Evolution of Flare Ribbons and Energy Release Rate Ayumi Asai 1,2, T. Yokoyama T. 3, M. Shimojo 2,...
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Evolution of Flare Ribbons and Energy Relea se Rate Ayumi Asai 1,2 , T. Yokoyama T. 3 , M. Shimojo 2 , S. Masuda 4 , and K. Sh ibata 1 1:Kwasan and Hida Observatories, Kyoto University 2: Nobeyama Radio Observatory, NAOJ 3: Dept. of Earth and Planetary Science, University of Tokyo 4: 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 releas e rate, by using ribbon-separa tion speeds and photospheric m agnetic field. The temporal ev olution of the estimated recon nection rate and the Poynting flux reproduced the nonthermal bursts. They are locally large enough at the HXR sources, whi ch can explain the difference of spatial distributions of ra diation sources. We examined spatially resolved red-asymmetry distribution. A v B dt dE i c 4 2 2. ENERGY RELEASE RATE Fig1. H full disk imag e obtained with Flare M onitoring Telescope at Hida Obs. NOAA 9415 Energy release rate (dE/dt) is written as: B c : coronal magnetic fi eld strength v i : inflow velocity A : area of reconnectio n region Fig.2 Cartoon of magnetic reconnection We put slits in the direction of the flare ribbon separation, and calculated v f ・ B p and v f ・ B p 2 at th e outer edges of flare ribbons. W e followed the temporal evolution s of these values. Fig.4 Time profiles of microwave (NoRH), HXR (Yohkoh/HXT), reconnection rate (v f ・ B p ), and Poynti ng flux (v f ・ B p 2 ) for slit I (05:19 UT burst) and slit II (05:26 UT burst). (1) Qualitatively, both of the estimated reconnection rates (v f ・ B p ) and Poynting fluxes (v f ・ B p 2 ) reconstruct peaks of the light curves of the nonthermal emissions. We made extensive use of Yohkoh and SOHO MDI Data Service. B c ・ v i = B p ・ v f B c 2 ・ v i ∝ B p 2 ・ v f Reconnection rate Poynting Flux (Conservation of magnetic flux) (B c B ∝ p is assumed) RHESSI/SOHO/TRACE Workshop @Sonoma, California, Dec 8 – 11 2004 Sartorius telescope @Kwasan Obs. Flare 2001 April 10, 05:00UT @NOAA 9415 GOES X2.3 Data H…Kwasan Obs., Sartorius Tel escope Magnetogram…SOHO / MDI hard-X ray (HXR)…Yohkoh / HXT Microwave… Nobeyama Radioheliograph B p v f neutral line Fig.5 H image overlaid with HXR contour image HXR sources strong 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 kernels weak energy release Since it is difficult to estimate cor ona physical values (B c , v i ), by using the conservation law of magnetic flux, we estimate the energy release rate wi th observable values (B p , v f ). conservatio n of magnetic flux f p i c v B v B flare ribbon B c : coronal magnetic field strength v f : 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 f lux 3. RED ASYMMETRY slit I slit II HXR burst at 05:26UT slit I slit II slit (2) Quantitatively, both of the reconnection r ates and Poynting fluxes are enhanced enough (more than 10 times larger) at the HXR source s, compared with those at the other H kernel s. Table 1 Comparison o f the reconnection r ates and the Poynti ng fluxes between th e H kernels with HX R sources and those without ones reconnection rate (ratio) v f ・ B p [V m -1 ] Poynting flux (ratio) v f ・ B p 2 [erg cm -2 s -1 ] K1 2.6×10 2 (0.52) 1.3×10 9 (0.27) K2 7.7×10 3 (16) 7.6×10 11 (150) K3 4.9×10 2 (1.0) 5.0×10 9 (1.0) K3 K1 K2 4. SUMMARY +1.5 A -1.5 A red blue bright dark The brighter kernel, the redder it is. intensity of kernel blue red I blue -I red 0 We examined spatially resolved red-asymmetr y distribution. Precipitation of nonthermal particles cause downward motion of chromosp heric plasma reddening in H Fig.6 A spectrum at an H kernel Fig.8 Scatter plot of reddening and H kernel 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 (I blue -I red )/(I blue +I red )/2 0 bright dark intensity of kernel Normalized red-asymmet ry no correlation wit h intensity. Downward vel. ~ consta nt flux tube H kernel
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Transcript of Evolution of Flare Ribbons and Energy Release Rate Ayumi Asai 1,2, T. Yokoyama T. 3, M. Shimojo 2,...
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
