Temporal Evolution of the Magnetic Network in Polar Coronal Holes

We present an analysis of time series data acquired with the SUMER spectrograph on SoHO in coronal hole regions, being particularly interested to find the fast solar wind origins as low as possible in the solar atmosphere. We study the temporal evolution of the magnetic network as seen in different layers in the transition region (TR). Our results indicate that, in lines originating from low to medium TR temperatures, we find variations of intensity with periods of ≈ 20 min or longer which are made up of short time brightenings that repeat every ≈ 5 min. In these observations, we have not observe the fast solar wind starting as a steady outflow in the TR. Instead, we see bursts of short time brightenings, some of which represent bi-directional jets of different scales that, because of the open field structure they meet in coronal holes, we suggest they could pump plasma into the corona.