1. Superhot DEM (or DF?) RHESSI continuum with TRACE or EIT FeXXIV, SUMER FeXXI, GOES, or whatever

2. Motivation The physics of the transfer of magnetic energy to the plasma in a flare is largely unknown The plasma distribution function should become non-Maxwellian during intense energy release, and if we can diagnose it we may learn about this physical problem The DF, not the DEM, is the more fundamental description

3. Warren and Reeves, ApJ 554:L103, 2001 0.1 1.010 keV

5. Gallagher et al., Solar Phys. 2002

6. Problems - I We wish to use the observations to constrain the electron distribution function (DF) RHESSI samples this distribution at roughly h + kT> kT for bremsstrahlung continuum Multi-wavelength comparisons are essential for defining the DF at low energies (DEM at low temperatures)

7. Problems-II X-ray and EUV emission lines (specifically FeXXIV 192A and FeXXI 1354A) sample the distribution function differently. 1354A line is a 2s2 2p2 3P0 - 2s2 2p2 3P1 transition, but…what does that mean in terms of sampling the electron distribution function? We need cross-sections, not contribution functions.

8. Problems-III Emission lines are good, because they have have contribution functions with sharp spectral features - good kernels for inverse calculations But they are bad, because they must be interpreted in terms of a theoretical ionization equilibrium calculation (and abundances…)

9. Conclusions There is strong motivation to combine RHESSI imaging spectroscopy with TRACE images at 192A It is a hard problem and we probably need some help from atomic physicists We have an excellent event - April 21, 2002 - to work with - and probably many others