Forefronts, Spring 1994, Volume 9, Number 

Theory Center Visualization


A figure from a video by Theory Center researcher Steve Lantz, showing the interaction of plasma convection with a magnetic field. Such convection, which is governed by the laws of magnetohydrodynamics (MHD), is responsible for transporting heat in the outer layers of the Sun and other stars. In this 2D visualization of roll-like convection, the borders of the colored regions are streamlines of the flow, while the dark lines are magnetic field lines. A horizontal magnetic field is imposed at the bottom boundary and is allowed to diffuse upward into the convecting region, where it undergoes stretching and mixing due to a tilt/shear instability of the convection rolls. Above the convection zone, some magnetic field emerges from the top boundary into a vacuum region (shaded in blue in the figure), where it might be seen by an external observer. A generalization of this type of stretching and mixing to three dimensions may be important to the "solar dynamo" process, which is the cause of the well known 11-year sunspot cycle.


Another frame from the video by Theory Center staff member Steve Lantz. In this case, with different fluid parameters, the tilt/shear instability is absent, so the balanced, counterrotating rolls pull the magnetic fields up to the surface in a steady, symmetric fashion. (Green shading indicates a counterclockwise sense of rotation, while red is clockwise). An external observer would see a symmetric and dense concentration of vertical magnetic flux located near the downflowing region as shown. By contrast, above the tilted flow in the previous figure, the loop of magnetic field--- though still centered over the downdraft---has a skewed spatial distribution and is chaotically time- dependent. The latter type of correlation between vertical flow and vertical flux is closer to what is actually observed at the surface of the Sun. Lantz's video was recently accepted for publication in The Astrophysical Journal.

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Copyright 1994 by Cornell University. All Rights Reserved.

Layout and execution by Michael Herzog ( Last updated May 1994