Exploring magnetic reconnection with the Magnetospheric Multiscale (MMS) mission

Magnetic reconnection is a ubiquitous and fundamental process in the universe. It alters the geometry of the magnetic field and enables energy conversion between the fields and particles across multiple scales. As one of the most important topics in plasma physics, magnetic reconnection has been studied intensively over decades, but only since the launch of the Magnetospheric Multiscale (MMS) mission in 2015 we were able to investigate the kinetic and electron scale nature of reconnection with multipoint in-situ observations in the space.

MMS operates in a highly elliptical orbit and targets the prime locations of magnetic reconnections in the Earth’s magnetosphere: the dayside magnetopause and the nightside magnetotail plasma sheet. MMS has four identical spacecraft in a tetrahedron formation enabling spatial gradient analysis and the instruments on board MMS can measure the magnetic field, the electric field, as well as the three-dimensional (3D) distributions of plasma at high cadence. These outstanding features of MMS has nourished fruitful studies on reconnection, especially at the kinetic and electron scales.

In this presentation, we review the groundbreaking discoveries about reconnection in the era of MMS and introduce our latest findings on 1) the identification of active reconnection sites with the newly developed Magnetic Flux Transport (MFT) analysis, 2) the nonorthogonal x-lines phenomenon, and 3) a magnetic reconnection event with extraordinarily high particle energization in the magnetotail turbulence. These studies also open up important questions for future investigations, e.g. the 3D aspect of reconnection, the connection and interaction between reconnection and turbulence, and the connection with particle acceleration. The just finished MMS unbiased magnetosheath campaign and the upcoming large separation string-of-pearl campaign will provide us with more opportunities to deepen our understanding of reconnection.