Solar flare facts

LONDON - A massive gas bubble that could cause havoc with power grids, satellite and communication systems hit the Earth's magnetic field early on Wednesday and is likely to have the biggest impact in Alaska and Asia.

The solar flare erupted from a big sunspot at about 6am EST (midnight NZT) on Tuesday.

Following are some brief details on solar flares:

* What is a solar flare?

Flares are the most violent event in the solar system. A bright hydrogen arc emitting ultraviolet radiation and X-rays erupts from the Sun's corona (outermost layer of the Sun's atmosphere).

Flares are usually associated with sunspots, dark cool areas caused by intense magnetic fields breaking through the sun's surface.

Sunspots can send out clouds of electromagnetic plasma, called coronal mass ejections, composed of a hot ionised gas of charged solar particles.

The sun goes through 11-year cycles in sunspot activity.

* What causes a flare?

Although the effects of solar flares have been studied for years, their cause remains largely a mystery. They occur when energy stored in twisted magnetic fields is suddenly released.

More violent flares occur when sunspots group. They throw out charged particles and radiation with the energy of millions of atomic bombs.

* What effects can solar flares have?

Solar flares can wreak havoc with mobile phones, radio relays, satellite links and power grids on Earth.

In addition to their impact on communications and power on Earth, solar flares can pose radiation poisoning danger to astronauts in space.

They can also produce dazzling aurora -- the northern or southern lights.

If the magnetic field of the cloud is pointing northward, the same as the Earth's magnetic field, the effects will be minimal. If the orientation is southward the effects will be more dramatic and could cause a severe geomagnetic storm.

* Previous solar flares:

One of the largest previous sunspots ever seen was on April 2, 2001 but the monster flare shot out away from Earth.

A solar storm in March, 1989 knocked out the electrical system in all of Quebec and destroyed a large power transformer in New Jersey.

- REUTERS

NOAA NEWS: Powerful solar storm reaches earth

National Oceanographic and Atmospheric Administration's Space Environment Centre