Because the magnetopause boundary separates a region of relatively strong magnetic field (the magnetosphere) from a region of relatively weak magnetic field (the magnetosheath), the boundary must carry a surface current to ensure force balance across the boundary. This magnetopause current flows differently on the day side and night side of the Earth.
The magnetopause current encircling the magnetotail lobes closes through the middle of the tail in a neutral sheet current that separates the oppositely directed magnetic fields in the two tail lobes.
Part of the dayside magnetopause current closes on the magnetopause and part closes via Region 1 field-aligned currents in the ionosphere. The ring current lies in the inner part of the plasma sheet, where ions and electrons drift in opposite directions around the Earth. This ring current encircles the Earth and is not uniform, with the stronger current flowing on the night side of the Earth. The ring current closes partially within the magnetosphere and partially through ionospheric currents via Region 2 field-aligned currents.
Ionospheric closing currents comprise both Hall and Pedersen currents. Pedersen currents flow parallel to the electric field and perpendicular to the magnetic field, while Hall currents flow perpendicular to both fields. If the ionospheric conductivity were uniform, then the closing would be accomplished solely by Pedersen currents, but conductivity gradients do generally exist so there is a closing contribution from Hall currents.
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