American Geophysical Union | 2017 Jun 21
[img3="Earth’s airglow can be seen from the International Space Station as a greenish bubble 95 kilometers (59 miles) above the Earth’s surface. Credit: NASA"]https://news.agu.org/files/2017/06/Imag ... irglow.jpg[/img3][hr][/hr]Dating back to the first century, scientists, philosophers and reporters have noted the occasional occurrence of “bright nights,” when an unexplained glow in the night sky lets observers see distant mountains, read a newspaper or check their watch.
A new study accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union, uses satellite data to present a possible explanation for these puzzling historical phenomena.
The authors suggest that when waves in the upper atmosphere converge over specific locations on Earth, it amplifies naturally occurring airglow, a faint light in the night sky that often appears green due to the activities of atoms of oxygen in the high atmosphere. Normally, people don’t notice airglow, but on bright nights it can become visible to the naked eye, producing the unexplained glow detailed in historical observations.
Few, if any, people observe bright nights anymore due to widespread light pollution, but the new findings show that they can be detected by scientists and may still be noticeable in remote areas. Bright airglow can be a concern for astronomers, who must contend with the extra light while making observations with telescopes.
“Bright nights do exist, and they’re part of the variability of airglow that can be observed with satellite instruments,” said Gordon Shepherd, an aeronomer at York University in Toronto, Canada, and lead author of the new study. ...
WINDII Airglow Observations of Wave Superposition and
the Possible Association with Historical “Bright Nights” - G.G. Shepherd, M. Cho
- Geophysical Research Letters (online 06 Jun 2017) DOI: 10.1002/2017GL074014 (preprint)