Long-Term Variations of Plasmaspheric Total Electron Content from Topside GPS Observations on LEO Satellites

Abstract

The plasmasphere is located above the ionosphere with low-energy plasma, which is an important component of the solar-terrestrial space environment. As the link between the ionosphere and the magnetosphere, the plasmasphere plays an important role in the coupling process. Therefore, it is of great significance to study the electron content variation of the plasmasphere for the solar-terrestrial space environment. Nowadays, the topside global positioning system (GPS) observations on Low Earth Orbit (LEO) satellites provide a unique opportunity to estimate and study variations in the plasmasphere. In this paper, the plasmaspheric total electron content (PTEC) is estimated, and its long-term variations are studied from topside GPS observations onboard the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC). The PTEC in the daytime is higher than that in the nighttime, with the peak between 14:00 and 17:00 in the magnetic local time, while the minimum value of PTEC in the belt appears between 3:00 and 6:00 in the magnetic local time before sunrise. For seasonal variations, the PTEC is the highest in spring of the northern hemisphere and the lowest in summer of the northern hemisphere regardless of the state of the solar activity. The long-term variation in PTEC is further analyzed using 11-year COSMIC GPS observation data from 2007 to 2017. A high correlation between PTEC and the F10.7 indices is found. Particularly in the geomagnetic high-latitude region during the daytime, the correlation coefficient reaches 0.93. The worst case occurs during the nighttime in the geomagnetic middle-latitude region, but the correlation coefficient is still higher than 0.88. The long-term variations of plasmaspheric TEC are mainly related to the solar activity.

A Statistical Model of Inner Magnetospheric Electron Density: Van Allen Probes Observations

“…Previous studies have shown that the change of the PTEC is closely related to solar radio flux at 10.7 cm (Jin et al., 2021; Zhang et al., 2016). PTEC can be calculated by the following formula (Foelsche and Kirchengast, 2002; Jin et al., 2021; Zhang et al., 2016): $$$\mathrm{P}\mathrm{T}\mathrm{E}\mathrm{C}=\mathrm{p}\mathrm{o}\mathrm{d}\mathrm{T}\mathrm{E}\mathrm{C}\times \mathrm{f}(\varepsilon )$$$ $$$\mathrm{f}(\varepsilon )=\frac{\mathrm{sin}\,\varepsilon +\sqrt{{\left({R}_{\mathrm{p}\mathrm{p}\mathrm{t}}/{R}_{\mathrm{o}\mathrm{r}\mathrm{b}}\right)}^{2}-{(\cos \,\varepsilon )}^{2}}}{1+{R}_{\mathrm{p}\mathrm{p}\mathrm{t}}/{R}_{\mathrm{o}\mathrm{r}\mathrm{b}}}$$$ $$${R}_{\mathrm{p}\mathrm{p}\mathrm{t}}={R}_{E}+{H}_{\mathrm{p}\mathrm{p}\mathrm{t}}$$$ $$${R}_{\mathrm{o}\mathrm{r}\mathrm{b}}={R}_{E}+{H}_{\mathrm{o}\mathrm{r}\mathrm{b}}$$$ where $$\mathrm{f}(\varepsilon )$$ is the conversion coefficient, podTEC is precise orbit determination (POD) antenna TEC me...…”

“…Science question 2: Can we ignore the contribution of geomagnetic activity to PTEC? Most of LEO-based TEC studies have focused on the investigation of the topside ionospheric responses to geomagnetic storms (Astafyeva, 2009;Astafyeva et al, 2015;Kuai et al, 2017;Lei et al, 2014Lei et al, , 2015Lei et al, , 2016Mannucci et al, 2005;Zhong et al, 2016a) and other climatology characteristics of the topside ionosphere and plasmasphere (Jin et al, 2021;Noja et al, 2013;Pedatella and Larson, 2010;Yizengaw et al, 2008;Zhang et al, 2016;Zhong et al, 2017). There have been very limited long-term studies on the impact of different geomagnetic conditions on the PTEC.…”

Low-Latitude Ionospheric Responses and Coupling to the February 2014 Multiphase Geomagnetic Storm from GNSS, Magnetometers, and Space Weather Data

“…CMEs can produce stronger storms than CIRs and are usually initiated by a southward interplanetary magnetic field (IMF), which enhances the night-side convection and increases the ring current. When CIRs and CMEs reach Earth, solar wind/magnetosphere coupling processes generate a rapid increase in Poynting flux; they result in an enhancement of Joule heating, which leads to disturbances in upper atmosphere composition, temperature, density, and winds (e.g., [4,[17][18][19][20]).…”

Undifferenced Kinematic Precise Orbit Determination of Swarm and GRACE-FO Satellites from GNSS Observations

“…Low Earth Orbit (LEO) satellite is a valuable platform for Earth observation due to the low altitude, short period, and rapid connection with the ground [ 1 ]. The observation data collected by the LEO satellite have been widely used in geosciences with a wide area coverage, such as crustal deformation [ 2 , 3 ], ocean altimetry [ 4 ], Earth gravity field recovery [ 5 , 6 ], space weather [ 7 , 8 ] and remote sensing [ 9 , 10 ]. To ensure successful scientific applications undertaken by the LEO satellite, the precise orbit determination (POD) for the LEO satellite is essential.…”