Observational Study on the Velocity Field of an Eruptive Prominence

The Hα spectral data observed on March 5,1991 were obtained at Yunnan Observatory for a spray-like eruptive prominence, the "Multi-Cloud Model" method is applied to derive the 2D velocity field of the prominence. By analyzing the velocity field, an ejection velocity and angular velocity as well as their distributions versus the height are obtained.The results show that the blue-shift velocity of the prominence predominates absolutely, the range of the velocity is from 8 to 110 km/s.The velocity distribution is inhomogeneous and asymmetric: the values of the velocity are bigger in the middle and the base parts than those in the top part of the prominence; velocity gradient near the southern limb is larger than that near the northern one. Ejection movements present not only the ascending movement, but also the line-of-sight velocity V₀ towards the observer with an average value of 50 km/s, a rotational angular velocity ω is also detected with an average value being 7×10^-4 rad·s^-1,the height variations of V₀ and ω seem opposite with each other.