Modeling VIRTIS/VEX O₂(a1∆g) nightglow profiles affected by the propagation of gravity waves in the Venus upper mesosphere

Abstract

In this work we describe a model of the perturbation of the O 2 (a 1 Δ g ) nightglow limb profiles by the action of gravity waves (GWs) propagating in the Venus' upper atmosphere. Data have been acquired by the Visible and InfraRed Thermal Imaging Spectrometer (VIRTIS) on board the European Space Agency mission Venus Express (VEX). The high variability observed in the shape of the O 2 (a 1 Δ g ) nightglow limb profiles between 80 and 120 km, often characterized by the presence of a double peak, suggests the occurrence of GWs at the considered altitudes. In order to model and derive the GWs properties, we apply to Venus a well-known theory used to study terrestrial density fluctuations induced by the GWs propagation. The retrieved vertical wavelengths and amplitudes of the waves at the O 2 (a 1 Δ g ) layer altitude (~100 km) are of the order of 7-16 km and 3-14% respectively, complying with wave amplitude threshold for dynamical instability in the majority of the fitted cases. Temperature fluctuations would exceed 40% at higher altitudes (115-120 km) thus inducing either wave breaking or dissipation. Intrinsic horizontal phase velocities are expected to vary in the range 32 m/s and 85 m/s. GWs are detected in a wide range of latitudes from the midlatitudes up to the polar regions, and we cannot exclude existence of the sources of different nature. This study also confirms the high variability induced by the action of GW propagation in the airglow profiles of the terrestrial planets and points out the need for future missions to couple simultaneous complementary GW detection techniques in order to better constrain GW properties and understand their impact on the Venus general circulation.

Aeronomy of the Venus Upper Atmosphere

“…The VeRa Radio Science Experiment also provides wave information that is extracted from temperature fluctuations . Lastly, current efforts are focusing upon characterizing gravity waves from VIRTIS observations of O 2 IR nightglow (Altieri et al 2014).…”

Circulation of Venusian Atmosphere at 90–110 km Based on Apparent Motions of the O2 1.27 μm Nightglow From VIRTIS‐M (Venus Express) Data

“…In thermosphere (>110 km) a subsolar‐to‐antisolar (SS‐AS) circulation cell is driven by the solar heating (Sánchez‐Lavega et al, ). Thus, the dynamics in the transition region might be influenced by both of these modes (Bougher et al, ; Lellouch et al, ), as well as other mechanisms, such as gravity waves (Alexander, ; Altieri et al, ; Bertaux et al, ; Peralta et al, ; Zhang et al, ) and thermal tides (Zasova et al, ).…”

“…From limb mode observations O 2 (a 1 Δ g ) emission vertical profiles were obtained, and the mean altitude of the emission peak was found at 97.4 ± 2.5 km altitude. The double peak, observed in some cases, was interpreted after modeling (Altieri et al, 2014) as gravity waves with vertical wavelength of 10-14 km and horizontal wavelength of 100-1,000 km. The nadir measurements showed the distribution of the emission over the nightside and appearance of the local maxima at different latitudes and local time (LT), but on the averaged map, a wide spread spot of higher intensity of nightglow appeared around midnight (Piccioni et al, 2009;Shakun et al, 2010).…”

Diagnostics of internal atmospheric wave saturation and determination of their characteristics in Earth's stratosphere from radiosonde measurements

“…The original method of identifying wave events and reconstructing IGW characteristics in planetary atmospheres we developed [Gubenko et al, 2008b[Gubenko et al, , 2011[Gubenko et al, , 2016a has been widely recognized by scientific community both in Russia and abroad. It is now being successfully used to study wave processes in the atmospheres of Earth [Horinouchi, Tsuda, 2009;Xiao, Hu, 2010;Rechou et al, 2014;Sacha et al, 2014;Noersomadi, Tsuda, 2017;Zagar et al, 2017] and Venus [Altieri et al, 2014;Peralta et al, 2015]. For example, Rechou et al [2014] have shown that numerical simulation data and analysis of independent radar and probe measurements in Earth's atmosphere demonstrate high efficiency of our method and high reliability of scientific results it yields.…”