Hashem Hamedivafa

[ 1 ] - The dependence of the magnetic field strength of a sunspot umbra on its intensity and brightness temperature

A partial decrease of the convective energy by the magnetic field of a sunspot causes the temperature of the magnetized plasma to decrease and this leads to a magneto-hydrostatic equilibrium. Thus, we expect a strong relation between magnetic field strength of a sunspot and its temperature/brightness. Here, we investigate this relation in the umbra of the large sunspot in NOAA10930 using spectr...

[ 2 ] - A study on Ca II 854.2 nm emission in a sunspot umbra using a thin cloud model

In the present work, we introduce and explain a method of solution of the radiative transfer equation based on a thin cloud model. The efficiency of this method to retrieve dynamical chromospheric parameters from Stokes I profiles of Ca II 854.2 nm line showing spectral emission is investigated. The analyzed data were recorded with the Crisp Imaging Spectro-Polarimeter (CRISP) at Swedish 1-m So...

[ 3 ] - Structure of proper motions in a sunspot penumbra