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Energy and momentum deposition in coronal holes
Solar coronal hole simulations compared with interpretations of Yohkoh SXT observations
K. Tziotziou 1,
P.C.H. Martens 2 and
A.G. Hearn 1
Received 5 January 1998 / Accepted 27 July 1998
A grid of 74 coronal models with parameterized heating distribution, representing a wide range of physical parameters, has been calculated. We find that three of these models reproduce the recent observations made by Hara et al. (1994) with the soft X-ray telescope aboard the Japanese satellite Yohkoh , which indicate a temperature of with an emission measure of to , while other solutions reproduce the more standard Yohkoh and Skylab observations, which have a temperature of about
The best fit for the coronal temperature and emission measure gives a velocity at the Earth's orbit of only . A model including acceleration by Alfvén waves gives a final velocity of which is in agreement with the observations. The mechanical heating flux at the transition region is with a weighted average dissipation scale length of . The flux of Alfvén waves is .
In our models the velocity of the solar wind from coronal holes is completely determined by the Alfvén wave acceleration, in contrast to previous models in which the Alfvén wave acceleration increased the velocity of the purely thermal model only by a factor 2.
Observations of the non thermal broadening of the coronal red and green lines are consistent with this model.
Key words: hydrodynamics methods: numerical stars: coronae stars: mass loss
Send offprint requests to: A.G. Hearn
Online publication: November 3, 1998