Periodic variations of oxygen EUV dayglow in the upper atmosphere of Venus: Hisaki/EXCEED observations

K. Masunaga (1, 2) , K. Seki (2, 1, 3) , N. Terada (4) , F. Tsuchiya (5) , T. Kimura (6) , K. Yoshioka (7, 1) , G. Murakami (8) , A. Yamazaki (8) , M. Kagitani (5) , Chihiro Tao (9, 10) , Andrei Fedorov (10) , Y. Futaana (11) , T. L. Zhang (12) , D. Shiota (2) , François Leblanc (13) , Jean-Yves Chaufray (13) , I. Yoshikawa (14)

1 Department of Earth and Planetary Science [Tokyo]
2 ISEE - Institute for Space-Earth Environmental Research [Nagoya]
3 STEL - Solar-Terrestrial Environment Laboratory [Nagoya]
4 Department of Geophysics [Sendai]
5 PPARC - Planetary Plasma and Atmospheric Research Center [Sendai]
6 RIKEN RNC - RIKEN Nishina Center for Accelerator-Based Science [Wako]
7 Department of Physics [Tokyo]
8 ISAS - Institute of Space and Astronautical Science
9 NICT - National Institute of Information and Communications Technology [Tokyo]
10 IRAP - Institut de recherche en astrophysique et planétologie
11 IRF - Swedish Institute of Space Physics [Kiruna]
12 IWF - Space Research Institute of Austrian Academy of Sciences
13 HELIOS - LATMOS
14 Department of Complexity Science and Engineering [Tokyo]

Using the Extreme Ultraviolet Spectroscope for Exospheric Dynamics (EXCEED) aboard Hisaki and the Solar Extreme Ultraviolet Monitor on the Solar and Heliospheric Observatory, we investigate variations of the extreme ultraviolet (EUV) dayglow brightness for OII 83.4 nm, OI 130.4 nm, and OI 135.6 nm in the Venusian upper atmosphere observed in March–April (period 1), April–May (period 2), and June–July (period 3) in 2014. The result shows that characteristic periodicities exist in the dayglow variations other than the ~27 day solar rotational effect of the solar EUV flux: 1.8, 2.8, 3.1, 4.5, and 9.9 day in period 1; 1.1 day in period 2; and 1.0 and 11 day in period 3. Many of these periodicities are consistent with previous observations and theory. We suggest these periodicities are related to density oscillations of oxygen atoms or photoelectrons in the thermosphere. The cause of these periodicities is still uncertain, but planetary-scale waves and/or gravity waves propagating from the middle atmosphere, and/or minor periodic variations of the solar EUV radiation flux may play a role. Effects of the solar wind parameters (velocity, dynamic pressure, and interplanetary magnetic field's intensity) on the dayglow variations are also investigated using the Analyser of Space Plasma and Energetic Atoms (ASPERA-4) and magnetometer aboard Venus Express. Although clear correlation with the dayglow variations is not found, their minor periodicities are similar to the dayglow periodicities. Contribution of the solar wind to the dayglow remains still unknown, but the solar wind parameters might affect the dayglow variations.

Mots clés: upper atmosphere; Hisaki; Venus; EXCEED; EUV dayglow; solar wind interaction

Domaines: Physique Atmosphérique et Océanique [physics.ao-ph]; Géophysique [physics.geo-ph]

K. Masunaga, K. Seki, N. Terada, F. Tsuchiya, T. Kimura, et al.. Periodic variations of oxygen EUV dayglow in the upper atmosphere of Venus: Hisaki/EXCEED observations. Journal of Geophysical Research. Planets, 2015, 120 (12), pp.2037-2052. ⟨10.1002/2015JE004849⟩. ⟨insu-01240163⟩