On November 18, and following the rotation of the Sun, a large group of spots began to appear on the northeastern limb of its disk. As the Sun rotated, this group of sun spots was quickly followed by other similar ones, generating a gigantic group 200,000 kilometers in size, equivalent to more than 15 times the size of the Earth.
As a consequence, solar observation satellites soon detected solar flares (very directional emissions of radiation) coming from these regions of the Sun. Although, and until now, these flares have been classified as low and medium intensity, astronomers They do not rule out the possibility that higher category phenomena may occur in the coming days that could affect radio communications in some areas of the world and, in the worst case, some electronic equipment.
The rotation of the Sun (our star completes one revolution in about 27 days) has meant that, in the last week, this enormous group of spots has progressively rotated, now facing the Earth. This fact is relevant, since solar spots are frequently associated with the appearance of flares and coronal mass ejections.
Solar flares emit powerful streams of electromagnetic radiation (light) at different wavelengths, ranging from radio waves to gamma rays and visible light. Their classification is carried out based on the intensity of radiation in the X-ray range: ordered from most to least energetic, classes X, M and C have been described. The most worrying, class X, are of great magnitude. and they have a high probability of affecting radio communications and can even damage satellites.
For their part, coronal mass ejections launch enormous amounts of material (mainly electrons, protons and helium nuclei) into space at high speed. Although the Earth's magnetic field captures most of these particles before they reach the surface, if the flow generated by the coronal mass ejection is too intense it can give rise to geomagnetic storms capable of affecting some electronic equipment, such as power plants. electricity production. Typically, but not always, coronal mass ejections follow a solar flare.
The sunspot cluster is composed of different sets in a mosaic configuration. The main of these groups have been designated AR3490, AR3491, AR3492, AR3495, AR3496 and AR3497. Globally, they occupy an immense region of the solar photosphere (the equivalent of the surface of the Sun) with a size of approximately 200,000 kilometers and, in recent days, class M and C flares have been recorded from these macules.
Astronomers have also detected large loops of plasma developing over some of these spots. These loops, called solar prominences, are structures that lift very dense concentrations of material from the surface of the Sun towards its corona (an external region that is much hotter), and usually take on a filamentary shape. Specifically, prominences have been identified that have reached a height of up to 64,000 kilometers, which is equivalent to five times the diameter of the Earth.
Although flares and coronal mass ejections have always existed, it is now that they acquire greater importance due to the consequences they can have in a highly technical world. Therefore, observing the Sun, with satellites and other specialized instruments, is essential.
However, predicting with certainty the appearance of these phenomena is a complex task and currently only probabilities can be handled.
At this time, and for the aforementioned grouping of spots, some predictions point to a 5% probability that a class X flare will occur in the coming days. And for the less intense classes (and, therefore, less worrying) a 20% probability is estimated for a medium category flare (M) and a 65% probability for a class C flare (the weakest type).
The activity of the Sun, measured by the number of spots that appear on its surface, varies periodically in cycles of about 11 years, a fact that has been known since the 19th century. A solar cycle begins with a minimum in the number of spots, gradually develops to a maximum, and then decreases again toward the end of the period. These solar cycles have been numbered consecutively since the first one described in 1755.
The current cycle is number 25 and began in December 2019. At that time, some organizations such as the National Oceanic and Atmospheric Administration of the United States or NASA itself estimated that it would be a not very intense cycle and that the The maximum would be in July 2025, at which time the number of monthly sunspots would be around 115.
The reality is, however, that the Sun is showing much greater activity than expected and in July it reached 160 monthly spots. Last October, the value stood at 99, still above the expected figures. Everything seems to indicate, therefore, that we are in a cycle of unprecedented intensity in the last 20 years and that the moment of maximum could take place earlier than expected, in 2024. Of course, this greater activity leads to an increase in the risk of solar storms.
The most intense geomagnetic storm on record occurred in 1859. Known as the Carrington event, it blocked telegraph service between Europe and the United States for days and even caused fires in some power plants. The northern lights that developed as a result of the event could be observed even near the equator. If a solar storm of this intensity were to occur today, its effects could be catastrophic for our technology.
We have much more recent cases, although fortunately not so extreme. In March 1989, Canadian Quebec was deprived of electricity for hours, and the same thing happened in November 2003 in large parts of Sweden.
And in July 2012, a large coronal mass ejection was about to reach our planet, which would have had global consequences on satellites, communications and electronic equipment. Some experts have estimated that it would have taken between four and ten years to recover from the damage.
Another effect produced by the arrival on Earth of particles launched into space by coronal mass ejections is the increase in the number and extent of auroras.
These electrically charged particles are captured by the Earth's magnetic shield and many of them are driven towards the poles. There they interact with the air molecules in the upper layers of the atmosphere, transferring part of their energy to them, and the result is the emission of light that we know as auroras (boreal in the north and austral in the south).
In recent weeks, and in line with the increase in solar activity, auroras have been observed in rare places, even in southern Europe (for example in Spain, Italy or Portugal).
