On the historical hunt for the origin of the enigmatic green line in the spectrum of the aurora borealis.
The icon indicates free access to the linked research on JSTOR. Every eleven years or so, the Sun's magnetic field goes a little crazy and flips, magnetic north becoming south and vice versa. Before this happens, solar activity builds to a maximum, ejecting massive plasma and waves of radiation. We're near a "solar max" now. These energetic eruptions are a "potentially perilous time for Earth," disrupting communications and hobbling infrastructure. On the plus side, a "solar max" can result in spectacular displays of polar lights. In recent weeks, the aurora borealis (northern lights) have been seen as far south as Florida, while the auroral australis (southern lights) have been seen as far north as Queensland, Australia. An aurora's curtains of color in the night sky are created by the interaction of the Earth's magnetosphere and atmosphere with the solar wind. Some of the electrons and protons streaming out from the Sun get caught by the Earth, where they excite or ionize aspects of atmospheric chemistry. Humans have been bedazzled by the effects for millennia, making up many stories to explain the enigmatic lights. The science of auroras, on the other hand, is of more recent vintage. Historian of science Helge Kragh writes that auroral research "didn't constitute a scientific discipline" of its own until half way through the twentieth century. During the early part of the last century, scientists in a variety of disciplines, including…