Modeling Magnetoconvection in Active Regions Neal Hurlburt, David Alexander, Marc DeRosa Lockheed...
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Transcript of Modeling Magnetoconvection in Active Regions Neal Hurlburt, David Alexander, Marc DeRosa Lockheed...
Modeling Magnetoconvection in Active Regions
Neal Hurlburt, David Alexander, Marc DeRosa
Lockheed Martin Solar & Astrophysics Laboratory
Alastair RucklidgeUniversity 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=100 1000300
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=100171• 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=100SXT• 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
+15-30 +30
-15
Br
Ur
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=2.5Rs
• 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