Significant ionospheric hole and equatorial plasma bubbles after the
2022 Tonga volcano eruption
Abstract
This paper investigates the local and global ionospheric responses to
the 2022 Tonga volcano eruption, using ground-based Global Navigation
Satellite System (GNSS) total electron content (TEC), Swarm in-situ
plasma density measurements, the Ionospheric Connection Explorer (ICON)
Ion Velocity Meter (IVM) data, and ionosonde measurements. The main
results are as follows: (1) A significant local ionospheric hole of more
than 10 TECU depletion was observed near the epicenter
~45~min after the eruption, comprising
of several cascading TEC decreases and quasi-periodic oscillations. Such
a deep local plasma hole was also observed by space-borne in-situ
measurements, with an estimated horizontal radius of 10-15 deg and
persisted for more than 10 hours in ICON-IVM ion density profiles until
local sunrise. (2) Pronounced post-volcanic evening equatorial plasma
bubbles (EPBs) were continuously observed across the wide Asia-Oceania
area after the arrival of volcano-induced waves; these caused a Ne
decrease of 2-3 orders of magnitude at Swarm/ICON altitude between
450-575~km, covered wide longitudinal ranges of more
than 140 deg and lasted around 12 hours. (3) Various acoustic-gravity
wave modes due to volcano eruption were observed by accurate Beidou
geostationary orbit (GEO) TEC, and the huge ionospheric hole was mainly
caused by intense shock-acoustic impulses. TEC rate of change index
revealed globally propagating ionospheric disturbances at a prevailing
Lamb-wave mode of ~315 m/s; the large-scale EPBs could
be seeded by acoustic-gravity resonance and coupling to less-damped Lamb
waves, under a favorable condition of volcano-induced enhancement of
dusktime plasma upward ExB drift and postsunset rise of the equatorial
ionospheric F-layer.