Thermal plasma acceleration and outflows in the Earth’s ionosphere

地球电离层中的热等离子体加速和流出

• 批准号: RGPIN-2014-06069
• 负责人: Yau, Andrew
• 金额: $ 3.93万
• 依托单位: University of Calgary
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2015
• 资助国家: 加拿大
• 起止时间: 2015-01-01 至 2016-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=588790
• 关键词: Thermal; plasma; acceleration; outflows; Earth

Ion outflows play an important role in the coupling of the Earth’s ionosphere to its thermosphere and its magnetosphere: they constitute a significant source of plasma for the magnetosphere - the region in near-Earth space dominated by the Earth’s magnetic field. The overarching long-term goal of the proposed research is (a) to unravel the underlying plasma acceleration and transport processes of the different ion outflows and (b) to determine and quantify the effects of these outflows on the magnetosphere-ionosphere-thermosphere (MIT). Ion outflow populations may be classified into two categories: thermal and suprathermal. Contrary to earlier theoretical expectations, significant fluxes of “heavy” oxygen ions were found in thermal-energy “light ion polar wind” above their expected peak altitude in the presence of the Earth’s gravity, and previously “hidden” cold hydrogen ions (due to spacecraft charging) were recently discovered in the distant magnetosphere. These observations underscore the important direct influence of thermal outflows on the dynamics of the magnetosphere, and highlight important gaps in our knowledge on the different outflows and their interconnections. The short-term objectives of the proposed research projects are to fill several specific knowledge gaps by investigating (a) the role or influence of interplanetary magnetic field (IMF) and geomagnetic activity on plasma outflows, (b) the source mechanisms for thermal ion heating or acceleration and (c) the effect of ion-neutral collisions on plasma outflow in the topside polar ionosphere (300–1000 km), and (d) the role of convection electric field in the transport and intermixing of different outflow species and (e) their fates in the high-altitude magnetosphere (>10,000 km). We plan to engage four graduate (2 Masters and 2 PhD) and two postdoctoral students in data analysis and modeling research projects on (1) the influence of the IMF on dayside thermal outflows and polar ion composition distributions, (2) storm-time atomic nitrogen and molecular ion acceleration at F-region and topside altitudes, (3) the effects of ion-neutral collisions on thermal polar wind and auroral bulk flow and the Solar Cycle dependence of these effects, (4) the role of ion convection in plasma intermixing at high altitudes, and (5) centrifugal ion acceleration of low-energy ions at high altitudes. The data analysis projects will entail detailed and statistical analyses of observation data from the CASSIOPE Enhanced Polar Outflow Probe (e-POP) and complementary data from the SuperDARN radar. CASSIOPE was launched successfully on September 29, 2013 and placed into a polar orbit of 325 × 1500 km. Science operation of its eight instruments started sequentially in late October 2013 as the respective instruments completed commissioning. The modeling projects will involve simulation of particle trajectories in time-dependent electric and magnetic fields in the magnetosphere, using recently developed numerical codes. In terms of expected significance, each project will potentially produce an important scientific first on topside ionospheric ion outflow: including composition observation of IMF-driven dawn-dusk outflow asymmetry; molecular ion acceleration and resulting oxygen/nitrogen geo-corona in the topside ionosphere; solar variability of outflow within a solar rotation; co-existing H+ and O+ ions in the nascent polar wind; and “partially” gravitationally trapped oxygen ions capable of reaching centrifugal acceleration altitude, respectively. The research will advance our knowledge in MIT coupling, and our long-term goal to unravel the underlying plasma processes of ion outflows and to determine and quantify their effects on the MIT system.

离子外流在地球电离层与热层和磁层的耦合中起着重要作用：它们构成了磁层----近地空间中由地球磁场主导的区域----的重要等离子体源。拟议研究的首要长期目标是：（a）揭示不同离子外流的基本等离子体加速和传输过程;（B）确定和量化这些外流对磁层-电离层-热层的影响。 离子流出粒子数可分为两类：热离子和超热离子。与早期的理论预期相反，在地球引力存在的情况下，在热能“轻离子极风”中发现了“重”氧离子的显著通量，高于其预期的峰值高度，并且最近在遥远的磁层中发现了先前“隐藏”的冷氢离子（由于航天器充电）。这些观测结果强调了热外流对磁层动力学的重要直接影响，并突出了我们对不同外流及其相互联系的知识中的重要空白。 拟议研究项目的短期目标是填补若干具体知识空白，调查（a）行星际磁场和地磁活动对等离子体外流的作用或影响，（B）热离子加热或加速的源机制，（c）离子中性碰撞对极区电离层顶部等离子体外流的影响（d）对流电场在不同外流物质的迁移和混合中的作用和（e）它们在高空磁层（> 10，000公里）中的命运。 我们计划聘请四名研究生（2名硕士和2名博士）和两名博士后学生在数据分析和建模研究项目（1）国际货币基金组织对昼侧热外流和极性离子成分分布的影响，（2）风暴时间原子氮和分子离子加速在F区和顶侧高度，（3）离子-中性粒子碰撞对热极风和极光体流的影响以及这些影响与太阳周期的关系;（4）离子对流在高空等离子体混合中的作用;（5）低能离子在高空的离心离子加速。 数据分析项目将需要对CASSIOPE增强型极地外流探测器的观测数据和SuperDARN雷达的补充数据进行详细的统计分析。CASSIOPE于2013年9月29日成功发射，并进入325 × 1500公里的极地轨道。随着各仪器完成调试，其八台仪器的科学运行于2013年10月下旬相继开始。建模项目将涉及使用最近开发的数字代码模拟磁层中随时间变化的电场和磁场中的粒子轨迹。 就预期的重要性而言，每个项目都有可能在电离层顶面离子外流方面创造重要的科学先例：包括对国际货币基金组织驱动的晨昏外流不对称性的成分观测;分子离子加速和在电离层顶面产生的氧/氮地晕;太阳自转中外流的太阳变化;初生极风中共存的H+和O+离子;和“部分”被重力捕获的氧离子，其分别能够达到离心加速高度。这项研究将推进我们在MIT耦合方面的知识，以及我们的长期目标，即解开离子流出的潜在等离子体过程，并确定和量化它们对MIT系统的影响。