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Pumping of Magnetic Fields by PTCC

This research attempts to better understand the process of solar magnetic field generation by investigating the origin of strong magnetic fields that emerge at the solar surface. This field is believed to be derived from a strong toroidal magnetic field generated in a layer just below the base of the solar convection zone, called the tachocline. The tachocline is a thin region of stability located below the unstably stratified convection zone.

A thin horizontal magnetic field is arbitrarily introduced into the upper layer of a simulated solar convection zone. To maintain constant pressure, the density of the fluid inside the magnetic field is reduced. Hence the magnetic field is buoyant relative to its surroundings. In the absence of convective motion the magnetic field would rise. However, the highly turbulent convection zone drags components of the magnetic field down into the stably stratified layer by the advection of downward flowing plumes. As these plumes penetrate the stable layer in an area called the "overshoot" region, they decelerate rapidly. This rapid deceleration causes the plumes to "splash" and produce numerous small vortices. These highly turbulent vortices stretch the magnetic field and amplify its strength through local dynamo action. The net effect is a redistribution of magnetic energy as the magnetic field is both pumped into the tachocline region and then amplified.

     
     

Pumping Magnetic Fields

QuickTime | Real | MPEG

In the left cube is the enstrophy (rotation) component of a solar convection zone. On the right, a magnetic bouncy field is depicted. The magnetic field has been arbitrarily introduced into the convection zone.Ê Observe a downward flowing plume in the lower, left corner of the enstrophy domain. As we evolve through time, the magnetic field tries to rise due to bouncy. However, the competing effects of convective motion drag components of the field into the lower half of the domain.
 

Down-plume Zoom

QuickTime | Real | MPEG

Zooming in on the down-plume, we see how it interacts with the magnetic field. Notice how the field gets stronger (brighter colors) in the lower domain as the field is amplified by local dynamo action.
     
     
Visualization  
Visualization:
John Clyne, NCAR, SCD
Nic Brummell, University of Colorado
Project
Scientists:
Steve Tobias, University of Colorado
Nic Brummell, University of Colorado
Tom Clune, University of Colorado
Juri Toomre, University of Colorado
Date Catalogued:
2002-08-12
Rights:
© 2002, UCAR, All rights reserved.