A simple kinetic theory of auroral arc scales

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Abstract
A kinetic theory of the origins of the auroral arc scale spectrum is presented in this paper. The conceptual basis of the theory is current conservation in a turbulent plasma at the magnetospheric equatorial region in which a field‐aligned current is generated and the local electrostatic potential structure is forced to adjust to the presence of the field‐aligned current. This simple model uses an ad hoc Ohm's law relationship between the perpendicular current and the perpendicular electric field, but with a negative conductance in the generator region so that J⊥·E⊥ < 0. An exact solution of a simple model of the concept yields a bistatic auroral generator for which multiple‐arc formation is predicted if the field‐aligned current exceeds a critical value. The predicted scale spectrum is inversely proportional to the square root of the field‐aligned current strength spectrum.