Evolution of BarbAngle and Partial Filament Eruption

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Evolution of Barb-Angle and Partial Filament
Eruption

• J.T. Su1,2 , Y. Liu2, H.Q. Zhang1 , H.
  Kurokawa2
• V. Yurchyshyn3
• National Astronomical Observatories, Chinese
• Academy of Sciences
• (2) Kwasan and Hida Observatories, Kyoto
  University
• (3)Big Bear Solar Observatory, New Jersey
  Institute of Technology

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• Introduction
• Chirality (Helicity or Twist) exists in all
  solar magnetic features (Rust Kumar 1994 Low
  Hundhausen 1995 Martin 1998)
• These features belong to either dextral patten
  or sinistral patten. Martin (1998) pointed out
  that different chirality patterns can not
  co-exist in one magnetic feature(Martin 1998).

Dextral
Sinistral
Chirality patterns of filaments (Martin 1998)
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• (3) However, Pevtsov et al. (2003) found some
  filaments, in quiet or active regions, exhibit
  both sinistral and dextral barbs.

Pevtsov et al. (2003)
(4) Tracing the evolving process of one certain
magnetic feature may help to eliminate the
contradictions.
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• A Liu and zhang (2002) studied the evolution of
  a delta spot. Their results clearly demonstrate
  that the helicity reversal occurred in magnetic
  features of a delta-configuration, then the
  subsequent disintegration of the sunspot
  probably ascribed to this reversal behavior.
• B Wang et al. (2004) found the flare/CME
  initiation site is characterized by close contact
  with magnetic flux of the opposite helicity
  coinciding with observed flux cancellation.
• In this work, we study the angle evolution
  of a main barb born in the U-shaped filament.

Observation
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Partial filament Dextral The whole U-shaped
filament and the filament nearby to it are
sinistral by the definitions of Martin (1998).
BBSO Ha
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• Definition of barb angle

First, we outline the intensity contour of
filament and fix the minimum intensity level of
each image. Second, we plot two axis lines of
the barb and the filament to be analyzed. Last,
we plot a circle with the cross-point of the two
lines as the center and the distance between the
barb and the center as the radius. The value of
the angle a-o-b marked in the plot is available
now, which is acute or obtuse.
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The angle evolution can be divided into two
phases (1)a rise from the acute one to the
obtuse one and (2) a fall of the angle. The
separate time is on 2210 UT.
No BBSO data
Note that the changes of the angle reflected the
evolution of the barb chirality and furthermore
the helicity of the part of filament bearing the
barb.
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The first phase of barb evolution a rise of
barb-angle
BBSO Ha
The regions A and B Weakened.
The barb chirality evolved from sinistral to
dextral.
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The second phase of barb evolution a fall of
barb-angle
The angle 900 ?
Ha center
Ha center
One can see from the fitted line in evolving
Figure, that when the barb angle decreased nearly
to 900 (there was nearly no dextral component),
the U-shaped filament began to erupt.
FMT Ha
Ha center
Ha-Blue (-0.8Å)
The regions A and B Weakened occurred again.
FMT Ha images taken at Hida Observatory (Kurokawa
et al. 1995)
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Partial filament eruption
Magnetic Flux
Partial filament eruption
Before partial filament eruption, the magnetic
cancellation occurred on the Photosphere.
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FMT Ha
FMT Ha-Blue
EIT 195
However, no obvious brightenings appeared, it
indicates that no magnetic cancellation occurred
on the Chromosphere or Corona.
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Chirality Changing in partial filament
Magnetic field reconnecting in filament or
coronal arcade
Partial filament eruption
Interconnections weakened in filament
The process of partial eruption

• Conclusions
• (1)Helicity of opposite sign was formed in the
  filament, it would be likely to weaken the
  interconnections of the whole magnetic system.
• (2) Different chirality patterns can not co-exist
  in one magnetic feature for longer time.

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• Thanks a lot !