Auroras are elusive in other ways that fascinate scientists. For instance, where do the energised particles that cause the aurora actually come from. “Not directly from the sun. Lots of people get confused by this,” says Lester. As particles stream towards Earth, they hit the edge of the planet's magnetic “force field”, the magnetosphere. The field guides solar particles towards the poles, where they slam into the Earth's atmosphere and emit light. “You have to have interaction between the magnetosphere and the solar wind,” says Lester. “But this is not always what causes the brightness you see.” Several processes can cause the type of effect on particles that leads to aurora, which throws up bigger questions, like how energy flows through the solar system, how it interacts with Earth and other planets, and how the solar wind affects planets. “Although we understand the basic mechanisms, we don’t understand how it works dynamically,” says Dr Darren Wright, also at the University of Leicester.
There’s a growing need to answer these questions. As those who return home disappointed from a northern lights trip can testify, we can’t really predict auroras. From the vantage point of our own planet we are able to monitor the aurora in real time and combine with satellite measurements, such as those from the International Solar-Terrestrial Physics (ISTP) programme, an international effort run between Nasa, the European Space Agency, and Japan's Institute of Space and Astronautical Science. But despite the tremendous progress, aurora prediction doesn’t come with any guarantees.
This isn’t just an annoying inconvenience to hopeful travelers and stargazers. The more we become reliant on satellite technology, the more we need to forecast space weather more effectively, Sat-navs, such as those used to guide us to our location in Lapland rely on satellites, and these could potentially be damaged by the aurora. “If you get a big burst of activity from the sun, that can knock out some of the systems,” says Lawrence. A burst of solar activity can also affect many things here on Earth. In 1989, magnetic storms associated with an aurora caused a collapse of the Quebec power grid, leaving six million Canadians without electricity for hours. “If the aurora expand to lower latitudes than normal, “there could be problems to oil pipelines, transformers, power girds, anything with a metal conductor,” adds Lester.
Astronauts are also at risk. In August 1972, as Apollo 16 had returned to Earth and Apollo 17 readied for its mission, there was a flare, which had astronauts been on the Moon at the time, could have been potentially lethal. Future missions to the Moon and Mars rely on understanding our sun and knowing how to protect astronauts. Deeper space exploration is also reliant on this knowledge. “For expensive space craft such as Nasa’s Juno mission to study Jupiter, there was a lot of research on how to protect instruments,” says Wright.
This is important because aurora are not unique to Earth, you can find them on planets like Jupiter and Saturn too. Aurora on Jupiter are a hundred times brighter than those found on Earth and are bigger than our entire planet. The reason we see similar displays on planets such as Jupiter is because they have magnetic fields, caused by having liquid metallic cores. Not all planets have aurora, though. Mars, for example, no longer has an active magnetosphere, and therefore no aurora, though according to Wright it could have done in the past. (The fact that Mars doesn’t have aurora also adds to the danger of any planned human mission to the planet; our magnetic field protects us from harmful solar radiation.)