Main Title

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Main Title
Reconnection mini-workshop 2002.7.9. Kwasan obs.
Magnetic Reconnection in Flares Yokoyama, T.
(NAOJ)

• Introduction Reconnection Model of a Flare
• Direct Observation of a Reconnection Inflow
• MHD Simulation of a Flare

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Reconnection Model of a Flare Yohkoh
Observations
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• Observation of solar flares by Yohkoh
• Cusp-shape of the flare loop (Tsuneta et al.
  1992)
• Loop-top hard X-ray source (Masuda et al. 1994)

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• Plasma ejection associated with a flare
• Shibata et al. (1995) Ohyama et al. (1997)

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Magnetic reconnection model of solar
flares Carmichael (1964) Sturrock (1966)
Hirayama (1974) Kopp Pneuman (1976)
Magnetic energy of coronal field
Magnetic reconnection Bulk kinetic thermal
energy of plasma
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Observation of Reconnection Inflow in a
Flare T. Yokoyama (NAOJ) K. Akita (Osaka Gakuin
Univ.) T. Morimoto, K. Inoue (Kyoto Univ.) J.
Newmark (NASA/GSFC)
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Many pieces of indirect evidence cusp loops,
loop-top HXR sources, plasma ejection supporting
MHD simulations
But for solar flares, here has been NO direct
evidence of reconnection NO observation of
energy-release site itself
We should search for the reconnection flows
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• 2. Flare 1999-3-18
• Long-Duration Event (LDE 300tA) on the NE
  solar limb
• Simultaneous coronal mass ejection (CME)

SOHO/LASCO
SOHO/EIT
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• Soft X-ray Observation by SXT of Yohkoh
• cusp-shaped flare loops

T gt 4MK
303
322
437
803
1627
031
100,000 km
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Observation of plasmoid ejection and
reconnection inflow
EUV 1.5MK
SXR gt 4MK
100,000 km
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Observation of plasmoid ejection and
reconnection inflow
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Observation of plasmoid ejection and
reconnection inflow
Plasmoid ejection
Inflow
X-point
Reconnected loop
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Evolution of 1D plot of EIT data across the
X-point
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Evolution of 1D plot of SXT data along the cusp
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MHD Simulation of a Flare T. Yokoyama (NAOJ) K.
Shibata (Kyoto Univ.)
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This Study
MHD Simulation of a Flare
Yokoyama Shibata (1998)
In this study
Heat Conduction, Evaporation Radiation Cooling

• Simulation from the peak to the end of the decay
  phase
• Growth and cooling of post-flare loops
• Light curve, differential emission measure

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Numerical Model
Numerical Model

• 2.5-dimensional MHD
• Non-linear non-isotropic (Spitzer type) heat
  conduction
• Cooling by the optically-thin radiation
• No gravity
• Initially in magnetohydrostatic
• equilibrium
• Localized resistivity
• For typical case,

corona
Plasma b 0.2
chromosphere
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Temporal Evolution
Time Series
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Movie Temperature
Movie Temperature
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Movie Density
Movie Density
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Effects of Heat Conduction Radiation Cooling 0
Effects of the Heat Conduction Radiation
Cooling
Only MHD
Temperature
Density
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Effects of Heat Conduction Radiation Cooling 1
Effects of the Heat Conduction Radiation
Cooling
Only MHD
Conduction
Temperature
Density
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Effects of Heat Conduction Radiation Cooling 2
Effects of the Heat Conduction Radiation
Cooling
Conduction Radiation
Conduction
Only MHD
Temperature
This is the case without the radiation but with
the conduction.
Density
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DEM
Differential Emission Measure (DEM) Derived from
the Simulation Results
Time

• Rapid increase of the DEM of hot plasma in the
  rise phase, keeping the temperature.
• Temperature of maximum DEM decreases in the
  decay phase, keeping the amount of the DEM.

Time
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DEM Comparison
DEM Derived from the Simulation
DEM Derived from the Observations
Dere Cook (1979)
( only initial part of the decay phase )
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Light Curve Energy Budget
Light Curve Energy Budget

• The energy release continues even in the decay
  phase.
• The total amount of the released (magnetic)
  energy is several times the thermal energy
  derived from the snap shot at the peak of the
  flare.

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Plasma Beta 0
Parameter survey Effect of plasma b

• When the b is smaller, the cooling time is
  shorter.

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Plasma Beta 1

• When the b is smaller, the cooling time is
  shorter.

• Explanation

radiation
energy balance in reconnection
magnetic confinement

(Shibata Yokoyama 1999)
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Summary

• Summary
• Many pieces of evidence supporting the magnetic
  reconnection model of flares were found by recent
  space-craft observations.
• There is one example of direct observation of
  reconnection inflow.
• We developed a 2.5-dimensional MHD code
  including the effects of heat conduction,
  chromospheric evaporation, and radiation cooling.
  It is applied to simulate a solar flare.