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Super job you guys. So, what is NASA doing to study the auroras?

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Well, Nikki Fox, a senior scientist at the John Hopkins University Applied Physics Laboratory in Baltimore, Maryland, can tell us all about it.

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Why do scientists use satellite images to monitor the auroras?

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In analyzing the graph, when do auroral activities increase?

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What are the phases of the aurora?

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This is the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland.

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I am the operations scientist for the Polar Mission.

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The Polar Mission is part of NASA's Sun-Earth Connections fleet.

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Within the Sun-Earth Connections fleet, Polar has the responsibility for multi-wavelength imaging of the aurora,

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measuring the entry of the material into the polar regions, the flow of material to and from the ionosphere,

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and the discharge of the energy in the ionosphere and the upper atmosphere.

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Scientists use satellite images to monitor the position of the various auroral features.

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In particular, the latitudinal location of the edge closest to the equator of the aurora determines the amount of activity.

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The further the aurora moves towards the equator, the bigger the event.

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Also, the extent and speed of the expansion of the aurora tells us a lot about the amount of activity.

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The further and faster it moves, the larger the event.

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Polar is a unique spacecraft because it carries four different cameras to study the aurora.

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There is a high-resolution visible imager, which allows us to look at the aurora in different wavelengths or colors.

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In this way, we can simultaneously image the red, blue, and green components of the aurora.

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There is also a global imager, which allows us to look at the whole Earth at once.

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This camera takes pictures in ultraviolet, so we can see what the aurora is doing even when there is sunlight in the way.

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Auroras do occur during the daytime, we just can't see them with the naked eye.

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But from the images of this camera, we can see the size of the auroral oval.

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For example, the following graph shows you the latitudinal auroral extent for selected coronal mass ejection events.

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Coronal mass ejections, or CMEs, are gigantic explosions caused by the Sun that can reach speeds of millions of kilometers per hour.

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It takes around three days for a CME to reach the Earth.

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The vertical axis of the graph is the geomagnetic north latitude from 40° to 58°.

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On a globe, 40° north latitude is closer to the equator, and 58° north latitude is closer to the geomagnetic north pole.

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The horizontal axis represents the dates of selected CME events.

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From analysis of this graph, we can determine that the latitudinal auroral extent generally increased from 1997 to 2000.

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Be careful in the way you interpret this graph, the function appears to be decreasing.

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Even though the data show a downward trend, the auroral oval extended closer to the equator.

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For this particular graph, it tells us that the auroral activity increased.

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Let's look at two data points.

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From the data on January 10, 1997, there was an auroral event in the northern hemisphere that extended to a latitude of 57.3°.

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Do you know the name of the country that the auroral oval covered?

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If you said Canada, then you are correct.

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On July 15, 2000, there was an auroral event that extended to latitude 41.2°.

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The auroral activity was so intense that the auroral oval stretched into the southern parts of the United States.

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The 11-year solar cycle of the Sun reached its maximum in the year 2000, so we expected auroral activity to increase from 1997 to 2000.

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With all these cameras and the data we collect, we can photograph the evolution of an aurora.

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The evolution of every aurora tends to follow a similar sequence.

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We call this an auroral substorm.

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The following images show a typical sequence of an auroral substorm.

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The first image shows a quiet oval before any activity begins.

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This is called the quiet phase.

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Right before we see any bright emissions, we can observe the oval getting bigger and moves further towards the equator.

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This is called the growth phase.

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The activity truly begins with a small spot of light, or onset event, followed by the lighting up of the whole ring and an expansion to a more poleward location.

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The large bright region you can see is called the auroral bulge.

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When the aurora reaches its maximum expansion, you can see that the large bulge begins to break up and the small discrete features appear.

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Finally, the whole aurora dims and recovers.

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It will eventually return to the initial state, the quiet phase.

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The whole process may repeat over and over again until the activity dies out completely.

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Now, all the images you've seen so far have been from the northern hemisphere of the Northern Lights, or the aurora borealis.

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But did you know that there was also a southern counterpart of the aurora called the Southern Lights, or the aurora australis?

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And here we're seeing a unique movie taken by the polar spacecraft that shows us both the north and the south at the same time.

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This allows us to see that the activity is occurring at the same time in both hemispheres.

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We call this the conjugate aurora.

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Now, we've seen data from many different cameras on the polar spacecraft and learned that when you add them all together, you can learn an awful lot more about the aurora.

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Now we're looking at an animation which shows the polar auroral image underneath with the timed spacecraft flying over the top.

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Timed is taking images in very high resolution and you can see that every time the spacecraft flies through the oval,

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it suddenly illuminates all the fine scale features that you couldn't see before.

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So now we know that when you add two data sets together, you get even more information.

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Now with the addition of data from ground-based observatories and sounding rockets, we can look at the aurora with full perspective.

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Okay, now it's time for a cue card review.

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Why do scientists use satellite images to monitor the auroras?

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In analyzing the graph, when do auroral activities increase?

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What are the phases of the aurora?