Solar Radiation Storm

A solar radiation storm, also called a proton storm or S-scale event, occurs when the Sun launches a sudden, large surge of high-energy solar energetic particles — mostly protons — toward Earth and the rest of the solar system. NOAA's Space Weather Prediction Center rates these storms on a five-level Solar Radiation Storm scale, from S1 (minor) to S5 (extreme), based on the measured flux of high-energy protons reaching Earth's vicinity. The real-world effects scale up dramatically with intensity: minor storms cause little more than a small increase in radiation exposure for airline crews flying polar routes, while extreme S5 storms can force high-altitude polar flights to reroute, expose astronauts to radiation levels requiring them to shelter in more shielded parts of a spacecraft, degrade solar panels on satellites, and even cause a measurable increase in radiation at aircraft cruising altitudes. Because these energetic particles travel almost as fast as light, a solar radiation storm can begin within tens of minutes of the triggering solar flare or coronal mass ejection, leaving very little warning time — which is why continuous, real-time monitoring by satellites positioned to watch the Sun is so critical for protecting both people and technology.