Solar Wind Signatures Throughout the High-Latitude Atmosphere

A series of studies during the last decade have shown clear evidence of solar wind-related periodicities in the variations of different parameters of the lower (troposphere/stratosphere) and upper (thermosphere/ionosphere) atmosphere, over the high-latitude regions. This commentary is prompted by a recent study of the fluctuations of neutral density, winds, and temperatures near 90 km, which provides evidence of such a solar wind-related response in the mesosphere as well. It is timely to point out to the wider geophysical community that solar wind responses at different altitudes strongly indicate that the whole atmospheric column has a response to solar wind high-speed streams, something that few atmospheric scientists would have anticipated 10 years ago. Reviews of the wider body of work in this research field, however, conclude that different processes of solar wind-atmosphere coupling dominate at different altitudes and there remain unanswered questions about some of the details of these mechanisms and their relative importance. We therefore suggest that the studies considered here could usefully be extended in their methodology in order to constrain the mechanisms involved, rather than just identifying the solar wind driver. One example would be to examine time delays between the input, that is, the solar wind variations, and the response at different altitudes; another is to look for latitudinal variations in the amplitude of effects.