People in the UK often joke that any kind of weather can cause delays. What many are yet to consider is that the source of some delays might be found unexpectedly at the center of the Solar System. The Sun’s activity can affect the signaling systems that help trains run smoothly, scientists have found.

New research, presented at the National Astronomy Meeting, has revealed the effects that moderate and strong solar storms have on signaling systems. 

To be able to track trains, railway lines in the UK are segmented into blocks of about 1 to 2 kilometers (around 1 mile). When a train is on a particular segment, there’s no current, and there is a relay that detects the lack of said current and places the block on red. If there is a current, then the block is empty and stays green.

But solar storms can induce currents. A moderate storm might have an electric field strength of 2 volts per kilometer and strong storms might have double that, although Sweden has recorded much higher values, with storms more than 7 volts per kilometer detected along railways. And there are estimates that predict that extreme storms could reach strengths of 20 volts per kilometer.

The team looked at two portions of the UK rail network. A South-North line between the cities of Preston and Lancaster, and a West-East Line in Scotland between Glasgow and Edinburgh. They found that the electric field that a moderate storm can generate is enough to trick the system into thinking a train is there when there isn’t.

“Most of us have at one point heard the dreaded words: ‘your train is delayed due to a signalling failure’, and while we usually connect these faults to rain, snow, and leaves on the line, you may not have considered that the Sun can also cause railway signals to malfunction,” author Cameron Patterson, a graduate researcher at Lancaster University, said in a statement. 

“We are now working on looking at the case where trains are present on the line, and how strong a storm needs to be to turn a red signal back to green – a far more hazardous scenario potentially leading to crashes!”

Solar storms affect electronics in multiple ways. While the concern that major storms could completely disrupt entire systems needs to be taken more seriously, the effects of weaker but more numerous storms that can degrade electric and electronic systems over time shouldn't be overlooked.