The balance between turbulent and convection-driven plasma vorticity in the Earth’s ionosphere

Measurements of ionospheric flow vorticity can be used for studying ionospheric plasma transport processes, such as convection and turbulence, over a wide range of spatial scales. Here, we present the spatial variation across the northern hemisphere high-latitude ionosphere of probability density functions (PDFs) of ionospheric vorticity as measured by the Super Dual Auroral Radar Network (SuperDARN) over a six-year interval (2000-2005 inclusive). These PDFs are subdivided for different polarities of the By component of the Interplanetary Magnetic Field (IMF), which allows the separation of the observed PDFs into two distinct components. These components relate to: (1) The large-scale ionospheric convection flow driven by magnetic reconnection, and (2) Meso- and small-scale processes such as turbulence. The convection vorticity PDFs are single-sided and well fit by Weibull distributions, whereas the turbulence vorticity PDFs are double-sided and symmetric, and are well fit by q-exponential distributions. Both the observed model distributions can be understood in the framework of solutions of the stationary Fokker-Planck equation for different environmental plasma conditions.