Authors: Yi Qi (Laboratory for Atmospheric and Space Physics, Boulder, CO, United States) , Robert Ergun(Laboratory for Atmospheric and Space Physics, Boulder, CO, United States), Neha Pathak (Laboratory for Atmospheric and Space Physics, Boulder, CO, United States), Tak Chu Li (Department of Physics and Astronomy, Dartmouth College, Hanover, NH, United States), Stefan Eriksson (Laboratory for Atmospheric and Space Physics, Boulder, CO, United States), Alexandros Chasapis (Laboratory for Atmospheric and Space Physics, Boulder, CO, United States), Steven J Schwartz (Imperial College London, London, United Kingdom), Narges Ahmadi (Laboratory for Atmospheric and Space Physics, Boulder, CO, United States), Tien Vo (Laboratory for Atmospheric and Space Physics, Boulder, CO, United States), David Newman (Laboratory for Atmospheric and Space Physics, Boulder, CO, United States), Maria Usanova (Laboratory for Atmospheric and Space Physics, Boulder, CO, United States), Frederick D Wilder (University of Texas at Arlington, Arlington, TX, United States), and Jason Shuster (University of Maryland College Park, College Park, MD, United States)

Magnetic reconnection is a fundamental plasma process that has been studied with analytical theory, numerical simulations, in-situ observations, and laboratory experiments for decades. The models that have been established to describe magnetic reconnection often assume a reconnection plane normal to the current sheet in which anti-parallel magnetic field annihilates. The annihilation points, also known as the X-points, form an x-line, which is believed to be perpendicular to the reconnection plane. Recently, a new study (Pathak et al. 2022) using the Magnetospheric Multiscale (MMS) mission observations has challenged our understanding of magnetic reconnection by providing evidence that the x-line is not necessarily orthogonal to the reconnection plane. In this study we report a second nonorthogonal x-line event with similar features as that in the previous case study, supporting that the sheared x-line phenomenon is not an aberrant event. We employ a detailed directional derivative analysis to identify the x-line direction and show that the in-plane reconnection characteristics are well maintained even with a nonorthogonal x-line. In addition, we find the x-line tends to follow the magnetic field on one side of the current sheet, which suggests an asymmetry across the current sheet. We discuss the possibility that the nonorthogonal x-line arises from an interplay between the two aspects of reconnection: the macroscopic magnetic field topology and microscopic particle kinetics.