Close-up space images reveal unusual activity of the Sun, where bright explosions, called flares, cause massive waves of radiation.
Darker, cooler areas called sunspots appear, move, change shape and disappear. The Sun also shoots material into space in powerful explosions called solar particle events.
This solar activity varies over time, peaking every 11 years, and it was expected that the next high peak would occur in July 2025.
However, it now looks as if this “solar maximum” will arrive sooner than expected. This finding could lead to a better understanding of our star.
Solar activity also affects the Earth and the technology we depend on. Solar particle events can disable satellites and disrupt electrical grids. Solar activity that affects our planet is often referred to as "space weather."
To ensure we can predict and prepare, we need a good set of rules – a scientific model. NASA and the US National Oceanic and Atmospheric Administration have been creating these elements for many years. It combines a variety of methods to predict solar activity. This approach has resulted in the next solar maximum (peak) being scheduled for approximately July 2025. This peak is also expected to be relatively weak, like the maximum during the previous solar cycle, which lasted from approximately December 2008 to December 2019, peaking in April 2014.
However, alternative forecasts have been published by a team led by NASA scientist Robert Lemon, and Scott McIntosh, deputy director of the US National Center for Atmospheric Research (NCAR).
The team says the peak of the cycle will occur a year earlier in mid-late 2024, and sunspot numbers will be twice the official prediction, an indicator of activity. Current observations of the Sun also support these alternative predictions.
What is interesting is that many forecasting methods rely on the timing of the cycle length measured by the minimum (lowest point) of solar activity. But Lemon and McIntosh looked more deeply into actual sunspots and their magnetic properties.
The current prediction uses the lag — the time at which the last sunspot of the ancient cycle has faded — to indicate the end of the solar cycle. This can lead to different cycle length timings.
But what does rising solar activity mean for us, as the cycle soon reaches its peak?
Since the Sun releases huge amounts of energy in the form of flares and other events that fling material into space, there is a possibility that some of it could hit Earth if we were in the line of fire. Fortunately, the Earth has its own magnetic shield that can protect us.
When particles and magnetic fields coming from the Sun reach us, they first interact with the Earth's magnetic field, causing them to be crushed and preventing them from colliding with the Earth's surface.
Although the Earth's magnetic "shield" gives us a degree of protection, solar activity still affects us.
Solar activity can cause a power surge in long transmission lines used in electrical grids. An example is the 1989 power outage in Quebec, Canada.
Other effects include a change in the density of particles in the upper atmosphere. This can cause minor errors on devices that use GPS.
When solar activity becomes stronger, we are more likely to be hit by a solar storm, causing electrical problems on satellites. These spacecraft may need to be put into what is called “safe mode” where many systems are turned off.
Our society is constantly evolving in ways that make us more dependent on electrical infrastructure. We are also working to extend our technology to space. Electrical grids are being designed to be less vulnerable to power surges, and satellites are being designed to better handle space weather.
But we need a deeper understanding of our star. Experts already keep a detailed record of previous observations and are constantly expanding methods for observing the Sun and space weather using satellites.
The report was prepared by Daniel Brown, lecturer in astronomy, from Nottingham Trent University.
The mystery of the "destructive volcanic" tsunami was solved 373 years after it occurred
The eruption of the underwater Colombo volcano in the Aegean Sea in 1650 triggered a devastating tsunami recorded by eyewitnesses on that date.
A group of researchers, led by Dr. Jens Carstens, a marine geophysicist at the GEOMAR Helmholtz Center for Ocean Research in Kiel, surveyed the underwater Colombo Crater using modern imaging technology and reconstructed the historical events.
They found that eyewitness accounts of the natural disaster could only be described by a combination of a landslide followed by a volcanic eruption.
From the Greek island of Santorini, the eruption was visible for several weeks. In the late summer of 1650, people reported that the color of the water had changed and that the water was boiling.
About seven kilometers northeast of Santorini, an underwater volcano rose from the sea and began spewing glowing rocks.
Fires and lightning were seen, and columns of smoke darkened the sky. Then the water suddenly receded, rising toward the coast moments later, hitting it with waves up to 20 meters high. A massive explosion was heard more than 100 kilometers away, pumice stone and ash fell on the surrounding islands, and a deadly cloud of toxic gases claimed the lives of several people.
“We know these details about the historic Colombo eruption because there are contemporary reports compiled and published by a French volcanologist in the 19th century,” says Dr. Carstens.
But to find out how these devastating events occurred, Carstens and his German and Greek colleagues went to the Greek Aegean Sea in 2019 to study the volcanic crater with special technology.
On board the now-decommissioned research vessel POSEIDON, the team used 3D seismic methods to create a 3D image of the crater, which now lies 18 meters below the surface of the water.
“This allows us to look inside the volcano,” notes Dr. Gareth Crutchley, co-author of the study.
Not only did 3D imaging show that the crater was 2.5 kilometers in diameter and 500 meters deep, indicating a truly massive explosion, but seismic profiles also revealed that one side of the cone had been severely deformed.
“This part of the volcano has definitely slid,” Crutchley says.
The researchers then compared the various mechanisms that could have caused the tsunami with historical eyewitness accounts. They concluded that only a combination of a landslide followed by a volcanic eruption could explain the tsunami.
By combining 3D earthquakes with computer simulations, the researchers were able to reconstruct how high the waves would have been if they had been caused by the explosion alone.
“Accordingly, waves of six meters high were expected in a certain place, but we know from eyewitness reports that their height was 20 metres,” Carstens explains.
Moreover, the sea is said to have receded first at some point, but in the computer simulation, the wave crest reaches the coast first. Therefore, the explosion alone cannot explain the tsunami event.
However, when the landslide was included in the simulations, the data agreed with historical observations.
Carstens explains, “Colombo is partly made up of pumice with very steep slopes. It is not stable. During the eruption, which lasted for several weeks, lava was constantly ejected. Below, in the magma chamber, which contains a lot of gas, there was "Immense pressure. When one side of the volcano slid, the effect was like opening a bottle of champagne: the sudden release of pressure allowed the gas in the magma system to expand, creating a huge explosion."
The results were published in the journal Nature Communications.