When Our Star Misbehaves

Though it may be just a phase, the solar maximum leaves our sun looking quite hostile. by Paul Morledge

Earth has weathered some violent solar storms the past few weeks. The good news is much of the world has observed breathtaking aurorae. The bad news is much of our high-tech infrastructure is vulnerable to assault by solar disturbances.

The sun is currently in its solar maximum, which is the two to three year period around peak activity. Marked by the appearance of numerous, large sunspots, events during solar maxima include flares, coronal mass ejections, and blasts of solar wind that spew massive quantities of charged particles into space. It is these bursts of particles that manifest as ferocious space weather and cause large geomagnetic storms in our planet’s atmosphere. Resulting distortions in Earth's magnetosphere are what disrupt or completely block radio communications, scramble navigation systems, fry power grids, and provide for the awesome spectacle of aurorae.

It used to be that scientists had to wait for anecdotal evidence to infer that Earth’s magnetic field had been disturbed by space weather. For example, in 1959 some telegraph operators in New York found that intense currents were suddenly flowing through their systems, causing their telegraph keys to melt and stick in position. And when police cars in San Francisco radioed their local dispatchers, all they heard in response was the chatter of police dispatchers in Minneapolis. Only after these bizarre events occurred did scientists realize that Earth had been temporarily plagued by geomagnetic storms — in this case, resulting from a huge solar flare.

Today, solar scientists are equipped with a large arsenal of space- and ground-based telescopes committed to viewing the vagaries of the sun. Such intense surveillance allows them to predict solar activity and forecast our space weather. "This is a unique solar maximum in history," said George Withbroe, science director for NASA's Sun-Earth Connection Program. "The images and data are beyond the wildest expectations of astronomers a generation ago."

National Oceanic and Atmospheric Administration (NOAA) space weather forecasters, using data from the Advanced Composition Explorer satellite, are now able to provide about one hour notice for solar radiation storms, and up to two to three days warning of geomagnetic storms. This advanced notice gives communications and navigation systems operators, as well as power grid controllers, a head start in taking defensive measures against such storms.

NASA’s Solar and Heliospheric Observatory (SOHO) satellite helps scientists keep an ever-vigilant eye on the sun. Over the past few months, SOHO researchers have kept close tabs on the number, complexity, and size of sunspots — harbingers of solar upheaval. They have used this information to predict both the magnitude and direction of solar flares. In fact, SOHO imaged a giant cluster of sunspots late last month. This highly active region exploded on April 2. It produced the largest solar flare ever recorded since satellites began measuring solar activity in 1979. (It dwarfed the 1989 solar flare, which led to an intense geomagnetic storm above Canada and caused widespread power outages there). By April 3, this monstrous flare led to a distortion in Earth’s magnetic field big enough to allow Texans to see the Northern Lights. It also caused widespread static across radio frequencies used by commercial airliners, grounding many aircraft for several hours. The high-energy particles thrust out by the flare also temporarily disabled some Global Positioning Satellites orbiting the planet.

People on the ground are not directly affected by space weather because Earth's magnetic field and atmosphere serve as a protective blanket. However, airline passengers can experience as much radiation as 10 chest x-rays on long flights during strong solar storms. And astronauts involved in any extra-vehicular activity can be exposed to potentially lethal amounts of these high-energy photons.

Though most solar scientists believe we are over the hump of this solar maximum — which, as it turns out, has paled in comparison to other solar maxima of this century — there are still some who think the worst space weather is yet to come.

http://www2.astronomy.com/Content/Dynamic/Articles/000/000/000/398wcpdo.asp

-- Martin Thompson (mthom1927@aol.com), April 19, 2001