Momentum transfer at the high-latitude magnetopause and boundary layers

摘要

How and where momentum is transferred from the solar wind to themagnetosphere and ionosphere is one of the key problems of space physics.Much of this transfer occurs through direct reconnection on the dayside,particularly when the IMF is southward. However, momentum transfer alsooccurs at higher latitudes via Alfvén waves on old open field lines, evenfor southward IMF. This momentum is transferred to the ionosphere viafield-aligned currents (FACs), and the flow channel associated with theseFACs produces a Hall current which causes magnetic variations at highlatitude (the Svalgaard-Mansurov effect). We show examples where suchmomentum transfer is observed with multiple spacecraft and ground-basedinstruments.