MOSCOW, January 4, Vladislav Strekopytov. According to Indian astronomers, the peak of the current cycle of solar activity will occur between January and September 2024. According to scientists, there is a possibility that plasma emissions will reach the Earth, which means large-scale failures in satellites and ground-based electrical devices are possible.
Solar cycles
Solar cycles are periodic changes in solar activity. The most famous and best studied are the 11-year Schwabe cycles. They are characterized by a rather rapid (on average four years) increase in the number of sunspots and a slower (about seven years) decrease. That's why they are also called sunspot cycles. At the end of each, the polarity of the Sun's magnetic field is reversed.
Observations dating back to 1755 show that the strongest disturbances in the space environment, or space weather, occur around the middle of the cycle. But predicting the exact time of the onset of maximum activity is quite difficult even with the help of modern methods.
In December 2019, the next, 25th cycle of solar activity began. Models predicted it would peak in late 2025 or early 2026. However, judging by the latest data, this may happen a year earlier.
Magnetic effect
In 1935, Swiss astronomer Max Waldmeier discovered that the faster the growth rate of sunspots, the higher the peak, so stronger cycles take less time to reach maximum intensity. This correlation is traditionally used to predict the timing of the peak based on observations of the early phase of the next solar cycle.
Astrophysicists from the Center of Excellence in Space Science at the Indian Institute of Science Education and Research (IISER) in Kolkata have found another pattern that helps predict when solar activity will peak. They established a connection between the rate of decay of the magnetic field dipole moment and the increase in the number of sunspots. The discovery of Indian scientists does not in any way contradict the Waldmeier effect, but rather provides an opportunity to better understand the physical reasons for its occurrence.
Two sides of the same process
The Sun is a giant sphere of plasma – hot ionized, electrically charged gas. Convective plasma flows create the magnetic field of the star, and areas of its disturbance appear as sunspots. They are comparable in size to the Earth, and the intensity of magnetism in them is tens of thousands of times stronger than on our planet.
The solar dipole moment is the difference in magnetic field strength near the north and south poles. It changes over time, decreasing as it approaches the peak of solar activity. This is due to the fact that the magnetic field lines shift following the moving plasma.
At the beginning of the solar cycle, the magnetic field lines are poloidal – directed along the meridians. By the middle of the cycle they become toroidal – located along parallels. And at the end of the cycle, a change in polarity occurs. Such periodic changes are explained by the uneven rotation of the plasma (the equatorial regions of the Sun rotate faster than the polar regions) and the action of Coriolis forces.
The authors analyzed archives of long-term observations of ground-based solar observatories and proved that changes in the number of sunspots and the dipole moment are not interrelated events, but different manifestations of the same mechanism of an electromagnetic dynamo driven by the energy of plasma flows inside the Sun. This means that they can be used as two independent parameters, which significantly increases the reliability of the modeling.
By combining both parameters in their model, scientists calculated that the maximum of the 25th solar cycle will most likely occur in the period from January to September 2024 .
Flashes more dangerous than the maximum
For each solar cycle, the time of maximum activity and its strength are usually predicted.
“Predicting the time is the most difficult thing,” says Tatiana Podladchikova, a space weather specialist, Associate Professor at Skoltech, Candidate of Technical Sciences. “If you look at the graphs, the activity of the Sun is quite high now. There is a possibility that we are already at the maximum. But the peak could be double – one, for example, this year, and the other in two. And the total duration of the maximum will be about three to four years. All forecasts are very inaccurate. The version of Indian scientists is just one of the versions.”
Concerning the strength of the upcoming maximum, the spread of forecasts is also very large.
“Some scientists suggest that it will be approximately the same in strength as the peak of the previous, 24th solar cycle,” explains the expert. “This is also indicated by the results of our research. But there are those who believe that it will be much stronger “.
In any case, it is not the period of increased activity as such that should be feared, but individual extreme solar events, which occur more often during the decline of the solar cycle, notes Podladchikova.
Powerful flares are accompanied by magnetic storms and coronal mass ejections . High-energy radiation and plasma arms can reach near-Earth space and the Earth's surface. And this is much more dangerous for instruments and satellites.
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