Aurora Borealis By: Dominique
What are the northern lights? A phenomenon occurring near the polar regions that appears as wisps and luminous arches of light
Where can you see them? Earth’s magnetism draws solar wind towards the poles which is why the aurora occurs much more frequently near polar regions Scandinavia, Canada, northern North America, southern South America, Northern Europe, Siberia
Altitude Most aurora borealis displays occur between 90 and 130 km The lower edge is generally around 95 to 110km, about 10 times higher than a jet flies Sometimes high-altitude aurora can be seen at the level where space shuttles fly
Unique Sightings The northern lights have been seen south of 35 degrees North in the United States November 5th and 6th 2003, aurora borealis displays were seen in Texas, Arizona, and San Diego Unique southern sightings are the product of huge geomagnetic storms
What is the cause of the aurora borealis? The aurora borealis is caused by solar wind (the sun’s stream of plasma) Solar wind travels from the sun and enters Earth’s atmosphere and becomes agitated Some of the excited ions interact with the ionosphere and start glowing The excited ions absorb extra energy when colliding with Earth’s atmosphere, causing them to send out light photons
The colors we see as the aurora borealis are really the energy of photons • It takes a green photon about ¾ of a second to return to ground state and emit the color, while a red photon takes about 2 minutes to return to ground state and show its color. • If atoms collide with another air particle before reaching ground state they could transfer their energy to the other particle and never emit the light photon. • Differences in time that it takes to return to ground state determines where the color will show up. • In denser air (lower down) the red photon doesn’t have a chance, collisions are frequent and 2 minutes leaves a lot of time for a collision to occur. Why and how does colored light occur?
Colored Light Cont. • Green emissions do have a chance of occurring lower down because they return to ground state quickly. • Below about 100km (60 miles) altitude even the green emission doesn’t have a chance, collisions are simply too frequent in the dense air. • The green emission is squished by collisions at that altitude all that is left is a blue-red mixture of molecular nitrogen and that’s why a purple color is the lower border.
Colors Red is the dominant color Commonly seen colors are: red, green, violet, and blue The color depends on the gas that the plasma ions interact with Atomic nitrogen causes red and blue Atomic oxygen causes a dark red and green combination Molecular nitrogen results in purple
What exactly does aurora borealis mean? ‘aurora borealis’ is Latin: -aurora means ‘red dawn’ -borealis means ‘northern’ Galileo Galilei named the northern lights Aurora was the Roman goddess of dawn and Boreas was the Greek name for the North Wind
Effects on Communication Depending on the size of the solar flare, communications can be disrupted Radio, television, and satellite communications and some Ham radio frequencies can be disturbed
Effects on the Atmosphere The aurora borealis only affects the atmosphere at or above it Our weather is not affected at all because the aurora doesn’t interact with the troposphere At 100-200km altitude the energetic ions cause heating and create currents The currents cause horizontal wind and temperature changes Photographed from the ISS
Classification of Solar Events Different sized flares create different sized auroras C-class event- small solar flare with no effect on communication M-class event- medium sized solar flare that can disrupt communication X-class event- large or extreme solar flare that disrupts communication
Sources • Works Cited • “Aurora Borealis.” Aurora Borealis. N.p., n.d. Web. 1 June 2010. <http://www.aurora-borealis.us/>. • “Aurora Borealis (Northern Lights).” National Weather Service Forecast Office. N.p., 6 Jan. 2006. Web. 1 June 2010. <http://www.crh.noaa.gov/fsd/astro/aurora.php>. • “Facts.” Northern Lights And Winter Nights. Frontiers North Adventures Incorporated, n.d. Web. 1 June 2010. <http://www.northernlightswinternights.com/facts/>. • “Facts And Info About Aurora Borealis.” Facts About. N.p., n.d. Web. 1 June 2010. <http://www.facts-about.org.uk/science-aurora-borealis.htm>. • Lummerzhein, Dirk. “Frequently Asked Questions About the Aurora and Answers.” Geophysical Instistute . N.p., 12 May 2009. Web. 1 June 2010. <http://odin.gi.alaska.edu/FAQ/>. • The images are from: Google Image Search