Today’s Image of the Day comes from the NASA Earth Observatory and features a look at the aurora borealis lighting up the night sky over North America.
Even though the sun “sets” at night, it still emits a steady stream of energetic particles and radiation toward the Earth that interact with our atmosphere.
This image was captured at 2:46 am (Central Daylight Time) on April 21, 2018 by the Visible Infrared Imaging Radiometer Suite (VIIRS) on board the Suomi NPP satellite.
An aurora (plural: auroras or aurorae),sometimes referred to as polar lights, northern lights (aurora borealis), or southern lights (aurora australis), is a natural light display in the Earth’s sky, predominantly seen in the high-latitude regions (around the Arctic and Antarctic).
Auroras are the result of disturbances in the magnetosphere caused by solar wind. These disturbances are sometimes strong enough to alter the trajectories of charged particles in both solar wind and magnetospheric plasma. These particles, mainly electrons and protons, precipitate into the upper atmosphere (thermosphere/exosphere).
The resulting ionization and excitation of atmospheric constituents emit light of varying color and complexity. The form of the aurora, occurring within bands around both polar regions, is also dependent on the amount of acceleration imparted to the precipitating particles. Precipitating protons generally produce optical emissions as incident hydrogen atoms after gaining electrons from the atmosphere. Proton auroras are usually observed at lower latitudes.
Image Credit: NASA Earth Observatory