As millions of people look up at the sky, the moon temporarily (and completely) blocks the sun during this period. Total solar eclipse on April 8New data shows that this extraordinary cosmic event also changed the invisible “time signal” beamed from the United States around the world.But don’t worry, these signals of change won’t cause any changes time We conducted observations during or after the event.
The offset time signal comes from WWV Radio, a National Institute of Standards and Technology (NIST) facility in Fort Collins, Colorado that monitors and broadcasts high-frequency signals radio waves.
WWV, co-operated by NASA’s Amateur Radio Citizen Science Survey (HamSCI), continuously broadcasts special signals embedded with “digital time code” to millions of receivers around the world.The device receiving the signal interprets the digital codes embedded in the transmission and uses them to stay in sync with NIST atomic clockit is the gold standard for all American timekeeping.
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In order to do this, however, the signal must bounce off the ionosphere—the upper layer of the atmosphere 50 to 370 miles (80 to 600 kilometers) above the Earth’s surface where gases are converted into plasma,according to NOAA.During a lunar eclipse, the ionosphere changes slightly as the moon shadows Traveling across the United States at speeds in excess of 1,500 mph (2,400 km/h).
As a result, the frequency of the signal reflected from this part of the atmosphere changes slightly. Originally reported by Spaceweather.com. Similar frequency shifts appear in other radio signals sent or received by amateur radio operators across the country. HamSci reports.
Fortunately, the change in the frequency of the WWV signal is so small that the digital time code transmitted by the radio waves is not altered, meaning devices that rely on the signal to keep time are not affected, according to Spaceweather.com.
Radio waves from other major time sign stations around the world, including WWV’s sister station WWVH in Hawaii, were unaffected by the eclipse.
“Quick Turn to Darkness”
The shift to a WWV signal is called a Doppler shift and occurs when the distance the signal must travel increases or decreases. These changes can stretch or truncate the wave, thereby changing its frequency and wavelength.
Similar Doppler shifts occur naturally at least twice every 24 hours as the sun rises and sets, Christina Collins a researcher at the Space Science Institute in Boulder, Colorado (radio call sign KD8OXT) told Live Science in an email. “Every day, light from the sun causes photoionization in the ionosphere, causing the ionosphere to move, coalesce, or separate.”
Starting at sunrise, Collins said, this causes the ionosphere to expand, meaning radio waves don’t travel as far before being reflected by this invisible barrier. But she added that when the sun sets, the ionosphere shrinks, allowing signals to travel farther before bouncing back to the surface. Therefore, radio signals have to travel farther at night, which slightly increases their wavelength.
The same thing happens during a solar eclipse’s “rapid turn to darkness,” Collins said. “Essentially, it’s like a microcosm of the day-night cycle.”
Similarly, less extreme Doppler shifts may also be caused by changes in solar activity, including large gusts of solar wind, explosive solar flare and coronal mass ejectionCollins added that when they bombard our planet, they all change the Earth’s ionosphere.
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