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SILICON
SILIC
CHIP
www.siliconchip.com.au
Publisher & Editor-in-Chief
Leo Simpson, B.Bus., FAICD
Production Manager
Greg Swain, B.Sc. (Hons.)
Technical Editor
John Clarke, B.E.(Elec.)
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Jim Rowe, B.A., B.Sc
Nicholas Vinen
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2 Silicon Chip
Publisher’s Letter
The visual spectacle of
thunderstorms and auroras
Ever since I was a young boy, I have been fascinated
by thunderstorms and their visual spectacle. Indeed
on many a stormy night at home I love to go upstairs,
open up all the blinds and watch the show. Our home
has panoramic views over the sea and the show can
often be spell-binding as I watch vast cloud formations
flicker and flash, often lighting up the sea and coast as
bright as day. And while many people would probably
refer to these displays as “sheet lightning” (if they think about them at all), they
are far more than that. Yes, the cloud formations do light up and flicker from
one cloud to the next but that is partly because the direct lightning strikes are
obscured from view by the clouds themselves.
But if you look more closely you will often see that most of these strikes are
visible, whether from cloud to ground or from cloud to cloud. And often those
cloud to cloud strikes themselves are truly spectacular, especially when you
realise that they can easily span a distance of 20km or more. And then there
are strikes which don’t appear to hit the ground at all but merely spear off into
the distance or even straight up into space. How does that work?
We now know that what we see of thunderstorms is only a small part of the
show and that for every discharge to earth, there are equal discharges out into
space, far, far, above the stratosphere, as described in our feature article on
Atmospheric Electricity by Dr David Maddison, in this month’s issue.
But the spectacle of a thunderstorm is even more amazing when you realise
that the light show is continuous and lasts for many hours. In truth, a big storm
can last for days. I will often go to bed in the evening while a thunderstorm is
raging outside and then get up in maybe five or six hours later and the storm
will still be visible far out to sea or even beyond the horizon, maybe more than
100km to the east. And if I bothered to follow it on the Bureau of Meteorology’s weather radar, I could still see the storm several days afterwards until it
petered out maybe 1000km away.
All that time, there would have been many thousands of lightning strikes
per hour; no wonder the light show is continuous! And of course, the evidence
of all that electrical activity is not confined to the immediate locality of the
thunderstorm which may easily range over an area of more than 100 square
kilometres or a great deal larger. In fact, it is merely a tiny part of the global
electrical circuit (GEC) and every lightning strike has effects which ripple right
around the planet. And then we read in this month’s issue about Schumann
resonances (between the surface and the ionosphere) and how those resonances
are triggered by lightning strikes. Think of that – the GEC ringing like a bell
due to lightning and that is happening all the time, around the world. And it
has been like that for billions of years!
And the GEC itself is heavily influenced by the Sun and the most visible
evidence of that is in the auroras which are visible over vast areas of the polar
regions. No wonder there is growing tourism to view those wonderful spectacles. And then think about the Sun-induced violent geomagnetic storms.
They utterly dwarf our Earth-bound storms and can have far more reaching
effects as well.
With all that to consider, the ancients were right to tremble as the power of
storms was unleashed upon them. Yet they did not know even a fraction of
what was really going on, just as we today do not fully understand the mechanisms of storms. What we do know is truly enthralling and mind-boggling.
Next time a storm is brewing, even before it arrives in your locality, take the
opportunity to watch and wonder. Be enchanted.
Leo Simpson
siliconchip.com.au
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