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Abstract We report on a novel scenario of subauroral arcs within strong subauroral ion drifts (SAID)‐STEVE and Picket Fence. Their explanation requires a local source of low‐energy,ε < 18.75 eV, suprathermal electrons, and N₂vibrational and electronic excitation below ∼270 km. We show that the ionospheric feedback instability in strong SAID flows with depleted density troughs generates intense, small‐scale field‐aligned currents and parallel electric fields below the F₂peak. With these fields, we employed a rigorous numerical solution of the Boltzmann kinetic equation for the distribution of ionospheric electrons and determined the power going to excitation and ionization of neutral gas (the energy balance). The obtained suprathermal electron population and energy balance at altitudes of ∼130–140 km are just what is necessary for Picket Fence. Concerning STEVE, the kinetic theory predictions are in a good qualitative agreement with its basic features, such as the enhanced continuum emissions. Besides, the theory predicts that subauroral arcs might have the transient phase with typical aurora‐like emissions that fade out afterward. 

Abstract Ultralow frequency (ULF) electromagnetic waves are regularly detected by satellites near the plasmapause during substorms. Usually, the small‐scale waves are observed embedded in the large‐scale, quasi‐stationary electric field. We suggest that the small‐scale waves are generated in the ionosphere by the interactions between the large‐scale field and irregularities in the ionospheric density/conductivity. Under certain conditions, these waves can be trapped in the global magnetospheric resonator and amplified by the positive feedback interactions with the ionosphere. To verify this hypothesis, we model with a two‐fluid magnetohydrodynamics code structure and amplitude of the ULF waves simultaneously observed near the plasmapause by the Defense Meteorological Satellite Program satellite at low altitudes and the Combined Release and Radiation Effects satellite at high altitudes. Simulations reproduce in good, quantitative detail the structure and amplitude of the observed waves. In particular, simulations reproduce a “spiky” character of the electric field observed by the Defense Meteorological Satellite Program satellite at low altitude, which is a characteristic feature of ULF waves produced by the ionospheric feedback instability.