Coronal Mass Ejection Causes Radio Blackout in Arctic Circle

The Arctic Circle had a radio blackout due to a recent coronal mass ejection that created a polar cap absorption event.

Radio Blackout in the Arctic Circle

This CME has caused radio frequencies below 15 MHz to be almost entirely blacked out and the majority of frequencies below 35 MHz to be at least slightly damaged.

This polar cap absorption (PCA) event results from a coronal mass ejection that happened on May 7 and is currently crashing down the globe, according to NOAA's Space Weather Prediction Center.

Coronal Mass Ejection

Large plumes of solar plasma along with a magnetic field known as coronal mass ejections (CME) are expelled from the sun when there is high magnetic activity. These can move across space at rates of up to one million miles per hour, and some CMEs can take several days to reach Earth while others can do so in as little as 15 to 18 hours. A solar proton event, in which the sun also spews forth charged protons, can occasionally be a part of a CME.

On May 7, a long-lasting M1.5-class solar flare and a proton CME from the reversed-polarity sunspot AR3296 are likely to have been the causes of the current polar cap absorption event.

Proton Events vs. Radio Signals

When protons collide with the Earth and its magnetic field, radio blackouts can result. Polar cap absorption occurrences occur when the magnetic field directs the protons from the CME toward the poles, concentrating the radio blackout's effects there. Here, protons interact with atmospheric molecules to temporarily raise the density in the lower ionosphere, which prevents short-wave radio signals from being absorbed.

For the radio signals to go to their receiver, they must bounce off of the upper ionosphere, which is prevented by this.

Since ground-based radio networks are not in place across vast, isolated areas or oceans, these blackouts can have an impact on civil aviation by reducing long-range communications with aircraft.

The principal means by which airplanes in these regions interact with air traffic control is through high frequency, according to Mike Hapgood, an STFC Rutherford Appleton Laboratory space weather scientist. For instance, planes flying over the North Atlantic will connect with centers for oceanic air traffic control run by Canada, Iceland, and the UK/Ireland.

Hapgood added that although many aircraft carry satcom as a backup, high-frequency is required as part of internationally standardized protocols. Therefore, high-frequency blackouts can harm those linkages, but since they frequently only last a few tens of minutes, the industry can continue operating smoothly. As aircraft would then use short-range VHF radio communications, these blackouts won't have an impact on takeoff and landing.

Solar Maximum

The sun is predicted to become more active as it gets closer to its upcoming solar maximum, which is scheduled to take place in 2025. Since monitoring began in 1755, there have been 24 full solar cycles, with the current cycle being the 25th, Newsweek reports.

In hindsight, solar scientists managed to determine that Solar Cycle 25 started in December 2019 at the time of the solar minimum. Unsurprisingly, the solar maximum is anticipated to take place in the middle of Solar Cycle 25, most likely in July 2025, according to Forbes.