Collaborative Research: NSWP--Investigation of Global E-region Conductivities Relevant to the Seeding and Variability of Equatorial Spread F Using Measurements from COSMIC

低纬度恶劣空间天气的典型特征是赤道扩散F（ESF）现象，这是储存的重力能的爆炸性释放，通常发生在日落后时期。 ESF事件的发生和严重程度取决于当地赤道电离层的状况，以及通过适当磁通管内的耦合与其电接触的等离子体（即离赤道E区）的状况。在强 ESF 事件期间形成的湍流等离子体的对流羽流会降低从高频到 L 波段的通信，并且随着羽流随背景等离子体漂移而持续数小时。当前的一个主要兴趣领域涉及驱动 ESF 日常变化的因果机制。 ESF 与反转前增强（PRE）强度的变化有着令人信服的联系，PRE 是日落后时期垂直漂移速度的增加，将赤道等离子体驱动到更高的高度，那里的条件更有利于不稳定。 该项目重点关注 E 区域密度的全球测量，并将其应用于了解 ESF 的日常和长期变化。全球测量将来自 COSMIC（气象、电离层和气候星座观测系统）卫星上的仪器，并将包括总电子含量 (TEC) 的高分辨率全球定位系统掩星测量、与综合电离层电子密度相关的紫外线光度计测量以及沿卫星轨道的三波段 TEC 测量。将使用断层扫描反演和数据同化技术结合测量结果来估计电子密度的二维分布，包括 E 区域密度的水平等离子体密度梯度。将使用阿雷西博和吉卡马卡雷达的地面实况测量来验证结果并量化误差和分辨率。 该项目更广泛的影响之一在于将组装的 E 区域密度数据库，该数据库可能对全球同化模型有用，并且对于再现赤道电离层变化可能很重要，特别是在预测方面。 一名研究生以及一名新的年轻研究者将参与该项目，这是他作为首席研究员的第一个提案。

Low-latitude severe space weather is typified by the phenomenon of equatorial spread F (ESF), which is an explosive release of stored gravitational energy, usually occurring in the post-sunset period. The occurrence and severity of an ESF event depends on the condition of the local equatorial ionosphere, as well as that of the plasma in electrical contact with it (namely, the off-equatorial E region) through coupling within the appropriate magnetic flux tube. Convective plumes of turbulent plasma that develop during strong ESF events can degrade communications from high frequencies to the L-band and can last for several hours as the plumes drift with the background plasma. A major current area of interest relates to the causal mechanisms that drive the day-to-day variability of ESF. ESF has been convincingly linked to variations in the strength of the pre-reversal enhancement (PRE), which is an increase in the vertical drift velocity during the post-sunset period that drives equatorial plasma to higher altitudes where conditions are more conducive to instability. This project focuses on global measurements of E-region densities and applies them to understand the day-to-day and longer-term variability of ESF. The global measurements will come from instruments onboard the COSMIC (Constellation Observing System for Meteorology, Ionosphere, and Climate) satellites and will include high-resolution Global Positioning System occultation measurements of the total electron content (TEC), ultra-violet photometer measurements related to the integrated ionospheric electron density, and tri-band TEC measurements along the trajectory of the satellite. The measurements will be combined using tomographic inversion and data assimilative techniques to estimate the two-dimensional distribution of electron density, including the horizontal plasma density gradients of the E region densities. Results will be validated and errors and resolutions quantified using ground-truth measurements from the Arecibo and Jicamarca radars. One of the project's broader impacts lies in the database of E region densities that will be assembled which could be useful for global assimilation models and perhaps important in reproducing equatorial ionospheric variability, particularly in terms of prediction. A graduate student will be involved in the projectas well as a new young investigator for whom this is the first proposal as principal investigator.