Abstract
The total solar eclipse that occurred over the Arctic region on 20 March 2015 was seen as a partial eclipse over much of Europe. Observations of this eclipse were used to investigate the high time resolution (1 min) decay and recovery of the Earth's ionospheric E-region above the ionospheric monitoring station in Chilton, UK. At the altitude of this region (100 km), the maximum phase of the eclipse was 88.88% obscuration of the photosphere occurring at 9:29:41.5 UT. In comparison, the ionospheric response revealed a maximum obscuration of 66% (leaving a fraction, Φ, of uneclipsed radiation of 34±4%) occurring at 9:29 UT. The eclipse was re-created using data from the Solar Dynamics Observatory to estimate the fraction of radiation incident on the Earth's atmosphere throughout the eclipse from nine different emission wavelengths in the extreme ultraviolet (EUV) and X-ray spectrum. These emissions, having varying spatial distributions, were each obscured differently during the eclipse. Those wavelengths associated with coronal emissions (94, 211 and 335 Å) most closely reproduced the time varying fraction of unobscured radiation observed in the ionosphere. These results could enable historic ionospheric eclipse measurements to be interpreted in terms of the distribution of EUV and X-ray emissions on the solar disc.This article is part of the themed issue 'Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse'.
Highlights
The total solar eclipse visible over the Arctic region on 20 March 2015 gave observers across the UK an opportunity to witness a partial solar eclipse in which between 95% and 85% of the photosphere was obscured by the Moon, depending on the location of the observer
During the 1999 solar eclipse, measurements were made of the Earth’s ionosphere (the ionized portion of the Earth’s upper atmosphere created when extreme ultraviolet (EUV) and X-ray radiation are absorbed by the neutral atmosphere at altitudes above 90 km)
While good agreement has been found between the large-scale variations in E-region ionospheric number densities and the fraction of ionizing radiation incident upon the Earth’s atmosphere during the solar eclipse, it is not possible to draw any conclusions as to the possibility of identifying the occultation of specific active regions on the Sun by the ionospheric response
Summary
The total solar eclipse visible over the Arctic region on 20 March 2015 gave observers across the UK an opportunity to witness a partial solar eclipse in which between 95% and 85% of the photosphere was obscured by the Moon, depending on the location of the observer. That the chemistry of the Earth’s upper atmosphere has been determined, the many ionospheric experiments conducted during eclipses from 1932 to date have been re-interpreted to study the variation in the size of the uneclipsed corona [3,4,5]. Details of these early ionospheric eclipse experiments were collated in
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