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02 November 2024 

   

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Kinetic and magnetic alpha effects in nonlinear dynamo theory  Sharanya Sur
; Kandaswamy Subramanian
; Axel Brandenburg
;  Date: 
2 Jan 2007  Abstract:  The backreaction of the Lorentz force on the alphaeffect is studied in the limit of small magnetic and fluid Reynolds numbers, using the first order smoothing approximation (FOSA) to solve both the induction and momentum equations. Both steady and time dependent forcings are considered. In the low Reynolds number limit, the velocity and magnetic fields can be expressed explicitly in terms of the forcing function. The nonlinear alphaeffect is then shown to be expressible in several equivalent forms in agreement with formalisms that are used in various closure schemes. On the one hand, one can express alpha completely in terms of the helical properties of the velocity field as in traditional FOSA, or, alternatively, as the sum of two terms, a socalled kinetic alphaeffect and an oppositely signed term proportional to the helical part of the small scale magnetic field. The latter alternative is similar to the formulation in other closure schemes (abridged).  Source:  arXiv, astroph/0701001  Services:  Forum  Review  PDF  Favorites 


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