Podcaster: Carolyn Collins Petersen
Description: What are scientists learning as they study the effects the Sun has on our planet?
Bio: Carolyn Collins Petersen is a science writer and show producer for Loch Ness Productions, a company that creates astronomy documentaries and other materials. She works with planetariums, science centers, and observatories on products that explain astronomy and space science to the public. Her most recent projects were the Griffith Observatory astronomy exhibits in Los Angeles and the California’s Altered State climate change exhibits for San Francisco’s California Academy of Sciences. She has co-authored several astronomy books, written many astronomy articles, and is currently working on a new documentary show for fulldome theaters and a vodcast series for MIT’s Haystack Observatory.
Today’s Sponsor: This episode of 365 Days of Astronomy is sponsored by Loch Ness Productions, a unique multimedia production company specializing in cosmically creative content and space music for planetarium and fulldome theaters worldwide. Loch Ness Productions also works with exhibit designers, observatories, science institutions and publishers to bring a love of astronomy, Earth science, and space science to audiences everywhere. On the web at www.LochNessProductions.com
Hi, I’m Carolyn Collins Petersen – TheSpacewriter.
CAROLYN: What does it mean to live near a star like the Sun? For all of us here on Earth, it means a steady supply of heat and light to power our planet’s environment. But, it also means that we live with space weather caused by the Sun’s activity.
At MIT’s Haystack Observatory near Boston, Massachusetts, atmospheric scientists use radar antennas and GPS signals to study the effects of solar activity here at Earth. Dr. Philip Erickson and Dr. Anthea Coster are part of Haystack’s team of space weather researchers. I recently talked with them about what happens to Earth when the Sun stirs up a little space weather.
So Phil, walk us through the mechanics of a space weather event.
Phil Erickson: Well, it all starts with the fact that we are living with a star. And, the Sun is an active star. There’s a particularly well-known cycle called the solar cycle, which happens every 11 years – we’ve been quiet for the last three or four years and then it gets very active for a couple of years and then goes back and forth.
The Sun’s outer atmosphere is hot enough that it is continually boiling away its content, and that material we call the solar wind. That wind is not constant. It has very large outbursts, and those outbursts are often timed with the appearance of variability in the Sun’s surface and also in the Sun’s output.
When you get one of these bursts, we get space weather in the space between the planets and the Sun, and in fact, that affects the planets. That material can occur in something called a coronal mass ejection, which is kind of what it sounds – that’s the corona or the outer atmosphere of the Sun suddenly emitting a lot of material. That’s kind of a very large burst of solar wind in our face, if you want to think of it that way.
CAROLYN: So, why do we only see space weather at certain times?
PHIL: If it happens to be aimed just right, so that it’s coming straight at us on the Earth, we can end up getting something called a space weather “event.” That solar wind burst, when it arrives at Earth, starts interacting with our upper atmosphere.
Earth’s magnetic field actually extends out into space and the solar wind is formed of charged particles. For the charged particles, the magnetic field acts like an obstacle. The analogy is thinking of a rock in a river. Water flowing down toward the rock then has to move around the rock.
The solar wind burst, when it comes by Earth has to flow around the Earth, but when it does that, it’s pushing on the magnetic field that surrounds the Earth. And so the ionosphere – the charged part of the upper atmosphere – really cares whether the coupled Sun-Earth system has disturbances in it, and it will react to those. And so, there are a number of us who, in fact, study the physics of what happens to the upper atmosphere when we have one of these space weather events come by.
Here, for example, at Haystack Observatory, we have a very large, ground-based radar, which essentially uses a powerful transmitter and a very large antenna, and we use radio waves as a remote sensing tool to find out what the conditions are in the upper atmosphere without having actually to be up there. We send this very powerful radio wave up from the surface of the Earth. When it goes by a particular “box” of charged particles in the upper atmosphere, those charged particles absorb a tiny amount of the radio energy in that wave we sent, and in fact, they re-radiate a very, very, very tiny signal.
We can end up using that signal to determine similar things that a weather radar would do on the ground, except for here we’re looking at the “weather” in the upper atmosphere. We can tell density. We can tell temperature. We can tell the winds – which direction are things blowing – are they blowing away or toward us, left or right.
And so, we’ve been making measurements here for more than 40 years that are designed to look at the properties of the upper atmosphere here in the Boston, Massachusetts area, and then attempt to look at what we see, especially when we get a space weather disturbance and to see if we can understand what we’ve measured in terms of the physics of the ionosphere itself.
CAROLYN: Who else is studying space weather?
PHIL: We are one of the radars that do this. There are five radars that the United States supports through the National Science Foundation that are strung all the way from Greenland to the equator, there’s another one in Alaska that’s just been built, and there’s another one coming online in Resolute Bay, which is in cooperation with the Canadian government. In total, there are about ten of these radars. They are by far the most powerful ground-based technique for measuring the ionosphere.
But, what we’re looking for are essentially these space weather effects and we’re looking at how those effects occur when we see a space weather event lift off the surface of the Sun.
CAROLYN: It sounds like space weather goes way beyond auroral displays, doesn’t it?
PHIL: Absolutely! Auroral displays are kind of the earliest human indication that something might be happening in the upper atmosphere. But, now that we have a lot of technology that relies on radio waves and relies on other forms of communications, all of these are susceptible to space weather events, and so understanding how the events occur and what their strengths are is very important in order to be able to predict how those systems will fare in the future and how reliable they’ll be.
CAROLYN: Dr. Anthea Coster is an expert on what space weather can do to those technologies that we depend on every day
Anthea, last year you took part in a symposium about space weather and how it can affect such things as signals from global positioning satellites. So, how does GPS work?
ANTHEA COSTER: How GPS gets position and time is that basically there are extremely accurate clocks that are in the GPS satellites. And, they are sending out signals which give their time information and position information.
And, those signals have to travel through the atmosphere and through the ionosphere, and if your receiver can get signals from at least four satellites, you can calculate not only your position, but also your time.
CAROLYN: How does space weather affect that?
ANTHEA: The reason space weather is important is this propagation aspect because it uses radio waves to propagate through the atmosphere and the atmosphere can cause distortion.
CAROLYN: How does that work?
ANTHEA: I like to think about how if you shine a white light on a prism, the light will kind of separate into different colors. Well, the ionosphere does that with radio waves, but it also slows the wave down so it’s not traveling at the speed of light, it’s traveling a little bit slower.
In addition, it can distort your signal, and either you have to correct that, or if it gets bad enough, you lose the signal.
CAROLYN: And how does that affect the GPS and the technology we use every day?
ANTHEA: It depends a little bit on how large the space weather event is. If we really had a HUGE event, it could actually disrupt anything you’re trying to receive with the GPS system. But, probably that won’t happen.
CAROLYN: So, what would happen?
ANTHEA: Depending on each individual receiver, your position won’t be as accurate. Now, for most purposes, in general you’ll be fine. But, if you needed really high accuracy, somebody who’s doing navigation on our coastal waterways, if you’re navigating a barge, you really need to know your horizontal position very well. Or somebody trying to land a plane, or navigating a train – all of these are areas where you really, really need high precision. So, if you’re not prepared that you could have these huge changes, very rapidly, it could cause you to make a mistake. And, in some of these cases,it could be a very serious mistake.
Remember GPS is embedded in all of our timing devices, all over. And, we don’t even think about it, but when you use your cellphone, some of that signal is using the time information that they’re getting from GPS. So, those could be impacted by very large space weather events.
CAROLYN: So, what can we do to predict these events?
ANTHEA: We are beginning to get enough understanding that, if we know a space weather storm is coming, we can kind of predict what’s going to happen and when it would happen. But, we need more science or research to kind of understand those processes better.
If you were relying on it and you knew there was going to be some kind of error, if somebody sent you out an alert, you would know “Okay, at this point in time, I may not be able to use my GPS.”
And actually, the FAA has done that for airplanes with their WAAS system. They’re monitoring this. They’re aware of these problems. If there’s one of these large storms, they tell all of the pilots, “Do not use your WAAS system at this time to land your plane.”
CAROLYN: Phil and Anthea, thank you both for giving us an up-to-date peek at space weather and its effects on us and our technology.
If you’d like to learn more about space weather surf on over to www.thespacewriter.com/wp and click on the 365 Days of Astronomy tab. You’ll find more space weather information and Web page links.
Thanks for listening!
End of podcast:
365 Days of Astronomy
The 365 Days of Astronomy Podcast is produced by the New Media Working Group of the International Year of Astronomy 2009. Audio post-production by Preston Gibson. Bandwidth donated by libsyn.com and wizzard media. Web design by Clockwork Active Media Systems. You may reproduce and distribute this audio for non-commercial purposes. Please consider supporting the podcast with a few dollars (or Euros!). Visit us on the web at 365DaysOfAstronomy.org or email us at info@365DaysOfAstronomy.org. Until tomorrow…goodbye.