asai ayumi kwasan observatory, kyoto university july 12, 2002 @nobeyama evolution of flare ribbons...
TRANSCRIPT
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ASAI Ayumi Kwasan Observatory, Kyoto University
July 12, 2002 @Nobeyama
Evolution of Flare Ribbons and Energy Release
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“re”-connection of magnetic field line
Released energy by reconnection or induced energy into th
e region↑
Estimate by using physical values at t
he footpoints
Model of Magnetic Reconnection
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Energy Release RatedE/dt depends on m
agnetic field B and inflow velocity vi
Assumingvi ⇒ vfoot
Bcorona ⇒ Bphotosphe
Examine the relation of these values with energy
release rate
32
4BAv
B
dt
dEi
Reconnection model indicates
A : area of the reconnection region
Energy Release Rate
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Energy Release Rate
32
4BAv
B
dt
dEi
Reconnection model indicates
A : area of the reconnection region
Energy Release Rate
Time profile of HXR intensity is well fitted wi
th that of dE/dt
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Flare・ 05:10 UT April 10, 2001・ GOES X2.3 class・ NOAA 9415
DataH ・・ Kwasan Observatory, Sartorius Telescopemagnetogram ・・ SOHO / MDIhard-X ray ・・ Yohkoh / HXTmicrowave ・・ Nobeyama Radioheliograph
Observation
H image taken with FMT at Hida Obs.
NOAA 9415
Sartorius Telescope
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H Movie of the Flare
East West
Great Two-Ribbon Flare
Thanks to short exposure time,
fine structure inside the flare ribbons is
clearly seen.
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E4
E3E2
E1
W4
W3 W2
W1HXR sources
HXR Sources
contour lines : magnetic fieldPositive / Negative
E2
W2
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Measure the magnetic field strength along the outer sides of flare ribbons.
North
South
SOHO/MDI
Magnetic Field Strength and HXR Radiation
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Magnetic Field Strength
E3E1
E2
E4
W3
W2
W1 W4
HXT source
HXT source
+
-
North South
North
South
positive
negative
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Magnetic Field Strength
・ H kernels without HXT sources
: 300 ~ 550 G
・ HXT sources : 1200 ~ 1350 G
( ~ 3 times larger)
E1 : 300E2 : 1350E3 : 550E4 : 500
W1 : 300W2 : 1200W3 : 500W4 : 450
Magnetic Field Strength (G)
E4
E3
E1
W4
W3E2W2W1
E2W2
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32
4BAv
B
dt
dEi
↓
Energy release rate of the HXR sources is 16-27 times larger than the energy release rate of
the other H kernels. It is larger than the HXT
dynamic range.
Estimation of energy release rate at each source
vi : inflow velocityA : area of reconnection point
32
4BAv
B
dt
dEi
vi : inflow velocity B∝
2+
= 0.5 (Sweet-Parker)
1 (Petschek)
magnetic field strength is 3 times larger
Magnetic Field Strength and Energy Release Rate
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Evolution of Flare Ribbon
To examine separation of ribbons, we estimated the distance of the fronts of the ribbons from neutral line in the direction perpendicular to neutral line.
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05:10
05:40
××
WestEastt
r r
Separation of Flare Ribbons
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HXR sources appear when separation speed of flare ribbons slow down
×
WestEast
dis
tan
ce
fro
m n
eu
tral
lin
e
time time
Separation speed and HXR Sources
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32
4BAv
B
dt
dEi
Slowing down of the ribbon-separation is caused by increase of magnetic field strength.
Both B and vi must be considered simultaneously Reconnection Rate and/or Poynting Flux
HXR sources appear when separation speed of flare ribbons slow down→inverse dependence!?
Separation Speed and Energy Release Rate
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32
4BAv
B
dt
dEi
•Reconnection rate
Bcoronavi = Bphotospherevfoot
•Poynting Flux
Bcorona2vi ∝ Bphotosphere
2vfoot
Reconnection Rate and Poynting Flux
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Reconnection Rate and Poynting Flux
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Bphotosphere
Separating Speed
Distance from NL
B2×v
B×v
Microwave
HXR
Reconnection Rate and Poynting Flux
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Summary (1)
The magnetic field strengths at the HXR sources are about 3 times larger than at the other H kernels.
This suggests that the energy release rate at the HXR sources is 16-27 times larger than those of the other H kernels.
32
4BAv
B
dt
dEi
3
2
4BAv
B
dt
dEi
2+
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Summary (2)
The HXR sources appear when the separating speed of the flare ribbons are slowing down.
This seems to be inversely dependence on the energy release rate.
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Summary (3)
There are good correlations between the energy release rate and the reconnection rate and poynting flux.