High minor ion outflow speeds in the inner corona and observed ion charge states in interplanetary space

Abstract

Flow speeds recently derived from, chromospheric, transition region and coronal observations indicate that the solar wind acceleration process takes place at heights in the solar atmosphere much lower than previously imagined (Dupree et al. 1996). Doppler dimming observations of the O VI 1032/1037 Å spectral lines show that this is not only true for the background electron-proton solar wind but also for minor ions (Kohl et al. 1997). The limits that these observations place on the flow speed of the O+5 ions are at least a factor of 3 to 4 higher than expected from earlier minor ion studies (e.g. Bürgi & Geiss 1986; Ko et al. 1997). Using the newest available atomic data together with the most recent observational constraints on electron temperatures, electron densities and flow speeds, we show that high minor ion outflow speeds of the order of the O+5 outflow speed (about 130 to 230 km s-1 below 3 RS) are consistent with charge state observations. We then discuss how minor ion charge state observations can be used in future observational and theoretical studies to place limits on solar wind acceleration and heating mechanisms.