1. Evolution of Flare Ribbons and Energy Release Rate Ayumi ASAI 1, Takaaki YOKOYAMA 2, Masumi SHIMOJO 3, Satoshi MASUDA 4, and Kazunari SHIBATA 1 1:Kwasan and Hida Observatories, Kyoto University 2:Dept. of Earth and Planetary Science, University of Tokyo 3:Nobeyama Radio Observatory, NAOJ 4:Solar-Telestorial Environment Laboratory, Nagoya University 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. We estimated the energy release rate, 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. Fig.2 H  image overlaid with HXR contour image HXR sources strong energy release 2. ENERGY RELEASE RATE Fig1. H  full disk image obtained with Flare Monitoring Telescope at Hida Observatory NOAA 9415 Energy release rate ( dE/dt ) is written as: B c : coronal magnetic field strength v i : inflow velocity A : area of reconnection region 3. RESULTS The dynamic range of HXT is about10. Therefore, if the released energy at the HXR sources are (at least) 10 times larger than those at the other H  kernels, the difference of appearance can be explained. Fig.3 Cartoon of magnetic reconnection We put slits in the direction of the flare ribbon separation, and calculated v f ・ B p and v f ・ B p 2 at the outer edges of flare ribbons. We followed the temporal evolutions of these values. Fig.5 Time profiles of microwave (NoRH 17GHz), HXR (Yohkoh/HXT), reconnection rate ( v f ・ B p ), and Poynting flux (v f ・ B p 2 ) for slit I (05:19 UT burst) and slit II (05:26 UT burst). (1) Temporal Evolution: Qualitatively, both of the estimated reconnection rates ( v f ・ B p ) and Poynting fluxes ( v f ・ B p 2 ) reconstruct peaks of the light curves of the nonthermal emissions. We made extensive use of Yohkoh and SOHO MDI Data Service. B c ・ v i = B p ・ v f B c 2 ・ v i ∝ B p 2 ・ v f Reconnection rate Poynting Flux (Conservation of magnetic flux) ( B c ∝ B p is assumed) The difference between the spatial distributions radiation sources are caused by the difference of released energy. Comparing H  and HXR images, we found the difference between the spatial distribution of the H  kernels and that of the HXR sources: only a few sources, which are accompanied by the H  kernels, are seen in the HXR images, while we can see two-ribbon structure with many H  kernels in the H  images. IAU 223 Symposium, St. Petersburg, June 14 – 19 2004 Sartorius telescope @Kwasan Obs. Flare 2001 April 10, 05:00UT @NOAA 9415 GOES X2.3 Data H  …Kwasan Obs., Sartorius Telescope Magnetogram…SOHO / MDI hard-X ray (HXR)…Yohkoh / HXT Microwave…Nobeyama Radioheliograph Here, we estimate the reconnection rate v f ・ B p, and the Poynting flux v f ・ B p 2 along the slits which pass the HXR sources, as the representations of the energy release rates. BpBp vfvf neutral line other H  kernels weak energy release Since it is difficult to estimate corona physical values ( B c, v i ), by using the conservation law of magnetic flux, we estimate the energy release rate with observable values ( B p, v f ). conservation of magnetic flux flare ribbon B c : coronal magnetic field strength v f : speed of ribbon separation Fig.4 Method of the analyses newly reconnected loop microwave HXR reconnection rate Poynting flux HXR burst at 05:19UT microwave HXR reconnection rate Poynting flux 4. RED ASYMMETRY slit I slit II HXR burst at 05:26UT slit I slit II slit (2) Spatial Distribution: 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 H  kernels. Table 1 Comparison of the reconnection rates and the Poynting fluxes between the H  kernels with HXR sources and those without ones reconnection rate (ratio) v f ・ B p [V m -1 ] Poynting flux (ratio) v f ・ B p 2 [erg cm -2 s -1 ] K1 2.6×10 2 (0.52) 1.3×10 9 (0.27) K2 7.7×10 3 (16) 7.6×10 11 (150) K3 4.9×10 2 (1.0) 5.0×10 9 (1.0) K3 K1 K2 K2 : HXR sources 5. Summary +1.5 A-1.5 A redblue bright dark The brighter kernel, the redder it is. Red-asymmetry is stronger at HXR sources. intensity of kernel blue red I blue -I red 0 We examined spatially resolved red-asymmetry distribution. Precipitation of nonthermal particles cause downward motion of chromospheric plasma  reddening in H  Fig.6 A spectrum at an H  kernel Fig.7 Scatter plot of reddening and H  kernel intensity