Modeling Emerging Magnetic Flux W.P. Abbett, G.H. Fisher & Y. Fan

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 exploration of parameter space

ANMHD Examples: LHS --- magneto-convection and the local solar dynamo; RHS --- emerging magnetic flux.

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).

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?

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)

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

Local Zeus3D (no AMR) flux emergence calculation

Example of driving a ZeusAMR coronal simulation with an ANMHD generated lower boundary. True “code coupling” can be achieved using the PARAMESH framework.

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

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

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

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