Preflare features in radios and in hard x rays
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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 2 nd Annual Meeting, June 22, 2005. Energy Release in Preflare Phase. Impulsive phase:

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Preflare Features in Radios and in Hard X-Rays

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Preflare features in radios and in hard x rays

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

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

Nonthermal Emission

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

Observation

NOAA 10039

Flare

2002/July/23 00:20 UT

NOAA 10039 (SE limb)

GOES X4.8

Light Curve

SXR(GOES)、HXR(RHESSI)、

microwave(Nobeyama Radioheoigraph)

Divide them into 4 sub-phases, and examine each of them


Phase 1 before the flare

(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

(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

(Phase 2) Preflare Phase II

  • Nonthermal emission (a~-3.0)

  • Above-the-loop-top source (Masuda’s source?)


Phase 3 ejection

(Phase 3) Ejection

slit

  • Faint EUV ejection

  • Associated CME

  • Induce intense energy release


Phase 4 impulsive phase

(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

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

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


Preflare features in radios and in hard x rays

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


Preflare features in radios and in hard x rays

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

Tether-Cutting Model

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

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


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