Multiple Longitude Sector Storm‐Enhanced Density (SED) and Long‐Lasting Subauroral Polarization Stream (SAPS) During the 26–28 February 2023 Geomagnetic Storm

Abstract

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 ∼36 hours 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.This article is protected by copyright. All rights reserved.

Localized Plasma Density Peak at Middle Latitudes During the April 2023 Geomagnetic Storm

“…However, our results showed that the mid‐latitude peak on 24 April is an independent latitude feature, different from the oscillation feature generated by TID observed during this storm (Li et al., 2023). Moreover, SED usually refers to narrow enhanced TEC bands extending from the high‐density area at the mid‐latitudes in the local afternoon and dusk sectors to the higher latitudes in the noon sector (e.g., Aa et al., 2023; Coster et al., 2007; Foster, 1993). Nevertheless, the peak structure in this study stays from local dusk to midnight.…”

“…SAPS refers to greatly enhanced westward plasma drifts and poleward electric fields in the subauroral ionosphere equatorward of the electron auroral precipitation zone during storms/substorms. The westward plasma drift usually enhances with a velocity of a few hundred meters to kilometers per second levels in a narrow latitudinal band from about dusk to midnight sector (Aa et al., 2023; Foster & Burke, 2002; He et al., 2019). According to previous studies (Aa et al., 2023; He et al., 2019), the subauroral westward ion drifts with a visible independent peak and magnitude greater than 250 m/s could be identified as SAPS.…”

“…The westward plasma drift usually enhances with a velocity of a few hundred meters to kilometers per second levels in a narrow latitudinal band from about dusk to midnight sector (Aa et al., 2023; Foster & Burke, 2002; He et al., 2019). According to previous studies (Aa et al., 2023; He et al., 2019), the subauroral westward ion drifts with a visible independent peak and magnitude greater than 250 m/s could be identified as SAPS. Figure 10 illustrates the latitudinal profiles of ion density and horizontal drift velocity corresponding to the satellite passes shown in Figure 6.…”

Significant Midlatitude Bubble‐Like Ionospheric Super‐Depletion Structure (BLISS) and Dynamic Variation of Storm‐Enhanced Density Plume During the 23 April 2023 Geomagnetic Storm

“…The bottom panels of Figures 6f and 6g show that the latitudinal profiles of sunward ion flux had a noticeable subauroral enhancement in the region where SAPS overlapped with the poleward edge of the SED base region. This observation suggests that SAPS could transport vast amount of plasma from later local times toward noon via the horizontal advection, potentially contributing to the higher densities in the SED plume (Aa, Zhang, Wang, et al., 2023; Foster et al., 2007; Vlasov et al., 2003; Zou et al., 2013).…”

“…Moreover, some studies suggest that the formation of the SED plume could be related to the erosion of the outer plasmasphere (Bao et al., 2023; Goldstein et al., 2003). This is associated with the occurrence of the subauroral polarization stream (SAPS, Foster & Burke, 2002), where the horizontal advection of large plasma flux transported by the sunward SAPS flow may serve as an important source of the SED plume (e.g., Aa, Zhang, Wang, et al, 2023; Foster et al., 2007; Foster et al., 2020; Zou et al., 2013). In addition, the storm‐induced equatorward neutral wind surge (Balan et al., 2010; Mendillo, 2006), as well as the composition change with the downwelling of neutral species at mid‐to‐low latitude (Immel et al., 2001; W. Wang et al., 2012), may also contribute to the TEC/Ne enhancements in the SED region.…”