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A BALL OF FURY

For those of you that were outdoors late on the night of Sept 10th and into the morning of the 11th of this year, you were probably rewarded with a vibrant display of Northern Lights. I was in Montreal that time as guest speaker at a public star night. Many the attendees noticed the northern sky turn a faint greenish tone around 10:15 p.m. Within an hour the sky began to rock – in colour that is. Like the swaying of a curtain in the breeze, sheets of lime green began to ripple. At times this intensity was so bright you could almost read a newspaper. This activity persisted a good part of the night.

No, we were not being invaded by beings of another world, but it definitely came from outer space. We can thank our day time star – the Sun for this free and awesome light show. The Sun is an enormous ball of burning hydrogen gas which on occasion unleashes huge bubbles of charged particles called Corona Mass Ejections (CME). Our planet is severely dwarfed compared to the Sun and these mammoth solar eruptions. 109 Earths fit across the Sun’s belly and about 1.3 million of our worlds can fit in it.

Over an eleven year cycle, the Sun’s interior undergoes tremendous twisting of its various layers. Like the snapping of an elastic band, all that energy has to go somewhere and at sometime. From time to time the solar surface sports dark blemishes called sunspots. Compared to the Sun’s 5,500°C surface temperature, these spots are cooler (about 3,700°C), magnetic regions that appear in greater numbers at the height of the eleven year cycle. NEVER LOOK AT THE SUN WITHOUT PROPER FILTRATION, BLINDNESS CAN OCCUR. It is now known that CMEs erupt far from these spots and has no direct relation to them.

When such a solar belch occurs, charged particles fly straight off the Sun’s surface (photosphere) at some two million kilometres per hour. If a blast happens to in our direction, we usually receive its effect in about three days. After all, the Sun’s average distance from us is close to 150 million kilometres. Once these fast moving particles reach our upper atmosphere, we could see a cosmic light show like no other. However, this depends on the Earth’s polarity called the magnetopause. If north points south and south points north, the solar shockwave is permitted to react with our north and south poles thus causing the exquisite light show. This reaction compares to roughly the workings of a fluorescent tube. It the magnetopause points correctly, the shockwave is deflected and no aurora occurs.

These mystic lights in the sky have been gazed in fear for centuries on end. Many civilizations have their own legends as time went on. Many people believe these shimmering lights are reflections off glaciers in the north. Such is not the cause. But it appears that we do get a greater number of displays starting in the fall. Although this magnetic storm cannot harm us on Earth, thanks to our atmosphere, radio, cells phone and orbiting satellites can be affected. Passengers in commercial airliners could get a few X-rays worth of low radiation. I would not want to be on a space walk doing an S5 storm – radiation hazard.

You can easily photograph these displays. Using a single lens reflex camera (SLR), simply load your camera with light sensitive film (ASA 400 speed). Attach it to a camera tripod and use a cable release. This will eliminate shaking of the camera. Move the shutter speed dial to “B”. Now when you trip the cable release and fold it, you have manual control on exposure time. 20 to 30 seconds should do. Digital camera can use the same setup and you see your results instantly.

We now live in the information highway, with news and images delivered to you in real time. One such site is the Solar and Heliospheric Observatory, SOHO which is an orbiting satellite some one million kilometres from our planet. SOHO is dedicated to watching and studying the Sun 24/7. To follow the Sun’s weather, I suggest Space Weather. This site gives a head’s up on solar activity and the possibility of Aurora activity.

Keep looking up and one night you will see the dancing curtains. Email me your observations.

Upcoming events

October 7, 2005 Monthly meeting of the Royal Astronomical Society of Canada, Ottawa Centre.

Clear skies,
Gary Boyle
garyboyle@sympatico.ca

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Gary Boyle is a freelance astronomy educator and writer. He teaches astronomy to adult and children as well as hosts many summertime ‘Star Nights’ at Provincial Parks and campgrounds.
Visit his web site at: www.wondersofastronomy.com
Send Questions & Comments about the Starry Nights to Gary Boyle

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