Spatially Resolved Spectral Analysis of Gradual Hardening FlareTakasaki 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

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 peakIntroductionTsuneta 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??

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

SpectralHXRMicrowave 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

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

temporal variation of spectral indexIn 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 GHzNOT imaging spectroscopyNOT imaging spectroscopy

= 9.5107 E1.5/ NL-band (14-23 keV)M1-band (23-33keVM2-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)In this flare, HXR is emitted from precipitating electrons which are once trapped in coronal loops!

Nov. 25, 2000 01:21(UT)GOES class M8.2

Identification of hardening HXR sourceHard X-ray contour on Ha imageHXR 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.

34 GHz microwave emissionFor 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.

Spatial distribution of microwave sourcesat peaks of time profiledirect precipitation componentprecipitation after trap componentMirroring componentmicrowave is dominantly emitted at western footpoint.microwave is dominantly emitted at looptop.at valleys of time profileIn the microwave, we can also see the trapped component.

Brief summary of flare configurationMicrowave HXRHXR 800 Gauss70 GaussHa ribbon-70 gauss+800 gaussSoHO/MDItrapped electrons

Spatially resolved spectral index (footpoint)rectangle AElectron spectral index (HXR)Electron spectral index (Microwave)HXR is emitted at only rectangle CTotal emission (from rectangle A)Total emission (from rectangle C)HXR; 1.0(thick target)Microwave; 1.22 /0.9 (Dulk, 1985)HXRNoRH (17GHz)A

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

microwaveElectron spectral index (HXR)HXR is emitted at only rectangle CTotal emission (rectangle B)Total emission (rectangle C)HXR; 1.0 (thick target)Microwave; 1.22 /0.9 (Dulk, 1985)HXRElectron spectral index (Microwave)Spatially resolved spectral index (looptop)BCNoRH (17GHz)

BCSpectral indeces of microwave (B) and HXR (C) show quit different evolution.different from footpoint population.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.

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