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PE1RRR > SOLAR 08.02.21 09:18l 89 Lines 4675 Bytes #999 (0) @ WW
BID : 6369-PE1RRR
Read: GUEST
Subj: I'll have a sporadic E please bob :)
Path: IW8PGT<IZ3LSV<IR1UAW<IW2OHX<UA6ADV<LU4ECL<VK2RZ<PE1RRR
Sent: 210208/0815Z @:PE1RRR.#NBW.NLD.EURO #:6369 [Rijen] $:6369-PE1RRR
From: PE1RRR@PE1RRR.#NBW.NLD.EURO
To : SOLAR@WW
Iâ€Öll have a Sporadic-E please Bob
FEBRUARY 3, 2021 BY RED
You will see several mentions of Sporadic-E on my site, so Iâ€Öve taken a shot
here at explaining the phenomenon in my own words. I hope you enjoy the tangent
from the usual posts, but if you are already versed in solar physics feel free
to skip along- wait maybe you wonâ€Öt get that reference unless you read this
bit… ðŸ¤ö
Sporadic E events- a phenomenon frequently observed in the early 90s as the
increased frequency of the Sunâ€Ös coronal mass ejections created observable
disturbances in the Earthâ€Ös ionosphere.
The phenomena occurs naturally every 11-year cycle, waxing and waning between
the peaks- known as the solar maximum– during these periods, the most
sunspots are produced.
Sunspots are a product of the complex interactions between the suns powerful
magnetic fields and the fusion reactions occurring deep within the core of the
sun. Magnetic fields twist and contort through the plasma as the sun rotates on
its axis, eventually some of these powerful magnetic fields can no longer hold
on to their couplings and break apart in violent and destructive solar flares,
scattering the sunâ€Ös plasma deep into space. Sometimes, directly at Earth.
Powerful magnetic interactions during solar flare events also cause magnetic
disturbances that travel at the speed of light towards Earth. These are known
as geomagnetic storms and can in the most extreme cases cause severe problems
for the electrical grids that deliver power to our industry and homes, as well
as damage satellites that operate out beyond the protection of our magnetic
field.
Approximately three days after a geomagnetic storm, the sub-light-speed
particles ejected from the sun arrive at Earth and hit the magnetic field, and
if powerful enough can sometimes reach the upper ionosphere. These particles
are extremely high-energy, if they were to reach the surface of Earth they
would have a devastating and deadly effect on biological organisms.
The magnetic field of Earth is generated by the planetâ€Ös liquid core- much
like
a bicycle dynamo, the magnetic interaction though rotation of the different
densities of liquid metal in the core produce strong magnetic fields that
protrude out from the north and south poles, enveloping the Earth with a
magnetic shield.
As the sun shines, it also emits solar radiation in the form of a constant
stream of charged particles- this ambient bombardment is known as the solar
wind.
The solar wind speed increases dramatically during sunspot activity, putting
greater pressure on Earthâ€Ös magnetic envelope. As the magnetic field
interacts with the solar wind, particles billow around the envelope towards the
poles-
the weakest points of the magnetic field- where the charged particles interact
with the oxygen and nitrogen gas in the upper atmosphere- this can be observed
visually as the Aurora Borealis and Aurora Australis.
Sporadic-E is the name designated for the unpredictable property of the
ionosphere when the solar wind travels deep and at high enough energy through
the ionosphere that it causes a plasma to occur. This plasma is conductive, and
therefore capable of reflecting radio frequency back to the ground.
This is how high frequency (HF) radio waves that would otherwise be absorbed by
the ambient ionosphere propagate great distances beyond line of sight. Although
the radio waves always travel in a straight line from the source, they can
bounce off the sporadic plasma and back towards the ground. In combination with
the ocean, this can sometimes happen multiple times before the radio wave is
intercepted by a radio receiver. This is colloquially known as radio skip.
Other forms of radio propagation such as Tropospheric Ducting affect VHF and
higher frequencies.
For the most part the F1 and F2 layers form from the separation of the radio-
absorbing D layer at night when the solar wind reduces pressure on the magnetic
field facing away from the sun, as Earth rotates from day to night- this allows
shortwave to propagate further which is why distant radio stations can only be
heard coming through in the evening hours.
Sporadic-E layers of the ionosphere are responsible for the majority of radio
propagation phenomenon at upper-HF frequencies, such frequencies as the common
CEPT and UK CB radio specification and the 10, 6 and 4 meter amateur radio band.
If you would like to view this article with pictures, the post can be found
here:
https://eindhoven.space/2021/02/03/can-i-have-a-sporadic-e-please-bob/
73 de Red PE1RRR
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