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Title: Fine-scale magnetic features in the solar Atmosphere
Authors: Pradeep Chitta, L
Issue Date: Jun-2014
Publisher: Indian Institute of Astrophysics
Citation: Ph.D. Thesis, Pondicherry University, Puducherry
Abstract: The surface of the Sun and solar-type stars is permeated by magnetic fields with a variety of spatial and temporal scales. The spatial scales range from sub-arcsec tangled fields that are yet to be observed (inaccessible to the current instruments) to tens and hundreds of megameters large active regions. The time scales have equally broad spectrum ranging from less than a minute (for small-scale activities) to months (large active regions). These magnetic fields and their activity play a dominant role in the solar atmosphere and govern the space weather. Furthermore, understanding the solar magnetism, its generation, and its interactions act as templates to such phenomena in the large scales. It is generally thought that a solar dynamo process at the base of the convective zone is responsible for the generation of active regions in the Sun. There exists a magnetic cycle, with the global field of the Sun, oscillating between a predominantly poloidal to toroidal field with a period of 11 years. Rooted in the convective zone below the photosphere, the magnetic field buoyantly rises through the solar atmosphere. The granular motions continually jostle the magnetic field which lead to magnetic stress and magnetic waves. This interplay between the convective motions and magnetic field holds the key to understand the dynamical solar atmosphere, and coronal heating. High spatio-temporal resolution observations of the Sun reveal a facet of the solar magnetism that is highly intermittent and dynamic. This magnetic field extends well beyond the active regions and covers the entire surface of the Sun. Mainly observed at the boundaries of supergranular cells and in the intergranular lanes, these magnetic fields are known to be responsible for the myriad of structures and phenomena that are observed in the solar atmosphere. The typical length scale of this magnetic field, at the photosphere, range from less than a hundred kilometers to a few megameters. With a magnetic flux of 1016 − 1020 Mx, these are seen as thin bright flux tubes and dark pores in the intensity images. In this dissertation I study the dynamics of magnetic field, particularly, in the quiet Sun, from photosphere to corona. This work can be broadly divided into two parts. (i) Studying the dynamics of magnetic field at the photosphere. This aspect deals with the interactions between convective motions and magnetic field using high resolution observations: (a) acoustic waves and magnetic field interactions, (b) horizontal motions and dynamics of the solarmagnetic bright points. (ii)Magnetic coupling and the heating of solar atmosphere. Topics of flux emergence and magnetic carpet are explored in this part: (a) hydrodynamic modeling of the coronal response to ephemeral regions in terms of temperature fluctuations and differential emission measure are studied in detail, (b) using the time sequence of high resolution line-of-sight (LOS) magnetograms as lower boundary conditions, three-dimensional (3D) magnetic modeling is performed to understand the role of the magnetic carpet in the heating of solar corona.
Description: Thesis Supervisor Prof. R. Kariyappa
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Appears in Collections:IIAP Ph.D.Theses

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