Fine Structure inside Flare Ribbons and its Temporal Evolution

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Fine Structure inside Flare Ribbons and its
Temporal Evolution

• ASAI Ayumi 1,
• Masuda S. 2, Yokoyama T. 3, Shimojo M. 3,
  Kurokawa H. 1,
• Shibata, K. 1, Ishii T. T. 1, Isobe H. 1,
  Takasaki H. 1, Kitai R. 1, Yaji K. 4
• 1 Kwasan Observatory, 2 STE lab., 3 Nobeyama
  Radio Obsevatory, 4 Kawabe Cosmic Park
• January 22, 2002, Yohkoh 10th Anniv. Meeting

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Foot Point of Flare Loop
Non-thermal particles bombard the chromospheric
plasma at both the foot points simultaneously.
The temporal evolution of both the foot points
is very similar. (Sakao 1994)
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From the site of highly-correlated pair of foot
points and the time of precipitation, the site
and the time of particle acceleration can be
determined.
simultaneously brighten
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Foot Point of Flare Loop
Precipitations of particles cause HXR sources and
Ha kernels. HXR sources and Ha kernels show
high correlation in their locations and their
temporal evolutions. (Kitahara Kurokawa 1990)
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Foot Point of Flare Loop
Ha images enable us to investigate precipitation
of non-thermal particles into the chromosphere
with higher spatial resolution than HXR and/or
microwave. (Kurokawa 1988)
Ha
HXR
Soft X-ray
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Todays Topic
We determine precisely the site of
precipitations using the Ha data of the 2001
April 10 flare. We compare the spatial
distribution of the HXT sources with the Ha
kernels and discuss the energy release at the HXT
sources.
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Observation
Flare 0510 UT April 10, 2001 GOES X2.3
class NOAA 9415 Data Ha??Kwasan Observatory,
Sartorius Telescope EUV??TRACE (171Å
image) 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.
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Method of Data Analysis
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Method of Data Analysis
? Using cross-correlation functions of the light
curves, we identified the conjugate foot points
in each mesh.
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TRACE Flare Loop
TRACE 171Å images show post-flare loops of 1MK
plasma. The TRACE flare loops really connect
the pairs.
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Time of Brightening
The pairs are classified according to the times
of brightening.
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Temporal Evolution of Ha Kernels
Movement of the site of energy release.
t
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Summary (1)

• We have invented a unique method for analyzing Ha
  data.
• We have investigated the site of the
  precipitation of particles with higher spatial
  resolution.
• We have followed the history of the energy
  release.

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HXT Sources
HXT sources
contour lines magnetic field Positive / Negative
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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
3 times larger magnetic field strength causes 27
times larger energy release rate at the HXT
sources than those of the other Ha kernels. It
is larger than the HXT dynamic range.
vi inflow velocity A area of reconnection
point
IHXT ? dE/dt
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Summary (2)

• We have found the differences of the magnetic
  field strengths between the HXT sources and the
  other Ha kernels. Those at the HXT sources are
  about 3 times larger than at the other Ha
  kernels.
• Using Ha data, we have been able to investigate
  the weaker brightenings where less energy release
  occur and cannot be seen in HXT.

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Magnetic Field Strength and Energy Release Rate
Estimation of energy release rate at each source
Energy release rate of the HXT sources is 16-27
times larger than the energy release rate of the
other Ha kernels.
vi inflow velocity A area of reconnection
point
a 0.5 (Sweet-Parker) 1 (Petschek)
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Light Curves of the Flare
Light curves of the flare The Ha light curve of
the flares also shows gradual rise like the SXR
(GOES) light curve.
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Light Curve of Ha Kernels
Light curves of each Ha kernels show impulsive
spikes like those of nonthermal radiation. Each
Ha kernel are generated by precipitation of
nonthermal particles.
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Time of Brightening
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Magnetic Field Strength and Nonthermal Radiation
Measure the magnetic field strength along the
outer sides of flare ribbons.
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Magnetic Field Strength

E2
HXT source
E3
E4
Ha kernels without HXT sources 400500
G HXT sources 12001400 G ( 3 times larger)
E1
W1
W4
W3
HXT source
W2
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