Japan Geoscience Union Meeting 2021

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[J] Oral

P (Space and Planetary Sciences ) » P-CG Complex & General

[P-CG18] Planetary Magnetosphere, Ionosphere, and Atmosphere

Thu. Jun 3, 2021 10:45 AM - 12:15 PM Ch.04 (Zoom Room 04)

convener:Kanako Seki(Graduate School of Science, University of Tokyo), Hiroyuki Maezawa(Department of Physical Science Osaka Prefecture University), Takeshi Imamura(Graduate School of Frontier Sciences, The University of Tokyo), Naoki Terada(Graduate School of Science, Tohoku University), Chairperson:Yuki Harada(Kyoto University), Takeshi Imamura(Graduate School of Frontier Sciences, The University of Tokyo), Naoki Terada(Graduate School of Science, Tohoku University)

12:00 PM - 12:15 PM

[PCG18-12] Periodic variations of hydrogen and oxygen airglow in the Martian upper atmosphere during a rapid growth of a regional dust storm

*Kei Masunaga1, Naoki Terada2, Nao Yoshida2, Takeshi Kuroda2, Kazuo Yoshioka3, Tomoki Kimura2, Fuminori Tsuchiya2, Go Murakami4, Atsushi Yamazaki4, Ichiro Yoshikawa3 (1.University of Colorado Boulder, 2.Tohoku University, 3.University of Tokyo, 4.Institute of Space and Astronautical Science)

Keywords:Mars, Hisaki space telescope, Airglow, Dust storm

Analyzing extreme ultraviolet (EUV) spectra of the Martian upper atmosphere obtained from the Hisaki space telescope, we study variations of hydrogen (HI Ly-β) and oxygen (OI 135.6 nm) airglow during a rapid expansion of a regional dust storm that occurred in Mars Year 33. We find that Ly-β brightness did not vary with the solar EUV flux but significantly increased over the observation period (LS=213°-232°), while OI 135.6 mainly varied with the solar EUV flux. After subtracting the seasonal and solar effects from Ly-β and OI 135.6 nm brightness, respectively, it was found that their residual brightness varied with a ~6-8-day periodicity and that the OI 135.6 nm residual brightness approximately varied in quadrature with that of Ly-β. The variation level for both emissions was ~20-40% for the whole disk. This indicates that when hydrogen atoms are globally produced by water vapor transported from the lower atmosphere during the dust storm expansion, the amount of oxygen atoms significantly decreases in the upper atmosphere of Mars. In this presentation, we discuss a role of atmospheric waves such as baroclinic waves that usually present in the northern hemispheric lower atmosphere in this season as a possible candidate to cause the periodic airglow variations in the upper atmosphere. We also discuss a cause of the anti-correlation between the hydrogen and oxygen airglow emissions, by analyzing variations of other emission lines such as OII 83.4 nm and ArI 106.6 nm, and CO bands as well as the hydrogen and oxygen emissions.