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R.T. Scopes, J.T. Schmelz (University of Memphis), J.-P. Wuelser (Lockheed Martin)
Despite recent progress in understanding the solar corona, there are still important parameters and processes that remain elusive. Chief among them is the coronal heating problem, the precise physical mechanism(s) by which the solar atmosphere is heated to its million-degree (or greater) temperatures. It is not yet known how this energy is stored, released, and dissipated.
Theoretical arguments classify coronal heating mechanisms as either dissipation of MHD waves or dissipation of field-aligned electric currents. When reasonable estimates of the current density and wave amplitudes are combined with the classical coefficients of resistively and viscosity, the derived heating rates are too low to balance the energy losses through radiation and conduction. Fortunately, there is a rich database of theoretical models described in the literature that attempts to explain how the dissipation rates are enhanced over the classical estimates.
Since many of these theoretical models can produce enough energy to balance the observed losses from both radiation and conduction, the coronal heating problem is then to determine which of these possible models, if any, is correct. We are involved in a joint analysis of plasma parameter measurements obtained from high-resolution EUV spectral line data from the SOHO Coronal Diagnostics Spectrometer, and imaging data gathered simultaneously with the Yohkoh Soft X-ray Telescope. These data were used to determine the multi-thermal distribution at each pixel along a set of quasi-stable coronal loops using the forward-folding technique. Specifically, our focus has been comparison of measurements taken form coronal loop footpoints with those of their respective peaks. We are currently comparing our observational results with the temperature profiles predicted by various coronal heating mechanisms to determine which of these mechanisms, if any, is responsible for the loop heating (Priest et al. 1998, Nature, 393, 545). This research is supported through NASA grant NASG5-7197.
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