Outstanding Questions and Future Research on Magnetic Reconnection

Magnetic reconnection is a fundamental energy conversion process in plasmas. While

changes in the topology of the magnetic field take place inside a small region, acceleration  and heating of the plasma are distributed over larger scales. Acceleration and heating drive plasma transport and lead to explosive magnetic energy release likewise on large scales during phenomena such as substorms, solar flares, and  possibly gamma ray bursts. With modern space  technology, geospace is an ideal plasma laboratory for studying how collisionless magnetic reconnection operates in nature since plasmas and fields in action can be directly measured at high cadence. With the advanced in-situ measurement capability to resolve electron-scale physics, the four Magnetospheric Multiscale (MMS) spacecraft  have significantly advanced the study of magnetic reconnection and relevant plasma processes.  In this presentation we highlight unsolved problems of magnetic reconnection in collisionless plasma. Advanced in-situ plasma measurements and simulations have enabled scientists to gain a novel understanding of magnetic reconnection. Nevertheless, outstanding questions remain concerning the complex dynamics and structures in the diffusion region, cross-scale and regional couplings, the onset of magnetic reconnection, and the details of particle energization. We discuss future directions for magnetic reconnection research, including new  observations, new simulations, and interdisciplinary approaches.