Ionospheric detection and localization of volcano eruptions on the example of the April 2015 Calbuco events

Abstract

AbstractUsing data from ground‐based Global Navigation Satellite Systems (GNSS) receivers located in southern Chile, we study the ionospheric total electron content (TEC) response to two eruptions of the Calbuco volcano that occurred on 22–23 April 2015. In both cases, the TEC response showed quasi‐periodic signals with several consecutive wave trains. The averaged amplitude of the observed covolcanic TEC perturbations amounted 0.45 total electron content unit, 1 TECU = 1016 el m−2 (TECU) for the first eruption and 0.16 TECU for the second one. We compare amplitudes of the TEC response to volcano eruptions of different intensity from our and previously published data, and we show that both the intensity and the background ionospheric conditions define the amplitude of ionospheric covolcanic disturbances. The relative contribution, however, scales with the eruption intensity. The traveltime diagrams allowed to estimate the propagation speed of the observed covolcanic TEC perturbations as ~900–1200 m/s, which is close to the acoustic (or shock acoustic) waves speed at the ionospheric height. The spectrograms are consistent with the conclusion on the acoustic nature of the observed TEC perturbations. Finally, we use the approximation of a spherical wave propagating at a constant velocity from a point source, and for the first time, we calculate the location of the volcanic source and the onset time of the volcano eruption from ionospheric measurements. We show that even from 30 s ionospheric GPS data it is possible to “localize” the eruptive source within several degrees of latitude/longitude.