Morphology of Ionospheric Sporadic E Layer Intensity Based on COSMIC Occultation Data in the Midlatitude and Low‐Latitude Regions

Abstract

Ionospheric sporadic E layer is thin irregularity with much higher plasma density in the ionospheric E region (~90-120 km). Morphology of sporadic E intensity is investigated by using the COSMIC radio occultation data during 2007-2012. Maximum gradient value of total electron content fluctuation is defined as S max index, and it shows good linear relationship with the sporadic E intensity parameter (ordinary critical frequency, foEs) in the low-latitude and midlatitude regions. By using this S max index as the sporadic E layer intensity, distribution of sporadic E intensity is obtained. Some known features are confirmed such as the hemisphere summer enhancement, diurnal and semidiurnal behavior, and intensity depression anomaly regions. New findings are also obtained, especially the different behavior pattern in the low-latitude region. (1) Both positive and negative correlations exist between sporadic E intensity and solar activity, and this correlation also shows complex magnetic latitude dependency. (2) Weaker seasonal variation is found in the low-latitude region. Besides, hemisphere asymmetries of sporadic E intensity/location are also found during the equinox. (3) Longitudinal wave number-4 feature of sporadic E intensity is prominent in the lower latitude region, which may be related to the diurnal eastward wave number-3 tide. In a word, it is feasible to investigate the sporadic E layer intensity distribution based on radio occultation data, which also allows for a global morphology analysis.

Relationship Between Wavenumber 4 Pattern of Sporadic E Layer Intensity and Eastward Propagating Diurnal Tide With Zonal Wavenumber 3 in Low Latitude Region

“…Diurnal behavior was found in all latitude bands and semidiurnal behavior was mainly found in mid-latitude hemispheric summers. Similar results were also found by Niu et al (2019).…”

“…Much recently, Niu et al. (2019) also confirmed this phenomenon by using the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) occultation data but attributed it to the DE3 tide. However, there are still several inconsistencies such as the seasonal variation and zonal propagation direction.…”

Climatology of the Equatorial Plasma Bubbles Captured by FORMOSAT‐3/COSMIC

“…It also inhibits the vertical ion drift of the PRE, making the equatorial ionosphere more stable. The Es layers are more prevalent in solstices (Niu et al, 2019; Yeh et al, 2012), which could partly explain the absence of EPBs around 60–120°E in June solstice.…”

Spatial Characteristics on the Occurrence of the Nighttime Midlatitude Medium‐Scale Traveling Ionospheric Disturbance at Topside Ionosphere Revealed by the Swarm Satellite

“…Since E s activity is rare in the winter hemisphere (Arras et al, 2008; Niu et al, 2019; Tsai et al, 2018; Zhou et al, 2016), the considerable contribution from γ U , max at postsunset in the winter hemisphere (Figures 5a and 5e) cannot be amplified to trigger irregularities. Thus, MSTID activity is rare at postsunset.…”