Title: Magnetic Shear in Two-ribbon Solar Flares
1Magnetic Shear in Two-ribbon Solar Flares
- Yingna Su1,2
- Advisors Leon Golub1, Guangli Huang2
- Collaborators A. A. Van Ballegooijen1, E. E.
Deluca1, - J. McCaughey1, K. K. Reeves1, and M. Gros3
- 1. Harvard-Smithsonian Center for Astrophysics,
USA - 2. Purple Mountain Observatory, China
- 3. DSM/DAPNIA/Service dAstrophysique, CEA
Saclay, France - 2007 SPD dissertation talk, Honolulu, 05/28/2007
2Acknowledgements
- 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
3Outline
- 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)
4 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) - Ha, EUV, and microwave observations
- (Su et al. 2006 and references therein)
5Interpretation
Cartoon of the evolution of the magnetic field in
the standard model of solar flares ( Su et al.
2006).
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).
6Outline
- 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)
7Motivation
- Two Questions
- Is the shear motion of the footpoints common?
- Could the change from the impulsive to gradual
phase be related to the magnetic shear change?
(Lynch et al. 2004)
8Distribution 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
9Distribution of TEIP - TCSM
- 15 Type I flares
- measured shear angle
- corresponding HXR observations
- TEIP - TCSM 02 min
- In most events, the cessation of shear change is
0-2 minutes earlier than the end of the impulsive
phase.
10Outline
- 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)
11Data 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 (F) - Parameters representing magnetic shear
Initial shear angle (q1), final shear angle (q2),
and change of shear angle(q12) - Intensity of flare/CME events
- Peak flare flux (PFF) and CME speed (VCME)
12Result I
- log10B, log10S, log10F vs. log10(PFF), VCME
positive correlations
- log10F is better than log10B, log10S
(F BS)
13Result II
- q12 is better than both q1 and q2 (q12 q1 -
q2 )
14Result III
- Three multi-parameter combinations vs.
log10(PFF) and VCME strong linear correlations - Combination 2 (log10F , q1 , q12 ) is the
top-ranked combination - Combination 2 is only slightly better than
combination 3 (log10F , q12)
15Outline
- 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)
16Conclusions
- 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 shows - better correlation than individual parameter.
- The intensity of solar flare/CME events may
depend mainly on the released magnetic free
energy (q12) rather than the total magnetic free
energy (q1) stored prior to the eruption.
17Outline
- 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)
18Observational 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.
19Formation of the sheared core field
XRT observations of sheared field formation From
0019 UT on Dec 10 To 1243 UT on Dec 12
- SOT observations of
- Emerging flux
- West-to-east Motion
- CCW Rotation
- in the Lower sunspot
20 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
21Pre-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
22Pre-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
23Summary
- 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.
24Thank you for your attention !
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27- Part of the sheared cored fields erupted, Part of
the sheared core fields stayed behind