In A Nutshell
The trigger for lightning bolts—especially the fatal cloud-to-ground type—has long been a mystery. However, scientists now believe that the Sun’s magnetic field may be one culprit. By twisting and turning the Earth’s weaker magnetic field, the rotation of the solar magnetic field permits cosmic rays to enter our atmosphere, creating a path like a thin conducting wire for electrical charges inside storm clouds to strike the ground. The good news is that the Sun’s magnetic field is highly predictable, which might help us to forecast the timing, place, and type of lightning strikes.
The Whole Bushel
Until now, lightning strikes have been quite unpredictable. The trigger for lightning bolts—especially the fatal cloud-to-ground type—has long been a mystery. However, scientists now believe that the solar magnetic field, powered by currents deep in the Sun that are millions of miles from Earth, is one culprit.
The solar magnetic field acts like a bar magnet. As the Sun rotates, the field changes its position relative to Earth, sometimes pointing toward us and sometimes away from us. This can skew our planet’s own magnetic field, which acts as a shield against high-energy particles (known as “galactic cosmic rays”) that bombard us from outside our solar system. By twisting and turning the Earth’s weaker magnetic field, the rotation of the solar magnetic field permits these cosmic rays to enter our atmosphere, creating a path like a thin conducting wire for electrical charges inside storm clouds to strike the ground.
Using data from satellites and the UK’s Met Office for 2001 to 2006, researchers from the University of Reading discovered that the UK experienced a 50 percent jump in thunderstorms when the solar magnetic field was directed away from Earth.
“From our results, we propose that galactic cosmic rays are channeled to different locations around the globe, which can trigger lightning in already charged-up thunderclouds,” said lead researcher Dr. Matt Owens. “The changes to our magnetic field could also make thunderstorms more likely by acting like an extra battery in the atmospheric electric circuit, helping to further ‘charge up’ clouds.”
Space weather experts like Dr. Owens have been able to accurately predict the position of the Sun’s magnetic field since the 1970s. They just didn’t realize it affected our weather. By adding this information to typical weather forecasting techniques, they should be able to make better predictions of when and where lightning will occur.
But they expect this information will also help them to forecast the type of lightning. When cosmic rays enter our planet’s atmosphere, we experience an increase in the more damaging and fatal cloud-to-ground lightning bolts. When we’re shielded from these cosmic rays, then we may get more sheet lightning because the electrostatic discharge might happen in the clouds. Sheet lightning appears as a general brightening of the clouds rather than a thunderbolt striking the ground.
Of course, even with this new information, there’s a limit to how much forecasters can predict. They can estimate how likely it is that a particular geographic area will experience lightning strikes. But they won’t be able to tell us exactly where and when lightning will hit the ground.
Nevertheless, these improved forecasts could be extremely helpful for power companies and other businesses that need to protect fragile electronic equipment. More accurate predictions could also reduce fatalities by warning people when and where to avoid dangerous lightning strikes outdoors.