Preflare Features in Radios and in Hard X-Rays Ayumi ASAI Nobeyama Solar Radio Observatory, NAOJ collaborated with H. Nakajima, M. Shimojo, H. S. Hudson, R. P. Lin, and S. M. White AOGS 2nd Annual Meeting, June 22, 2005

Energy Release in Preflare Phase Impulsive phase: Strong nonthermal emission in HXRs and in microwaves Fast reconnection, violent energy release Preflare phase: Gradual emission in SXRs, start of plasmoid ejection/CME destabilization of preflare structure Physical process in preflare phase has a key of flare trigger

Nonthermal Emission strong energy release  HXR microwave Masuda et al. (1994) strong energy release  HXR thick-target : footpoint thin-target : above loop top (nonthermal?/thermal?) microwave flare loop particle acceleration in preflare phase? (Farnik et al. 2003) fast shock flare loop

Observation Flare NOAA 10039 2002/July/23 00:20 UT NOAA 10039 (SE limb) GOES X4.8 Light Curve SXR(GOES)、HXR(RHESSI)、 microwave(Nobeyama Radioheoigraph) NOAA 10039 Divide them into 4 sub-phases, and examine each of them

(Phase 1) Before the Flare Large loop-like structure (m-wave) Thin-thermal emission (a~0) Not clear in EUV  high temperature (~5MK)? Like a sigmoid?

(Phase 2) Preflare Phase I Rapid temperature increase (SXR, GOES)：hotter than 10MK Low energy HXR emission thermal emission? 17GHz 12-25 keV

(Phase 2) Preflare Phase II Nonthermal emission (a~-3.0) Above-the-loop-top source (Masuda’s source?)

(Phase 3) Ejection Faint EUV ejection Associated CME Induce intense energy release slit

(Phase 4) Impulsive Phase The physical features are almost the same as in the impulsive phase HXR Footpoint (nonthermal) Above-the-loop-top (thermal?/nonthermal?) microwave Loop / loop top (nonthermal) Above-the-loop-top source? Masuda et al. (1994)

Ejections and Energy Release Destabilization of the structure (tether-cutting / breakout) Plasmoids/filaments start to rise Induce strong energy release (impulsive phase) Nonthermal emission even in the phase BEFORE the ejection Destabilization process is accompanied by particle acceleration HXR time

Summary We examined the preflare features of 2002 July 23 flare in HXRs and in microwave Faint EUV ejection at 00：24UT Induced fast energy release in the impulsive phase We found the thermal and nonthermal features even in the phase before the ejection Nonthermal emission @ footpoin and above the loop top Masuda’s HXR sources? Energy release mechanism in the preflare phase is probably accompanied by particle acceleration

ようこうで探るプリフレア現象 Farnik (1996) リム付近で発生したフレアの統計解析 41/131(~31%)イベントでプリフレア エネルギー解放の場所は上空か? 優位な差は見られず gray scale: preflare

ようこうで探るプリフレア現象 Farnik and Savy (1998) プリフレア相増光の領域の一部は、フレアループと重なっている事が多い。　しかし、２つの領域が完全に一致する物は少ない gray scale: preflare contour: flare GOESでフレアと認識されなくてもプリフレア現象が起きている場合あり!

Tether-Cutting Model 強くシアした磁力線 Moore et al. (2001) ApJ 強くシアした磁力線 足元付近で磁気リコネクションすることにより、磁力線の支え(tether)を切る(cutting) 不安定になり、上部(filament)が上昇、CMEに

Temperature Variation in Preflare Phase Shimojo (1999) Date:20-Sep-1997 09:30UT Blue con. : 4MK Green con. : 5MK Red con. : 6MK SXT Image 09:20:37UT 09:09:09UT Temp. Map 09:27:01UT 09:30:31UT 09:32:35UT