Modeling Magnetoconvection in Active Regions Neal Hurlburt, David Alexander, Marc DeRosa Lockheed Martin Solar & Astrophysics Laboratory Alastair Rucklidge University of Leeds (Or what Solar B can do for me)

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=100 Q=1000

Q= r Heating Energy Inputs Peaks near penumbra/umbra boundary Weak heating by “grains” Time dependent Pointing Flux at surface for various field strengths

Coronal Heating: Q= Moss –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, ApJ 2002

Coronal Heating: Q=100 SXT Moss –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, ApJ 2002

3D Model Penumbra 3D Cylindrical Segment (CCS code) –10Mm x 40Mm 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.

3D 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.

3D Compressible Spherical Segment Code (CSS) Fully-compressible magnetoconvection Initial radial field with no net flux Parameters –Ray=1e5 –Pr=1, Pm=.2 –5 Hp DeRosa & Hurlburt, 2002

Q F BrBr UrUr Moderate field Q=100 Dots form in strong field regions Cells move Pattern not random Evolves from previous state Dynamo action Solar B/FPP clarify dynamics of SG magnetoconvection DeRosa & Hurlburt, 2002

Into the Corona: Structure Potential field extrapolation –source surface at r=2.5R s Most lines closed (black) Which lines are heated?

Simulated AR Observation (Alexander et.al.) Loops –Potential Extrapolation –MDI Magnetogram Emission –Hydrostatic model (Aschwanden & Schrijver 2002) –TRACE 284 Response Uniform Heating On Disk On Limb

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