Direct Observations of the Magnetic Reconnection Site of an Eruption on 2003 November 18

1. Direct Observations of the Magnetic Reconnection Site of an Eruption on 2003 November 18 2005,ApJ, 622,1251 J. Lin, Y.-K. Ko, L. Sui, J. C. Raymond, G. A. Stenborg, Y. Jiang, S. Zhao, and S. Mancuso 2005/11/28 太陽雑誌会 <short>　長島薫 Solar Seminar (Zasshikai) NAGASHIMA Kaori

2. <1.Introduction> Since the timescale of magnetic dissipation or reconnection is longer than that of the catastrophe (i.e., the Alfven timescale ), the development of a long current sheet is expected during major eruptions. In this study, a direct observation of the current sheet and the associated reconnection process is reported. reconnection inflow current sheet & reconnection outflow part of Fig.1 Schematic diagram of a disrupted magnetic field forming in an eruptive process.

3. <2.Observations & Results>Observations an eruptive event • occurred on 2003 Nov. 18 • on the east limb (between NOAA AR 0507 & 0508) DATA: • SOHO/EIT 195Å & RHESSI • observation of the initial stage & subsequent development of the eruption in the lower corona • SOHO/UVCS, LASCO & MLSO MK4 • observation of the consequences in the higher corona

4. EIT 195Åmovies current sheet (fig2) flare loop (fig2)non-movie

5. composite of LASCO C2 (17:50) , MK4(17:49) ,& EIT 195Å (17:48) images This figure resembles the typical Kopp-Pneuman configuration for major flares (Kopp & Pneuman 1976), in which the post-flare/CME loops are located under the cusp structure at the lower tip of the current sheet. Fig. 8

6. after the wavelet-based intensity contrast enhancement (WICE) before the WICE WICE → good at emphasizing the fine features of large-scale structure.（Stenborg & Cobelli 2003 A&A）

7. LASCO C2 movie • enhanced by the wavelet (WICE) technique • Fine structures • leading edge & core of CME • current sheet • the helical structure around the CME core fig4 (~12hr)

8. <2. Observations & Results>Inflow Velocity & Reconnection rate • Following Yokoyama et al.(2001), the inflow velocity can be measured using the motion of two legs of the arcade system observed by EIT. • However, the structure seen in the EIT images is diffuse and the apparent inward motion was suggested that actually due to the changing position of the X-type reconnection region rather than inflow. (Chen et al. 2004) • Therefore, in this study, they use the UVCS observations to determine the inflow speed. Yokoyama et al. 2001 part of Fig.4

9. Fig.5 EIT 195Å (10:14) UVCS Lyα(slit scan) LASCO C2 (10:26) using WICE The width of a dark gap seen in the left UVCS image decreased with time. magnetic reconnection inflow time *dark gap ⇔ current sheet

10. <2. Observations & Results>Inflow Velocity & Reconnection rate • The dark gap (not a no emission region but a lower Lyα intensity region) could result from a higher temperature or a significant outflow speed. • The Lyα width in the gap is considerably larger than in the outside of it. This suggests higher temperature in the gap. However, this temperature (6.7e6 K) require a density above 1e8 /cm^3 to account for the Lyα intensity. This is inconsistent with no FeXVIII signal. • Smaller density also can be a cause of darkening, but the modest density enhancement was observed in the LASCO images. • Then, the low emission is due to Doppler dimming. • An outflow speed of 200 km/s would account for the low intensity in the gap. (large line width⇔LOS comp. of outflow.)

11. <2. Observations & Results>Inflow Velocity & Reconnection rate Inflow velocity can be deduced by comparing the widths of the gap every two successive times. inflow velocity VR : 10.5-106 km/s north time the center of gap ~ P.A. =95° south Lyα intensity Position Angle [deg.] Fig.11a 5 Lyαintensity profiles along the UVCS slit taken at 1.70Rsun 10:04-10:14 UT.

12. an evidence for the reconnection inflow LOS ⊥inflow north : blueshift (~20km/s) No Doppler shift south : redshift (~35km/s) inflow inflow When the field lines adjoining the CS are tilted ... the center of the gap Wavelength [A] Fig. 12 averaged over 10:04-10:14

13. <2. Observations & Results>Inflow Velocity & Reconnection rate • Outflow velocity : 460-1075 km/s • Several bright blobs successively flowed away from the Sun along a long thin streamer-like feature observed by LASCO C2 & C3. • the thin feature ⇔current sheet (CS) • the blobs ⇔ outflow of reconnection inside the CS • Assuming an incompressible plasma, the outflow velocity is equal toVA(the local Alfven speed in the reconnection region). • Therefore, the reconnection rate MA=VR/VA is in the range from 0.01 to 0.23. (However the real value of MA should vary over a wider range.)

14. Summary • an erupitive process • direct observation of CS, inflow, and outflow • an energetic CME • the CME & the flare are connected by a stretched current sheet. • the average reconnection inflow :10.5-106km/s (using the UVCS Lyα data ) • Lyα profiles around the gap are shifted. • a direct evidence of the reconnection inflow? • the average outflow : 460-1075km/s (blob) • the reconnection rate :0.01-0.23