On the extended chromosphere of Alpha Orionis

The authors develop preliminary models for the extended chromosphere of α Orionis. A flux of Alfvén waves sufficient to drive an outflow of ≡10-6M_sun;yr-1 is assumed. The momentum and energy equations for the wave-driven wind are solved assuming steady, radial, spherically symmetric flow. The mechanical energy fluxes needed to heat the extended chromosphere are of sufficient magnitude that momentum deposition by waves can support an extended chromosphere. The model accounts reasonably well for the observed radio continuum emission, the observed surface brightness distributions, and the emission fluxes in a variety of spectral lines. The detailed kinematics of the solution is less satisfactory in reproducing observed line profiles. It is suggested that the observed, nearly symmetric line profiles can be understood best in terms of a "fountain" model, in which most of the ejected material falls back rather than escaping.