When two people in a room speak with nearly identical voices, it sounds like just one person from the outside. But if you listen closely to their pronunciation, you'll notice different accents. The same goes for the solar wind — the stream of charged particles from the Sun. Its slow component travels at about 400 km/s, and all the jets seemed alike. But a new program that automatically tunes itself to find differences picked out two distinct 'accents'—based on composition, not speed.

The Sun ejects particles in two main ways. The fast wind comes from coronal holes — regions where magnetic field lines are open, like funnels. The slow wind could originate either in the streamer belt, a zone of closed magnetic loops, or at the edges of those same holes. The speeds of these two sources are nearly identical, differing by just 4 km/s, like the difference between a walk and a light jog. But their composition differs: near the Sun, ions lose different numbers of electrons, and this 'chemical fingerprint' persists all the way out. The program took seven such characteristics and, without any hints, sorted 30,602 observations from the Solar Orbiter probe into three groups. Two of them are slow wind with different compositions, and the third is fast wind. The intermediate group matched the boundaries of coronal holes exactly. Now, knowing which stream is heading toward Earth, we can better predict disturbances for satellites and communications.