1 Introduction: Onset of solar flares and coronal mass ejections Yokoyama, T. Dept. Earth & Planetary Science, University of Tokyo Isobe, H. Univ. Tokyo Shibata, K. Kyoto Univ. AOGS Singapore

2 Observational evidence for the magnetic reconnection model The “CSHKP” model Masuda et al. (1994) Shibata et al. (1995) Tsuneta et al. (1992) Yokoyama et al. (2000) see also Lin et al. (2005)

3 Reconnection in the onset of a CME Lin & Forbes (2000) Chen & Shibata (2000)

4 Observational evidence for the magnetic reconnection model The “CSHKP” model Masuda et al. (1994) Shibata et al. (1995) Tsuneta et al. (1992) Yokoyama et al. (2000)

5 What is the next ? Energy build-up and trigger mechanism of flares/CMEs Particle accelerations Reconnection physics and so on …

6 Temporal change of the magnetic patterns on the surface: Complex motions ; shear, rotation, collision, emergence The coronal field lines are twisted and sheared. Free energy is stored in a form of electric currents. Release of the stored free magnetic energy Energy build up

7 Plasma eruption triggered by emerging flux The helical field lines are ejected upward. erupting field lines Notoya, TY, HI et al. (2006)

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9 SOLAR-B/SOT (SOHO/MDI NASA) 3-componets vector field High resolution (~0.2 arcsec) Without interruption

10 Topics in the following talks Measurement of the helicity and its injection in terms of the energy build-up in the corona Reconstruction of the coronal field from the observational data of the photospheric magnetic field. Energy build-up processes: shear & emergence of magnetic flux

11 Questions How is the free magnetic energy stored ? Where and when ? What is the trigger mechanism of a flare/CME ? How can we reconstruct the magnetic field in the corona ? Is it OK only by using the photospheric field information ? Is the helicity (or helicity injection) a good parameter for the prediction of a flare/CME event ? What are the conditions of an active region to be flare/CME productive ?