Download Tracing the release sites of the energy stored in the twisted coronal

Hinode9 @Belfast
13-18 September 2015
Tracing the release sites of
the energy stored in the
twisted coronal structure in
X-class flares
Toshifumi Shimizu
(ISAS/JAXA, Japan)
&
Satoshi Inoue
(Max-Plank Institute for Solar System Research, Germany)
2015.9.14
Hinode 9
3
“Eruptive” solar flares
! 
General scenario
Formation of magnetic flux rope
Free energy stored as a nonpotential magnetic field in
the corona!
Non-potential field
Active region in Dec 2006
Magnetic
Develop
MHD
dynamically
reconnection
Destabilization
Eruption of magnetic flux rope
Filament eruption, CME
2015.9.14
Hinode 9
(Amari+14 Nature)
4
Where and how the energy is
stored and released?
! 
! 
3D non-potential magnetic structure formed in the corona
Hinode SOT’s Spectro-Polarimeter (SP) makes the most
accurate measurements of vector magnetic fields at the
photosphere.
= 1000
= 1000
2012/3/6 22UT
The boundary condition for
deriving 3D coronal magnetic
fields with non-linear force free
field (NLFFF) modeling
(Inoue+14)
2015.9.14
Hinode 9
X5.4
X1.3
5
2012/3/7 X5.4/X1.3 Flare
A geoeffective solar flare
coronagraph
LASCO
Magnetic field surrounding the flare core,
producing launch of a plasma ejection
870km/s
Preflare
Onset
30” (20,000km)
SDO/AIA 194A (FeXII+FeXXIV)
2015.9.14
10min
6
A strong sheared magnetic configuration
White – positive
Black - negative
Magnetic flux Bz
Solar surface: Continuum
(Hinode SOT/SP)
Yellowed areas – flare ribbons at the beginning of the X5.4 ! 
A candidate for triggering the X5.4 flare
" 
A small-scale trigger structure identified in the red square
2015.9.14
Hinode 9
7
Surface gas dynamics
! 
Conditioning the magnetic structure for flare trigger
FOV 20”x20”
(Shimizu, Lites, & Bamba 2014)
= 1000
Trigger field
Image: Bz, arrows: (Bx, By)
(in local frame)
Yellow contours: flare ribbons
2015.9.14
Doppler velocity
-5 Km/s 0
Hinode 9
N17E27: ~30 deg tilted from LOS
+5
8
Evolution of horizontal magnetic flux
Flare onset
2.0
Area size
1.5
1.0
unit: x10
2
! 
□ : mag. flux of
horizontal field (SP)
+ : area size of
horizontal field (SP)
0.5
mag. flux
0
Dotted: Line-of-sight
magnetogram (HMI)
2.5
6
4
3.0
Area size (x107 km2)
magnetic flux (x1019 Mx)
8
0.0
18:00 20:00 22:00 00:00 02:00 04:00
Start Time (06-Mar-12 17:00:00)
The photospheric magnetic field near PIL becomes more horizontal
after eruptions, related to the newly formed low-lying fields during flares
2015.9.14
Hinode 9
9
NLFFF & Twist Map (-1<Tn<0)
3D coronal field from NLFFF
modeling
Pitch (twist number) of each field line
from one footpoint to the other. 2hr before the flare: 22:00 UT on 2012 March 6
Force-free condition
2015.9.14
∇ × B = αB
Hinode 9
Tn =
1
4π
∫ αdl
-1
Tn
0
Tn definition from Inoue+12
10
Field twist after the X5.4 flare
! 
Tn =
1
4π
∫ αdl
The magnetic twist was changed with the flare:
Decreased, increased, and redistributed.
Two hours before the flare onset 22 UT on 6 March
Two hours after the flare onset
2 UT on 7 March Tn
0
Twist changes in the two maps
Tn =
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Hinode 9
ΔTn
! 
! 
! 
! 
-1
2015.9.14
ΔTn
1
Hinode 9
-1
11
1
4π
∫ αdl
Positive ΔTn:
Twist is increased.
Negative ΔTn:
Twist is decreased.
Twist is reduced with the
flare at many locations
including the location of
the flare ribbons at the
early phase.
Twist is slightly increased
mainly at outer area.
12
Chromospheric flare ribbons ! 
! 
Trace which footpoint
locations of the magnetic
field lines are involved in the
energy release each time.
One-to-one correspondence
of bright kernels in flare
ribbons confirms that the
coronal field derived with
NLFFF is reasonable.
SDO/AIA 1600A 2015.9.14
Hinode 9
13
Twist change at the locations swept by flare ribbons
Not reliable, affected
by the boundary
condition in NLFFF
Total of changes in magnetic twist
at the flare ribbon locations
1-8
0.5-4
! 
Total intensity of the flare ribbons
(AIA 1600A) (arbitrary unit)
The largest decrease was observed in the magnetic field
lines involved at early phase of the energy releases. 2015.9.14
Hinode 9
14
Summary
! 
Some key observational elements for producing flares,
discussed with Hinode magnetic-field measurements.
–  A high-speed gas dynamics at the solar surface for leading to the
onset of flares (Shimizu, Lites & Bamba 2014).
–  The magnetic twist formed in the corona
! 
! 
Magnetic twist is redistributed (decreased and increased)
in coronal fields, in response to the occurrence of the
X5.4 flare.
The largest decrease in magnetic twist was observed in
the magnetic field lines involved at early phase of the
energy releases
2015.9.14
Hinode 9
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