CORONAL HEATING AND THE VERTICAL TEMPERATURE STRUCTURE OF THE QUIET CORONA

The radial variation of temperature in the inner corona is examined us ing long-exposure Yohkoh images of two regions of diffuse (quiet) coro na. The results indicate a steady radial increase of temperature for b oth regions, out to 0.7 and 0.95 solar radii above the limb. We find t hat the filter-ratio data for the two regions is well fitted in each c ase by integration over the line of sight of a spherically symmetric m odel atmosphere in hydrostatic equilibrium and with a temperature prof ile due to a conserved inward heat flux. An Abel inversion process is also applied to the data, and this gives results consistent with the s pherically symmetric, conserved-heat flux model. These results imply t hat the nonthermal energy responsible for heating these regions of the quiet corona is being deposited beyond the observed range of heights. However, the diffuse regions we examined are believed to be partly cl osed-field regions, and so, the radial models require careful interpre tation. We discuss the implications for coronal heating in these regio ns.