Modeling Emerging Magnetic Flux

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Modeling Emerging Magnetic Flux

• W.P. Abbett, G.H. Fisher
• Y. Fan

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Sub-surface Modeling

• ANMHD --- 3D MHD in the anelastic approximation
• Pseudo-spectral technique
• Code is mature --- optimized for use on both
  shared and distributed memory machines (eg. IBM
  SP, SGI Origin 3800), as well as single-processor
  workstations
• Numerical algorithm allows for extensive
• exploration of parameter space

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ANMHD Examples LHS --- magneto-convection and
the local solar dynamo RHS --- emerging
magnetic flux.
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Of interest Highly twisted, knotted
configurations (Linton, Fan, Fisher)
Kink unstable magnetic flux tube rising through a
stratified model CZ (LHS using ANMHD -- Fan et
al.) and evolving in a non-stratified domain
using a periodic spectral code (RHS -- Linton).
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Delta Spot Active Regions modeled as buoyant,
initially kink-unstable flux tubes that emerge
through CZ (Linton et al.)
Q Is emerging flux (especially in highly
sheared configurations) an important component of
the CME initiation process?
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ANMHD --- Summary

• Provides numerous, simulated active region
  datasets that can be used to provide
  self-consistent, depth dependent sub-photospheric
  velocity and magnetic fields for input into
  global coronal models
• Future development plans SANMHD (3D spherical
  ANMHD --- Bercik)

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Modeling the Corona

• PARAMESH A domain decomposition, adaptive
  mesh refinement (AMR) framework developed by
  MacNeice et al. and distributed by GSFC
• Zeus3D A staggered mesh finite-difference
  (non-relativistic) MHD code originally developed
  by Stone, Norman, and Clarke and publicly
  distributed by NCSA
• ZeusAMR A fully compressible 3D MHD code with
  AMR which resulted from a merge of PARAMESH with
  a modified version of Zeus3D

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Local Zeus3D (no AMR) flux emergence calculation
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Example of driving a ZeusAMR coronal simulation
with an ANMHD generated lower boundary. True
code coupling can be achieved using the
PARAMESH framework.
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ZeusAMR Progress Tasks Completed

• Merged Zeus3D with PARAMESH v2.x (decomposition
  technique optimized for SGI shared memory
  architectures)
• ZeusAMR transport step no longer directionally
  split (Fan)
• ZeusAMR written to enhance portability the NCSA
  editor and input decks are eliminated in favor of
  more modern, portable preprocessors and I/0.
• Incorporated boundary conditions and refinement
  criteria appropriate for simulating flux
  emergence into the low corona
• Added option to include the Boris Correction
• Incorporated an approximate treatment of
  transition region heating and cooling terms

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ZeusAMR Tasks Nearly Complete

• Implement and test the polar and lower radial
  boundary conditions when running 3D MHD
  simulations in spherical coordinates
• Incorporate explicit resistivity into the code
• Develop a user-friendly means of incorporating an
  initial global coronal atmosphere into a
  pre-defined, ZeusAMR block structure

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ZeusAMR Future development

• Upgrade PARAMESH routines to v3.0 (more efficient
  mpi treatment for distributed memory
  architectures)
• Add optically thin radiative cooling and
  conduction along fieldlines to the equation of
  internal energy
• Incorporate the improved MoC algorithm, and the
  two temperature treatment of Clarke

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Summary ANMHD can provide a variety of simple
(to more complicated) datasets to incorporate
into the boundaries of global (or local)
simulations of the corona. Different
configurations can Be readily generated the
Images on the left were Calculated on a
1.2GHz Athlon PC in 8 hours