modelling of interplanetary magnetic clouds evolution.

In this work, we study changes of magnetic cloud shapes on their travel from the solar corona to the Earth’s orbit. Magnetic field at the origin of the cloud is determined from WSO source surface maps. Velocity of ambient solar wind is approximated by Parker’s formula adjusted for interplanetary plasma measurements at 1 AU. Solar wind density profile is set to satisfy flow continuity requirement. The cloud expands once the total ambient pressure decreases on its motion. There are two constrains for the expansion: conservation of total magnetic energy density inside the magnetic cloud and conservation of the magnetic flux at the boundary of the cloud. Our model leads to the dependence of minor and major radii of the cloud to the helio-distance. We will show typical profiles for fast and slow magnetic clouds observed in 1998-2001.