Estimation of Thermospheric Oxygen Density and Temperature From Combined Optical and Radar Measurements

中性原子氧O是地球高层大气中的关键物质，在200-700千米之间的热层组成中占主导地位。航天器在近地轨道上运行、了解热层和电离层之间的耦合以及表征大气对空间天气或气候变化等驱动因素的动态响应都需要了解其密度[O]。本项目旨在开发一种基于非相干散射雷达（ISR）数据和同步光学发射观测的[O]估计新技术。新技术将提供海拔550-850公里范围内的O密度和温度估计。它将[O]估算基于O和H+，而不是O和O+的耦合，从而避免了O+-O碰撞截面的不确定性所带来的困难，这些困难一直困扰着过去传统的地面技术。这是由最近在阿雷西博为上层电离层开发的新的非相干散射多离子拟合技术实现的。这项技术将应用于阿雷西博天文台近20年的光学和雷达数据，以编制中纬度气候学[O]和热层温度变化。在阿雷西博，新的测量方法有助于提高光学探测器的灵敏度和双波束雷达的能力，将用于将中性密度逆温的高度范围扩展到更低的高度。这将允许对所谓的“伯恩赛德因子”F进行独立的、大大改进的估计，F是对O+-O碰撞频率的理论和经验估计之间差异的度量。对这一因素的现有估计存在巨大差异，这构成了热层化学中一个长期存在的难题。该项目的更广泛影响包括这项新技术对其他广泛的大气研究的有用性。此外，该项目还为学生提供了研究机会，并将有助于进一步发展年轻、成功的女科学家的独立研究事业。

Neutral atomic oxygen, O, is a key species in Earth's upper atmosphere, where it dominates thermospheric composition between ~200-700 km. Knowledge of its density, [O], is required for spacecraft operations in low earth orbit, for understanding the coupling between the thermosphere and ionosphere, and for characterizing the dynamic atmospheric response to drivers such as space weather or climate change. This project is to develop a new technique for [O] estimation based on Incoherent Scatter Radar (ISR) data and coincident optical emission observations. The new technique will provide both O density and temperature estimates over the altitude range 550-850 km. It bases the [O] estimation on O and H+ rather than O and O+ coupling, thereby avoiding the difficulties associated with uncertainties in the O+-O collisional cross section that have plagued traditional ground-based techniques in the past. This is made possible by new incoherent scatter multi-ion fitting techniques recently developed at Arecibo for the topside ionosphere. The technique will be applied to nearly 20 years of optical and radar data available from the Arecibo observatory to compile a climatology of mid-latitude [O] and temperature variations for the thermosphere. New measurements facilitating improvements in optical detector sensitivity and dual-beam radar capability at Arecibo will be used to extend the altitude range of the neutral density inversions down to lower altitudes. This will allow for an independent, much improved estimation of the so-called "Burnside factor", F, a measure of the discrepancy between theoretical and empirical estimates for the O+-O collision frequency. The large discrepancies in existing estimates of this factor constitute a long-standing puzzle in thermosphere chemistry. Broader impacts of this project include the usefulness of this new technique for a wide range of other atmospheric studies. In addition, the project includes research opportunities for students and would help further the independent research career of a young, successful female scientist.