On-disk Observation of Bidirectionally Propagating Plasma Blobs Near the Reconnection Site of a Solar Eruption

Current sheet is a commonly observed structure involved in solar eruptions. However, the physical properties of its fine structures during a solar eruption are rarely investigated. Here, we report an on-disk observation that displays 139 compact, circular or elliptic bright structures, presumably plasma blobs, propagating bidirectionally along a plasma sheet during a period of about 24 minutes around the peak time of an eruptive flare. From extreme ultraviolet images, we distinguish a plasma sheet connecting the flare loops and the erupting filament. The average width, duration, and projected velocities of these blobs are about 1.7±0.5 Mm, 73±54 s, and 190±81 km/s, respectively. The reconnection site rises with an average velocity of about 51 km/s. We have obtained the temporal variation of the blob number during the solar eruption, which is similar to that of the GOES X-ray flux. The observational results suggest that plasmoid instability plays an important role in the energy release process of solar eruptions.