Driver of the Positive Ionospheric Storm over the South American Sector during 4 November 2021 Geomagnetic Storm

Abstract

During geomagnetic storms, ionospheric storms can be driven by several mechanisms. Observations performed using ground- and space-based instruments were used to reveal the driver of the positive ionospheric storm over the South American sector during the 4 November 2021 geomagnetic storm. The positive storm appeared from 10:30 UT to 18:00 UT and covered the region from 40°S to 20°N. The maximum magnitudes of TEC (Total Electron Content) enhancement and relative TEC enhancement were about 20 TECU and 100%, respectively. Defense Meteorological Satellite Program (DMSP) also observed a significant electron density increase over South America and the eastern Pacific Ocean. In the meantime, about 50% ∑O/N2 enhancement was observed by the Global-scale Observations of the Limb and Disk (GOLD) satellite at low latitudes. Ionosonde observations (AS00Q and CAJ2M) registered an ~80 km uplift in F2 peak height (HmF2) and a prominent F2 peak electron density (NmF2) increase ~3 h after the uplift. A prominent enhancement in the cross-polar cap potential (CPCP) in the southern hemisphere was also observed by Super Dual Auroral Radar Network (SuperDARN) one hour earlier than the HmF2 uplift. Measurements of the Ionospheric Connection Explorer satellite (ICON) showed that the outward E×B drift was enhanced significantly and that the horizontal ion drift was poleward. According to the ICON ion drift observations, the HmF2 uplift was caused by an electric field rather than equatorward neutral wind. We propose that the enhanced eastward electric field dominated the positive ionospheric storm and that the thermospheric composition variation may have also contributed.

3‐D Ionospheric Imaging Over the South American Region With a New TEC‐Based Ionospheric Data Assimilation System (TIDAS‐SA)

“…The magnitude of storm-time TEC enhancements is about 40%-60% in the EIA crests region and 20%-30% in the equatorial trough region. This positive ionospheric storm was also reported by Zhai et al (2022) using 2-D ground-based GNSS TEC and 1-D in situ measurements, which are consistent with our 3-D ionospheric imaging results.…”

“…These results suggest that an enhanced eastward electric field component and upward E × B drifts, resulting from the penetration electric field that led to the ionosphere being lifted to a higher altitude with a lower recombination rate, could be one of key drivers causing this positive ionospheric storm. The data assimilation results align well with observations made by Zhai et al (2022), who used the ionosonde and ICON drift measurements to prove the aforementioned electrodynamic effect. Moreover, Zhai et al (2022) reported a ∼50% enhancement in O/N 2 in the equatorial and low-latitude regions of South America, as observed by the Global-scale Observations of the Limb and Disk (GOLD) satellite.…”

“…The SYM‐H index exhibited two major negative peaks, which are −111 nT at 08:25 UT and −117 nT at 13:00 UT on 04 November, respectively. Several previous studies have reported that this geomagnetic storm triggered notable low‐latitude ionospheric disturbances, especially over the South American sector (Rukundo, 2023; K. Wu et al., 2023; Zhai et al., 2022). This provides a good opportunity to assess our newly developed TIDAS‐SA regional data assimilation system and conduct an in‐depth analysis of the storm‐induced ionospheric perturbations.…”

Investigation of the Southern Hemisphere Mid‐High Latitude Thermospheric ∑O/N2 Responses to the Space‐X Storm

“…ionosphere responses to geomagnetic disturbances (Aa et al, 2022;C. S. Lin et al, 2022;Liou et al, 2005;Lu et al, 2012;Meier et al, 2005;Verkhoglyadova et al, 2017;Zhai, Cai, et al, 2023;Zhai, Tang, et al, 2023; since it reflects the production and loss of the ionospheric F-region plasma (Rishbeth, 1998). Additionally, O and N 2 are two of the major components of the thermosphere, influencing the total mass density of the thermosphere, which is important for monitoring and predicting the drag force of low-Earth-orbiting satellites (Dietrich et al, 2022).…”

Mid‐Latitude Ionospheric Response to a Weak Geomagnetic Activity Event During Solar Minimum

“…During the transportation and corotation process, the formed disturbance can also be altered by background winds (Cai, Burns, Wang, Qian, Solomon, et al., 2021). The thermospheric composition disturbance make contributions to the corresponding ionosphere plasma density variations to result in positive or negative ionospheric storm effect (density enhancement or depletion), especially in the daytime mid‐latitude (Fuller‐Rowell et al., 1994; Rishbeth, 1998; Zhai et al., 2022). Furthermore, the equatorward or poleward wind during storm can transport the plasma along the magnetic field line to impact the plasma density variations (J. Liu, Wang, Burns, Yue, et al., 2016), as well as the E × B drifts influenced by penetration electric field (Lu et al., 2012, 2013; Wang et al., 2010).…”