1. Flare Ribbon Expansion and Energy Release
Ayumi Asai
Nobeyama Solar Radio Observatory, NAOJ
April 6, India
First of all, I would like the SOCs and the LOCs for inviting me and their kind arrangements.
Today, I would like to present what can we learn from flare ribbon expansion.

2. Nobeyama Radioheliograph
cadence: 1 sec
spatial resolution: 10”
17 GHz / 34 GHz
flare, prominence, sunspot
circular polarization
I belong to Nobeyama Solar Radio Observatory, National Astronomical Observatory of Japan, which is located in the middle of Japan main island.
We have a radio interferometer named Nobeyama Radioheliograph.

3. Flare Ribbon Expansion and Energy Release
Ayumi Asai
Nobeyama Solar Radio Observatory, NAOJ
April 6, India
First of all, I would like the SOCs and the LOCs for inviting me and their kind arrangements.
Today, I would like to present what can we learn from flare ribbon expansion.

4. Solar Flare

5. Magnetic Reconnection Model
(Carmichael 1964; Sturrock 1966; Hirayama 1974; Kopp-Pneuman 1976)
well explains observed phenomena
phenomenologically succeeded
still needs to be checked quantitatively and qualitatively

6. magnetic reconnection
Flare Ribbons
magnetic reconnection
flare (Hida Obs.)
size : 104 – 105 km
duration : 10 min – 10 hours
Ha flare ribbons

7. 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?

8. 2001-April-10 Flare Flare April 10, 2001 05:10 UT GOES X2.3 NOAA 9415
East
West
Ha images taken with Sartorius Telescope

9. Observations Data Ha･･Sartorius Telescope,
Kyoto University (Ha center)
EUV・・TRACE (171A)
HXR・・Yohkoh/HXT
microwave・・
Nobeyama Radioheliograph
magnetogram・・SOHO/MDI
Sartorius Telescope (Kwasan Obs.)

10. 1. Conjugacy of Ha Footpoints
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
simultaneously brighten

11. Conjugacy of Ha footpoints
divided flare ribbons into fine meshes
determine “conjugated footpoints” by using cross-correlation function
red:positive, blue:negative

12. The TRACE loops really connect the pairs.
TRACE Flare Loops
TRACE 171A
The TRACE loops really connect the pairs.
East
West

13. Temporal evolution of Ha kernels
The pairs are classified according to the times of brightening

14. Focus on Each Pair
Movement of the site of energy release t

15. 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
Reconnection model indicates
Bc : coronal magnetic field strength
vin : inflow velocity
A : area of the reconnection region

16. Energy Release Rate Electric Field  conservation of
Bc : coronal magnetic field strength
Bp : photospheric magnetic field strength
vin : inflow velocity
vf : separation speed of flare ribbons
 conservation of
magnetic flux
It is very difficult to estimate physical values (Bc, vin) in the corona
Poynting Flux
I estimate the energy release rate, by using observable values (Bp, vf)

17. Evolution of Flare Ribbons
Neutral Line B v
I estimate the reconnection rate vB, and the Poynting flux vB2 as the representations of the energy release rates.

18. Evolution of Flare Ribbons
Neutral Line B v
I estimate the reconnection rate vB, and the Poynting flux vB2 as the representations of the energy release rates.

19. Evolution of Flare Ribbons
Neutral Line B v
I estimate the reconnection rate vB, and the Poynting flux vB2 as the representations of the energy release rates.

20. Energy Release Rate Energy Release Rate
HXR sources
flare ribbons
Ha image
Energy Release Rate
We compare the derived energy release rate with HXR light curves

21. Reconnection Rate and Poynting Flux
microwave
HXR
An HXR burst occurred on
the slit (05:19 UT).
reconnection rate
Poynting flux

22. Reconnection Rate and Poynting Flux
microwave
HXR
reconnection rate
An HXR burst occurred on
the slit (05:26 UT).
Poynting flux

23. Quantitative EstimationW1
Comparison of Poynting and Electric Field (Reconnection Rate) between the Ha kernels with HXR sources and those without ones E2 W2 E2 W2 E1 W3 E3 E4 W4

24. 3. Ha kernel spectroscopy
Ichimoto & Kurokawa 1984
Ha spectrum
flare
Ha line is shifted red-ward
red-asymmetry
velocity : km/s
X-ray
corona Ha
compression
chromosphere l
Ha line

25. Red-Asymmetry Map we calculated as an indicator of r.a.
all over the flare ribbon, the tendency of r.a. is seen
map

26. Red-Asymmetry Distribution
strong edges of the flare ribbon
1000~3000 km (?)
at HXR sources, r.a. is not necessary strong

27. Scatter plot (intensity vs RA)
Iblue-Ired vs r.a. scatter plot
the brighter the kernel is, the stronger the r.a. is
intensity of Ha kernel
red
blue

28. Summary We can learn from Ha 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 Ha wing data

30. 2D / 3D
observed as Ha flare ribbons

31. Temporal evolution of Red-Asymmetry
red-asymmetry peak precedes the HXR/microwave peaks (HXR bursts are not necessary associated with strong red-asymmetry)

32. 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
bright
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?
dark
bright in red
bright in blue

33. Haカーネルのライトカーブ
場所によってさまざまなライトカーブを示す

34. 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

35. Ha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 Haカーネルの増光 Haフレアリボンの形成
エネルギー解放したループの足元の場所が分かる
Haフレアリボンとして観測

36. Ha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Haカーネルを生成
非熱的・高エネルギー粒子の彩層突入
硬X線
Ha線
コロナ
　彩層
制動放射
急激な熱化など