Institute of Atmospheric Physics CAS, Prague
ACOUSTIC GRAVITY WAVES AND OTHER PERTURBATIONS IN THE THERMOSPHERE AND IONOSPHERE BY CONTINUOUS DOPPLER SOUNDING
Authors: J. Chum(1), J. Laštovička(1), T. Šindelářová(1), J. Fišer(1), Z. Mošna(1),
M.A. Cabrera(2), J.-Y. Liu(3),
(1) Institute of Atmospheric Physics, Bocni II/1401, 14131 Prague 4, Czech Republic
(2) Laboratorio de Telecomunicaciones, Facultad de Ciencias Exactas y Tecnología (FACET), Universidad Nacional de Tucumán (UNT), Argentina
(3) Institute of Space Science, National Central University, Chung-Li 320, Taiwan
Corresponding author: Jaroslav Chum, email@example.com
Results of recent observations of ionospheric perturbations on short time scales obtained by international network (Czech Republic, Argentina, Taiwan and South Africa) of multipoint continuous Doppler sounders with time resolution about 10 s are presented. Examples of observation and analysis of propagation of gravity waves (GWs), equatorial spread F (ESF), infrasound from earthquake and large convective systems, as well as ionospheric perturbations caused by solar flares will be shown. Main focus will be on GWs and infrasound.
It is documented that roughly poleward propagation of GWs dominates in the local summer, whereas mainly equatorward propagation is observed in the local winter. The observations of co-seismic perturbations by Doppler sounders in the vicinity of ionosondes and seismic sensors proved that the co-seismic perturbations are caused by approximately vertically propagating infrasound waves triggered by vertical motion of the ground surface. Numerical simulations and Doppler measurements confirmed that in the vicinity from epicenters of strong earthquake, the infrasound propagates in nonlinear regime in the upper atmosphere, which resulted in the change of spectral content of the wave packet (shift toward lower frequencies) and formation of N-shaped pulse that resembled a shock wave. Infrasound waves with periods from about 0.0035 to 0.022 Hz associated with large convective systems and typhoons that passed over Taiwan were observed in the ionosphere; usually the frequency of around 0.005 Hz was recorded.