Magnetic Reconnection in Flares Yokoyama, T. (NAOJ) Reconnection mini-workshop Kwasan obs. Main Title 1.Introduction : Reconnection Model of a Flare 2.Direct Observation of a Reconnection Inflow 3.MHD Simulation of a Flare

Reconnection Model of a Flare & Yohkoh Observations

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)

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

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

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)

Many pieces of indirect evidence cusp loops, loop-top HXR sources, plasma ejection supporting MHD simulations FOUND !! 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 …

2. Flare Long-Duration Event (LDE; ~300  A) on the NE solar limb Simultaneous coronal mass ejection (CME) SOHO/EIT SOHO/LASCO

Soft X-ray Observation by SXT of Yohkoh cusp-shaped flare loops 100,000 km 3:033:224:37 8:0316:270:31 T > 4MK

Observation of plasmoid ejection and reconnection inflow EUV ~1.5MK SXR > 4MK 100,000 km

Observation of plasmoid ejection and reconnection inflow

Plasmoid ejection Inflow Reconnected loop X-point

Evolution of 1D plot of EIT data across the X-point

Evolution of 1D plot of SXT data along the cusp

Energy release rate (1) Derivation of reconnection rate From SXR observation Lifetime From EUV observation Energy release rate (2)

From (1) = (2) Thus, we obtain Consistent with the Petschek model.

MHD Simulation of a Flare T. Yokoyama (NAOJ) K. Shibata (Kyoto Univ.)

MHD Simulation of a Flare Yokoyama & Shibata (1998) Simulation from the peak to the end of the decay phase Growth and cooling of post-flare loops Light curve, differential emission measure In this study Heat Conduction, Evaporation & Radiation Cooling This Study

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, Plasma  = 0.2 Alfv = 100 sec cond = 600 sec rad = sec Numerical Model chromosphere corona

Time Series Temporal Evolution

Movie : Temperature

Movie : Density

Effects of the Heat Conduction & Radiation Cooling Only MHD Tempera ture Density Effects of Heat Conduction & Radiation Cooling #0

Effects of the Heat Conduction & Radiation Cooling Tempera ture Density Only MHDConduction Effects of Heat Conduction & Radiation Cooling #1

Conduction & Radiation Conduction Effects of the Heat Conduction & Radiation Cooling Tempera ture Density Only MHD Effects of Heat Conduction & Radiation Cooling #2 This is the case without the radiation but with the conduction.

Differential Emission Measure (DEM) Derived from the Simulation Results Time DEM 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 Dere & Cook (1979) ( only initial part of the decay phase ) DEM Derived from the Simulation DEM Derived from the Observations DEM: Comparison

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. Light Curve & Energy Budget

Parameter survey : Effect of plasma  When the  is smaller, the cooling time is shorter. Plasma Beta #0

When the  is smaller, the cooling time is shorter. Explanation If we assume is independent of at the start of the radiation cooling process Plasma Beta #1 radiation: energy balance in reconnection & magnetic confinement (Shibata & Yokoyama 1999)

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. Summary