High latitude gravity waves at the Venus cloud tops as observed by the Venus Monitoring Camera on board Venus Express
High latitude gravity waves at the Venus cloud tops as observed by the Venus Monitoring Camera on board Venus Express
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DOI：
10.1016/j.icarus.2013.09.012
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发表时间：
2014-01-01
期刊：
影响因子：
3.2
通讯作者：
Svedhem, H.
中科院分区：
文献类型：
--
作者：
Piccialli, A.;Titov, D. V.;Svedhem, H.
用金星监测照相机（VMC/VEx）获得的金星北方半球的高分辨率图像可以研究云顶（类似于62-70公里高度）的小尺度动力学现象，包括波列等特征。对这些波进行了系统的视觉搜索;分析了1500多个轨道，并在300多张图像中观察到了波型。根据波形形态将VMC图像分为长、中、短和不规则波四种类型。为了表征波的类型及其可能的激发源，我们检索了波的属性，如位置（纬度和经度），当地时间，太阳天顶角，包的长度和宽度，方向，和每个波的波长。长型波表现为长而窄的直线特征，延伸超过几百公里，波长在7到17公里之间。中等类型的波表现出不规则的波前延伸超过100公里，波长范围在8-21公里。短波包的宽度为几十公里，延伸到几百公里，其特征是波长较小（3-16公里）。不规则波场似乎是波干涉的结果。这些波通常在所有VMC滤波器中被识别出来，并且大多数在高纬度（60-80 N）的冷领地区被发现，并集中在Ishtar Terra上方，这是一个大陆规模的高地，包括地球上最高的山脉带。金星快车航天器接近近心点的高速不允许测量波的相速度，因为图像对之间的时间间隔很短。由于缺乏相速度的信息，我们不能绝对肯定地确定这些波的性质。然而，通过比较VMC图像中观察到的波特征的形态和性质与以前的观测结果，可以合理地假设这里研究的波是重力波。(C)2013 Elsevier Inc. All rights reserved.
High resolution images of Venus Northern hemisphere obtained with the Venus Monitoring Camera (VMC/VEx) allow studying small-scale dynamical phenomena at the cloud tops (similar to 62-70 km altitude) including features like wave trains. A systematic visual search of these waves was performed; more than 1500 orbits were analyzed and wave patterns were observed in more than 300 images. Four types of waves were identified in VMC images on the base of their morphology: long, medium, short and irregular type waves. With the aim to characterize the wave types and their possible excitation source, we retrieved wave properties such as location (latitude and longitude), local time, solar zenith angle, packet length and width, orientation, and wavelength of each wave. The long type waves appear as long and narrow straight features extending more than a few hundreds kilometers and with wavelengths between 7 and 17 km. Medium type waves exhibit irregular wavefronts extending more than 100 km and with wavelengths in the range 8-21 km. Short wave packets have a width of several tens of kilometers and extend to few hundreds kilometers and are characterized by smaller wavelengths (3-16 km). Irregular wave fields appear to be the result of wave interference. The waves are often identified in all VMC filters and are mostly found in the cold collar region at high latitudes (60-80 N) and are concentrated above Ishtar Terra, a continental size highland that includes the highest mountain belts of the planet. The high speed of the Venus Express spacecraft close to the pericentre does not allow to measure phase speed of waves due to the short temporal interval between image pairs. The lack of information on phase velocities does not allow us to establish with absolute confidence the nature of these waves. However, by comparing the morphology and properties of the wave features observed in VMC images to those seen by previous observations it is reasonable to assume that the waves studied here are gravity waves. (C) 2013 Elsevier Inc. All rights reserved.