Dynamic Properties of Solar Spicules Observed by Sumer/soho

We present a study the dynamic properties of EUV spicules. The selected data were obtained as time series in polar coronal holes by SUMER/SOHO. The short exposure time and the almost fixed position allow the analysis of the spicule properties such as: occurrence, lifetime, Doppler velocity, etc. Our data reveal that spicules occur repeatedly at the same location with a birth rate of around 0.1/min and a lifetime ranging from 15 minutes down to a few minutes. Most of them have a height between 10 and 20 above the limb, and some can reach a height of 20 to 40 as macrospicules. We are able to see some spicules showing a process of “falling after rising” indicated by the change of Doppler velocity signs. In addition, on the disk, the same data indicate that EUV spicules have a behaviour as brightenings, with increase of radiance and change of Doppler velocity if seen in time series radiance maps and Dopplergrams.