Abstract
AbstractRecently, citizen scientist photographs led to the discovery of a new auroral form called “the dune aurora” which exhibits parallel stripes of brighter emission in the green diffuse aurora at about 100 km altitude. This discovery raised several questions, such as (i) whether the dunes are associated with particle precipitation, (ii) whether their structure arises from spatial inhomogeneities in the precipitating fluxes or in the underlying neutral atmosphere, and (iii) whether they are the auroral manifestation of an atmospheric wave called a mesospheric bore. This study investigates a large‐scale dune aurora event on 20 January 2016 above Northern Europe. The dunes were observed from Finland to Scotland, spanning over 1,500 km for at least 4 h. Spacecraft observations indicate that the dunes are associated with particle precipitation and reveal the presence of a temperature inversion layer below the mesopause during the event, creating suitable conditions for mesospheric bore formation. The analysis of a time lapse of pictures by a citizen scientist from Scotland leads to the estimate that, during this event, the dunes propagate toward the west‐southwest direction at about 200 m s−1, presumably indicating strong horizontal winds near the mesopause. These results show that citizen science and dune aurora studies can fill observational gaps and be powerful tools to investigate the least‐known region of near‐Earth space at altitudes near 100 km.
Highlights
A study carried out jointly by researchers and citizen scientists described an auroral form previously unreported in the literature, which was called “the dunes” (Palmroth, Grandin, Helin, et al, 2020)
This study investigates the nature of the dune aurora by combining photographs taken by citizen scientists and satellite observations during a large-scale event which took place above Northern Europe on 20 January 2016
This study investigated a dune aurora event which took place in the local evening hours of 20 January 2016 above Northern Europe
Summary
A study carried out jointly by researchers and citizen scientists described an auroral form previously unreported in the literature, which was called “the dunes” (Palmroth, Grandin, Helin, et al, 2020). The dune aurora is an optical phenomenon, so far mostly reported at subauroral latitudes too, which had not been analyzed in the peer-reviewed scientific literature until it was brought to the attention of the scientific community by citizen scientists. It consists of a modulation of the optical emission intensity within the green diffuse aurora exhibiting an oscillatory pattern in the horizontal dimension. Observational evidence suggests that this phenomenon can persist for tens of minutes to over an hour
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