The Sun is notorious for its 11-year cycle, but also for the fact that it has sunspots on its surface that allow astronomers to analyze its “health” and, more importantly, predict space weather. But in years such as this one, when the solar minimum is in full effect, and very few sunspots are available, establishing future space weather patterns gets very difficult. Recently, however, a fortunate discovery made in Israel gave the scientific community another method of analyzing the Sun.
While analyzing lightning strikes coming in from Africa – via a network of Very Low Frequency (VLF) wire antennas –, Professor Colin Price, from the Tel Aviv University, and graduate student Yuval Reuveni discovered peculiar patterns in the discharges once every 27 days. This is the precise time it takes for the Sun to spin once around its axis. Details of the discovery appear in the latest issue of the respected Journal of Geophysical Research – Space Physics.
The work, experts say, could have significant implications for understanding the interactions that exist between the Sun and the Earth.
“Even though Africa is thousands of miles from Israel, lightning signals there bounce off the Earth's ionosphere – the envelope surrounding the Earth – as they move from Africa to Israel. We noticed that this bouncing was modulated by the sun, changing throughout its 27-day cycle. The variability of the lightning activity occurring in sync with the sun's rotation suggested that the sun somehow regulates the lightning pattern,” Price explains. He is also the head of the Department of Geophysics and Planetary Science at TAU.
“Short-term changes in solar activity can also impact satellite performance, navigational accuracy, the health of astronauts, and even electrical power grid failures here on Earth. Many scientists claim that the sun's variability is linked to changes in climate and weather patterns, so the small changes we observed every 27 days could also be related to small variations in weather patterns. Our data may help researchers examine short-term connections between weather, climate, and sun cycles. With this tool, we now have a good system for measuring the pulse of the sun,” he adds.
Price also believes that the new discovery may help climate-change scientists formulate new hypotheses on how the Sun influences the weather on our planet, both during solar minimums and solar maximums. The expert is himself an acclaimed climate scientist. “We know that Earth rotates once every 24 hours, and the moon once every 27.3 days. But we haven't been able to precisely measure the rotation rate of the sun, which is a ball of gas rather than a solid object; 27 days is only an approximation. Our findings provide a more accurate way of knowing the real rotation rate, and how it changes over time,” he concludes.