David C. Nicholls led a 2012 investigation of discrepant nebular temperature measurements. The paper, with Michael A. Dopita and Ralph S. Sutherland, explores a Kappa distribution for electron energies instead of imposing a Maxwell-Boltzmann distribution.
Different spectral diagnostics weight electron energies differently. Consequently, a departure from the assumed distribution can change inferred temperatures and abundances in different ways. The study presents the nonthermal distribution as a physical explanation to test, rather than treating agreement obtained under a changed assumption as a direct measurement of the distribution itself.[ref]
Resolving the electron temperature discrepancies in H II regions and planetary nebulae: kappa-distributed electrons by David C. Nicholls and others. Abstract: alternative electron distribution and consequences for temperature and abundance diagnostics
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