Studying the current sheet structure close to a reconnection point with MMS observations

Abstract:

From the classical picture of magnetic reconnection in the magnetotail, it is expected to the current sheet to have a classic Harris-type structure with a maximum current density at the magnetic equator. In-situ observations have shown that the magnetotail current sheet structure is frequently much more complicated than the simple Harris-type picture. However, the detailed current structure especially near the small-scale reconnection region in the magnetotail has not been well explored. In this work, we present a multiple reconnection event observed by the Magnetospheric Multiscale (MMS) mission on July 6, 2017, for which the structure of the current sheet as well as some of its characteristics scales are well resolved. Our results show that while reconnection occurs, the current sheet structure is highly dynamic changing from a bifurcated shape far from the reconnection site, to a more symmetric (Harris-type) structure near the X-line. Additionally, we show that the sustained presence of a guide field also deviates the current sheet structure from what is expected.