Good to see some activity on the list. If you like Earth
science sorts of things, they are really everywhere. A few weeks
ago, PBS had a show about something called sprights. We all know
that when there is a thunderstorm, lightning jumps from cloud to
cloud and from cloud to ground where it sometimes does property
damage and kills people if they happen to be in the way of the
strikes.
Men are killed much more often than women, begging the
comments about how we don't have sense enough to come in out of
the rain and there is probably some truth to that.
The program, however, was about some special lightning
that was discovered in 1973 or so. Ever so often in a really big
electrical storm, we get a flash of lightning that is really big
and bad. It not only may strike the ground but also shoots
straight up until it touches the edge of space, about 60 miles
high. These flashes are called sprights and they are hard for
people to see from the ground because they are on the wrong side
of the clouds. Sometimes, people can see them if the storm is
off at a distance and there is a view of the whole thing, but
most serious spright watchers do their observation from
airplanes.
The sprights are colored while ordinary lightning is
blue-white due to it's high temperatures, about 54-thousand
degrees.
The sprights are known to be red and sometimes other colors. This
is due to the thinning air as you go higher and higher. The air
actually becomes more electrically conductive and the thin
gases behave sort of like the gas in a florescent tube.
Different gases make different colors and the same gas makes
different colors at different pressures so one can see all the
colors of the rainbow if the conditions are right.
According to the program, maybe 1 in 10 flashes in a big storm
produces a spright and some ordinary thunderstorms don't produce
any. Sprights have now been observed from the International Space
Station and several high-altitude jets that were sent up to
observe and photograph them.
The researchers studying the sprights have figured out
that there is more or less a giant electric circuit between the
Earth and space and that electrical impulses such as those
sprights reverberate through our atmosphere such that there is a
ringing effect. The system rings at 8 cycles per second which is
an extremely low frequency. Remember, this is not a sound but an
electrical disturbance. When a big spright fires off somewhere,
even thousands of miles away, that giant bell we live in rings
and scientists can pick up the signals on oscilloscopes if they
are looking for them.
To get an idea of how low this frequency is, think of
the lowest note on the piano. That note is the first A and it
vibrates at 27 cycles per second. You mostly hear the overtones
of that note because 27 hertz is almost too low to hear. The
electrical vibrations are about 1/3 of that so even if you fed
the signal in to an audio amplifier, you would feel it more than
hear it. You'd really need some huge expensive speakers to feel
that note.
There are also electromagnetic disturbances in our
atmosphere that one can hear but that's a whole other discussion
and you need to be near the North or South poles to hear them
best. The old Earth has a lot more stuff going on than many
people realize.
Martin
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