Abstract:
The thesis comprises studies on two distinctly diverse astrophysical situations; one on the outer envelope of a late-type star at its main sequence stage (solar corona), the other on the ionized cloud surrounding an early-type star at its formation stage (the HII region -- Orion Nebula). The following problems are addressed in the work; the nature of velocity fields in the solar corona and its relations to local magnetic fields and the phase of the solar cycle, the excitation mechanism of the coronal green line and its variations in different coronal regions and the kinematics of an HII region in the farthest regions from the ionizing star
