With a solar storm washing over the Earth this weekend, it's welcome timing for a new solar radiation warning system that gives more warning than ever before.
Developed by a US-South Korean team, it can forecast the radiation from violent solar storms nearly three hours (166 minutes) in advance, giving astronauts and air crews flying over Earth’s polar regions time to take protective action.
The first particles from a solar storm reach the Earth in just ten minutes, but it's the later ones that are the most dangerous, because there are many more of them.
And, using data collected by two neutron monitors installed years ago at the South Pole by the University of Delaware — one inside and one outside the Amundsen-Scott South Pole Station — the team says it can make useful predictions.
When the first protons hit an air molecule in Earth’s atmosphere, they blast apart into tiny pieces, which, in turn, slam into other air molecules, and so on. Neutrons, neutrally charged particles, are produced as part of this cascading event.
The team's established a correlation between the energy of the first-arriving protons and the intensity of the later-arriving, more dangerous particles. They've tested it out against 12 solar events, using against observations made by geosynchronous satellites, and found good agreement for protons with energies higher than 40 to 80 megaelectron (million) volts.
Depending on the protons’ energy, the system provides a warning time up to 166 minutes.
And this will become increasingly important as we move into the solar maximum, a peak period of solar storm activity which generally occurs every 11 years.
"If you’re in a plane flying over the poles, there is an increased radiation exposure comparable to having an extra chest X-ray you weren’t planning on,” says professor John Bieber of the University of Delaware.
"However, if you’re an astronaut on the way to the moon or Mars, it’s a big problem. It could kill you."
Most astronauts have flown in low Earth orbit in recent years, but if we go back to the moon or decide to send humans to Mars, we need to think about these things, Bieber says. Indeed, he the Apollo astronauts were lucky.
"Somehow they got these moon launches between big solar flares that would have killed them right then and there," he says.