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

在流星雨期间，许多流星痕迹都是肉眼可以看到的。进入地球环境的外星粒子导致了这些痕迹，并在大气层的上层沉积了不同类型的金属/离子。虽然大多数这些颗粒的质量只有一克的一小部分，但它们的总日沉积速率是以数千吨为单位测量的。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轨迹，电子密度显著增加。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，超过几千开尔文。这个项目通过研究这些小径中温度松弛所涉及的物理过程，促进了科学的进一步进步。这些研究预计不仅适用于流星轨迹，也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运行的。在较低的电离层高度，这项研究可能带来关于闪电刺激的瞬变发光事件所涉及的等离子体不均匀的更多知识。研究生将在该计划下得到支持和培训。这项多学科的研究是由国家自然科学基金会的等离子体物理项目共同资助的。这项创新性的研究旨在开发使用等离子体流体方程和蒙特卡罗动力学模型的理论框架。这项工作是在早期关于放电和瞬变发光事件(TLEs)的研究的基础上发展起来的，该研究已经成功地用于电晕和瞬变发光事件的建模。这项研究的主要目标之一是获得有关流星轨迹中电子温度松弛的新知识，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，数值模拟和模拟工作将有助于：(A)描述随高度变化的流星轨迹中的电子加热和冷却速率；(B)了解流星轨迹等离子体在不同地磁场条件下的演化。这对现有的利用流星回波来推断高层大气温度和风的遥感技术有影响。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.