[SFDXA] The Solar Eclipse Shifted Atomic Time Signals in the USA

[Bill]

*Space Weather News for April 17, 2024*
https://spaceweather.com 
<https://Spaceweather.us11.list-manage.com/track/click?u=0c5fce34d5ca05f64a13d085d&id=f8ca569bab&e=d71faae82a>
https://www.spaceweatheralerts.com 
<https://Spaceweather.us11.list-manage.com/track/click?u=0c5fce34d5ca05f64a13d085d&id=702a2a92e6&e=d71faae82a>

*SOLAR ECLIPSE DOPPLER-SHIFTS TIME SIGNALS:* Last week's total eclipse 
of the sun did more than cast a shadow. It also Doppler-shifted radio 
transmissions of atomic time across the USA. More than a dozen ham radio 
monitoring stations measured the effect. Spaceweather.com 
<https://Spaceweather.us11.list-manage.com/track/click?u=0c5fce34d5ca05f64a13d085d&id=1e8bea434a&e=d71faae82a>.

*
*

*THE SOLAR ECLIPSE SHIFTED TIME SIGNALS IN THE USA: * The US National 
Institute of Standards and Technology (NIST) has a radio station in Fort 
Collins, Colorado. Call letters: WWV 
<https://www.nist.gov/pml/time-and-frequency-division/time-distribution/radio-station-wwv>. 
Operating at multiple shortwave frequencies, WWV broadcasts precise time 
and frequency information 24/7 to listeners worldwide. On April 8, 2024, 
the frequency of WWV shifted:

<https://spaceweather.com/images2024/16apr24/dopplershift.jpg>
This plot also contains data from WWV's sister station in Hawaii, WWVH

"It was the solar eclipse," says ham radio operator Kristina Collins 
<https://spaceweathergallery2.com/indiv_upload.php?upload_id=205561> 
(W8EDU) of Cleveland, Ohio, who assembled records from 13 monitoring 
stations in and around the path of totality. "The HamSCI 
<https://hamsci.org/> Personal Space Weather Station Network's Grape 
stations measure Doppler shift in the carrier signal of time standard 
radio stations such as WWV. On April 8th, the network saw a distinct 
S-curve signature associated with the eclipse."

The Doppler shift occured when the shadow of the Moon pierced the 
ionosphere 
<https://www.swpc.noaa.gov/phenomena/ionosphere#:~:text=The%20Ionosphere%20is%20part%20of,used%20for%20communication%20and%20navigation.>, 
creating a temporary hole where ionization was reduced. This, in turn, 
altered the "skip distance" from transmitters to receivers, as shown in 
the diagram below:

<https://spaceweather.com/images2024/16apr24/diagram.jpg>

Because the skip point was moving, reflected radio signals were 
naturally Doppler-shifted. Spaceweather.com reader and senior physicist 
Larry Carr of Brookhaven National Labs made this calculation: "Using the 
10 MHz WWV frequency, an average shift of about 1/2 Hz implies the layer 
bottom (the 'skip point') was moving at speeds up to 15 m/s. During the 
entire eclipse, the reflecting layer moved on the order of 50 km."

The total Doppler shift was only a few cycles per second, similar to 
normal night-day variations, so no one actually lost track of time 
during the eclipse. Nevertheless, it is a fascinating demonstration of 
an eclipse's power to touch the Earth.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/sfdxa/attachments/20240417/f060b283/attachment.html>