Solar Sources

Areas of strong, complex magnetic field on the Sun, usually marked by sunspots, where magnetic energy builds up and is released. Active regions are the launch sites of the largest solar flares and coronal mass ejections, and are watched closely for space-weather forecasting.

Regions of the Sun's corona where the magnetic field opens out into space rather than looping back, appearing dark in X-ray and ultraviolet images. They are the source of the fast solar wind, and the high-speed streams they send out drive recurring geomagnetic activity.

Dark, cooler patches on the Sun's visible surface where intense magnetic fields suppress the flow of heat from below. Their number rises and falls with the solar cycle, and they mark the magnetically active regions from which flares and CMEs erupt.

The ionised layer of Earth's upper atmosphere, created by solar ultraviolet and X-ray radiation. It reflects and refracts radio waves — enabling long-distance HF communication — but solar flares and geomagnetic storms disturb it, causing radio blackouts and errors in satellite navigation.

The roughly eleven-year rise and fall of the Sun's activity, traced by the number of sunspots from solar minimum to solar maximum and back. Its underlying magnetic cycle takes about twenty-two years, as the Sun's polarity flips and returns. Activity — flares, CMEs, and storms — peaks near solar maximum.