ASAI Ayumi Kwasan Observatory, Kyoto University July 12, Evolution of Flare Ribbons and Energy Release

“re”-connection of magnetic field line Released energy by reconnection or induced energy into the region ↑ Estimate by using physical values at the footpoints Model of Magnetic Reconnection

Energy Release Rate dE/dt depends on magnetic field B and inflow velocity v i Assuming v i ⇒ v foot B corona ⇒ B photosphe Examine the relation of these values with energy release rate Reconnection model indicates A : area of the reconnection region Energy Release Rate

Reconnection model indicates A : area of the reconnection region Energy Release Rate Time profile of HXR intensity is well fitted with that of dE/dt

Flare ・ 05:10 UT April 10, 2001 ・ GOES X2.3 class ・ NOAA 9415 Data H  ･･ Kwasan Observatory, Sartorius Telescope magnetogram ･･ SOHO / MDI hard-X ray ･･ Yohkoh / HXT microwave ･･ 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 E3 E2 E1 W4 W3 W2 W1 HXR sources HXR Sources contour lines : magnetic field Positive / 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 E3 E1 E2 E4 W3 W2 W1 W4 HXT source + - NorthSouth North South positive negative

Magnetic Field Strength ・ H  kernels without HXT sources : 300 ～ 550 G ・ HXT sources : 1200 ～ 1350 G ( ～ 3 times larger) E1 : 300 E2 : 1350 E3 : 550 E4 : 500 W1 : 300 W2 : 1200 W3 : 500 W4 : 450 Magnetic Field Strength (G) E4 E3 E1 W4 W3 E2 W2 W1 E2 W2

↓ Energy release rate of the HXR sources is 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 v i : inflow velocity A : area of reconnection point v i : 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 × × WestEast t ｒｒ Separation of Flare Ribbons

HXR sources appear when separation speed of flare ribbons slow down × West East distance from neutral line time Separation speed and HXR Sources

Slowing down of the ribbon-separation is caused by increase of magnetic field strength. Both B and v i 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

Reconnection rate B corona v i = B photosphere v foot Poynting Flux B corona 2 v i ∝ B photosphere 2 v foot Reconnection Rate and Poynting Flux

B photosphere Separating Speed Distance from NL B 2 ×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 times larger than those of the other H  kernels. 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.