Concentration of magnetic fields in convective downdrafts

Snapshot of a part of the outermost layer in a global magnetohydrodynamical simulation of solar convection. The image is displayed in a cartesian plane covering 90 degrees in latitude (vertical, equatorial plane at bottom and North Pole on top), and 150 degrees in longitude (horizontal). The color scale shows the temperature perturbation (brighter = hotter fluid, darker = colder fluid), on which are superimposed a few isocontours of the radial magnetic field (component perpendicular to the image; green = positive, blue = negative). Notice how the magnetic field tends to become concentrated in the narrower, darker lanes of colder, descending fluid surrounding broader areas of hotter, brighter ascending fluid. At this relatively early stage in the simulation, no net hemispheric flux has yet built up, so that the net magnetic flux is here close to zero. The magnetic field present at this time is mostly produced by turbulent dynamo action associated with the small-scale convective flow. .

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Ghizaru, M., Charbonneau, P., et Smolarkiewicz, P.K., Magnetic cycles in a large eddy simulation of solar convection, The Astrophysical Journal Letters, 715, L133-L137; on ADS
Racine, E., Charbonneau, P., Ghizaru, M., Bouchat, A., et Smolarkiewicz, P.K., On the mode of dynamo action in a global large-eddy simulation of solar convection, The Astrophysical Journal, 735, id46; on ADS