A Nonlinear Force-Free Field Model to Reconstruct the Sun's Coronal Magnetic Fields

Gupta, Manu (2019) A Nonlinear Force-Free Field Model to Reconstruct the Sun's Coronal Magnetic Fields. Masters thesis, Indian Institute of Science Education and Research Kolkata.

PDF (MR dissertation of Manu Gupta (17MR003)) 17MR003.pdf - Submitted Version Restricted to Repository staff only Download (4MB)

Abstract

Sun is a magnetically active star. Magnetic activity of the Sun has a significant impact on Earth as intense solar eruptions like flares and coronal mass ejections (CMEs) can cause disturbances in our telecommunication systems, degradation of satellites, power cutoffs, and pose a danger of life-threatening radiation for astronauts. The magnetic field in solar corona plays a major role in these solar eruptions. The free (non-potential) energy stored in coronal magnetic fields determines the occurrence and intensity of these outbursts from the Sun. So, studying the magnetic field in corona is essential to understand the origin and evolution of these eruptive phenomena. At present, it difficult to directly measure the vector magnetic field in the corona through observations, therefore computational models are required to study the coronal magnetic fields. In this thesis, a Nonlinear Force-Free Field (NLFFF) model is developed in spherical geometry to study the magnetic field structures in the solar corona. This model is based on extrapolation techniques utilizing the vector magnetic field measurements of the solar photosphere (visible surface of the Sun). The model reconstructs magnetic field for solar corona that is in a force-free equilibrium state. We evaluate the quality of reconstruction of the coronal magnetic fields obtained from the NLFFF model by comparing it with the configuration given by an analytical solution. We consider two such cases, and the associated results are presented in this thesis in the context of model validation.

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