1 / 10 Comparison between Microwave and Hard X-ray Spectral Indices of Temporally and Spatially Resolved Non-Thermal Sources Kiyohara, J., Takasaki, H., Narukage, N. (Kyoto Univ.), Masuda, S. (STE Lab., Nagoya Univ.), Nakajima, H. (NRO/NAOJ) Yokoyama, T. (Univ. Tokyo) Nobeyama Symposium Kiyosato

2 / 10 Introduction Non-thermal emission of flares are frequently observed simultaneously by microwave and hard X-rays. The time profiles of these frequencies are similar with each other. (Kundu 1961) These observations suggest that the electrons emitting microwave and HXRs belong to the same population in each event. However, it is observed that the indices of the power-law fit to the distribution functions in microwave and HXRs differ (Kundu et al 1994.; Silva et al. 1999; Raulin et al. 1998). In order to study this, we analyzed simultaneous observations of flares by NoRH, NoRP, and Yohkoh/HXT. The advantage of these observations is that they are spatially and temporally resolved.

3 / 10 Data Instruments –Yohkoh Hard X-ray Telescope (HXT) –Nobeyama Radioheliograph (NoRH) –Nobeyama Radio Polarimeters (NoRP) Event Selection – > 30 cts/s/SC in M2-band of HXT – (source size)/(beam size) >4 in NoRH image – 15 events analyzed in total

4 / 10 Power-law indices Power-law index in HXR spectrum –Assume the thick-target model –Electron index  x Power-law index in microwave spectrum –Observed NoRP spectrum is fitted by the broken- power-law model. –Taking the intensity ratio in different frequency obtained by NoRH –Only optically-thin part (high-frequency part) –Using Dulk’s (1985) fitting function –Electron index  m

5 / 10 Group 1 8 of 15 events Impulsive ( < 10min.) Power-law indices have similar values at the HXR peak Spatially compact in microwave HXT H-band 01:4401:52 29-Oct-2000 NoRP 17GHz xx mm

6 / 10 Group 2 3 of 15 events Gradual ( > 10 min.) Power-law indices show little change temporally Relatively large scale in microwave HXT H-band 03:2003:44 03-Apr-2001 NoRP 35GHz xx mm

7 / 10 Group 3 4 of 15 events HXT H-band 05:3805:43 28-Nov-1998 NoRP 17GHz xx mm

8 / event The HXR source is located at the part where the microwave spectrum is softer. HXR NoRH 34GHz Intensity NoRH spectral index SoftHard

9 / 10 HXR vs Microwave The HXR sources seem to be located at the part where the microwave spectrum is softer in general

10 / 10 Summary & Discussion Power-law indices  m and  x of electron distribution functions are derived from the microwave and hard X-rays spectra, respectively, in the impulsive phase of the selected events as functions of time and position. We found: 1. The selected events are categorized in three types by the temporal behavior of the delta. 2.The microwave spectrum near the footpoints is softer than that near the looptop. 3.Hard X-ray sources seem to be located at the area where such softer microwave spectra are seen. The previous studies show by using spatially-unresolved data that  x is generally larger than  m. Our findings, however, suggest that the previous results are because of the relatively weighted signal of microwave from the loop top which is emitted by trapped electrons. There still remains a possibility that the electron power indices have a single value from hard X-ray emitting energy around 100keV up to microwave emitting energy, which is believed to be > 0.3 MeV.