Global Modeling of Plasma Plumes in the Equatorial Upper Atmosphere

赤道上层大气的电离部分每天表现出显著的变化。这种日常变化的一个重要来源是等离子体羽流，它们包含复杂的内部结构，人们对其知之甚少，这种内部结构统称为赤道扩散F （ESF）。ESF是一个复杂的现象，涉及范围广泛，从数十公里大小的赤道等离子体气泡到米尺度的等离子体密度不规则。最近使用ESF观测和数值模拟的结果表明，仅考虑等离子体（电离层）的条件很难预测ESF，其中一个原因可能是中性气体（热层）的不同条件。此外，不同高度层之间的垂直耦合在不同尺度等离子体结构的形成中可能是重要的，并且先前已经提出与大气沉积相关的金属离子可能间接导致ESF。本研究的目的是研究热层动力学和金属离子作为ESF的可能原因。全球电离层模式SAMI3 （SAMI3也是电离层的一个模式）将得到进一步发展，并由各种热层动力学模式加以补充。这项工作将包括：(1)通过运行SAMI3的高分辨率版本，在各种热层模型给出的不同热层条件下研究ESF的日常变化；(2)SAMI3模拟金属离子（Fe+和Mg+）通过改变日落后电离层的电导率对ESF的发生和演变的影响。(3) SAMI3的进一步改进，包括实现四阶部分供体细胞运输方案和嵌套网格技术，以实现足够高的分辨率，而不会造成计算上的限制。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The ionized portion of the equatorial upper atmosphere exhibits significant variability from one day to the next. One important source of this day-to-day variability are plumes of plasma that contain complex - and poorly understood - internal structure that is collectively known as equatorial spread F (ESF). ESF is a complex phenomenon that involves a wide range of scales from equatorial plasma bubbles of tens of km in size to meter-scale irregularities in the plasma density. Recent results using ESF observations and numerical simulations suggested that ESF is difficult to predict by considering condition of the plasma (ionosphere) alone and that one reason may be different conditions in the neutral gas (thermosphere). In addition, vertical coupling between different altitudinal layers can be important in formation of plasma structures at various scales, and it has been previously suggested that metallic ions associated with meteoric deposition may be indirectly responsible for ESF. The goal of this research is to study thermospheric dynamics and metallic ions as possible causes of ESF. The global ionospheric model SAMI3 (Sami3 is Also a Model of the Ionosphere) will be further developed and complemented by a variety of models of thermospheric dynamics. The work will involve (1) study of day-to-day variability of ESF by running the high-resolution version of SAMI3 for different thermospheric conditions as given by a variety of thermosphere models, (2) SAMI3 simulations of the effect of metallic ions (Fe+ and Mg+) on the onset and evolution of ESF through changing conductivity in the post-sunset ionosphere, and (3) further improvements in SAMI3 including implementing the 4th order partial donor cell transport scheme and the nested grid technique to achieve sufficiently high resolution without being computationally prohibitive.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.