Will the next space weather season be stormy or fair?

The great news about the sun is that there is no big news. We are blessed, astronomers like to say, to live next to a “boring star.”

But the inhabitants (if any) of the planets that orbit the neighboring star Proxima Centauri, just 4.2 light-years away, are less fortunate. In April, astronomers announced that a massive flare had erupted from its surface in 2019. For seven seconds, as a battery of telescopes on Earth and in space watched, the tiny star had increased its emission of ultraviolet radiation 14,000 times, by one of the most violent flares ever seen in our galaxy.

This was more than serious territory for sunburn. “A human being on this planet would have a hard time,” said Meredith MacGregor, an astronomy professor at the University of Colorado who led the global observing effort.

Space weather on this scale could sterilize potentially habitable planets and could spell bad news for the search for life beyond this solar system. Even mild space weather can be detrimental to already evolved and settled creatures; Sunspots and solar storms, which wax and wane in an 11-year cycle, spray energy that can endanger spacecraft, astronauts, and communication systems.

A new cycle of storms will begin at any moment, and astrophysicists are divided on how active or threatening it will be. The sun may be about to set records for the number of sunspots and violent storms, or it may be sliding into a decline like the Maunder Minimum, from 1645 to 1715, when almost no sunspots appeared, a period that was known in Europe. like Little Ice. Age.

“We live in the atmosphere of a star,” as Scott McIntosh, a solar physicist at the National Center for Atmospheric Research in Boulder, Colorado, says. “As a civilization, we take our star for granted.”

Here, 93 million miles from the nearest star, which we call our sun, we exist and mostly thrive on the brink of almost incomprehensible violence and complexity.

The sun is a medium-sized star, a ball of fiery hot ionized gas a million miles in diameter. Its large interior rotates faster than its exterior, and the outer layers rotate faster at the equator than at the poles. The result is a tangled nest of magnetic fields, which manifest as sunspots and worse when they break the surface.

Every second, thermonuclear reactions at the center of the sun burn 600 million tons of hydrogen into 596 million tons of helium. The missing four million tons, converted into pure energy, constitute the mortgage payment for all life on Earth and perhaps elsewhere in the solar system. As energy emerges from the sun, it rises through successively cooler and less dense layers of gas and, finally, 100,000 years later, the photosphere, or surface, where the temperature is just 5,700 degrees Fahrenheit.

The sun is amazingly constant when making these mortgage payments. A few years ago, an experiment in Italy confirmed that our star does not appear to have changed its energy output in at least the last 100,000 years, the time it takes for that energy to migrate from the core of the sun. The researchers were able to calculate how much energy the sun produces in real time by measuring subatomic particles called neutrinos that are produced by nuclear reactions within the sun, escape in seconds, and reach Earth in just eight minutes. They found that this energy matched production that was generated 100,000 years ago and is only now detectable.

The action doesn’t stop at the surface of the sun. That friendly yellow photosphere boils like oatmeal and is peppered with dark magnetic storms – the infamous sunspots – that crackle, spin, and lash through space with showers of electrical particles and radiation. The corona, made up of thin, super-hot streamers of electrified gas, and visible only during solar eclipses, stretches millions of miles from the glowing surface.

Things sometimes go wrong, although so far on a scale well below the outbursts seen in Proxima Centauri. As the magnetic fields generated by all that swirling, electrified gas emerge on the sun’s surface, they twist and tangle. Eventually, they break and reconnect in loops, releasing enormous amounts of radiation and charged particles – an explosive solar flare that can be more powerful than millions of hydrogen bombs.

Sometimes these flares launch entire chunks of the sun’s outer layers into space, in events called coronal mass ejections. The mother of all solar storms known so far occurred on September 1, 1859, when a drop of sunlight smashed into Earth. Sparks came out of telegraph systems in Europe and North America, setting fires. The auroras that night stretched as far south as Hawaii and Cuba and were so bright that people could read their newspapers in the light.

In 2012, another coronal mass ejection barely missed Earth. An earlier study by the National Academy of Sciences concluded that a direct hit from such a storm could cause about $ 2 trillion in damage, shutting down the power grid and leaving satellites at least temporarily blind. Forget trying to use the Internet or your local ATM; many people would not even be able to flush their toilets without the electricity to run the water pumps, the report noted. “I think as a civilization we get screwed up,” Dr. McIntosh said.

Such storms are most likely to occur during high points in the mysterious 11-year cycle of sunspot activity from the sun.

Lately, the sunspot cycles have weakened. During the last cycle, 101 spots were observed in the sun in 2014, the year of maximum activity; which was well below the historical average of 160 to 240.

Last year, a committee of scientists from NASA and the National Oceanic and Atmospheric Administration predicted that the next cycle would be just as anemic, with a peak in 2025 of around 115 sunspots.

But Dr. McIntosh and his colleagues have produced a radically different forecast, of more than 200 sunspots at their peak. The 11-year sunspot cycle, they say, based on a 140-year analysis of solar measurements, contradicts a more fundamental 22-year Hale cycle, named for its discoverer, George Ellery Hale. During that period, the sun’s magnetic field reverses its polarity and then returns.

Each cycle ends or begins when two bands of magnetism, migrating from opposite high latitudes of the sun, meet at the equator and annihilate each other. On average, each phase of the cycle takes 11 years, but it can vary.

Dr. McIntosh and his team found that the longer one cycle, the weaker the next, and vice versa. The current cycle, the twenty-fourth since record-keeping began, shows all signs of ending after just over 10 years, shorter than average, which means the next cycle should be strong.

“Sunspot cycle 25 could have a magnitude that rivals the first ones since the records began,” Dr. McIntosh said in late April. On Thursday, he and his team were still waiting for the “ignition” to begin. “It’s very, very close,” he wrote in an email. “We are watching very closely.”

What is at stake, in addition to the health of our planetary infrastructure, is the pride astronomers take in feeling that they understand the complicated and violent processes that occur behind the relatively calm face of the sun.

“I think the problem with the sun is that we are too close to it, so there is too much data on the sun,” said Dr. McIntosh. He called it a model breaker: “Your models will eventually fail. It’s part of the reason it’s so difficult to forecast the weather, right? Because our observations are so detailed, but you know it’s hard to get it absolutely right. “

Tony Phillips, an astronomer who runs the Spaceweather.com website, agreed in an email. “In my experience, when people really understand something, they can explain it simply,” he said. “It amazes me that hardly anyone in the solar cycle prediction business can explain their favorite dynamo model in a way that ordinary people can ‘understand’ it.”

The situation reminded him of the proverbial blind men trying to produce an Elephant Theory, with one of them focused solely on feeling the animal’s trunk.

“Scott and Bob are standing off to the side yelling, ‘Hey, you guys are ignoring most of the elephants,'” he said. “In other words, there is more to the solar cycle than is commonly assumed in conventional models. And so, according to Scott, they are doomed to get the wrong idea. “

Jay Pasachoff, a Williams College astronomer who has spent his life observing the corona during solar eclipses, said he did not attach much thought to such forecasts. In an email, he recounted a meeting during the last cycle that had “a fun series of talks.”

The conversation, as he recalled it, was: “The next cycle will be stronger than average, the next cycle will be weaker than average, the next cycle will be stronger than average or weaker than average, the next cycle will not. it will be stronger than average than average nor weaker than average. “

He added: “My plan is to wait and see.”

Potential dangers aside, understanding how the sunspot cycle actually works is crucial “from a purely human point of view, if you want to understand the stars,” said Dr. McIntosh. “And if you think about it, the Earth’s magnetic field is largely the reason we probably have life on Earth.”

Mars, he noted, doesn’t have much of an atmosphere or magnetic field. “If your planet doesn’t have a magnetic field, you can have all the atmosphere you want,” he said, “but the friendly star in your local neighborhood could wipe it out in the blink of an eye.”

In fact, astrophysicists suspect that fate happened to Mars, which was once warmer and wetter than it is now.

Proxima Centauri, a small star known as an M dwarf, is home to at least two exoplanets, one of which is the size of Earth and close enough to the star to be habitable if it weren’t bathed in radiation. Dr. MacGregor offered a ray of hope for life in those neighborhoods.

“Recent work has shown that ultraviolet light could be very important in catalyzing life, converting complex molecules into amino acids and ultimately into single-celled organisms,” he said. “Since M dwarfs are so small and cool, they don’t actually produce as much ultraviolet radiation, except when they explode. Perhaps there is a sweet spot where a star is bright enough to ignite life, but not bright enough to destroy it immediately! “

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