Oct. 31, 2013:Some Halloweens are scarier than others.

Ten years ago, in late October 2003, space weather forecasters

experienced a frission of dread when two gigantic sunspots appeared.

Both had complex magnetic fields that harbored energy for strong

explosions. If the spots turned toward Earth and erupted....

That's exactly what happened. From Oct. 19th through Nov. 7th 2003,

there were 17 major eruptions on the sun, including a record-setting X28

flare. One after another, CMEs (coronal mass ejections) slammed into

Earth's magnetosphere, causing geomagnetic storms and Northern lights

seen as far south as Florida and Texas. On Halloween itself, many trick

or treaters witnessed blood-red auroras--very spooky indeed.

At the peak of these "Halloween Storms," as solar physicists began

to call them, airlines had to re-route polar flights to lower

latitudes, the power went out in parts of Sweden, and more than half of

NASA's satellite fleet experienced problems ranging from temporary

shut-downs to permanent damage. The FAA's Wide Area Augmentation System

(a network of radio transmitters that improves GPS navigation for

aircraft) was offline for approximately 30 hours due to the storm, and

the Japanese ADEOS-2 satellite was severely damaged.

Fast forward 10 years to October 2013, and the sun is storming again.

A week before Halloween 2013, a new coven of big sunspots

appeared. To date (Oct. 31st), they have unleashed more than half a

dozen major flares including four X-class events. Earth is not

experiencing the same kind of effects as ten years ago, however, because

the eruptions have not been as energetic and, moreover, most of them

have missed our planet. This makes the Halloween Storms of 2013 less

scary than their 2003 predecessors.

"This spate of activity is inconsequential when compared to the

2003 events,” recalls Joe Kunches, a longtime forecaster working at

NOAA’s Space Weather Prediction Center in Boulder CO. He points out that

geomagnetic storm indices now are an order of magnitude smaller than

they were ten years ago.

Nevertheless, the current storms are remarkable because they are

the "flariest" thing to come along in a while. Solar activity waxes and

wanes in 11-year cycles. In 2003, the sun was ramping down from a

strong Solar Max. The potent Halloween storms of that year were, if not

actually predicted, at least not surprising. 2013 is different. The

current solar cycle is one of the weakest in a century. This makes the

mini-Halloween Storms of 2013 a bigger surprise even as they do less

damage.

Also mitigating the damage in 2013 is a decade of improvements in

space weather forecasting. Using data from NASA science spacecraft such

as the twin STEREO probes and the Solar Dynamics Observatory, NOAA

analysts are able to predict the arrival of solar storms with better

accuracy than ever. This gives satellite operators, NASA mission

controllers, and airline flight planners extra time to safeguard life

and property.

Ultimately, the ending of this spooky tale may require a

re-write. Why? Because it's not over yet. As Halloween 2013 comes and

goes the sun is still peppered with large and active sunspots. One of

them may yet send a powerful flare and CME directly toward us, sparking

storms akin to the ones from a decade ago.

When you knock on the door and shout “trick or treat”, you never

know what you might get when the door opens. The sun is much the same

way.