SpaceWeather.com Archive — Wed, Apr 17, 2024

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ANOTHER CME IS COMING: A faint CME left the sun on April 15th, the result of an M-class solar flare from sunspot AR3639. A NASA model predicts it will hit Earth's magnetic field on April 18th. The CME's impact could spark a G1-class geomagnetic storm with auroras at high latitudes. Aurora alerts: SMS Tex t

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. 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:

This plot also contains data from WWV's sister station in Hawaii, WWVH

"It was the solar eclipse," says ham radio operator Kristina Collins (W8EDU) of Cleveland, Ohio, who assembled records from 13 monitoring stations in and around the path of totality. "The HamSCI 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, 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:

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.

more data: from Neil Miller of Aiken, SC

Realtime Solar Eclipse Photo Gallery
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18K GOLD TOTAL ECLIPSE PENDANT: This pendant has touched the shadow of the Moon. On April 8, 2024, during a total eclipse of the sun in Texas, the students of Earth to Sky Calculus launched it to the stratosphere onboard a cosmic ray research balloon. Floating more than 118,110 feet high, the locket spent 3 minutes and 45 seconds wrapped in lunar shadow:

You can have it for $199.95. The 18K gold-plated locket is inscribed with the words "I love you to the Moon and back," and opens to hold a personal photo or other small item. It comes with a greeting card showing the locket in flight and telling the story of its journey to the edge of space during the total eclipse.