DMSP/SSUSI observations of the high-latitude dayside aurora (HiLDA

High-latitude dayside aurora (HiLDA) are large-scale discrete arcs or spot-like aurora poleward of the cusp, observed previously in the northern hemisphere by the Viking UV imager [Murphree et al., 1990] and by the IMAGE FUV [Frey et al., 2003]. The particular interest on HiLDA is to understand its formation related to the dayside reconnection and the resulted field-aligned currents (FACs) configuration in the polar cap (open field line region). In addition, the occurrence of HiLDA in the southern hemisphere is not well known.

In this study, we investigate the properties of HiLDA using DMSP/SSUSI images from the satellites F16, F17, F18, and F19. The combined data with auroral images from DMSP/SSUSI, ion drift velocity from SSIES, magnetic field perturbations from SSM, and energetic particle spectrum from SSJ make it possible to study the electrodynamics in the vicinity of the HiLDA and its connection the dayside cusp. HiLDA is formed due to monoenergetic electron precipitation (inverted-V structures) with the absence of ion precipitation. The field-aligned potential drop can be up to tens of keV. Applying the current-voltage relation, we suggest accelerated polar rain as the source of HiLDA, indirectly controlled by the solar wind/magnetosheath plasma population. The upward field-aligned current associated with the potential drop is a part of the cusp current system, produced by the dayside reconnection. Both lobe reconnection and reconnection on the duskside flanks play a role in the formation of HiLDA.

The occurrence of HiLDA is highly associated with the sunlit hemisphere and IMF By dominated conditions. Our results agree with previous observations, which show that HiLDA occurs during positive By dominated conditions in the northern summer hemisphere. We also confirmed that HiLDA occurs during negative By dominated conditions in the southern hemisphere. In addition, the fine structures of HiLDA are studied.

References

Murphree, J. S., Elphinstone, R. D., Hearn, D., and Cogger, L. L. ( 1990), Large‐scale high‐latitude dayside auroral emissions, J. Geophys. Res., 95( A3), 2345– 2354, doi:.

Frey, H. U., Immel, T. J., Lu, G., Bonnell, J., Fuselier, S. A., Mende, S. B., Hubert, B., Østgaard, N., and Le, G. ( 2003), Properties of localized, high latitude, dayside aurora, J. Geophys. Res., 108, 8008, doi:, A4.