The solar wind is a continuous flow of plasma (mostly protons and electrons) ejected from the Sun's corona at hundreds of kilometres per second.
The solar wind is a continuous flow of plasma (mostly protons and electrons) ejected from the Sun's corona at hundreds of kilometres per second. It's the medium through which all space weather travels — and its properties dictate how severely Earth's magnetic field responds.
The Sun's corona is so hot (1–2 million °C) that its particles exceed escape velocity. The result is a constant outflow of magnetised plasma streaming through the entire solar system.
These values fluctuate constantly. During a CME impact, speed can exceed 1,000 km/s, density can spike 10x, and the IMF can jump to 30+ nT. It's the spikes that cause geomagnetic storms.
The Interplanetary Magnetic Field is carried by the solar wind. Its north-south component (Bz) is the single most important factor for geomagnetic storm intensity.
We can't predict solar wind conditions from solar observations alone — we need to measure it directly at Earth's doorstep.
Space weather isn't just about what the Sun does — it's about what the solar wind delivers to Earth's doorstep, and whether the magnetic field is oriented to let the energy in.