Implications of a strongly peaked polar magnetic field |
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| Authors: | N R Sheeley Jr Y -M Wang C R DeVore |
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| Institution: | (1) E.O. Hulburt Center for Space Research, U.S.A.;(2) Laboratory for Computational Physics and Fluid Dynamics, U.S.A.;(3) Naval Research Laboratory, 20375-5000 Washington, D.C., U.S.A. |
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| Abstract: | Using the flux-transport equation in the absence of sources, we study the relation between a highly peaked polar magnetic field and the poleward meridional flow that concentrates it. If the maximum flow speed 
m greatly exceeds the effective diffusion speed  /R, then the field has a quasi-equilibrium configuration in which the poleward convection of flux via meridional flow approximately balances the equatorward spreading via supergranular diffusion. In this case, the flow speed ( ) and the magnetic field B() are related by the steady-state approximation ()  (/R)B ()/B() over a wide range of colatitudes from the poles to midlatitudes. In particular, a general flow profile of the form sin
p
cos
q
which peaks near the equator (q  p) will correspond to a cos
n
magnetic field at high latitudes only if p = 1 and
m = n /R. Recent measurements of n  8 and 600 km2 s–1 would then give
m 7 m s–1. |
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