Subj: [Fwd: [Fwd: Eclipse 11 August 1999]]
Date: 8/9/99 6:52:11 AM Pacific Daylight Time
From: cplyler@i-america.net (Charlie Plyler)
To: geo-seismic-labs@bigfoot.com (Frank Condon)
CC: Phikent@aol.com (Kent Steadman)
Here is some more on the coming eclipse and the monitoring
opportunities.
Charlie
Hi Charlie,
I don't remember if I sent this News release I received from NASA
to you or not. If so, disregard, otherwise you might find this of
some interest to your efforts. I don't recall if we discussed ham
radio in our earlier correspondence. I have been an amateur operator
since I was 13 - Boy is that ancient history. Don't recall if you
are also into ham radio.
I am going to monitor various HF frequencies prior to, during & after
the eclipse. I have been busy putting together an antenna for the
effort. The results of all the work that is going into this global
monitoring & recording effort should prove interesting and beneficial.
>From an elfrad point-of-view, do you plan to do any analysis of any
effects the eclipse may have on RF reception for elfrad? Hope all is
well with you.
Warren Holdenbach
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"NASA, astronomy, sun, aurora, Headlines, News, space, plasma,
solar, basic research, science news, Marshall" "Hams around the
world can track the 11 Aug 1999 total solar eclipse by monitoring
its effects on radio propagation."
Audio Eclipse May Fill the Sky
4 August 1999: During a total solar eclipse, day becomes night for
a few precious minutes the temperature drops, birds stop singing,
& bees return to their hives for a premature rest. An eerie quiet
envelopes the landscape inside the path of totality.
However, from the unique perspective of a ham radio operator,
night is anything but quiet - and neither is a solar eclipse.
Many shortwave radio stations that are undetectable in daytime
are easy to pick up at night. The reason has to do with the Sun's
effect on Earth's atmosphere. During the day, solar UV radiation
ionizes atoms and molecules in the upper atmosphere, creating a
zone called the ionosphere. The uppermost part of the ionosphere,
called the F layer, is so thoroughly ionized that some free
electrons exist there - even at night - when the UV source (the
Sun) is not present. The F layer is like a mirror for radio waves
with frequencies below 20 MHz. Shortwave transmissions from earth
hit the F layer and bounce back down.
In fact, many such bounces can occur, and this is the reason
why over-the-horizon transmissions are possible at short wave
frequencies.
Interestingly, the ionosphere - so important for long distance
radio communication - can also dampen radio waves. In the D and E
layers the degree of ionization is not as great as in the F layer.
Partial ionization cause these layers to act more like a resistor
than a mirror.
Short waves passing through them are attenuated rather than
reflected. Signals at some frequencies are damped out altogether.
Fortunately, the level of ionization in the D layer is small, and
when the sun sets at night, all the molecules and free electrons
can recombine, and the D layer disappears! Stations that were
damped out during the day can then propagate around the world.
This well-known atmospheric ritual takes place every day. On 11
August 1999 it will happen twice.
As the path of totality slices through Earth's atmosphere, ions
& electrons in the vicinity of the shadow will begin to recombine.
The reflecting F layer may not be greatly affected, but ionization
in the attenuating D layer could vanish. Shortwave radio stations
that were restricted in range to sites in Europe just moments
earlier may be able to skip over the horizon and be heard on the
other side of the Atlantic.
Solar Disk Jockeys - Scientists at NASA/Marshall are putting this
phenomenon to the test by inviting Science@NASA readers to become
Solar Disk Jockeys, who will report the effects of the 11 August
solar eclipse not by watching for it, but by listening for it.
Since England and middle Europe offer unpredictable visual
conditions, the audio eclipse may prove the most reliable
observation, particularly when heard from thousands of miles away.
The BBC World Service will be a good choice for many radio
listeners. BBC transmitters are located mostly in the UK
relatively near the path of totality, and they transmit at
frequencies between 5 and 15 MHz that are favorable for probing
changes in the D-layer.
The table, below, shows BBC frequencies and suggested monitoring
times. Europe's VOA transmitters may also be suitable. A List of
Voice of America (VOA) frequencies for Europe is given at -
http://www.voa.gov/europe.html.
This table lists short-wave frequencies for the
HREF="http://www.bbc.co.uk/worldservice/index.shtml"
British Broadcasting Corporation (BBC) world service, whose
transmitters are located relatively near the path of totality.
The table suggests the times are in Universal time when hams may
detect the clearest trasnmission during the eclipse event.
(HREF="http://tycho.usno.navy.mil/"
HREF="http://www.voa.gov/allsked.html">European VOAtransmitters
may also be interesting. Ham operators should experiment before
11 August to select frequencies to log during the eclipse.
Interested readers should use their shortwave receivers to
experiment with different stations. The best ones for eclipse
listening will be transmitters that can be heard at night, but not
at all during the day. The eclipse will begin over Europe around
10:10 UT when it is still night over most of North America. Thus,
when the daytime ionosphere begins to diminish over Europe, there
is a good chance that European shortwave broadcast stations will
be able to propagate great distances into the Western Hemisphere.
5 August: There Goes the Sun 4 August: Audio Eclipse May Fill the
Sky 3 August: Turning blueprints into watercolors
31 July: Farewell, Lunar Prospector
Recording useful data is easy: Simply note the following info: The
station's signal strength as displayed on the receiver's VU meter
at night and during the local time of the eclipse for a week
centered on Aug 11. Then email your logs, your audio recordings
(if any), and your position (latitude and longitude) to Marshall
Space Flight Center's
Eclipse mailbox. The data will be analyzed to help determine
ionospheric properties & used for a future story from Science@NASA.
A map of expected changes in radio MUF (maximum usable frequency)
caused by the August 1999 solar eclipse. The striking aspect of
these University College London simulations is that changes are
global, not local to the path of totality. With times shown at
top, the numerical simulation, performed by University College,
London, will be used to support a collaborative experiment between
UCL & the Rutherford-Appleton Lab, in which radio signals between
Spain & England will probe the eclipse on selected MW frequencies
and radios tuned by the public.
HREF="http://www.wdc.rl.ac.uk/ionosondes/eclipse/science.html">
More information from Rutherford-Appleton Labs
A total eclipse of the Sun is about as close to a controlled
experiment as atmospheric research can hope for. Marcos A.,
Penaloza M. Univ of Essex, Institute for Environmental Research.
The possibility of listening; to the August 1999 eclipse from afar
has more than novelty value. Scientists are interested, too,
because the results of a global monitoring experiment could give
them new insight into the physics of the upper atmosphere.
Radio Heaven -
In the last 1000 years, the 25th most significant human event was
the first over-the-horizon radio transmission, according to Life
Magazine's millennium edition: a 2,000 mile space broadcast of the
Morse code letter, carried from a kite in Italy to a receiver in
N.Y. In 1999, there are 4 million amateur radio operators in
the US alone, and they continue to increase around 7% per year.
As the Moon's shadow moves across the earth, temperature in the
upper atmosphere will drop, changing wind patterns as air contracts
in on the eclipse region. In the absence of UV radiation from the
Sun, the ionosphere rapidly begins to decay. The shadow of the
moon races through the atmosphere at supersonic speeds, causing
wind & waves of electron-ion recombination to spread through the
atmosphere from the eclipse region. The effects could be global.
All these phenomena have been predicted by theory & some have been
observed during previous
eclipses. On 11 August scientists & amateur radio operators will
attempt to refine physical models of the ionosphere by attempting
to monitor changes in the D layer absorption of radio beacons.
The public is invited to participate (see related links)
Theoretical physics will benefit from an improved understanding
of the ionosphere, and so will radio broadcasters. In many
atmospheric models attenuation of the D layer is overestimated,
with the result that radio transmitters are often operated at a
higher power than necessary. This, in turn, costs money, wastes
energy, and pollutes the already cluttered airwaves with more RFI
(radio freq interference).
Improved models of RF ionosphneric absorption could lead to lower
power broadcasts during the day. With measurements of absorption
obtained during the eclipse, scientists & engineers hope to have
a better understanding of the nature of ionospheric absorption
which may ultimately lead to less interference in the future
(quote from Rutherford- Appleton Lab, UK.)
Calling All Solar Disk Jockeys -
For sky watchers in North America and other areas not touched
by the path of totality, August 11, 1999 offers a unique
opportunity to sense the eclipse from a distance (or perhaps from
beneath a cloud if you live in Britain). Science@NASA encourages
readers to tune into the eclipse using shortwave radios and to
report their results for scientific analysis.
HREF="mailto:eclipse@msfc.nasa.gov">
Reader suggestions concerning appropriate frequencies & observing
procedures are welcomed & will be distributed to other Solar Disk
Jockeys prior to totality.
Science@NASA will need the following information for a meaningful
record of observations.
a) the frequency of the radio station(s),
b) the station's signal strength(s) as displayed on the receiver's
VU meter at night and during the local time of the eclipse for
a week centered on Aug 11,
c) your location (latitude and longitude).
Send these logs and your audio recordings (if any) to Marshall
Space Flight Center's Eclipse mailbox.
HREF="mailto:eclipse@msfc.nasa.gov"
The data will be analyzed to help determine ionospheric properties,
and used for a future story from Science@NASA.
For more info about the 11 Aug 1999 solar eclipse, please visit
Goddard Space Flight Center's Solar Eclipse home page.
HREF="http://sunearth.gsfc.nasa.gov/eclipse/eclipse.html"
External Web Links
Radio frequencies
reference - Voice of America's European stations - HREF =
"http://www.williams.edu/Astronomy/IAU_eclipses/atmospheric.html"
Project for study of Atmospheric & Ionospheric effects - prepared
by Marcos & Penaloza at the Institute for Environmental Research
Central Campus. England, U. K.
Rutherford-Appleton Laboratory (UK) research on eclipse effects:
HREF="http://www.wdc.rl.ac.uk/ionosondes/eclipse/">
Upper atmospheric research during the eclipse - R.A. Lab's home
page for the upper atmospheric research during the 11 Aug eclipse
HREF="http://www.wdc.rl.ac.uk/ionosondes/eclipse/temperatures.html
- Temperatures in upper atmosphere
- Temperature variations at 240 km during an eclipse
Atmospheric winds during an eclipse
HREF="http://www.wdc.rl.ac.uk/ionosondes/eclipse/waves.html">
Wind and Waves - in the ionosphere during an eclipse
HREF="http://www.wdc.rl.ac.uk/ionosondes/eclipse/PUST.html">
Public participation - Public opportunities, through R.A. Lab to
participate in measuring eclipse effects.
Further reading:
1. Journal of Atmospheric & Terrestrial Physics Volume: 38 Page:
May 1976 Meisel, D. (N.Y. State Univ) Duke, B. (Canadian Broad-
casting Corp.) Aguglia, R.C.(Buffalo Museum of Science) Goldblatt,
N. R. (Rochester Institute of Technology) p. 8
2.Zokolov, L. E. Legen'ka, A. D. Pulinets, S. A. (IZMIRAN)
Geomagnetizm i Aeronomiia Volume: 33 Issue 1 Pages 49-57
01 Feb 1993
3. tseva, N. A. Elanskii, N. F. Matveev, A. D. Vartanian, V.
Meteorologiia i Gidrologiia Page: 45-50 Jun 01, 1984
More Space Science Headlines
- NASA research on the web
HREF="http://spacescience.nasa.gov/">
NASA's Office of Space Science press releases & other news related
to NASA and astrophysics - Science Notes from Previous Eclipses -
A multifrequency sounding experiment bounced high-power radio waves
off the Earth's atmosphere during the 10 July 1972 eclipse, and a
research team led by N.Y. State Univ & the Canadian Broadcasting
Corp found: A correlation of very low frequency (VLF) phase, high
frequency (HF) signal strength, & geomagnetic field behavior on
eclipse day.
For the 18 March 1988 eclipse, a vertical sounding experiment
bounced signals between Japan and Russia and indicated that the
uppermost layers of the ionosphere (the F2 layer) changed only
30-35 minutes after maximal phase of solar eclipse. But little
to no weather change was indicated during the solar eclipse of
31 July 1981, either for atmospheric temperature or ozone.
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