A global picture of ionospheric slab thickness derived from GIM TEC and COSMIC radio occultation observations

Abstract

The ionospheric equivalent slab thickness (EST), defined as the ratio of total electron content (TEC) to F2 layer peak electron density (NmF2), describes the thickness of the ionospheric profile. In this study, we retrieve EST from TEC data obtained from Global Ionospheric Map (GIM) and NmF2 retrieved from Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) ionospheric radio occultation data. The diurnal, seasonal, and solar activity variations of global EST are analyzed as the excellent spatial coverage of GIM and COSMIC data. During solstices, daytime EST in the summer hemisphere is larger than that in the winter hemisphere, except in some high‐latitude regions, and the reverse is true for the nighttime EST. The peaks of EST often appear at 0400 local time. The presunrise enhancement in EST appears in all seasons, while the postsunset enhancement in EST is not readily observed in equinox. Both enhancements are attributed to the more remarkable electron density decay of NmF2 compared to that of TEC. The dependence of EST on solar activity is related to the inconsistent solar activity dependences of electron density at different altitudes. Furthermore, it is interesting that EST is enhanced from 0° to 120°E in longitude and 30° to 75°S in latitude during nighttime, just to the east of Weddell Sea Anomaly, during equinox and the Southern Hemisphere summer. This phenomenon is supposed to be related to the effects of geomagnetic declination‐related plasma vertical drifts.

Statistical Analysis of Ionospheric Total Electron Content (TEC): Long-Term Estimation of Extreme TEC in Japan

“…In this study, we estimated extreme TEC values by assuming that the slab thickness has only seasonal dependence. The seasonal dependence of the slab thickness shown in Figure 5 is consistent with the results of previous studies (Jin et al, 2007;Huang et al, 2016). Another factor determining the slab thickness is the dynamics and/or composition change caused by geomagnetic disturbances.…”

Transition of Interhemispheric Asymmetry of Equatorial Ionization Anomaly During Solstices

“…Although the assumption used by the Abel inversion leads to some discrepancies between electron densities derived from the COSMIC IRO data and other observations in the lower ionosphere, their morphologies are consistent (Chu et al, ; Hu et al, ; Lei et al, ; Yue et al, ). COSMIC data have been used in various researches, including the characteristics of the F 2 layer peak electron density (NmF2), F 2 layer peak height (hmF2), slab thickness, and equatorial dynamics, and obtained reasonable results (Guo et al, ; He et al, , ; Huang et al, ; Lin, Wang, et al, ; Lin, Liu, et al, ; Liu et al, ). In this study, we used COSMIC EDPs from day 194 of 2006 to day 180 of 2017, downloaded from the COSMIC Data Analysis and Archive Center.…”

A Statistical Study on the Winter Ionospheric Nighttime Enhancement at Middle Latitudes in the Northern Hemisphere

“…We used the TEC data to calculate the equivalent slab thickness (EST) of the ionosphere in order to better understand the morphology of the topside ionosphere during the INE period. EST (in units of km) is defined as the ratio of TEC (in units of TECu, 10 16 electron/m 2 ) to NmF2 (in units of 10 12 electron/m 3 ) (e.g., Huang et al, 2016). NmF2 is obtained by NmF2 = 1.24 × 10 10 (foF2) 2 (foF2 is in units of MHz).…”