Improved Meteoroid Characterization through Laboratory Experiments, Modeling, and Ground-based Observations

一项为期四年的研究旨在调查和改进对流星体的性质与由此产生的中间层和低热层(MLT)流星光学发射和雷达特征之间的关系的了解。将建立实验室实验，通过向包含已知气体密度的实验室室内发射已知质量、速度和成分的投射物来模拟地球大气层对流星的烧蚀。所发现的模拟流星的发光亮度与所使用的射弹质量之间的观测关系，将有助于使用地面雷达和光学流星测量来确定单个流星体的质量，其准确度大大提高。这一结果将量化物体流入地球大气层的总流星数量。这项研究将通过科罗拉多大学等离子体、大气和宇宙尘埃(IMPACT)模拟研究所的实验进行，目标是在明确定义的实验室条件下再现烧蚀过程。然后，这些实验结果将应用于从雷达和光学技术获得的流星观测数据，以估计单个流星事件的质量，并验证实验和模拟结果。该奖项将进一步支持博尔德州立大学攻读博士学位的研究生的教育和培训。此外，本科生将通过CU Boulder的发现学习学徒计划(DLAP)参与该计划。DLAP计划为CU本科生提供实践研究体验，并支付报酬，最终形成最终研究报告，并在该计划中向教职员工和研究生发表演讲。最后，这项研究的结果将被整合到2018年秋季开始的名为《太空：环境与影响》的新本科课程中。这门课程是在全校范围内向所有专业的学生开放的“太空辅修”课程的赞助下开发的；因此，这门课程将惠及理工科以外的学生。流星是空间环境的关键组成部分，因此这项研究将作为一个关键主题来强调近地空间环境令人着迷的复杂性。研究人员计划在这个系列中包括关于模拟流星工作的讲座。流星体进入地球大气层的速度在10到70公里/S之间，质量从飞克(Fg)到克或更大；然而，流星体的总质量流量仍然不确定，估计范围跨越两个数量级。流星体的消融是高层大气金属层形成的主要原因，包括铁原子(Fe)、镁原子(Mg)、钙原子(Ca)、钾原子(K)和钠原子(Na)，它们的峰值都在85-95公里高度范围内。这些金属层导致了各种大气现象，包括夜光云颗粒的成核，生物有效铁对海洋的肥沃，以及平流层气溶胶含量与臭氧化学之间的关系。此外，毫克或更大的流星对绕地球运行的航天器构成风险，有可能造成物理或电气损害。对总质量通量的准确评估对于提高对这些区域的了解至关重要。总质量通量误差主要是由于无法确定单独观测到的粒子的质量造成的。导致流星体质量估计不佳的主要不确定性来源是将质量映射到可观测数据的参数的不确定性，例如光学发射和雷达散射截面。这些参数是发光效率和电离几率。该项目可能会提供迄今为止对一系列速度和代表流星体的不同材料的最佳测量结果。该奖项的首要科学目标是解决理解MLT大气学的一个简单但关键的问题：从太空进入我们大气层的总质量通量是多少？在实验室制造人造流星的能力提供了一个很好的机会，以一种非专家可以理解的方式与社区互动。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。

A four-year research designs to investigate and improve the understanding of the relationship between the properties of a meteoroid and the resulting mesosphere and lower thermosphere (MLT) meteor optical emission and radar signatures. Laboratory experiments would be set up to simulate the ablation of meteors by the Earth's atmosphere by firing projectiles with known mass, speed, and composition into a laboratory chamber containing a known density of gas. The observed relationship found between the luminous brightness of the simulated meteor with the mass of the projectile used would help enable the use of ground-based radar and optical meteor measurements to determine the masses of individual meteoroids with considerably improved accuracy. This result would then quantify the estimate of the total meteor influx of objects into the Earth's atmosphere. This research would be done through experiments at the University of Colorado's Institute for Modeling Plasma, Atmospheres and Cosmic dusT (IMPACT) facility in which the goal would be the recreation of the ablation process in well-defined laboratory conditions. These experimental results would then be applied to meteor observational data derived from both radar and optical techniques, in order to estimate masses of individual meteor events and to validate experimental and modeling results. This award would further support the education and training of a graduate student pursuing a Ph.D at CU Boulder. In addition, undergraduate students would be involved in the program through the Discovery Learning Apprenticeship Program (DLAP) at CU Boulder. The DLAP program provides CU undergraduates a hands-on research experience, with pay, culminating in a final research report and a presentation to faculty and graduate students in the program. Finally, results from the research would be integrated into a new undergraduate course entitled 'Space: Environment and Effects', to begin in Fall 2018. This course is being developed under the auspices of a campus wide "Space Minor" open to students in all majors; as such, this curriculum would reach students beyond science and engineering. Meteors make up a key component of the space environment, and so this research would be used as a key topic to underline the fascinating complexity of the near-earth space environment. The researcher plans to include lectures on simulated meteor work in this series.Meteoroids enter the Earth's atmosphere with velocities between 10 and 70 km/s and masses from femtograms (fg) up to grams or larger; however, the total mass flux of meteoroids remains uncertain, with a range of estimates spanning two orders of magnitude. The ablation of meteoroids are suggested to be responsible for the creation of metal layers of the upper atmosphere, including atomic iron (Fe), magnesium (Mg), calcium (Ca), potassium (K), and sodium (Na) layers that all peak within the range of 85-95 km altitude. These metal layers lead into a variety of aeronomical phenomena, including the nucleation of noctilucent cloud particles, ocean fertilization with bio-available Fe, and creating a relationship between stratospheric aerosol content and O3 chemistry. Moreover, meteors of milligram size and larger pose a risk to spacecraft orbiting the Earth, with the potential to cause physical or electrical damage. Accurate assessment of the total mass flux is critical to improving the understanding of each of these areas. The total mass flux error is primarily caused by the inability to determine masses of individually observed particles. The major sources of uncertainty that lead to poor estimates of meteoroid masses are uncertainty in the parameters which map the mass to observables, such as optical emissions and radar cross section. These parameters are the luminous efficiency and the ionization probability. The project would possibly provide the best measurements to date for a range of velocities and for different materials representative of meteoroids. The foremost science objective in this award addresses a simple yet critical problem in understanding MLT aeronomy: what is the total mass flux entering our atmosphere from space? The ability to create artificial meteors in the lab provides a great opportunity to engage with the community in a way that non-specialists can understand.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.