The Diagnostic Temperature Discrepancy as Evidence for Non-Maxwellian Coronal Electrons

Two independent temperature diagnostics applied to the quiet solar corona yield systematically different results: radio brightness and Doppler line widths indicate Tkin ≈0.6 MK, while ionization equilibrium and hydrostatic scale heights indicate Tion ≈1.5 MK. This factor of 2.4 ±0.3 discrepancy is typically attributed to calibration issues or multithermal effects. We propose instead that both measurements are correct: they probe different regions of a non-Maxwellian velocity distribution. As shown by S. P. Owocki & J. D. Scudder (1983), ionization rates in non-Maxwellian plasmas are dominated by the suprathermal tail, so that standard Maxwellian fitting systematically overestimates the core temperature. In a kappa distribution, the predicted ratio scales approximately as κ/(κ− 3/2). The observed ratio implies κ≈2–3, consistent with the independently measured spectroscopic range (κ ≈ 2–5) for the quiet Sun. This framework applies where the Knudsen number exceeds ∼0.01—particularly in the lower corona where temperature gradients are steep. We predict that the diagnostic ratio should collapse toward unity in high-density structures where collisions restore thermal equilibrium. If confirmed, standard fluid models may overestimate conductive losses by applying Spitzer-H¨arm diffusion to inherently non-Maxwellian plasma.