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: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=708306
• 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 x 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.

离子流出在地球电离层与其热层和磁层的耦合中发挥着重要作用：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。拟议研究的总体长期目标是（a）揭示不同离子流出的潜在等离子体加速和传输过程，以及（b）确定和量化这些流出对磁层-电离层-热层（MIT）的影响）。 离子流出群体可以分为两类：热离子和超热离子。与早期的理论预期相反，在地球重力存在的情况下，在预期峰值高度之上的热能“轻离子极风”中发现了大量“重”氧离子通量，以及先前“隐藏”的冷氢离子（由于最近在遥远的磁层中发现了航天器充电）。这些观测结果强调了热流出对磁层动力学的重要直接影响，并强调了我们对不同流出及其相互联系的认识中的重要差距。 拟议研究项目的短期目标是通过研究（a）行星际磁场（IMF）和地磁活动对等离子体流出的作用或影响，（b）热离子加热的源机制来填补几个特定的​​知识空白或加速度；(c) 离子-中性碰撞对极地电离层（300-1000 公里）等离子体流出的影响，以及 (d) 对流电场在离子传输和混合中的作用不同的外流物种以及 (e) 它们在高空磁层（>10,000 km）中的命运。 我们计划聘请四名研究生（2名硕士和2名博士）和两名博士后参与数据分析和建模研究项目，研究项目涉及（1）IMF对白天热流出和极性离子成分分布的影响，（2）风暴时原子F 区和上部高度的氮和分子离子加速，(3) 离子中性碰撞对热极风和极光整体流的影响以及这些影响的太阳周期依赖性，(4) 等离子体中离子对流的作用(5)高海拔低能离子的离心离子加速。 数据分析项目将对 CASSIOPE 增强型极地流出探测器 (e-POP) 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，进入325×1500公里的极地轨道。 2013年10月下旬，八台仪器相继完成调试，开始科学运行。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。 就预期意义而言，每个项目都可能在上部电离层离子流出方面产生重要的科学成果：包括IMF驱动的黎明-黄昏流出不对称的成分观测；分子离子加速以及由此产生的顶部电离层中的氧/氮地冕；太阳自转期间流出量的太阳变化；新生极风中共存的 H+ 和 O+ 离子；和“部分”重力捕获的氧离子，分别能够达到离心加速高度。这项研究将增进我们在 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。