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Modeling Long-Lived “Super-Hydrostatic” Active Region Loops
Harry Warren Amy Winebarger
John Mariska
Naval Research LaboratoryWashington, DC
Solar-B Science MeetingJapan
February 3-5, 2003Heating Function? EH(s,t)
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Motivation: Understanding the properties of active region loops observed with TRACE
Aschwanden et al., 2001, ApJ, v550, p1036
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Static Models Don’t Work!
RTVS (uniform heating) scaling law predicts very low densities for long loops.
TRACE observations show nobs/nuni ~ 100!
RTVS (foot point heating) scaling law gives densities that are higher, but only by a factor of about ~3. Highly localized footpoint heating → instability.
Winebarger et al., ApJ, in press
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Impulsive Heating Steady Heating
n ≈ T1/2 n ≈ T2
10 MK → 1 MK
n → n/3
10 MK → 1 MK
n → n/100
Dynamic solutions can be much denser than static solutions
Rosner et al., 1978, ApJ, 220, 643Cargill et al., 1995, ApJ, 439, 1034
Warren et al., 2002, ApJL, v570, p41
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Cooling loops can be overdense near 1 MK
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Loops cool faster than they drain
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Simulated TRACE light curves
Delay between the appearance of the
loop in 195 and 171
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4-Jul-1998 (Aschwanden Loop #23)
Winebarger et al., ApJ, submitted
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18-Aug-1998 (Aschwanden Loop #2)
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Simulated loop cools too fast!
EF = 2 ergs cm-3 s-1, δ = 680 s
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Not one loop, many filaments? – Consistent with the light curve
10 filaments, EF ≈ 0.2-2 ergs cm-3 s-1, δ = 680 s
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Filaments lead to flat filter ratios
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SXT→TRACE Loops
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SXT→TRACE Loops
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Light curves of loop cooling from SXT to TRACE
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Single cooling loop produces too much intensity in TRACE
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SXT/TRACE intensity ratios are consistent with filamentation
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Conclusions/Implications for Solar-B
Dynamics and filamentation are important in determining what is observed
EIS+XRT+SOT will provide an unprecedented opportunity to study the dynamical evolution of active region loops
More modeling is needed to identify signatures of coronal heating