Airglow of the Earth's atmosphere

Airglow over the VLT (Very Large Telescope) platform.

Airglow, a faint emission of light by a planetary atmosphere, is caused by various processes in the upper atmosphere, such as the recombination of atoms which were photoionized by the sun during the day, luminescence caused by cosmic rays striking the upper atmosphere, and chemiluminescence caused mainly by oxygen and nitrogen reacting with hydroxyl ions at heights of a few hundred kilometres. It is not noticeable during the daytime because of the scattered light from the sun. The airglow at night may be bright enough to be noticed by an observer and is generally bluish in colour.
 

Eruption of Mount Agung

In 2017 Mount Agung, a volcano on the island of Bali in Indonesia erupted violently enough to cause evacuation and air-flight disruption. As of 27 November 2017 the alert level is at its highest and evacuation orders are in place. The eruption caused some 40,000 people to be evacuated from 22 villages around Mount Agung. It also caused surrounding airports to be closed. Lombok International Airport, located on the neighboring island of Lombok, closed on 26 November and was reopened the next morning. Ngurah Rai International Airport, located at the southern tip of the island and southwest of the volcano, closed on 27 November. More than 400 flights were canceled, and about 50,000 passengers were grounded.