Recently, 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). Citizen science has emerged as a powerful way to unravel previously overlooked physical phenomena while making science accessible beyond academia by involving citizen scientists in research projects (Grandin, 2020). In space physics, a particularly noteworthy illustration of the breakthroughs citizen science can achieve is the ongoing studies of the Strong Thermal Emission Velocity Enhancement (STEVE) phenomenon, which consists of faint optical emissions forming a ribbon equatorward from the main auroral arc, essentially

<p>Recently, 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 1500 km for at least four hours. Spacecraft observations confirm that the dunes are associated with electron 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, 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.</p>