Fierce 'superflares' from the sun zapped aninfant Earth3 March 2015, by Adam Hadhazy, Astrobiology Magazine

The young Sun inundated the early Earth withsuperflares of particles and radiation. Credit:NASA/Vladimir Airapetian

Our young sun may have routinely blasted Earthwith gobs of energy more powerful than any similarbombardments recorded in human history.

Huge bursts of these particle and radiation"showers" ignited by these so-called "superflares"could have penetrated Earth's protective magneticfields and bathed our planet's atmosphere, a newstudy has shown. Superflares, therefore, likely hadprofound impacts on the development of life on ourplanet.

The findings stem from a growing set ofobservations of other stars like the Sun. NASA'sKepler spacecraft spotted the brighteningcharacteristic of flares in Sun-like stars it monitoredfor over four years. Although flares commonlyerupt from the Sun and it appears other stars aswell, frequency does not render these stellar

explosions any less impressive.

"Solar flares represent the most violent eruptions inthe Solar System," said Vladimir Airapetian, seniorastrophysicist at NASA's Goddard Space FlightCenter and a research professor at George Masonand Capella Universities. "They release energycomparable to a couple billion megatons of TNT ina few minutes."

Airapetian was the lead author of a new paper onthe findings appearing in the Proceedings of 18thCambridge Workshop on Cool Stars, StellarSystems, and the Sun Proceedings of LowellObservatory.

The Kepler data, along with observations of twoSun-like stars by Japanese astronomers, haverevealed that the Sun's documented spasms mightbe rather mild and rare in modern times, fortunatelyfor us.

The 'Big One'

The biggest flare event in recent history was the so-called Carrington event in 1859, named after theBritish astronomer Richard Carrington. Hedocumented a brightening of the Sun near a groupof sunspotsoften the site of flaresthat precededan incredible aurorae display. Astonished skygazers reported the colorful Northern Lights as farsouth as the Caribbean.

Aurorae are caused by particles of air gettingcharged up by energy from the flaring Sun as itfloods into the atmosphere at Earth's poles. In theCarrington event, this overflow of energy alsoinduced electric currents in telegraph wires,causing sparks, and even setting equipment on fire,according to reports from the time.

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Based on the Carrington event and smaller, morerecent Sun-spawned disruptions, many scientistsand policymakers worry about a devastatinglypowerful flare crippling our technology-dependent,modern society.

Airapetian's study affirmed these concerns asjustified. Observations of 279 Sun-like starsdetected signs of brightening comparative in size tothe Carrington event, but also superflares on theorder of 10,000 times stronger than any flaresknown to have been unleashed by the Sun.

"This discovery is hard to overestimate," saidAirapetian, "because it may uncover the 'hiddenpowers' of our Sun in the past, near or far future."

In the Carrington event of 1859, aurora, like that seenhere, descended as far south as the Caribbean. Credit:NOAA

Unruly youth

Other research has found that young, Sun-likestars, much like young human children, areparticularly prone to throwing tantrums. Early intheir lives, stars rotate faster and are moremagnetically activeconditions ripe for flareeruptions.

Flares arise when magnetic field lines emanatingfrom the Sun, which normally form "rubber band-like" loops, snap and reconnect, experiencing a sortof "short circuit," as Airapetian calls it. A burst oflethal doses of solar radiation as well as the Sun's

constituent charged gas, or plasma, often spews outinto space. When the latter is involved, the flare issaid to have hurled a coronal mass ejection, orCME.

Very active stars yield stronger and more frequentflares and CMEs. Airapetian said that according tohis research team's calculations, the young Sun inits first several hundred million years of life couldhave cranked out an astounding 250 superflaresper day.

Of course, then as now, most superflares andassociated CMEs would have missed Earth, arelatively small target in the Solar System. Still,statistically speaking, it looks likely that early Earthtook the brunt of a solar blast more powerful thanthe Carrington event at the shocking rate of at leastonce a dayand for half an eon.

An energetic rain

To get a sense of the effects on early Earth fromthis sort of, as Airapetian put it, "fast and furious"superflare and super-CME bombardment, he andhis team built computer models. The modelssimulated a relatively conservative super-CME,only about twice that of the Carrington event'spotency, and had it smash into a model of theEarth's magnetosphere and upper atmosphere.

For simplicity's sake, Airapetian assumed that Earthhad developed a magnetic field of similar intensityas today's about 500 million years after its birth,shortly following the Sun's genesis 4.6 billion yearsago. The presence of this field would probably haveoverlapped for a time with the Sun's youthfulsuperflare activity. Life, perhaps not incidentally, isthought to have emerged about 3.8 billion yearsago, after the magnetic field's formation.

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Earths magnetic field, illustrated here, could havegreatly compressed under an onslaught of superflaresfrom the young Sun. Credit: NASA

According to the new study, early Earth's magneticfield would have buckled under the raging Sun'sonslaught.

"In our paper, we have shown that a superCarrington-type CME event would have greatlycompressed the magnetic field," said Airapetian."This would ignite huge electric currents on Earthand let energetic particles penetrate the Earth'satmosphere and surface."

Giver, or taker, of life?

What exactly this radiation would have done tohinder or perhaps, counterintuitively, help life's rise,is debatable. The timing of a modicum of protectionagainst the superflaring young Sun, thanks to amagnetic field, suggests the complexity of life's self-replicating chemistry could not have withstood theyoung Sun's energetic interference.

However, continuing research by Airapetiansuggests superflares and CMEs from the Sun mighthave been integral to life's rise. Such energeticradiation could have broken apart nitrogenmolecules with very tightly bound atoms in the earlyEarth's atmosphere into free, individual nitrogenatoms. From the perspective of chemistry, nitrogenatoms bond well with other atoms.

Superflares might have paradoxically paved the way forlife on Earth. Credit: Peter Sawyer / SmithsonianInstitution

Thus set free by superflares, the nitrogen atomscould have then combined with hydrogen andcarbon, creating "organic molecules that can setfavorable conditions for creating the building blocksof life," said Airapetian. Furthermore, the nitrogenatoms could have combined with hydrogen formingammonia in the atmosphere, a greenhouse gas thatmight have played an important role in warming theearly Earth.

It's been a long-standing mystery how inert,molecular nitrogen in early Earth's atmosphere everbroke down into atomic nitrogen. Life performs thistask all the time, but it begs the chicken-or-the-eggscenario of how life ever formed without availablenitrogen, and how nitrogen was ever availablewithout life. Superflares might provide the answer.

"On one hand, our studies suggest that the harshconditions introduced by intensive radiation fromflare and CME activity had a detrimental effect onlife," he said. "On the other hand, high levels ofsteady, intense radiation could have opened a'window of opportunity' for the origin of life on Earthby setting a stage for prebiotic chemistry itrequires."

Airapetian and colleagues have continued digginginto these implications and promise new resultssoon.

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Source: Astrobio.net

This story is republished courtesy of NASA'sAstrobiology Magazine. Explore the Earth andbeyond at www.astrobio.net .

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