1. Spatially Resolved Spectral Analysis of Gradual Hardening Flare Takasaki H., Kiyohara J. (Kyoto Univ.), Asai A., Nakajima H. (NRO), Yokoyama T. (Univ. of Tokyo), Sato J. ( STEL/Nagoya-U.), Kosugi T. (JAXA) Oct, 27, 2004 Nobeyama

2. gradual hardening flares (Kosugi et al. 1985)  long duration event and gradual variation in the HXR and microwave fluxes.  HXR emission with a spectrum that systematically hardens with time (the power-law spectral index is reaching ≦ 3)  the energy dependence time delay of microwave and HXR peak Introduction Tsuneta et al. (1984) reported that the gradual hardening HXR source located on apex of coronal loop.  It is suggested that the magnetic trapping of energetic electrons plays significant role in this type of flares!!!  Really??

3. How is gradual hard flare seen in microwave? Light Curve HXR time profile ~ microwave time profile one-to-one correspondence of individual spikes between HXR and microwave in their time profiles  HXR and microwave are generated by a single population of energetic electrons accelerated in the flare energy-release process.

4. N E Spectral δ HXR ≠δ Microwave  Implies “not single population” !!!? There is a breakup in the energy spectrum of the electrons. However, previous works (of the light curves / of the spectral) are performed without spatial resolution.  “spatially resolved” spectral distribution (imaging spectroscopy) is needed.  NoRH + HXT : use images in both wavelengths

5. Nov. 25, 2000 01:21(UT) GOES class M8.2 Data Yohkoh/HXTGOES

6. temporal variation of spectral index In HXR, a soft-hard-harder temporal variation of electron spectral index. Temporal behavior and value of microwave spectral index is different from those of HXR. This is calculated by 1, 2, 3.75, 9.4, 17, 34 GHz NOT imaging spectroscopy This is calculated by M2 and H-band NOT imaging spectroscopy

7. τ= 9.5×10 7 E 1.5 / N L-band (14-23 keV) M1-band (23- 33keV ） M2-band (33-53 keV) H-band (53-93 keV) Time delay of HXR peak emission Energy dependence of HXR time profiles energy dependence of particle trapping (Coulomb collision) (Spitzer, Physics of Fully Ionized Gases) ±0 ＋2＋2 ＋4＋4 ＋8＋8 ＋2＋2 ＋4＋4 In this flare, HXR is emitted from precipitating electrons which are once trapped in coronal loops!

8. NoRH (34GHz) EIT (195 Å ) Nov. 25, 2000 01:21(UT) GOES class M8.2

9. Identification of hardening HXR source Hard X-ray contour on Ha image HXR is emitted at footpoint. the dominant hard X-ray source appears as a single source located above the Ha bright point in eastern- ribbon and the temporal and spatial variation of this HXR source is correspond with the variation of this Ha bright point.

10. 34 GHz microwave emission For the impulsive phase of each peak, the microwave emission from the western footpoint was considerably larger than that from the looptop. After peak, on the contrary, the emission of loop top is larger than that of footpoint.

11. Spatial distribution of microwave sources at peaks of time profile → direct precipitation component → precipitation after trap component → Mirroring component → trapping component microwave is dominantly emitted at western footpoint. microwave is dominantly emitted at looptop. at valleys of time profile In the microwave, we can also see the trapped component.

12. Brief summary of flare configuration Microwave HXR ＋ 800 Gauss － 70 Gauss Ha ribbon × -70 gauss +800 gauss SoHO/MDI trapped electrons

13. Spatially resolved spectral index (footpoint) δ rectangle A Electron spectral index (HXR) Electron spectral index (Microwave) ※ HXR is emitted at only rectangle C Total emission (from rectangle A) Total emission (from rectangle C) HXR; δ ＝ γ ＋ 1.0 (thick target) Microwave; δ ＝（ 1.22 – α ） /0.9 (Dulk, 1985) δ HXR NoRH (17GHz) A

14. 1.Spectral indeces of microwave (A) and HXR (C) show quit similar evolution.  Single population at footpoint emission!!!?  Both are mainly once-trapped electrons. 3.Peak times of microwave (A) delay for ～ 15 sec from those of HXR (C). 2.There is a constant gap between δ Microwave and δ HXR ; (δ HXR -δ Microwave ～ 2).  NOT single power-law!!??  … depends on theoretical or not ??? A B C

15. δ microwave Electron spectral index (HXR) ※ HXR is emitted at only rectangle C Total emission (rectangle B) Total emission (rectangle C) HXR; δ ＝ γ ＋ 1.0 (thick target) Microwave; δ ＝（ 1.22 – α ） /0.9 (Dulk, 1985) δ HXR Electron spectral index (Microwave) Spatially resolved spectral index (looptop) B C NoRH (17GHz)

16. B C 1.Spectral indeces of microwave (B) and HXR (C) show quit different evolution.  different from footpoint population. 2.Peak time of microwave (B) delay for ～ 30 sec. from those of HXR (C).  The energy of electrons which produce microwave emission at looptop are larger than those at the footpoint if we assume the Coulomb collision.

17. Summary We performed imaging spectroscopy on a gradual hardening flare. 1. Electrons which produce HXR and microwave at footpoint are probably produced by same population, 2.But, there is a gap which we can not explain … 3.They mainly precipitate after trapping. 4.The energy of electron in looptop may be larger than that in footpoint, and these electrons may be strongly trapped.