ASAI Ayumi Kwasan Observatory, Kyoto University

July 12, 2002 @Nobeyama

Evolution of Flare Ribbons and Energy Release

“re”-connection of magnetic field line

Released energy by reconnection or induced energy into th

e region↑

Estimate by using physical values at t

he footpoints

Model of Magnetic Reconnection

Energy Release RatedE/dt depends on m

agnetic field B and inflow velocity vi

Assumingvi ⇒ vfoot

Bcorona ⇒ Bphotosphe

Examine the relation of these values with energy

release rate

32

4BAv

B

dt

dEi

Reconnection model indicates

A : area of the reconnection region

Energy Release Rate

Energy Release Rate

32

4BAv

B

dt

dEi

Reconnection model indicates

A : area of the reconnection region

Energy Release Rate

Time profile of HXR intensity is well fitted wi

th that of dE/dt

Flare・ 05:10 UT April 10, 2001・ GOES X2.3 class・ NOAA 9415

DataH ･･ Kwasan Observatory, Sartorius Telescopemagnetogram ･･ SOHO / MDIhard-X ray ･･ Yohkoh / HXTmicrowave ･･ Nobeyama Radioheliograph

Observation

H image taken with FMT at Hida Obs.

NOAA 9415

Sartorius Telescope

H Movie of the Flare

East West

Great Two-Ribbon Flare

Thanks to short exposure time,

fine structure inside the flare ribbons is

clearly seen.

E4

E3E2

E1

W4

W3 W2

W1HXR sources

HXR Sources

contour lines : magnetic fieldPositive / Negative

E2

W2

Measure the magnetic field strength along the outer sides of flare ribbons.

North

South

SOHO/MDI

Magnetic Field Strength and HXR Radiation

Magnetic Field Strength

E3E1

E2

E4

W3

W2

W1 W4

HXT source

HXT source

+

-

North South

North

South

positive

negative

Magnetic Field Strength

・ H kernels without HXT sources

: 300 ～ 550 G

・ HXT sources : 1200 ～ 1350 G

( ～ 3 times larger)

E1 : 300E2 : 1350E3 : 550E4 : 500

W1 : 300W2 : 1200W3 : 500W4 : 450

Magnetic Field Strength (G)

E4

E3

E1

W4

W3E2W2W1

E2W2

32

4BAv

B

dt

dEi

↓

Energy release rate of the HXR sources is 16-27 times larger than the energy release rate of

the other H kernels. It is larger than the HXT

dynamic range.

Estimation of energy release rate at each source

vi : inflow velocityA : area of reconnection point

32

4BAv

B

dt

dEi

vi : inflow velocity B∝

2+

= 0.5 (Sweet-Parker)

1 (Petschek)

magnetic field strength is 3 times larger

Magnetic Field Strength and Energy Release Rate

Evolution of Flare Ribbon

To examine separation of ribbons, we estimated the distance of the fronts of the ribbons from neutral line in the direction perpendicular to neutral line.

05:10

05:40

××

WestEastt

ｒ ｒ

Separation of Flare Ribbons

HXR sources appear when separation speed of flare ribbons slow down

×

WestEast

dis

tan

ce

fro

m n

eu

tral

lin

e

time time

Separation speed and HXR Sources

32

4BAv

B

dt

dEi

Slowing down of the ribbon-separation is caused by increase of magnetic field strength.

Both B and vi must be considered simultaneously Reconnection Rate and/or Poynting Flux

HXR sources appear when separation speed of flare ribbons slow down→inverse dependence!?

Separation Speed and Energy Release Rate

32

4BAv

B

dt

dEi

•Reconnection rate

Bcoronavi = Bphotospherevfoot

•Poynting Flux

Bcorona2vi ∝ Bphotosphere

2vfoot

Reconnection Rate and Poynting Flux

Reconnection Rate and Poynting Flux

Bphotosphere

Separating Speed

Distance from NL

B2×v

B×v

Microwave

HXR

Reconnection Rate and Poynting Flux

Summary (1)

The magnetic field strengths at the HXR sources are about 3 times larger than at the other H kernels.

This suggests that the energy release rate at the HXR sources is 16-27 times larger than those of the other H kernels.

32

4BAv

B

dt

dEi

3

2

4BAv

B

dt

dEi

2+

Summary (2)

The HXR sources appear when the separating speed of the flare ribbons are slowing down.

This seems to be inversely dependence on the energy release rate.

Summary (3)

There are good correlations between the energy release rate and the reconnection rate and poynting flux.