Flare Ribbon Expansionand Energy Release

Ayumi Asai

Nobeyama Solar Radio Observatory, NAOJ

April 6, 2005 @Nainital, India

Nobeyama Radioheliograph

• cadence: 1 sec• spatial resolution: 10”• 17 GHz / 34 GHz• flare, prominence,

sunspot• circular polarization

http://solar.nro.nao.ac.jp/

Flare Ribbon Expansionand Energy Release

Ayumi Asai

Nobeyama Solar Radio Observatory, NAOJ

April 6, 2005 @Nainital, India

Solar Flare

Magnetic Reconnection Model

• well explains observed phenomena

• phenomenologically succeeded

(Carmichael 1964; Sturrock 1966; Hirayama 1974; Kopp-Pneuman 1976)

• still needs to be checked quantitatively and qualitatively

magnetic reconnection

H flare ribbons

2001-4-10 flare (Hida Obs.)

Flare Ribbons

size : 104 – 105 kmduration : 10 min – 10 hours

What can we learn from Flare Ribbons?

• Two elongated bright regions (two ribbon) on each side of magnetic neutral line

• Two ribbons have the opposite magnetic polarity (N/S) to each other

• Two ribbons separate to each other with a speed of about several 10 km/s in earlier phase, and decelerated to about several km/s in later phase

• Correspond to the footpoints of post-flare loops

What can we learn from flare ribbons?

H images taken with Sartorius TelescopeEast West

Flare• April 10, 2001• 05:10 UT

• GOES X2.3

NOAA 9415

2001-April-10 Flare

DataH ･･ Sartorius Telescope,

Kyoto University (H center)

EUV ・・ TRACE (171A)

HXR ・・ Yohkoh/HXTmicrowave ・・

Nobeyama Radioheliographmagnetogram ・・ SOHO/MDI

Sartorius Telescope (Kwasan Obs.)

Observations

simultaneously brighten

• Nonthermal particles and thermal conduction bombard the chromospheric plasma at both the footpoints simultaneously

The temporal evolution of both the footpoints is very similar(Sakao 1994)

• We identify the conjugated pairs of the footpoints which show similar light curves

N S

?

1. Conjugacy of H Footpoints

1.divided flare ribbons into fine meshes

2.determine “conjugated footpoints” by using cross-correlation function

red:positive, blue:negative

Conjugacy of H footpoints

TRACE 171A

The TRACE loops really connect the

pairs.

TRACE Flare Loops

East West

The pairs are classified according to the times of brightening

Temporal evolution of H kernels

Movement of the site of energy release

t

Focus on Each Pair

2. Energy Release Rate

• quantitative estimation of the amount of the released energy, based on the magnetic reconnection model and by using observable values

test the reconnection model

AvB

dt

dEW in

c

42

2

Reconnection model indicates

Bc : coronal magnetic field strengthvin : inflow velocityA : area of the reconnection region

Electric Field

fpinc vBvBE

Bc : coronal magnetic field strengthBp : photospheric magnetic field strengthvin : inflow velocityvf : separation speed of flare ribbons

Energy Release Rate

conservation of magnetic flux

Poynting Flux

fpinc vBvBW 22 I estimate the energy release rate, by using observable values (Bp, vf)

It is very difficult to estimate physical values (Bc, vi

n) in the corona

I estimate the reconnection rate vB, and the Poynting flux vB2 as the representations of the ener

gy release rates.

Bv

Neutral Line

Evolution of Flare Ribbons

Evolution of Flare Ribbons

Bv

I estimate the reconnection rate vB, and the Poynting flux vB2 as the representations of the ener

gy release rates.

Neutral Line

Evolution of Flare Ribbons

Neutral Line

Bv

I estimate the reconnection rate vB, and the Poynting flux vB2 as the representations of the ener

gy release rates.

H image

HXR sourcesflare ribbons

Energy Release Rate

Energy Release Rate

HXRIW

We compare the derived energy release rate with HXR light curves

Reconnection Rate and Poynting Flux

microwave

HXR

reconnection rate

Poynting flux

An HXR burst occurred on the slit (05:19 UT).

Reconnection Rate and Poynting Flux

microwave

HXR

reconnection rate

Poynting flux

An HXR burst occurred on the slit (05:26 UT).

Quantitative Estimation

E4

E3

E1

W4

W3E2W2

W1 Comparison of Poynting and Electric Field (Reconnection Rate) between the H kernels with HXR sources and those without ones

E2W2

• H line is shifted red-ward

red-asymmetry• velocity : 50-100 km/s

H

H spectrumIchimoto & Kurokawa 1984flare

chromosphere

corona

compression

X-ray

H line

3. H kernel spectroscopy

Red-Asymmetry Map

• we calculated 　　　　　　　　　　　　　

　　　　　　　 as an indicator of r.a.

• all over the flare ribbon, the tendency of r.a. is seen

2/)( bluered

bluered

II

II

map

2/)( bluered

bluered

II

II

Red-Asymmetry Distribution

• strong asymmetry @outer edges of the flare ribbon

1000~3000 km (?)

• at HXR sources, r.a. is not necessary strong

Scatter plot (intensity vs RA)

• Iblue-Ired vs r.a. scatter plot

• the brighter the kernel is, the stronger the r.a. isin

tens

ity o

f H

ker

nel

red blue

Summary

• We can learn from H flare ribbons:• Select conjugated footpoints by calculating

the cross-correlation function• Estimate energy release rate, by using the

separation motions of two ribbons and the photospheric magnetic field strengths

• Examine red-asymmetry distribution by using H wing data

2D / 3D

observed as H flare ribbons

Temporal evolution of Red-Asymmetry

• red-asymmetry peak precedes the HXR/microwave peaks (HXR bursts are not necessary associated with strong red-asymmetry)

bright in red bright in blue

bright

dark

Scatter Plot

より明るいカーネルほど、赤でより明るい

red asymmetryがより強く出ていることを示唆 ?

Haカーネルの強度

H カカカカのライトカーブ場所によってさまざまなライトカーブを示す

Neupert Effect

• The shape of light curves in HXRs and microwaves correspond to the time-derivative of SXR ones!

(Neupert 1968)

• Radiation in SXRs ~ total energy

HXR/microwave radiations ~ energy release rate

Idt

dISXR HXRSXR I

dt

dI

H線での放射

• 非熱的粒子や熱伝導がフレアループに沿って伝播し、足元で彩層に突入する

H カカカカカカカH カカカカカカカカカ• エネルギー解放したループの足元の場所が分かる

Hフレアリボンとして観測

　彩層

コロナ

Hカーネルと硬 X線放射源

• フレア (磁気リコネクション )に伴い、硬 X線で非熱的な放射源が生成

• 非熱的・高エネルギー粒子が彩層に突入

硬 X線放射源と H カカカカを生成

非熱的・高エネルギー粒子の彩層突入

硬 X線

制動放射急激な熱化など

H カ