Probing the Dynamic Ionosphere: A Multifaceted Approach

极光不仅仅是一个美丽的景象，它是巨大电流的可见表现，这些电流穿过近地空间，并将数十亿瓦的电力注入我们的高层大气。 极光影响着我们的大气层，甚至可能影响着我们的气候，并提供了一个充满宇宙的基本等离子体过程的全景。 它还可能对空间和地面技术构成威胁。 流行的文章甚至天文学教科书都倾向于对极光进行过于简单的解释，即太阳风中的带电粒子被地球磁场“捕获”并引导到磁极。 实际上，太阳风和极光之间的联系要复杂得多，也有趣得多。 例如，极光电子的能量被加速到太阳风能量的1000倍，这一事实无法单独用磁场来解释。 此外，最强烈的极光从磁层深处的一个来源吸引电子，而没有直接进入太阳风。 最重要的是，这种简单的解释忽略了一点，即极光基本上是电路的一部分，由快速流动的太阳风与地磁场相互作用形成的磁流体动力发电机提供动力。 该提案旨在利用加拿大在一系列前所未有的空间和地面仪器方面的领导地位所提供的丰富而及时的机会，解决与极光形成有关的关键问题，更一般地说，解决与地球电离层的来源结构和可变性有关的关键问题。 该项目最重要的是2013年11月发射的欧洲航天局Swarm卫星上的电场仪器。 这些仪器是卡尔加里大学与加拿大工业伙伴COM DEV International（现为Honeywell）和瑞典空间物理研究所合作开发的。 电场的估计来自低能量等离子体测量，包括离子流速，等离子体密度和温度。 Swarm将这些与最先进的磁场测量相结合，目前正在对电离层的电动力学行为和等离子体特性进行精确，长期，多点，极到极的调查。 虽然Swarm本身没有直接测量极光，也没有产生极光的高能电子，但我们能够通过部署在加拿大北极地区的白光全天空相机阵列单独获得这些信息，作为NASA/CSA THEMIS地面观测链的一部分，并很快通过新的TREx（过渡区探测器）多波长阵列，两者都是通过与卡尔加里大学极光成像小组的合作而实现的。

More than just a beautiful sight, the aurora is the visible manifestation of massive electric currents that thread near-Earth space and inject billions of Watts of electrical power into our upper atmosphere. The aurora affects our atmosphere and possibly our climate, and provides a ringside view of fundamental plasma processes that pervade the universe. It can also pose a threat to technology in space and on the ground. Popular articles and even astronomy textbooks tend to give an oversimplified explanation of the aurora in terms of charged particles from the solar wind “captured” by Earth's magnetic field and channeled to the magnetic poles. In reality the connection between the solar wind and the aurora is more complex, and much more interesting. For example, auroral electrons are accelerated to energies 1000 times larger than those in the solar wind, a fact that cannot be explained by a magnetic field alone. Furthermore, the most intense auroras draw electrons from a source deep in the magnetosphere, with no direct access to the solar wind. Most importantly, the simple explanation misses the point that the aurora is fundamentally part of an electric circuit, powered by a magneto-hydrodynamic dynamo formed from the interaction of the fast-flowing solar wind with the geomagnetic field. This proposal is aimed at resolving key questions pertaining to formation of the aurora, and more generally to sources structure and variability of Earth's ionosphere by taking advantage of a rich and timely opportunity made possible by Canadian leadership in an unprecedented array of space and ground-based instrumentation. Foremost for this project are the Electric Field Instruments (EFIs) on the European Space Agency's Swarm satellites, launched in November 2013. These instruments were developed at the University of Calgary in collaboration with Canadian industrial partner COM DEV International (now Honeywell) and the Swedish Institute for Space Physics. Electric field estimates are derived from low-energy plasma measurements that include ion flow velocity, plasma density, and temperature. Combining these with state-of-the-art magnetic field measurements, Swarm is currently carrying out a precision, long-term, multi-point, pole-to-pole survey of the electrodynamic behavior and plasma properties of the ionosphere. Although Swarm itself has no direct measurements of auroral light nor the energized electrons that cause it, we are able to obtain this information separately through an array of white-light all-sky cameras deployed across the Canadian Arctic as part of the NASA/CSA THEMIS ground-based observatory chain, and soon through the new TREx (Transition Region Explorer) multi-wavelength array, both made possible through a collaboration with the auroral imaging group at the University of Calgary.