Science & history · An active star
CMEs and the solar wind
Two kinds of material leave the Sun: a steady wind all the time, and occasional giant clouds called coronal mass ejections.
The solar wind
The solar wind flows outward at over a million miles per hour, from features such as coronal holes and active regions. It blows a bubble around the solar system, the heliosphere, whose edge is the heliopause.
Coronal mass ejections
A CME is an enormous cloud of electrically charged gas. When one is aimed at Earth it can arrive in as little as about 15 hours, or take several days. On arrival it can drive currents in power grids, swell the upper atmosphere and set off aurora. The fastest charged particles from an eruption can arrive in about 30 minutes.
Sources
- NASA What Is the Solar Wind? (opens in a new tab) for over a million miles per hour; coronal holes; heliosphere; aurora · checked 2 October 2026
- NASA Solar Storms and Flares (opens in a new tab) for flares (light, ~8 minutes), CMEs (15 hours to days), particle storms (~30 minutes), effects · checked 2 October 2026