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Photospheric Flux Changes and the MHD Approximation

Published online by Cambridge University Press:  25 April 2016

P. R. Wilson
P. R. Wilson*
Affiliation:
Department of Applied Mathematics, University of Sydney
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Extract

The rate of change of magnetic flux Ф contained within a closed curve C moving with the plasma velocity u, is given by

where B is the magnetic induction and S is a surface bounded by the curve C. Using the hydromagnetic equation,

where η is the magnetic diffusivity, this becomes

In many astrophysical contexts η is small and thus approximately

Since this implies that the flux within any moving closed curve does not change, the field is said to be ‘frozen into’ the plasma and moving with it.

Type
Contributions
Information
Publications of the Astronomical Society of Australia , Volume 5 , Issue 4 , 1984 , pp. 500 - 502
Copyright
Copyright © Astronomical Society of Australia 1984

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References

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