Ionospheric processes

经过几十年的研究，我们对电离层的基本认识现在有了坚实的基础。然而，随着仪器能力的不断进步，一些旧的主题需要重新审视，更不用说新的数据集经常会揭示出有趣的惊喜，这带来了新的挑战。这种状态的基本原因是电离层等离子体和上层大气/热层是由稀薄的气体构成的，经常受到强烈的偏离平衡的影响，无论是通过电场和电流，还是电场、温度或密度的大空间变化。这通常会产生湍流，如果要适当地量化粒子、动量和能量在系统中的传输，湍流的起源和演变都需要了解。我使用先进雷达系统、火箭和卫星的观测来查询介质。从这个起点开始，我仔细研究了电流的产生，中性大气和电离层的加热以及它们通过产生大块运动和不稳定性的后果，特别是在等离子体成分中。我的长期目标是深入了解与这些大规模偏离平衡相关的过程。这是一个具有挑战性的目标，因为许多现象是不可预测的（有许多反馈和非线性机制涉及）。我的学生和合作者要追求的具体短期目标是：(1)大马赫数条件下离子速度分布的新研究。鉴于现代雷达和卫星数据，这个问题应该重新审查；(2)利用最新数据集的新见解，对电离层下层和中层上层等离子体不稳定性提出了新的线性和非线性理论；(3)利用加拿大极帽深处的新雷达系统和加拿大卫星项目，对电离层中的等离子体尖峰进行仔细的调查，这是太阳风等离子体与地球等离子体连接的区域的足迹。该地区大气加热的来源及其响应尚不清楚；(4)研究高纬度地区对太阳风输入的各种响应。这包括在高层大气中所谓的电离斑块的产生和传播，以及由太阳风磁场和动压的变化触发磁亚暴和风暴的程度；(5)研究低纬度地区的电动力学，既与大的太阳风扰动有关，也与更安静的条件有关，这为整个电离层增加了一个有趣的视角；(6)研究高频无线电波在各种条件下的传播，以便更好地定位高频雷达回波，监测大尺度电离层结构。

After several decades of studies our basic understanding of the ionosphere now rests on solid foundations. Nevertheless, with the constant progress in instrumental capabilities some old topics need to be revisited, not to mention that the new datasets can often reveal interesting surprises, which present new challenges. The basic reason for this state of affair is that the ionospheric plasma and the upper atmosphere/thermosphere are made of rarefied gases and often subject to strong departures from equilibrium, be it through electric field and currents, or large spatial variations in electric fields, temperatures or densities. This produces turbulence more often than not, the origin and evolution of which both need to be understood if the transport of particles momentum and energy through the system is to be properly quantified. I use observations from advanced radar systems, rockets and satellites to query the medium. From this starting point I carefully study the generation of electrical currents, the heating of both the neutral atmosphere and the ionosphere and their consequences through the generation of bulk motions and instabilities, particularly in the plasma component. My long term objective is to gain a deep understanding of the processes associated with these large departures from equilibrium. This is a challenging goal, as many of the phenomena are unpredictable (there are lots of feedback and nonlinear mechanisms involved). Specific short term objectives to be pursued with my students and collaborators are: (1) a renewed study of ion velocity distributions under large Mach number conditions. This subject is due for renewed scrutiny in view of modern radar and satellite data; (2) new linear and nonlinear theories of plasma instabilities in the lower ionosphere and in the upper mesosphere, using new insights from recent datasets; (3) using new radar systems deep in the Canadian polar cap, and Canadian satellite projects to produce a careful investigation of the plasma cusp in the ionosphere, which is the footprint of the region where the solar wind plasma becomes connected with the earth plasma. The origin of atmospheric heating in that region and the response are not well understood; (4) investigating the various responses of the high latitudes to solar wind input. This includes the production and propagation of so-called patches of ionization in the upper atmosphere, and the degree to which magnetic substorms and storms are triggered by changes in the solar wind magnetic field and dynamic pressure; (5) investigating the electrodynamics of low latitude regions both in relation to large solar wind perturbations and for much quieter conditions, which adds an interesting perspective on the whole ionosphere; (6) the study HF radio wave propagation under various conditions will also be scrutinized in order to better locate HF radar echoes, and monitor large scale ionospheric structures.