Investigating the Relationship Between Plasma Bubbles, Ionospheric Pierce Points, and ROTI Using ASI and GPS Observations.

We investigate the presence and structure of equatorial plasma bubbles (EPBs) over El Leoncito, Argentina, by combining airglow observations from an all-sky imager (ASI) with ionospheric irregularity signatures derived from the Rate of Total Electron Content Index (ROTI), calculated from GPS measurements, on the geomagnetically quiet night of September 13, 2017. The ASI images captured the full life cycle of multiple EPBs, while the ROTI values showed enhanced ionospheric irregularities during the same periods when airglow depletions were prominent. Both datasets were used to compare the timing and location of airglow depletions' presence with the GPS signal trajectory, aiming to evaluate whether the GPS signals traversed plasma bubbles and how this influenced the values of ROTI. The ionospheric pierce points (IPPs) of the signals were calculated, and their geographic coordinates were projected onto ASI images. The analysis reveals a strong spatial-temporal correlation between the elevated ROTI values and the intersection of the signal paths with plasma bubble regions in ASI images. The results show that signals from certain satellites exhibited enhanced ROTI values when their paths passed through airglow depletion regions, confirming that EPBs are the source of the observed ionospheric irregularities. In contrast, satellites whose signal paths did not intersect plasma bubbles maintained low and stable ROTI values.