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，有两个问题反复出现：为什么宇宙如此高度结构化？ 太空中的等离子体是如何变得如此充满活力的？ 日冕环的精细结构和构成它们的百万开尔文等离子体就是最好的例子。 极光电离层虽然没有得到广泛的认识，但也不例外。 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公里的高度观察到极光等离子体达到与日冕相媲美的温度。 在极光中，高度的结构和令人惊讶的高能量都归功于电磁力，或者更具体地说，归功于太阳风、磁层和电离层通过兆安培级电流和磁场的相互作用。

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.