Joan T. SchmelzJoan T. SchmelzUniversity of MemphisUniversity of MemphisMonterey, Feb 2006 Monterey, Feb 2006

Limitations of TRACE/EIT Limitations of TRACE/EIT Temperature Analysis Temperature Analysis

for Coronal Loopsfor Coronal LoopsUofM StudentUofM StudentWorkforce: Workforce: K. Nasraoui K. Nasraoui J. RoamesJ. RoamesL. LippnerL. LippnerJ. GarstJ. GarstA. GibsonA. Gibson

• EIT (Neupert et al. 1998) EIT (Neupert et al. 1998)

• TRACE (Lenz et al. 1999)TRACE (Lenz et al. 1999)

• Isothermal approximation Isothermal approximation

• Ratio of 171 and 195 A imagesRatio of 171 and 195 A images

1st-Generation Loop 1st-Generation Loop Temperature AnalysisTemperature Analysis

Observed Ratio

Plasma Temperature

TRACE: TRACE: 171 171 Loop Loop Pixels Pixels

TRACE: TRACE: 195 195 Loop Loop Pixels Pixels

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

• Loops had T~1.2 MK Loops had T~1.2 MK

• Surprise: not RTVSurprise: not RTV

• No significant temperature variation No significant temperature variation along loop lengthalong loop length

• Could loops be preferentially heated Could loops be preferentially heated at the footpoints?at the footpoints?

1st-Generation Loop 1st-Generation Loop Temperature ResultsTemperature Results

• Aschwanden et al. (2000 etc.) Aschwanden et al. (2000 etc.) – TRACE and EITTRACE and EIT– 195/171 loops and 284/195 loops195/171 loops and 284/195 loops– Added background subtractionAdded background subtraction– Stressed co-alignmentStressed co-alignment

• Schmelz et al. (2003, 2006)Schmelz et al. (2003, 2006)– Looked at a few loops in great detail Looked at a few loops in great detail

2nd-Generation Loop 2nd-Generation Loop Temperature AnalysisTemperature Analysis

TRACE: TRACE: Back-Back-ground ground PixelPixel

TRACE: TRACE: Back-Back-ground ground Pixels Pixels

TRACE: TRACE: Back-Back-ground ground PixelsPixels

-BG subtraction or not -BG subtraction or not

-Simple BG subtraction or complex-Simple BG subtraction or complex

-Loop pixels or BG pixels-Loop pixels or BG pixels

Instrument

Data

• Why do we see so many 1.2 MK TRACE Why do we see so many 1.2 MK TRACE Loops? (171/195; AR loops)Loops? (171/195; AR loops)– Selection effect? Selection effect?

– Instrumental effect? Instrumental effect?

– Operator error?Operator error?

Question for Mark WeberQuestion for Mark Weber

5.0 5.5 6.0 6.5 7.0

17

18

19

20

21

22

23

Log Temperature

Log

DE

M

5.0 5.5 6.0 6.5 7.0

17

18

19

20

21

22

23

Log Temperature

Log

DE

M

5.0 5.5 6.0 6.5 7.0

17

18

19

20

21

22

23

Log Temperature

Log

DE

M

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

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

Important Result:Important Result:

There is a Second Class of There is a Second Class of Solutions to Explain Flat TRACESolutions to Explain Flat TRACE171/195 Ratios for AR loops:171/195 Ratios for AR loops:1.1. All the AR plasma is at 1.2 MKAll the AR plasma is at 1.2 MK2.2. There is a broad T-distributionThere is a broad T-distribution along the line of sightalong the line of sight

-- Weber et al. (2005)-- Weber et al. (2005)

• Zhang, White & Kundu 1999Zhang, White & Kundu 1999

• Chae et al. 2002Chae et al. 2002

• Aschwanden & Nightingale 2005Aschwanden & Nightingale 2005

• Use three coronal fliters171/195/284Use three coronal fliters171/195/284

3rd-Generation Loop 3rd-Generation Loop Temperature AnalysisTemperature Analysis

Aschwanden & Nightingale (2005) example loopAschwanden & Nightingale (2005) example loop

Isothermal Approximation T=1.2 MK

• Markov-Chain Monte Carlo based DEM Markov-Chain Monte Carlo based DEM algorithm (Kashyap & Drake 1998) 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 DEM modification done randomly to

obtain new models to compare with dataobtain new models to compare with data

DEM from DEM from Vinay Kashyap (CfA)Vinay Kashyap (CfA)

• Problem: plasma could be isothermal, Problem: plasma could be isothermal, the 3 filters cannot constrain the DEM the 3 filters cannot constrain the DEM

• Solution: need more filters with higher Solution: need more filters with higher & lower temperature responses -- AIA& lower temperature responses -- AIA

• AIA provides AIA provides – high-T and low-T constraints on the DEMhigh-T and low-T constraints on the DEM

– Sufficient T coverage to determine Sufficient T coverage to determine isothermal vs. multi-thermal structureisothermal 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 filters Image the AR loops in all AIA filters (even if the loops aren’t visible in all filters)(even if the loops aren’t visible in all filters)

AIA SequenceAIA Sequence

The absence of photons is The absence of photons is NOT an absence of NOT an absence of informationinformation

-- Leon Golub-- Leon Golub