A blast of solar wind is pummeling Earth’s magnetosphere, sparking the strongest geomagnetic storm so far this year.Though it registered a “7” on the 0-to-9 K-index scale of magnetic disturbances, the storm is expected to pass quickly. The silver lining, for those at high-latitudes anyway, is a beautiful show of auroras — the result of high-energy particles from the sun smashing into oxygen and nitrogen in Earth’s atmosphere. As the molecules return to normal, they give off energy in the form of photons. The colors in the aurora depend on which atmospheric gas is being revved up by the invading electrons and how much energy is being exchanged. Oxygen emits greenish yellow or red light; Nitrogen generally produces blue.

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