Abstract

Observations of vibrationally excited hydroxyl (OH*) emissions are widely used to obtain information about the dynamics and composition of the atmosphere. We present some analytical approximations for the characteristics of the hydroxyl layer in the Martian atmosphere such as OH* concentration at the maximum and height of the maximum, as well as relations for estimating the influence of various factors on the OH* layer in night conditions. These characteristics depend on the temperature of the environment, concentration of atomic oxygen, and their vertical gradients. The relations are applied to the results of numerical modeling using the global atmospheric circulation model for prediction of seasonal behavior of the hydroxyl layer on Mars. Annual and intra-annual variations in the concentration of excited hydroxyl and layer height from the modeling data have both some similarities with those of the Earth and significant differences. The concentration and height maximum in the equatorial, northern and southern midlatitudes vary depending on the season; the maximum concentration and the minimum height fall on the first half of the year. Model calculations confirmed the presence of the peak OH* concentration at polar latitudes in winter at an altitude of approximately 50 km with the volume emission densities of 2.1, 1.4, and 0.6 × 10⁴ photons cm^–3 s^–1 for vibrational level transitions 1–0, 2–1, and 2–0, respectively. The relations obtained may be used for the analysis of measurements and interpretation of their variations.

中文翻译：

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火星夜间羟基特征及年内变化的解析近似

摘要

对振动激发的羟基 (OH*) 排放的观测被广泛用于获取有关大气动力学和成分的信息。我们提出了火星大气中羟基层特征的一些解析近似值，例如最大值处的 OH* 浓度和最大值的高度，以及用于估计夜间条件下各种因素对 OH* 层影响的关系。这些特性取决于环境温度、原子氧浓度及其垂直梯度。这些关系应用于使用全球大气环流模型预测火星上羟基层季节性行为的数值模拟结果。模拟数据中激发羟基浓度和层高的年内和年内变化与地球既有相似之处，也有显着差异。赤道、北部和南部中纬度地区的浓度和高度最大值随季节变化；最大浓度和最小高度落在上半年。模型计算证实，冬季极地纬度地区存在峰值 OH* 浓度，海拔高度约为 50 公里，体积排放密度分别为 2.1、1.4 和 0.6 × 10 最大浓度和最小高度落在上半年。模型计算证实，冬季极地纬度地区存在峰值 OH* 浓度，海拔高度约为 50 公里，体积排放密度分别为 2.1、1.4 和 0.6 × 10 最大浓度和最小高度落在上半年。模型计算证实，冬季极地纬度地区存在峰值 OH* 浓度，海拔高度约为 50 公里，体积排放密度分别为 2.1、1.4 和 0.6 × 10^{4 个}光子 cm ^–3 s ^–1分别用于振动能级跃迁 1–0、2–1 和 2–0。获得的关系可用于分析测量和解释它们的变化。