J.P. Reistad, N. Østgaard, K. M. Laundal, A. Ohma, K. Snekvik, P. Tenfjord, A. Grocott, K. Oksavik, S. E. Milan (2018) Observations of Asymmetries in Ionospheric Return Flow During Different Levels of Geomagnetic Activity, J. Geophsy. Res., doi.org/10.1002/2017JA025051 (pdf)