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: 2017
• 资助国家: 加拿大
• 起止时间: 2017-01-01 至 2018-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=633488
• 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）等离子体的重要来源。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，(b)确定和量化这些流出对磁层-电离层-热层（MIT）的影响。离子流出种群可分为热流和超热流两类。与先前的理论预期相反，在地球引力存在的情况下，在热能“轻离子极地风”中发现了“重”氧离子的显著通量，高于其预期的峰值高度，而以前“隐藏”的冷氢离子（由于航天器充电）最近在遥远的磁层中被发现。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，并突出了我们在不同外流及其相互联系方面的知识的重要空白。拟议研究项目的短期目标是通过调查(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)热离子加热或加速的来源机制，以及(c)离子中性碰撞对顶层极电离层（300-1000公里）等离子体流出的影响，来填补若干具体知识空白。(d)对流电场在不同外流种输运和混合中的作用以及(e)它们在高海拔磁层（bbb10万km）中的命运。我们计划招收4名研究生（2名硕士和2名博士）和2名博士后，进行数据分析和建模研究项目，研究内容包括：(1)IMF对日侧热流出和极性离子组成分布的影响，(2)f区和上层高度风暴时间原子氮和分子离子加速，(3)离子中性碰撞对热极风和极光体流的影响以及这些影响对太阳周期的依赖。(4)离子对流在高海拔等离子体混合中的作用；(5)低能离子在高海拔的离心离子加速。数据分析项目将需要对CASSIOPE增强型极流探头（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，并被送入325 × 1500公里的极地轨道。2013年10月下旬，8台仪器相继完成调试，开始科学运行。建模项目将包括使用最近开发的数值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层电离层离子流出方面产生重要的科学首次：包括imf驱动的黎明-黄昏流出不对称性的成分观测；上层电离层分子离子加速和由此产生的氧/氮地球日冕；太阳自转期间太阳流出量的变化；新生极风中H+和O+离子共存；和“部分”被引力捕获的氧离子分别能够达到离心加速度高度。这项研究将提高我们对MIT耦合的认识，并实现我们的长期目标，即揭示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。