Date: March 29, 2011

Title: Solar Activity and Space Weather

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Podcasters: Mark Webb and Katie Peterson talk to Dr. Michael Smutko of the Adler Planetarium and Northwestern University

Organization: Adler Planetarium – www.adlerplanetarium.org

Description: Solar activity has started to finally pick up! Mark Webb and Katie Peterson talk to Dr. Michael Smutko of the Adler Planetarium and Northwestern University about what that means. NASA declared 2011 as the Year of the Solar System so we’re talking about space weather and the Sun-Earth connection. What are sunspots and how do flares differ from coronal mass ejections? And what is space weather and how does it impact us here on Earth?

Bio: The Adler Planetarium – America’s First Planetarium – was founded in 1930 by Chicago business leader Max Adler. The museum is home to three full-size theaters, including the all-digital projection Definiti Space Theater, the Sky Theater which utilizes a Zeiss optical projector, and the Universe 3D Theater. It is also home to one of the world’s most important antique instrument collections. The Adler is a recognized leader in science education, with a focus on inspiring young people, particularly women and minorities, to pursue careers in science.

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Transcript:

Mark
Welcome, to a special edition of the Adler Planetarium’s bi-weekly podcast, Adler Night and Day. The Adler Night and Day podcast provides listeners with a glimpse of what they can see in the night sky as well as updates on recent solar weather and riveting conversation. For the 365 Days of Astronomy, we’ll be concentrating on the riveting conversation. I’m your host, Mark…

Katie
And I’m Katie. NASA has declared 2011 as the Year of the Solar System. So we thought we’d kick of our 365 contributions with Dr. Michael Smutko of the Adler Planetarium. And we’d talk a little bit about space weather and the Sun-Earth connection. Welcome, Mike.

Mike
It’s great to be here. Thanks Katie and Mark!

Mark
It’s good to have you back!

Katie
So let’s get right into it. What is space and solar weather?

Mike
Well, Space weather is in some ways is a lot like weather here on Earth. You go out side your house and the weather is the stuff that happening outside. Space weather is the conditions, the events that are happening outside the Earth, outside the atmosphere of the Earth. Primarily caused by the Sun, the Sun dominates our solar system. The Sun provides not just light energy, but it provides a steady stream of particles to the whole solar system when those particles reach the Earth and interact with the Earth, then we get what we call space weather.

Mark
Okay, I’ve heard that solar weather happens in a cycle. What is that, and what is Solar Maximum and Solar Minimum? How does all of that work?

Mike
Well, it’s been known that the Sun goes through variations in its activity level, actually over the course of about eleven years. So, you’ll go through a period where there’s lots of activity on the surface of the Sun, lots of sunspots, lots of prominences, lots of flares and things like that. To maybe five years later where there’s not really much going on at all and then in another five years it gets very active again. So, over the course of about eleven years the Sun goes through these variations. And these variations have been observed for hundreds of years going back into history.

Katie
So, what defines the boundaries of a named solar cycle? We’ve just entered solar cycle 24 and we sometimes have an appearance of spot from solar cycle 23. How’s that possible and what defines that start and stop?

Mike
Well, the solar cycles are related to magnetic fields. Invisible magnetic fields that thread through the outer layers of the Sun. And these fields get wrapped up and when they get wrapped up, that’s what causes a lot of the sunspots and related activity. No it turns out that the fields, when they soft of get knotted together, it doesn’t happen all over the Sun at the same time. You actually find at the beginning of a solar cycle, as the activity starts to increase, you see lots of activity at the higher latitudes. You know, sort of the equivalent of the northern latitudes or the very southern latitudes here on Earth. And then, over the course of that eleven year cycle, as you get farther into the cycle, the sunspot activity gets to lower and lower latitudes, closer to the equator on the Sun. We say that a new cycle has started when we start seeing sunspots at high latitudes again. And sometimes you’ll have a few leftovers, a few lingering sunspots from the previous solar cycle. Even though you’ll have a few sunspots at the equator while the majority of the new spots are forming at higher latitudes.

Katie
So, what does it mean when you might be reading a report and they’re talking about spot that has a different polarity?

Mike
So sunspots are related to the magnetic activity on the Sun. And, just like if you’ve ever played with a bar magnet in school, you know that magnets have a north pole and a south pole. One side that wants to face the North Pole of the Earth and another that wants to face the South Pole. Sunspots are similar; they also have a magnetic polarity. They have a North Pole and a South Pole and it turns out that over the course of a solar cycle, that in a given solar cycle, all of the sunspots will be orientated in the same direction. That is, they’ll all have their North poles facing in one direction as the Sun rotates around. The next cycle, it actually flips the other way around so it leads with the South Pole! Instead of the North Pole.

Katie
Hmm…

Mike
Yah, it’s not obvious why that would happen. But again, it’s this eleven-year cycle. All of these magnetic fields get wrapped up and twisted within the deeper layers of the sun. And in fact, the true cycle isn’t eleven years it’s actually twenty-two years. Because after the first solar cycle, the magnetic fields all flip in the Sun and then it stays flipped for eleven years and after the second eleven years it flips back to where you started from. So if you actually want to go through a full solar cycle it takes more like twenty-two years to get all of the magnetic orientations the same way you started with.

Katie
Any idea why that happens?

Mike
Other than it’s really complicated?

Katie
(laughs) Maybe more than we can get in to in one podcast?

Mike
More than we can get into in this podcast! The equations used to talk about the stuff that happens on the Sun are called magneto-hydro dynamics. And it’s this merging of the equations that govern electromagnetic fields, as well as, the equations that govern fluids and plasmas. It’s really nasty stuff. It takes the bravest of astronomers to dive into those types of equations and it’s tough stuff to calculate. It’s even tougher to observe though because to be able to decide between one theory and another competing theory about how the sunspots form we need to have really precise, detailed observations and we’re just starting to get that information now, these days, in modern times.

Katie
Okay, so the last solar minimum. The one we’re easing out of right now was really, really long. Comparative to the last few cycles. Any idea why some cycles are more intense, be it in their maximum or their minimum? And then some are just sort of closer to an average? No, unfortunately, no. We don’t have any good explanation of why a particular solar minimum would last longer than an average one. Again, the weather analogy is a very appropriate for what when we’re talking about the Sun. You know, meteorologist here on Earth can say, “Oh, the temperature is so and so and humidity is this then there’s a good chance of thunderstorms.” But there may or may not be thunderstorms on that given day. Solar activity is very similar to that. We know that we’re in a minimum phase or in a maximum phase. We can maybe see lots of sunspots but the specifics are frustratingly hard to predict on the Sun.

Mark
Okay, so I think most of us have probably seen pictures or video of solar flares. Are those the same things as Coronal Mass Ejections and are they related to sunspots?

Mike
All of these phenomenon are related and they all feed back to this idea of magnetic fields. Magnetic fields on the Sun are like rubber bands inside the Sun. As the Sun rotates around these magnetic field lines get all tangled up and stretched out. So if you think of a ball of rubber bands being twisted around from the middle, eventually you store up lots of energy and if you go too far the rubber band will snap. That’s exactly what happens on the Sun with these magnetic fields. Magnetic field lines literally snap and do what’s called a reconnection and that releases tremendous amounts of energy. That’s often exhibited in what’s called a solar flare. And solar flares are amazingly powerful events. They can have the equivalent of megatons and megatons of TNT. Much more powerful than anything that’s ever been exploded on the Earth. They are also related to things called Coronal Mass Ejections, where that’s literally where a large amount of material from the Sun that gets flung off into space by this explosive event but it’s actually not clear if the flare cause the mass ejection or if they’re sort of symptoms of the same phenomena. We’re trying to figure that out, today, with modern satellites.

Katie
Okay, you just talked about the energy in a solar flare. Now that we’ve started getting back into, or solar activity has begun to increase. We’ve seen the first X-flare of the last four years; we’ve had a handful of M-class solar flares. When I say X-class and M-class, and C-class, B-class… what am I talking about?

Mike
The flare classification system is a rating of the energies given off by flares. A, B, C, and then it jumps to M, and X is the most powerful. It’s a rating scale similar to the ones for earthquakes or tornadoes, things like that. It’s an estimate of the amount of energy contained within one of these solar flares and they’re actually measured by one of the same satellites that study the weather here on Earth. The GOES satellites. They have some instruments pointed down taking measurements and photographs of clouds and systems here on Earth. They have other systems that are X-Ray camera systems that measure the particles coming from the Sun. That’s how we get an estimate of the energies in these flares.

Mark
Okay, so sunspots… some of them are small and then other ones are like conglomerates of multiple spots it seems like, Uh, is there a classification for those and why are they different in that way.

Mike
Again, we’re not really sure why you would get a small sunspot verses a large group of sunspots. There’s a relationship between the sizes of sunspot groups and just general solar activity. When the Sun is more active, when it’s closer to solar maximum you can expect to find a lot more and a lot bigger active regions on the sun, just because the magnetic field tangling is more intense, stronger, there’s just more energy stored within those larger sunspot groups in active times, when the Sun is active. But, you know… there’s a random variation with that too. You don’t always get giant sunspot groups when the Sun is active and you don’t always get small sunspots when it’s at it’s minimum but you know that’s a decent average.

Mark
I’m trying to create a model of how this magnetic field works and the analog of what I’m working with is kind of how magnets work here on Earth when they’re lined up correctly they’re sort of at rest but if you twist them off axis they want to sort of snap back. Is that similar to..?

Mike
Yes, actually, that’s a very good analogy. If you’ve got the magnets all lined up they’re sort of a minimum energy state. They’re stable, they’re happy lined up the way they are. If you start twisting them so that they’re at different orientations, they do want to snap back and that’s a little bit like what’s happening during a flare. You have all of these magnetic field lines that have been distorted out of shape by the rotation of the Sun and convection inside the Sun suddenly all snap back to the orientation, you know, sort of a minimum energy orientation and that energy has to go somewhere. Energy is conserved so it gets flung off the surface.

Mark
All right, so, we’ve talked about space weather and does it really effect us here on Earth? And, is it like Earth weather? Can we forecast weather on the Sun?

Mike
We can and unfortunately just like Earth weather it’s very hard to do. We can try. Earth weather is effect by what the Sun is doing, is effected by these particles streaming. During very active times lots more particles will stream off the Sun at very high speeds. These particles can have speeds of a million miles per hour and very energetic particles and when they reach the Earth they interact with the Earth’s magnetic fields and they tend to spiral around the Earth’s magnetic field lines, which, as it turns out, are concentrated at the north and south magnetic poles. The most obvious way of detecting this activity is by the Northern Lights, when you see Northern Lights they’re nothing more than these charged particles interacting with the nitrogen and oxygen atoms in the Earth’s atmosphere giving us these really nice colors. That’s kind of the more benign interaction. It can be a lot more severe than that. Uh, astronauts in space during a strong flare or Coronal Mass Ejection are literally in danger of their lives. They can get radiations poisoning from these energetic particles and it’s a serious consideration for those long-term space missions. How do you protect astronauts from these types of events? But even here on Earth there other more dramatic effects. In 1989 there was a very famous blackout across parts of Canada, caused by a big solar flare, and a big Coronal Mass Ejection. So many particles streamed toward the Earth that power lines started to act like antennas for them and there were currents generated in these power lines that they were just never intended to handle and parts of Canada were blacked out as a result.

Mark
Yah, those are all networked together.

Mike
Yep, absolutely. It’s one big interconnected world now

Katie
On our, on our note of doom. I will wrap this up! Thanks for joining us Mike.

Mark
Thanks, Mike

Mike
My pleasure

Katie
And I’d also like to thank the listeners of the 365 Days of Astronomy podcast. To listen to full episodes of Adler Night and Day go to www.adlerplanetarium.org/podcasts. You can also check the Adler out on Facebook, YouTube, and Twitter. The Adler Night and Day podcast has a blog! Check us out at adlernightandday.tumblr.com

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365 Days of Astronomy
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