Scientists have discovered new evidence to suggest that lightning on Earth is triggered not only by cosmic rays from space, but also by energetic particles from the Sun. University of Reading researchers found a link between increased thunderstorm activity on Earth and streams of high-energy particles accelerated by the solar wind, offering compelling evidence that particles from space help trigger lightning bolts.

 

Publishing their study today, 15 May 2014, in IOP Publishing's journal Environmental Research Letters, researchers from Reading's Department of Meteorology found a substantial and significant increase in lightning rates across Europe for up to 40 days after the arrival of high-speed solar winds, which can travel at more than a million miles per hour, into Earth's atmosphere.

 

Although the exact mechanism¹ that causes these changes remains² unknown, the researchers propose that the electrical properties of the air are somehow altered as the incoming charged particles from the solar wind collide with the atmosphere.

 

The results could prove useful for weather forecasters, since these solar wind streams rotate with the Sun, sweeping³ past Earth at regular intervals⁴, accelerating particles into Earth's atmosphere. As these streams can be tracked by spacecraft, this offers the potential for predicting the severity of hazardous⁵（有危险的） weather events many weeks in advance.

 

Lead author of the study, Dr Chris Scott, said: "Our main result is that we have found evidence that high-speed solar wind streams can increase lightning rates. This may be an actual increase in lightning or an increase in the magnitude of lightning, lifting it above the detection threshold of measurement instruments.

 

"Cosmic rays, tiny particles from across the Universe accelerated to close to the speed of light by exploding stars, have been thought to play a part in thundery（雷鸣般的） weather down on Earth, but our work provides new evidence that similar, if lower energy, particles created by our own Sun also affect lightning.

 

"As the Sun rotates every 27 days these high-speed streams of particles wash past our planet with predictable regularity⁶. Such information could prove useful when producing long-range weather forecasts."

 

Professor Giles Harrison, head of Reading's Department of Meteorology and co-author of the ERL article, said: "In increasing our understanding of weather on Earth we are learning more about its important links with space weather. Bringing the topics of Earth Weather and Space Weather ever closer requires more collaborations between atmospheric⁷ and space scientists, in which the University of Reading is already leading the way."

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