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Magnetic feature tracking, what determines the speed?

Published online by Cambridge University Press:  05 July 2012

Gustavo Guerrero ,
Matthias Rheinhardt  and
Mausumi Dikpati
Gustavo Guerrero
Affiliation:
Solar Physics, HEPL, Stanford University, Stanford, CA, 94305-4085, USA email: gag@stanford.edu NORDITA, Roslagstullsbacken 17, Stockholm, Sweden
Matthias Rheinhardt
Affiliation:
Department of Physics, FI-00014 University of Helsinki, Finland email: rheinhar@mappi.helsinki.fi NORDITA, Roslagstullsbacken 17, Stockholm, Sweden
Mausumi Dikpati
Affiliation:
High Altitude Observatory, NCAR, Boulder, CO, 80301, USA email: dikpati@ucar.edu
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Abstract

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Recent observations revealed that small magnetic elements abundant at the solar surface move poleward with a velocity which seems to be lower than the plasma velocity U. Guerrero et al. (2011) explained this discrepancy as a consequence of diffusive spreading of the magnetic elements due to a positive radial gradient of |Uθ|. As the gradient's sign (inferred by local helioseismology) is still unclear, cases with a negative gradient are studied in this paper. Under this condition, the velocity of the magnetic tracers turns out to be larger than the plasma velocity, in disagreement with the observations. Alternative mechanisms for explaining them independently are proposed. For the turbulent magnetic pumping it is shown that it has to be unrealistically strong to reconcile the model with the observations.

Keywords

Sun: activitySun: magnetic fields
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 7 , Symposium S286: Comparative Magnetic Minima: Characterizing quiet times in the Sun and Stars , October 2011 , pp. 70 - 74
Copyright
Copyright © International Astronomical Union 2012

References

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