A plasma entering the magnetosphere crosses two principal boundaries - the bow shock and magnetopause. The crossing of the bow shock significantly modifies plasma parameters as well as the direction and magnitude of the frozen-in interplanetary magnetic field (IMF) creating a key region - the magnetosheath - for a transfer of solar wind mass and momentum to the magnetosphere.
A highly turbulent magnetosheath plasma and magnetic field then interact with the magnetopause and can penetrate deeper into the magnetosphere.