The Aurora Borealis, or the Northern Lights, illuminates the sky above Nehe City in northeast China's Heilongjiang Province, March 25, 2024.(Photo: Xinhua)

China's National Center for Space Weather on Sunday issued a solar flare warning as a strong solar flare (X1.3-class) erupted from the sun. Other strong solar flares may erupt in the next three days, the center said.  

The X1.6 class solar flare erupted at 2:01 pm Sunday Beijing time and had an impact on the ionosphere over China. It is expected that in the next three days, there is still a possibility of M-class or X-class solar flares, said the center in its warning. 

Solar flares are large explosions from the surface of the Sun that emit intense bursts of electromagnetic radiation, which can last mere minutes. They are rated based on their strength, with A-class as the smallest, followed by B, C, M and X as the most potent, according to the Xinhua News Agency. They are one of the most intense sun phenomena, with a cycle of approximately 11 years. Their main observational characteristics are that a localized region of the solar atmosphere suddenly becomes brighter, often accompanied by enhancements in various energy bands of electromagnetic radiation and particle emissions, with a rapid increase in brightness and a slower decrease.

Although the lifespan of a solar flare is only a few minutes to dozens of minutes, the energy released is equivalent to the total energy of tens of thousands or even millions of strong volcanic eruptions, or equivalent to the explosion of billions of hydrogen bombs.

The 25th solar cycle peak of solar activity between January and October is predicted to be a period of "solar maximum," meaning the sun will reach its peak activity level for the current cycle in 2024.

Earlier on Friday, the National Center for Space Weather also issued a solar flare yellow warning, as the sun erupted with a strong solar flare (X1.6-class) at 10:22 am Friday Beijing time. This event occurred during daytime and had an impact on the ionosphere over China, the center said.

Solar flares, as the most typical solar eruption activity, can eject billions of tons of solar material from the surface of the sun at speeds of several hundred kilometers per second. They carry the sun's powerful magnetic energy, and when they hit the Earth, they can cause changes in the direction and strength of the Earth's magnetic field, known as geomagnetic storms, said Cheng Xin, vice dean of the School of Astronomy and Space Science at Nanjing University, as quoted by The Paper. 

Cheng noted that geomagnetic storms can cause fluctuations in voltage and current in long-distance power transmission systems, leading to power outages or unstable power supply, changes in satellite attitude, and disruptions in GPS signals, resulting in navigation failure. 

In the face of the impact of geomagnetic storms, Cheng said that accurate prediction of solar activity is crucial as it can give people some warning time, and operators can take measures to protect infrastructure from the severe effects of solar storms, such as strategically shutting down power grids, readjusting aircraft routes or satellite orbits. 

He also noted that not all effects of geomagnetic storms are negative, as they can also lead to phenomena such as auroras. "If the geomagnetic storm is particularly strong, auroras may even be visible in more southern regions," Cheng said. 

A few months earlier in December 2023, due to geomagnetic storms, auroras appeared in many high-latitude areas of China, including Northeast China's Heilongjiang and North China's Inner Mongolia. During those days, to observers' surprise, auroras were even observed in Beijing, a lower latitude area. According to the China National Geographic Channel, it was the second recorded aurora sighting in Beijing history.