Ionospheric single crest events at different altitudes and activity levels observed by Swarm constellation

Abstract

The current work makes use of eight years of electron density data observed by the Swarm constellation to study the characteristics of the equatorial ionospheric single crest phenomenon recorded at the altitudes of these satellites. The features of single crests have been investigated at different altitudes and geomagnetic activity levels. Results showed that the occurrence rate of a single crest was not significantly different between the lower and higher satellite altitudes. The relationship between the occurrence of single crests and the Kp index has shown a dramatic enhancement at high level activities. In addition, the occurrence of single crest has dramatically enhanced with the strength of both the interplanetary electric field and the north-south interplanetary magnetic field. Also, irrespective of season, the South Atlantic Anomaly (SAA) region has always shown a large occurrence of single crest events compared to other longitudes. In addition, the occurrence of the events is always larger during equinoxes than during summer and winter solstices. The significant occurrence of single crest recorded during both equinoxes and the maximum phase of the solar cycle (F10.7 index) and those observed over the SSA region, suggests an alignment between the strength of electron density and the occurrence rate of single crests.

Statistical Characteristics of Total Electron Content Intensifications on Global Ionospheric Maps

“…This is different from the previous finding of enhanced occurrences of electron density single‐peaks with increasing geomagnetic activity by Hussien et al. (2023), although they used Kp instead of Dst as the indicator for the geomagnetic activity level. According to our results, the number of intensifications has a small tendency to increase when geomagnetic activity becomes more intense, which might be caused by SED structures during intense geomagnetic storms being identified as TEC intensifications.…”

“…Hussien et al. (2023) finds that the number of single‐peak events in the electron density data from SWARM increases with increasing F10.7. Our result shows that one‐intensification case occurs more often with lower F10.7 values than higher F10.7 values, supporting the conclusion of L. Huang et al.…”

“…Deviations from the classical two‐peak EIA have also been reported. Specifically, a significant amount of single‐peak EIA events have been observed with TEC data along a certain longitude (L. Huang et al., 2014) and in situ electron density measurements (Fathy & Ghamry, 2017; Hussien et al., 2023). The single peaks could be manifestations of strong asymmetry in northern and southern EIA crests, which are caused by weakened equatorial plasma fountain and the neutral wind crossing the equator (Fathy & Ghamry, 2017; L. Huang et al., 2014).…”

Temporal Variability of Equatorial Ionization Anomaly Crest Locations Extracted From Global Ionospheric Maps

“…Second, in our selection of the double‐peaked EIAs, more two‐intensification cases during northern hemispheric summer than during other seasons are ruled out due to their longitudinal distance exceeding the criterion of 45°. The excluded two‐intensification cases could be latitudinally single‐crest events (L. Huang et al., 2014; Fathy & Ghamry, 2017; Loutfi et al., 2022; Hussien et al., 2023), which were also found to occur more often around June solstice than other time of year (L. Huang et al., 2014; Fathy & Ghamry, 2017).…”

Occurrence Characteristics of Nighttime Merged EIA Based on NASA GOLD Observations from 2018 to 2023

“…It should be noted that the single-peak EIA encompasses various mechanisms, such as the formation of EIA through the merging of two EIA crests on 15 January 2022 and 27 August 2022 (see Supplementary Materials S1 and S4) or the formation of single-peak EIA due to the disappearance of another EIA crest (such as the EIA crests on 26 April 2023 and 27 August 2023; see Supplementary Materials S2 and S3). In previous studies [22,23], the instantaneous observations from in situ satellites on a single orbit are unable to identify the reasons for the formation of a single-peak EIA. These types have all been classified as single-peak EIA.…”