A Study of Flare-associated X-Ray Plasma Ejections. III. Kinematic Properties

In this study, we have investigated the kinematic properties of flare-associated X-ray plasma ejections. First, we obtained the speed profiles of well-observed several events and compared them with the GOES soft X-ray flux profiles as well as the HXT hard X-ray flux profiles of their associated flares. Second, we have estimated the Alfvén speed at the observing height of X-ray plasma ejections in order to find whether the X-ray plasma ejection is a reconnection outflow as predicted by standard magnetic reconnection model. Finally, we have estimated the representative speeds of all 137 X-ray plasma ejections and then compared them with the speeds of the coronal mass ejections (CMEs). Our main results are as follows: (1) X-ray plasma ejections usually initially accelerate and then constantly propagate or slowly decelerate; (2) for several well-observed examples, the speed profiles of X-ray plasma ejections are similar to those of the hard X-ray emission profiles; (3) the speed of an X-ray plasma ejection ranges from 30 to 1300 km s^-1, with a mean speed of 230 km s^-1, and the speed of a CME ranges from 150 to 2000 km s^-1 with a mean value of 530 km s ^-1; (4) there is no statistical correlation between the speeds of X-ray plasma ejections and the corresponding CME speeds; (5) an X-ray plasma ejection seems to have a much shorter acceleration duration (less than 10 minutes) than that of a CME (larger than 30 minutes). On the basis of these results, we suggest that the majority of X-ray plasma ejections are not likely to be the X-ray counterpart of CMEs but outflows generated by magnetic reconnection, at least from the kinematical point of view.