Astronomy

Directionality of solar flares

Directionality of solar flares

I have read a number of articles about Coronal Mass Ejections (CME) and solar flares and I'm trying to establish how directional the radiation from them is.

I am aware that radiation from these solar events does not travel directly outward from the direction of the sun but follows magnetic lines of force and may be subject to eddies and other other effects that modify the direction of travel.

So my question is: What does the graph of average radiation intensity v radial distribution look like for a point in deep space (radiation intensity v degrees bearing from the line of maximum intensity) for a passing solar flare or CME? For the purpose of this question, deep Space is the region between the orbits of Venus and Mars

Edit

For the purposes of this question "radiation" refers to particulate radiation such as electrons, heavy nuclei and especially protons originating from the Sun during a solar flare or CME (peak flux in Watts per square metre).

In case that an exact answer is not available an approximate answer would be acceptable.


Solar flare

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Solar flare, sudden intense brightening in the solar corona, usually in the vicinity of a magnetic inversion near a sunspot group. The flare develops in a few minutes, or even seconds, and may last several hours. High-energy particles, electron streams, hard X-rays, and radio bursts are often emitted, and a shock wave occurs when the flare interacts with the interplanetary medium. The flare occurs above the surface in the corona, and energy deposited in the surface brings up a superhot cloud, about 100 million Kelvins (100 million °C, or 180 million °F), which is a strong, long-lasting source of X-rays. Smaller flares do not show all these attributes, and flares rarely occur in the three or four years of sunspot minimum. The biggest flares occur in association with large sunspots that have sharp magnetic gradients and large currents, which are the source of the flare energy. There is a class of spotless flares associated with filament eruptions they are large and sometimes produce coronal mass ejections but produce few high-energy particles.

Flares are brighter than the whole Sun in X-rays and in ultraviolet light. X-ray photons and high-energy particles arrive immediately, but the main particle flux arrives a few days later.


Solar flare hit Earth today, astronomers have revealed

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Solar storm: NASA captures the moment a sunspot 'explodes'

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Solar storms have the potential to pose a serious threat to Earth. A stream of particles released from the Sun can interfere with Earth's satellite technology. Experts are all too aware of the risk they pose, which is why they keep a close eye on them.

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Just today, astronomers have noted that a coronal mass ejection (CME) has glanced Earth's atmosphere.

CMEs come to fruition from the presence of 'sunspots' on the surface of our host star.

They are typically cooler than the rest of the surface of the Sun as sunspots are areas of strong magnetic fields.

The magnetism is so strong that it actually keeps some of the heat from escaping.

Solar flare hit Earth today, astronomers have revealed (Image: GETTY)

Solar storms have the potential to pose a serious threat to Earth (Image: GETTY)

However, as the magnetic field builds, it increases pressure in the sunspot which can erupt as a solar flare, or a CME.

A CME which was released on May 28 has finally arrived at Earth after a four-day voyage from the Sun, hitting today at around 2pm BST.

However, the solar storm was not powerful enough to cause any damage to Earth or its technology.

Astronomy site Space Weather said: "A CME hit Earth's magnetic field today, June 2nd, at approximately 1300 UT.

A CME which was released on May 28 has finally arrived at Earth (Image: GETTY)

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"It was a glancing blow, delivered by a storm cloud that left the sun on May 28th.

"The weak impact barely altered the solar wind speed around Earth (data) and has not sparked a geomagnetic storm."

The biggest solar storm known to us was the Carrington Event which occurred in September 1859.

During that solar storm, the sun unleashed a series of powerful solar flares into space that were so powerful telegraph operators&rsquo offices experienced a surge in electricity which resulted in some buildings setting on fire.

Sun facts and figures (Image: EXPRESS)

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Now, in a world far more reliant on technology, the consequences of a huge solar storm would be much more devastating, and the threat has so far been ignored, Avi Loeb, professor of science at Harvard University, has previously said.

Prof Loeb and his colleague Doctor Manasavi Lingam believe a huge solar storm similar to the Carrington Event could cost up to £16trillion ($20trillion).

Prof Loeb said: &ldquoThe sun is usually thought of as a friend and the source of life, but it could also be the opposite.

&ldquoWe predict that within 150 years, there will be an event that causes damage comparable to the current $20 trillion, and the damage will increase exponentially at later times until technological development will saturate. Such a forecast was never attempted before.&rdquo


Solar Flares

The magnetic field lines near sunspots often tangle, cross, and reorganize. This can cause a sudden explosion of energy called a solar flare. Solar flares release a lot of radiation into space. If a solar flare is very intense, the radiation it releases can interfere with our radio communications here on Earth.

NASA's Solar Dynamics Observatory captured this imagery of a solar flare, as seen in the bright flash. A loop of solar material, a coronal mass ejection (CME), can also be seen rising up off the right limb of the Sun. Image credit: NASA/SDO/Goddard

Solar flares are sometimes accompanied by a coronal mass ejection (CME for short). CMEs are huge bubbles of radiation and particles from the Sun. They explode into space at very high speed when the Sun’s magnetic field lines suddenly reorganize.


The give and take of mega-flares from stars

Credit: CC0 Public Domain

The long relationships between stars and the planets around them—including the Sun and the Earth—may be even more complex than previously thought. This is one conclusion of a new study involving thousands of stars using NASA's Chandra X-ray Observatory.

By conducting the largest survey ever of star-forming regions in X-rays, a team of researchers has helped outline the link between very powerful flares, or outbursts, from youthful stars, and the impact they could have on planets in orbit.

"Our work tells us how the Sun may have behaved and affected the young Earth billions of years ago," said Kostantin Getman of Pennsylvania State University in University Park, Pennsylvania, who led the study. "In some ways, this is our ultimate origin story: How the Earth and Solar System came to be."

The scientists examined Chandra's X-ray data of more than 24,000 stars in 40 different regions where stars are forming. They captured over a thousand stars that gave off flares that are vastly more energetic than the most powerful flare ever observed by modern astronomers on the Sun, the "Solar Carrington Event" in 1859. "Super" flares are at least one hundred thousand times more energetic than the Carrington Event and "mega" flares up to 10 million times more energetic.

These powerful flares observed by Chandra in this work occur in all of the star-forming regions and among young stars of all different masses, including those similar to the Sun. They are also seen at all different stages in the evolution of young stars, ranging from early stages when the star is heavily embedded in dust and gas and surrounded by a large planet-forming disk, to later stages when planets would have formed and the disks are gone. The stars in the study have ages estimated to be less than 5 million years, compared to the Sun's age of 4.5 billion years.

The Lagoon Nebula, one of the star-forming regions in the latest study, is about 4,400 light years from Earth in the Milky Way galaxy where stars. This field-of-view shows the southern portion of a large bubble of hydrogen gas, plus a cluster of young stars. X-rays from Chandra (purple) have been combined with infrared data (blue, gold, and white) have been combined with infrared data from the Spitzer Space Telescope in this composite image. Credit: X-ray: NASA/CXC/Penn State/K. Getman, et al Infrared: NASA/JPL/Spitzer

The team found several super-flares occur per week for each young star, averaged over the whole sample, and about two mega-flares every year.

"We want to know what kinds of impact—good and bad—these flares have on the early lives of planets," said co-author Eric Feigelson, also of Penn State. "Flares this powerful can have major implications."

Over the past two decades, scientists have argued that these giant flares can help "give" planets to still-forming stars by driving gas away from disks of material that surround them. This can trigger the formation of pebbles and other small rocky material that is a crucial step for planets to form.

On the other hand, these flares may "take away" from planets that have already formed by blasting any atmospheres with powerful radiation, possibly resulting in their complete evaporation and destruction in less than 5 million years.

RCW 120 is another star-forming region that was part of the new research. It is slightly farther away than the Lagoon Nebula at a distance of about 5,500 light years. This view of RCW 120, which has the same wavelengths and colors as the Lagoon composite, contains an expanding bubble of hydrogen gas, about 13 light years across. This structure may be sweeping up material into a dense shell and triggering the formation of stars. Credit: X-ray: NASA/CXC/Penn State/K. Getman, et al Infrared: NASA/JPL/Spitzer

The researchers also performed detailed modeling of 55 bright super- and mega-flares and found that most of them resemble long-lasting flares seen on the Sun that produce "coronal mass ejections," powerful ejections of charged particles that can damage planetary atmospheres. The Solar Carrington Event involved such an ejection.

This work is also important for understanding the flares themselves. The team found that the properties of the flares, such as their brightness and frequency, are the same for young stars with and without planet-forming disks. This implies that the flares are likely similar to those seen on the Sun, with loops of magnetic field having both footprints on the surface of the star, rather than one anchored to the disk and one to the star.

"We've found that these giant flares are like ones on the Sun but are just greatly magnified in energy and frequency, and the size of their magnetic loops," said co-author Gordon Garmire from the Huntingdon Institute for X-ray Astronomy in Huntingdon, Pennsylvania." Understanding these stellar outbursts may help us understand the most powerful flares and coronal mass ejections from the Sun."


Planets around old red dwarfs may still get blowtorched by flares

Well, this news is a bit of a bummer: Planets that orbit even really old red dwarfs can still get viciously zapped by high-energy radiation from flares, making it difficult for them to support life. It's not so much the flares kill everything they touch, it's that over the lifetime of the planet they strip the atmosphere away.

As you can imagine, that makes breathing difficult.

More Bad Astronomy

The new study only looked at a single star, but it's a telling one: Barnard's star, a red dwarf just 6 light years away. It's actually the fourth closest known star to the Sun (bearing in mind the Alpha Centauri system is a triple star, so that one group is 1 through 3). That's why it was picked for the study, because its proximity makes it easier to study.

Red dwarfs have less mass than the Sun, are cooler, and fainter. Specifically, Barnard's Star has only 1/6th the Sun's mass, 1/5th its diameter, and shines at an incredibly feeble 1/300th the Sun's brightness. If the Earth orbited Barnard's star at the same distance it does from the Sun, it would freeze solid.

Also, Barnard's star is old, about 10 billion years old. That's twice as old as the Sun. That plays a big role here.

Artwork of a red dwarf in a binary system undergoing a flare. Credit: NASA's Goddard Space Flight Center/S. Wiessinger

Despite their diminutive size, red dwarfs can be explosively violent. They can emit powerful stellar flares, which are enormous explosions of energy from their surfaces. Flares occur when the magnetic field lines created inside a star tangle up near the surface. These lines store huge amounts of energy, and if the lines snap — essentially short circuiting — that energy gets released all at once.

The magnetic fields of stars are created due to two things: rising and falling parcels of plasma (ionized gas) inside them, and their rotation. The rotation of the star acts as a dynamo, generating the magnetic field. The plasma deep in the star is hot, so it rises, and when it hits the surface it cools and falls again (this is called buoyant convection). The magnetic field inside these parcels of plasma is what can cause flares when they reach the surface.

Although red dwarfs can be very dim, they are fully convective, meaning plasma starts rising from the core itself all the way to the surface. That gives them a lot of time to generate powerful magnetic fields.

A huge solar flare erupted on the Sun in October 2003, seen here in X-rays. It was also accompanied by a powerful coronal mass ejection. Solar storms like these are a danger to our power grid and orbiting satellites. Credit: NASA/SOHO

When stars are young they tend to spin rapidly. They slow with age, mostly as they blow a wind of particles from their surface (like the Sun's solar wind). As the star spins, its magnetic field spins with it, catching the subatomic particles like a fishing net cast into water. This causes drag, slowing the star's spin. Over millions and even billions of years, a star's spin can slow quite a bit. Since the spin helps generate the energy to power the magnetic field, older stars tend to have weaker magnetism… which in turn means they don't flare as much.

Very young red dwarfs are terrifying they erupt with gigantic flares all the time, making them terrible places to look for planets with life. First of all, these flares are ridiculously powerful, sometimes equaling the total amount of energy the star puts out otherwise. Also, they emit tons of hard high-energy radiation like ultraviolet and X-rays.

But as they age they settle down, right? And given that Barnard's Star is so ancient, it must be pretty calm. Right? Right?

Yeah, in this case not so much. The new study used Hubble and Chandra to examine the nearby dim bulb to see how often it flares and how powerful they are. Although they didn't observe it for long (about 14 hours total) Barnard's Star performed for them pretty well: It erupted three times, twice in the far-ultraviolet and once in X-rays. Looking at the overall duration times of the flares, the astronomers found that Barnard's Star is in a flare state about 25% of the time.

That's a lot. Like, a lot a lot. The flares weren't super powerful — about one ten-thousandth as bright as the total energy of the Sun — but still a big deal. Why?

Artwork depicting a flare from a red dwarf stripping away a planet’s atmosphere. Credit: NASA/CXC/M. Weiss

We know that red dwarfs are good at making planets like Earth (roughly the same size and made of the same sort of material). To be habitable around such a feeble star, though, these potential Earths have to orbit close in. That means when the star flares, the planet takes the full brunt of it.

The atmosphere absorbs that energy, but doing so heats it up, making it puffier, and more likely to leak away from the planet. The astronomers calculate that a planet like Earth orbiting Barnard's Star would lose its atmosphere in roughly 10 million years.

Artwork depicting a system of planets around a red dwarf star. Credit: ESO/M. Kornmesser/N. Risinger (skysurvey.org)

Mind you, any planet like Earth that close to its red dwarf host would probably lose its air rapidly after it formed, because, remember, the stars flare a whole lot more when they're young. The hope was that after the star settles down, geological processes might create a second atmosphere around the planet, making it potentially habitable.

This new study shows that's unlikely. Like I said earlier: Bummer.

Well, maybe. Again, this is one star, chosen because it was close, so the flares could be detected more easily. It's possible Barnard's Star is unusually flarey for an old red dwarf.

After all, not all red dwarfs are this active. In fact, in another paper just published astronomers found a couple of warm planets orbiting two different red dwarfs, and both stars appear inactive as far as flares go. The planets are larger than Earth and receive quite a bit more heat from their stars that we do (one gets more than Venus, the other more than Mercury!), but still, this gives me hope that there are yet many Earth-sized planets orbiting calmer red dwarfs out there.

This won't help Barnard's Star's planet, though. Not long ago a planet was found orbiting Barnard's Star, a super-Earth, though far enough out (60 million kilometers) that it's almost certainly incredibly cold, roughly -170°C! In that case, getting hit by billions of flares might be doing it a service.

I'll note as I always do that we're still getting started understanding all this, and there's a long way to go. Maybe there are billions of Earth-sized planets in the galaxy stripped bare by their tantrum-throwing host stars, or maybe there are mitigating factors we don't know yet.

That latter may be the way to bet, so I'm not quite ready to throw out a whole galaxy over one star. Let's keep looking.


Contents

Flare stars are intrinsically faint, but have been found to distances of 1,000 light years from Earth. [3] On April 23, 2014, NASA's Swift satellite detected the strongest, hottest, and longest-lasting sequence of stellar flares ever seen from a nearby red dwarf, DG Canum Venaticorum. The initial blast from this record-setting series of explosions was as much as 10,000 times more powerful than the largest solar flare ever recorded. [4]

Proxima Centauri Edit

The Sun's nearest stellar neighbor Proxima Centauri is a flare star that undergoes occasional increases in brightness because of magnetic activity. [5] The star's magnetic field is created by convection throughout the stellar body, and the resulting flare activity generates a total X-ray emission similar to that produced by the Sun. [6]

Wolf 359 Edit

The flare star Wolf 359 is another near neighbor (2.39 ± 0.01 parsecs). This star, also known as Gliese 406 and CN Leo, is a red dwarf of spectral class M6.5 that emits X-rays. [7] It is a UV Ceti flare star, [8] and has a relatively high flare rate.

The mean magnetic field has a strength of about 2.2 kG ( 0.2 T ), but this varies significantly on time scales as short as six hours. [9] By comparison, the magnetic field of the Sun averages 1 G ( 100 μT ), although it can rise as high as 3 kG ( 0.3 T ) in active sunspot regions. [10]

Barnard's Star Edit

Barnard's Star is the fourth nearest star system to Earth. Given its age, at 7–12 billion years of age, Barnard's Star is considerably older than the Sun. It was long assumed to be quiescent in terms of stellar activity. However, in 1998, astronomers observed an intense stellar flare, showing that Barnard's Star is a flare star. [11] [12]

TVLM513-46546 Edit

TVLM 513-46546 is a very low mass M9 flare star, at the boundary between red dwarfs and brown dwarfs. Data from Arecibo Observatory at radio wavelengths determined that the star flares every 7054 s with a precision of one one-hundredth of a second. [13]

2MASS JJ18352154-3123385 A Edit

The more massive member of the binary star 2MASS J1835, an M6.5 star, has strong X-ray activity indicative of a flare star, although it has never been directly observed to flare.

The most powerful stellar flare detected, as of December 2005, may have come from the active binary II Peg. [14] Its observation by Swift suggested the presence of hard X-rays in the well-established Neupert effect as seen in solar flares.


Earth has an area of magnetic force activity, called a magnetic field. It is also surrounded by a jacket of gases, called an atmosphere. Our magnetic field and atmosphere act like a superhero’s shield, protecting us from the majority of the solar wind blast.

Most of the charged particles crash into Earth’s shield and flow around it. The particles squish and flatten the side of the magnetic field that faces the Sun. The other side of the magnetic field stretches into a long, trailing tail.

In this image, the blue lines represent the shield created by Earth’s magnetic field. Notice how the solar wind shapes the magnetic field. Credit: SOHO (ESA & NASA)

Sometimes charged particles sneak past Earth’s shield. When these particles hit the atmosphere, we are treated to glowing light shows known as auroras.

Auroras, seen here over Alaska. Credit: NASA/Terry Zaperach


The effects of solar flares on Earth's magnetosphere

An illustration of solar flare impacts on the whole geospace. Credit: Jing Liu.

Planet Earth is surrounded by a system of magnetic fields known as the magnetosphere. This vast, comet-shaped system deflects charged particles coming from the sun, shielding our planet from harmful particle radiation and preventing solar wind (i.e., a stream of charged particles released from the sun's upper atmosphere) from eroding the atmosphere.

While past studies have gathered substantial evidence of the effects that solar wind can have on Earth's magnetosphere, the impact of solar flares (i.e., sudden eruptions of electromagnetic radiation on the sun) is poorly understood. Solar flares are highly explosive events that can last from a few minutes to hours and can be detected using X-rays or optical devices.

Researchers at Shandong University in China and the National Center for Atmospheric Research in the U.S. have recently carried out a study investigating the effects that solar flares can have on Earth's magnetosphere. Their paper, published in Nature Physics, offers new valuable insight that could pave the way towards a better understanding of geospace dynamics. Geospace, the portion of outer space that is closest to Earth, includes the upper atmosphere, ionosphere (i.e., the ionized part of the atmosphere) and magnetosphere.

"The magnetosphere is located in the region above the ionosphere and is the fully ionized space region above 1000 km from the ground," Professor Jing Liu, one of the researchers who carried out the study, told Phys.org. "The region is surrounded by the solar wind and is affected and controlled by the earth's magnetic field and the solar wind's magnetic field."

The magnetosphere is generally described as Earth's protective barrier against solar wind and other solar particles, as it prevents these particles from entering the planet's other protective layers. Nonetheless, past studies showed that when the direction of solar wind is opposite to the magnetosphere's magnetic field, magnetic lines from these two regions can 'connect." This means that some solar wind particles can be directly transmitted to the space surrounding Earth.

"We asked ourselves: Can the flare process, which is characterized by enhanced radiation, not only directly affect the earth's ionosphere, but also cause disturbance in the magnetosphere like the solar wind?" Liu said. "To answer this question, we adopted a series of observational datasets, collected by global satellite navigation systems, the European incoherent scattering radar network, ionospheric satellites, lunar orbiting satellites, and more."

Liu and his colleagues analyzed data collected by different devices and satellites during a solar flare event that took place on 6 September 2017. To do this, they adopted a recently developed numerical geospace model developed at the National Center for Atmospheric Research. This model, called the high spatial-temporal resolution magnetosphere ionosphere thermosphere model (LTR), reproduces the changes triggered by solar flares in the magnetosphere-ionosphere coupling system.

Using the LTR model and previously collected data, the researchers were able to unveil solar flare effects on magnetospheric dynamics and on the electrodynamic coupling between the magnetosphere and the ionosphere. More specifically, they observed a rapid and large increase in flare-induced photoionization of the polar ionospheric E-region at altitudes between 90 and 150 km. The phenomenon observed by Liu and his colleagues appeared to have a number of effects on the geospace region, including a lower Joule heating of the Earth's upper atmosphere, a reconfiguration of the magnetosphere convection and changes in auroral precipitation.

"We demonstrated that solar flare effects extend throughout the geospace via electrodynamic coupling, and are not limited, as previously believed, to the atmospheric region where radiation energy is absorbed," Liu explained. "Due to the similar solar-magnetosphere-ionosphere coupling process in other earth-like planets, our study also provides new clues for exploring and understanding the effects of solar flares on other planets. In my future research, I plan to study the effects of flares on planets with the same magnetosphere (such as Jupiter, Venus and Saturn)."


The elephant and the stars

At stake, besides the health of our planetary infrastructure, is the pride that astronomers take in feeling that they understand the complicated and violent processes going on behind the sun’s relatively calm face.

“I think the problem with the sun is that we’re too close to it, and so there’s too much data about the sun,” Dr. McIntosh said. He called it a breaker of models: “Your models are going to fail eventually. It’s part of the reason why it’s so hard 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 website Spaceweather.com, agreed in an email. “In my experience, when people really understand something, they can explain it simply,” he said. “It is striking to me that almost no one in the solar-cycle prediction business can explain their favorite dynamo model in a way that lay people can ‘get it.’”

The situation reminded him of the proverbial blind men who try to produce a Theory of Elephants, with one of them focused solely on feeling the animal’s trunk.

“Scott and Bob are standing off to the side shouting, ‘Hey, you guys are ignoring most of the elephant,’” he said. “In other words, there’s more to the solar cycle than is commonly assumed by conventional models. And so, according to Scott, they are doomed to get the big picture wrong.”

Jay Pasachoff, an astronomer at Williams College who has spent his life observing the corona during solar eclipses, said he did not put much store in such forecasts. In an email, he recounted a meeting during the last cycle that had “an amusing set of talks.”

The conversation, as he recalled it, went: “The next cycle will be stronger than average, the next cycle will be weaker than average, the next cycle will be either stronger than average or weaker than average, the next cycle will be neither stronger than average nor weaker than average.”

He added, “So my plan is to wait and see.”

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

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

Indeed, astrophysicists suspect that such a fate befell Mars, which was once warmer and wetter than it is now.

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

“Recent work has shown that ultraviolet light might be very important for catalyzing life — turning complex molecules into amino acids and ultimately into single-celled organisms,” she said. “Since M dwarfs are so small and cold, they don’t actually produce that much UV radiation, except when they flare. Perhaps there is a sweet spot where a star flares enough to spark life but not so much that it immediately destroys it!”