[PPS05-P04] Stationary wavy features and Banded structures at Venusian cloud top extracted by averaging multiple LIR images
Keywords:Stationary gravity waves, Venus, Akatsuki
In the previous studies using LIR data, only planetary-scale stationary features have been investigated. On the other hand, Peralta et al. (2017) analyzed the data taken by VIRTIS onboard Venus Express, and reported the existence of many small-scale stationary features; however, VIRTIS can observe the night side only, and the observations were confined to the high latitude of the southern hemisphere because of the geometry of the orbit. Therefore, we intend to investigate with a new analysis method the topographical and local time dependency of small-scale, weak stationary features by using LIR data, which can observe all latitude regions at any local time. Though the S/N ratio of LIR is lower than VIRTIS, averaging of multiple images can suppress noises and at the same time emphasize stationary patterns. By using this method, small-scale, stationary wave trains were newly found above relatively-low topographic rises with altitudes of 1-3 km. In addition to stationary features, zonally-elongated banded structures were also found in averaged LIR images. Such structures have once been detected in LIR images taken during Akatsuki’s Venus flyby in 2010 (Taguchi et al., 2012); the new analysis confirmed that banded structures are ubiquitous at the cloud top. The orientations of the banded structures are different from those of dark streaks found in ultraviolet images.