Ca II H sunspot tomography from the photosphere to the chromosphere

¹ Institute for Solar Physics, Royal Swedish Academy of Sciences, Albanova University Center, 10691 Stockholm, Sweden
² Stockholm Observatory, Dept. of Astronomy, Stockholm University, Albanova University Center, 10691 Stockholm, Sweden
e-mail: vasco@astro.su.se

Received: 5 April 2013
Accepted: 6 July 2013

Abstract

Aims. We aim at gaining insight into the thermal properties of different small-scale structures related to sunspots.

Methods. We use filtergrams in the Ca ii H filter at the Swedish 1-m Solar Telescope to study the relationship between fine structure at different heights in a sunspot.

Results. The methods for destretching and aligning the different image data work well. The magnetic spine structure in the outer parts of the sunspot penumbra is found to be associated with higher intensities in the Ca ii H wing passbands but with less steep vertical temperature gradients. Dark lanes in a light bridge behave very similarly to dark cores in penumbral filaments. Fibril structures are seen in the line-core images over the umbra and penumbra.

Conclusions. The observations add support to the idea that penumbral filaments, light bridges, and umbral dots are caused by similar processes of overturning convection. Observations in the Ca ii H & K wings are a promising observable, complementing others, for testing simulation results for sunspots at high spatial resolution.