Formation of Magnetic Flux Ropes
during Confined Flaring Well
Before the Onset of a Pair of Major
Coronal Mass Ejections
Georgios Chintzoglou1,*, Spiros Patsourakos2, Angelos Vourlidas3
1 School
2
of Physics, Astronomy and Computational Sciences, George Mason University, USA
Physics Department, Astrogeophysics Section, University of Ioannina, Ioannina, Greece
3 Applied Physics Lab, The Johns Hopkins University, Laurel, MD, USA
* Supported by the NASA Earth & Space Science Fellowship (NESSF)
List of Facts - AR11429
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Strongest Anti-Hale’s AR of Cycle 24!
Complex (quadrupolar) configuration.
Extreme shear (compared to Potential B) >70 deg along Polarity Inversion
Line (PIL)
Schrijver logR ≈ 5.2 (strongest PIL gradient)
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List of Facts - AR11429
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Multiple flare episodes (M2.1 , X5.4, X1.5). Activity continued throughout
AR11429’s transit
AR11429 gave off two ultra-fast CMEs (>2,000 km/sec); one of the most
geo-effective of Cycle 24 (Dst = -143 nT; Richardson 2013)
12h Prior to CMEs: Confined M2.1 flare w/ visible MFR signatures
<- Extremely non-radial
direction for each CME
5-day Evolution of AR11429
131A + BLOS Composite
AIA λ 131Å
T ≈10 ΜΚ
HMI BLOS
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5-day Evolution (BLOS from HMI)
Soft X-Ray and EUV flux from AR11429
211 A; Base difference.
NO DIMMING after
confined event
1-day evolution (prior to CMEs)
131A + BLOS Composite
AIA λ 131Å
T ≈10 ΜΚ
HMI BLOS
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From Chintzoglou et al 2015 (in print; ApJ)
DEM
Temperature Maps
SDO/AIA
Coronal Passbands
DEM Analysis for M2.1 flare
Differential Emission
Measure (DEM) is a measure
of the amount of emitting plasma
along the LOS as a function of Te.
Inversion allows to estimate the
Temperature of the plasma
 (Temperature maps; method
by Plowman et al 2013).
VERIFIED EXISTENCE OF
HOT STRUCTURE (~10MK).
From Chintzoglou et al 2015 (in print; ApJ)
Slow Quasi-Static Rise during M2.1 flare
arcsecs
STEREO EUVI B
SDO/AIA
10-20 km/sec
SDO/AIA
STEREO EUVI B
SDO/AIA
Summary of Analysis
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12 hours before the eruption, a confined eruption occurred in the NE PIL
During M2.1 flare Structure rises slowly (10-20km/sec), until it stops,
presumably because of strong overlying flux.
DEM analysis confirms that NE MFR is a very hot structure (~10 MK)
While cooling (13:49 UT), we observe the existence of a structure along
the NE PIL able to support cool plasma.
Evidence that NE flux-rope is formed via confined flare ~12 hours prior to
its CME.
Analysis II
• Using a model for the Coronal field to additionally
support the existence of magnetic flux ropes.
• Model appropriate for analysis: Non-Linear Force-Free
Field (NLFFF) Extrapolation Model (Wiegelmann 2006)
• We apply several tools to detect flux ropes
a. field-line integration & visualization
b. |J| (current) visualization
c. Fractional Twist maps
3-D Flyby around the NLFFF before
eruption (2012-03-06 23:48 UT)
From Chintzoglou et al 2015 (submitted; ApJ)
|J| cut
Integrated |J|
AIA 131 A
Comparing Model w/ Observations
Oval structure + B-field shows detached helical structures
From Chintzoglou et al 2015 (in print; ApJ)
Flux rope parameters from NLFFF
Fractional Twist Maps
The magnetic Twist of field lines
is related to the magnetic helicity via
the Twist, Tn,and Writhe, Wr, numbers
(Berger & Field 1984):
An analytical expression for
Tn, is given in Berger & Prior 2006.
For force-free fields:
α: force-free parameter,
dl: infinitesimal length of field line.
Applying this analysis on a simulated
Sheared Arcade (from Aschwanden 2006),
the highest value obtained for Tn is 0.5
From Chintzoglou et al 2015 (submitted; ApJ)
Time evolution of <α>, <Τn>, Twisted Flux
From Chintzoglou et al 2015 (in print; ApJ)
Summary of Analysis II
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Only a small fraction in the vicinity of the PIL exhibits significant twist
(|Tn|>0.5).
Flux ropes are weakly twisted and low lying.
PHYSICAL CONSIDERATIONS:
• The Kink Instability (KI) is not supported by these findings nor by 131 Å
imaging.
• Therefore we shall consider the Torus Instability (TI) for the trigger
mechanism of the CMEs -> critical decay index ncrit.
Decay Index vs Height
Evidence for super-critical
D.I. “tunnels” (n>1.5) –
allowing the ejection of the
MFR
From Chintzoglou et al 2015 (in print; ApJ)
Conclusions
Anti Hale’s AR w/ two ultra-fast (>2,000km/s) CMEs
Two distinct locations (PILs) of activity within the AR
Confined eruption likely created a relatively high-lying FR which
subsequent flux emergence + cancellation strengthened it and led to 1st
CME.
• MFR1 may have formed in confined flaring and MFR2 over multiple
subflaring events.
• CME trigger: Torus Instability; direction: path of minimum resistance.
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Thank you
• Shear evolution suggestive of MFRs prior to
eruption (see Forbes & Priest 1995)
Evolution of Shear
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Shear builds up w/ time
Note: Increase of mean shear is consistent
with rise/expulsion of Flux-rope(s). Forbes
& Priest (1995) showed that while the
horizontal field after eruption becomes
less potential, the net field above an
AR can become more potential.
Decay Index vs Height
Evidence for DI supercritical “tunnels” (n>1.5) –
allowing the ejection of the
MFR
From Chintzoglou et al 2015 (submitted; ApJ)
Movie showing slow rise
SDO/AIA
STEREO B
From Chintzoglou et al 2015 (submitted; ApJ)