The northern lights are a fascinating natural phenomenon. These animated shows in the night sky have contributed to the mythology, folklore, and art of many cultures and civilizations in the northern hemisphere. In the early 17th century, Italian astronomer Galileo named the phenomenon "aurora borealis" after the Roman goddess of morning, because he thought the luminescence was due to reflected sunlight in the atmosphere.
We now know that the aurora are powered by the solar wind—an ever-present stream of ions and electrons that blows off the sun and expands outwards through space. This wind interacts with the Earth's magnetic field, distorting it and creating a downstream tail.
Solar wind energy is stored in this long tail and released unpredictably in bursts of accelerated particles and electron currents. Such bursts, called substorms, occur along the equatorial plane of Earth's night side, and then propagate along magnetic field lines to the polar regions, where they cause spectacular auroral displays.
But to this day, these auroral storms are not fully understood. Numerous studies of the Earth's magnetosphere and space weather have never been able to pinpoint where in the magnetosphere the energy of the solar wind transforms explosively into auroras.