3-D Pre-Eruption Magnetic Field Configuration Involved in 28 Oct 2003 Fast Halo CMEs

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3-D Pre-Eruption Magnetic Field Configuration
Involved in 28 Oct 2003 Fast Halo CMEs

• Xuepu Zhao
• Stanford University
• 36Th COSPAR Assembly Beijing, China, July
  19, 2006

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1. Purpose of the work

• This work tries to study the cause of extreme
  solar eruptions occurred in AR486
• The time variation of AR486 rope
• Conditions for an emerging flux rope to generate
  an extreme solar eruption
• The 3-D field configuration above AR486
• Summary discussion

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2. Time variation of AR486

• Within AR486, reverse S
• structures have been
• Identified in
• pre-X17-flare Hafilament
• post-X17-flare EIT
• arcade
• (Yurchyshyn et al., 2005)
• left-handed flux rope
• (Fan Gibson, 2004)

Movie
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Fig. 1 shows the time variation of the AR area
(top panel), total line-of-sight field strength
(middle panel), the mean line-of-sight field
(bottom panel) of AR0486 from Oct 22 to Nov
The symbols and lines denote the parameters
for outward and inward polarities. The green
red lines denote the total of unsigned and
signed parameters, respectively. Positive area
decreases, Negative area increases Bl Bl-
gt Emerging flux rope!
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3. Conditions for emerging rope togenerate
extreme solar eruption

• 3.1 Fan Gibson (2004)
• Before kink instability,
• Quasi-equilibrium expand, displace arcade
• potential gt non-potential
• 3.2 Upward buoyancy is balanced by downward
  plasma weight magnetic force in the arcade. It
  is
• the plasma weight .

Fig. 2 Adopted from Fan Gibson
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3.3 The buoyancy depends on density in ropes
N decreases, buoyancy increases 3.4 The
plasma weight depends on the volume of
the arcade overlying the rope. The
volume depends on what kind of closed
field region the AR486 is located
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Fig. 3 Bipolar (underlying HCS) and Uni-polar
(underlying plasma sheet with like polarity)
Closed Region (BCR UCR) (Hundhausen, 1972
Zhao Webb, 2003)
Fig. 4 A sketch of the 12 November 1966 eclipse
adopted from Saito Tandberg-Hanssen
1973 The condition for EFRs to generate extreme
solar eruptions is Low-density twisted ropes
emerging within UCRs
The top of the outmost arcade in UCR is lower
than in BCR. Plasma weight in UCR is in general
less than in BCR
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4. The 3-D field configuration above AR486
before newly emergence of flux rope
Fig 5 Magnetic arcades anchored at Bl gt 50 G
calculated using 2003.10.28_09.35
synoptic frame the PFSS model with Nmax200.
The top of outmost arcade above AR486
looks lower than others
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EIT 195 2003.10.28_13.13
Fig. 6 Left panel shows the calculated magnetic
arcades with top less than 1.10 Rs.
The calculated arcade above the red dot is
similar to the observed bright arcade.
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Fig. 7 Magnetic arcade calculated starting from
all pixels with the arcade top 1.00-1.05
(l-t) 1.05-1.10 (r-t) 1.10-1.30 (l-b) 1.30-2.50
(r-b) AR486 was located in UCR with outmost
arcade top less than 1.1 Rs
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5. Summary and Discussion

• 5.1 We have shown
• The evidence that suggests that AR486 may
  be an emerging left-handed twisted flux rope
• Low-density twisted ropes emerging
  within UCRs are the condition for emerging flux
  ropes to generate extreme solar eruptions
• The AR0486 is located in an UCR and the
  top of outmost arcade anchored within AR486
  before the emergency of the flux rope is mostly,
  if not all, less than 1.10 Rs, implying that the
  plasma weight that confines the emerging flux
  rope is small.

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5.2 If the evolution of emerging flux ropes
discussed above is valid, the plasma
density in the emerging flux rope must be low
to satisfy the condition for AR486 to generate
extreme solar eruptions. 5.3 On Oct.
29, 2003 a left-handed magnetic cloud with low
density was observed by ACE, and the cloud
has been shown to be the interplanetary
counterpart of the 28 Oct 2003
X17-flare-associated halo CME (Hu et al., 2005,
also see Fig. 8), consistent with the
inference of 5.2 5.4 It has been shown
that most of halo CMEs occur within BCRs
(Zhao webb, 2003) and most of magnetic clouds
contain low plasma temperature, implying
that the BIG plasma weight of the
overlying arcade and the SMALL buoyancy of ropes,
thus the emergence of flux ropes may be
ceased before the kink instability takes
place. Shearing and converging flows may be
necessary to drive break-out CMEs.
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Thank you !
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