Oxygen Observations by STEREO/PLASTIC in the Slow Solar Wind

We have analyzed solar wind oxygen in the data from the STEREO Plasma and Supra-thermal Ion Composition Experiment (PLASTIC). For this initial study we concentrate on the slow solar wind where the ion composition is stable, different ion species have nearly the same bulk speed, and the kinetic temperature is usually low. The mass of the detected ions is determined when the ions have both a valid time-of-flight and a residual energy measured by a Solid State Detector (SSD). The bulk speed, thermal speed and flow angles of O6+ are then calculated using the electrostatic analyzer and position data. The STEREO data are compared to similar measurement on ACE/SWICS.