Thursday, November 11, 2010

Space Weather - Impact on Life on Earth

The other day we discussed what Space Weather is. It was very basic just to give you an idea of how it comes about. Now let's see if there is an impact of Space Weather down here on Earth. It's not like you need a special Space Weather umbrella to protect you from it - or a tin foil hat. Even though it would be great to see this on a daily basis, don't you think?

We have already established that Space Weather has an impact on not only life (or technology) in Space, but also down here on Earth. Let's take a closer look at how a Space Weather event can impact us here on Earth.

First, let's review how Space Weather impacts Earth on a global scale. Here is a short movie showing you a CME (Coronal Mass Ejection) from the Sun, traveling through Space and interacting with Earth's magnetosphere.

The most beautiful impact all of this has are the awe-inspiring Aurora Borealis and Aurora Australis -- the Northern and Southern lights.To witness these lights is a treat and I could spend hours looking at images and videos of those events. Let's take a closer look at why we see these amazing shapes in the Northern or Southern skies.

Near the poles of Earth, observers have often seen glowing clouds shaped like curtains, tapestries, snakes, or even spectacular radiating beams. Northern Hemisphere observers call them the Northern Lights of Aurora Borealis. Southern Hemisphere observers call them the Southern Lights or Aurora Australis. Because most people, and land masses, are found north of the equator, we have a longer record of observing them in northern regions such as Alaska ,Canada, Scandinavia, but sometimes as far south as the Mediterranian Sea or Mexico! 

Earth is surrounded by a magnetic field. Sprinkle iron filings on a paper and put a magnet underneath. You will see lines of magnetism that seem to 'flow' towards the poles of the magnet. If you were a charged particle in space, you would be magnetically trapped on one of these lines of magnetism. As you flow down Earth's magnetic field into the north and south poles, you collide with atoms of oxygen and nitrogen. This gives off the colored lights you see in an aurora. What do you think these ovals of light look like from the ground if you were looking up at the sky? From space we can look down at an aurora and see that it actually looks like a crown of light! Scientists call this the Auroral Oval as you can see in the picture below. If you were standing on the ground looking up at the night sky, you would only see a very small part of this halo. It would look like beautiful draperies and curtains of shimmering light that change shape from minute to minute!

On May 29, looking southward from a vantage point about 350 kilometers above the southern Indian Ocean, astronauts onboard the International Space Station watched this enormous, green ribbon shimmering below. Known as aurora australis or southern lights, the shifting, luminous bands are commonly seen at high northern latitudes as well, there known as the aurora borealis or northern lights. North or south their cause is the same though, as energetic charged particles from the magnetosphere pile into the atmosphere near the Earth's poles. To produce the characteristic greenish glow, the energetic particles excite oxygen atoms at altitudes of 100 kilometers or more. Aurora on May 29 were likely triggered by the interaction of the magnetosphere with a coronal mass ejection erupting from the Sun on May 24.

And we are not all that special here on Earth! We have been able to observe Auroras on other planets, like Saturn. What drives auroras on Saturn? To help find out, scientists have sorted through hundreds of infrared images of Saturn taken by the Cassini spacecraft for other purposes, trying to find enough aurora images to correlate changes and make movies. Once made, some movies clearly show that Saturnian auroras can change not only with the angle of the Sun, but also as the planet rotates. Furthermore, some auroral changes appear related to waves in Saturn's magnetosphere likely caused by Saturn's moons. A false-colored image taken in 2007 shows Saturn in three bands of infrared light. The rings reflect relatively blue sunlight, while the planet itself glows in comparatively low energy red. A band of southern aurora in visible in green. Inspection of many more Saturnian images may well lead to an even better understanding of both Saturn's and Earth's auroras.

But let's enjoy some more aurora pictures from right down here! Next time I will talk a little more on how Space Weather impacts us living creatures.

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