Role of interchange instability in flux transfer event origin
Abstract. It is shown that the interaction of the interplanetary magnetic field (IMF), when it has southward component, with the geomagnetic field leads to the formation of an enhanced pressure layer (EPL) near the magnetopause. Currents flowing on the boundary between the EPL and the magnetosheath prevent the IMF from penetrating the magnetosphere. However, the outward boundary of the EPL is unstable. The interchange instability permanently destroys the EPL. Separate filaments of the EPL move away from the Earth. New colder plasma of the magnetosheath with a frozen magnetic field replaces the hotter EPL plasma, and the process of EPL formation and destruction repeats itself.
The instability increment is calculated for various magnitudes of the azimuthal wave number, ky, and curvature radius of the magnetic field lines, Rc. The disturbances with R-1e≤ky≤4R-1e (where Re is the Earth's radius) and Rc≅Re are the most unstable.
A possible result of the interchange instability of the EPL may be patchy reconnection, displayed as flux transfer events (FTEs) near the magnetopause.