The solar activity cycle arises from the flipping of the sun's magnetic poles. Tõnis Eenmäe, a researcher in astrophysics at the Tartu Observatory, explained that the magnetic poles switch approximately every 11 years: the north pole becomes the south pole and vice versa. It is during the middle of this cycle that solar magnetic activity is at its highest, resulting in more sunspots and the most frequent occurrence of large eruptions.

"Since the Sun is a gaseous body, it rotates at different speeds at different latitudes. When the Sun rotates at different speeds at the poles and the equator, the magnetic fields become very distorted. Various magnetic processes start occurring, which astronomers refer to as solar activity," Eenmäe told ERR.

Eenmäe noted that when magnetic fields break, reconnect or recombine in some areas, this often leads to solar flares. During such eruptions, a large amount of material is released from the star and scattered into space, creating what is known as the solar wind. This cloud of charged particles is quite large and sparse and can sometimes collide with Earth.

"When particles from the Sun reach Earth, the planet's magnetic field protects us from them. However, near Earth's magnetic north and south poles, it's possible for these particles to reach the upper layers of the atmosphere and collide with oxygen and nitrogen atoms there. They excite these atoms, giving them energy," the astrophysicist explained.

"The atoms usually try to give away this energy quickly and emit light of different wavelengths in the process, which we recognize as light of different colors. That's how auroras are created," he added.

According to Eenmäe, the last solar minimum occurred at the end of 2019, when there were almost no sunspots visible on the Sun. It should be noted that sunspots and magnetic events are strongly related. "Currently, sunspots can be seen almost all the time," he said. The predicted maximum of the solar activity cycle is expected to fall in 2024 and 2025.

According to Tõnis Eenmäe, auroras actually occur in Estonia a couple of times a week. Most of the time, they are simply not very visible to the naked eye. "These are mostly weak auroras that often go unnoticed by the human eye, or if noticed, they appear pale, whitish in color and low in the northern sky. The auroras are there, but it's not a particularly spectacular sight. In cities, they are not seen at all," the scientist pointed out.

In his estimation, clearly visible, colorful auroras may occur maybe a few times a month. "Moreover, the auroras that caught people's attention last Sunday are not even the strongest that can occur in Estonia. For example, last spring, there were much stronger ones in Estonia," Eenmäe mentioned.

Look for auroras around the spring equinox

To encounter the Northern Lights, photographer and aurora enthusiast Kertu Kosk recommends using the internet for assistance. On a promising evening, one should keep an eye on websites like Virmalised.ee or SpaceweatherLive.

There are also social media groups that share information, and mobile applications available that forecast aurora appearances. "These provide a rough prediction, but whether the auroras will be stronger or weaker, they don't particularly forecast. On those evenings, you just need to keep an eye on the groups and go for a walk outside," Kosk said.

Particles emitted from the Sun usually reach Earth within three days, and thus, applications rely on the American NOAA satellite data for three-day forecasts. "They base it on whether there's an event happening on the Sun. If something departs from the Sun, they start predicting whether our planet will get hit by it. Since Earth is relatively the size of a pinhead in comparison to the Sun, there's a high likelihood that the burst will miss," she noted.

According to Kosk, no one was able to predict Sunday's strong aurora display in advance. "They knew something had left the Sun, but I haven't checked yet whether they predicted it would miss us or didn't consider it to be very strong. We only foresaw Sunday's display when it reached the satellites," Kosk said.

Another common mistake that beginners in aurora watching often make, according to Kosk, is going outside for too short a time. "For example, on Sunday night, there were three to four stronger displays. There are always pauses in between when the sky calms down. If you go outside at that moment and wait for about half an hour, you might get the impression that there are no auroras at all," she observed.

According to Kertu Kosk, the aurora viewing season typically lasts from September to the end of April. This is the time when auroras should be most visible to the naked eye. However, if there is a very strong aurora display that reaches southward from Estonia, Kosk notes that it's possible to see them even in the summer. The sky is usually darker towards sunset.

The best time for aurora viewing in Estonia, in Kosk's estimation, is around March 20. "It is the lovely time of the spring equinox. Our home planet is at such a favorable angle to the Sun at that time, which maximizes the likelihood of seeing auroras. Also, the Earth's magnetic field is somewhat more fragile then," Kosk summarized.

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