Auroras and blackouts

Adventures on Earth for August 4, 2010
By George E. Beetham Jr.

A solar flare was expected to reach Earth on Tuesday of this week, perhaps interrupting radio communications and communications satellites and providing spectacular auroral displays at the poles.


The immediate reaction to internet users to the report was concern that the solar flare might pose a danger to life on Earth.

The answer to that question is that solar flares have been erupting in our sun and flying to Earth for the 4.6 billion years our planet has existed.

The only danger, so far as we can tell, would be shortwave radio users bruising their fists pounding on their radios or people in the Arctic and Antarctic straining necks watching the aurora.

How widespread the aurora would be was anybody’s guess when the story broke on Monday. The Geophysical Institute at the University of Alaska Fairbanks forecasts aurora activity, but no report was available for the first three days of August.

There was a slight chance that aurora would be visible in this region, but cloudy skies likely prevented that.

In any event, city lights would have blacked out any aurora that might have been visible from this latitude.

When the sun gives off energy in flares or other ejections, the energy flows outward from the sun. When it reaches Earth, the energy interacts with the planet’s magnetic field.

The aurora is the magnetic field after it is excited by the solar wind.

What we learn from the aurora is that the magnetic field is not static. It ebbs and flows, like ocean waves or wind. The curtains of light shimmer and pulse, sometimes slowly, sometimes more rapidly.

Depending on what matter is carried to Earth from the sun, the aurora can take on colors. Often the aurora is a whitish haze, perhaps with a tint of green.

The aurora are one of nature’s most spectacular displays, particularly when they are more active. As far as the planet is concerned, it is just another day. It has been going on for a long, long time, and it is likely to continue for another long, long time.

Wherever aurora are visible, city lights likely prevent in-town viewing. One has to travel to a dark, rural area to see aurora. Mountaintops are another good place.

Radio communications often black out during solar activity. The ejections excite the radio spectrum, particularly the part of the spectrum used for long-range radio (shortwaves and VHF frequencies).

Often, east-west communications are completely blocked while north-south communications continue unaffected. It’s another geophysical mystery why this is so.

The blockage usually lasts for 24 hours or less and the airwaves return to normal after everything settles down. Blockages can be a minor annoyance or a major problem, depending on how much of the spectrum is affected and what services use those frequencies.

Ham radio operators may want to take a night off, perhaps drive out of town to see if they can catch a view of the aurora.

If you miss it, there are videos of aurora displays all over the internet.