  Quiescent streamers are characterized by a peculiar UV signature as pointed
out by the results from the observations of the Ultraviolet and Coronograph
Spectrometer (UVCS) on board SOHO: the intensity of heavy ion emission lines
(such as OVI) show dimmer core relative to the edges. Previous models show that
the structure of the heavy ion streamer emission relates to the acceleration
regions of the slow solar wind at streamer legs and to gravitational settling
processes in the streamer core. Observations of Mg9+ ion EUV emission in
coronal streamers at solar minimum were first reported by the UVCS instrument.
The Mg X 625A emission is an order of magnitude smaller than the OVI 1032A
emission, requiring longer exposures to obtain statistically significant
results. Here, MgX coronal observations are analyzed and compared, for the
first time, with the solar minimum streamer structure in hydrogen and OVI
emissions. We employ the 2.5D three-fluid model, developed previously to study
the properties of O5+ ions in streamers, and calculate for the first time the
density, temperature, and outflow structure of Mg9+ ions in the solar minimum
streamer. The Mg9+ ions are heated by an empirical radial heating function
constrained by observations of the kinetic ion temperature obtained from MgX
emission line profiles. The detailed structure of Mg9+ density, temperature,
and outflow speed determined by the Coulomb momentum and energy exchange as
well as electromagnetic interactions with electrons and protons in the
three-fluid model of the streamer. The results of the model are in good
qualitative agreement with observations, and provide insights on the possible
link between the magnetic structure of the streamer, slow solar wind sources,
and relative abundances of heavy ions.
