Estimating the electron energy and the strength of the electric field within sprites using ground-based optical data observed over South African storms

Nnadih, S. and Kosch, M. and Mlynarczyk, J. (2021) Estimating the electron energy and the strength of the electric field within sprites using ground-based optical data observed over South African storms. Journal of Atmospheric and Solar-Terrestrial Physics, 225: 105760. ISSN 1364-6826

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Abstract

We present a new simplified method to estimate the characteristic electron energy and electric field within a mesospheric transient luminous event using ground-based calibrated and filtered optical data. We assume non-relativistic motion, a Maxwell-Boltzmann distribution, a model of the electron-neutral collision frequency, elastic electron collisions, that the collisional excitation cross-section can be assigned to a single value, and that each electron-neutral collision produces one photon on average. Example observations of carrot sprites over South Africa give estimated electron energy of 4.6–4.9 ± 0.03 eV, which compares favourably with previous similar results using more sophisticated methods. Ideally, two wavelengths should be observed simultaneously but we show a good estimate is possible with only the bright N2(1 PG) red emission.