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Solar Applications of the Space Weather Modeling Framework

Solar Applications of the Space Weather Modeling Framework. R. M. Evans 1,2 , J. A. Klimchuk 1 1 NASA GSFC, 2 GMU. February 2014 SDO AIA 171 Å. Bart, Igor, Chip, Rona, Gabor, Meng, Ofer, Noé, Zhenguang, Darren, Rich, Lars, and Tamas Thank you!. February 2014 SDO AIA 171 Å.

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Solar Applications of the Space Weather Modeling Framework

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  1. Solar Applications of the Space Weather Modeling Framework R. M. Evans1,2, J. A. Klimchuk1 1NASA GSFC, 2GMU February 2014 SDO AIA 171 Å

  2. Bart, Igor, Chip, Rona, Gabor, Meng, Ofer, Noé, Zhenguang, Darren, Rich, Lars, and Tamas Thank you! February 2014 SDO AIA 171 Å

  3. Introduction • The formation and disruption of current sheets • Applies to many domains and problems in heliophysics • Coronal loops are bright structures in EUV and X ray images • A variety of observations indicate that both loops and the diffuse emission between loops are heated by impulsive bursts of energy, called nanoflares • What are the critical onset conditions for current sheet disruption, and are they different in the chromosphere and corona? • How does the coupling between the chromosphere and corona affect the disruption? • At what height in the atmosphere is the disruption likely to occur? July 2012 SDO/AIA Rebekah M. Evans October 14, 2014 SWMF User Meeting

  4. Approach: leverage experience and existing problem type GLOBAL Solar Corona Model (ModUserScChromo) REGIONAL Flux Emergence Model (ModUserEe) Fang et al. 2012 REGIONAL Coronal Loop Model with Chromosphere (ModUserTbd) Rebekah M. Evans October 14, 2014 SWMF User Meeting

  5. Simulation Set Up Loop Top Gravitational acceleration g Base of Corona Base of Chromosphere Schematic of a semicircular loop, straightened out with a modified profile for gravity. Rebekah M. Evans October 14, 2014 SWMF User Meeting

  6. New Initial Conditions Specify: Bz Tcorona Lcorona Tchromo Lchromo Rebekah M. Evans October 14, 2014 SWMF User Meeting

  7. New Initial Conditions Calculate Q* and Ncorona using static equilibrium loop scaling laws; ρcorona from ideal gas law Specify: Bz Tcorona Lcorona Hydrostatic extrapolation using Pcorona and Tchromo (H~500 km) to find base pressure Pchromo Tchromo Lchromo *Q is the background volumetric heating. We use density-dependent heating for T<Tchromo Steady State Atmosphere Rebekah M. Evans October 14, 2014 SWMF User Meeting

  8. Existing capabilities ModEquationMhd (single fluid) • Optically thin radiative energy loss User-defined loss function • Field-aligned collisional heat flux • User-defined source terms to energy, momentum equations • Gravity and Volumetric heating function • AMR • Static atmosphere and Current sheet formation Radiative loss function Radiative Loss Function Klimchuk, Raymond Temperature Simulation time increases significantly Rebekah M. Evans October 14, 2014 SWMF User Meeting

  9. Challenge: Boundary conditions I k=2 Desired features for top/bottom plasma BCs: force balance across the boundary (no mass flow) • BATSRUS options for BCs base of chromosphere: • ‘reflect’, ‘float’, ‘fixed’, ‘linetied’ • Implemented user BC • Hydrostatic extrapolation of pressure into ghost cells using Temp. in first internal cell. Density calculated from p, Temp • As the simulation approaches SS, pressure increases somewhat at the boundary and total mass of system increases k=1 k=0 k=-1 Sides are periodic • Future – solve for the actual force balance (may be too complicated) Rebekah M. Evans October 14, 2014 SWMF User Meeting

  10. Challenge: Boundary conditions II • Desired features for top/bottom BCs: create a current sheet by adding energy into the system via a shear flow at the boundary • BATSRUS options for shearing BCs: • ‘shear’: instructions to only use for specific problem type (shock tube) • Eruptive event, breakout - not clear how to easily work into generic ModUser • Implemented BC: • No magnetic flux transport through boundary • - Shearing speed U0=0.01vA,corona • Current sheet half width w=0.001Ly • Ramp up time • Apply in both ghost cells w/Ly=0.01 w/Ly=0.001 Uy [km/s] X [km] Rebekah M. Evans October 14, 2014 SWMF User Meeting

  11. Simulation at the end of the ramp up (t=10 minutes) Jz Uy By w ~200 km At the lower boundary: Velocity and magnetic shear, and the resulting current sheet At the lower boundary: Shear profile and resulting magnetic field Rebekah M. Evans October 14, 2014 SWMF User Meeting 11

  12. Required feature - AMR Using AMR to refine TR • Currently using: • Static atmosphere (4 AMR levels) • dz= 24 km in TR • ~4 million cells • Current sheet (5 AMR levels) • > 10 million cells corona 375 km Cell Size (km) 24 km TR Z (km) corona Cell Size (km) TR Cell Number Rebekah M. Evans October 14, 2014 SWMF User Meeting

  13. Required feature - AMR Using AMR to refine TR • Currently using: • Static atmosphere (4 AMR levels) • dz= 24 km in TR • ~4 million cells • Current sheet (5 AMR levels) • > 10 million cells • Desire – flexible AMR criteria to give length scales for any quantity corona Cell Size (km) TR Z (km) corona Cell Size (km) • Desire – AMR criteria selection in PARAM.in normalized to the maximum value in the simulation TR Cell Number Rebekah M. Evans October 14, 2014 SWMF User Meeting

  14. Challenge: Grid Optimization • Direction-specific AMR • Current capability: one direction, must be specified during configure – we are still thinking about how to take advantage of this • Desire: variable during runtime • Aspect ratio of cells • Current capability: can be stretched, but fixed from grid initialization • Desire: variable in time, and in the domain TR Corona Chromo. Early times As current sheet forms As current sheet disrupts Rebekah M. Evans October 14, 2014 SWMF User Meeting

  15. Needs for the future • Short term: • 3d file saving issue (Tecplot) may be resolved • Field lines, domain • Energy balance issue (Jim will discuss more) • Need S>10,000, CS aspect ratio >100 • Assistance w/ higher order schemes (spatially fifth-order MP5 limiter) • Subcycling and Part-Steady scheme may be useful • Long term: • Neutrals (multi-fluid) – Jim will discuss more • Resistivity: T-dependent, B-dependent, Pederson (cross-field) • General feedback • Tecplot output is used • Easier way to make user-defined plot variables (ex: source terms in En. Eq) • Making the code run faster is always good Rebekah M. Evans October 14, 2014 SWMF User Meeting

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