Comparison of GOLD Nighttime Measurements With Total Electron Content: Preliminary Results

Abstract

The National Aeronautics and Space Administration (NASA) Global-scale Observations of the Limb and Disk (GOLD) has been imaging the thermosphere and ionosphere since October 2018. It provides continuous measurements over a large area from its geostationary orbit. The unambiguous two-dimensional (2-D) maps of OI 135.6 nm radiance retrieved from GOLD after sunset are compared with the total electron content (TEC) maps measured by GPS receivers in the American sector. The OI 135.6 nm radiance observed by GOLD is an indicator of the peak electron density of the ionosphere F2 region, while the TEC is the total electron density in the column. Our comparisons show that the two data sets match each other very well in the equatorial ionization anomaly (EIA) morphology and its seasonal variability. Equatorial plasma bubbles (EPBs) are evident in GOLD nighttime OI 135.6 radiance. Corresponding depletions are shown in TEC maps, but without GOLD data as a reference, it is difficult to discern that the depletions are EPBs. In addition, both GOLD 135.6 radiance and TEC maps observed third peaks of electron density poleward of the southern EIA crests. Furthermore, both show that the ionosphere after sunset is quite dynamic and has strong day-today variability. In all, the GOLD and TEC have valuable synergy to allow us to gain a better understanding of the equatorial ionosphere.

First Zonal Drift Velocity Measurement of Equatorial Plasma Bubbles (EPBs) From a Geostationary Orbit Using GOLD Data

“…NASA's Global-scale Observations of the Limb and Disk (GOLD) mission observes Earth's FUV airglow emissions from geostationary orbit (Cai et al, 2020;Eastes et al, 2017Eastes et al, , 2019Eastes et al, , 2020. Disk observations by the GOLD spectrograph provide unique opportunity for more detailed information about EPBs.…”

The Ionosphere at Middle and Low Latitudes Under Geomagnetic Quiet Time of December 2019

“…the ionosphere and thermosphere could react to geomagnetic disturbance differently due to the different solar EUV energy input. The research on the ionosphere variations during the storm or quiet time in solar minimum has also been ongoing (e.g., Cai, Burns, Wang, Coster, et al, 2020;Klenzing et al, 2013;Laskar et al, 2020;Li et al, 2020). However, some ionospheric variations/phenomena during geomagnetic storms are possibly not attributed to the energy injections from the solar wind and magnetosphere.…”

Towards a Real-Time Description of the Ionosphere: A Comparison between International Reference Ionosphere (IRI) and IRI Real-Time Assimilative Mapping (IRTAM) Models

“…Figures [28][29][30] show that at Ascension Island, for the three considered solar activity levels, the IRI hmF2 modeling accuracy is improved by IRTAM especially during nighttime hours. Overall, for LSA, the hmF2 modeling precision of IRI and IRTAM can be considered equivalent during pre-sunrise and daytime hours, since the RMSE and NRMSE grids at these hours show similar patterns.…”

“…This validation and recalculation scheme is an ongoing process for empirical models and leads to the continuous improvement of the model itself. Over the years, IRI underwent many validation studies and comparisons with other ionospheric models [21][22][23][24][25][26][27][28]; on the contrary, validations of the IRTAM model are restricted to the works by Vesnin [29] and Galkin et al [18] for specific locations and conditions. Due to the ever-growing importance that IRTAM is gaining as the most used and affirmed real-time specification of the ionosphere, it is important to validate its performances against large and different datasets to quantify the improvement made by IRTAM in the description of ionospheric weather when compared to the climatological representation made by IRI.…”