Joan T. Schmelz University of Memphis Monterey, Feb 2006 Limitations of TRACE/EIT Temperature Analysis for Coronal Loops UofM Student Workforce: K. Nasraoui J. Roames L. Lippner J. Garst A. Gibson

EIT (Neupert et al. 1998)EIT (Neupert et al. 1998) TRACE (Lenz et al. 1999)TRACE (Lenz et al. 1999) Isothermal approximationIsothermal approximation Ratio of 171 and 195 A imagesRatio of 171 and 195 A images 1st-Generation Loop Temperature Analysis

Observed Ratio Plasma Temperature

TRACE:171LoopPixels

TRACE:195LoopPixels

Reminiscent of results from pioneering papers: flat distribution with T = 1.2 MK

Loops had T~1.2 MKLoops had T~1.2 MK Surprise: not RTVSurprise: not RTV No significant temperature variation along loop lengthNo significant temperature variation along loop length Could loops be preferentially heated at the footpoints?Could loops be preferentially heated at the footpoints? 1st-Generation Loop Temperature Results

Aschwanden et al. (2000 etc.)Aschwanden et al. (2000 etc.) –TRACE and EIT –195/171 loops and 284/195 loops –Added background subtraction –Stressed co-alignment Schmelz et al. (2003, 2006)Schmelz et al. (2003, 2006) –Looked at a few loops in great detail 2nd-Generation Loop Temperature Analysis

TRACE: Back- ground Pixel

TRACE: Pixels

TRACE: Pixels

-BG subtraction or not -Simple BG subtraction or complex -Loop pixels or BG pixels

Instrument Data

Why do we see so many 1.2 MK TRACE Loops? (171/195; AR loops)Why do we see so many 1.2 MK TRACE Loops? (171/195; AR loops) –Selection effect? –Instrumental effect? –Operator error? Question for Mark Weber

Log Temperature Log DEM

Log Temperature Log DEM

Log Temperature Log DEM

The TRACE 171/195 response ratio collapses toward Mark’s ‘region 2’ if the plasma along the line of sight has a broad temperature distribution

Observed 171/195 TRACE ratio was the ratio of the areas under the response curves (~1) which corresponds to T = 1.2 MK Important Result:

There is a Second Class of Solutions to Explain Flat TRACE 171/195 Ratios for AR loops: 1. All the AR plasma is at 1.2 MK 2. There is a broad T-distribution along the line of sight along the line of sight -- Weber et al. (2005)

Zhang, White & Kundu 1999Zhang, White & Kundu 1999 Chae et al. 2002Chae et al Aschwanden & Nightingale 2005Aschwanden & Nightingale 2005 Use three coronal fliters171/195/284Use three coronal fliters171/195/284 3rd-Generation Loop Temperature Analysis

Aschwanden & Nightingale (2005) example loop

Isothermal Approximation T=1.2 MK

Markov-Chain Monte Carlo based DEM algorithm (Kashyap & Drake 1998)Markov-Chain Monte Carlo based DEM algorithm (Kashyap & Drake 1998) PINTofALE (Kashyap & Drake 2000)PINTofALE (Kashyap & Drake 2000) Iterative forward fit of DEM(T)Iterative forward fit of DEM(T) DEM modification done randomly to obtain new models to compare with dataDEM modification done randomly to obtain new models to compare with data DEM from Vinay Kashyap (CfA)

Problem: plasma could be isothermal, the 3 filters cannot constrain the DEMProblem: plasma could be isothermal, the 3 filters cannot constrain the DEM Solution: need more filters with higher & lower temperature responses -- AIASolution: need more filters with higher & lower temperature responses -- AIA

AIA providesAIA provides –high-T and low-T constraints on the DEM –Sufficient T coverage to determine isothermal vs. multi-thermal structure Along the line of sightAlong the line of sight Along the length of the loopAlong the length of the loop Image the AR loops in all AIA filtersImage the AR loops in all AIA filters (even if the loops aren’t visible in all filters) AIA Sequence

The absence of photons is NOT an absence of information -- Leon Golub