Bi-directional flows in a C-class solar flare

We have explored the bi-directional flows in a C-class solar flare observed by Solar Dynamic Observatory Atmospheric Imaging Assembly (SDO/AIA) on 2012 December 26. This event occurs in a curved magnetic loop connecting a pair of negative and positive fields. The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) observations show a X-ray source in 3-25 keV stayed at the loop top during the flare. High-cadence AIA observations exhibit many flows movement intermittently along the flare loop. In order to analyze these flows, firstly, the event is cut along the loop direction with a curved slit which is wide enough to include the bulk of ultraviolet (UV) and X-ray emissions. Secondly, after integration the flux along the slit width, we get the space-time slices at 9 AIA wavelengths and in RHESSI 3-25 keV. Thirdly, the derivative is done on the space-time slices. Many bi-directional flows are identified as the oblique streaks on the intensity-gradient space-time slices during the flare lifetime. They almost start from the same position near the loop top, where the X-ray emission is bright in 3-25 keV. Then they move toward the positive and the negative polarity footpoints simultaneously. Their average speed is directly measured about 230 km s(-1), and they exhibit a typical quasi-period of about 3 minutes. The characteristics of these flows, such as bi-directional, simultaneous, symmetrical and quasi-periodic, are the observational constraints for acceleration theories.