INFLUENCE OF HEAVY-IONS ON THE HIGH-SPEED SOLAR-WIND

We present the results of a parameter study of the influence of heavy ions on the background solar wind, choosing doubly ionized helium, or alpha particles, and O+6 examples. Using a three-fluid solar wind mode l, we keep the input parameters to the electrons and protons unchanged and investigate the effects of changing the input energy flux to the heavy ions and their coronal abundance, i.e., their abundance at 1 R-s , on the background electron-proton solar wind. Our results confirm ea rlier studies that alpha particles can have a dramatic effect on the t hermodynamic and flow properties of the protons in the solar wind. The maximum coronal abundance for which the changes in the energy input t o the heavy ions has no effect on the protons is 5 x 10(-4) for the al phas and 5 x : 10(-5) for the oxygen ions, which are well below the ph otospheric values. For larger coronal abundances, the sensitivity of t he changes of the flow speed and proton mass flux to changes in the en ergy input to the heavy ions increases sharply with increasing abundan ce. When the heavy ions are not heated, the increase in the coronal ab undance leads to an increase in flow speed, a decrease in proton mass flux, and an increase in proton temperature at 1 AU. However, as the h eat input to the heavy ions increases, the dependence of these paramet ers on the abundance goes through a transition and starts to follow th e opposite pattern, namely a decrease in flow speed and proton tempera ture at 1 AU, and an increase in proton mass flux. This study shows th at, for currently known photospheric elemental abundances, the flow pr operties of heavy ions cannot be investigated independently of those o f the bulk proton-electron solar wind. The effect of heavy ions on the electron-proton bulk solar wind is determined primarily by the collis ions occurring very close to the coronal base. Hence including physica l processes responsible for the preferential heating of heavy ions to temperatures exceeding those of protons in the inner corona cannot be done without considering the subsequent implications for the protons a nd electrons in a self-consistent manner.