Magnetic reconnection as a source of jets from a penumbral intrusion into a sunspot umbra

TL;DR

This study uses high-resolution solar observations to link transient jets in sunspot penumbral intrusions to magnetic reconnection processes, revealing detailed jet structures and their magnetic origins.

Contribution

It provides the first detailed observational evidence connecting penumbral intrusion jets to magnetic reconnection mechanisms in sunspots.

Findings

Jets extend up to 3000 km above penumbral intrusions.

Many jets exhibit a λ-shaped structure indicating magnetic reconnection.

Jets are associated with magnetic field interactions between penumbral and umbral regions.

Abstract

We present the results of high resolution co-temporal and co-spatial photospheric and chromospheric observations of sunspot penumbral intrusions. The data was taken with the Swedish Solar Telescope (SST) on the Canary Islands. Time series of Ca\,II H images show a series of transient jets extending roughly 3000 km above a penumbral intrusion into the umbra. For most of the time series jets were seen along the whole length of the intruding bright filament. Some of these jets develop a clear $\lambda$-shaped structure, with a small loop appearing at their footpoint and lasting for around a minute. In the framework of earlier studies, the observed transient $\lambda$ shape of these jets strongly suggests that they are caused by magnetic reconnection between a curved arcade-like or flux-rope like field in the lower part of the penumbral intrusion and the more vertical umbral magnetic field forming a cusp-shaped structure above the penumbral intrusion.