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Session 17 - Magnetic Fields II.
Oral session, Tuesday, July 01
Ballroom A, Chair: Paul Charbonneau

[17.04] Two-dimensional Anelastic MHD Simulations of the Buoyant Rise of Magnetic Flux Tubes in the Solar Convection Zone

Y. Fan, E. G. Zweibel (JILA, Univ. of Colorado at Boulder), S. R. Lantz (Cornell Theory Center, Cornell University)

We perform two-dimensional simulations of the buoyant rise of twisted horizontal magnetic flux tubes through an adiabatically stratified layer representing the solar convection zone. The numerical calculations employ the anelastic approximation of the basic MHD equations. We confirm the results of recent compressible simulations by Moreno-Insertis and Emonet that the transverse component of the tube magnetic field can prevent the splitting of the tube into a vortex pair, and that most of the flux in the initial tube cross-section rises in the form of a rigid body and reaches a terminal speed similar to the prediction of the thin flux tube model. Furthermore, we studied the interaction between a pair of buoyant flux tubes as they rise side by side. Our simulations show that the vortices in the wakes of the two tubes interact and are continuously shed by the tubes. As a result each tube gains around it a net circulation of the opposite sign of the shed eddy and experiences a periodic lift force which causes the tubes to show an oscillatory horizontal motion as they rise.

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