Direct in situ observations of eruption-associated magnetic reconnection in the solar corona

Abstract

Magnetic reconnection is a fundamental process within highly conductive plasmas. Oppositely oriented field lines are reconfigured, releasing stored magnetic energy. It plays a vital role in shaping the dynamics of the solar corona and provides one of the main mechanisms for releasing the stored energy that powers solar eruptions. Reconnection at the Sun has been studied using remote-sensing observations, but the Parker Solar Probe (PSP) now permits in situ sampling of reconnection-related plasma in the corona. Here we report on a PSP fly-through of a reconnecting current sheet in the corona during a major solar eruption on 5–6 September 2022. We find that even 24 h after the flare peak, PSP detected the reconnection exhaust, indicating continuing fast reconnection, which we confirmed using remote-sensing observations made by the Solar Orbiter. This reconnection persisted much longer than typical timescales of a few minutes to hours. Plasma parameters measured by PSP within the reconnection region match numerical simulations. These new observations provide a key bridge between theory and measurements of plasmas in the solar atmosphere, laboratory experiments and astrophysical systems, generating new constraints required for the refinement of models and for the strengthening of their links to observations at many scales.