Solar Flux Influence on the In‐Situ Plasma Density at Topside Ionosphere Measured by Swarm Satellites

Abstract

In this study, we perform the first comprehensive comparison of ion density (Ni) in the topside ionosphere measured by the Langmuir probe (LP) and faceplate (FP) of the thermal ion imager on board Swarm satellites. Our results show a systematic difference between the LP and FP derived Ni values, and the systematic difference shows prominent dependences on solar flux, local time, and season. Although both Ni datasets show generally good linear regression with electron density (Ne) measurements from the incoherent scatter radar (ISR) located at Jicamarca, the Ni derived from LP shows an additional dependence on the solar flux, while such a dependence cannot be seen in the FP‐derived Ni. We suggest that the solar flux dependence of LP‐derived Ni is related to the ion compositions change at Swarm altitude, which has not been properly accounted for in the LP processing algorithm. More light ions (e.g., H+), diffusing down from the plasmasphere to the Swarm altitude, seem to cause the overestimation of Ni from LP during low solar activity. A linear relation between the Swarm LP‐derived Ni and ISR Ne is derived, and such a function is recommended to be implemented into further updates of the Swarm LP plasma density data.

The swarm Langmuir probe ion drift, density and effective mass (SLIDEM) product

“…2. This is in line with recent results suggesting that light ions lead to density over-estimations from Swarm Langmuir probe measurements (Xiong et al 2022).…”

Coherence Scale and Directivity of Nighttime Equatorial Plasma Irregularities: Results From Swarm Formation Flight

“…We have conducted similar analyses with Swarm 16 Hz density data (e.g., Aol et al., 2020), but the duty cycle of the data product is not high, especially during the recent years during which Swarm |Δ GLON | changed actively (e.g., Xiong et al., 2022, Figure 2). As a result, we cannot get enough number of observation segment pairs for reliable statistics (figure not shown).…”

A novel neural network model of Earth’s topside ionosphere

“…It is of note that the COSMIC EDPs can span over several degrees in latitude and longitude, and therefore the geographic positions of the top points of the profiles were used to train the and models, while during the model testing the profiles were assumed vertical. The P10.7 represents a smoother version of the 10.7 cm radio flux index (F10.7), and is derived as an average of the current F10.7 value and that over the previous 81 days 46 , 47 . This index has been used in a variety of ionospheric models, including the IRI model, and was found to give better performance than the raw F10.7 values 48 , which can exhibit spikes, especially during the strong solar storms.…”