Electrodynamical structuring and heating of the ionosphere revealed through low-enery ion imaging

在空间研究中出现的众多问题中，有两个反复出现：为什么宇宙的结构如此之高？而且，太空中的等离子体是如何变得如此有能量的？日冕环的精细结构和其中的百万开尔文等离子体就是最好的例子。虽然人们对极光电离层的认识较少，但它也不例外。在一个以地球半径为边界的系统中，极光形式的主要空间尺度从几十公里到几十米不等。而且，在低至500公里的高度观测到的极光等离子体的温度可以与日冕的温度相媲美。在极光中，高度的结构和惊人的高能量都归功于电磁力的存在，或者更具体地说，是太阳风、磁层和电离层通过兆安级电流和穿过它们的磁场相互作用的结果。

Of the numerous questions that arise in the study of space, two recur time and again: Why is the universe so highly structured? And, how do plasmas in space become so energetic? The fine structure of coronal loops and the million-Kelvin plasmas that populate them are prime examples. While less widely appreciated, the auroral ionosphere is no exception. In a system whose boundaries are measured in Earth radii, the dominant spatial scales of auroral forms range from tens of kilometers to tens of meters. And, auroral plasmas at altitudes as low as 500 km have been observed to reach temperatures rivaling those of the solar corona. In the aurora, both the high degree of structure and the surprisingly high energies owe their existence to electromagnetic forces, or more specifically to the interaction of the solar wind, the magnetosphere and the ionosphere through mega-Ampere-scale electric currents and the magnetic fields that thread them.