The Sun's outer atmosphere, the corona, is so hot (over a million kelvin) that the Sun's gravity cannot hold it down — it boils off continuously as a supersonic stream of protons, electrons and a trace of heavier ions called the solar wind. Because the Sun rotates as this plasma streams outward, each parcel traces a curving path called the Parker spiral, the same shape a rotating garden sprinkler traces with its water jets.
Eugene Parker predicted the solar wind's existence in 1958 from theory alone, before any spacecraft could confirm it — and the mission that later flew closest to the Sun, NASA's Parker Solar Probe, was named after him while he was still alive to see it launch.
A continuous stream of plasma pours off the Sun's corona, curling into a Parker spiral as the Sun rotates beneath it, sweeping past a small L1 spacecraft parked ahead of Earth, and finally piling up against Earth's magnetic field at the bow shock — the whole chain that gives forecasters advance warning of space weather.
Fast wind from coronal holes and slow wind from the streamer belt trace differently-wound spirals — slower plasma winds tighter, exactly as predicted by tan(ψ) = Ω·r / v — while a simulated L1 spacecraft "measures" the passing stream's speed and density seconds before it reaches Earth.
Pick a source region, or blend both streams, then drag the speed and density sliders and watch the spiral angle, transit time and dynamic pressure update live. Toggle the spiral guide lines and Earth's bow shock, and orbit the scene with your mouse or finger.
Solar wind measured at L1 gives Earth roughly 15-60 minutes of warning before it arrives — just enough time for power grid operators and satellite controllers to brace for a geomagnetic storm.