Asymmetric Magnetic Reconnection in the Earth's Magnetosphere: Basic Theory and Kinetic Signatures (Invited)

Asymmetric magnetic reconnection has become the focus of intense study in recent years due to its applicability to the dayside magnetosphere, the solar wind and corona, turbulent systems in general, and laboratory plasmas. The study of this asymmetric reconnection is particularly timely owing to the launch of the Magnetospheric Multiscale Mission (MMS) next year, which will focus on dayside reconnection in the first phase of its mission. To put these observations in context, it is important to understand how asymmetric magnetic reconnection will warp diffusion region properties at both the ion and electron kinetic scales. Multiple case studies using both simulations and observations have shown that the Hall diffusion region structures are substantially modified during asymmetric reconnection, with the quadrupolar Hall magnetic field becoming bipolar, and the bipolar Hall electric field becoming unipolar. After reviewing the basic properties of the diffusion region during asymmetric reconnection, we will present results from a systematic kinetic-PIC simulation study of a wide range of asymmetric inflow conditions. The separation of the stagnation point and the x-line appears to play a primary role in the warping of kinetic signatures of the diffusion region and also gives rise to purely kinetic structures not present in a fluid description of reconnection. Signatures which may aid the observational search for the electron and ion diffusion regions will be discussed.