On the Electron Temperature in the Topside Ionosphere as Seen by Swarm Satellites, Incoherent Scatter Radars, and the International Reference Ionosphere Model

Abstract

The global statistical median behavior of the electron temperature (Te) in the topside ionosphere was investigated through in-situ data collected by Langmuir Probes on-board the European Space Agency Swarm satellites constellation from the beginning of 2014 to the end of 2020. This is the first time that such an analysis, based on such a large time window, has been carried out globally, encompassing more than half a solar cycle, from the activity peak of 2014 to the minimum of 2020. The results show that Swarm data can help in understanding the main features of Te in the topside ionosphere in a way never achieved before. Te data measured by Swarm satellites were also compared to data modeled by the empirical climatological International Reference Ionosphere (IRI) model and data measured by Jicamarca (12.0°S, 76.8°W), Arecibo (18.2°N, 66.4°W), and Millstone Hill (42.6°N, 71.5°W) Incoherent Scatter Radars (ISRs). Moreover, the correction of Swarm Te data recently proposed by Lomidze was applied and evaluated. These analyses were performed for two main reasons: (1) to understand how the IRI model deviates from the measurements; and (2) to test the reliability of the Swarm dataset as a new possible dataset to be included in the underlying empirical dataset layer of the IRI model. The results show that the application of the Lomidze correction improved the agreement with ISR data above all at mid latitudes and during daytime, and it was effective in reducing the mismatch between Swarm and IRI Te values. This suggests that future developments of the IRI Te model should include the Swarm dataset with the Lomidze correction. However, the existence of a quasi-linear relation between measured and modeled Te values was well verified only below about 2200 K, while for higher values it was completely lost. This is an important result that IRI Te model developers should properly consider when using the Swarm dataset.

Estimation of Ion Temperature in the Upper Ionosphere Along the Swarm Satellite Orbits

“…Overall, the largest difference (∼19% after the correction) at low latitudes was noticeable for Swarm B satellite but the comparison was based on only 14-15 coincident data points. In recent work, Pignalberi et al (2021) examined and compared diurnal and seasonal variations of T e at around 510 km altitude for Jicamarca, Arecibo, and Millstone Hill ISRs using climatology obtained based on Swarm B high-gain LP data between 2014and 2020and ISR data between 1974and 2020 In their analysis of T e climatology trends, they found that the Swarm B LP T e correction given in Lomidze et al (2018) improves the agreement and noticeably reduces the overestimation, but large discrepancies remain for Jicamarca and during nighttime for Arecibo. This once again indicates a need to refine the low latitude calibration of Swarm LP T e values, and possibly incorporating latitudinal and diurnal dependence into the correction, as noted by Pignalberi et al (2021).…”

“…In recent work, Pignalberi et al (2021) examined and compared diurnal and seasonal variations of T e at around 510 km altitude for Jicamarca, Arecibo, and Millstone Hill ISRs using climatology obtained based on Swarm B high-gain LP data between 2014and 2020and ISR data between 1974and 2020 In their analysis of T e climatology trends, they found that the Swarm B LP T e correction given in Lomidze et al (2018) improves the agreement and noticeably reduces the overestimation, but large discrepancies remain for Jicamarca and during nighttime for Arecibo. This once again indicates a need to refine the low latitude calibration of Swarm LP T e values, and possibly incorporating latitudinal and diurnal dependence into the correction, as noted by Pignalberi et al (2021). Additionally, improvements in the Swarm LP data processing and, for example, inclusion of effects associated with the presence of light ions, which can be important source of errors at low latitudes during nighttime, is recommended.…”

Coordinated Observations of Rocket Exhaust Depletion: GOLD, Madrigal TEC, and Multiple Low‐Earth‐Orbit Satellites

“…The recent statistical investigation by Pignalberi et al. (2021) examines the Swarm temperatures in terms of local time at three ISR sites. They report that the Lomidze et al.…”

Spacecraft Potential Changes Associated With EMIC Waves in the Inner Magnetosphere

“…If the cold ions gain an energy (E i ) of ∼20 eV by the EMIC waves (Figure 3f), the electron thermal energy E e is ∼0.01 eV. Since typical electron temperatures in the top-side ionosphere and in the plasmasphere are ∼0.3 eV (e.g., Comfort et al, 1985;Pignalberi et al, 2021), the estimated 0.01 eV is an unreasonable value of the electron temperature.…”