SPACE WEATHER FORECAST

“At the moment we have telescopes looking at the Sun,” says Desai, “they see stuff happening on the Sun’s surface, and as soon as a CME occurs we can start running our models to predict what time the CME will arrive, and when it does, what will its properties be—how big is its magnetic field, and how much plasma is contained inside of it. Typically, CMEs can take between three and five days to reach us, but a severe one could reach us sooner.”

Indeed, NASA figures put the shortest time for a CME to cross the 93 million miles between us and the Sun as 15 hours, for a mindboggling speed of over six million miles per hour.

Desai’s team has discovered that, if CMEs come at us in pairs, then the second storm will be more violent as a result. While investigating the 23 July 2012 event, they discovered a previous CME on 19 July. The fourday gap between the storms was long enough for the solar wind to recover from the stress, but by using computer modeling to place the second CME closer to the first, the Imperial team discovered that it became stronger, and faster.

If a CME is moving faster than the background solar wind (a million mph), then ahead of the plasma cloud travels an interplanetary shockwave that can arrive at Earth with just an hour’s warning. While this shockwave transfers its energy mainly through electromagnetic fields rather than particles, it can push particles ahead of it, increasing the chances of a radiation storm here on Earth.