1. Fine Structure inside Flare Ribbons and its Temporal Evolution ASAI Ayumi 1, Masuda S. 2, Yokoyama T. 3, Shimojo M. 3, Kurokawa H. 1, Shibata, K. 1, Ishii T. T. 1, Isobe H. 1, Takasaki H. 1, Kitai R. 1, Yaji K. 4 1: Kwasan Observatory, 2: STE lab., 3: Nobeyama Radio Obsevatory, 4: Kawabe Cosmic Park January 22, 2002, Yohkoh 10 th Anniv. Meeting

2. Foot Point of Flare Loop Non-thermal particles bombard the chromospheric plasma at both the foot points simultaneously. The temporal evolution of both the foot points is very similar. (Sakao 1994) ? simultaneously brighten From the site of highly-correlated pair of foot points and the time of precipitation, the site and the time of particle acceleration can be determined.

3. Foot Point of Flare Loop precipitation of non-thermal particles HXR bremsstrahlung rapid thermalization HH Precipitations of particles cause HXR sources and H  kernels. HXR sources and H  kernels show high correlation in their locations and their temporal evolutions. (Kitahara & Kurokawa 1990)

4. Foot Point of Flare Loop HXR H  images enable us to investigate precipitation of non- thermal particles into the chromosphere with higher spatial resolution than HXR and/or microwave. (Kurokawa 1988) HH Soft X-ray

5. Today’s Topic ・ We determine precisely the site of precipitations using the H  data of the 2001 April 10 flare. ・ We compare the spatial distribution of the HXT sources with the H  kernels and discuss the energy release at the HXT sources.

6. Observation Flare ・ 05:10 UT April 10, 2001 ・ GOES X2.3 class ・ NOAA 9415 Data H  ･･ Kwasan Observatory, Sartorius Telescope EUV ･･ TRACE (171 Å image) magnetogram ･･ SOHO / MDI hard-X ray ･･ Yohkoh / HXT microwave ･･ Nobeyama Radioheliograph H  image taken with FMT at Hida Obs. NOAA 9415 Sartorius Telescope

7. H  Movie of the Flare Great Two- Ribbon Flare Thanks to short exposure time, fine structure inside the flare ribbons is clearly seen.

8. Method of Data Analysis ① Divided both the flare ribbons into fine meshes. Examined light curves of each box. 1 mesh box : ～ (3.2 arcsec) 2 ; RED is positive,BLUE is negative.

9. Method of Data Analysis ② Using cross-correlation functions of the light curves, we identified the conjugate foot points in each mesh.

10. TRACE Flare Loop TRACE 171 Å images show post- flare loops of 1MK plasma. The TRACE flare loops really connect the pairs.

11. Time of Brightening The pairs are classified according to the times of brightening.

12. Temporal Evolution of H  Kernels Movement of the site of energy release. t

13. Summary (1)  We have invented a unique method for analyzing H  data.  We have investigated the site of the precipitation of particles with higher spatial resolution.  We have followed the history of the energy release.

14. E4 E3 E2 E1 W4 W3 W2 W1 HXT sources HXT Sources contour lines : magnetic field Positive / Negative E2 W2

15. Magnetic Field Strength ・ H  kernels without HXT sources : 300 ～ 550 G ・ HXT sources : 1200 ～ 1350 G ( ～ 3 times larger) E1 : 300 E2 : 1350 E3 : 550 E4 : 500 W1 : 300 W2 : 1200 W3 : 500 W4 : 450 Magnetic Field Strength (G) E4 E3 E1 W4 W3 E2 W2 W1 E2 W2

16. Magnetic Field Strength and Energy Release Rate 3 times larger magnetic field strength causes 27 times larger energy release rate at the HXT sources than those of the other H  kernels. It is larger than the HXT dynamic range. Estimation of energy release rate at each source v i : inflow velocity A : area of reconnection point v i : inflow velocity ∝ B I HXT ∝ dE/dt

17. Summary (2)  We have found the differences of the magnetic field strengths between the HXT sources and the other H  kernels. Those at the HXT sources are about 3 times larger than at the other H  kernels.  Using H  data, we have been able to investigate the weaker brightenings where less energy release occur and cannot be seen in HXT.

18. Magnetic Field Strength and Energy Release Rate Energy release rate of the HXT sources is 16-27 times larger than the energy release rate of the other H  kernels. Estimation of energy release rate at each source v i : inflow velocity A : area of reconnection point v i : inflow velocity ∝ B a 2+a a = 0.5 (Sweet-Parker) 1 (Petschek)

19. Light Curves of the Flare Light curves of the flare The H  light curve of the flares also shows gradual rise like the SXR (GOES) light curve. Sartorius HXT (H) GOES NoRH

20. Light Curve of H  Kernels Light curves of each H  kernels show impulsive spikes like those of nonthermal radiation. Each H  kernel are generated by precipitation of nonthermal particles.

21. Time of Brightening

22. Magnetic Field Strength and Nonthermal Radiation Measure the magnetic field strength along the outer sides of flare ribbons.

23. Magnetic Field Strength E3 E1 E2 E4 W3 W2 W1 W4 ・ H  kernels without HXT sources : 400 ～ 500 G ・ HXT sources : 1200 ～ 1400 G ( ～ 3 times larger) HXT source 北南 + -