2. Data3. Results full disk image (H  ) of the flare (Sartorius Telescope) NOAA Abstract Preflare Nonthermal Emission Observed in Microwave and Hard X-Rays Ayumi ASAI 1, Hiroshi NAKAJIMA 1, Masumi SHIMOJO 1, Stephen M. WHITE 2, Hugh S. HUDSON 3 1: Nobeyama Solar Radio Observatory/NAOJ, 2:University of Maryland, 3:University of California Berkeley We examined the preflare features of 2002 July 23 flare in HXRs and in microwave Faint EUV ejection is identified at 00 ： 24UT  which Induced fast energy release in the impulsive phase We found the thermal and nonthermal features even in the phase before the ejection Nonthermal footpoint and loop top Masuda’s HXR sources?  Energy release mechanism in the preflare phase is probably accompanied by particle acceleration micorwave emissions (nonthermal gyrosynchrotron;  <0) and HXR (higher energy) started to rise  nonthermal emission, even in the phase Flare 2002/July/23 00:20 UT NOAA (SE limb) GOES X4.8 Light Curve soft X-ray (SXR) : GOES hard X-ray (HXR) : RHESSI extreme ultraviolet (EUV) : TRACE (195 Å ) microwave : Nobeyama Radioheoigraph 5. Summary Impulsive phase: strong nonthermal emission (HXR, microwave)  violent energy release Preflare phase: gradual emission in SXRs, start of plasmoid ejection/CME, etc.  destabilization of the structure (tether-cutting / breakout) Physical process in preflare phase has a key of flare trigger Large loop-like structure is seen in microwaves Thin-thermal emission (  ~0) Not clear in EUV GOES temperature is ~5MK Like a sigmoid? Faint EUV ejection associated with small burst Flare-associated CME also starts to rise  Induce intense energy release slit The physical features are almost the same as in the impulsive phase  impulsive energy release HXR Footpoint (nonthermal) Above-the-loop-top (thermal?/nonthermal?) microwave Loop / loop top (nonthermal) Above-the-loop-top source!? Masuda et al. (1994) We present a detailed examination on the nonthermal emissions during the preflare phase of the large flare which occurred on 2002 July 23. The microwave (17 and 34 GHz) data obtained with Nobeyama Radioheliograph, at Nobeyama Solar Radio Observatory, and the hard X-ray data taken with RHESSI obviously showed nonthermal features. We found a faint ejection associated with the flare in the EUV images taken with TRACE. We also examined the temporal, spatial, and spectroscopic features on the emission sources. 1. Introduction tether-cutting (left) mode and breakout model (right) SXR plasmoid ejection Divide the preflare phase into 4 sub- phases, and examine each of them RHESSI NoRH GOES time profiles of the preflare phase of the flare Phase I Phase II Phase III Phase IV GOES temperature increased rapidly (hotter than 10MK) SXR/HXR (low energy) brightened  thermal emission? time profile of GOES temperature (left) EUV image of phase I overlaid with microwave contour, (right) the map of the microwave speatral index  phase II time slice image of TRACE EUV images type-III bursts are sometimes observed in the preflare phase, which implies particle acceleration in the phase  more direct evidences are required (?) phase IV Nonthermal emission even in the phase BEFORE the ejection (phase II)  Destabilization process is accompanied by particle acceleration