Auroral Dunes Observed Over Norway

August 20, 2021

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Photographer: Geir T. Birkeland Oye

Summary Author: Geir T. Birkeland Oye; Cadan Cummings

The astounding photos above show a unique and newly named atmospheric phenomenon called auroral dunes. Named after their visual similarity to sand dunes, these wavy, green sheets of aurora occur between 65-80 degrees latitude and 50 - 75 miles (80-120 km) in altitude in the auroral mesosphere-lower thermosphere-ionosphere (MLTI). Mesospheric studies are difficult to conduct because the altitude is too high for balloons and below the altitude satellites orbit, thus causing this region of the atmosphere to be nicknamed the ignorosphere. For years, viewers in the Arctic have observed these colorful dune-like auroras without the ability to fully explain them. In 2018, new insights into what causes this type of aurora were unveiled when several teams of citizen scientists across Finland and Sweden worked together to photograph and triangulate their location. Their research findings suggested that auroral dunes are likely a type of atmospheric gravity wave- called a mesospheric bore- that gets trapped in the mesosphere at approximately  60 miles (100 km) in altitude and illuminates when interacted with solar wind particles. Although mesospheric bores would likely be extremely difficult to observe in the Arctic due to interference from airglow and nightglow events, the proposed mechanism for auroral dunes is supported by their approximately 45 km wavelength and high incidence in this very thin layer of the atmosphere.  Photos taken January 22, 2012. 

Photo Details: Sigma 15mm fisheye lens, Canon EOS 500D, ISO: 1600, various exposure times.

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