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

在流星雨期间，许多流星的轨迹都是肉眼可见的。进入地球环境的外星粒子会产生这些痕迹，并在大气层的上部区域沉积存款不同种类的金属/离子。 虽然这些颗粒中的大多数质量只有一克的一小部分，但它们的总日沉积速率以数千吨计。当流星体进入地球大气层时，它们形成了近似圆柱形的等离子体尾迹，电子密度大大增强。 有一个重要的光谱证据表明，流星尾迹中的等离子体温度升高，超过几千度开尔文。 该项目通过研究这些路径中温度弛豫所涉及的物理过程来促进科学的进一步进步。预计这些研究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。将研究的扩散过程是在操作中的正柱直流放电。在较低的电离层高度，这项研究可能会带来更多的知识等离子体的不均匀性参与闪电刺激的瞬态发光事件。一名研究生将在该方案下得到支持和培训。这项多学科研究由美国国家科学基金会等离子体物理项目共同资助。这项创新研究旨在开发采用等离子体流体方程和蒙特卡罗动力学模型的理论框架。这项工作是从早期的放电研究发展起来的，已经成功地实现了电晕和瞬态发光事件（TLEs）的建模。调查的主要目标之一是获得新的知识，电子温度弛豫的流星轨迹，重点扩散动力学。这项工作寻求有关电子中性碰撞频率，双极扩散率和发展的梯度漂移等离子体不稳定性的信息。此外，数值模拟和建模工作将有助于：（a）电子加热和冷却率的流星轨迹与高度的特性，（B）在不同的地磁场条件下流星轨迹等离子体的演变知识。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NSF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.