Open Access

Table 1

List of ionosonde observatories used in this work, in order of decreasing latitude. Note that the longitudes for the three stations to the West of the Greenwich meridian are listed with negative longitudes. Distances and bearings to the location of the eruption were calculated using the calculator freely available online at this URL: This calculator takes into account the WGS-84 shape of the Earth, using the formulas found in Vincenty (1975).

Name Ursicode Latitude Longitude Ionosonde Cadence Distance Azimuth
Juliusruh JR055 54.6°N 13.4°E DPS-4D 5 min 15,931 km 29.0°
Fairford FF051 51.7°N −1.5°E DPS-4D 7.5 min 16,536 km 5.6°
Chilton RL052 51.5°N −0.6°E DPS-1 10 min 16,551 km 7.3°
Dourbes DB049 50.1°N 4.6°E DPS-4D 5 min 16,626 km 17.2°
Pruhonice PQ052 50.0°N 14.6°E DPS-4D 15 min 16,326 km 34.3°
Sopron SO148 47.6°N 16.7°E DPS-4D 15 min 16,443 km 39.9°
Rome RO041 41.9°N 12.5°E DPS-4 15 min 17,148 km 39.3°
Roquetes °EB040 40.8°N 0.5°E DPS-4D 5 min 17,707 km 13.7°
San Vito VT139 40.6°N 17.8°E DPS-4D 7.5 min 16,940 km 50.3°
Athens AT138 38.0°N 23.5°E DPS-4D 5 min 16,694 km 62.3°
Gibilmanna GM037 37.9°N 14.0°E AIS-I°NGV 15 min 17,384 km 48.1°
El Arenosillo EA036 37.1°N −6.7°E DPS-4D 5 min 18,158 km 353.19°

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