Aurora Flash: Hello, the Sun Express has arrived!

On the evening of December 1, auroras appeared in the night sky over Mohe, Inner Mongolia and even Beijing. Astronomy enthusiasts took photos of the aurora based on the forecast released on November 30 by the National Space Weather Monitoring and Early Warning Center of the China Meteorological Administration, and the photos went viral on the Internet. The Beijing Aurora quickly became a hot topic.

Beijing Aurora Photo Source: Pu Shi

Most people would be unfamiliar with the term "space weather". The space here is not simply outer space. Space weather actually occurs on the surface of the sun, in the interplanetary space, and in the Earth's space environment (magnetosphere, ionosphere, thermosphere, and middle and upper atmosphere). It can affect the normal operation and reliability of space-based and ground-based technical systems, and endanger the conditions or state of human activities, health, and life. [1] The most important space weather is solar activity.

The aurora is the third "express delivery" that the Earth receives from the Sun. When a solar storm erupts, it will send three "express deliveries" to the Earth. The first "express delivery" is the electromagnetic waves emitted by the flare, which travels through space at a speed of about 3x108m/s, just like sunlight reaching the Earth, and arrives at the Earth in just eight and a half minutes. The X-rays and ultraviolet rays in it will affect the Earth's ionosphere, disrupting communication systems and positioning services. The second "express delivery" is carried by high-energy protons, which arrive at the Earth after tens of minutes to more than ten hours. It causes absorption in the D region of the ionosphere, hindering aviation communications and satellite operations.

The third "express delivery" is the coronal mass ejected into the universe by clouds of solar matter, some of which will reach the Earth in about two or three days. A large amount of coronal mass travels through the universe at high speed, delivering express delivery. After reaching the Earth, it "frictions" with the Earth's magnetic field, forming geomagnetic storms, and is "packaged" in the atmosphere, producing auroras.

The coronagraph carried by the SOHO satellite captured the process of the coronal mass ejection. Image source: China Weather Network

The National Space Weather Monitoring and Warning Center observed four bursts of coronal mass ejections at 5:00, 21:00, 22:00 on November 27 and around 20:00 on November 28. The three coronal eruptions on the 27th were weak but concentrated in time. The last burst was the strongest and formed a nearly spherical ejection surface. The charged plasma of the coronal ejection usually "attacks" the earth two or three days later. Therefore, the National Space Weather Monitoring and Warning Center predicts that a small geomagnetic storm will occur on November 30, and a large geomagnetic storm will occur on December 1, which may last until the next day.

At the same time, a forecast was released that parts of Heilongjiang and Xinjiang in my country might see red or even green auroras. But the auroras that appeared in parts of Beijing were obviously beyond the forecast.

The aurora in Beijing is due to the fact that we are at the end of the 25th solar activity cycle, and the intensity of solar activity is about to reach its peak . The more intense the solar activity, the more powerful the material thrown out, which can break through many obstacles and reach areas with lower latitudes. Therefore, the aurora that can only be seen in high-latitude areas will also appear in Beijing, which can also explain why auroras have appeared frequently in China this year, where auroras are rare.

Original studies have shown that solar activity will reach its peak in 2025, but based on current observation data, solar activity will reach its peak ahead of schedule in 2024, which will be the best year for observing the aurora.

The aurora appears more frequently in the United States and my country at similar latitudes. This is because the two ends of the Earth's magnetic field are not completely aligned with the Earth's rotation axis. Relative to the rotation axis, the magnetic field in the northern hemisphere deflects toward the western hemisphere. Therefore, in the northern hemisphere, China and the United States are at similar latitudes, and the probability of seeing aurora in the United States is higher.

Image credit: Space Weather

Behind the gorgeous aurora lies a multitude of crises . The movement of the sun seems to be far away from us, but in fact, it affects our lives all the time. In history, there have been many incidents that disrupted the normal order of human life, namely space disasters.

In March 1989, during the peak of solar activity, high-intensity coronal ejections broke out, and the Earth's powerful geomagnetic storm generated huge induced currents, which impacted power supply systems around the world. The situation was the most serious in Quebec, Canada, where the power grid was completely paralyzed and 6 million households were in darkness. Most areas restored power after 9 hours, but some areas even spent several days in darkness. At the same time, the United States and Japan also faced the phenomenon of power supply system transformers burning out, and Sweden experienced circuit tripping.

The movement of the sun can directly affect high-tech equipment in space, especially causing damage to the operation of artificial satellites. There have been many incidents of damage to artificial satellites.

In early November 1990, the Fengyun satellite B, which had only been in operation for two months, was affected by the high-energy particle flow from the solar eruption, causing the computer program controlling its attitude to become chaotic and the satellite flipped. After repairs, the satellite continued to operate normally. On February 14 of the following year, the satellite's attitude flipped again due to solar activity, but due to the failure to discover and remedy the problem in time, Fengyun satellite B was completely unable to operate.

The "Bastille Day incident" on July 14, 2000, caused image resolution degradation, data loss, and space station orbit decline for many artificial satellites. Japan's ASCA satellite even fell into the Earth's atmosphere and burned up.

At the same time, solar activity is closely related to human health. Studies have shown that the incidence of some infectious diseases, skin diseases, cardiovascular and cerebrovascular diseases are related to the intensity of solar activity. The more intense the solar activity, the higher the incidence.

In order to mitigate the damage caused by solar activity, Chinese scientists continue to work hard to study and predict space weather events. This includes using satellites and other observation equipment to monitor solar activity and space weather conditions, as well as developing prediction models and algorithms to predict space weather events, which is particularly helpful for the development of aerospace industry. The representative is the National Space Weather Monitoring and Early Warning Center.

The National Space Weather Monitoring and Warning Center ensures that aircraft in flight maintain contact with the ground; provides great convenience for aircraft navigation; reduces life threats to flight attendants and passengers; and escorts the successful launch of spacecraft and their orderly operation.

Fengyun-3E solar extreme ultraviolet band monitoring image Source: Space Weather

References:

[1] China Association for Science and Technology. Geophysics Development Report[M]. Beijing: China Science and Technology Press, 2009: 31.

Author: Li Beibei, Associate Professor of the Institute of History of Science and Technology and Meteorological Civilization