Cranmer, S. R., 2003, ``Heating of the Extended Solar Corona,'' IUGG XXIII General Assembly, Symposium GAIV.02: Coupling Complexity in the Heliosphere, Sapporo, Japan, July 2003 (Invited Talk). [Talk viewgraphs, in Adobe PDF format, are available.]
The acceleration region of the solar wind has been revealed in the past decade to be a highly dynamic nonequilibrium plasma environment. For example, the UVCS instrument on SOHO has revealed strong kinetic anisotropies and extremely large ion perpendicular temperatures in the acceleration regions of coronal holes. Despite the many new observational constraints, though, the basic physical processes responsible for heating the million-degree solar corona and accelerating the solar wind are not known. Obtaining a fundamental understanding of the physics of the extended corona is especially challenging for several reasons. First, the plasma in the wind's acceleration region (1 to 10 solar radii) is neither fully collisional nor fully collisionless. Second, many of the proposed physical processes, such as turbulent cascade and wave-particle resonances, act on a multiplicity of spatial scales (from centimeters to solar radii) with feedback effects not yet well understood. Third, it is not yet clear to what extent the numerically minor heavy ions affect and reflect the physics of the bulk proton-electron plasma. This presentation reviews the above issues in the context of building unified models of coronal particle kinetics and fluctuation spectra that include as many of the proposed mechanisms as possible. Because many of the physical processes interact with one another on a multitude of spatial and temporal scales, their true impact on the system may not be made clear until they are studied simultaneously (producing an emergent richness that would not have occurred if each process was studied in isolation). A discussion of remote-sensing observations that still need to be made will also be presented.
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