Movement of an Arch-like Eruptive Prominence

The motions of ascending, descending and expanding in radius of an arch-like eruptive prominence are analyzed in this paper. The variations of the height of the prominence versus time were relative fast during the stages of its ascending and the beginning of the descending, and were linear basically. But the height variation was slow and linear basically during the end stage of its descending. The prominence did not free fall down under the action of gravity, it falled down under an united actions of not only the gravity but also inhomogeneous atmospheric resistance and magnetic force. The ejection velocity of the prominence weaken gradually, it weaken rapidly during its ascending. However, during the descending there was a leap-like change: the velocity decreased rapidly at first, then increased fast, during the late stage of descending it decreased slowly. The time when the prominence ascended to its maximum height was earlier about 4 minutes than that time while the radius of prominence expanded to the maximum. The expanding velocity of its radius reached the minimum when the ascending or descending velocity was in the maximum and vice versa.