Fine Structure inside Flare Ribbons and its Temporal EvolutionASAI Ayumi 1,

Masuda S. 2, Yokoyama T. 3, Shimojo M. 3, Kurokawa H. 1,Shibata, K. 1, Ishii T. T. 1, Isobe H. 1, Takasaki H. 1, Kitai R. 1, Yaji K. 41: Kwasan Observatory, 2: STE lab., 3: Nobeyama Radio Obsevatory, 4: Kawabe Cosmic Park

January 22, 2002, Yohkoh 10th Anniv. Meeting

Foot Point of Flare LoopNon-thermal particles bombard the chromospheric plasma at both the foot points simultaneously. The temporal evolution of both the foot points is very similar.(Sakao 1994)?simultaneously brightenFrom the site of highly-correlated pair of foot points and the time of precipitation, the site and the time of particle acceleration can be determined.

Foot Point of Flare LoopPrecipitations of particles cause HXR sources and Ha kernels.

HXR sources and Ha kernels show high correlation in their locations and their temporal evolutions.(Kitahara & Kurokawa 1990)

Foot Point of Flare LoopHXRHa images enable us to investigate precipitation of non-thermal particles into the chromosphere with higher spatial resolution than HXR and/or microwave.(Kurokawa 1988)HaSoft X-ray

Todays Topic We determine precisely the site of precipitations using the Ha data of the 2001 April 10 flare.

We compare the spatial distribution of the HXT sources with the Ha kernels and discuss the energy release at the HXT sources.

ObservationFlare 05:10 UT April 10, 2001GOES X2.3 classNOAA 9415

DataHaKwasan Observatory, Sartorius TelescopeEUVTRACE (171 image)magnetogramSOHO / MDIhard-X rayYohkoh / HXTmicrowaveNobeyama RadioheliographHa image taken with FMT at Hida Obs.NOAA 9415

Ha Movie of the FlareGreat Two-Ribbon Flare

Thanks to short exposure time, fine structure inside the flare ribbons is clearly seen.

Method of Data Analysis

Method of Data Analysis Using cross-correlation functions of the light curves, we identified the conjugate foot points in each mesh.

TRACE Flare LoopTRACE 171images show post-flare loops of 1MK plasma.

The TRACE flare loops really connect the pairs.

Time of BrighteningThe pairs are classified according to the times of brightening.

Temporal Evolution of Ha KernelsMovement of the site of energy release.t

Summary (1)We have invented a unique method for analyzing Ha data.

We have investigated the site of the precipitation of particles with higher spatial resolution.

We have followed the history of the energy release.

HXT SourcesHXT sourcescontour lines : magnetic fieldPositive / Negative

Magnetic Field StrengthHa kernels without HXT sources : 300550 G

HXT sources : 12001350 G( 3 times larger)E1 : 300E2 : 1350E3 : 550E4 : 500W1 : 300W2 : 1200W3 : 500W4 : 450Magnetic Field Strength (G)E4E3E1W4W3W1

Magnetic Field Strength and Energy Release Rate3 times larger magnetic field strength causes 27 times larger energy release rate at the HXT sources than those of the other Ha kernels.

It is larger than the HXT dynamic range.Estimation of energy release rate at each sourcevi : inflow velocityA : area of reconnection pointIHXT dE/dt

Summary (2)

We have found the differences of the magnetic field strengths between the HXT sources and the other Ha kernels. Those at the HXT sources are about 3 times larger than at the other Ha kernels.

Using Ha data, we have been able to investigate the weaker brightenings where less energy release occur and cannot be seen in HXT.

Magnetic Field Strength and Energy Release RateEnergy release rate of the HXT sources is 16-27 times larger than the energy release rate of the other Ha kernels.Estimation of energy release rate at each sourcevi : inflow velocityA : area of reconnection pointa = 0.5 (Sweet-Parker)1 (Petschek)

Light Curves of the FlareLight curves of the flare

The Ha light curve of the flares also shows gradual rise like the SXR (GOES) light curve.

Light Curve of Ha Kernels Light curves of each Ha kernels show impulsive spikes like those of nonthermal radiation.

Each Ha kernel are generated by precipitation of nonthermal particles.

Time of Brightening

Magnetic Field Strength and Nonthermal RadiationMeasure the magnetic field strength along the outer sides of flare ribbons.

Magnetic Field StrengthE3E1E2E4W3W2W1W4Ha kernels without HXT sources : 400500 G

HXT sources : 12001400 G( 3 times larger)HXT sourceHXT source+-