The sketch at the right and the one below illustrate the flow of charged particles in the equatorial plane of the magnetosphere. The interaction of the solar wind with the magnetosphere (through reconnection and viscous processes) results in a bulk flow of plasma down the magnetotail. This flow is referred to as "convection," although this term is really a misnomer because convection is a thermal process and the flow of plasma is not, being governed instead by large-scale electric and magnetic fields. In the plasma sheet, the direction of the convective flow is sunward, perpendicular both to the direction of the Earth's magnetic field (out of the screen) and to the direction (dawn-to-dusk) of the electric field imposed on the magnetosphere by the solar wind interaction. (The motion of the plasma perpendicular to both the electric and magnetic fields is known as "E-cross-B drift.") As coupling between the solar wind and the magnetosphere intensifies, sunward convection increases, and the boundary separating the convective and co-rotational flow regimes (known as the "separatrix") moves inward, freeing some of the plasma previously bound on "closed" Earth-encircling trajectories to follow "open" convective paths toward the dayside magnetopause. Weakening of convection enlarges the region of near-Earth plasma that co-rotates with the Earth and allows the magnetic field lines emptied of plasma during periods of high convection to refill.

Figures adapted from: Brice, N. M., Bulk motion of the magnetosphere, J. Geophys. Res., 72, 5193, 1967; and Kavanaugh, L. D., Jr. et al., Plasma flow in the magnetosphere, J. Geophys. Res., 73, 5511,1968.