This article was originally published on Conversation. The publication contributed an article to Space.com’s Expert Voices: Op-Ed & Insights.
Alan Cooper is a professor at Charles Sturt University
Pavel Arsenovič is a senior researcher at the University of Natural Resources and Life Science (BOKU).
A remarkable aurora in early May this year demonstrated the power that solar storms can emit as radiation, but at times sun it does something far more destructive. These bursts, known as “solar particle events”. protons directly from the surface of the sun it can shoot like a searchlight space.
Records show that roughly every thousand years Earth is hit by an extreme solar particle event that could cause severe damage to the ozone layer and increase surface ultraviolet (UV) radiation levels.
We have analyzed what happens during such an extreme event and paper released today. We also show it in times when the earth is magnetic field is weak, these events could have a dramatic effect on life across the planet.
Earth’s critical magnetic shield
Earth’s magnetic field provides a vital protective cocoon that deflects electrically charged radiation from the Sun. In its normal state, it acts like a gigantic bar magnet, with lines of force rising from one pole, looping and falling back down at the other pole, in a pattern sometimes described as an “inverted grapefruit”. The vertical orientation at the poles allows some ionizing cosmic rays to penetrate down into the upper atmosphere, where they interact with gas molecules to produce the glow we know as the aurora.
Related: We may have just witnessed some of the strongest auroras in the last 500 years
However, the field is changing a lot time. In the last century, the north magnetic pole traveled across northern Canada at a speed of about 40 kilometers per year, and the field weakened by more than 6%. The geological record shows that there were periods of centuries or millennia when the geomagnetic field was very weak or even completely absent.
By looking, we can see what would happen without the Earth’s magnetic field Mars, which lost its global magnetic field and consequently most of its atmosphere in the distant past. In May, not long after the Northern Lights, a powerful solar particle hit Mars. It disrupted traffic Mars Odyssey spacecraft and caused radiation levels on the surface of Mars about 30 times higher than what you would get during a chest X-ray.
Proton force
The Sun’s outer atmosphere emits a constant fluctuating current electrons and protons known as “solar stormHowever, the solar surface also sporadically emits bursts of energy, mostly protons, in solar particle events—which are often associated with solar flare.
Protons are much heavier than electrons and carry more energy, so they reach lower altitudes in Earth’s atmosphere and excite gas molecules in the air. However, these excited molecules only emit X-rays, which are invisible to the naked eye.
Hundreds of faint solar particle events occur each solar cycle (roughly 11 years), but scientists have found traces of much stronger events throughout Earth’s history. Some of the most extreme were thousands of times stronger than anything recorded by modern instruments.
Extreme solar particle events
These extreme solar particle events happen roughly every few millennia. The most recent occurred around 993 AD and was used to show which Viking buildings in Canada used wood harvested in 1021 AD.
Less ozone, more radiation
In addition to their immediate effect, solar particle events can also set off a chain of chemical reactions in the upper atmosphere that can damage ozone. Ozone absorbs the sun’s harmful UV rays, which can damage eyesight and DNA (increasing the risk of skin cancer), as well as affect the climate.
In ours new studywe used large-scale computer models of global atmospheric chemistry to investigate the impacts of an extreme solar particle event.
We found that such an event could deplete ozone levels for a year or so, increase surface UV radiation levels, and increase DNA damage. However, if the solar proton event came during a period when Earth’s magnetic field was very weak, ozone damage would last for six years, increasing UV radiation levels by 25% and increasing the rate of DNA damage caused by the sun by up to 50%.
Particle explosions from the past
How likely is this deadly combination of a weak magnetic field and extreme solar protons? Given how often each occurs, it seems likely that they occur together relatively often.
In fact, this combination of events can explain several mysterious events in Earth’s past.
The last period of weak magnetic field – including a temporary switch between the north and south poles – began 42,000 years ago and lasted about 1,000 years. Several significant evolutionary events occurred around this timesuch as the disappearance of the last Neanderthals in Europe and extinction of marsupial megafauna counting on it giant wombats and kangaroos in Australia.
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An even larger evolutionary event has also been linked to the Earth’s geomagnetic field. The origin of multicellular animals at the end of the Ediacaran period (from 565 million years ago), recorded vr fossils in the Flinders Ranges of South Australiaoccurred after a period of 26 million years weak or absent magnetic field.
Similarly, the rapid evolution of various groups of animals in the Cambrian explosion (about 539 million years ago) is also related to geomagnetism and high levels of UV radiation. There was simultaneous development of eyes and hard body shells in many unrelated groups described as the best means of detecting and avoiding harmful incoming UV rays while ‘running away from the light’.
We are still only beginning to explore the role of solar activity and Earth’s magnetic field in the history of life.