Anti‐Parallel Reconnection at the Dayside Magnetopause: Ionospheric Signatures and Implications for the Low Latitude Boundary Layer

Reconnection at the dayside magnetopause is of fundamental importance in determining the dynamics and composition of the magnetosphere and the high latitude ionosphere. There are two competing hypotheses for such reconnection, sub-solar and anti-parallel. In this paper, evidence is provided that suggests that anti-parallel reconnection occurs, at least under some circumstances. Some of the consequences of anti-parallel reconnection are considered. These include the absence of a low latitude boundary layer during southward IMF, the relative timing of reconnection events as observed in the ionosphere, the time-dependence of ion outflow and the implications for the composition of the magnetosheath, and the transient nature of reconnection. Some suggestions for tests that would allow differentiation between the anti-parallel and sub-solar reconnection are also made.