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Intense electric currents called electrojets occur in weakly ionized magnetized plasmas. An example occurs in the Earths 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, $ ablatimes (vec{U}timesvec{B}) eqpartialvec{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, $partialvec{B}/partial t$, 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.
We perform fully kinetic simulations of flows known to produce dynamo in magnetohydrodynamics (MHD), considering scenarios with low Reynolds number and high magnetic Prandtl number, relevant for galaxy cluster scale fluctuation dynamos. We find that
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