Date: December 29, 2011
Title: Solar Activity and the Upcoming Cycle
Podcaster: Katie Peterson
Organization: Adler Planetarium
Links: www.adlerplanetarium.org
www.adlerplanetarium.org/podcasts
Description: Solar Cycle 24 has begun and the Sun is finally showing signs of activity. This upcoming solar maximum is predicted to peak in 2013 but be much more subdued than the last several cycles. What are scientist learning now that’s helping them to make predictions about the next solar cycle?
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 featuring a ultra-high resolution digital planetarium, 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.
Visit our website: http://www.adlerplanetarium.org
Sponsors: This episode of “365 Days of Astronomy” is sponsored by NO ONE. Please consider sponsoring a day or two so we can continue to bring you daily “infotainment” into the new year.
Happy Holidays!
Transcript:
Katie
Welcome to a special edition of the Adler Planetarium’s bi-weekly podcast, Adler Night and Day. Adler Night and Day podcast provides listeners with a glimpse of what they can see in the night sky, updates on recent solar weather, and awesome conversation. For the 365 Days of Astronomy we’ll be dispensing with everything but the conversation. And without further ado, I’m your host Katie and today I’m joined by Dr. Michael Smutko and we’ll be talking about the Sun. Welcome, Mike…
Mike
Thanks, Katie. It’s nice to be back.
Katie
So we started our 365 contributions at the beginning of the year with Mike because 2011 is the Year of the Solar System, and we’re going to wrap it up with Mike again because there’s been some interesting new reports about the Sun and we just… It’s Adler Night and Day! We like the Sun!
Mike
And I like the way we’re coming full circle.
Katie
It does
Mike
We’re coming back we’re we started!
Katie
So, solar weather has really kind of revamped. But, before we really get into that stuff, let’s just go over, what are the basics of solar activity. So, we’ve go sunspots, probably the most common activity to your average Sun watcher. Um, what are sunspots?
Mike
Well, sunspots are basically colder regions on the surface of the Sun. When people look at the Sun, it’s fairly simple, it’s this big yellow ball in the sky and it’s powered by nuclear reactions, but the details of what happens next actually get really complicated and they have to do with these invisible magnetic fields, similar to the magnetic fields that point a compass needle north here on Earth, the Sun also has magnetic fields. And one of the properties of a magnetic field is that they can store energy. You can kind of wind them up just like a rubber band. And the more you wind them up the tenser they get and the more energy they hold. Sunspots are caused when the magnetic field lines, within the Sun, get really tangled up and they literally act like a cork . They keep that hot gas, that hot energy from the core of the Sun from reaching the surface. So, the result is this dark spot on the surface of the Sun. Where for lack of a better name we’ve called them Sunspots for hundreds of years.
Katie
Alright, so we’ve got sunspots down. Now we get to a little bit more of the showy kind of solar activity. What are flares, what are prominences, and how do they differ?
Mike
Well, Solar flares and prominences are actually related to sunspots. They all are caused by this magnetic activity of these magnetic field lines. A solar flare happens when these magnetic field lines get so wrapped up and so entangled with each other that they literally break. They snap in what’s called a reconnection. And it can be very violent, a solar flare is very much like an explosion on the surface of the Sun. They have a whole range of energies they give off x-rays and ultraviolet light. In fact some of them can be so strong that they can actually effect the Earth’s atmosphere. Now, prominences are really pretty things to look at. The most common kind that you see in photographs look like little loops of fire coming out from the surface of the Sun. And those prominences, those loops are caused by the exact same idea, again magnetic field lines, that you played with in elementary school science experiments where you take a bar magnet and then put a piece of paper over top and then sprinkle iron filings or something magnetic on top of it. You can see that the iron filings trace out these little loops, that’s exactly what’s happening in these prominences. But now the magnetic field lines are coming out of the ball of the Sun and the hot gasses of the surface of the Sun follow those loops of energy just like the iron filings follow a magnet here on Earth.
Katie
So, what’s a coronal mass ejection and is that related to any of the activity we just talked about?
Mike
Again, it is all related. It all has to do with the magnetic fields. But a mass ejection, a coronal mass ejection is sort of a flare to the next level and even more energetic. A lot of the energy is in the form of ultraviolet light and X-rays. A CME is associated with an explosion that is so powerful that it actually throws up a lot of the Sun’s mass into the solar system, into space and some of these CMEs can eject billions of tons of solar material into space in a matter of moments or within minutes at least.
Katie
So, we have CMEs and we have the ability to monitor those and have an idea of when they’re coming at us but there’s something that’s always happening and that’s the solar wind. Can you talk about that and how it differs from materials that are ejected from the Sun?
Mike
So, a coronal flare and these coronal mass ejections are these dramatic events, these kind of “every now-and-then” events. The solar wind in contrast is a constant. It’s always there. It was actually predicted theoretically but a guy at the University of Chicago named Eugene Parker in the 1950s. And people said “No, that’s ridiculous, the Sun doesn’t behave like that. The Sun doesn’t give off this wave of particles all the time.” But it turns out it actually does! As soon as spacecraft went into space on of the first things they found was, hey, wow! There’s these particles flowing from the Sun. Basically it boils down to the idea that the Sun is so hot it gives off so much energy that the Sun loses it’s outer layers. The Sun’s heat pushes away it’s own outer layers. The gravity of the Sun isn’t strong enough to hold on to all of it. And, so the Sun, evaporate isn’t quite the right word, but the Sun is sort of losing it’s outer layers, little by little, and this happens all the time. We call it the solar wind.
Katie
So, when the solar wind,.. let me back up. The solar wind is not itself necessarily a constant as it’s going. It has some variation to it as well?
Mike
That’s right, just like wind here on Earth, the solar wind gets a little stronger, a little weaker.
Katie
So what happens when, is there an impact on Earth when the solar wind is particularly elevated? Or, when we have a coronal mass ejection that is Earth directed?
Mike
Oh, absolutely!
Katie
And how does that manifest?
Mike
So, these mass ejections from the Sun, whether they’re the dramatic ones, the coronal mass ejections or the slower calmer ones of the solar wind. They’re basically charged particles, protons and electrons. When those charged particles reach the magnetic field of the Earth they actually interact with the Earth’s magnetic field, similar to the way they interact with the Sun’s. Now, on the Sun you get these mice prominences and solar flares and all that. Here on Earth the results are a little calmer. That’s what we call the Northern Lights or the Southern Lights. You get these really nice aurora. More violent eruptions on the Sun can actually cause the Earth’s atmosphere to expand outward a little bit. The energy actually starts ionizing and heating up Earth atmosphere and the Earth’s atmosphere can actually grow a little bit. This is, ya know, it sounds kinda cool but for people who operate satellites and spacecraft it’s a problem because that increases friction for satellites in space and so satellites actually start slowing down and they can come crashing down to Earth sooner than originally planned during times when the Sun is more active than usual.
Katie
Now, you just mentioned the Northern Lights which are also known as the Aurora Borealis and the key there being, in the Northern Lights, the term Northern. Just a few months ago we had a display of the Northern Lights that was witnessed as far south as Atlanta and a lot of the southern states. What led up to that, how did that occur?
Mike
Well, the reason that they’re called the Northern Lights and the Southern Lights, cause you can see them equally well in the Southern hemisphere, is that again, it relates back to these magnetic fields. The magnetic field of the Earth is strongest near the magnetic poles of the Earth.. The north and south magnetic pole. And that happens to be in northern Canada. So, when all these charged particles from the Sun reach the Earth’s magnetic field they tend to get concentrated near the magnetic poles. So that why it’s easier to, or more common to, see these aurora near the magnetic poles of the Earth. But in the case of a really strong eruption, if the conditions are right and the eruption is pointed at Earth at just the right direction and all that then the aurora can be seen ya know, much further south than just Canada or Greenland or places like that. As you mentioned, Atlanta, or even further south people have seen aurora from time to time.
Katie
So, we’ve now seen this definite uptick in our solar activity since the time you came on in the beginning of the year to now we’ve had several X flares, we’ve had this display of the Northern Lights in un-typical southern latitudes and we’ve seen we’ve seen this increase. But, there have been some reports that have come out that have been quite interesting. I’m going to pass it over to you and let you talk about that for a minute.
Mike
Yah, absolutely, so… as you, as most of the listeners know, the Sun goes through an activity cycle. It goes through a period of very strong activity where you have lots of sunspots visible, lots of flares and eruptions and then it gets calm, it kind of settles down for a while and then it ramps back up and gets exciting again. This cycle of activity to boring back to activity again typically takes about 11 years but there’s, the Sun isn’t listening to it’s own kind of rules anymore. Our current solar cycle is actually, we got stuck in a minimum for several years longer than astronomers had expected. Normally the Sun is very reliable. It peaks, it gets quiet, it peaks again but for whatever reason we got stuck in a minimum for a long time and as you said it looks like the Sun is getting more active, these aurora are, it’s like “finally!” it’s behaving like we’re expecting even if it was a little late.
Katie
And we were supposed to peak this year, correct?
Mike
That’s right, but the latest studies say that our peak might actually come a little later. It might actually happen in 2013. And they also say that the peak in 2013 might be weaker. That the Sun won’t get as active as you would typically expect during an active period. There was, this summer, in June of 2011 there was meeting of the solar physics division of the American Astronomical Society. And at this meeting several different individual groups presented results saying that not only is it true that the Sun seems to be weaker this time around than you’d normally expect but the presented evidence that our next solar cycle, right, so the next 11 year cycle, not the one that we’re currently in but the very next one. It turns out that there are indicators that experts can study on the Sun, there are actually people that can actually study the core of the Sun in a similar way that geologists on Earth can study the core of the Earth with the way that earthquakes propagate and sound waves propagate, you can actually do the same kind of thing with the Sun. And these people normally can see precursors, they can see currents within the Sun itself, sort of change direction when a new solar cycle is beginning and these changes happen two or even three years before the next solar cycle is scheduled to begin. Well at this meeting over the summer, these scientists got up and presented results that not only is this cycle weaker but they don’t see any signs at all of the next cycle beginning yet. So, some of these, some of the world’s experts who have been studying the Sun are saying that there’s strong evidence that not only is this current solar cycle going to be a weak one but the next one, at best is going to be weak, at worst might not happen at all. We may be entering a period of very, very calm Sun with little activity at all.
Katie
Have we seen historically times, there’s a lot of talk during this past minimum when it stretched out for so long about, oh a repeat of the Maunder Minimum which was a very long period of inactivity. Is there any historical data that shows these smaller periods of lower activity that gives us any kind of idea of what we might be in store for? Like, what, how long may this may last for?
Mike
There have been stretches where the Sun has not been as active as you would expect. The most famous one being the one that you mentioned, the Maunder Minimum, which was a period of about 70 years in the late 1600s where no sunspots were seen at all.
Katie
That’s mindboggling, still!
Mike
And it turns out at that same period of time, the temperatures in Europe were cooler than normal too. So, a lot of people are wondering will that sort of thing happen again? Will this reduction in solar activity, if it does turn out to be true, will that also imply maybe slightly cooler temperatures here on Earth? And the honest answer is, we’re just not sure. Um, there’s still a lot about the Sun that we don’t know.
Katie
Are there any other possible implications, good and bad, of this difference in activity for us here on Earth.
Mike
Well, there is! We know for a fact that during times of solar activity, when there’s lots of sunspots, lots of flares and eruptions and things like that. That the Sun is a bit more luminous, it will actually give off a bit more energy than average and so that would imply warming temperatures here on Earth. Uh, it’s very natural to expect the opposite is true. If the Sun is very quiet you would expect less energy being emitted from the Sun and as a result perhaps the planets and the solar system would cool off us a little bit. Not dramatic amounts, just a bit. There’s also implications for particles raining into the solar system from beyond our solar system. Things called cosmic rays. When the Sun is very active the solar wind flows out beyond the boundaries of our solar system. It flows out beyond Neptune, it flows out beyond the Kuiper Belt and where all these comets are lurking out there waiting to come in to the solar system and it actually kind of makes a bubble and that bubble is caused by the solar wind helps keep out some of those particles from space. These energetic particles. Um, when the Sun is not as active it changes the boundaries of this bubble, the bubble actually shrinks a little bit . Um, it also has effects with the Earth’s magnetic fields when the Sun is very strong, when it’s emitting lots of activity, it changes the shape of the Earth’s magnetic field slightly and that can have effects on the upper atmosphere on satellites, on communications, and stuff like that. So, yah! There’s more to the Earth-Sun interaction than just whether we have Sun today and clouds tomorrow.
Katie
That’s really fascinating and I’m really glad that you came by to help us wrap up our year’s contributions to the 365!
Mike
Well, thank you very much. It was great to come back!
Katie
And I’d also like to thank the listeners of the 65 Days of Astronomy podcast. To listen to full episodes of the Adler Night and Day podcast go to www.adlerplanetarium.org/podcasts. You can also check out the Adler on Facebook, YouTube, Twitter and more. The Adler Night and Day podcast has a blog! Check us out at www.adlernightandday.tumblr.com.
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365 Days of Astronomy
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