Outstanding Questions and Future Research on Magnetic Reconnection

Abstract

This short article highlights 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.

Keywords: Cross-scale; Diffusion region; Energetics; Magnetic reconnection; Magnetospheric Multiscale (MMS) mission; Onset.

Fig. 1

Reconnection in geospace. In addition to global dayside and nightside magnetic reconnection, recent in-situ measurements and simulations have revealed 3D, complex, and localized reconnection features throughout geospace. (a-f) Examples of different types of reconnection that are actively studied in the MMS era. (g) 3D view of the magnetosphere from an MHD model (Credit: V. G. Merkin) adapted from Sitnov et al. (2016), where several key mesoscale processes KHI, BBF/DF and FTE related to localized reconnections are indicated. The highlighted reconnection features are: (a) secondary and/or multiple reconnection at the magnetopause (adapted from Øieroset et al. 2016), (b) turbulent reconnection in the shock transition region (adapted from Bessho et al. 2022), (c-d) 3D multiscale KHI/KHV induced reconnection (adapted from (c) Nakamura et al. and (d) Faganello et al. 2012), (e) structured and disturbed EDR in the magnetotail current sheet (adapted from Cozzani et al. 2021) and (f) transient and localized reconnection at the dipolarization front (adapted from Hosner et al. 2024)