A Spectroscopic Observation of a Magnetic Reconnection Site in a Small Flaring Event

Abstract

We have observed two types of coronal bidirectional flows in a flare with a small energy release through a spectroscopic observation of the Fe X emission line at 6374 Å with a ground-based coronagraph at the Norikura Solar Observatory. We find a bidirectional flow of ±3 km s-1 above the top of a flare loop. Remarkable increases of the line intensity and line width are not observed in the flow. From the loop geometry and sign of the Fe X Doppler velocity we conclude that the bidirectional flow is reconnection inflow above the flare loop. We estimate the reconnection rate to be ~0.003 for this event. The other bidirectional flow is observed along postflare loops with significant increases of the line intensity and Doppler velocity. This flow is interpreted as a cooling upflow having a velocity of ~10 km s-1 along a postflare loop from its lower part. We also find that the increase of the nonthermal line width in the loop-top region starts when the line intensity reaches its peak. This supports the presence of a mechanism to enhance turbulent plasma motions in the loop-top region.