If any of you were hoping for a perfectly ordinary Thursday, you might be sorely out of luck in the best possible way. NOAA forecasters have revealed that there's a probable chance Earth will be bombarded with strong geomagnetic storms tonight, stemming from solar flares that erupted from sunspot AR2158 over the last two days. The first outflow, seen by NASA's "Solar and Heliospheric Observatory," was ejected on Tuesday, September 9th at precisely 17:46 UT, while the second one was spotted just yesterday (Wednesday, September 10th).
When the Sun unleashes its fury in the form of highly powerful CMEs and solar flares, it's possible for certain radio frequencies to be interrupted for a short period of time. Such was the case here. The X1.6-class solar flare was so powerful, it disrupted high frequency radio communications for well over an hour. As scary as that sounds, believe it or not, despite the fact that almost 100 million miles (160 million km) separate Earth and the Sun, this happens more often than you might expect. To quote one of our articles:
"Events this powerful, classified as R3 on NOAA’s Scale for Radio Blackouts, occur about 175 times per solar cycle. So while not common, these events aren’t entirely rare either."
“High Frequency” officially refers to radio waves between 3 and 30 mega Hertz (1 MHz = 1 million cycles per second). These waves can be reflected by the ionosphere, the layer of Earth’s atmosphere between 85 and 600 km in altitude. Radio signals can thus be “skipped” along the atmosphere like stones on a pond. This has historically been one of our primary modes on intercontinental communication and is widely used today for aviation, government time stations, weather stations, and amateur radio, among other things."
"Solar storms interrupt these communications by altering the properties of the ionosphere, which happens in two basic ways. The first, which caused the radio blackouts last week, is simply due to the high-energy radiation from the flare. X-rays bombard Earth, knocking electrons off atoms in the ionosphere. This creates an abnormally high density of free electrons in the lower ionosphere and is referred to as a Sudden Ionospheric Disturbance. High frequency radio waves are absorbed by this increased density, which blocks the "skipping" property and results in a complete blackout of HF communications for minutes to hours."
[Reference: "Why Solar Storms Cause Radio Blackouts"]
What's more is that not only did the most powerful ejection of the two affect our technology, but it also triggered something called "radio noise," This refers to a phenomenon that generates a static noise picked up by shortwave receivers. This particular instance was noted by radio astronomers positioned within the U.S, and some stationed all the way across the Pacific Ocean. Thomas Ashcraft — an amateur radio astronomer from New Mexico — released a three-minute clip of the noise recorded from his own radio observatory. "It was absolutely howling," he said. He certainly has something to compare it to, as he has spent over two decades listening intently for radio activity.
Back to the subject: NOAA gives an 80% chance that, when these flares meet Earth's atmosphere, they will spark intense geomagnetic storms, which would likely include bright aurorae that can be seen at mid-latitudes leading up to the weekend. Per NOAA, "Radio emissions from shock waves at the leading edge of the CME suggest that the cloud tore through the sun's atmosphere at speeds as high as 3750 km/s. That would make this a very fast-moving storm, and likely to reach Earth before the weekend. Auroras are definitely in the offing. Stay tuned for a more detailed forecast in the hours ahead."
WATCH: X1.6 solar flare from AR2158 (10th of Sept 2014)