magnetic shear in two-ribbon solar flares yingna su 1,2 advisors: leon golub 1, guangli huang 2...

Magnetic Shear in Magnetic Shear in Two-ribbon Solar FlaresTwo-ribbon Solar Flares

Yingna SuYingna Su1,21,2

Advisors: Leon GolubAdvisors: Leon Golub11, Guangli Huang, Guangli Huang22

Collaborators: A. A. Van BallegooijenCollaborators: A. A. Van Ballegooijen11, E. E. Deluca, E. E. Deluca11, , J. McCaugheyJ. McCaughey11, K. K. Reeves, K. K. Reeves11, and M. Gros, and M. Gros33

1.1. Harvard-Smithsonian Center for Astrophysics, USA Harvard-Smithsonian Center for Astrophysics, USA 2. Purple Mountain Observatory, China2. Purple Mountain Observatory, China

3. DSM/DAPNIA/Service d’Astrophysique, CEA Saclay, France3. DSM/DAPNIA/Service d’Astrophysique, CEA Saclay, France

2007 SPD dissertation talk, Honolulu, 05/28/20072007 SPD dissertation talk, Honolulu, 05/28/2007

AcknowledgementsAcknowledgements

• Advisors: Leon Golub (CfA), Guangli Huang (PMO)

• Collaborators: A. A. Van Ballegooijen, E. E. Deluca, J. McCaughey, K. K. Reeves, and M. Gros

• Valuable suggestions from S. K. Antiochos, J. Lin, J. Karpen, B. Schmieder…

• Other CfA SSXG group members: M. Weber, J. Cirtain, M. Bobra, P. J. Jibben, S. Saar, K. Korreck, A. Savcheva, L. Lundquist, and J. Bookbinder

• Instruments: TRACE, Hinode/XRT, SOHO/MDI, SOHO/LASCO, SOHO/EIT, NJIT/BBSO, SPI/ACS, Hinode/SOT, RHESSI

• Financial support: TRACE contract from Lockheed Martin and NASA contract NNM07AA02C at CfA

OutlineOutline Background (Su et al. 2006, solar physics, 236, 325)

Statistical Analysis of Shear Motion (Su et al. 2007a, ApJ, 655, 606)

What Determines the Intensity of Solar Flare/CME events? (Su et al. 2007b, ApJ, 665, 1448)

Conclusions

Preliminary results from Hinode/XRT --Evolution of the sheared magnetic fields in AR10930 (Su et al. 2007c, PASJ, submitted)

Shear Motion of Footpoints EUV brightening pairs

Start: close to the magnetic inversion line (MIL),

but widely separated along the MIL (Fig. a, highly sheared)

End: straight across and far from the MIL

(Fig. f, weakly sheared)

Strong-to-weak shear motion of the footpoints

Hard X-ray observations (Yohkoh/HXT) (Masuda, Kosugi, and Hudson 2001)

Hα, EUV, and microwave observations

(Su et al. 2006 and references therein)

This observed shear change can be understood by the cartoon we made corresponding to the standard model for solar flares. (e.g., Moore et al. 2001 and references therein).

InterpretationInterpretation

Cartoon of the evolution of the magnetic field in the standard model of solar flares ( Su et al. 2006).

OutlineOutline

Background (Su et al. 2006, solar physics, 236, 325)


What Determines the Intensity of Solar Flare/CME events?

(Su et al. 2007b, ApJ, 665, 1448)

Conclusions


MotivationMotivation

Two Questions:

Is the shear motion of the footpoints common?Is the shear motion of the footpoints common?

Could the change from the impulsive to gradual phase be Could the change from the impulsive to gradual phase be related to the magnetic shear change?related to the magnetic shear change? (Lynch et al. 2004)(Lynch et al. 2004)

Distribution of Shear AnglesDistribution of Shear Angles

Data sample: 50 two-ribbon flares well observed by TRACE

Type I flares: 86% (43 out of 50)

Ribbon separation: Yes Shear motion: Yes

For 24 Type I flares Initial shear angles: 50°– 80° Final shear angles: 15°– 55° Change of shear angles: 10°– 60°

Distribution of Distribution of TEIP - TCSM

15 Type I flares

measured shear angle corresponding HXR observations

TEIP - TCSM: 0~2 min

In most events, the cessation of shear change is 0-2 minutes earlier than the end of the impulsive phase.




Conclusions


Data sets and methodsData sets and methods

Data sample: 18 Type I flares

associated with CMEs

measured shear angles

Six magnetic parameters:

Parameters representing magnetic size: Background field strength (B), the area (S), and magnetic flux ()

Parameters representing magnetic shear: Initial shear angle (), final shear angle (), and change of shear angle()

Intensity of flare/CME events:

Peak flare flux (PFF) and CME speed (VCME)

Result IResult I

log10B, log10S, log10 vs. log10(PFF), VCME : positive correlations

log10 is better than log10B, log10S ( =B×S)

Result IIResult II

vs. log10(PFF), VCME : no correlation

is better than both and ( = - )

, vs. log10(PFF), VCME : negative and positive correlations

Result IIIResult III

Three multi-parameter combinations vs. log10(PFF) and VCME : strong linear correlations

Combination 2 (log10 , , ) is the top-ranked combination

Combination 2 is only slightly better than combination 3 (log10 , )

OutlineOutline

Background (Su et al. 2006, solar physics, 236, 325)



Conclusions


ConclusionsConclusions

The strong-to-weak shear motion of the footpoints is a common feature in two-ribbon flares.

The cessation of magnetic shear change is 0-2 minutes earlier than the end of the impulsive phase in 10 out of the 15 events, which suggests that the change from impulsive phase to gradual phase is related to the magnetic shear change.

The magnetic flux and change of shear angle are two best parameters which show comparably strong correlations with the peak flare flux and CME speed. A multi-parameter combination showsbetter correlation than individual parameter.

The intensity of solar flare/CME events may depend mainly on the released magnetic free energy () rather than the total magnetic free energy () stored prior to the eruption.




Conclusions


Observational DataObservational Data Target:

NOAA AR 10930 where two X-class flares occurred:

X3.4 flare on 2006/Dec/13

X1.5 flare on 2006/Dec/14

Data from:

Hinode/XRT

Hinode/SOT

TRACE

SOHO/MDI

Topic:

Evolution of the sheared core field prior to, during, and after the flares.

Formation of the sheared core fieldFormation of the sheared core field

XRT observations of sheared field formation:

From

00:19 UT on Dec 10

To

12:43 UT on Dec 12

SOT observations of

1. Emerging flux

2. West-to-east Motion

3. CCW Rotation

in the Lower sunspot

QuickTime™ and aYUV420 codec decompressor

are needed to see this picture.

Part of the sheared cored field erupted, while part of them stayed behind.



X 3.4 flare on 2006/12/13



X1.5 flare on 2006/12/14

Pre-flare vs. post-flare sheared core field (Dec 13 flare)Pre-flare vs. post-flare sheared core field (Dec 13 flare)

Post-flare core field is less sheared than the pre-flare core field

Reformation or partial eruption of the filament

Pre-flare vs. post-flare sheared core field (Dec 14 flare)Pre-flare vs. post-flare sheared core field (Dec 14 flare)

Post-flare core field is less sheared than the pre-flare core field

Reformation or partial eruption of the filament

SummarySummary

The formation of the sheared core field is caused by the CCW rotation and west-to-east motion of an emerging sunspot.

XRT observations of partial eruption of the sheared core field may explain the existence of the filament after the flare.

Post-flare core field is much less sheared than the pre-flare core field, which is consistent with the scenario that the energy released during the flare is stored in the highly sheared core field.

Thank you Thank you for for

your attention !your attention !

Part of the sheared cored fields erupted, Part of the sheared core fields stayed behind

magnetic shear in two-ribbon solar flares yingna su 1,2 advisors: leon golub 1, guangli huang 2...

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