ASAI Ayumi

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Evolution of Flare Ribbons and Energy Release

• ASAI Ayumi
• Kwasan Observatory, Kyoto University
• July 12, 2002 _at_Nobeyama

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Model of Magnetic Reconnection
Released energy by reconnection or induced energy
into the region ? Estimate by using physical
values at the footpoints
re-connection of magnetic field line
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Energy Release Rate
dE/dt depends on magnetic field B and inflow
velocity vi Assuming vi ? vfoot Bcorona ?
Bphotosphe Examine the relation of these values
with energy release rate
Energy Release Rate
Reconnection model indicates
A area of the reconnection region
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Energy Release Rate
Energy Release Rate
Reconnection model indicates
Time profile of HXR intensity is well fitted with
that of dE/dt
A area of the reconnection region
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Observation
Flare 0510 UT April 10, 2001 GOES X2.3
class NOAA 9415 Data Ha??Kwasan Observatory,
Sartorius Telescope magnetogram??SOHO /
MDI hard-X ray??Yohkoh / HXT microwave??Nobeyama
Radioheliograph
NOAA 9415
Ha image taken with FMT at Hida Obs.
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Ha Movie of the Flare
Great Two-Ribbon Flare Thanks to short exposure
time, fine structure inside the flare ribbons is
clearly seen.
West
East
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HXR Sources
HXR sources
contour lines magnetic field Positive / Negative
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Magnetic Field Strength and HXR Radiation
Measure the magnetic field strength along the
outer sides of flare ribbons.
North
South
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Magnetic Field Strength
E2

negative
HXT source
E3
E4
North
E1
W1
W4
W3
South
HXT source
-
W2
positive
North
South
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Magnetic Field Strength
Magnetic Field Strength (G)
E1 300 E2 1350 E3 550 E4 500
W1 300 W2 1200 W3 500 W4 450
Ha kernels without HXT sources 300550
G HXT sources 12001350 G ( 3 times larger)
W1
E1
W3
E3
W4
E4
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Magnetic Field Strength and Energy Release Rate
Estimation of energy release rate at each source
magnetic field strength is 3 times larger
? Energy release rate of the HXR sources is 16-27
times larger than the energy release rate of the
other Ha kernels. It is larger than the HXT
dynamic range.
vi inflow velocity A area of reconnection
point
a 0.5 (Sweet-Parker) 1
(Petschek)
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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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Separation of Flare Ribbons
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Separation speed and HXR Sources
HXR sources appear when separation speed of
flare ribbons slow down

distance from neutral line
East
West
time
time
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Separation Speed and Energy Release Rate
HXR sources appear when separation speed of flare
ribbons slow down ?inverse dependence!?
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
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Reconnection Rate and Poynting Flux

• Reconnection rate

Bcoronavi Bphotospherevfoot

• Poynting Flux

Bcorona2vi ? Bphotosphere2vfoot
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Reconnection Rate and Poynting Flux
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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 Ha
  kernels.
• This suggests that the energy release rate at
  the HXR sources is 16-27 times larger than those
  of the other Ha kernels.

2a
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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.