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

低纬恶劣空间天气的典型特征是赤道扩散F(ESF)现象，这是一种储存的引力能量的爆炸性释放，通常发生在日落后。ESF事件的发生和严重程度取决于当地赤道电离层的状况，以及通过在适当的磁通管内耦合而与之电接触的等离子体(即赤道外E区)的状况。在强ESF事件期间产生的湍流等离子体对流羽流可能会使通信从高频降级到L波段，并可以持续几个小时，因为羽流与背景等离子体一起漂移。目前感兴趣的一个主要领域涉及驱动ESF日常变异性的因果机制。ESF已经令人信服地与前逆转增强(PRE)强度的变化有关，PRE是日落后期间垂直漂移速度的增加，将赤道等离子体推向更有利于不稳定条件的更高海拔。该项目侧重于E区密度的全球测量，并将其应用于了解ESF的日常和较长期的变异性。全球测量将来自COSMIC(气象学、电离层和气候星座观测系统)卫星上的仪器，并将包括高分辨率全球定位系统掩星测量总电子含量(TEC)、与电离层综合电子密度有关的紫外线光度计测量、以及沿卫星轨道的三波段TEC测量。这些测量将使用层析反演和数据同化技术相结合，以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。结果将得到验证，误差和分辨率将使用阿雷西博和基卡马卡雷达的地面实况测量进行量化。该项目的一个更广泛的影响在于将汇编的E区密度数据库，该数据库可用于全球同化模式，并可能对重现赤道电离层可变性，特别是在预测方面很重要。一名研究生将参与该项目，以及一名新的年轻调查员，这是作为首席调查员的第一个提议。

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.