Analysis of high resolution observations of sunspots fine structures

Abstract

This Ph.D. thesis deals with the study of the interaction between plasma and magnetic fields on the Sun. Observations acquired during two observing campaigns, one at the Solar Swedish Tower and the other at the Richard B. Dunn Solar Telescope, provided high-resolution data which were used to study the details of some phenomena occurring in the Sun. In particular, this work aims to extend and consolidate our knowledge on the formation and evolution of sunspots observed in the solar photosphere. The first aspect which was investigated concerns the study of the mechanism of the penumbra formation in a sunspot. In this regard, I give my contribution in explaining the behaviour of the magnetic field forming the penumbral filaments. A second aspect concerns the study of the kinematic and magnetic properties of a light bridge separating into two parts the umbra of a sunspot. I found that there is a relationship between the upflow motions in the light bridge dark lane and the magnetic field configuration. The third aspect concerns the study of the properties of granules in a light bridge and in the quiet Sun using a new algorithm developed in collaboration with the Department of Mathematics of the University of Catania. In particular, I compared the size, mean continuum intensity and Doppler velocity between the granules forming the light bridge and those of the quiet Sun. In the conclusion, I give my interpretation of the observed phenomena and suggest future observations to confirm these results and support theoretical models.