How do solar flares affect the Earth?
Strong solar flares can release a stream of energetic subatomic particles that often give us spectacular auroral displays.
Solar flares are energetic releases of electromagnetic radiation (and sometimes matter) from the surface of the Sun, thought to be caused by the localised twisting and realignment of the Sun’s magnetic field. Most of this electromagnetic radiation is absorbed by Earth’s dayside ionosphere and has little effect on the planet.
However, strong solar flares can increase the ionisation of the upper atmosphere, knocking electrons out of their atoms, which then interferes with the propagation of short-wave radio signals used for communications. Solar flares also heat the ionosphere, causing it to expand, which is a potential threat to artificial satellites in low-Earth orbit.
A more dangerous scenario is when a solar flare releases a stream of energetic subatomic particles towards Earth. These ‘coronal mass ejections', or CMEs, buffet Earth’s magnetic field, squeezing and shaking it, and can induce enormous electric currents in telephone lines and electrical distribution networks on our planet’s surface. CMEs can also expose astronauts to dangerous levels of radiation.
One positive outcome of CMEs is that they are often responsible for spectacular auroral displays at Earth’s polar regions. Overall, though, there are no long-term effects of solar flares or CMEs, either to humans, or to planet Earth.
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Asked by: Bill Orzel, via email
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