Solar Winds Contribute To Lightning Strikes On Earth
Solar winds from the Sun create the beautiful Northern and Southern lights in the Earth's sky, but scientists have recently discovered that they are also responsible for one of the most natural phenomena on Earth: lightning.
The discovery, made by researchers at the University of Reading's Department of Meteorology, came after they noticed increased lightning strikes in Europe for more than a month after streams of high-energy particles, or solar winds, arrived from the sun. The solar winds can greatly effect weather, according to the researchers, who said that satellite tracking of the winds may help them forecast hazardous weather weeks in advance.
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"Our main result is that we have found evidence that high-speed solar wind streams can increase lightning rates," said Dr. Chris Scott, lead author of the research, in a press release. "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 weather down on Earth, but our work provides new evidence that similar, if lower energy, particles created by our own Sun also affect lightning."
The scientists proved their theory by analyzing records of lightning strikes that occurred at a radius of 500 kilometers from central England between 2000 and 2005. The record of lightning strikes was compared with data from NASA's Advanced Composition Explorer (ACE) spacecraft, which lies between the Sun and Earth and measures the characteristics of solar winds.
They found that 40 days after the arrival of the solar wind, lightning peaked with an average of 422 strikes across the UK, compared to 321 strikes before the solar wind hit the Earth's atmosphere. Maximum strikes were observed 12 to 18 days after the arrival of the solar wind.
Solar winds are streams of electrons and protons that are released from the upper atmosphere of the Sun. They can travel at more than a million miles per hour into Earth's atmosphere, a phenomenon that occurs every 27 days or so, or the time it takes the Sun to make one complete rotation.
Although most of the particles get deflected by the Earth's magnetic field, some particles, such as a slower stream and faster stream, may combine to form a stronger magnetic field, which allows them to get through. These highly charged particles that vary in density, temperature, and speed alter the electrical properties of the air upon collision with the Earth's atmosphere.
According to the team, the particles may be penetrating storm clouds where they discharge electrical energy in the form lightning. "We propose that these particles, while not having sufficient energies to reach the ground and be detected there, nevertheless electrify the atmosphere as they collide with it, altering the electrical properties of the air and thus influencing the rate or intensity at which lightning occurs," Scott said in the release.
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