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> What distinguishes the neutrosphere from the ionosphere? The degree to
> which atmospheric gases are ionized?
Yes.
> By what?
Mostly by solar UV radiation.
> Meteor infall?
This causes only local ionization along the meteor track, but this
ionization is strong enough to bounce off not only HF (shortwave)
but also VHF. Ham radio operators sometimes communicate through
"meteor scatter" as they call it. Amateur astronomers can observe
meteor showers with radio like this: get a directional (yagi) antenna
to your FM receiver, tune in some FM station that's a bit farther
away than you normally are able to receive, and point your antenna
there. Now, whenever a meteor occurs in that direction, you'll
be able to briefly (for 5-10 seconds) hear that radio station.
> Cosmic radiation?
This causes only local ionozation, but this ionization may occur all
the way down to the ground, or even directly in physicists'
laboratories.
> Solar wind?
Most of the solar wind is deflected by the Earth's magnetic field,
far above our atmosphere. However, when the solar acticity is
unusually strong and the solar wind very intense and also contains
very energetic particles, solar wind particles may penetrate to
low altitudes, 30 km or so. This usually happens at higher latitudes
since the charged particles from the solar wind is directed towards
the poles by the earth's magnetic fields. When the atmosphere is
ionozied at these unusually low altitudes, there's usually a
"black-out" in shortwave radio communications: the radio waves
can no longer bounce off the (normal) ionosphere at 150-250 km
altitude since they're absorbed by this unusual ionization down to
ca 30 km altitude. Such an event is called PCA (Polar Cap Absorption).
> Also, how does the level of the ionosphere relate to changes in Earth's
> magnetic field and the associated radiation belts?
They both relate to disturbances in the solar activity. One common
event is the PCA mentioned above.
> Just a curious question from a relative newbie: I've been interested in
> meteorics for many years, but never before had the time to study
> meteorology or atmospheric science... Until meteoptic came along.
> Fascinating list!
>
> Clear skies,
> Lew Gramer
Paul Schlyter, Swedish Amateur Astronomer's Society (SAAF)
Grev Turegatan 40, S-114 38 Stockholm, SWEDEN
e-mail: pausch_at_saaf.se psr_at_home.ausys.se
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