10:45 〜 11:00
[PEM12-26] Recent observations of Atmospheric-Ionospheric coupling and Doppler sounding in Europe
★Invited Papers
キーワード：Ionosphere, Perturbations, Earthquake, Infrasound, Geomagnetic storm
Continuous Doppler sounding of the ionosphere is a simple and useful tool to investigate and analyze perturbations in the ionosphere on short time scales (including infrasonic periods) caused by forcing from below and above. The application of Doppler sounding will be shown on two examples:
a) Detection and analysis of infrasound waves in the European ionosphere generated by the recent devastating earthquake sequence in Turkey on 6 February 2023. Imprints of seismic P, S and Rayleigh waves were clearly observed in the ionosphere in central Europe for the second M=7.7 shock at 10:24 UT. Using observation and simulation, it is discussed that infrasound of a given frequency can only reach specific heights due to attenuation. In the studied case, the infrasound frequency was around 0.05 Hz (period ~20 s) and the waves were attenuated above ~200 km. Thus, the ionospheric co-seismic signatures were only detected for the daytime M=7.7 earthquake that occurred at 10:24 UT (11:24 LT in Czechia), but not for the nighttime M=7.8 earthquake that took place about 9 hours before at 01:17 UT, when the ionosphere was much thinner and sounding signals reflected at altitudes larger than 300 km.
b) Ionospheric disturbances observed during the geomagnetic storm on 5 November 2023 that caused large perturbations of electron densities and movement of ionospheric plasma. The ionospheric fluctuations are compared with local geomagnetic data and solar wind forcing. In addition, the effect on GNSS accuracy is presented. Regional differences between ionospheric perturbations in Belgium, Czechia and Slovakia are also shown.
a) Detection and analysis of infrasound waves in the European ionosphere generated by the recent devastating earthquake sequence in Turkey on 6 February 2023. Imprints of seismic P, S and Rayleigh waves were clearly observed in the ionosphere in central Europe for the second M=7.7 shock at 10:24 UT. Using observation and simulation, it is discussed that infrasound of a given frequency can only reach specific heights due to attenuation. In the studied case, the infrasound frequency was around 0.05 Hz (period ~20 s) and the waves were attenuated above ~200 km. Thus, the ionospheric co-seismic signatures were only detected for the daytime M=7.7 earthquake that occurred at 10:24 UT (11:24 LT in Czechia), but not for the nighttime M=7.8 earthquake that took place about 9 hours before at 01:17 UT, when the ionosphere was much thinner and sounding signals reflected at altitudes larger than 300 km.
b) Ionospheric disturbances observed during the geomagnetic storm on 5 November 2023 that caused large perturbations of electron densities and movement of ionospheric plasma. The ionospheric fluctuations are compared with local geomagnetic data and solar wind forcing. In addition, the effect on GNSS accuracy is presented. Regional differences between ionospheric perturbations in Belgium, Czechia and Slovakia are also shown.