Quantitative study of dusty plasma in the polar mesosphere

极地中间层尘埃等离子体的定量研究

• 批准号: NE/I027231/1
• 负责人: Michael Kosch
• 金额: $ 37.87万
• 依托单位: Lancaster University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2012
• 资助国家: 英国
• 起止时间: 2012 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FI027231%2F1
• 关键词: Quantitative; study; dusty; plasma; polar

Dusty plasma is a key constituent in many natural environments and is found in the atmosphere's mesosphere region between 50 and 80 km altitude. However, it remains poorly understood. Our ultimate goal is to provide a greater quantitative understanding of the dusty plasma in the polar mesosphere, the occurrence of which is undoubtedly linked to decreasing mesospheric temperatures and increasing water vapour content via increased methane concentration, and therefore a direct consequence of climate change and at least partly human activity. Specifically, we aim to answer several key questions concerning the mesopause region, including: How much dust is there relative to the plasma density? What is the dust particle size distribution? How much charge does the dust accumulate as a function of plasma temperature? What is the dust density altitude dependence, if any, given that the dust size should sort itself out under gravity according to its buoyancy? Due to the disintegration of meteors, dust occurs naturally in the upper atmosphere with a typical size of ~1-50 nm. At high-latitudes, upward circulation of the atmosphere in the summer hemisphere under the action of atmospheric gravity waves causes extreme cooling in the mesopause region down to ~150K or less, typically minimising around 80-90 km altitude. At these low temperatures, any water vapour present freezes out onto the dust and reduces the mobility of the free electrons. In addition, the ice coated meteoric dust particles accumulate negative charge from the surrounding plasma. The remaining free low-mobility electrons are electrostatically trapped by the quasi-static heavy dust particles. The electrostatically driven dust and free electron spacing causes reflection of radar waves, i.e. the so-called Polar Mesospheric Summer Echoes (PMSE) phenomenon. PMSE are easily detected by radars, such as the EISCAT facility in northern Norway, as powerful echoes. Noctilucent clouds (NLC) are the visual equivalent of PMSE and are caused by scattering of sunlight around sunset by the larger dust particles, which occur below the PMSE layer. Both phenomena are striking examples of climate change where the upper atmosphere cools as the lower atmosphere heats up. In addition, Polar Mesospheric Winter Echoes (PMWE) appear at lower altitudes in the radar data, around 50-80 km in the winter hemisphere. However, much less is known about PMWE but there is increasing evidence that they are also a dusty plasma phenomenon.Heating the plasma by High Frequency (HF) radio waves increases the free electron mobility, which breaks down the plasma structuring and reduces the PMSE/PMWE radar echo amplitude. This is now done routinely at EISCAT using the Heater. The temporal evolution and recovery of the PMSE is a function of many variables, including ion and electron temperature, plasma and dust density, dust particle size and charge. By using multiple radar wavelengths whilst temporarily modifying the plasma surrounding the dust, we can uniquely determine the characteristics of the dusty plasma and answer the key questions given above. To date, a few rocket shots have provided us with only brief snapshots of the dusty plasma, none of them associated with artificial ionospheric heating. We propose to use the 4 radars present at EISCAT, along with the ionospheric Heater, to systematically determine the characteristics of the PMSE dusty plasma as a function of altitude and time. We will also determine whether the same dusty plasma theory is applicable to PMWE. In addition, we are very fortunate to be invited collaborators of the Charged Aerosol Release Experiment (CARE, USA) rocket experiment, which will provide us with the unique opportunity of generating an artificial dusty plasma over EISCAT. This control experiment will provide a definitive test for our understanding of dusty plasma.

尘埃等离子体是许多自然环境中的关键成分，存在于海拔 50 至 80 公里之间的大气中间层区域。然而，人们对它仍然知之甚少。我们的最终目标是对极地中间层的尘埃等离子体有更深入的定量了解，其发生无疑与中间层温度下降和甲烷浓度增加导致水蒸气含量增加有关，因此是气候变化和至少部分人类活动的直接后果。具体来说，我们的目标是回答有关中层顶区域的几个关键问题，包括：相对于等离子体密度，有多少尘埃？粉尘粒径分布是怎样的？作为等离子体温度的函数，灰尘会积累多少电荷？考虑到灰尘大小应根据其浮力在重力作用下自行排序，灰尘密度高度依赖性（如果有）是多少？由于流星的解体，高层大气中自然产生尘埃，其典型尺寸约为 1-50 nm。在高纬度地区，夏半球大气在大气重力波的作用下向上环流，导致中层顶区域极度降温，降至~150K或更低，通常在80-90公里高度处最小化。在如此低的温度下，任何存在的水蒸气都会冻结在灰尘上并降低自由电子的迁移率。此外，覆盖冰的流星尘埃颗粒会从周围的等离子体中积累负电荷。剩余的自由低迁移率电子被准静态重尘埃颗粒静电捕获。静电驱动的尘埃和自由电子间距导致雷达波反射，即所谓的极地中层夏季回声（PMSE）现象。 PMSE 很容易被雷达（例如挪威北部的 EISCAT 设施）检测为强大的回波。夜光云（NLC）在视觉上相当于 PMSE，是由于 PMSE 层下方出现的较大尘埃颗粒对日落周围的阳光进行散射而引起的。这两种现象都是气候变化的引人注目的例子，即高层大气变冷而低层大气升温。此外，极地中层冬季回波（PMWE）出现在雷达数据中较低的高度，在冬半球大约50-80公里处。然而，人们对 PMWE 知之甚少，但越来越多的证据表明它们也是一种尘埃等离子体现象。通过高频 (HF) 无线电波加热等离子体会增加自由电子迁移率，从而破坏等离子体结构并降低 PMSE/PMWE 雷达回波幅度。现在，EISCAT 使用加热器常规地完成此操作。 PMSE 的时间演变和恢复是许多变量的函数，包括离子和电子温度、等离子体和灰尘密度、灰尘颗粒大小和电荷。通过使用多个雷达波长，同时临时改变尘埃周围的等离子体，我们可以独特地确定尘埃等离子体的特征并回答上面给出的关键问题。迄今为止，几次火箭发射只为我们提供了尘埃等离子体的简短快照，其中没有一个与人工电离层加热有关。我们建议使用 EISCAT 的 4 台雷达以及电离层加热器来系统地确定 PMSE 尘埃等离子体随高度和时间变化的特征。我们还将确定相同的尘埃等离子体理论是否适用于 PMWE。此外，我们非常幸运地受邀参与带电气溶胶释放实验（CARE，美国）火箭实验，这将为我们提供在 EISCAT 上生成人造尘埃等离子体的独特机会。这个对照实验将为我们对尘埃等离子体的理解提供一个明确的测试。

项目成果

A comparison of overshoot modelling with observations of polar mesospheric summer echoes at radar frequencies of 56 and 224 MHz

• DOI: 10.5194/angeo-33-737-2015
• 发表时间: 2015-06
• 期刊: Annales Geophysicae
• 影响因子: 1.9
• 作者: O. Havnes;H. Pinedo;C. L. Hoz;A. Senior;T. Hartquist;M. Rietveld;M. Kosch

First modulation of high-frequency polar mesospheric summer echoes by radio heating of the ionosphere

通过电离层无线电加热首次调制高频极地中层夏季回波

• DOI: 10.1002/2014gl060703
• 发表时间: 2014
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Senior A

Dusty Space Plasma Diagnosis Using the Behavior of Polar Mesospheric Summer Echoes During Electron Precipitation Events

利用电子沉淀事件期间极地中层夏季回波的行为进行尘埃空间等离子体诊断

• DOI: 10.1029/2018ja025395
• 发表时间: 2018
• 期刊: Space Physics
• 作者: Mahmoudian A

Analysis and Exploitation of Landforms for Improved Optimisation of Camera-Based Wildfire Detection Systems

• DOI: 10.1007/s10694-021-01120-2
• 发表时间: 2021-04
• 期刊: Fire Technology
• 影响因子: 3.4
• 作者: Andries M. Heyns;W. du Plessis;Kevin M. Curtin;M. Kosch;G. Hough

Ordovician-Silurian true polar wander as a mechanism for severe glaciation and mass extinction.

奥陶纪-志留纪真正的极地漂移是严重冰川作用和大规模灭绝的机制。

• DOI: 10.17159/sajs.2021/7941
• 发表时间: 2022
• 期刊: Nature communications
• 影响因子: 16.6
• 作者: Jing X