'Slinky' magnetic loops seen on Sun

Magnetic arcade: Like a coiled spring on the Sun's surface

July 21, 2000 - BBC

On 14 July, an active region on the Sun's surface, designated AR9077, erupted in one of the most energetic flares seen on the surface of our star for years.

Superhot gas and magnetic fields mingle over an the active region

As a result of the explosion, a cloud of energetic charged particles was ejected towards Earth, triggering a geomagnetic storm and displays of aurorae.

Watching the site of the explosion on the Sun was Nasa's Trace satellite. Its cameras took a remarkable close-up of AR9077 just after the flare erupted.

Taken in ultra-violet light, the image shows multi-million degree hot plasma cooling down while supported in an arcade of magnetic loops. Each magnetic loop is far larger than the diameter of the Earth.

Trace monitors the Sun from Earth orbit

Active regions on the Sun's surface are caused by magnetic fields, in the form of gigantic tubes, that rise-up from below the visible surface. When they do so, they become filled with superhot gas that highlights their loops and coils.

Because the magnetic loops are twisted, they eventually buckle and reconfigure their shape, liberating vast amounts of energy that explosively heats gas and expels some of it into space.

Trace's instruments have been designed to look at the magnetic structures on the Sun's surface and follow their changes as flares develop.

Inside Earth's Magnet

June 16, 2000 - AP

The mysterious force that controls magnetic north and south is becoming a bit less mysterious - thanks to some massive number-crunching. Scientists have developed computer simulations that show, in three-dimensional detail, how Earth generates a magnetic field.

"The breakthrough was doing the problem three dimensionally," said Stephen Zatman a geophysicist at the University of California, Berkeley. "And the reason it was possible was really the computational ability - the fact that computers have become fast enough and have large enough memory."

The churning of the Earth's molten iron core, combined with the way our planet rotates, turns the Earth into a massive magnet - spinning out a magnetic field. At the North Pole, the field points straight upwards, and at the South Pole it points straight down.

This engine that creates all this is called the Earth's geodynamo.

In a paper published in this week's issue of the journal Science, geophysicist Bruce Buffett of the University of British Columbia reviewed our current understanding about what makes the geodynamo go.

"Perhaps the most important advance in the past few years is the development of (models) that achieve self-sustaining dynamo action," Buffett said.

The first of these models was developed by Gary Glatzmaier of the University of California, Santa Cruz, and Paul Roberts of UCLA.

The Glatzmaier-Roberts model was also the first that was able to "evolve." They plugged in all the numbers available for magnetic fields and velocities in the Earth's core, but didn't guide their outcomes. When the model is sped up and run for the equivalent of 100,000 years, its magnetic field flip-flops.

That's striking because the same thing happens on the real Earth. Magnetic traces in rocks show that around every 200,000 years, the North Pole becomes the South Pole and vice versa.

The Glatzmaier-Roberts model shows that the polar flip is guided by fluctuations in heat between Earth�s molten core and the rocky mantel that surrounds it. But the model is still not detailed enough to show what sets off the switch in the first place.

The problem, Zatman said, is that we can't slip down to the center of the Earth to take a peek.

"We don't know exactly what the Earth's magnetic field looks like inside the core," he said. "So we don't know what should go into the model, or what we should expect to get back out."