Magnetic reconnection, a universal process occurring across plasma regimes, is of fundamental importance to many phenomena, but is yet to be fully understood. Major progress in understanding fast reconnection onset requires coordinated efforts among all relevant researchers. We call for contributions to address this topic through theoretical, observational, and experimental investigations. Specific subject areas include, but are not limited to, current sheet thinning, instabilities, flare and nanoflare morphology/energetics, dayside magnetopause reconnection, magnetotail current sheet and reconnection, and basic numerical simulation studies. Given the concurrent community-wide efforts in addressing the challenging problems centered around magnetic reconnection, it is timely to call upon a wider participation, and to provide a forum for wider dissemination of knowledge and current understanding, in order to better facilitate a focused team effort in elucidating the science question on fast reconnection onset.

• SM - SPA-Magnetospheric Physics