The chromosphere above a δ-sunspot in the presence of fan-shaped jets^⋆

Institute for Solar Physics, Department of Astronomy, Stockholm University, AlbaNova University Centre, 106 91 Stockholm, Sweden
e-mail: carolina.robustini@astro.su.se

Received: 4 July 2017
Accepted: 12 September 2017

Abstract

Context. Delta-sunspots are known to be favourable locations for fast and energetic events like flares and coronal mass ejections. The photosphere of this sunspot type has been thoroughly investigated in the past three decades. The atmospheric conditions in the chromosphere are not as well known, however.

Aims. This study is focused on the chromosphere of a δ-sunspot that harbours a series of fan-shaped jets in its penumbra. The aim of this study is to establish the magnetic field topology and the temperature distribution in the presence of jets in the photosphere and the chromosphere.

Methods. We use data from the Swedish 1m Solar Telescope (SST) and the Solar Dynamics Observatory. We invert the spectropolarimetric Fe i 6302 Å and Ca ii 8542 Å data from the SST using the non-LTE inversion code NICOLE to estimate the magnetic field configuration, temperature, and velocity structure in the chromosphere.

Results. A loop-like magnetic structure is observed to emerge in the penumbra of the sunspot. The jets are launched from this structure. Magnetic reconnection between this emerging field and the pre-existing vertical field is suggested by hot plasma patches on the interface between the two fields. The height at which the reconnection takes place is located between log τ₅₀₀ = −2 and log τ₅₀₀ = −3. The magnetic field vector and the atmospheric temperature maps show a stationary configuration during the whole observation.