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

¹ Max-Planck-Institute für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany
e-mail: bharti@mps.mpg.de
² Bal Shiksha Sadan Society, 3-Ratakhet, Udaipur, Rajsathan, India
³ School of Space Research, Kyung Hee University, Yongin, 446-701 Gyeonggi Do, Korea

Received: 5 September 2016
Accepted: 24 October 2016

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.