[P-PS02] Recent advances of Venus science and coming decades

[PPS02-16] Identification and characterization of quiescent cloud region "CALM" in the Akatsuki and Venus Express data

*佐藤 毅彦^1,2、Vun Choon Wei^3,2、堀之内 武⁴、Kevin McGouldrick⁵、佐藤 隆雄⁶ (1.宇宙航空研究開発機構・宇宙科学研究所、2.総合研究大学院大学・宇宙科学専攻、3.ZMP株式会社、4.北海道大学、5.コロラド大学ボルダー校、6.北海道情報大学)

キーワード：雲、微物理、硫酸、あかつき、ビーナス・エクスプレス

"CALM" was identified in the Akatsuki IR2 data acquired during Orbits 24 and 25 (August 2016) once data (in 2.26- and 1.735-um filters) were plotted in a special coordinates: the horizontal axis is logarithm of radiance at 2.26 um while vertical axis (basically logarithm of radiance at 1.735 um) has been sheared such that the curve corresponding to varying amount of Mode 3 particles becomes almost level (M3L = Mode 3 Leveled). CALM appears as a concentration of data points in this correlation plot (Clouds Aligned Linearly in M3L coordinates) and is interpreted as relatively quiescent region in which aerosol sizes are determined by equilibrium. Because IR2 stopped working in December 2016, the available data set is limited. To identify more CALM-like regions and to characterize them, we have examined the data acquired by VIRTIS-M onboard Venus Express. Examples of CALM-like regions in VEx/VIRTIS-M data will be presented along with physical insights obtained through comparison with Akatsuki/IR2 data.