HR: 0830h
AN: SP51B-07    [Abstracts]
TI: Solar Cycle Variations of Coronal Hole Properties
AU: * Miralles, M P
EM: mmiralles@cfa.harvard.edu
AF: Harvard-Smithsonian Center for Astrophysics, 60 Garden St., MS-50, Cambridge, MA 02138 United States
AU: Cranmer, S R
EM: scranmer@cfa.harvard.edu
AF: Harvard-Smithsonian Center for Astrophysics, 60 Garden St., MS-50, Cambridge, MA 02138 United States
AU: Kohl, J L
EM: jkohl@cfa.harvard.edu
AF: Harvard-Smithsonian Center for Astrophysics, 60 Garden St., MS-50, Cambridge, MA 02138 United States
AB: As of early 2005, we have measured with the SOHO Ultraviolet Coronagraph Spectrometer (UVCS) the physical properties of at least 136 large coronal holes that produced a variety of high-speed solar wind conditions at 1 AU. UVCS has been used to observe O VI (103.2 and 103.7 nm) and H I Lyman alpha (121.6 nm) emission lines as a function of heliocentric distance in coronal holes since 1996. The analysis of their spectroscopic parameters allows us to identify similarities and differences among coronal holes at different phases of the solar cycle. From such measurements we can derive plasma parameters (densities, temperatures, velocity distribution anisotropies, and outflow speeds) for O⁵⁺ and protons as a function of heliocentric distance in the coronal holes. These properties, combined with other observed quantities such as white-light polarization brightness and the more-or-less unipolar magnetic fluxes measured on-disk, let us map out the "allowed parameter space" of coronal hole plasma properties more fully than ever before. We will present the solar cycle dependence of the above plasma parameters from the last solar minimum in 1996 to present and compare them, where possible, with the in situ solar wind properties. We will also present an update on the pattern that is beginning to emerge, i.e., coronal holes with lower densities at a given heliocentric distance tend to exhibit faster ion outflow and higher ion temperatures. This information will thus be used to set firm empirical constraints on coronal heating and solar wind acceleration in coronal holes. In 2005, the polar coronal holes have not yet evolved to the fully quiescent minimum state seen in 1996-1997, though the next solar minimum is expected to occur in about 1.5 to 2 years. This work is supported by NASA under Grant NNG04GE84G to the Smithsonian Astrophysical Observatory, by the Italian Space Agency, and by PRODEX (Swiss contribution).
DE: 2164 Solar wind plasma
DE: 2169 Sources of the solar wind
DE: 7511 Coronal holes
DE: 7536 Solar activity cycle (2162)
DE: 7549 Ultraviolet emissions
SC: Solar Physics Division - AAS [SP]
MN: 2005 Joint Assembly