Aurora Borealis By: Ariel Gooch Elementary Astronomy Spring 2011

Introduction An aurora (plural: auroras or aurorae) usually observed at night, is a natural light display in the sky, particularly in the polar regions, caused by the collision of charged particles directed by the Earth's magnetic field.

History of Naming Named after the Roman Goddess of dawn, Aurora, and the Greek name for the north wind, Boreas, by Pierre Gassendi in 1621 Aurora Boreas

Where else can you see aurora borealis? spotted throughout the world most visible closer to the poles due to the longer periods of darkness and the magnetic field Northern lights over Moskosel, Lapland, Sweden

Auroral Mechanism Results from emissions of photons in the Earth’s upper atmosphere oxygen and nitrogen atoms returning from an excited state to a ground state

Auroral Mechanism Oxygen emissions - green or brownish-red Nitrogen emissions - blue or red

Auroras Curtain Like Shape Electrons are not free to move in just any direction Magnetic fields impede motion of charged particles when they try to cross the magnetic field Electrons stay on or near this field line even when it makes a collision Example of electron movement

Frequency of Occurrence Geomagnetic storms ignite auroras more often during the months around the equinoxes (spring and fall) Greatest during October and April

Best Place to See an Aurora High northern latitudes, Alaska, Canada, and Scandinavia You need a clear and dark sky

Aurora Events of Historical Significance “Great geomagnetic storm” occurred on both August 28th and September 2nd,1859 Thought to be the most spectacular aurora in recent recorded history During the most intensive phases of the storm the oscillations were so rapid that only few observations could be made

Auroras on Other Planets If a planet has an atmosphere and is bombarded by energetic particles, it will have an aurora Venus has no atmosphere, irregular aurora Uranus and Neptune, magnetic field of both planets is not aligned with the rotational axis, getting a very distorted auroral oval

Auroras on Other Planets Aurora on Saturn Aurora on Jupiter

Can You Hear the Aurora? The upper atmosphere is too thin to carry sound waves, and the aurora is so far away that it would take a sound wave 5 minutes to travel from an overhead aurora to the ground

Can an Aurora be predicted? Yes, but with less confidence than weather prediction When the solar wind is very strong and perturbed, we have a chance of intense aurora

Conclusion The Aurora Borealis is quite an incredible and beautiful sight, that I recommend one travels to witness Unfortunately, we have been at a minimum aurora activity since 2007

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