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Strong electric fields in the auroral and equatorial electrojets can distort the background ion distribution function away from Maxwellian. We developed a collisional plasma kinetic model using the Boltzmann equation and a simple BGK collision operator which predicts a relatively simple relationship between the intensity of the background electric field and the resulting ion distribution function. To test the model, we perform 3-D plasma particle-in-cell simulations and compare the results to the model. The simulation applies an elastic collision operator assuming a constant ion-neutral collision rate. These simulations show less ion heating in the Pedersen direction than the analytic model but show similar overall heating. The model overestimates the heating in the Pedersen direction because the simple BGK operator includes no angular collisional scattering in the ion velocity space. On the other hand, the fully-kinetic particle-in-cell code is able to capture the physics of ion scattering in 3-D and therefore heats ions more isotropically. Although the simple BGK analytic theory does not precisely model the non-Maxwellian ion distribution function, it does capture the overall momentum and energy flows and therefore can provide the basis of further analysis of E-region wave evolution., Comment: 16 pages, 4 figures, submitted to Frontiers

Intense electric currents called electrojets occur in weakly ionized magnetized plasmas. An example occurs in the Earth's ionosphere near the magnetic equator where neutral winds drive the plasma across the geomagnetic field. Similar processes take place in the Solar chromosphere and MHD generators. This letter argues that not all convective neutral flows generate electrojets and it introduces the corresponding universal criterion for electrojet formation, $\nabla\times (\vec{U}\times\vec{B})\neq\partial\vec{B}/\partial t$, where $\vec{U}$ is the neutral flow velocity, $\vec{B}$ is the magnetic field, and $t$ is time. This criterion does not depend on the conductivity tensor, $\hat{\sigma}$. For many systems, the displacement current, $\partial\vec{B}/\partial t$, is negligible, making the criterion even simpler. This theory also shows that the neutral-dynamo driver that generates electrojets plays the same role as the DC electric current plays for the generation of the magnetic field in the Biot-Savart law., Comment: 5 pages, 2 figures, 21 references