Velocity Field and Loss of Mass in Solar Macrospicules from High Time Resolution Observations in the He ii 304 Å Spectral Line

We use high-cadence observations in the He ii 304 Å line and a simple one-dimensional hydrodynamic model to reconstruct the evolution of the velocity field of 18 macrospicules. Besides, we study motions of their apparent summits and find them to follow parabolic trajectories, which correspond closely to the obtained velocity field. The trajectory decelerations typically range from 140 to 240 m/s2, and initial velocities from 80 to 145 km/s. Moreover, we find a clear linear dependence between these two values. We estimate that typically from 10 to 30% of the macrospicule's observed mass fade out of the spectral line.