Abstract:
The equatorial plasma bubbles (EPBs) are depleted plasma density regions in the ionosphere
occurring during the post-sunset hours, associated with the signal fading and scintillation signatures
in the trans-ionospheric radio signals. Severe scintillations may critically affect the performance of
dynamic systems relying on global navigation satellite system (GNSS)-based services. Furthermore,
the occurrence of scintillations in the equatorial and low latitudes can be triggered or inhibited
during space weather events. In the present study, the possible presence of the EPBs during the
geomagnetic storm periods under the 25th solar cycle is investigated using the GNSS-derived total
electron content (TEC) depletion characteristics at a low-latitude equatorial ionization anomaly
location, i.e., KL University, Guntur (Geographic 16◦260N, 80◦370E and dip 22◦320
) in India. The
detrended TEC with a specific window size is used to capture the characteristic depletion signatures,
indicating the possible presence of the EPBs. Moreover, the TEC depletions, amplitude (S4) and phase
scintillation (σϕ) indices from multi-constellation GNSS signals are probed to verify the vulnerability
of the signals towards the scintillation effects over the region. Observations confirm that all GNSS
constellations witness TEC depletions between 15:00 UT and 18:00 UT, which is in good agreement
with the recorded scintillation indices. We report characteristic depletion depths (22 to 45 TECU)
and depletion times (28 to 48 min) across different constellations confirming the triggering of EPBs
during the geomagnetic storm event on 23 April 2023. Unlikely, but the other storm events evidently
inhibited TEC depletion, confirming suppressed EPBs. The results suggest that TEC depletions
from the traditional geodetic GNSS stations could be used to substantiate the EPB characteristics for
developing regional as well as global scintillation mitigation strategies.
