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)

Motivation: Understanding the properties of active region loops observed with TRACE

Aschwanden et al., 2001, ApJ, v550, p1036

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

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

Cooling loops can be overdense near 1 MK

Loops cool faster than they drain

Simulated TRACE light curves

Delay between the appearance of the

loop in 195 and 171

4-Jul-1998 (Aschwanden Loop #23)

Winebarger et al., ApJ, submitted

18-Aug-1998 (Aschwanden Loop #2)

Simulated loop cools too fast!

EF = 2 ergs cm-3 s-1, δ = 680 s

Not one loop, many filaments? – Consistent with the light curve

10 filaments, EF ≈ 0.2-2 ergs cm-3 s-1, δ = 680 s

Filaments lead to flat filter ratios

SXT→TRACE Loops

SXT→TRACE Loops

Light curves of loop cooling from SXT to TRACE

Single cooling loop produces too much intensity in TRACE

SXT/TRACE intensity ratios are consistent with filamentation

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