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Please use this identifier to cite or link to this item: http://hdl.handle.net/2248/5838

Title: Helicity Constrained Model of a Galactic Dynamo
Authors: Avijeet Prasad
Issue Date: Jun-2010
Publisher: Indian Institute of Astrophysics
Citation: M.Sc. Thesis, School of Sciences, Indira Gandhi National Open University (IGNOU), New Delhi
Abstract: Magnetic fields correlated on kiloparsec scales are seen in disc galaxies. The origin could be due to amplification of small scale seed fields by a turbulent dynamo. Helicity conservation imposes constraints on dynamo action and one can study the minimal field strength of the large scale magnetic field that could arise despite the constraint. The calculation of helicity is technically complicated because of open boundaries and the usual form for the MHD invariant needs to be modified to take this into account. A general formalism has been developed to calculate the field strength using a quasi-linear dynamo model. As a first step, a galactic disk dynamo model has been built analytically while making the usual assumptions of shear and the alpha effect. We find quadrupolar solutions that are matched to a vacuum field with D = 11. The general approach to solving the quasi-linear dynamo using the full set of relative helicity boundary conditions are described
Description: Thesis Supervisor Prof. Arun Mangalam
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URI: http://hdl.handle.net/2248/5838
Copyright: © Indian Institute of Astrophysics
Appears in Collections:Integrated M.Sc-Ph.D

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