## 1. IntroductionRecent UVCS/SOHO data (Kohl et al. 1997, Cranmer et al. 1997) show,
for the heavy ions exemplified by , very high
temperatures reaching K in the inner corona with
large temperature anisotropy ( In the present paper we extend the one-ion treatment of McKenzie et
al. (1997) by considering two ion components, the minor component
being either the or (in
the latter case the main component is taken to be the
() mixture). In parallel to the early work (Yeh
1970, Weber 1973) our treatment exploits the critical structure of the
phase space of the stationary bi-ion flow equations using the
generalized concept of sonic points in a bi-ion flow including
differential streaming (McKenzie et al. 1993). In order to avoid
solving the coupled energy and momentum equations we use the proton
temperature profiles of McKenzie et al. (1997) and assume the minor
component is preferentially heated proportional to its mass (with an
extra factor of The published work on the multi-ion solar wind acceleration problem, apart from early isothermal models (Yeh 1970, Weber 1973) or the calculations assuming simple temperature profiles (Leer, Holzer & Shoub 1992), include also, starting from Burgi (1992), the more complete calculations in which the energy transport equations are solved simultaneously with the flow equations, with some assumptions made for the source terms. However, none of those cover the case that we consider, namely the anisotropic temperature profiles and a complete expression for the wave force. The extensive study of Hansteen et al. (1997), while encompassing also the chromosphere, is restricted to the case of isotropic temperatures. Isenberg (1984) included both the wave force and anisotropic temperatures as well as a specific model of the resonant interaction, but his calculations were limited to the region outside 10 , beyond the solar wind critical points. We do not intend to review here the whole field of solar wind acceleration theories but we want to draw attention to interesting recent work by Hu et al. (1997) and Tu and Marsch (1997). © European Southern Observatory (ESO) 1998 Online publication: June 12, 1998 |