Shulou(Shulou.com)11/24 Report--

In the early morning of April 24, gorgeous red light bands appeared in the sky of Karamay, Xinjiang, as if someone was sprinkling in the darkness with a huge paintbrush. This dazzling scene was recorded by the photographer for everyone to enjoy, and people familiar with it can see at a glance that this is the aurora.

How do auroras come into being? To put it simply, charged particles in the solar wind are captured by the earth's magnetic field, accelerate along the magnetic line of force, and eventually hit atmospheric molecules, causing them to excite and emit light of different wavelengths. The solar wind is a hot plasma stream constantly erupting on the surface of the sun, which carries the sun's magnetic field and spreads in all directions. When the solar wind encounters the earth's magnetic field, it will produce complex interactions, forming a huge magnetosphere structure. In this structure, there is a part called magnetotail, which is a tail formed by the earth's magnetic field elongated by the solar wind. In the magnetotail, particles from the solar wind and the ionosphere accumulate and are released in the magnetic reconnection, accelerating the production of energy particles and settling along the magnetic line of force. These particles collide with atmospheric molecules near the earth's poles, producing different colors of light. For example, oxygen atoms emit green or red light, and nitrogen atoms emit blue or purple light.

This explains why the aurora is obviously blown by the solar wind, but it is stronger at night. Small particles are also good at sneaking attacks! Of course, these charged particles not only bring auroras, they also interact with the Earth's magnetic field, leading to drastic changes in the magnetic field, a phenomenon called geomagnetic storms. Generally speaking, during geomagnetic storms, auroras are usually more active and obvious.

Obviously, as a natural luminescence phenomenon that occurs at high latitudes, if auroras appear in the middle latitudes, it proves that solar activity is abnormal. The aurora in Xinjiang is closely related to a geomagnetic storm. According to the National Space Weather Monitoring and early warning Center, a major geomagnetic storm with an kp index of 8 occurred from 2: 00 a.m. to 8: 00 a.m. on April 24.

In fact, due to the relatively low latitude in China and the magnetic pole on the North American side, it is difficult for even geomagnetic storms with a kp of 8 to cause auroras in China. Coincidentally, the coronal mass ejection that triggered the geomagnetic storm was directed directly at the earth. This is really prepared.

Although the aurora is beautiful, it sings very well: "the most charming and dangerous". Aurora burst is caused by high-energy charged particles, a large number of high-energy examples entering the earth will cause the failure of man-made satellite communications, ground communications and power transportation will be affected. Among them, geomagnetic storms have the most serious impact on space satellites. As a result of this geomagnetic storm, the newly launched Fengyun 3G was forced to make some adjustments; in February 2022, Star chain also lost 40 satellites due to a geomagnetic storm. For most ground facilities, the impact of a general geomagnetic storm is not serious, but if you encounter a particularly severe geomagnetic storm, it can still have some impact on daily life. For example, in March 1989, Quebec, Canada was interrupted by a geomagnetic storm for as long as nine hours.

Therefore, it is also a good thing that the aurora does not visit China very often, and it is not a good thing for the whole earth when most parts of China can see the aurora. For example, in 1859, Hebei had the record of aurora: "Red gas starts in the northwest", and the so-called red gas is the same color as this Xinjiang aurora. This time, the influence of the aurora extends not only to Hebei, China, but also to the kingdom of Hawaii at 20 degrees north latitude. The pointer of the geomagnetic instrument at the Greenwich Observatory even jumped out of the scale, which is called a burst meter today. This process is called the Carrington incident. At that time, there were not many electronic devices, and today, the impact of geomagnetic storms on the earth on this scale would be catastrophic. In July 2012, the sun again ejected coronal mass equivalent to the Carrington event, but fortunately there was some deviation from the earth's position, otherwise the Mayan prophecy would have come true in a sense.

The Northern Lights, a painting by the painter Frederick Edwin Church depicting the Carrington incident, although the active sun will have so much impact on the earth, we cannot expect solar activity to weaken. In fact, as long as solar activity weakens slightly, it may have a greater impact on human life than when solar activity is active. For example, the famous "Mund minimum", during this period, although there are still auroras, but sunspots are almost invisible. Correspondingly, during this period, the winter weather around the world was unusually cold. Further studies show that the temperature anomaly in the minimum period of solar activity ranges from-0.5 ℃ to-0.4 ℃. As a result, whenever solar activity weakens slightly, there are fears that the earth will enter a small ice age.

However, whether the minimum period is really related to the abnormal temperature of the earth is still a controversial topic. However, the effects of solar periodic activities on the earth's energy budget, climate change, monsoon and weather have achieved fruitful results. We still hope that the sun will keep its normal activity and quietly illuminate the earth.

The relationship between Meiyu Belt and sunspots (SSN). References:

Ding Yihui. The influence of solar activity on the earth's climate and weather [J]. Meteorology, 2019. 45 (03): 297-304.

This article comes from the official account of Wechat: stone popular Science Studio (ID:Dr__Stone), author: Xing Si

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