Azimuthal Variation of Magnetopause Reconnection at Scales Below an Earth Radius

Abstract

AbstractWhile magnetopause reconnection naturally occurs in three‐dimensional environments, our understanding of the process has been mainly confined to the two‐dimensional reconnection plane. How reconnection varies in the third direction, that is, the azimuthal direction, and what causes the variation remain open questions. We study the azimuthal variation of reconnection at an underexplored scale, which is below an Earth radius, using THEMIS spacecraft. Our results show that reconnection jets transition from being present to absent within tenths of a RE, corresponding to tens of ion inertial lengths. The absence of jets cannot be explained by an ion or electron diffusion region, or a magnetic flux rope flanked by two reconnection sites. The sharp transition of reconnection is associated with spatially varying waves. No drivers of the transition are identified locally at the magnetopause or in the upstream, implying that reconnection may naturally have a finite extent at certain stages of its development.