Aurora in Beijing? Navigation failure? Are these "abnormal phenomena" caused by it?

The Aurora was photographed in Beijing!

On the evening of December 1, astronomy enthusiasts in Huairou District and Mentougou District of Beijing captured the aurora phenomenon, and #北京极光# topped the Weibo hot search list, sparking a lot of discussion among netizens. It is worth mentioning that this is the first time that the aurora phenomenon has been recorded on a large scale in Beijing since the advent of photography technology.

Weibo Hot Search

Before this, many people believed that the aurora could only be seen near the Antarctic Circle or the Arctic Circle. But in recent days, auroras have appeared in many parts of my country, including northern Heilongjiang, Hulunbuir, Inner Mongolia, and many other places.

The aurora was photographed in Beijing on December 1 (Photo by Pu Shi)

Behind the Aurora

How are the auroras formed?

For a long time, people have had different opinions on the causes of the aurora. It was not until the 1960s that scientists combined ground observations with those detected by satellites and rockets and gradually formed a scientific explanation for the aurora.

In fact, the formation of auroras requires several elements, namely the atmosphere, magnetic field and solar storms. After the solar storm enters the Earth's magnetic field, under the influence of the Earth's magnetic field, high-energy particles turn to the polar regions and collide with atoms in the upper atmosphere in the high altitudes near the North and South Poles of the Earth, producing luminescence and thus producing auroras.

It is worth mentioning that the aurora can be observed not only on Earth, but also on other planets such as Jupiter and Mercury.

Mars Aurora

Since the beginning of this year, auroras have been seen frequently in northern my country because solar activity is gradually increasing. Eruptions or explosive activities on the surface of the sun generally have a rough cycle of about 11 years. December 2019 is the starting point of this solar activity cycle, and we are now in the rising phase of solar activity. Current monitoring shows that compared with the rising phase of the previous solar cycle, the solar explosive activity in this rising phase is significantly stronger.

Since 2023, there have been relatively large geomagnetic activities in relevant areas of my country for many months. The aurora seen this time is also inseparable from the geomagnetic storm caused by relatively strong solar activity.

Geomagnetic storm phenomenon

Geomagnetic storms are a typical solar eruption activity. We know that the corona is the outermost layer of the sun's atmosphere. When the sun erupts, a coronal mass ejection will occur. One ejection can throw hundreds of millions of tons of solar matter away from the sun's surface at a speed of hundreds of kilometers per second. At the same time, they also carry the sun's strong magnetic field energy. Once it hits the earth, it will cause changes in the direction and size of the geomagnetic field. This is called a geomagnetic storm.

Geomagnetic storms have many effects, one of which is to drive the movement of particles in the Earth's upper atmosphere to intensify, eventually causing the atmosphere to expand due to heat and spread to higher space. The aurora is actually just a "by-product" of geomagnetic storms.

So what impact do geomagnetic storms have on us?

Cai Zheng, associate professor of the Department of Astronomy at Tsinghua University, said that geomagnetic storms not only bring beautiful and mysterious auroras, but may also affect the propagation of radio waves, thereby interfering with ground communications and satellite signals, affecting the accuracy of navigation satellite systems and the signal quality of mobile phones and satellite TV; they may also affect power transmission systems, leading to data loss or functional failure of satellites in orbit. Radiation increases during magnetic storms, and astronauts working in space usually have to take additional protective measures, but it has almost no effect on the health of ordinary people.

The appearance of the Aurora in Beijing

So why has the aurora, which is originally common in high-latitude areas, expanded to Beijing, which is around 40 degrees north latitude?

In fact, although auroras mainly appear in high latitudes, they can also appear in mid- and low-latitudes, but at a lower frequency. The specific situation is affected by geographical location, climate conditions and changes in solar activity.

Sometimes auroras even appear in low latitudes near the equator, a phenomenon known as an "auroral storm". Although this is rare, some countries and regions near the equator have indeed recorded this phenomenon. This usually occurs when solar activity is particularly strong, and the energy of the solar wind can cross the magnetic field boundary near the equator, extending the visibility of auroras to low latitudes.

Most of the auroras observed in our country are red. Why is that?

Schematic diagram of human observation of the aurora

In the schematic diagram of human observation of the aurora, we can also see that most of the auroras are concentrated 90 to 400 kilometers above the earth. Above 300 kilometers, the aurora is mainly light red, 200 to 300 kilometers are mainly dark red, 100 to 200 kilometers are mainly green, and below 100 kilometers are blue, purple, or a mixture of multiple colors.

Because the earth's surface has a certain curvature, the earth itself will block some distant objects. If the observation point is too far away from the aurora, only the red aurora at a higher altitude can be seen. Therefore, the aurora seen in China are mostly red, while those seen in the Arctic Circle are mostly green.

It is worth mentioning that in the next few months to one or two years, solar activity will still be at its peak, so we may once again see the gorgeous aurora visiting the earth.