Energy and momentum deposition in coronal holes - Solar coronal hole simulations compared with interpretations of Yohkoh SXT observations

A grid of 74 coronal models with parameterized heating distribution, repres enting a wide range of physical parameters, has been calculated. We find th at three of these models reproduce the recent observations made by Hara et al. (1994) with the soft X-ray telescope aboard the Japanese satellite Yohk oh, which indicate a temperature of 1.8 similar to 2.4 x 10(6) K with an em ission measure of 10(25.5) to 10(26.2) cm(-5), while other solutions reprod uce the more standard Yohkoh and Skylab observations, which have a temperat ure of about 1.4 x 10(6) K. The best fit for the coronal temperature and emission measure gives a veloc ity at the Earth's orbit of only 10 km s(-1). A model including acceleratio n by Alfven waves gives a final velocity of 630 km s(-1) which is in agreem ent with the observations. The mechanical heating flux at the transition re gion is 2.1 x 10(5) erg cm(-2) s(-1) with a weighted average dissipation sc ale length of 0.1 R.. The flux of Alfven waves is 2.1 x 10(5) erg cm(-2) s( -1). In our models the velocity of the solar wind from coronal holes is complete ly determined by the Alfven wave acceleration, in contrast to previous mode ls in which the Alfven wave acceleration increased the velocity of the pure ly thermal model only by a factor 2. Observations of the non thermal broadening of the coronal red and green lin es are consistent with this model.