Evolution of Flare Ribbons and Energy Release Magnetic Reconnection 2005 @Awajishima, Hyogo, March 8 – 10, 2005 Evolution of Flare Ribbons and Energy Release Ayumi Asai1, T. Yokoyama T.2, M. Shimojo1, S. Masuda3, and K. Shibata4 1: Nobeyama Radio Observatory, NAOJ 2: Dept. of Earth and Planetary Science, University of Tokyo 3: Solar-Terrestrial Environment Laboratory, Nagoya University 4: Kwasan and Hida Observatories, Kyoto University Sartorius telescope @Kwasan Obs. 1. INTRODUCTION Magnetic reconnection is a key process for energy release and particle acceleration during solar flares. We quantitatively estimated the amount of the released energy, based on the magnetic reconnection model and by using observable values. Energy release rate (dE/dt) is written as: Bc : coronal magnetic field strength vi : inflow velocity A : area of reconnection region Since it is difficult to estimate corona physical values (Bc, vi), by using the conservation law of magnetic flux, we estimate the energy release rate with observable values (Bp, vf). Flare 2001 April 10, 05:00UT @NOAA 9415 GOES X2.3 Data Ha…Kwasan Obs., Sartorius Telescope Magnetogram…SOHO / MDI hard-X ray (HXR)…Yohkoh / HXT Microwave… Nobeyama Radioheliograph NOAA 9415 Fig.2 Cartoon of magnetic reconnection conservation of magnetic flux Bc : coronal magnetic field strength vf : speed of ribbon separation Reconnection rate Bc・vi = Bp・vf (Conservation of magnetic flux) Fig1. Ha full disk image obtained with Flare Monitoring Telescope at Hida Obs. Poynting Flux Bc2・vi ∝ Bp2・vf (Bc∝Bp is assumed) 2. ENERGY RELEASE RATE slit I slit II slit II We put slits in the direction of the flare ribbon separation, and calculated vf・Bp and vf・Bp2 at the outer edges of flare ribbons. We followed the temporal evolutions of these values. slit I microwave microwave HXR HXR HXR burst at 05:19UT HXR burst at 05:26UT neutral line newly reconnected loop reconnection rate reconnection rate Bp vf Poynting flux Poynting flux slit Fig.4 Time profiles of microwave (NoRH), HXR (Yohkoh/HXT), reconnection rate (vf・Bp), and Poynting flux (vf・Bp2) for slit I (05:19 UT burst) and slit II (05:26 UT burst). (1) Qualitatively, both of the estimated reconnection rates (vf・Bp) and Poynting fluxes (vf・Bp2) reconstruct peaks of the light curves of the nonthermal emissions. flare ribbon Fig.3 Method of the analyses The spatial distribution of the Ha kernels is different from that of the HXR sources. The dynamic range of HXT is about10. reconnection rate (ratio) vf・Bp　[V m-1] Poynting flux (ratio) vf・Bp2 [erg cm-2 s-1] K1 2.6×102 (0.52) 1.3×109 (0.27) K2 7.7×103 (16) 7.6×1011 (150) K3 4.9×102 (1.0) 5.0×109 (1.0) Table 1 Comparison of the reconnection rates and the Poynting fluxes between the Ha kernels with HXR sources and those without ones So, the released energy at the HXR sources of (at least) 10 times larger than those at the other Ha kernels can explain the difference of appearance. HXR sources strong energy release K1 K2 K3 (2) Quantitatively, both of the reconnection rates and Poynting fluxes are enhanced enough (more than 10 times larger) at the HXR sources, compared with those at the other Ha kernels. Fig.5 Ha image overlaid with HXR contour image other Ha kernels weak energy release 3. RED ASYMMETRY 4. SUMMARY We examined spatially resolved red-asymmetry distribution. Precipitation of nonthermal particles cause downward motion of chromospheric plasma  reddening in Ha flux tube We estimated the energy release rate, by using ribbon-separation speeds and photospheric magnetic field. The temporal evolution of the estimated reconnection rate and the Poynting flux reproduced the nonthermal bursts. They are locally large enough at the HXR sources, which can explain the difference of spatial distributions of radiation sources. We examined spatially resolved red-asymmetry distribution. Ha kernel Reddening is conspicuous at the edge of flare ribbons blue red l -1.5 A +1.5 A Fig.7 Spatial distribution of red-asymmetry Fig.6 A spectrum at an Ha kernel The brighter kernel, the redder it is. bright bright Normalized red-asymmetry no correlation with intensity. Downward vel. ~ constant intensity of kernel intensity of kernel red blue Fig.8 Scatter plot of reddening and Ha kernel intensity dark red dark blue Iblue-Ired (Iblue-Ired)/(Iblue+Ired)/2 We made extensive use of Yohkoh and SOHO MDI Data Service.