Is it related to the recent hot weather?, The record for the highest temperature in 20 years in the Earth's thermosphere | Earth | Weather

July 4th, 5th, and 6th were the three hottest days on record on Earth, especially July 6th, when the global average temperature 2 meters above the Earth's surface reached 17.23 ℃, making it the hottest day on Earth since instrument records began in the 1850s. You should know that the last time the Earth was so hot was during the Imbrian Ice Age, about 120000 years ago.

In fact, in 2023, in addition to the Earth's temperature already exploding, the Earth's thermosphere outside the surface also experienced the highest temperature in 20 years. According to NASA data, after absorbing the energy of solar storms, the Earth's thermosphere also reaches its peak temperature in nearly 20 years.

NASA predicts that a large-scale solar storm will soon hit Earth again, with auroras visible in 13 states including Maryland in the United States.

The thermal layer is very hot but the total energy is not high

Is it related to temperature that the Earth's thermosphere has reached its highest temperature in 20 years? The answer is no problem.

"To answer this question, the first step is to understand what the thermosphere is," Ren Zhipeng, a researcher at the Institute of Geology and Physics, Chinese Academy of Sciences, told West China Urban Daily and Cover News on July 10th.

According to various properties such as vertical motion and energy absorption, the atmosphere is divided into multiple levels. From the ground up, there are troposphere, stratosphere, mesosphere, and thermosphere. Generally speaking, the thermosphere refers to the atmosphere at an altitude of 85 kilometers above the ground, and most human aircraft capable of reaching this altitude are rockets and artificial satellites.

"The main source of energy in the thermosphere is the absorption of ultraviolet radiation with very short wavelengths from the sun, mainly concentrated in far ultraviolet radiation and extreme ultraviolet radiation. The temperature near the ground is generally around 300 Kelvin, which is about 27 degrees Celsius; the temperature in the thermosphere is generally as low as 600 Kelvin, and can reach 1500 Kelvin when it is high, and even exceed 2000 Kelvin, which is much higher than the ground." Ren Zhipeng introduced that the energy in the thermosphere comes and dissipates quickly. "Its storage effect is generally not so strong, and can only last for a few days. The temperature in the thermosphere changes due to the intensity of solar radiation."

Although the temperature of the thermosphere far exceeds the surface temperature, it has little effect on the temperature. Ren Zhipeng introduced, "As the altitude increases, the density of the atmosphere decreases exponentially. The reason why satellites can fly in the sky for a long time is also related to the low density of the thermosphere. Therefore, although the thermosphere temperature is high, the total energy is limited. Moreover, it acts as a protective layer, absorbing many high-energy particles and rays that are harmful to us humans, so it has little to do with ground temperature."

Solar activity may further enhance

Why has the thermosphere temperature reached its peak in 20 years this year?

Researcher Ren Zhipeng stated that when it comes to the atmospheric thermosphere, it is generally related to the solar activity cycle. The solar activity index has a cycle of approximately 11 years, and NASA's mention of this 20 year cycle is actually due to the previous solar activity cycle with a significant solar activity peak, which basically ended around 2003; In the following solar activity cycle, the overall solar activity is weak, and when it should be strong, it does not become stronger, resulting in a weak overall ultraviolet radiation from the sun. In the last solar activity week, there were even two years with the lowest solar radiation since the beginning of the space age -2008 and 2009.

"The calculation for this 20 year period mainly consists of the late stage of the previous solar activity cycle, the entire cycle of the previous solar activity cycle, and the starting stage of the current solar activity cycle. Due to the weak activity of the previous solar activity cycle, it appears to be strong this year. In fact, the current solar activity is similar in intensity to 2003 and has not yet reached its peak. There is still a possibility of further enhancement of solar activity in the future."

Increased impact on space activities

Although the temperature rise in the thermosphere has limited impact on normal human activities, it has a significant impact on space activities. Researcher Ren Zhipeng repeatedly reminded when discussing this issue, "Due to the weak solar activity in the previous cycle, the impact on space exploration was also relatively small. However, entering a new cycle, solar activity has returned to normal levels, so more careful verification is needed for space exploration."

"Many satellites have relatively low flight altitudes, so atmospheric drag becomes an important factor determining the lifespan of satellites." Ren Zhipeng said, "As the temperature of the thermosphere rises, the corresponding density will increase dramatically, leading to a doubling of the lifespan of these satellites."

At the beginning of 2022, Musk's star chain crashed dozens of satellites in one go due to the impact of geomagnetic storms, which resulted in this loss. At that time, the star chain was likely based on the data of weak solar activity in the previous cycle, and a more economical solution was designed. Unexpectedly, the ordinary disturbance in the thermosphere caused dozens of satellites to crash.

"In fact, this is also a warning." Ren Zhipeng said, "Now that solar activity has basically returned to normal, China's space activities have also been increasing in recent years. We must be doubly careful in this regard."