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IRA FLATOW, host:

You're listening to Talk of the Nation: Science Friday. I am Ira Flatow. And as we talk about problems on Wall Street, the economy, global warming. You name it. Traffic this weekend. I've got something else for you to perhaps worry about. And that is something unusual going on with the solar wind. The latest measurements of the solar wind by the Ulysses space probe - it's in polar orbit around the sun - indicates that the million mile an hour plasma emanating from the sun called the solar wind is weaker. It's weaker than they've seen it since the beginning of the space age. It's like 50 years or so, like that. And of course, that's - as I say, 50 years and a lifetime of what, a five-billion-year-old sun. So what? Maybe it's just an anomaly. Might the softer wind, though, have an impact here on earth? Or maybe astronauts heading towards international space station?

Some of the answers we hope to get from our next guest, David McComas. David McComas is principal investigator for the Ulysses Solar Wind Observation. It's over the poles, and it's called SWOOPS. It's a big experiment, the SWOOPS experiment. He's also a senior executive director of the Space Science and Engineering Division at Southwest Research Institute in San Antonio, Texas. Welcome to Science Friday.

Dr. DAVID MCCOMAS (Principal Investigator, SWOOPS Experiment): Thank you very much. Good afternoon, Ira.

FLATOW: Good afternoon, Dr. McComas. Should we be worried about this?

Dr. MCCOMAS: Well, I don't think we should be worried. It's very interesting what's happening with the sun and the solar wind, but I don't think it portends any particular crisis at least in the near future.

FLATOW: Give us an idea exactly what the solar wind is first.

Dr. MCCOMAS: OK. So the solar wind is the outer atmosphere of our sun expanding out into space. When you see, for example, an eclipse or a photo of an eclipse where the bright surface of the sun is blocked out, you can see around the outside of that a dimmer region, which we call the corona. The corona is basically the atmosphere of the sun. And at the outer boundaries of the corona, a material is constantly evaporating out into space, all directions all the time. It forms an ionized gas that scientists call plasma. An ionized gas, which just means the electrons and ions are separated from each other. And it flows out of millions miles per hour in all directions all the time from the sun.

FLATOW: And it's just a normal thing we've known about for billion - I mean, it's happening for billions of years, right?

Dr. MCCOMAS: It's been happening for billions of years.

FLATOW: And we discovered it many years ago.

Dr. MCCOMAS: It was first inferred from observations of comet tails in the - I think the 1950s, but it wasn't directly measured until the very early 1960s.

FLATOW: Does it have any protective effect?

Dr. MCCOMAS: So, the solar wind extends out, blowing out all these direction at a million miles an hour, and it basically inflates a bubble in space. And that bubble is something that we call the heliosphere. Helius, from the Greek for sun and sphere, just the region of influence. So the heliosphere is the region of influence of our sun. And basically, the expanding solar wind blows this bubble and pushes out the rest of the galaxy. And at a very great distance about three times farther than the farthest planet, is the edge of this bubble. And beyond that, is the local part of the galaxy. The local part of the galaxy is filled with radiation that we call galactic cosmic rays or galactic cosmic radiation. And basically, this protective bubble formed by the solar wind excludes the vast majority of these galactic cosmic rays. So yes, it does protect the inner solar system quite a bit from the high-energy radiation outside in the galaxy.

FLATOW: So does that mean if we have a weaker solar wind, more of those potentially harmful rays, would you say that it might be heading in our direction?

Dr. MCCOMAS: That's true. As the solar wind weakens, the - it's sort of like a tire that's being inflated or a balloon. If there's less pressure on the inside, the pressure on the outside makes it a smaller - makes the heliosphere smaller and allow some more of those cosmic rays to make their way into the inner heliosphere to the planets and to the region of space that we care the most about.

FLATOW: But we have our own earth's magnetic field that might protect us.

Dr. MCCOMAS: Right. So we on earth are actually protected two more ways. We have our own magnetic field, which forms something we call a magnetosphere around the earth, the region of influence that the earth's magnetic field dominates. And inside of that, we have our own atmosphere, and the galactic cosmic rays are largely stopped in the earth's atmosphere. So here on earth, we don't really have a problem with galactic cosmic rays, but if we were for example, astronauts on our way to Mars...

FLATOW: Mm-hm.

Dr. MCCOMAS: We wouldn't have any of those protections, and the trip for example to Mars takes many months, and so in that sort of environment it is a concern just exactly how intense the galactic cosmic radiation making it's way into the inner heliosphere actually is.

FLATOW: So it wouldn't affect astronauts in the space shuttle or the space station

Dr. MCCOMAS: So they're protected by the earth's magnetic field and magnetosphere, their not protected by the atmosphere

FLATOW: Mm-hm.

Dr. MCCOMAS: But they're still very well protected by the magnetic field of the earth in Low Earth Orbit where the space station is.

FLATOW: Now the instruments on your list is - have they been sending back information over the years, and do you see a gradual drop in the wind or was there something that sort of spiked?

Dr. MCCOMAS: Yes, so first, maybe I should just tell you a little tiny bit about Ulysses. It's an amazing mission, it's the only mission that humanity has ever sent out of the plane of the planets. Basically all the planets orbit around the sun pretty much on a plane which we call the ecliptic plano, the equatorial plane of the sun.

Ulysses was launched in October 1990 by a joint team at the European Space Agency and NASA joint mission. Tremendous international mission launched in October 1990, flew out Jupiter and used the intense gravity of Jupiter to sling it out of this equatorial plane, and go over the poles of the sun. And what's really important about our observations from Ulysses is, it doesn't just tell us about the solar wind here locally, but it tells us about the solar wind at all latitudes. So, with Ulysses we've been able to understand this expanding solar wind as a three dimensional structure...

FLATOW: Mm-hm.

Dr. MCCOMAS: And not just down in the equatorial plane.

FLATOW: Mm-hm.

Dr. MCCOMAS: So, we've been making solar measurements from Ulysses for 18 years now, and we've been going over in this polar orbit for the last 16 years since October - since February 1992. So, what we've observed over those 16 years is pretty much a slow and steady decline.

There are smaller scale ups and downs to it, but on average, sort of a continuing decrease over those 15 or 16 years, and that's been through the previous minimum of the sun spot in solar-activity cycle through the maximum. The last maximum of the solar-activity cycle and now through the current minimum of the solar-activity cycle. So even as the sun's output has varied on solar activity has come and gone, the overall pressure, the overall energy being put out by the sun into the form of solar wind has drop to nearly 25 percent.

FLATOW: Wow.

Dr. MCCOMAS: Yeah. It's a big change.

FLATOW: No - and no theories about why.

Dr. MCCOMAS: Well , I think we understand or some of us think we understand at least that it's associated with less magnetic flux coming up from the inside of the sun, and coming up into the solar atmosphere.

Many of us believe that that's ultimately what provides the energy source that drives the solar wind, but as to why the sun's dynamo would be putting less magnetic flux into the crone eye, and I certainly don't know and I don't know anybody that probably does.

FLATOW: Let see what our listeners have to say. 1-800-989-8255. Mark in Saint Paul. Hi, Mark

MARK (Caller): From Saint Paul.

FLATOW: Hi there. Go ahead.

MARK: I've had bit of an interest, my hobby, amateur radio, we play around with the ionosphere quite a bit, and that's reliant on the solar wind, and you look at the American reader really, they've been monitoring and we've got almost no sun-spot activity for a number of months.

The question, I'm kind of wondering, a while back I came across some NASA articles about the fact that the solar wind has been very quiet for - and there's one scientist that's predicting sort of a 50-year cycle of sorts. I was wondering if there's any knowledge about that, or prediction about that, and also is there any relation to the solar activity and our climate aspect of the global warming in some regards?

FLATOW: Good questions.

Dr. MCCOMAS: Yes, so, let me take the first part of that question. It's been a tremendously - a quiet solar minimum, the last several years, very few sun spots, very quiet conditions, quiet conditions in ionosphere, obviously you know, and the effects on your radio interest.

MARK: Mm-hm.

Dr. MCCOMAS: The thing that's interesting about the drop in pressure of the solar wind is it extended not just in the solar minimum face, but actually through the previous solar maximum. So, while we see the output of solar and the pressure of the solar wind go up and down somewhat over the solar cycle, the larger effect we've been seeing is a sort of a decrease even across the solar cycle for max to min, and so it's something going on in the sun that's changing on a longer time scale than just this 11-year cycle.

FLATOW: Spooky, Mark, huh? OK. Thanks for calling. 1-800-989-8255 is our number. So, if you had been able to observe it for longer than 50 years, or hundred years, you think you could pick up a trend or a cycle back and forth on this?

Dr. MCCOMAS: Yeah, so that's a great question which of course we can't answer, because we don't have the data. The sun itself has changed a lot over the centuries and the millennia. We know that there have been times when solar activity was very, very low, that (unintelligible) minimum several hundred years ago, and even solar maxima had very small numbers of sun spots and that sort of thing.

It was probably a case that the solar wind was weaker then, but it wasn't being measured, so there's really no way to know for sure. It is the case of course, but all of the solar winds and all of the energy of the solar is driven by the sun, so if the sun is putting out less power into the corona, you know, that will manifest itself as less energy in the solar wind.

FLATOW: Now, we're used to seeing the energy from the sun being invisible. Sunlight, it heats us up, we see it every day. Where does the solar wind come from?

Dr. MCCOMAS: So, of course the vast majority of the energy, the sun, is actually invisible light, which heats the earth...

FLATOW: Mm-hm.

Dr. MCCOMAS: And all the things that we're used to. The energy of the solar wind probably comes from this magnetic file which is produced in the dynamo down inside the sun.

FLATOW: Now the dynamo is this fusion reaction? (Unintelligible)

Dr. MCCOMAS: No. The dynamo is motion in a conducting material. In this case it's a plasma...

FLATOW: Mm.

Dr. MCCOMAS: It's a cyanized gas. And when you have motion in this conducting gas, you basically can generate magnetic fields

FLATOW: Mm-hm.

Dr. MCCOMAS: By the motion and the charged particles.

FLATOW: The sun is a big ball of gas.

Dr. MCCOMAS: It's a big ball of gas, and there are motions inside of it...

FLATOW: Mm-hm.

Dr. MCCOMAS: Which generate magnetic fields. And I mean, interestingly, I mean, the solar cycle that we see, the direction of the sun's magnetic fields flips over every 11 years. And so, for 11 years it points south and for 11 years, it points north, and back and forth.

So there's something very interesting going on inside the sun, generating this dynamo.

FLATOW: Mm.

Dr. MCCOMAS: And as that magnetic field is generated, some of it leaks out, and is submitted out into open magnetic field in the corona which then can be converted in to power in the solar wind.

FLATOW: Mm-hm. This is Talk of the Nation: Science Friday from NPR News. Talking now with David McComas, principal investigator for the SWOOPS experiment. Talking about the sun, and I guess, what you're saying is that there's less we know about the sun than we thought we did?

Dr. MCCOMAS: Yeah, that of course is one of the really interesting things about science. When you start to get data and observations, and start to understanding things better, almost always you find that the problems are harder and deeper than you thought when you started. And you know, you work your way down through them...

FLATOW: Mm-hm.

Dr. MCCOMAS: And eventually come to a good understanding.

FLATOW: Mm-hm.

Dr. MCCOMAS: But we're certainly not there yet as far as the sun goes or the solar wind.

FLATOW: OK. What about the future? Can you get a new probe that might answer some of those questions?

Dr. MCCOMAS: So, there are new probes going up every, you know, every few years that study different sorts of things. As far as the three-dimensional structure of the solar wind and the heliosphere goes, Ulysses has really been unique. And right now, while there are things that we scientists talk about as possible replacements someday, there's nothing really planned to go into a similar orbit over the poles of the sun.

On the other hand in less than a month, right now scheduled for October 19th, there's going to be a new space probe launched by NASA called the Interstellar Boundary Explorer or IBEX for short, which instead of going and traveling out to this interstellar boundary, it's actually able to make images of the interstellar boundary from the inside looking out. And it will be the first time that we'll be able to actually see this interaction between the solar wind and the galaxy. And we'll be able to see that looking all directions in space from an earth orbiting satellite.

FLATOW: It's about where Voyager is now.

Dr. MCCOMAS: The Voyagers have actually - are actually out in this region, this interaction region, close to the boundary, the edge of the heliosphere, just inside the edge of the heliosphere. And so they're making really great measurements, both Voyager One and Voyager Two, but as we were just talking about with the sun, actually the biggest that we've learned from the Voyager One and Two observations is, we didn't understand that nearly as well as we thought we did. We've mostly taken data which has, you know, caused great surprises and mysteries. You know, things we thought we understood, all of a sudden we realized, boy, it doesn't work like we thought.

(Soundbite of laughter)

Dr. MCCOMAS: And so this combination of having the two Voyager spacecraft out there simultaneously with the IBEX observations looking all directions, and getting sort of the global interaction, will be just a tremendous boom for really understanding...

FLATOW: Mm.

Dr. MCCOMAS: This global interaction between our sun and the galaxy for the very first time.

FLATOW: So tonight at dinner when people talk about this sun and the experiment, you can actually say there is something new under the sun.

Dr. MCCOMAS: Yes, there is.

FLATOW: This time and it's - and it talks about how when you just - when you think you know everything, there's always that other rock, something under the rock, that's when you turn it over. It surprises you.

Dr. MCCOMAS: Absolutely.

FLATOW: And the IBEX will be launched in October.

Dr. MCCOMAS: In October.

FLATOW: And when does it go into orbit and start working?

Dr. MCCOMAS: Takes us about five weeks to get it up into its final orbit and get the instruments turned on. And then it takes six months to make the first all-sky image, because we actually use the motion of the earth around the sun to make the measurements in all the different directions. We've actually put a little video up on your Science Friday website if people are interested in the IBEX mission, that they can see how we form the images and that sort of thing.

FLATOW: Yeah. Go to sciencefriday.com and that's our second video, sort of "Pick of the Week" this week. And you'll be making a three-dimensional image or getting three...

Dr. MCCOMAS: Right.

FLATOW: Wow.

Dr. MCCOMAS: Right. We'll be making an image from the inside looking out, covering all - you know, all directions in the sky. So, it'll be a complete sky coverage.

FLATOW: Will we be able to look at that image ourselves, and moving around, you know, like a virtual reality image.

Dr. MCCOMAS: I - we haven't gotten there yet, but...

(Soundbite of laughter)

Dr. MCCOMAS: I wouldn't be surprised.

FLATOW: We'd be happy to put that on our site.

(Soundbite of laughter)

Dr. MCCOMAS: Well, invite me back when we have the first all-sky image, and we'll see...

FLATOW: All right.

Dr. MCCOMAS: If we can do that.

FLATOW: All right, Dr. McComas, consider that an invitation.

Dr. MCCOMAS: OK.

FLATOW: Good luck to you. Good luck on your launch in October.

Dr. MCCOMAS: Thanks so much, Ira.

FLATOW: David McComas is principal investigator for the Ulysses Solar Wind Observations Over the Poles of the Sun Experiment, SWOOPS to you, a lot easier to say. He's also senior executive director of the Space Science and Engineering Division at Southwest Research Institute in San Diego - in San Antonio. San Anton, one of our favorite cities, Texas. That's about all the time we have for today.

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