A key area of study in space weather is magnetosphere-ionosphere coupling, often abbreviated as M-I coupling. This area deals with how the activities in the magnetosphere (the region of space where the Earth’s magnetic field dominates) and the ionosphere (the very top of the Earth’s atmosphere, where electrically neutral gasses are ionized by solar radiation). These two regions physically couple in many ways. Electric currents flow from the magnetosphere down into the ionosphere, causing gasses to circulate with the currents. The ionosphere will resist and regulate the flow of electrical current and gas, changing the electric fields within the magnetosphere. Plasma, or electrically charged gas, escapes from the ionosphere and populates the magnetosphere, changing mass content of near-Earth outer space.
Confusing? It is, even to scientists. M-I coupling is fundamental to understanding the characteristics and dynamics of space and space weather, but it is complicated, detailed, and heavily inter-dependent on many processes. Scientists have been working on this topic for decades. In 1974, a group of scientists sequestered themselves in Yosemite National Park with the goal of advancing their understanding of a hot new topic, M-I coupling:
Forty years later, in 2014, a second M-I coupling workshop was held at Yosemite National Park to see how our understanding has evolved over four decades. It included many of the scientists who attended the first M-I workshop, and each block of talks was preceded by footage from the original workshop and remarks to add historical context to our work. It was a unique experience of new and old; a singular conference where each presenter could see the giants on whose shoulders we stand.
How far have we come? On one hand, very far! Four decades of new research and new measurements of both the ionosphere and magnetosphere have yielded a far deeper understanding of M-I coupling. Conversely, it was painfully obvious that in many ways, the discussions of today are all too similar to those in 1974. This is because while we understand in greater detail the workings of the M-I system, some of the big picture questions from 1974 continue to be debated. The introductory talk by Dr. Jim Burch does an excellent job of summarizing this paradox:
This paradox reminds me of how my undergraduate advisor once described science. The layperson expects an experiment to provide an instant and concrete answer to a question, as if a scientist was turing over a trivia card to reveal an answer. However, it is more like a window that is so filthy that you cannot see through it. The initial experiments are the first attempts to clean this window: it removes a lot of dirt, and we can start to see through it, but there are still smudges and streaks that keep the view occluded. So we try again, and the glass becomes clearer, but it takes many, many attempts and a lot of effort before we can see through with perfect clarity. In space science, our window is still very dirty: there are many unknowns that keep us from fully understanding how the magnetosphere-ionosphere system works. Because of this, it is often necessary to revive old conversations and controversies so that we are sure that our window to understanding is truly clean, at least in a few spots.
A new book has been published by the American Geophysical Union covering the work presented at the 2014 meeting, entitled “Magnetosphere-Ionosphere Coupling in the Solar System.”