Simultaneous Observation of Equatorial Plasma Bubbles and Traveling
Ionospheric Disturbances over Indonesia Following the 15 January 2022
Tonga Volcano Eruption
Abstract
We report our analysis of multi-diagnostic ionospheric observations over
Indonesia following the 15 January 2022 Tonga volcano eruption.
Observation data from the Indonesian GNSS CORS network, ionosondes, and
GISTM receivers, in conjunction with the Himawari-8 satellite imagery,
were used in the analysis. The Lamb waves from the eruption, traveling
at ~310 m/s, reached eastern part of Indonesia
(~5,000 km from Tonga) approximately 4 hours after the
eruption. The Lamb waves traversed the Indonesian region for 4 hours and
40 minutes, around sunset period. As a result, some unseasonal
equatorial plasma bubbles (EPBs) occurred over this longitude sector,
with an earlier-than-usual onset time. There was a directional split in
the zonal drift velocity of these EPBs, where some EPBs drifted eastward
with a velocity of 138.0 ± 6.9 m/s and others westward with a velocity
of 39.6 ± 2.0 m/s. At the same time, traveling ionospheric disturbances
(TIDs) from the Tonga eruption also propagated over the Indonesian
region with a velocity of 434.6 ± 21.7 m/s. In the total electron
content (TEC) data, interactions between EPBs and TIDs were observed
over the region. There were enhancements in the rate-of-TEC index (ROTI)
and S4 scintillation index, indicating the presence of ionospheric
density irregularities. A turbulent ionospheric F-layer, due to these
EPBs and TIDs, caused either spread-F echoes or a loss of F-region
traces in the ionograms. An intensification of sporadic-E layer, lasting
for a few hours, was also observed in the ionograms.