Aurora borealis in Ukraine: When to wait for the next one?

After the full-scale invasion of the Russian invaders and the recent bolide over the Kyiv region, it is probably already difficult to surprise Ukrainians with something. But on the evening of April 23, an unusual crimson glow began to flare up in the northern part of the sky — the aurora borealis, which became an “echo” of a powerful solar flare. Since the sky over the entire northern part of Ukraine was clear, millions of people could see an unusual phenomenon for our latitudes.

Artificial illumination prevented us from fully enjoying the spectacle of the aurora borealis on April 23 in Kyiv. The author of the photo is Oleksandr Chubukov (Kyiv Club of astronomy enthusiasts “Astropolis”)

M-class solar flare occurred on April 21, 2023, in the NOAA 3282 group of spots and was accompanied by a significant coronal mass ejection. A powerful stream of charged particles (mainly protons) “went” from the Sun into outer space, on the way of which our Earth occurred. In fact, our luminary constantly throws out such particles, this phenomenon has even been called the “solar wind”. But they are successfully “intercepted” by the earth’s magnetic field at altitudes of about 400 km.

During solar flares, high-energy particles appear in the solar wind, capable of “getting closer” to us. According to the laws of electrodynamics, it is easiest for them to do this in the area of the earth’s magnetic poles, which do not coincide with geographical ones (and constantly change their position), but in our era they are not very far away from them. At altitudes of about 200 km, these particles begin to collide with atmospheric gas atoms. At the same time, energy is released in the form of electromagnetic radiation. We see it as the Aurora borealis.

The “Auroral Oval” is a section of the Northern Hemisphere of the Earth. The aurora borealis was observed over it on April 23. In fact, due to the glow occurring at altitudes up to several hundred kilometers, it is visible on a much larger area. 

The flow of charged particles carries with it its own magnetic field interacting with the Earth’s field, and when it “meets” powerful coronal ejections of solar matter, phenomena known as geomagnetic storms occur when the Earth’s magnetosphere contracts, and particles (especially the most high-energy ones) are able to enter the atmosphere of our planet not only in northern latitudes, but also in temperate, and sometimes even in tropical. The event on April 23 was assigned an index of 8 on a 9-point scale, so it was one of the most powerful magnetic storms of the current 25th cycle of solar activity, which began in 2020. It was not surprising that auroras were observed during it in the north of Ukraine and even in Bavaria.

On the opposite side of the planet over the island of Tasmania on the morning of April 24, an aurora was also observed, caused by a coronal mass ejection. A bright meteor also got into the picture. Source: @mantisalive

Group NOAA 3282 is located north of the solar equator. Due to the rotation of the Sun, it has already gone beyond the visible edge of its disk and will reappear in the field of view of ground observers in about two weeks. It is unlikely that this particular group will be the source of an equally powerful coronal ejection “directed” to the Earth. But a similar release can occur in other active areas on the surface of the luminary. At least until the end of 2024, its activity will grow, so we can assume that before that time we will still have the opportunity to see the aurora borealis from the territory of Ukraine — it is possible that it will be even brighter and more powerful than the one that has decorated our sky on the evening of April 23. However, it will be possible to predict its appearance only immediately after the solar flare “responsible” for it.

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