Flare Ribbon Expansion and Energy ReleaseAyumi ASAI

Kwasan and Hida Observatories, Kyoto University

Explosive Phenomena in Magnetized Plasma – New Development of Reconnection Research –

March 17 – 19, 2004 @Kyoto

1. INTRODUCTIONMagnetic reconnection mechanism is a key process for the energy release and the particle acceleration during solar flares. We estimated the amount of the

released energy quantitatively, based on the magnetic reconnection model and by using observable values.

We estimate the energy release rate, by using the separation speeds of two ribbons and the photospheric magneti

c field strengths. The estimated reconnection rate and the Poynting flux along each slit show good correlation with the nonthermal

bursts (Fig. 5). They are also locally large enough at the HXR sources, and can explain the difference of spatial distributions betw

een HXR and H images. For more accurate estimation, we have to take into account the relation bet

ween Bc and Bp

Fig.2 H image overlaid with HXR contour image

HXR sourcesstrong energy release

AvBdtdE

ic

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 : in flow velocity A : area of reconnection region

3. RESULTS

The dynamic range of HXT is about10. Therefore, if the released energy at the HXR sources are (at least) 10 times larger than

those at the other H kernels, the difference of appearance can be explained.

Fig.3 Cartoon of magnetic reconnection

Slits were put in the direction of the flare ribbon separation, and calculated Bpvf and

Bp2vf at the outer edges of fla

re ribbons.We followed the temporal ev

olutions of these values.

Fig.5 Time profiles of microwave (NoRH 17GHz), HXR (Yohkoh/HXT), reconnection rate (Bpvf), and Poynting flux (Bp2vf) for slit I (05:

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

Qualitatively, both of the estimated reconnection rates (Bpvf) and Poynting fluxes (Bp

2vf) reconstruct peaks of the light curves of the nonthermal emissions.

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

Bcvi = Bpvf

Bc2vi ∝ Bp

2vf

Reconnection rate

Poynting Flux

(conservation of magnetic flux)

(Bc B∝ p is assumed)

The difference of the spatial distributions are

caused by the difference of released

energy!?

Comparing the H images with the HXR images (Fig 2.), we found the difference between the spatial distribution of the H

kernels and that of the HXR sources: only two sources, which are accompanied by the H kernels, are seen in the HXR image.

Sartorius telescope @Kwasan Obs.

Flare (Fig 1.)April 10, 2001 05:00UTNOAA 9415GOES X2.3DataH…Kwasan Obs., Sartorius Tele.Magnetogram…SOHO / MDIhard-X ray (HXR)…Yohkoh / HXTMicrowave…NoRH

Here, we estimate the reconnection rate Bpvf, and the Poynting flux Bp

2vf along the slits which pass the HXR sources, as the parameters of the energy release rates.

Bpvf

neutral line

other Ha kernelsweak energy release

Although it is very difficult to estimate corona physical values (Bc, vi), assuming the conservation law of magnetic flux, and using observable values (Bp, vf ), we estimate

the energy release rate.conservation of magnetic flux fpic vBvB flare ribbon

Bc : coronal magnetic field strengthvf : speed of ribbon separation

Fig.4 Method of the analyses

reconnected loop

microwave

HXR

reconnection rate

Poynting flux

HXR burst at 05:19 UT

microwave

HXR

reconnection rate

Poynting flux

4. SUMMARY

slit I slit II

HXR burst at 05:26 UT

slit I slit II

slit

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) Bpvf 　 [V m-1]

Poynting flux (ratio)vfBp

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

K1K2

K2 : HXR sources

P1