Solar wind ion trends and signatures: STEREO PLASTIC observations approaching solar minimum

摘要

STEREO has now completed the first two years of its mission, moving fromclose proximity to Earth in 2006/2007 to more than 50 degrees longitudinalseparation from Earth in 2009. During this time, several large-scalestructures have been observed in situ. Given the prevailing solar minimumconditions, these structures have been predominantly coronal hole-associatedsolar wind, slow solar wind, their interfaces, and the occasional transientevent. In this paper, we extend earlier solar wind composition studies intothe current solar minimum using high-resolution (1-h) sampling times forthe charge state analysis. We examine 2-year trends for iron charge statesand solar wind proton speeds, and present a case study of CarringtonRotation 2064 (December 2007) which includes minor ion (He, Fe, O) kineticand Fe composition parameters in comparison with proton and magnetic fieldsignatures at large-scale structures observed during this interval.