Space Weather 101
💨 Solar Wind
View live Solar Wind data →What is Solar Wind?
The solar wind is a continuous stream of charged particles — mostly electrons and protons — that flows outward from the Sun's outer atmosphere (the corona) in every direction, carrying the Sun's magnetic field along with it. It's not an occasional event; it blows constantly, but its speed and density vary a lot depending on conditions on the Sun at the moment that particular stream left.
Why it matters
Solar wind speed is one of the key ingredients — alongside a southward Bz — in determining whether conditions are favorable for a geomagnetic storm and aurora. Faster wind delivers more kinetic energy to Earth's magnetic field, and a sudden speed jump is often the clearest real-time sign that a coronal mass ejection has arrived.
Typical values
Quiet, typical solar wind runs about 300-400 km/s. Wind escaping through coronal holes (gaps in the Sun's magnetic field) often reaches 500-700 km/s. Fast CME-driven shocks can spike above 700-800 km/s, and the most extreme recorded events have exceeded 2,000-3,000 km/s.
How scientists measure it
Spacecraft stationed at the L1 Lagrange point — about 1.5 million km from Earth, directly between Earth and the Sun — carry instruments that directly sample the solar wind as it streams past, measuring particle speed, density, and temperature in real time, roughly 15-60 minutes before that same wind reaches Earth.
Why it affects Earth
Faster, denser solar wind pushes harder against Earth's protective magnetic bubble (the magnetosphere), compressing it and potentially triggering geomagnetic storms, aurora, and — in extreme cases — disruptions to satellites, power grids, and radio communication.
FAQ
Does the solar wind ever stop?
No — it blows continuously in all directions, at speeds and densities that vary constantly, but it never fully stops.
What's the difference between solar wind and a CME?
The solar wind is the Sun's constant background outflow. A coronal mass ejection (CME) is a distinct, much larger burst of plasma launched during a specific eruptive event, riding along within or ahead of the ordinary solar wind.