Record-breaking blasts from unseasonable solar storms seen in late 2003 are just now reaching the edge of the Solar System, scientists reported on Thursday.

More than a dozen coronal mass ejections - eruptions of super-heated gas triggered by tangled magnetic fields on the Sun's surface - shot from the star over a period of 20 days last October and November.

In the events, which pointed in different directions because of the Sun's rotation, radiation and high-speed particles surged ahead of gas from the blasts themselves. On 28 and 29 October, that gas reached Earth in record time - about 20 hours, sweeping past the planet at five million miles per hour.

"If you look at the overall speed of the events - the sheer momentum of it - it's the biggest event we've measured in space," University of Michigan astronomer Thomas Zurbuchen told reporters at a NASA teleconference.

An unprecedented number of spacecraft tracked the blasts as they sped outward from the Sun, producing a trove of data that may help scientists predict the effects of future space storms.

The blasts produced auroras as far south as Florida in the US, shut down power in a city in Sweden, and forced astronauts aboard the International Space Station to duck into a relatively well shielded service module.

Martian impact

A few hours after reaching Earth, the blasts hit Mars, which has no global magnetic field to shield it from solar storms. The events disabled a radiation-monitoring instrument on the orbiting spacecraft Mars Odyssey. And computer simulations suggest they also blew off part of the planet's upper atmosphere, an effect that may have helped erode the planet's surface water over 3.5 billion years.

"We know there used to be a lot more water than there is right now. Where did it go?" Zurbuchen said. "One of the key ideas people are talking about is the connection to these space storms."

The Ulysses spacecraft near Jupiter and the Cassini spacecraft near Saturn both detected radio waves when the blasts slammed into the planets' magnetic fields.

In April, the blasts - slowed to 1.5 million miles per hour - even caught up with the Voyager 2 probe, which has travelled about 7 billion miles from the Sun since its launch in 1977. And preliminary data suggest they may have reached the Voyager 1 spacecraft, nearly 9 billion miles from the Sun this Tuesday, eight months after erupting from the star.

Interstellar particles

At those distances, the Sun's magnetic influence begins to wane as solar wind particles come into contact with particles from interstellar space. The blasts are expected to temporarily expand - by 400 million miles - the boundary of this heliosphere, which they will probably reach by early 2005.

"If the blast wave still has enough energy at that point, it can cause the interstellar material to radiate radio waves, which can tell us how far it is to the edge of interstellar space," said Ed Stone of the California Institute of Technology.

Researchers say predicting space storms has come a long way in recent years - they got a little advance warning in 2003 by measuring vibrations on the Sun's surface from sunspots on the far side of the star. And using computer models, scientists accurately predicted when the blasts would reach the Voyager 2 probe, accounting for the slowing effects of interstellar material.

"We got it to within a day," said Justin Kasper of the Massachusetts Institute of Technology. "The neat thing is our models are getting sophisticated enough we can model out to the heliosphere."

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