1 / 31

Main Title

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. Reconnection Model of a Flare & Yohkoh Observations.

ralph
Télécharger la présentation

Main Title

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 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

  2. Reconnection Model of a Flare & Yohkoh Observations

  3. 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)

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

  5. 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

  6. 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)

  7. Many pieces of indirect evidence • cusp loops, loop-top HXR sources, plasma ejection • supporting MHD simulations FOUND !! • But … for solar flares, here has been • NOdirect evidence of reconnection • NO observation of energy-release site itself • We should search for the reconnection flows …

  8. 2. Flare 1999-3-18 • Long-Duration Event (LDE; ~300tA) on the NE solar limb • Simultaneous coronal mass ejection (CME) SOHO/LASCO SOHO/EIT

  9. Soft X-ray Observation by SXT of Yohkoh • cusp-shaped flare loops T > 4MK 3:03 3:22 4:37 8:03 16:27 0:31 100,000 km

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

  11. Observation of plasmoid ejection and reconnection inflow

  12. Observation of plasmoid ejection and reconnection inflow Plasmoid ejection Inflow X-point Reconnected loop

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

  14. Evolution of 1D plot of SXT data along the cusp

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

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

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

  18. MHD Simulation of a Flare This Study 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

  19. Numerical Model Numerical Model Alfv = 100 sec cond = 600 sec rad = 16000 sec • 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

  20. Time Series Temporal Evolution

  21. Movie : Temperature Movie : Temperature

  22. Movie : Density Movie : Density

  23. Effects of the Heat Conduction & Radiation Cooling Effects of Heat Conduction & Radiation Cooling #0 Only MHD Temperature Density

  24. Effects of the Heat Conduction & Radiation Cooling Effects of Heat Conduction & Radiation Cooling #1 Conduction Only MHD Temperature Density

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

  26. 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

  27. DEM: Comparison Time DEM Derived from the Simulation DEM Derived from the Observations Dere & Cook (1979) ( only initial part of the decay phase )

  28. 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.

  29. Parameter survey : Effect of plasma b Plasma Beta #0 • When the b is smaller, the cooling time is shorter.

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

  31. 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.

More Related