Multiple longitude sector storm-enhanced density (SED) and long-lasting subauroral polarization stream (SAPS) during the 26–28 February 2023 geomagnetic storm

This paper conducts a multi-instrument analysis and data assimilation study of midlatitude ionospheric disturbances over the European and North American longitude sectors during a strong geomagnetic storm on 26-28 February 2023. The study uses a set of ground-based (GNSS receivers, ionosondes) observations, space-borne (DMSP, GOLD) measurements, and a new TEC-based ionospheric data assimilation system (TIDAS). We observed a series of distinct storm-time features with regard to storm-enhanced density (SED) and subauroral polarization stream (SAPS) as follows: (a) Under multiple ring current intensifications, the storm-time subauroral ionosphere produced long-lasting duskside SAPS for similar to 36 hr along with considerable dawnside SAPS for several hours. (b) Associated with long-lived SAPS, strong SED occurred consecutively in the European longitude sector near local noon during a positive ionospheric storm and later in the North American longitude sector near local dusk during a negative ionospheric storm. (c) The 3-D morphology of SED in multiple longitude sectors was reconstructed using TIDAS data assimilation technique with fine-scale details, which revealed a narrow ionospheric plasma channel with electron density enhancement and layer uplift.