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Loading contentDark, 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.
Facts on this topic will be cited from these primary and reference sources.
Space-weather forecasts and alerts: aurora (OVATION), the Kp index, and the G1–G5 geomagnetic storm scale.