Lambda-shaped jets from a penumbral intrusion into a sunspot umbra: A possibility for magnetic reconnection

Abstract

We present the results of high resolution co-temporal and co-spatial photospheric and chromospheric observations of sunspot penumbral intrusions. The data were 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 λ-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 λ shape of these jets suggests that they could be 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.