サガワ ヒデオ   SAGAWA HIDEO
  佐川 英夫
   所属   京都産業大学  理学部 宇宙物理・気象学科
   職種   教授
言語種別 英語
発行・発表の年月 2012/10
形態種別 研究論文
査読 査読あり
標題 Wind mapping in Venus' upper mesosphere with the IRAM-Plateau de Bure interferometer
執筆形態 その他
掲載誌名 Astronomy & Astrophysics
出版社・発行元 EDP SCIENCES S A
巻・号・頁 546,pp.A102
著者・共著者 Moullet, A,Lellouch, E,Moreno, R,Gurwell, M,Sagawa, H
概要 Context. The dynamics of the upper mesosphere of Venus (similar to 85-115 km) have been characterized as a combination of a retrograde superrotating zonal wind (RSZ) with a sub-solar-to-antisolar flow (SSAS). Numerous mm-wave single-dish observations have been obtained and been able to directly measure the mesospheric line-of-sight winds by mapping the Doppler shifts of CO rotational lines, but their limited spatial resolution makes their interpretation difficult.
Aims. By using interferometric facilities, one can achieve a higher resolution in Doppler-shift maps, allowing us in particular to place firmer constraints on the respective contributions of the SSAS and RSZ circulations to the global mesospheric wind field.
Methods. We report on interferometric observations of the CO(1-0) line obtained with the IRAM-Plateau de Bure interferometer in November 2007 and June 2009, which was able to map the upper mesosphere dynamics on the morning hemisphere with a high spatial resolution (3.5-5.5 '').
Results. All the obtained measurements show, with a remarkably high temporal stability, that the wind globally flows in the (sky) east-west direction, corresponding in the observed geometry to either an unexpected prograde zonal wind or a SSAS flow. A very localized inversion of the wind direction, which could correspond to a RSZ wind, is also repeatedly detected in the night hemisphere. The presence of significant meridional winds is not evidenced. Using models with different combinations of zonal and SSAS winds, we find that the data is most accurately reproduced by a dominant SSAS flow with a maximal velocity at the terminator of similar to 200 m/s, displaying large diurnal and latitudinal asymmetries, combined with an equatorial RSZ wind of 70-100 m/s. Overall, this is indicative of a wind-field structure consistent with but much more complex than the usual representation of the mesospheric dynamics.
DOI 10.1051/0004-6361/201118451
ISSN 0004-6361