CEDAR: Modeling of Initial Temperature Relaxation and Expansion of Meteor Trails

在流星雨期间，许多流星痕迹是肉眼可见的。进入地球环境的外星粒子会产生这些痕迹，并在大气层的上层沉积不同种类的金属/离子。虽然这些颗粒中的大多数质量只有一克的一小部分，但它们的总体每日沉积速率以数千吨计算。当流星体进入地球大气层时，它们形成了大约圆柱形的等离子体轨迹，电子密度显著增强。有一个重要的光谱证据表明，流星轨迹中的等离子体温度升高，超过几千开氏度。该项目通过研究这些轨迹中温度松弛的物理过程，促进了科学的进一步发展。这些研究预计不仅适用于流星轨迹，而且适用于任何涉及衰变等离子体的物理系统。将要研究的扩散过程是在正柱直流放电中进行的。在较低的电离层高度，这项研究可能带来更多关于闪电激发瞬态发光事件中等离子体不均匀性的知识。研究生将在该项目下得到支持和培训。这项多学科研究是由美国国家科学基金会等离子体物理项目共同资助的。该创新研究旨在建立等离子体流体方程和蒙特卡罗动力学模型的理论框架。这项工作是在早期对放电的研究基础上发展起来的，该研究已成功地用于电晕和瞬态发光事件（TLEs）的建模。研究的主要目标之一是获得流星尾迹中电子温度弛豫的新知识，重点是扩散动力学。这项工作寻求有关电子中性碰撞频率、双极性扩散速率和梯度漂移等离子体不稳定性发展的信息。此外，数值模拟和建模工作将有助于：(a)流星轨迹中随海拔变化的电子加热和冷却速率表征，(b)了解不同地磁场条件下流星轨迹等离子体的演化。这对利用流星回波推断高层大气温度和风的现有遥感技术产生了影响。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。

Many meteor trails are visible to an unaided eye during shower events. Extra-terrestrial particles entering the Earth’s environment result in these trails and deposit different kind of metals/ions in the upper regions of the atmosphere. Although most of these particles have masses of a small fraction of a gram, their overall daily deposition rates are measured in thousands of tons. As the meteoroids enter the Earth’s atmosphere, they form approximately cylindrical plasma trails with considerable enhancements of electron density. There is a significant spectroscopic evidence of elevated plasma temperatures in meteor trails, exceeding several thousands of degrees kelvin. This project promotes the further progress of science by investigating the physical processes involved in temperature relaxation in these trails. These studies are expected to be applicable not only to meteor trails but any physical system involving decaying plasmas. The diffusion processes that will be studied are in operation in positive column direct current discharges. At lower ionospheric altitudes this research may bring additional knowledge about plasma inhomogeneities involved in lightning stimulated transient luminous events. A graduate student will be supported and trained under this program. This multi-disciplinary research is co-funded by the Plasma Physics program at the NSF.The innovative research aims at developing theoretical framework that employs plasma fluid equations and Monte Carlo kinetic models. The work develops from the earlier research on the electrical discharge, which has been successfully implemented for modeling of corona, and transient luminous events (TLEs). One of the primary goals of the investigation is to gain new knowledge about electron temperature relaxation in the meteor trails with a focus on diffusion dynamics. This work seeks information about the electron-neutral collision frequencies, ambipolar diffusion rates and development of gradient-drift plasma instabilities. Additionally, the numerical simulation and modeling work will facilitate: (a) electron heating and cooling rates characterization in meteor trails with altitude, (b) knowledge about the evolution of meteor trail plasma under varying geomagnetic field conditions. This has implications on the existing remote sensing techniques that employ meteor echoes for inferring temperatures and winds in the upper atmosphere.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.