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Indian Institute of Science

1. Chatterjee, Piyali. Understanding The Solar Magnetic Fields :Their Generation, Evolution And Variability.

Degree: PhD, Faculty of Science, 2010, Indian Institute of Science

The Sun, by the virtue of its proximity to Earth, serves as an excellent astrophysical laboratory for testing our theoretical ideas. The Sun displays a plethora of visually awe-inspiring phenomena including flares, prominences, sunspots, corona, CMEs and uncountable others. It is now known that it is the magnetic field of the Sun which governs all these and also the geomagnetic storms at the Earth, which owes its presence to the interaction between the geomagnetic field and the all-pervading Solar magnetic field in the interplanetary medium. Since the solar magnetic field affects the interplanetary space around the Earth in a profound manner, it is absolutely essential that we develop a comprehensive understanding of the generation and manifestation of magnetic fields of the Sun. This thesis aims at developing a state-of-the-art dynamo code SURYA1taking into account important results from helioseismology and magnetohydrodynamics. This dynamo code is then used to study various phenomenon associated with solar activity including evolution of solar parity, response to stochastic fluctuations, helicity of active regions and prediction of future solar cycles. Within last few years dynamo theorists seem to have reached a consensus on the basic characteristics of a solar dynamo model. The solar dynamo is now believed to be comprised of three basic processes: (i)The toroidal field is produced by stretching of poloidal field lines primarily inside the tachocline – the region of strong radial shear at the bottom of the convection zone. (ii) The toroidal field so formed rises to the surface due to magnetic buoyancy to form active regions. (iii) Poloidal field is generated at the surface due to decay of tilted active regions – an idea attributed to Babcock (1961) & Leighton (1969). The meridional circulation then carries the poloidal field produced near the surface to the tachocline. The profile of the solar differential rotation has now been mapped by helioseismology and so has been the poleward branch of meridional circulation near the surface. The model I describe in this thesis is a two-dimensional kinematic solar dynamo model in a full sphere. Our dynamo model Surya was developed over the years in stages by Prof. Arnab Rai Choudhuri, Dr. Mausumi Dikpati, Dr. Dibyendu Nandy and myself. We provide all the technical details of our model in Chap. 2 of this thesis. In this model we assume the equatorward branch of the meridional circulation (which hasn’t been observed yet), to penetrate slightly below the tachocline (Nandy & Choudhuri 2002, Science, 296, 1671). Such a meridional circulation plays an important role in suppressing the magnetic flux eruptions at high latitudes. The only non-linearity included in the model is the prescription of magnetic buoyancy. Our model is shown to reproduce various aspects of observational data, including the phase relation between sunspots and the weak, efficient. An important characteristic of our code is that it displays solar-like dipolar parity (anti-symmetric toroidal fields across… Advisors/Committee Members: Choudhuri, Arnab Rai (advisor).

Subjects/Keywords: Solar Magnetic Field; Magnetism (Astrophysics); Helioseismology; Solar Dynamo Models; Solar Oscillations; Helicity; Solar Dynamo Theory; Stochastic Fluctuations; Mean Field Dynamo Model; Magnetic Flux Tube; Poloidal Field Accretion; Dynamo Model SURYA; Astrophysics

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Chatterjee, P. (2010). Understanding The Solar Magnetic Fields :Their Generation, Evolution And Variability. (Doctoral Dissertation). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/657

Chicago Manual of Style (16th Edition):

Chatterjee, Piyali. “Understanding The Solar Magnetic Fields :Their Generation, Evolution And Variability.” 2010. Doctoral Dissertation, Indian Institute of Science. Accessed December 03, 2020. http://etd.iisc.ac.in/handle/2005/657.

MLA Handbook (7th Edition):

Chatterjee, Piyali. “Understanding The Solar Magnetic Fields :Their Generation, Evolution And Variability.” 2010. Web. 03 Dec 2020.

Vancouver:

Chatterjee P. Understanding The Solar Magnetic Fields :Their Generation, Evolution And Variability. [Internet] [Doctoral dissertation]. Indian Institute of Science; 2010. [cited 2020 Dec 03]. Available from: http://etd.iisc.ac.in/handle/2005/657.

Council of Science Editors:

Chatterjee P. Understanding The Solar Magnetic Fields :Their Generation, Evolution And Variability. [Doctoral Dissertation]. Indian Institute of Science; 2010. Available from: http://etd.iisc.ac.in/handle/2005/657

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