Will "solar magnetic field reversal" bring disaster? Don't be scared!

Rumor: "The sun's magnetic field is about to reverse, will it bring disaster to the earth?"

Some people on the Internet claim that the solar magnetic field is about to reverse, which will lead to increased solar activity, which will directly affect the earth and bring disasters, causing confusion and worry among people. Rumor analysis shows that this is alarmist.
The reversal of the solar magnetic field is not uncommon, and it occurs once every 11 years. It does not bring any "disaster" to the Earth, nor does it have a significant impact on our daily lives. The change in the solar magnetic field has a certain impact on satellite operations and space missions, but it is not only due to increased solar activity.

Maybe you already know this, or maybe you just found out after reading this article: In the next one or two years, the solar magnetic field will reverse (again). Many people are beginning to worry about this, and some are beginning to make alarmist statements, saying that the solar magnetic field reversal will lead to increased solar activity, bringing disaster to the earth, etc. So is this true?

Copyrighted stock images, no reproduction is authorized

Let me first state the conclusion: Another reversal of the solar magnetic field will not bring doomsday to the Earth and mankind, but the change in the solar magnetic field will indeed have some impact on satellites and space missions.

Why do I say so?

The reversal of the solar magnetic field is nothing new

The term "solar magnetic field reversal" sounds particularly grand, and since the sun is closely related to our lives, everyone may worry about their own safety. But there is no need to be afraid. It turns out that "solar magnetic field reversal" is not a rare thing even if it is put on the scale of our short 100-year life - the solar magnetic field reverses once every 11 years or so on average. The magnetic north pole moves from the northern hemisphere of the sun to the southern hemisphere, or from the southern hemisphere to the northern hemisphere. This goes back and forth, and a complete "Haier cycle" (Hale, not the one that makes home appliances) is completed every 22 years.

Friends who can understand this article should have experienced at least one solar magnetic field reversal, or even at least one 22-year Haier cycle! Now everyone is safe and sound (most of them have no memory of the magnetic field reversal they experienced...), which just shows that this kind of solar activity is not a big deal for people living on the surface of the earth, and the rumor that the solar magnetic field reversal will bring disasters is self-defeating. Of course, although the solar magnetic field reversal will not directly bring disaster to the earth and humans, it does have a certain impact, but the range is outside the earth's atmosphere.

Is low solar activity okay?

The reversal of the solar magnetic field marks the peak of solar activity. During the peak years of solar activity, sunspots frequently appear and coronal mass ejections often occur. If the ejected material happens to hit the earth, it will cause magnetic storms marked by low-latitude auroras. Magnetic storms can cause communication interference, satellite failures, atmospheric expansion due to heat, and in extreme cases, power outages. Magnetic storms can also make auroras occur more frequently.

Everyone is already familiar with news about magnetic storms. For example, in 2024, auroras frequently appeared in northern China because of frequent solar activity. In 2022, Musk's SpaceX Starlink satellite also suffered damage due to magnetic storms. However, these impacts are still limited to outside the Earth's atmosphere.

Since solar activity can "climb to the top", it means that there is still half of the road "downhill" - solar activity will also become low. Although it seems to be more "peaceful" compared to the high solar activity years, in fact, the "cold violence" of the low solar activity years is also worth being vigilant! Since we have already talked a lot about the high solar activity years and geomagnetic storms, this time we will focus on the impact of the low solar activity years.

Cosmic rays taking advantage of the void

As a planet of the sun, the earth is always "covered" by the sun. The solar wind blows out a large bubble with a radius of tens of billions of kilometers in interstellar space, called the "heliosphere". The largest structure in it is called the "heliospheric current sheet", which is composed of solar wind materials driven by the magnetic field that rotates with the sun. It plays a modulating role in the flow of cosmic rays from interstellar space.

Solar wind is deflected by the Earth's magnetic field. Copyrighted image. Reproduction is not authorized.

Cosmic rays are mainly composed of protons and alpha particles, flying at a speed close to the speed of light. They are extremely energetic and can penetrate 10-20 cm thick aluminum plates (the main material of manned spacecraft), or change the logic state of microelectronic devices, threatening the safety of spacecraft. In the International Space Station, about 80% of the radiation equivalent received by astronauts comes from cosmic rays. In years of high solar activity when the magnetic field reverses, the heliospheric current sheet will fluctuate violently, blocking the attack of cosmic rays on the solar system. In relatively calm years of low solar activity, cosmic rays are more likely to come in. Fortunately, with the protection of the Earth's atmosphere and magnetic field, it has little impact on the daily lives of ordinary people.

As can be seen from the figure below, the low solar activity years are the high cosmic ray years. my country's manned lunar landing plan is in 2030, which is a low solar activity year, so we must strengthen our precautions against cosmic rays; and cosmic ray detection equipment, such as "Lasso", can expect fruitful observation results at that time.

High-energy particles from coronal holes

The corona refers to the outermost layer of the sun's atmosphere, with a temperature of up to 1 million degrees Celsius and a thickness of millions of kilometers. In the corona, there are some darker areas with lower energy and gas density than the surrounding areas. They look like holes, so they are called "coronal holes." Charged solar particles are usually trapped in the magnetic field around the sun. If a coronal hole appears, the particles will escape from here, twice as fast as the usual solar wind. In years of high solar activity, coronal holes will be concentrated around the sun's poles and have little impact on the earth. In years of low solar activity, coronal holes will appear near the sun's equator, aiming the muzzles of the firing guns at the orbital planes of the solar system planets, and their size and number will increase.

Although not as violent as the coronal mass ejections during the most active years of the Sun, the coronal holes are large and can exist for a long time. As the Sun rotates, the high-energy particle streams escaping from the coronal holes sweep across the Earth every 27 days or so, injecting a large number of charged particles into the Earth's outer radiation belt (13,000-60,000 kilometers from the Earth), causing potential damage to satellites operating there (including many navigation, meteorological, and communication satellites).

High-inclination satellite electrostatics

Satellites operating in low-Earth orbit will also be disturbed by the low solar activity, but interestingly, the disturbance is not caused by the sun's active attack, but by the sun's passive sabotage.

When a low-orbit satellite with a large orbital inclination passes near the Earth's poles, it will encounter charged particles pouring down from the "funnel" at both ends of the geomagnetic field. The electrons will accumulate on the satellite. When the accumulation reaches a certain level, static electricity discharge will occur, endangering the safety of the satellite. Fortunately, low-orbit satellites operate in the ionosphere, where the sun's extreme ultraviolet radiation ionizes the Earth's atmosphere, generating a large number of free positive and negative charges. The positive charge can neutralize the electrons accumulated on the surface of the satellite and alleviate the satellite's charging effect.

However, in years with low solar activity, the ionization level of the ionosphere will also decrease due to the decrease in extreme ultraviolet radiation, and the supply of positive charge will be a bit out of order. The threat of charging effect to low-orbit satellites will be greatly increased. A 12-year long-term study published in 2012 found that although auroras are more frequent in years with high solar activity, the frequency of electrostatic charging is very low, and almost no events with charging above 100 volts occur. On the contrary, in years with low solar activity, the frequency of such events increases greatly, with nearly 40 events occurring in the busiest month, with the highest voltage recorded reaching 2,000 volts.

With the continuous advancement of China's space program, including the realization of ambitious goals such as lunar exploration and Mars exploration, my country will accelerate the pace of space exploration in the next few years. At the same time, as more and more spacecraft enter space, we should not take the space environment lightly. The space weather caused by solar activity is complex and changeable, and high and low years have their own troubles. We need to strengthen the daily monitoring and forecasting of the space environment to escort space missions.

Looking in the mirror of rumors

Many of these rumors are fabricated with the help of astronomical phenomena, usually with the characteristics of exaggerating facts and creating panic, using sensational language to exaggerate serious consequences and attract public attention. They often take things out of context and interpret scientific phenomena one-sidedly. For example, they ignore the periodicity and harmlessness of the reversal of the solar magnetic field and only exaggerate the possible negative impact. In addition, these rumors cater to the public's cognitive bias towards science, take advantage of people's fear of the unknown of macroscopic astronomical phenomena, create seemingly reasonable speculations, and make them more contagious. In this regard, we should not be fooled by seemingly high-sounding professional terms. As long as we do a little search, the rumors will be self-defeating.

References

[1]https://www.space.com/sun-magnetic-field-flip-solar-maximum-2024

[2]https://www.researchgate.net/figure/Modulation-of-cosmic-ray-flux-at-Earth-by-the-solar-magnetic-cycle-The-top-panel-depicts_fig4_353010829

[3]https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2011JA016875

Planning and production

Author: Qu Jiong, a popular science writer whose works have been published in the National Museum, the National Space Administration, etc.

Review | Liu Xi, researcher at Beijing Planetarium, science film director and writer