Aurorae on the way? | Astronomy.com

On September 8, active region 10808 on the Sun produced both M-class and X-class solar flares within a few hours of each other. The Transition Region and Coronal Explorer satellite captured this image, which shows the dramatic energy released during those flares. View a movie of this activity near the bottom of this page.

J. Cirtain (CfA) / NASA

September 13, 2005
Observers in North America could be treated to sporadic, yet dazzling, sky shows during the upcoming few nights. Astronomers predict aurorae could shine in northern latitudes, hanging red and green curtains across the sky.

“This evening [September 12], there is about a 70-percent chance of medium-strength aurorae at our Boston latitude,” says Jonathan Cirtain of the Harvard-Smithsonian Center for Astrophysics. “Aurorae could reach even farther south.”

Eruptions from Sunspot 808 could generate mid-September 2005 auroral displays seen from northern latitudes.

John McConnell

Aurorae occur during geomagnetic storms, which are triggered by eruptions on the Sun. A large, active region has produced several strong flares recently. The solar wind, a fast-moving stream of particles constantly moving from our star, carries the Sun’s magnetic field into space. The wind, typically flowing at 250 miles (400 kilometers) per second, can mingle with Earth’s magnetic field, generating electrical currents that force protons and electrons into the polar atmospheres. Collisions between these particles and atmospheric gases illuminate the polar ovals, typically between heights of 62 and 155 miles (100 to 250 kilometers).

Using the Transition Region and Coronal Explorer (TRACE) satellite, Cirtain’s team witnessed unusual energetic activity in this sunspot region. “In one case, we recorded 5 separate flares over the course of 6 hours. That’s very unusual.”

This activity could continue — the National Oceanic and Atmospheric Administration predicts a 75-percent chance of additional X-class flares within the next day.

When this activity appeared in August with Region 10798, 798 for short, eruptions caused a few auroral displays on Earth. The area disappeared from sight as the Sun revolved. Late last week, the sunspot recurred, giving hope to aurora aficionados. (When an active sunspot reappears after one revolution, it receives a new numeral designation.)

To view the potential aurorae, keep your eyes fixed north from your favorite dark-sky location.

For future aurora predictions, visit our space weather section. To access this content, you will need to use a subscriber number or newsstand code.