NASA's Solar Dynamics Observatory captured this image of a solar flare – as seen in the bright flash on the right side – on Sept. 10, 2017. The image shows a combination of wavelengths of extreme ultraviolet light that highlights the extremely hot material in flares, which has then been colorized.
Credits: NASA/SDO/Goddard
You’d think that because it rises and sets predictably every day, we’d know everything there is to know about our Sun. But that’s not the case. The Sun constantly outgasses the solar wind, but also periodically belches huge blobs of plasma, energetic particles, and magnetic fields that can wreak havoc on Earth’s communications networks and other electrical systems. These blobs also slam into the other planets of our solar system, stripping their atmospheres or interacting with their magnetic fields. And we’re still not sure what mechanisms lie beneath these violent outbursts. In this week’s episode, NASA Chief Scientist Jim Green sits down with solar scientist Alex Young to discuss the Sun’s powerful explosions.
Jim Green: Our solar system is a wondrous place with a single star, our sun, and everything that orbits around it--planets, moons, asteroids, and comets. What do we know about this beautiful solar system we call home? It’s part of an even larger cosmos with billions of other solar systems.
Hi, I’m Jim Green, NASA’s Chief Scientist, and this is Gravity Assist.
With me today is Dr. Alex Young, from Goddard Space Flight Center, and Alex is a solar scientist, a physicist who's been studying the Sun, its output, and what we call space weather, his whole career. Welcome Alex!
Alex Young: Oh thank you, it's great to be here.
Jim Green: You know, what do we mean when we use that term space weather?
Alex Young: Well, space weather is this environment in the solar system that's created by the Sun and the energy and matter that it puts out and how it interacts with all the bodies in the solar system, the planets and everything else you could think of.
Jim Green: So it's like weather here on Earth. Things happen and when they happen, the wind blows over us and there's wind in space and so that's an interesting phenomena when you look out in space you don't see that stuff
Alex Young: That's right, and so we have this sort of somewhat steady wind that's coming off the Sun, we call it the solar wind, and that's the Sun's hot atmosphere which is streaming out into space. It carries away the Sun's magnetic field and sometimes we even get these explosions, and they’re huge—almost like tsunamis—that ride on top of the solar wind and these are the more energetic phenomena that make up space weather
Jim Green: So these are things like flares and coronal mass ejections.
Alex Young: Right. So the Sun has very strong magnetic field and that magnetic field gets twisted up inside of it, much like rubber bands get twisted, they had tension, they have pressure, sometimes they get twisted enough and they snap. They snap violently, releasing energy—a flash of light, we call a solar flare, to the whole electromagnetic spectrum—and sometimes they spit out these huge blobs of material and magnetic field. Those are called coronal mass ejections, and both of those can create shock waves that excite particles to near relativistic speeds and so we get this storm of energetic particles.
Jim Green: You know, those are the kind of things, those particles you can't see but they certainly can affect everything that we do from our instruments on our spacecraft, but also for human exploration not only on the station but for when we go beyond low-Earth orbit.
Alex Young: Exactly, and they are creating this very, very dynamic but hazardous and hostile environment for humans out in space but as well [for] all our technology because all this stuff is electromagnetic and so it interacts with technology which is electric in nature.
Jim Green: Alex, what's the worst solar flare you've ever seen from the missions you've been involved in?
Alex Young: Well, the biggest one that I know of—and it actually happens to be the biggest one that was ever recorded in the space age—happened during a time period of about two weeks. From the end of October to the beginning of November we call the Halloween storms in 2003, and one of those flares that occurred just as the flaring region was rotating out of view on November 4th created what we call it an X-class flare, and this one was off the charts. It was bigger than anything we'd ever seen, and in fact our instruments couldn't even record it so we had to estimate how big it really was.
Jim Green: So when these flares take off and they start accelerating particles does that happen in all directions or is it very directional?
Alex Young: Well flares, the light itself is not directional, it's pretty isotropic. So if you see it—anywhere that region is visible on the Sun you will see it. But the particles, those are very directional. They are created by jets and that's actually those particles, are actually slamming into the Sun, creating the light, then they're streaming out into space. But those are very focused.
Jim Green: You know that other phenomena you mentioned, that coronal mass ejection, what's the worst CME you've ever seen?
Alex Young: Well the worst CME I've ever seen happens to be again the biggest we've seen in the space age. On July 2012, we had an event, it actually happened on the side of the Sun. It was caught by one of our other spacecraft, STEREO, which are orbiting the Sun, they're not looking from the Earth-facing direction, we measured this at a phenomenal 3500 kilometers per second. That sounds like a lot—and it is—and it's especially a lot for CMEs. It's the biggest, fasted one we've ever recorded.
Jim Green: So these are bubbles of reconnected magnetic field and in those bubbles are all the atmosphere that it captures and it just sort of lifts off and flies at us.
Alex Young: Exactly. And the crazy thing is that they're really huge--they start off bigger than mini-Earths in size and they quickly expand as they're moving away from the Sun, and very quickly they can then fill huge portions of the inner solar system.
Jim Green: Ninety degrees or a hundred and twenty degrees in size as they pass by the Earth.
Alex Young: Yeah, they're just phenomenal. And they're carrying all of that material, billions of tons of material as well as the magnetic field of the Sun inside of it.
A solar flare erupts from the Sun in September 2017.
Credits: NASA/SDO/Goddard
Jim Green: So you know, as a young research in my particular field, that's where I take over. And we found that you know when those coronal mass ejections hit the Earth's magnetic field, we always see aurora. Now a CME may or may not hit the Earth but when they do, we're in for a beautiful dazzling display of auroral lights.
Alex Young: And it's amazing. And that's the first sign that we can visually see and experience of what's happening. But there's so much more that happens when all of that stuff is interacting with the magnetic field and this kind of tear-shaped bubble around the Earth we call the magnetsophere.
Jim Green: As you were talking, it comes to mind you know over the space era, the 40, 50, 60 years now where we've been putting these puzzles together and trying to understand space weather and get an even bigger picture of it, have we seen everything the Sun can put out in space weather?
Alex Young: Most definitely not. And you know when we think about it, we have seen not even a blink of an eye of the life of the Sun. So much has been happening, the Sun when it was younger it was far more active, and we've really only seen a little bit, we know from looking at historical records—both things that humans have recorded in terms of aurora they've seen that there are huge storms. But we also see signatures in radioactive elements, carbon-12, beryllium-10. These are things that are left by nuclear reactions in the atmosphere with particles that we can see these traces in things like ice cores and tree rings and we know there have been much bigger events in the past.
Jim Green: You know, what are some of the big historic events that we've been studying?
Alex Young: There have been a few in the modern age, in the space age. The one that I talked about, the whole series during October/November 2003, the Halloween storms. A very famous one, in 1989, March, that was when there was actually a storm that caused a power outage in Quebec, very well known. But the big one that most people try to refer to is what's called the Carrington Event. And that was seen by Richard Carrington in England in September 1859. There were a series of events and he saw the first white-light flare. So a solar flare visible in white light with a telescope from a sunspot and then a few days later, they observed aurora here on Earth. And that's the first time they made the connection between these magnetic eruptions on the Sun, the flare, and something occurring here on Earth.
Jim Green: Yeah actually scientifically, one would think that that is the start of the beginning of understanding some aspects of space weather. So Carrington was an astronomer at night and during the day he sketched sunspots. And how the story goes, as he was sketching the sunspot, it actually came out of focus off and on and he worked hard trying to focus it, couldn't get it focused. And then he realized, “This is a real event I'm looking at.”
Alex Young: Right
Jim Green: So he ran all over the observatory looking for people to take him up to the telescope. But this was at 11:30, they were all at the lunch, and so he had to discover it on his own. But fortunately another astronomer also looking at the Sun at the same spot saw it too.
Alex Young: Right, and so this is the beginning of the modern age of space weather and it's still to this day, the key event that everybody compares to when they talk about a big space weather event and the kinds of things that space weather can do.
Jim Green: Yeah and one of the reasons for that is as you mentioned, indeed he saw the reconnection occurring just above the Sun spot and that's what the flare started to do, and then a coronal mass ejection lifted off. Seventeen hours later, there was the auroroa. Now coronal mass ejections, take 80 hours typically to go from the Sun and so seventeen hours, this thing was really moving. And it had an enormous amount of mass and then the aurora was observed cutting right through the United States, through Mexico, and down into Central America. So a pretty spectacular event.
On July 5, 2017, the Solar Dynamics Observatory watched an active region — an area of intense and complex magnetic fields — rotate into view. During its 13-day trip across the face of the Sun, the active region put on a show for several NASA Sun-watching satellites, producing several solar flares, a coronal mass ejection and a solar energetic particle event.
Credits: NASA’s Goddard Space Flight Center/SDO/SOHO/CCMC/SWRC/Genna Duberstein, producer
Alex Young: And this was a really cool event for a lot of reasons and we've seen similar things. Even with this July 2012 event, the speeds are comparable...about 17 hours for it to reach about the distance from the Sun to the Earth.
Jim Green: Now that one didn't hit the Earth.
Alex Young: That one didn't hit the Earth, that hit a spacecraft on the side of the Earth, STERO. But that spacecraft was at about the same distance. But the other aspect was we also saw this effect of multiple events where one event kind of clears out the way and then the big one blasts through and it's got this free-range just sweep through the solar system to slam into the Earth in this case.
Jim Green: Yeah so it's a double whammy, it's really two coronal mass ejections. Those regions are so active that they continually reconnect. Now, they come from really big sunspots.
Alex Young: Right, we're talking sunspots that are many times the size of the Earth. And these sunspots, the bigger they get, the more complex they get. We can see how much energy they have contained inside them that gives an indication of what sort of activity might we see.
Jim Green: So are there other events like the Carrington that we can go even further back?
Alex Young: We can, and there's been one that's been talking about recently. It's now called the Charlamagne event by some because it's estimated to be within a period of about 774 or 775, somewhere in that period during the time of Charlamagne, was first recorded in carbon-14 in tree rings.
Jim Green: Wow.
Alex Young: Now the original estimate was that this event was a 1000 times a Carrington event.
Jim Green: Wow.
Alex Young: But then, this was put out by a group in Japan, but then some other scientists sat back and tried to figure this out and they said "Something doesn't seem right here. This is just a little bit odd." So they looked at their calculations, realized that they didn't calculate for a very focused particle event and they treated it as a giant bubble around the entire Sun. And it turns out it wasn't a 1000 times bigger, but still 10-20 times bigger than the Carrington event. And that's just massive.
Jim Green: Well, what would happen to our technologies today if an event like that occurred?
Alex Young: Well it could be quite catastrophic and there have been studies by the National Academies, estimates certainly billions and billions of dollars of damage, estimates up to even trillions of dollars because it would have such a global impact on our technology infrastructure. We could see power outages across the globe and in interconnected power grids especially. There would also be impact to communications, but another aspect--satellites. We would possibly lose many satellites.
Jim Green: Yeah, so the modern day technologies are kinda susceptible to these space weather effects.
Alex Young: And one of the aspects about this is that we're now in an age with technology we didn't have even during 2003, and certainly not during 1989. We've been in a relatively small solar cycle...that's the 11-year activity cycle. So we actually don't really know what a massive or strong solar event would do to the infrastructure that we have today.
Jim Green: So, now that we know about this and we're becoming much more aware of how active the Sun could be because it has been more active in the past, how can we protect our technology here on Earth?
Alex Young: Well there are a lot of things we can do. One is simply prediction. That is, trying to make some sort of estimate of when an event is going to occur. Now as you mentioned, CMEs take some time to get here. Now as far as a solar flare, there's not a lot you can do. Once you see it, it's here. There you just have to be prepared for fast reaction time, knowing that you have a spacecraft, there's activity on the Sun, and what kind of adjustments can you make to the spacecraft flight in flight control. So we're studying things like drag and what not to better understand that.
But the other things we can do is when we talk about the impact on the power grids, we can improve the power grids themselves, improve the infrastructure, and even when we know an event is coming, we can do simple things like turning the power grid off for a short amount of time--what we call a brown-out. It's just like if you knew there was a lightning storm coming to your house, the first thing you would do is unplug your stereo.
Jim Green: Right, in fact how it affects our power grids is really because of the aurora. The aurora has huge currents that are in the ionosphere so as they pass overhead, they induce other currents in our power grid that aren’t usually there and therefore they can overload the transformers, burn them up, and that's what causes the massive power-outages.
Alex Young: Exactly, because these currents are looking for places to travel through, large conductors. And you know we also see not just this happening in power lines, but you even see these large currents conducting through pipes, pipelines.
Jim Green: Oh right, pipelines.
Alex Young: And that can actually cause corrosion to increase in pipelines.
Jim Green: We talked about these massive coronal mass ejections that occur, sometimes they hit the Earth, sometimes they don't. But you know, we've got other planets out there.
Alex Young: That's right!
Jim Green: So what happens to them?
Alex Young: Well, they definitely interact with all the bodies in the solar system and they have had impact over the years. We now have had a mission called MAVEN, which has been studying Mars for a long time looking at atmospheric loss. We believe that over billions of years, solar wind and coronal mass ejections have slowly stripped away the atmosphere. And the atmosphere we see today on Mars is not the atmosphere it used to have.
Jim Green: Right.
Alex Young: But the other aspect is “What is the magnetic field of those different planets?” Some planets like Mars don't have a magnetic field, a global magnetic field right now. Venus, in addition. So the kind of magnetic field determines the interaction that's going to occur. But it definitely occurs with all of the bodies in the solar system.
Jim Green: Do you think there's a little bit of a connection with space weather and the importance for the formation of life in our solar system?
Alex Young: Absolutely! One of the things we know is the Sun has changed over time. It was much dimmer in the past, spinning much faster, but it was also much more active. We estimate the early Sun was producing many Carrington-like events on a daily basis.
Jim Green: Wow.
Alex Young: But also the spectrum of that star was different. We get much more UV, much more X-Rays, so all the planets were being bathed by huge amounts of radiation. And this has had an impact on how atmospheres themselves form. This radiation is interacting with these atmospheres, changing how they evolve, and it could have had an impact on the energy source itself needed to spark life. Because as I mentioned, the Sun was dimmer and we have what we call the [Faint] Young Sun Paradox. So did we have enough light, enough energy to support life? But there are other energy sources. The particles, not just visible light but the X-Ray and UV. So these are all pieces of the puzzle that we have to take into account.
Watch this movie to see how energy from our young sun – 4 billion years ago -- aided in creating molecules in Earth's atmosphere that allowed it to warm up enough to incubate life.
Credits: NASA's Goddard Space Flight Center/Genna Duberstein
Jim Green: Yeah, so the Faint Young Sun Paradox means that [the Sun] was very dim in its past, and the paradox what that’s all about of course is that we know early on that Venus, Earth, and Mars had an enormous amount of water and yet it had so much energy from other sources than just the visible light.
Alex Young: Right and the cool thing is you know we've always talked about the Goldilocks Zone, this region where it's not too hot, it's not too cold, thinking in terms of liquid water. Well what all of this research has now shown us is that that whole idea, "what is it to be habitable?" is much more complex. And we have to understand the activity of the star and all the other energy sources that it's producing to really define what we mean by "habitability" for planets in our solar system as well as exoplanets.
Jim Green: Yeah, so the study of space weather has got to factor that in. And so that really is really all about an evolution of the central star. So as you mentioned our star, the Sun, was rotating much faster in the past, it was dimmer but all kinds of other things were going on. How is it going to continue to evolve? What are the next steps?
Alex Young: Well, it will continue on the course that it's on right now for quite a while but eventually, inside the Sun it's currently using as its fuel source hydrogen, which it's turning into helium. Eventually once it uses all that up, it'll turn to the helium and start fusing it. And it works its way up the periodic table to a point where it can't fuse anymore elements and at that point, it starts to change. Its outer atmosphere starts to expand, it shifts more and more and more towards a red star, much like the star in Superman, at Krypton, and it is what we call a red giant. And it starts to fill the inner solar system.
Jim Green: We know about these because we can see stars that are like that as you describe, red giants and other evolved stars that have about the mass of our own Sun. So it's gotta be connected, it's a normal process of the evolution. And now we have computer codes that actually calculate that over time.
Alex Young: Exactly. I mean, the coolest thing about it is just recognizing that we are living in such a small little period, a snapshot, of what's going on. And as we understand how the planets have evolved, we have to understand how the stars evolved and connect all those pieces over time.
Jim Green: You know one of the things that I love to do when I talk to my colleagues is really try to understand how they got into this field. What were the events in their life that really got them excited about their science, gave them that gravity assist that propelled them forward to become the scientist they are today.
So Alex, what's your gravity assist?
Alex Young: Well, it's a multi-part assist. It's a couple little tiny pushes and then one giant push. I started off, when I was a young kid I saw the original Star Trek in syndication, and I was fascinated by this idea of exploring space and especially the character Mr. Spock. The scientist on the Enterprise. And so I thought this would be so cool to be able to do that. And then around the same time I saw a show by Carl Sagan called Cosmos. And he took you around the universe in a space ship. He had his own spaceship and he explored and I started to see, hey I can actually do this. I can actually be an explorer like Mr. Spock. But I can do it in real life and study the universe from here with telescopes and spacecraft. And it was an exciting time because it was the early 1980s so Voyager results were coming out, I was writing to NASA and they were sending me pictures from Jupiter and Saturn.
Jim Green: Cool, cool.
Alex Young: And at the same time I was getting specs for the space shuttle, they were just beginning with the launch of that, so all this was happening and as I slowly slipped into high school. And my dad was an art professor, and one of his colleagues was a physics professor. And they made a deal. The physic's professor's daughter wanted to study art. And I wanted to study physics. So they said, if we can swap and in the afternoons and go and meet with each other and learn.
So I went and met with the physicist while his daughter met with my dad.
Jim Green: Wow!
Alex Young: And I learned about physics. He helped me, I built a laser and went to the science fair and really got into all this. This sort of came together finally, and that was the piece that just shot me out. That was the really, really serious assist.
Jim Green: That's fantastic. Well Alex, I really enjoyed our time today talking about the Sun, certainly one of my favorite subjects. I really appreciate you here giving us your wisdom and letting us know what's happening in the field today.
Alex Young: Well thank you and I am so excited that you had me here.
Jim Green: Join us next time as we continue our exploration of NASA science. I'm Jim Green, and this is your Gravity Assist.
Last Updated: Sept. 11, 2018
Editor: Gary Daines
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