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Grex Tutoring Item 5: solar interference
Entered by brenda on Fri Sep 2 06:45:04 UTC 1994:

Just exactly why does solar activity interfere with EM transmission?
I know it does, but never understood why.

9 responses total.

#1 of 9 by rcurl on Fri Sep 2 18:06:33 1994:

Solar activity can help or hinder EM transmission. Extreme UV ionizes
the F layer, which permits the use of higher frequencies for long
distance communication. UV and X-rays ionize the D layer, leading to
absorption of HF signals, and decreasing them. Charged particles enter
primarily the polar regions, and cause magnetic storms, auroras, and
increased EM absorption. (In a nutshell....)

#2 of 9 by dang on Fri Sep 9 20:34:39 1994:

Wouldn't there also be just plain increased backround and interferince? 
Or does our sun not emit any of those frequencies?

#3 of 9 by rcurl on Fri Sep 9 21:51:29 1994:

That's a good question. I think that the sun is "radio quiet" because
its high temperature causes ionization, which creates a good *shield*
for RF. But there must be some RF, although I don't know of anyone
noting a diurnal solar RF cycle.

#4 of 9 by dang on Mon Sep 12 18:16:13 1994:

Well, if I get a chance I'll ask Mr Taylor.

#5 of 9 by zook on Sat Oct 15 19:19:57 1994:

I believe the sun is a strong RF emitter.  I would expect it to be
because of the "black-body" radiation principle.  While (based on its
temperature) it emits strong UV energy, it is such a bright source that
it sends significant Joules in other frequencies, especially lower ones
like RF.  I could think of a number of reasons why it would emit
interference-generating stuff - first direct RF emission, second solar
wind inducing electromagnetic interactions with the Earth's magnetic
field third Cerenkov radiation from trapped ions in Earth's magnetic/
gravitic fields.  I'm sure disruption of the smooth ionic surfaces in
the atmosphere (which act like mirrors) is also a good explanation.
Someone might want to double-check all this - it's been ten years since
I've had to think about this.

BTW, proof is in the pudding.  Try listening to AM radio in the daytime
and at night and see how many more stations you pick up at night.
Also, presence of solar flares and sunspots correlates with increased
interference.

#6 of 9 by srw on Sun Oct 16 16:24:01 1994:

The reason you pick up more AM stations from farther away at night has
little too with RF interference from the Sun. Rather it is caused by
a diurnal change in the altitude of the Heaviside layer, which reflects
these AM signals back to Earth.

#7 of 9 by jcparis on Thu Mar 2 16:17:14 1995:

help

#8 of 9 by aruba on Fri Mar 3 01:53:51 1995:

Hi Jean-Claude, welcome to the Tutoring conference!  Try "write help" to get
ahold of a real live person to help you.

#9 of 9 by kami on Fri Mar 3 05:52:45 1995:

what kind of help would you like, other than in using grex?

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