Click here to view fulltext PDF

Permanent link:
https://www.ias.ac.in/article/fulltext/pram/061/04/0707-0724

Dynamo; magnetohydrodynamic turbulence; field theory

Renormalized viscosity, renormalized resistivity, and various energy fluxes are calculated for helical magnetohydrodynamics using perturbative field theory. The calculation is of firstorder in perturbation. Kinetic and magnetic helicities do not affect the renormalized parameters, but they induce an inverse cascade of magnetic energy. The sources for the large-scale magnetic field have been shown to be (1) energy flux from large-scale velocity field to large-scale magnetic field arising due to non-helical interactions and (2) inverse energy flux of magnetic energy caused by helical interactions. Based on our flux results, a primitive model for galactic dynamo has been constructed. Our calculations yield dynamo time-scale for a typical galaxy to be of the order of 10⁸ years. Our field-theoretic calculations also reveal that the flux of magnetic helicity is backward, consistent with the earlier observations based on absolute equilibrium theory.

Mahendra K Verma¹

1. Department of Physics, Indian Institute of Technology, Kanpur - 208 016, India

Published

October 2003

Manuscript received

21 October 2002

Manuscript revised

25 June 2003

Accepted

3 July 2003