Moon: Earth Big Brother, why do I hide behind you, also feel that the “solar wind” like a knife cut?
Earth: Little brother of the moon, my magnetic field seems to be swaying a little, a new study by Chinese scientists has found that even if you are behind me, my magnetic field sometimes “can’t cover” you…
On June 30, NASA’s website reported on the latest findings by chinese scientists under the title “Discovering a New Model of The Moon’s Exposure to Solar Radiation”, which was previously published in the international journal Geophysical Research and Space Physics. The American Geophysical Society (AGU) and the Rutherford Laboratory (RAL) in the United Kingdom have also paid attention to and reported on the study.
“The swaying of the Earth’s magnetic tail is a phenomenon of interaction between the solar wind and the Earth’s magnetosphere. Because this wobble affects the moon’s space environment, the study will help people understand what different space weather may be faced if the moon is to be carried out for a long time after landing. Shi Quanqi, author of the paper and a professor at Shandong University’s School of Space Science and Physics, told Science daily that the past thought that the earth’s magnetosphere deflection occurred mainly at a distance from Earth, such as three times the distance of the Earth’s moon, and this was the first time such deflection had been found in lunar orbit.
Why is this research getting NASA’s attention? “Sending astronauts to the moon for long periods of time requires understanding the dynamics of space weather around the moon,” said Professor Vassilis Angelopoulos, lead scientist for the THEMIS-ARTEMIS project at the University of California, Los Angeles. “
Meet the solar system’s “storm storm”
A full moon, as clear as a mirror.
On such days, people on earth often sing songs to the moon and sigh about the quiet years. In space, however, the solar wind is never-ending blowing into planetary space, and with the burst of solar high-energy particles, the surface of the moon without the atmosphere is far from “quiet”, but often subjected to high-energy particle radiation “bombarded”.
What are the consequences of such a “bombardment”?
“The most dangerous thing about lunar exploration equipment is the effect of high-energy particles on the materials and devices of the equipment.” Shi Quanqi said. The bombardment of high-energy particles can cause varying degrees of damage to electronic devices and satellite materials, such as increased instrument noise, incorrect sensor readings, and degradation of solar panels. Satellites orbiting the moon may also be affected by charged particles and accumulate over time, causing equipment to be “decommissioned” earlier. In addition, if we are exposed to radiation doses that exceed safety standards for a longer period of time, human cells will become cancerous and other lesions, so for astronauts working on the lunar table, excessive radiation will affect health and even life-threatening, so on the moon for human radiation monitoring and protection is also very important.
It has also been reported that when solar wind protons react with lunar soil, water formation is also produced, so understanding the effect of solar radiation on the lunar surface will also help to better understand where and how water is deposited on the lunar surface for human consumption on the moon and the source of spacecraft fuel.
But when the moon moves away from the sun (including the full moon stage), the Earth’s magnetic field has a protective effect. Studies have shown that the Earth’s magnetic field can be elongated at night (to form a magnetic tail) that deflects high-energy particles from the solar wind and gives the moon’s surface a “shield.”
That is, three-quarters of the moon’s transit cycle, protons, electrons, and sometimes high-energy particles in the solar wind go straight to the moon’s surface, as if a “storm” would hit the moon’s surface; Previous observations and simulations have shown that spacecraft operating in lunar orbit and astronauts operating on the lunar surface are relatively safe during the full moon because of the protection of the magnetosphere.
If “space weather” can be as “four distinct seasons”, then human activity on the moon will have a clear “safe period.” However, the Team’s findings suggest that this is not the case, and that there may be significant risks during what was previously thought to be a “security period”.
Intercepted space weather “change face”
Back on March 8, 2012, an interplanetary shock wave struck the moon from as far as near, and the Artemis probe was moving nearby, carrying a magnetometer that detected the plasma velocity and the size and direction of the satellite’s position in space and sent the data back to Earth.
“The data sent back by satellites is massive, different research teams set different research objectives, and when we do another study, we’re looking at the plasma and magnetic field data at this time period that’s a little bit special, very different from the magnetosphere.” Shi Quanqi said.
By screening and analyzing the broader data, the team found that there had been no previous reports of significant deflection of the tail of the Earth’s magnetosphere in observations near the moon’s orbit. The team found that in this case an interplanetary shock wave passed through the solar wind and a large turn, causing the magnetosphere to produce a large deflection in the lunar orbit: the magnetic tail swayed like a wind-blown “wind bag.”
Such a wobble makes the moon’s space weather a “big change face”: the moon at full moon is directly exposed to the Earth’s magnetosphorescism , the heating and compressed solar wind, in which the moon’s surface is exploring and astronauts and base facilities are not effectively protected, the Earth’s magnetic field will not be effectively shielded, and it is likely to be attacked by the high-energy solar particles that just come.
For example, as in a stormy storm, “the moon (including the people and objects of the moon’s watch)” even if standing under an umbrella, but the rain and the occasional hail will hit it.
Such magnetosphere deflection, which has been predicted since 1972, has been thought to occur only at distances from Earth, such as at more than three times the distance of the Earth and moon, and has never been observed as likely to reach the moon.
“At first our angle was to study the flow in the earth’s magnetic tail, but when it happens in lunar orbit, it means there is a connection to the lunar space environment.” Shi Quanqi said that the theoretical research has shown potential application value, so the team contacted the Chinese Academy of Sciences National Center for Space Science, carried out more in-depth research.
Reproduction and rediscovery of realistic simulations
Shandong University Shi Quanqi team and the National Space Science Center associate researcher Tang Binbin, in the space weather national key laboratory open project support, one side is responsible for observation, one side is responsible for simulation, in the Chinese Academy of Sciences, Peking University, Ninxin University and other units of colleagues, hope to the moon space weather “change face” reasons for more detailed exploration.
The Global Magnetic Fluid Simulation Program of the National Center for Space Science is one of the most mainstream models in the world. “Global Magnetic Fluid Mechanics (MHD) simulation is a three-dimensional modeling of the magnetosphere scale to see how the solar wind and magnetosphere interact,” Tang said. Specifically, the model uses the known upstream solar wind parameters as inputs, solves the three-dimensional magnetic fluid mechanics equation, and obtains the plasma parameters and magnetic field bit type distribution of the entire magnetosphere space and its evolution over time under the constraints of boundary conditions such as the ionosphere. “
“The global magnetic fluid mechanics model we use is a numerical model of PPM-LR magnetic fluid mechanics developed by our country, which has the characteristics of high precision and small dissipation, and can be used well to study our concerns.” Tang Binbin said.
One benefit of the simulation is the overall reproduction of magnetic field and plasma activity in the Earth-moon space, overcoming the limitations of observations by satellites with only one or two points. In layman’s terms, the simulation looks at the global situation, and the satellite can only see the parameters of the point where it is located.
On the other hand, through simulation, in addition to being able to reproduce the observed situation, it is possible to change the different input conditions to see which factors dominate among the many complex factors. Equivalent to many experiments, i.e. numerical experiments.
“Because it wasn’t clear whether it was the observed tilted shock wave or the tilted solar wind played a leading role, we made several simulations of different conditions, for example, in a simulation where we let the interplanetary shock wave hit the Earth head-on, only to have the direction of the solar wind change, and we found that the magnetosphere could have the same deflection.” Shi Quanqi said that the solar wind itself can lead to the discovery of the Earth’s magnetic field deflection, meaning that such deflection may occur more frequently than originally thought, because the probability of the solar wind meeting the deflection conditions is much higher than the probability of interplanetary shock waves.
Occasional interplanetary shocks introduced the team’s focus to the Earth’s magnetosphere deflection in lunar orbit, but continued in-depth research allowed the team to discover a bigger secret.
“We also validated the results with another model. Two different global magnetic fluid simulations show that the magnetic tail deflection at the lunar position is mainly controlled by the direction of the solar wind, with a time scale of about half an hour. “
Find out the law
Space weather forecast expected to “broadcast” for the moon landing
The phenomenon of the local ball “unmasking” the moon is no longer an accident, meaning that it will be regular and will become an important part of the moon’s space weather composition.
Studying lunar space weather will hopefully lead to early warning.
“Basic theoretical research will build models based on the observations and numerical simulations of the data, ” Shi explained. In the future, the satellite closer to the sun can monitor this deflection, once the deflection phenomenon occurs, you can immediately transmit the signal to the ground, people can immediately through model analysis, predict that it will reach the moon will make the magnetosphere deflected to what extent, if the deflection is very strong, you can as soon as possible in the tens of minutes before the early warning, notify the facilities on the moon quickly shut down sensitive instruments, astronauts immediately hide to the shelter. “
“We expect this discovery to help improve the dynamic model of the lunar radiation environment and provide a safe buffer period for all kinds of activities on the moon.” In addition, the effects of solar wind will vary with the lunar surface environment and latitude, which may affect future activities such as the location of the long-term lunar table base, mining operations, Shi said. Water synthesis also occurs when solar wind protons react with lunar soil, so this work will also help us better understand where and how water is deposited on the moon’s surface for human needs on the moon and the source of spacecraft fuel.
“The early warning of space weather is much like the weather forecast on Earth, except that the observation almost the object of space weather needs to look for the impact of solar wind, particle storms, and interplanetary electromagnetic fields on space.” Shi Quanqi said that Shandong University has now set up a lunar radiation detection laboratory, in addition to further analysis of China’s Chang’e-4 probe transmitted back the lunar space environment data, will also develop a number of autonomous detection methods, hoping to study the relevant space weather activity law more clearly.