LONDON, Dec 2 (Reuters) – An upcoming cycle of stormy solaractivity risks causing damage to electrical transformers andthreatening vulnerable energy infrastructure around the globe, areport by an insurance group says.

The sun follows a predictable 11 year activity cycle, with thenext period of stormy activity expected to begin in 2012-13.

The report by German insurance group Allianz said a high impactsolar storm, not easily predicted due to its recorded rarity, couldcause blackouts and economic losses of over $1 trillion and thatthe worst case scenario would be even worse.

“What we're coming into at the moment is the bad (space)weatherperiod,” Jim Wild of Britain's Lancaster University, an expert insolar plasma physics, told Reuters.

A large explosion on the surface of the sun could releasebillions of tonnes of superheated magnetically charged gas at aspeed of a million miles per hour, and when that gas hits theearth's magnetic field, it can trigger a big solar storm.

The severity of a potential disruption has made experts atinsurance and national security institutions take notice.

“When you start to imagine not having electricity in a sizeablefraction of a country or a continent for weeks or even months …it's serious business,” Wild said.

SMALL LEAD TIME

The difficulty lies in predicting how often serious solar typeevents occur.

The small lead time given by satellites is also a problem forpreventing solar storm damage, as currently no satellite is closeenough to the sun to give more than an hour's warning, Wildsaid.

Updating the satellites to give the earth more preparation timewould cost around $1 billion, he added.

Space weather is a relatively new area of study, withsophisticated observations going back only 50 years and lacking aninternational coordinated tracking system such as that found withnormal meteorological weather.

“We have very little on a solar time scale,” Wild said.

The most damaging storm in recent memory was a 1989 outage inQuebec, Canada, which affected six million people.

The first scientific recording of a large solar storm was madein 1859 by English astronomer Richard Carrington, who observed awhite light explosion on the surface of the sun.

Wild said: “what they didn't know back then was why about two orthree days later you could see the northern lights over Cuba andall of the telegraph system was disrupted by geomagneticactivity.”

According to the Allianz report, an event on the same scaletoday would cause extensive damage to electricalinfrastructure.