Abstract
This research represents a contribution to the theory on the coupling of the volcanic activity and the ionospheric dynamics, represented by total electron content (TEC) patterns and their behaviour. The ionospheric response to the activity of the Etna volcano has been analysed using global navigation satellite system (GNSS)-derived TEC values, employing data from International GNSS Service (IGS) reference station near the volcano and on two distant IGS locations. Volcanic activity has been modelled using volcanic radiative power (VRP) data obtained by the Middle InfraRed Observation of Volcanic Activity (MIROVA) system. The estimated minimal night TEC values have been averaged over defined index days of the VRP increase. During the analysed period of 19 years, the volcano activity was categorised according to pre-defined criteria. The influence of current space weather and short-term solar activity on TEC near the volcano was systematically minimised. The results showed mean/median TEC increases of approximately +3 standard deviations from the overall mean values, with peak values placed approximately 5 days before the VRP increase and followed by general TEC depletion around the time of the actual volcanic activity increase. Additionally, TEC oscillation pattern was found over the volcano site with a half-period of 6.25 days. The main interpretation of results indicates that the volcanic activity has modified the ionospheric dynamics within the nearby ionospheric region before the actual VRP increase, and that the residual impact in the volcano’s surrounding area refers to terrestrial endogenous processes and air–earth currents. Those changes can be detected during criteria predefined in the research: during quiet space weather conditions, observing night-time TEC values and within the limits of low short-term solar influence.
Highlights
The development of the ionospheric total electron content (TEC) determination methods, together with improving the means of volcanic activity monitoring, have allowed for the sensing of the seismic processes and their possible couplings with the ionospheric dynamics
By examining various TEC subset patterns, we found that minimal night TEC values vary with solar activity in an acceptably small degree (Figure 3)
The presented results suggest a causal correlation between the Etna volcano activity and the surrounding ionospheric behaviour, providing insights referring to the mutual relation between the two phenomena
Summary
The development of the ionospheric total electron content (TEC) determination methods, together with improving the means of volcanic activity monitoring, have allowed for the sensing of the seismic processes and their possible couplings with the ionospheric dynamics. Li et al [17] analysed the coupling relationship between volcanic eruption and TEC anomalies using Global Ionospheric Map (GIM) data before the 15 volcanic eruptions indicated by Volcanic Explosivity Index 4+ (VEI4+). In [22], authors analysed global navigation satellite system (GNSS)-derived short-term TEC response to the Merapi 2010 and the Kelud 2014 volcano eruptions. They observed quasi-periodic oscillation of TEC values of a frequency ~4 mHz (period ~250 s), which lasted for ~20 and ~120 min, respectively. The results are presented and discussed afterwards, drawing inferences and conclusions on obtained findings
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