The preliminary results of the research, which show that radiation from the Sun has increased over the past 50 years, provide a warning for the world. The scientists say that a brighter Sun increases global warming.
"Changes we saw seem to suggest that the Sun is brighter than during previous eclipses," said Dr Chris Davis, head of ionospheric monitoring at Rutherford Appleton Laboratories at Chilton, Oxfordshire, one of the scientists co-ordinating research for several universities during the eclipse.
He and his colleagues set up an experiment at Helston School in Cornwall to test a hypothesis by scientists at the laboratory that the radiation from the Sun is increasing.
They bounced radio waves off the Earth's ionosphere to see how it was affected by the phenomenon. The ionosphere is created by the Sun's radiation so it decays during a total eclipse. Dr Davis said that it disappeared "much more slowly" than during eclipses elsewhere in the world in the 1940s, suggesting that the Sun's corona, all that can be seen during totality, had got brighter.
He stressed that final conclusions could not be drawn until the measurements had been fully studied and the results published in a peer-reviewed scientific journal. But the preliminary results provided "promising" evidence to support the hypothesis that the Sun was brightening.
Previous work at the laboratory, based on measuring the magnetic field of the Sun, had suggested that it had got brighter by about a 10th of 1 per cent since records began at the beginning of the century, and last week's research was giving them "confidence" that something of the sort was indeed happening. "This may not seem a lot but it would have a noticeable effect on the Earth," said Dr Davis. It would increase global warming and made it more urgent that the world tackled the pollution that also caused it. "If the Sun is getting brighter, which is beyond our control, the last thing we should do is to add fuel to the fire," he said. He added that the brightening seemed to be part of a natural cycle - "part of the natural breathing of the star" - but nobody could yet tell how long it would continue.
In another experiment, a one-second glimpse of the eclipse gave researchers from University College London and the University of Southampton new insights into chemical processes in the Sun, based on colour variations in the corona.
An experiment by Heinz Muller, a retired academic from Sheffield, in conjunction with Aberystwyth University and the Rutherford-Appleton laboratory, measured changes in the solar winds during an eclipse. That exploited the coincidence that Wednesday's eclipse took place during a shower of meteors. The researchers will work out how they were blown about by the solar winds during the eclipse and how it altered their paths.
Radio amateurs all over Europe were asked by the Rutherford-Appleton laboratory to carry out broadcast conversations at the same time during the eclipse and measure changes in the strength of the signals, to give information on how the atmosphere changes during an eclipse.
In a further eclipse experiment, scientists from Lancaster University measured radio emissions from stars and astronomical sources to see how much they are absorbed by the ionosphere during the extreme conditions of a solar eclipse.Reuse content