Two-dimensional Vlasov simulations of fast stochastic electron heating

Speirs, David Carruthers and Eliasson, Bengt and Daldorff, Lars K. S. (2017) Two-dimensional Vlasov simulations of fast stochastic electron heating. Journal of Geophysical Research: Space Physics, 122 (10). pp. 10638-10650. ISSN 2169-9402

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    Abstract

    Ionospheric heating experiments using high frequency ordinary (O) mode electromagnetic waves have shown the induced formation of magnetic field-aligned density striations in the ionospheric F-region. These striations are observed in association with lower-hybrid (LH) and upper-hybrid (UH) turbulence and significant electron heating, further enforcing the striations. High-energy electrons can result in the ionisation of neutrals and the formation of descending artificial ionospheric layers (DAILs). In the current context, we present the results of a two-dimensional (2D) numerical simulation conducted using a Vlasov-Maxwell code to study the mode-conversion of an O mode pump wave to trapped UH waves in a small-scale density striation. Subsequent multi-wave parametric decay is observed leading to UH and LH turbulence and the excitation of large amplitude electron Bernstein (EB) waves. Large-amplitude EB waves result in significant electron heating when the wave amplitude exceeds a threshold value for stochastic motion of the electrons. For typical experimental parameters, the simulated electron temperature is observed to rise from 1500 K to more than 5000 K in a fraction of a millisecond, much faster than the usual Ohmic heating due to collisions which occurs on second-scale. The stochastic electron heating could potentially be one of the mechanisms involved in the formation of DAILs.