Solar flares and CMEs affect Earth on different timelines because of the nature of what each one is and how it travels.
- Solar Flares: These are bursts of electromagnetic radiation, so they travel at the speed of light, reaching Earth in about 8 minutes. This means their effects, like disruptions in radio communication and GPS signals, are almost immediate after the flare occurs. Solar flares primarily affect the sunlit side of Earth’s upper atmosphere (ionosphere), where the radiation can cause radio blackouts.
- Coronal Mass Ejections (CMEs): CMEs are massive ejections of solar plasma (charged particles) and magnetic fields. Since they consist of matter, they move much more slowly than light, typically taking 1 to 4 days to reach Earth. The time varies based on the speed of the CME, which can range from hundreds to over a thousand kilometers per second. If a CME is directed toward Earth, its impact results in geomagnetic storms, which can disturb satellites, power grids, and other technology.
So, while solar flare effects are almost instantaneous, CME effects are delayed by hours or days, depending on their speed. Both events can occur independently, which is why Earth may experience one without the other, or experience both with a time lag between their effects.
