Solar activity grows and causes some radio blackouts in Asia and Australia

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Solar flares a few days ago caused some radio blackouts in Asia and Australia.

However, we are still far from the maximum solar activity expected for July 2025.

sun awakening

The past period of low solar activity, which lasted more than a year, caused some concern.

It was even thought that a very long period of solar hibernation could have some influence on the Earth's climate.

However, during the last few weeks, the Sun is recovering a level of activity that signals the end of its period of rest.

The images captured of the Sun during these last days reveal

on the surface of our star: sunspots, bulges, flares and holes in the corona.

Sunspots of April 25.Ramon Delgado/Astroguada

In fact, since September 2020, sunspot counts

, suggesting that we could be in for an unusually intense cycle of activity.

cycles

Solar activity is measured by the number of visible sunspots: the so-called Wolf number.

This number varies periodically, following a cycle of approximately 11 years (the duration of the cycles can range from about 9 to 13 years).

, it is the solar minimum.

But little by little, spots begin to appear at high solar latitudes, which then multiply and spread towards the equatorial regions, until the solar maximum is reached.

Studying the evolution of sunspots is extremely important because these are the ones that cause flares and solar eruptions.

When the sunspot cycle reaches its maximum, the Sun is at its most active, and that is when

, which, if directed towards Earth, can damage the high-tech systems on which we depend so much. .

Solar cycles

.

Cycle 1 was called the period 1755-1766 and, from then until now, 24 cycles have been completed.

cycle 25

The most recent solar minimum took place in 2019: during a period of 274 days the Sun did not have a single spot, thus concluding Cycle 24. In December 2019 Cycle 25 began,

.

Evolution of sunspot number. NOAA

The trend observed in recent weeks points to more intense activity than expected.

The attached image of the Sun taken on Monday April 25 from Guadalajara by amateur astronomer Ramón Delgado (from the Astroguada association) shows the group of spots labeled AR2993.

This group produced a double flare of moderate size (type M, in astronomical jargon) that caused blackouts in several communication systems in Asia and Australia.

The previous week

(class X) but, fortunately, this one was not pointing in the direction of Earth and had no effect on our planet.

Everything seems to indicate that Cycle 25 is going to be

.

If at the maximum of Cycle 24 the Sun was populated with 115 spots, some predictions indicate that in Cycle 25 it could reach a maximum of around 130. However, according to other predictions, the Sun could have two hundred spots at its maximum of 2025.

predictions

The differences between some predictions and others are due to the difficulties that solar physicists encounter in extrapolating what the behavior of the Sun will be. These extrapolations are made from the patterns observed in solar activity during the last centuries, but there are several techniques for carry them out.

Some prediction methods are simply based on the recent behavior of sunspots, while others are based on models that

Sun.

The latter seem to be the most reliable, but they need to know the value of the magnetic field in the polar areas of the Sun, a value that is very difficult to measure today.

The European Solar Orbiter space probe (in which Spain plays an important role) should provide images of the solar poles in the year 2025, during the maximum, which could greatly contribute to refining activity prediction models.

Solar storms and their risks

Violent flares are produced in sunspots that are accompanied by the emission of X-rays. These rays, which take about 8 minutes to reach our planet, help to ionize the upper layers of the atmosphere and are usually absorbed in the ionosphere.

But when the radiation is intense enough, it can heat and distort the ionosphere and

our communications systems, especially the short waves used in long-range aviation, emergency communications and amateur radio systems.

Along with X-radiation, solar flares can be associated with coronal mass ejections that carry large amounts of highly energetic particles traveling at speeds of between 300 and 1,000 kilometers per second.

When ejected in the direction of our planet, these particles, which take two or three days to reach Earth,

technological equipment.

In order to carry out planning work in electrical and aerospace companies, continuous monitoring of the Sun and the development of reliable forecasting methods is therefore of vital importance.

Auroras

But not everything is negative in solar storms.

When the particles ejected by the Sun reach our planet, they penetrate our atmosphere following the magnetic lines of the magnetosphere, that is, through regions near the poles.

By interacting with the atoms and molecules of the atmosphere, in the region

where the density is sufficient, the solar wind particles communicate energy that leads to high energy levels in the atmospheric particles.

The rapid de-excitation of the latter then produces the beautiful luminous radiation that we call polar auroras.

Rafael Bachiller

is director of the National Astronomical Observatory (National Geographic Institute) and academic of the Royal Academy of Doctors of Spain.

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