On the night of May 10/11, 2024, the aurora borealis became visible from the twilight period and was visible – intermittently – until dawn, which we can safely say: whoever managed to observe it had one of the most beautiful experiences of his life.
What is the reason for this extraordinary phenomenon?
The huge sunspot group (AR3664) at the right edge of the Sun gave us the solar flares that make our auroras possible. The size of the spot group is illustrated by the fact that it is more than 15 times the diameter of our Earth!
Source: Mónika Landy-Gyebnár
In the 11-year cycle of solar activity, we have reached the maximum period, at which time many more sunspots appear on our star than usual, and their size also increases. Larger sunspots can cause larger coronal ejections (abbreviated as CMEs), with which charged particles speeding at very high speeds can approach our planet, or they can run in another direction.
When these particles meet the earth’s magnetic field, they create disturbances in it, geomagnetic disturbances, one of the effects of which is the formation of the aurora borealis. On the face of our Sun, published in early May, there is a group of sunspots that grew to an amazingly large size in a few days, bearing the serial number AR3664. It is comparable in size to the one that caused the Carrington event experienced in 1859.
Coronal ejections of the X type, reaching the highest category, puffed out from the sunspot one after the other, and three of them crowded into each other reaching the magnetic field of our planet. (At the aurora borealis in early November 2023, we were able to enjoy the effects of two medium-sized CMEs.)
In such cases, of course, forecasts are made, but there are many constantly changing factors, due to which there is a lot of uncertainty in the forecasts. In this case as well, the main events were expected until Saturday dawn, but luckily for us, they already started on Friday evening.
These CMEs coming in at each other’s throats, amplifying each other’s effect, resulted in the creation of a geomagnetic storm of strength not seen since the end of October 2003 in the magnetic field of our planet.
Although the forecasts expected that the aurora borealis could be seen from significant, large areas and medium latitudes, but not for such a large magnetic storm. Geomagnetic disturbances are measured on a scale of 1-5, we have now reached level 5, the strongest magnetic storm.
The cloud cover determined where we could see the aurora borealis
In our country, the aurora borealis usually appears only in the part of the sky above the northern horizon, it is extremely rare, as it was in November 2023. Now, however, the phenomenon significantly surpassed this, they could see the dance of purple light streaks reaching the zenith (this is the top of the sky), who were kept awake by the experience.
Unfortunately, a thick cloud cover in the north-eastern part of the country hindered observation, elsewhere the clouds were only partially covered. The phenomenon began to appear after 9:00 p.m. in the then still light twilight northern sky, and from 10:00 p.m. it turned on with full force.
The aurora borealis visible throughout the night appeared in three main stages: starting after 9 pm and approx. The geomagnetic storm, which lasted until 11, started around midnight and lasted until around 2:30, then switched on again after 2 in the morning and continued until light. Around 1 in the morning, the geomagnetic storm reached level 5, at which time even those with south-facing windows could see the aurora borealis. , you only had to look up a little. In the southern states of Europe, such as Italy or Spain, the aurora borealis was also visible.
The SAR arc was also present throughout
The SAR arc is a pronounced red glow crossing the center of the panoramic image in a diagonal arc. The closer to the horizon, the purpler the aurora borealis. On the left side of the chapel, the yellowish spot of light is the moon about to set (clouds scatter its light).
Source: Mónika Landy-Gyebnár
Very similar to the case in November, the deep red SAR arc spanning the entire sky also appeared. This was not part of the aurora in the strict sense of the word, its formation is also different, but it can also be linked to geomagnetic disturbances.
The SAR arc is visible due to the excitation of atomic oxygen above 400 kilometers, and it is this high atmospheric altitude that causes it to appear further south than the usual aurora region. The name of the phenomenon comes from the English abbreviation of the arc under the aurora borealis. In general, this phenomenon is rather faint, not really noticeable with the naked eye, and most of the time it appears only on high-sensitivity photos. However, it was now easily visible in the rural sky thanks to its greater brightness.
Can another event like this be expected in the near future?
The maximum of solar activity will last for some time, so in theory we can expect strong coronal ejections and, under favorable conditions, aurora borealis. However, unfortunately, the shortness of the summer nights is also an aggravating factor.
If it is not so strong and visible all night, we may still see something similar to the one in November 2023 during the next year.
Experience shows that, at the latitude of our country, the chances of the aurora are really increased if successive CMEs are congested.