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

中性原子氧是地球高层大气中的关键物种，它在约200-700公里的热层组成中占据主导地位。了解其密度[O]对于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描述大气对空间天气或气候变化等驱动因素的动态反应是必要的。该项目旨在开发一种新的基于非相干散射雷达(ISR)数据和符合光发射观测的[O]估计技术。这项新技术将在550-850公里的高度范围内提供氧密度和温度估计。它基于O和H而不是O和O耦合来估计[O]，从而避免了过去困扰传统地面技术的与O-O碰撞截面不确定性相关的困难。这是由于阿雷西博最近为上层电离层开发的新的非相干散射多离子拟合技术。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，以汇编中纬度[O]的气候学和热层的温度变化。促进阿雷西博光学探测器灵敏度和双波束雷达能力提高的新措施将用于将中性密度反演的高度范围向下扩展到较低的高度。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碰撞频率的理论估计和经验估计之间的差异的量度。目前对这一因子的估计存在很大的差异，这是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广泛的其他大气研究的实用性。此外，该项目包括为学生提供研究机会，并将有助于促进一位年轻、成功的女科学家的独立研究生涯。

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.