The impact of energetic electron precipitation on mesospheric hydroxyl during a year of solar minimum
Journal article, Peer reviewed
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Original versionJournal of Geophysical Research: Space Physics. 2016, 121(6), 5914–5929 10.1002/2016JA022371
In 2008 a sequence of geomagnetic storms occurred triggered by high-speed solar wind streams from coronal holes. Improved estimates of precipitating ﬂuxes of energetic electrons are derived from measurements on board the NOAA/POES 18 satellite using a new analysis technique. These ﬂuxes are used to quantify the direct impact of energetic electron precipitation (EEP) during solar minimum on middle atmospheric hydroxyl (OH) measured from the Aura satellite. During winter, localized longitudinal density enhancements in the OH are observed over northern Russia and North America at corrected geomagnetic latitudes poleward of 55°. Although the northern Russia OH enhancement is closely associated with increased EEP at these longitudes, the strength and location of the North America enhancement appear to be unrelated to EEP. This OH density enhancement is likely due to vertical motion induced by atmospheric wave dynamics that transports air rich in atomic oxygen and atomic hydrogen downward into the middle atmosphere, where it plays a role in the formation of OH. In the Southern Hemisphere, localized enhancements of the OH density over West Antarctica can be explained by a combination of enhanced EEP due to the local minimum in Earth’s magnetic ﬁeld strength and atmospheric dynamics. Our ﬁndings suggest that even during solar minimum, there is substantial EEP-driven OH production. However, to quantify this eﬀect, a detailed knowledge of where and when the precipitation occurs is required in the context of the background atmospheric dynamics.