On the Variation of Column $O/N\textsubscript{2} $ in the upper atmosphere using Principal Component Analysis in 2-dimensional images

Abstract

Day-to-day variability in thermospheric composition is driven by solar, geomagnetic and meteorological drivers. The ratio of the column density of atomic oxygen and molecular nitrogen (O/N\textsubscript{2}) is a useful parameter for quantifying this variability that has been shown to exhibit close correspondence to F-region electron density, total electron content and upper atmospheric transport. Therefore, understanding the variability in O/N\textsubscript{2} gives an insight into the geophysical variability of other relevant ionospheric and thermospheric parameters. The relative contributions of these drivers for thermospheric variability is not well known. Here we report a new analysis of the variability in O/N\textsubscript{2} to identify the sources of variability in a 55-day time period. Principal Component Analysis (PCA) was performed on thermospheric O/N\textsubscript{2} column density ratio from days 81 to 135 of 2020 from NASA's Global-scale Observations of the Limb and Disk (GOLD) mission. We find that geomagnetic activity is the major source of variability in O/N\textsubscript{2} column density ratio, followed by solar-driven transport and meteorological driving from the lower atmosphere. The first component (PC1) showed a strong correlation to Kp index and IMF, and geomagnetic storm effects are seen in the wavelet analysis of PC1's weights. The fifth component (PC5) showed a strong quasi-6-day oscillation(Q6DO). The higher explained variance ratio of PC1 suggests a stronger effect of geomagnetic activity relative to meteorological forcing from planetary scale waves. The methodology of the present study also demonstrates how PCA can be used to isolate and rank different sources of variability in other IT parameters.

GOLD Synoptic Observations of Quasi‐6‐Day Wave Modulations of Post‐Sunset Equatorial Ionization Anomaly During the September 2019 Antarctic Sudden Stratospheric Warming

“…The recently launched GOLD mission is distinctive from previous aeronomy missions (Eastes et al., 2020). Having a unique observational sampling—also called synoptic view—enables GOLD to monitor the space weather of the ionosphere from meso‐scale plasma bubbles (Eastes et al., 2019) to large‐scale wave signatures (Gan et al., 2020a; Goel et al., 2022) in the EIA region across the South America, the Atlantic Ocean and the western coast of Europe and Africa. Based on this observational capability and through the combination with middle atmosphere observations made by SABER/TIMED (Sounding of the Atmosphere using Broadband Emission Radiometry/Thermosphere Ionosphere Mesosphere Energetics and Dynamics), the overarching goal of this work is to study the coupling of the post‐sunset ionospheric EIA with the Q6DW propagating from the middle atmosphere during the September 2019 SSW.…”

On the Variation of Column Density Ratio ΣO/N2 in the Upper Atmosphere Using Principal Component Analysis in 2‐Dimensional Images

“…jhuapl.edu/.The Python code of this work is available at https://github.com/divyam123-EECS-Physics/GOLD-PCA.git. The Pythocode and the subset of the aforementioned data sets used in this study is also available on Zenodo (Goel, 2023).…”

Thermospheric Responses to the 3 and 4 November 2021 Geomagnetic Storm During the Main and Recovery Phases as Observed by NASA's GOLD and ICON Missions

“…One of the key state parameters that ICON measures is wind profiles spanning 90–300 km at low and middle latitudes (Englert et al., 2023; Harding et al., 2021; Makela et al., 2021), and GOLD provides unparalleled synoptic observations of disk O/N 2 and temperatures (Eastes et al., 2020). The two missions have been revolutionizing the understanding of the ionosphere‐thermosphere dynamics during solar and geomagnetically active and quiet times (e.g., Cai et al., 2023; Eastes et al., 2020; England et al., 2020; Gan et al., 2020a, 2020b, 2023a, 2023b; Goel et al., 2023; Immel et al., 2023; Laskar et al., 2022; McGinness et al., 2023; Oberheide et al., 2020). The current investigation is motivated by a previous study—Gan et al.…”