This past weekend, intense auroras lit up the sky due to massive solar flares and coronal mass ejections from the sun. Flinging wave after wave of charged solar particles toward Earth, those particles slammed into Earth’s magnetic field Friday, triggering what space weather scientists called a level G5 geomagnetic storm — something Earth has not seen since the truly epic solar storms of Halloween 2003 (Space.com). Places that would normally not see the aurora caught a glimpse of the northern and southern lights!
The Aurora Borealis: How it Works
Solar Wind: The Sun constantly emits a stream of charged particles called the solar wind. Occasionally, the Sun experiences solar flares and coronal mass ejections (CMEs), which release even larger amounts of charged particles into space.
Earth’s Magnetic Field: Earth has a magnetic field that extends into space, surrounding the planet. This magnetic field deflects most of the solar wind, directing it around the Earth.
Magnetosphere: Earth’s magnetic field creates a protective bubble around the planet called the magnetosphere. When the solar wind interacts with the magnetosphere, it compresses the side facing the Sun and stretches the side facing away, creating a long tail on the night side.
Entry into the Atmosphere: Some of the charged particles from the solar wind are funneled towards the Earth’s poles by the magnetic field lines. As they approach the Earth’s atmosphere near the poles, they collide with gas molecules, mostly oxygen and nitrogen.
Excitation of Atoms: When these charged particles collide with gas molecules in the atmosphere, they transfer their energy to the atoms and molecules, exciting them to higher energy states.
Light Emission: As the excited atoms and molecules return to their normal energy states, they release the excess energy in the form of light. As seen below, different gases in the atmosphere emit light at different wavelengths, resulting in the characteristic colors of the aurora.
Oxygen
Emits a green or sometimes a rare red light when it’s about 60 miles above the Earth.
Nitrogen
Produces blue or purplish-red light.
Auroral Oval: The aurora borealis is typically seen in an oval shape around the magnetic poles. This is because the charged particles are guided by Earth’s magnetic field lines towards the poles, where they interact with the atmosphere and produce the light display.
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