Solar storms are likely to become more disruptive to planes and spacecraft within decades, say researchers at Reading University in England.

The study, published in Geophysical Research Letters, predicts that once the sun shifts toward an era of lower activity, more hazardous radiation will reach Earth. The sun cycles through phases of high and low solar activity. Currently the sun is at a grand solar maximum, which began in the 1920s and lasted throughout the space age.

"All the evidence suggests that the sun will shortly exit from a grand solar maximum that has persisted since before the start of the space age," said Mike Lockwood, professor of space environment physics at Reading.

"In a grand solar maximum, the peaks of the 11-year sunspot cycle are larger and the average number of solar flares and associated events such as coronal mass ejections are greater.

"On the other hand, in a grand solar minimum, there are almost no sunspots for several decades. The last time this happened was during the Maunder Minimum, between about 1650 and 1700."

The research is based on evidence from ice cores and tree trunks going back 10,000 years. The team measured the levels of nitrates and cosmogenic isotopes which are deposited in ice and organic material. The study found that Earth gets hit with more radiation during periods of middling solar activity.

Increased radiation is more of a threat in modern times because aviation and communications technology will be affected by the solar radiation.

"You can tell by the concentration of nitrates in ice sheets that there has been a solar event. What we showed was that they all cropped up at more middling activity than we have been used to," Lockwood told BBC News.

"We used this data to say that an unfortunate combination of solar conditions is coming our way in the next few decades.

"It's just a question of how much worse the radiation gets and how long it lasts."

The evidence seems to indicate that although solar storms will abate after the sun leaves its grand maximum, they will become more powerful, faster and carry more solar particles.

A decline in solar activity also allows more radiation from other parts of the galaxy to enter the solar system.