Bibcode
Martínez-Pillet, V.
Bibliographical reference
Space Science Reviews, Volume 178, Issue 2-4, pp. 141-162
Advertised on:
10
2013
Journal
Citations
35
Refereed citations
28
Description
Various aspects of the magnetism of the quiet sun are reviewed. The
suggestion that a small scale dynamo acting at granular scales generates
what we call the quiet sun fields is studied in some detail. Although
dynamo action has been proved numerically, it is argued that current
simulations are still far from achieving the complexity that might be
present on the Sun. We based this statement not so much on the low
magnetic Reynolds numbers used in the simulations but, above all, in the
smallness of the kinetic Reynolds numbers employed by them. It is argued
that the low magnetic Prandtl number at the solar surface may pose
unexpected problems for the identification of the observed internetwork
fields with dynamo action at granular scales. Some form of turbulent
dynamo at bigger (and deeper) scales is favored. The comparison between
the internetwork fields observed by Hinode and the magnetism inferred
from Hanle measurements are converging towards a similar description.
They are both described as randomly oriented, largely transverse fields
in the several hecto-Gauss range. These similarities are ever making
more natural to assume that they are the same. However, and because of
the large voids of magnetic flux observed in the spatial distribution of
the internetwork fields, it is argued that they are not likely to be
generated by dynamo action in the intergranular lanes. It is concluded
that if a dynamo is acting at granular scales, the end product might
have not been observed yet at current spatial resolutions and
sensitivities with the Zeeman effect. Thus an effort to increase these
resolutions and polarimetric sensitivities must be made. New ground- and
space-based telescopes are needed. The opportunity offered by the Solar
Orbiter mission to observe the Quiet Sun dynamics at the poles is seen
as one of the most important tests for confirming the existence, or
otherwise, of a granularly driven surface dynamo.
Related projects
Solar and Stellar Magnetism
Magnetic fields are at the base of star formation and stellar structure and evolution. When stars are born, magnetic fields brake the rotation during the collapse of the mollecular cloud. In the end of the life of a star, magnetic fields can play a key role in the form of the strong winds that lead to the last stages of stellar evolution. During
Tobías
Felipe García