Modeling Magnetoconvection in Active Regions Or what Solar
- Slides: 15
Modeling Magnetoconvection in Active Regions (Or what Solar B can do for me) Neal Hurlburt, David Alexander, Marc De. Rosa Lockheed Martin Solar & Astrophysics Laboratory Alastair Rucklidge University of Leeds
Questions • How does turbulent convection disperse magnetic field? • How does large-scale field influence convection? • How does convection structure & heat corona? • What do coronal structures tell us about solar magnetoconvection? • How can Solar B help answer these questions?
Approach • Explicit model of compressible magnetoconvection • Potential extrapolation • Hydrostatic loop models heated by fraction of local Poynting flux • Simulated observations
Large Scale Axisymmetric Model: Q=1000
Energy Inputs Q=100 300 1000 Heating • Peaks near penumbra/umbra boundary • Weak heating by “grains” • Time dependent r Pointing Flux at surface for various field strengths
Coronal Heating: Q=100 • Moss 171 – footpoints are bright in TRACE, dark in SXT – tops are bright in SXT, dark in TRACE • Repeated brightenings in all wavelength bands – MMFs – Collar flow • Apparent motion due to change in foot point sources • Solar-B can directly test these links Hurlburt, Alexander & Rucklidge, Ap. J 2002
Coronal Heating: Q=100 • Moss SXT – footpoints are bright in TRACE, dark in SXT – tops are bright in SXT, dark in TRACE • Repeated brightenings in all wavelength bands – MMFs – Collar flow • Apparent motion due to change in foot point sources • Solar-B can directly test these links Hurlburt, Alexander & Rucklidge, Ap. J 2002
3 D Model Penumbra • 3 D Cylindrical Segment (CCS code) – 10 Mm x 40 Mm • As aspect ratio of layer depth to radius increases, convection cells form at outer edge and migrate inwards • Flow is outwards along bright, narrow filaments • Solar-B will observe flows & field structure Low Entropy Hurlburt & Rucklidge 2002 Adv Space Res.
3 D Cylindrial Potential Extrapolation • Unipolar model embedded in larger domain with uniform flux • Fieldlines foot points chosen by Poynting flux distribution Hurlburt & Rucklidge 2002 Adv Space Res.
Uniform Heating Model • High loops from penumbra/umbra boundary • Bright low-lying loops from edges of penumbral filaments Hurlburt & Rucklidge 2002 Adv Space Res.
3 D Compressible Spherical Segment Code (CSS) • Fully-compressible magnetoconvection • Initial radial field with no net flux • Parameters – Ray=1 e 5 – Pr=1, Pm=. 2 – 5 Hp De. Rosa & Hurlburt, 2002
Moderate field Q=100 -30 Br F +30 +15 • Dots form in strong Q Ur -15 field regions • Cells move • Pattern not random • Evolves from previous state • Dynamo action • Solar B/FPP clarify dynamics of SG magnetoconvection De. Rosa & Hurlburt, 2002
Into the Corona: Structure • Potential field extrapolation – source surface at r=2. 5 Rs • Most lines closed (black) • Which lines are heated?
Simulated AR Observation (Alexander et. al. ) • Loops On Limb – Potential Extrapolation – MDI Magnetogram • Emission – Hydrostatic model (Aschwanden & Schrijver 2002) – TRACE 284 Response • Uniform Heating On Disk
Conclusions • Solar B can – – Seek signs of dynamo action Observe weak, horizontal fields in SG and granules Investigate supergranule evolution Observe detailed coupling between photospheric flows and coronal heating • Complete models of Sunspots & active regions will be available to compare directly with Solar B observations
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