Field‐aligned currents as a diagnostic tool: Result, a renovated model of the magnetosphere

In the outer magnetosphere, currents across magnetic field lines are carried by protons, because of their greater energy, whereas field‐aligned currents are carried by electrons. Consequently, there is plasma enhancement or depletion on flux tubes where the two types of current connect. Thus field‐aligned currents observed at low altitudes can be used to diagnose plasma redistribution in the outer magnetosphere. A stationary current sheet accompanies convection through a stationary plasma boundary. The observations of the location and strength of field‐aligned currents are used to create a model of the currents, flows, magnetic topology and plasma distribution in the outer magnetosphere. Differences from previous models include the following: (1) A steady state flow may exist at subauroral latitudes. (2) The upward current sheet (Region 1 dusk, Harang, region II dawn) separates dipolar flux tubes from inflated taillike flux tubes. Flux tubes convecting earthward from the tail collapse to a dipolar shape as they convect through this sheet. (3) There is a significant intrusion of solar wind protons from the dawn flank into the plasma sheet between the region I and II currents.