Effects of the March 2015 solar eclipse on near-surface atmospheric electricity

Abstract

Measurements of atmospheric electrical and standard meteorological parameters were made at coastal and inland sites in southern England during the 20 March 2015 partial solar eclipse. Clear evidence of a reduction in air temperature resulting from the eclipse was found at both locations, despite one of them being overcast during the entire eclipse. The reduction in temperature was expected to affect the near-surface electric field (potential gradient (PG)) through a reduction in turbulent transfer of space charge. No such effect could be unambiguously confirmed, however, with variability in PG and air-Earth current during the eclipse being comparable to pre- and post-eclipse conditions. The already low solar radiation for this latitude, season and time of day was likely to have contributed to the reduced effect of the eclipse on atmospheric electricity through boundary layer stability. The absence of a reduction in mean PG shortly after time of maximum solar obscuration, as observed during eclipses at lower geomagnetic latitude, implied that there was no significant change in atmospheric ionization from cosmic rays above background variability. This finding was suggested to be due to the relative importance of cosmic rays of solar and galactic origin at geomagnetic mid-latitudes.This article is part of the themed issue 'Atmospheric effects of solar eclipses stimulated by the 2015 UK eclipse'.

The solar eclipse: a natural meteorological experiment

“…This is partly consistent with results from the 11 August 1999 eclipse over southeast England where decreased convection was observed and convective cloud dissipated [23]. However, Bennett [15] concluded that the reduction in turbulence was insufficient to influence the surface atmospheric electric field.…”

“…[4,22]). Burt [14] and Bennett [15] analysed the wide range of measurements made at the Reading University Atmospheric Observatory, UK, where the eclipse reduced the solar radiation by 85% but the measurements were obtained under a 400 m thick layer cloud with its base at about 200 m above the surface. During the 2015 eclipse, Burt [14] found a reduction in near-surface turbulence and a reduction in cloud base height.…”

“…In addition, Portas et al [10] describe the use of the 20 March 2015 solar eclipse for science outreach activity, using a citizen science approach to generate a bespoke observing network; the related science results are analysed separately by Barnard et al [11]. Multiple conventional measurement systems are employed to analyse eclipse-related changes in surface meteorological [12][13][14][15][16][17], sounding balloon [7], satellite [18] and ionospheric data [19]. Atmospheric modelling studies to underpin interpretation of the observations for advancing conceptual understanding are provided by Clark [20] and Gray & Harrison [21].…”

Shear‐induced electrical changes in the base of thin layer‐cloud

“…The layer-cloud investigated here persisted over RUAO during 19 March 2015 (year day 78 of 2015) and dissipated after local noon on 20 March 2015. The cloud received unusually close scrutiny because it obscured the partial solar eclipse which occurred on 20 March, and the associated atmospheric electricity and meteorological conditions are extensively described in Bennett (2016) and Burt (2016) respectively. Figure 1 shows ceilometer, PG and sounding measurements made beneath the layer-cloud.…”

Atmospheric changes from solar eclipses

“…An additional source of atmospheric electrical observations was from magnetic observatories, such as the magnetic data from the 21 August 1914 total solar eclipse compiled by Bauer and Fisk (1916), which includes atmospheric electrical and meteorological measurements. Bennett (2016) gives a more detailed account of atmospheric electrical measurements during solar eclipses.…”