09:00 〜 09:15
[S19-1-03] Study of the Seismic Response of Dayside Non-LTE CO2 Emissions of Planets
The dayside non-LTE emissions of CO2 molecules, at 4.3 micrometers wavelength, have been clearly imaged by the VIRTIS instrument on board Venus Express (Peralta et al., 2016). The emissions present a smoothly varying pattern as a function of solar zenith and a peak of emission power in the 125-140 km altitude depending on wavelength.
Previous observations also demonstrated sensitivity to perturbations induced by atmospheric gravity waves (Garcia et al., 2009). Due to the exponential amplification of low-frequency infrasonic waves, CO2 non-LTE emissions in the upper atmosphere are expected to vary during the pass of infrasounds excited by seismic surface waves. In this study, we present modeling results as a response of the emissions to ground-vibrations-created seismic surface waves.
Modeling work is performed in two steps. First, the infrasonic waves generated by a seismic surface wave train are propagated in the Venus atmosphere using realistic conditions including wind, attenuation, and sound velocity profiles, using outputs from a state-of-the-art Venus General Circulation Model (Gilli et al, 2017). Subsequently, density, temperature and pressure perturbations are used as input to the CO2 non-LTE emission modeling software. The variations of the emissions are predicted for various observation geometries and quake parameters. Detection limit is analyzed as a function of quake magnitude and epicentral distance to the source.
The modeling results obtained by this study directly apply to the VAMOS mission concept study currently considering the sounding of Venus internal structure by imaging seismic/infrasonic waves through variations of airglow emissions. Applications to other terrestrial planets will also be discussed. Similar systematic nadir observations on Mars may be possible soon with ACS/Exomars (Korablev et al, 2016).
Previous observations also demonstrated sensitivity to perturbations induced by atmospheric gravity waves (Garcia et al., 2009). Due to the exponential amplification of low-frequency infrasonic waves, CO2 non-LTE emissions in the upper atmosphere are expected to vary during the pass of infrasounds excited by seismic surface waves. In this study, we present modeling results as a response of the emissions to ground-vibrations-created seismic surface waves.
Modeling work is performed in two steps. First, the infrasonic waves generated by a seismic surface wave train are propagated in the Venus atmosphere using realistic conditions including wind, attenuation, and sound velocity profiles, using outputs from a state-of-the-art Venus General Circulation Model (Gilli et al, 2017). Subsequently, density, temperature and pressure perturbations are used as input to the CO2 non-LTE emission modeling software. The variations of the emissions are predicted for various observation geometries and quake parameters. Detection limit is analyzed as a function of quake magnitude and epicentral distance to the source.
The modeling results obtained by this study directly apply to the VAMOS mission concept study currently considering the sounding of Venus internal structure by imaging seismic/infrasonic waves through variations of airglow emissions. Applications to other terrestrial planets will also be discussed. Similar systematic nadir observations on Mars may be possible soon with ACS/Exomars (Korablev et al, 2016).