Evolution of Flare Ribbons and Energy Release RateAyumi Asai1,2, T. Yokoyama T.3, M. Shimojo2, S. Masuda4, and K. Shibata1

1:Kwasan and Hida Observatories, Kyoto University 2: Nobeyama Radio Observatory, NAOJ

3: Dept. of Earth and Planetary Science, University of Tokyo4: Solar-Terrestrial Environment Laboratory, Nagoya University

1. INTRODUCTION

Magnetic reconnection is a key process for energy release and particle acceleration during solar flares. We quantitatively estimated the amount of the released energy, based on the

magnetic reconnection model and by using observable values.

We estimated the energy release rate, by using ribbon-separation speeds and photospheric magnetic field. The temporal evolution of the estimated reconnection rate and the Poynting flux reproduced the nonthermal bursts. They are locally large enough at the HXR sources, which can explain the difference of spatial distributi

ons of radiation sources.

We examined spatially resolved red-asymmetry distribution.

AvB

dt

dEi

c

4

2

2. ENERGY RELEASE RATE

Fig1. Hfull disk image obtained with Flare Monitoring Telescope at Hida Obs.

NOAA 9415

Energy release rate (dE/dt) is written as:

Bc : coronal magnetic field strength vi : inflow velocity A : area of reconnection region

Fig.2 Cartoon of magnetic reconnection

We put slits in the direction of the flare ribbon separation, and calculated vf ・ Bp and vf ・ Bp

2 at the outer edges of flare ribbons. We followed the temporal evolutions of these values.

Fig.4 Time profiles of microwave (NoRH), HXR (Yohkoh/HXT), reconnection rate (vf ・ Bp), and Poynting flux (vf ・ Bp2) for slit I (05:

19 UT burst) and slit II (05:26 UT burst).

(1) Qualitatively, both of the estimated reconnection rates (vf ・ Bp) and Poynting fluxes (v

f ・ Bp2) reconstruct peaks of the light curves of the nonthermal emissions.

We made extensive use of Yohkoh and SOHO MDI Data Service.

Bc ・ vi = Bp ・ vf

Bc2 ・ vi ∝ Bp

2 ・ vf

Reconnection rate

Poynting Flux

(Conservation of magnetic flux)

(Bc B∝ p is assumed)

RHESSI/SOHO/TRACE Workshop @Sonoma, California, Dec 8 – 11 2004

Sartorius telescope @Kwasan Obs.

Flare2001 April 10, 05:00UT @NOAA 9415GOES X2.3DataH…Kwasan Obs., Sartorius TelescopeMagnetogram…SOHO / MDIhard-X ray (HXR)…Yohkoh / HXTMicrowave…

Nobeyama Radioheliograph

Bpvf

neutral line

Fig.5 H image overlaid with HXR contour image

HXR sourcesstrong energy release

The spatial distribution of the H kernels is different from that of the HXR sources. The dynamic range of HXT is about10.

other H kernelsweak energy release

Since it is difficult to estimate corona physical values (Bc, vi), by using the conservation law of magnetic flux, we estimate the energy release rate with obs

ervable values (Bp, vf).

conservation of magnetic flux fpic vBvB

flare ribbon

Bc : coronal magnetic field strengthvf : speed of ribbon separation

Fig.3 Method of the analyses

newly reconnected loop

microwave

HXR

reconnection rate

Poynting flux

HXR burst at 05:19UT

microwave

HXR

reconnection rate

Poynting flux

3. RED ASYMMETRY

slit I slit II

HXR burst at 05:26UT

slit I slit II

slit

(2) Quantitatively, both of the reconnection rates and Poynting fluxes are enhanced enough (more than 10 times larger) at the HXR sources, compared with those at the other H kernels.

Table 1 Comparison of the reconnection rates and the Poynting fluxes between the H kernels with HXR sources and those without ones

reconnection rate (ratio)

vf ・ Bp 　 [V m-1]

Poynting flux (ratio)vf ・ Bp

2 [erg cm-2 s-1]

K1 2.6×102 (0.52) 1.3×109 (0.27)

K2 7.7×103 (16) 7.6×1011 (150)

K3 4.9×102 (1.0) 5.0×109 (1.0)

K3

K1

K2

4. SUMMARY

+1.5 A-1.5 A

red blue

bright

dark

The brighter kernel, the redder it is.

inte

nsi

ty o

f ke

rne

l

blue red

Iblue-Ired

0

We examined spatially resolved red-asymmetry distribution. Precipitation of nonthermal particles cause downward m

otion of chromospheric plasma reddening in H

Fig.6 A spectrum at an H kernel

Fig.8 Scatter plot of reddening and Hkernel intensity

So, the released energy at the HXR sources of (at

least) 10 times larger than those at the other H

kernels can explain the difference of appearance.

Reddening is conspicuous at the edge of flare ribbons

Fig.7 Spatial distribution of red-asymmetry

red blue

(Iblue-Ired)/(Iblue+Ired)/20

bright

dark

inte

nsi

ty o

f ke

rne

l

Normalized red-asymmetry no correlation with intensity.Downward vel. ~ constant

flux tube

H kernel