We could still consider the activity of the Sun to be low during October 2021 with a clear conscience. After all, in mid-October, there was hardly a major stain on the surface. What has become so fundamental that now the activity of the Sun is significantly increased and there are strong eruptions and the ejection of larger plasma clouds to the Earth?
Author: NASA/SDO/HMI
The answer is the occurrence of active areas and also groups of spots in them. These areas with spots are not always a source of strong eruptions, but at the turn of October and November, coincidentally, two groups with a relatively complicated magnetic field and thus really increased activity appeared on the surface. One was located near the center of the Sun in the southern hemisphere (AR 12887) and at that moment there was a strong eruption on October 28. promising a nice aurora borealis. Then the second one (AR 12891) turned to the center, this time in the northern hemisphere. And even here, on November 2, there was a strong eruption and subsequent outburst of matter from the corona.
It does not always happen that such eruptions with a long duration and a large ejection of matter occur at a time when the spots are near the center of the solar disk. In this case, however, this happened twice. In the images of the coronograph of the SOHO probe, we can then see a circular cloud of plasma (CME – Coronal Mass Ejection) propagating in all directions from the obscured disk of the Sun. Due to their circular shape, these phenomena have the English name “halo CME”. Such a cloud of plasma should then point directly at Earth. By the way, the previous eruption from the end of October caused a similar phenomenon, but it was not so circular, and therefore the main cloud of particles probably missed the Earth.
Author: NASA / ESA / SOHO / LASCO C3
The eruption of November 2 was significantly weaker. October belonged to the highest category X, which from the beginning of November reached only the second highest level M (exactly M 1.7). Nevertheless, we may also be quite interested in this one. Mainly because this time the ejected plasma cloud is almost circular and should really point directly at Earth. And secondly, because the earth’s magnetosphere was already reacting relatively intensely to very faint clouds, and the aurora borealis visible at high latitudes they were really nice. We could already observe aurora borealis from the Czech Republic even after eruptions of C9 (almost M1) or M4 (for example, a huge glow on November 20, 2003).
Autor: Space Weather Prediction Center
So what can be the next development? The cloud of particles is now back on Earth. Although the speed of its movement should exceed 500 km / s, it will take him about three days to reach our orbit. Along the way, he will also meet some of our envoys. The ACE, SOHO or DSCOVR probes monitor space weather (ie the flow of charged particles from the Sun, the so-called solar wind). SOHO also sent us an animation of that circular “halo” CME. The ACE probe, in turn, provides us with a live graph of various solar wind parameters. And as we wrote on Saturday, this probe will be the first to feel if and when a cloud of matter has arrived. And we on Earth will feel about half an hour late.
Thus, if the eruption in the active region of AR 12891 occurred on November 2 around 3:50 CET, it can be expected that the plasma cloud will reach the Earth after about two to three days, ie sometime during Thursday, November 4, or Friday, November 5. Moreover, it is not the only plasma cloud. On the way, it is even weaker after the eruption from the active region of 12887. On the other hand, a cloud of matter can be aimed a little above the plane for a change, where the Earth orbits and only its edge hits us again …
Again, it is especially important to wait and hope that
- the shock wave in the solar wind really arrives
- arrives at the right time (preferably at least in the afternoon, or preferably during the night)
- it will be clear somewhere (in inverse weather, eg in the mountains)
- the magnetosphere does react and aurorae form
- that the glows will be so beautiful that they will appear at least very low above our northern horizon
On the night of Sunday 30/31, we waited in vain for a nice aurora borealis. There were only two major vibrations, which evoked a nice aurora borealis visible best at latitudes above 60 °. So such a glow could not be seen in our country. Or would it just? There was some hope. But it would have to be extremely low above the horizon. Such news and photographs came to me from an experienced solar observer and aurora hunter. However, such an observation is probably not what we are waiting for.
If we want to see aurora borealis reaching at least ten, or better than 20 ° above the horizon, we will have to be very lucky. Such a strong geomagnetic storm is not really expected after this eruption. But the weekend has shown that we can be wrong in both directions. With aurora borealis, it’s like comets. Predicting their behavior is difficult, and once they fail, other times they are surprised. Maybe this will be the case.
Resources and recommended links:
[1] Previous article on aurora prediction
[2] Solarham.net portal dedicated to solar activity
[3] Spaceweather.com, among other things, about space weather
[4] NOAA solar wind forecasts
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