Observation of a type of sporadic solar mass ejection and its physical interpretation with numerical simulation

Seven mediate and small ejective events on the sun observed at Ganyu Observing Station of Purple Mountain Observatory in 2000 are investigated. It is found that they were not accompanied by brightening. Their lengths were in the range 1-2.5 x 10(4) km, their widths, 3-5 x 10(3) km, and their lifetimes, 3-7 minutes. They were produced at places of weak magnetic fields and far away from large sunspots. These ejections are interpreted by numerical simulation with 1-D hydrodynamic equations of flow along magnetic arcs. As demonstrated by the results, they are different from the spicules and surges simulated by Suematsu et al. and Shibata et al. They are not matter with photospheric or chromospheric densities pushed by shock waves or rebound shock waves toward the solar corona, rather, they are ejections formed by continuous matter flows after magnetic reconnection. After evolving for about 5 minutes, they can attain a stationary hydrodynamic state.