Magnetic structure of the boundary layer

It now appears that magnetospheric convection is driven by both magnetic reconnection and ‘viscous’ dragging of closed flux tubes acting in varying proportions but with reconnection being, on the average, the predominant cause. But the action of the closed flux tubes of the low latitude boundary layer seems predominant in driving system 1 field aligned currents and discrete auroras. A search of ISEE boundary layer data for the magnetic shear effects associated with field aligned currents has revealed, on some occasions, a ‘reverse draping’ of boundary layer field lines whose cause might be plasma entry around the cusps, a north-south asymmetry in current flow to the polar regions, or magnetic reconnection at high latitudes. Observed asymmetries in the nature and distribution of boundary layer encounters suggest that the boundary layer and/or the plasma mantle may differ substantially at the dawn and dusk sides of the magnetosphere and that there may be seasonal dependencies of their properties.