This article was originally published on conversation. This publication is a feature of Space.com Expert Voices: Commentary and Insights.
Alan Cooper Professor at Charles Sturt University
Pavle Arsenovic He is a senior scientist at the University of Natural Resources and Life Sciences (BOKU).
The amazing aurora that occurred in early May this year demonstrated the power of solar storms in the form of radiation, but sometimes Sun These explosions, known as “solar particle events,” proton Emitted directly from the surface of the sun like a searchlight space.
Records show that approximately every 1000 years Earth It could experience extreme solar particle events that could severely damage the ozone layer and increase ultraviolet (UV) radiation levels at the Earth’s surface.
We analyzed what would happen if such an extreme event were to occur. Paper published todayAlso, the Earth magnetic field If the magnitude of the earthquakes is small, these events can have dramatic effects on life on Earth.
Earth’s important magnetic shield
Earth’s magnetic field deflects electrically charged radiation from the Sun, providing an important protective cocoon for life. Under normal conditions, the field acts like a giant bar magnet, with field lines rising from one pole, looping around, and falling back down the other pole, a pattern sometimes called an “upside-down grapefruit.” The vertical orientation of the poles allows some ionized cosmic radiation to penetrate into the upper atmosphere, where it interacts with gas molecules to produce the glow known as the aurora borealis.
Related: We may have witnessed the most powerful aurora in 500 years
But the field changes a lot over time. timeOver the past century, the North Magnetic Pole has moved across northern Canada at a rate of about 40 kilometers per year, More than 6%The geological record shows that there have been centuries, even millennia, of periods when the Earth’s magnetic field was very weak or nonexistent.
The following diagram shows what would happen without the Earth’s magnetic field. MarsLost its global magnetic field a long time ago, and as a result, lost most of its atmosphere. Powerful solar particle event hits Mars.it is, Mars Odyssey The radiation dose in the spacecraft was about 30 times that of a chest X-ray on the surface of Mars.
The Power of Protons
The Sun’s outer atmosphere is constantly changing Electronic And Yoko said,Solar windHowever, the Sun’s surface sporadically emits bursts of energy (mostly protons) in solar particle events, which often Solar flare.
Because protons are much heavier and carry more energy than electrons, they reach lower altitudes in Earth’s atmosphere and excite gas molecules in the air, but these excited molecules only emit X-rays, which are invisible to the naked eye.
Hundreds of weak solar particle events occur every year Solar Cycle (roughly 11 years), but scientists have found evidence of much more powerful events throughout Earth’s history, some of the most extreme being thousands of times more powerful than anything recorded by modern instruments.
Extreme solar particle events
These extreme solar particle events Approximately every few thousand yearsThe most recent occurred around AD 993, when Viking buildings in Canada Timber harvested in 1021.
A decrease in the ozone layer leads to an increase in radiation levels
In addition to their direct effects, solar particle events can also set off a chain of chemical reactions in the upper atmosphere that destroys the ozone layer. Ozone absorbs the sun’s harmful UV rays, but can also damage vision and DNA (increasing the risk of skin cancer) and affect the climate.
Among Us New ResearchWe used a large-scale computer model of Earth’s atmospheric chemistry to investigate the effects of extreme solar particle events.
They found that such events could reduce the ozone layer for around a year, increase ground-level UV radiation, and increase DNA damage. But if the solar proton event occurs at a time when the Earth’s magnetic field is very weak, the ozone layer damage could last for six years, UV radiation levels could increase by 25%, and rates of sun-induced DNA damage could increase by up to 50%.
Particle blast from the past
How likely is this deadly combination of a weak magnetic field and an extreme solar proton event? Given how frequently each occurs, the chances of them happening at the same time seem relatively high.
In fact, this chain of events could explain some mysterious events in Earth’s past.
The most recent period of magnetic field weakening, which included a temporary pole-swap, began 42,000 years ago and lasted for about 1,000 years. Several major evolutionary events occurred: It happened around this timeThe disappearance of the last Neanderthals in Europe Extinction of large marsupials include Australia’s Giant Wombat and Kangaroo.
Even bigger evolutionary events have been linked to the Earth’s geomagnetic field. The origin of multicellular animals at the end of the Ediacaran period (565 million years ago) Fossils in the Flinders Ranges of South AustraliaIt occurred over a period of 26 million years Weak or non-existent magnetic field.
Similarly, the rapid evolution of many different groups of animals during the Cambrian explosion (about 539 million years ago) has also been linked to geomagnetic fields and high levels of ultraviolet light. The simultaneous evolution of eyes and hard shells in several unrelated groups is Explained “Escape from the Light” as the best way to detect and avoid harmful UV rays.
Explorations into the role of solar activity and the Earth’s magnetic field in the history of life are only just beginning.
