On the nature of high-latitude ionospheric fluctuations associated with the Kelvin-Helmholtz Instability

Plasma “irregularities” spanning a wide range of scales are known to be common in the high-latitude ionosphere. Since the irregularities are commonly observed close to density gradients, flow shears, and the aurora, processes such as the gradient-drift instability, the Kelvin-Helmholtz instability (KHI), and particle precipitation related phenomena are often suggested as important mechanisms for their generation [1 and ref. therein]. However, unravelling the details about the creation and development of the irregularities and turbulence at high latitudes remains a challenge, both observationally and computationally [e.g., 1].
Using the Geospace Environment Model of Ion-Neutral Interactions (GEMINI) [2], we performed numerical simulations of the evolution of the ionospheric KHI. We computed several parameters typically used in turbulence analysis for both density and velocity fluctuations and characterized their similarities and differences for varied “ideal” initial conditions, including different shear sizes, velocities, density gradients, and inertial capacitances. The results provide insights into the nature of the fluctuations during both the growth and the fully developed stage of the instability, and a basis for comparison with observations of irregularities coinciding with flow shears at high latitudes.
[1] Nishimura, Y., Verkhoglyadova, O., Deng, Y., and Zhang S.-R. (Eds.) (2022). in "Cross-Scale Coupling and Energy Transfer in the Magnetosphere-Ionosphere-Thermosphere System", Chapter 3 - "Density, irregularity, and instability". Elsevier. https://doi.org/10.1016/B978-0-12-821366-7.00001-9
[2] Zettergren, M. D., and Snively, J. B. (2015). "Ionospheric response to infrasonic-acoustic waves generated by natural hazard events". Journal of Geophysical Research: Space Physics, 120(9), 8002–8024. https://doi.org/10.1002/2015JA021116