Aurora dances over Iceland's steaming fumaroles

Stéphane Vetter's Halloween photograph captures ghostly towers of steam venting from fumaroles at Hverir in northeastern Iceland beneath green northern lights. Solar activity triggered the geomagnetic storms that sent energetic particles into Earth's upper atmosphere to create the display.

Source: NASA APOD
Image credit: Stéphane Vetter, via NASA APOD

Hverir is a geothermal field, a stretch of ground where the Earth vents heat directly. Fumaroles are cracks that breathe steam and sulfur gas, and on a cold night the steam rises in thick white towers that catch whatever light is in the sky. On this night the light was the aurora.

An aurora starts on the Sun. Solar activity throws charged particles outward, and when a gust of them reaches Earth, our magnetic field funnels many of them toward the poles. High above the ground, they strike the thin upper atmosphere and hand their energy to the atoms there. Oxygen, excited this way, glows green. That is the color in this photograph: solar wind, converted to light over Iceland.

Iceland sits under the auroral oval, the ring around the magnetic pole where auroras appear most often, which is why it gets displays like this while most of the world does not. Texas needed a storm of the May 2024 class to see aurora from Denton. This is Iceland's sky, not a forecast for anywhere else — but the physics is the same everywhere, and the photograph is a clean record of it: earthly steam below, solar weather above, in the same frame, on Halloween night, as NASA's Astronomy Picture of the Day for October 31.