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The decay of the mean solar magnetic field

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Abstract

We have analyzed the effects that differential rotation and a hypothetical meridional flow would have on the evolution of the Sun's mean line-of-sight magnetic field as seen from Earth. By winding the large-scale field into strips of alternating positive and negative polarity, differential rotation causes the mean-field amplitude to decay and the mean-field rotation period to acquire the value corresponding to the latitude of the surviving unwound magnetic flux. For a latitudinally broad two-sector initial field such as a horizontal dipole, the decay is rapid for about 5 rotations and slow with a t −1/2 dependence thereafter. If a poleward meridional flow is present, it will accelerate the decay by carrying the residual flux to high latitudes where the line-of-sight components are small. The resulting decay is exponential with an e-folding time of 0.75 yr (10 rotations) for an assumed 15 m s−1 peak meridional flow speed.

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Authors and Affiliations

  1. Naval Research Laboratory, 20375-5000, Washington, DC, U.S.A.

    Neil R. Sheeley Jr. & C. Richard DeVore

Authors
  1. Neil R. Sheeley Jr.
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  2. C. Richard DeVore
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E.O. Hulburt Center for Space Research.

Laboratory for Computational Physics.

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Sheeley, N.R., DeVore, C.R. The decay of the mean solar magnetic field. Sol Phys 103, 203–224 (1986). https://doi.org/10.1007/BF00147824

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  • DOI: https://doi.org/10.1007/BF00147824

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