4:45 PM - 5:00 PM
[PCG32-06] Millimeter-Wave Band Monitoring Observations of the Terrestrial Planets in the Solar System with 10-m SPART Telescope
The results obtained with SPART suggest that the disk-averaged mixing ratio of carbon monoxide derived at an altitude of approximately 80 km in Venus has steadily decreased since 2012. The X- and M-class solar events that reached Venus also seem to have decreased from 2012 to 2014. To study the electron production rate induced by solar energetic particles incident at different altitudes of the planetary middle atmospheres, we also developed an analytical model, using which ionization losses are numerically calculated on the basis of the Bethe?Bloch formula. The ionization of carbon dioxide induced by solar-energetic-particle events is considered to increase the production rate of CO. With a basic model under conditions of typically great solar-proton events with incident-proton energies of less than 1 GeV, it was found that the ionization rate reaches its maximum at an altitude of 80?90 km in the Venusian atmosphere. These results suggest that the decrease in CO in the Venusian middle atmosphere may be deeply related to the solar activities.
In this conference, we will present these results and the status of the SPART project.