Status: this preprint is open for discussion and under review for Annales Geophysicae (ANGEO).
Are drivers of northern lights in the ionosphere?
Osuke Saka
Abstract. Within the first minute of Pi2 onset, macro-scale free vortices -characterized by two-cell, irrotational vortical flows- are excited in the midnight sector of the inner magnetosphere. This state persists for approximately 10 minutes. Rather than serving as a direct source of field-aligned current, these free vortex perturbations excite guided poloidal waves. As these waves transmit to the ionosphere, they create localized space charges. To maintain quasi-neutrality, ionosphere responds by generating parallel potential drops and outflows. These parallel potential drops subsequently produce a forced vortex that propagates down to the polar ionosphere. Within this forced vortex, electron fluids composed of primary and secondary electrons (which manifest as the aurora) undergo ExB drifts. Ultimately, the primary driver for the generation of these parallel potential drops resides within the polar ionosphere itself.
Received: 29 Aug 2026 – Discussion started: 30 Sep 2026
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During the first 10 minutes following Pi2 onset, plasma convection in the midnight sector of the inner magnetosphere behaves as free, irrotational vortex flows. Within these irrotational convections, forced vortices (rotational flows) are generated above the ionosphere where parallel potential drops occur. The flapping motion of the aurora manifests within the electrostatic potential associated with these forced vortices.
During the first 10 minutes following Pi2 onset, plasma convection in the midnight sector of the...
