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传播F （ESF）现象，这是一种储存的重力能量的爆炸性释放，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条件，以及与之电接触的等离子体（即赤道外E区）的条件，通过在适当的磁通管内的耦合。在强烈的ESF事件中形成的湍流等离子体对流羽流可以降低从高频到l波段的通信，并且可以持续几个小时，因为羽流随着背景等离子体漂移。当前的一个主要研究领域涉及驱动ESF日常变化的因果机制。ESF与前反转增强（PRE）强度的变化有令人信服的联系，PRE是在日落后时期垂直漂移速度的增加，驱使赤道等离子体到更高的高度，那里的条件更有利于不稳定。该项目侧重于e区密度的全球测量，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，并将包括高分辨率的全球定位系统掩星测量总电子含量（TEC），紫外线光度计测量与综合电离层电子密度有关，以及沿着卫星轨迹的三波段TEC测量。测量结果将结合层析反演和数据同化技术来估计电子密度的二维分布，包括E区密度的水平等离子体密度梯度。将利用阿雷西博和吉马卡雷达的地面真值测量对结果进行验证，并对误差和分辨率进行量化。该项目的一个更广泛的影响在于即将收集的E区密度数据库，它可能对全球同化模型有用，也许对重现赤道电离层的变化很重要，特别是在预测方面。该项目将由一名研究生和一名新的年轻研究员参与，这是他首次被提议担任首席研究员。

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.