Study of dynamics and magnetic field structure of the solar convective envelope using sunspot activity

Abstract

The sun which is an important part of solar system plays a significant role in influencing the life on Earth, disrupting electrical power grids, satellite and telecommunication facilities, air-traffic etc. This is due to various solar cycle and activity phenomena like sunspots, flares and CMEs taking place in the sun that also have effect on the earth’s environment and climate. So it is important to study sunspots and associated phenomena. Before the advent of space era, from surface observations, it was difficult to infer the solar internal structure and dynamics. With the help of SOHO/MDI (Michelson Doppler Imager), it is now possible to infer internal structure by computing the velocity of sound waves passing through the sun, that provide clues to unravel the secrets of sun’s eleven year cycle and associated phenomena. On the other hand MDI instruments aboard SOHO measure the line of sight component of magnetic field structure of the sun. SOT instrument on Hinode yields very high resolution longitudinal and vector magnetic field components at the photospheric levels. With the valuable data from ground based observatories and from the space observatories, from dynamics and magnetic field structure of the sunspot on the surface, now we are at a better position to understand internal structure of the convective envelope where sunspots are supposed to be originated. Hence, it is important to study sunspots’ dynamics and magnetic field structure on the surface as they are supposed to be tracers of internal dynamics and magnetic field structure of solar convective envelope. This research study consists of studying of dynamics and magnetic field structure of the solar convective envelope by using dynamics and magnetic field structure on the solar surface. The thesis has been organized as follows. The first chapter consists of introduction to solar activities like sunspot, flares and magnetic field structures associated with the sunspots. The second chapter deals with abnormal rotation rates associated with bipolar sunspots that have leader and follower. Using six years (1969-1974) of data of sunspot groups from the white light pictures of the Kodaikanal Observatory, rotation rates of the leading and the following sunspots and the rate of change of longitudinal separation during their life times are computed.