Aurora One of the Wonders of the World
What is Aurora? • Auroras, also known as Northern And Southern (Polar) Lights are natural light displays in the sky, usually observed at night, particularly in the Polar Regions. • Aurora occurs deeper inside the Polar Regions, but these are rarely occurrences, and these are often invisible to the naked eye.
Aurora in Atomic Physics • What exactly happens? • Physicists say that the aurora is just a large-scale electrical discharge phenomenon in the high-altitude atmosphere, resulting from quantum leaps in oxygen and nitrogen atoms. • The color, shape, and intensity depend on the energy of the electrons shooting downward into the upper atmosphere. Aurora during a geomagnetic storm that was most likely caused by a CME from the Sun on May 24, 2010.
Colors of Aurora • Oxygen emissions: Green or brownish-red, depending on the amount of energy absorbed. • Nitrogen emissions: Blue or red. Blue if the atom regains an electron after it has been ionized. Red if returning to ground state from an excited state. Green is the most common of all auroras.
Historical Overview • • The Eskimos of the lower Yukon River believed that the aurora was the dance of animal spirits (deer, seals and salmon). In central Europe the Northern Lights were considered a bad omen. They warned of illness, plague and death. When red, they signaled the outbreak of war. Image of a colored woodcut by Wolf Drechsel, showing an auroral display over the German town of Nuremberg on October 5, 1591.
What is the best place to see Aurora? • The best places are high northern latitudes during the winter, Alaska, Canada, and Scandinavia. • Places like Fairbanks, Alaska, Dawson City, Yukon, Yellowknife, the southern tip of Greenland, Reykjavik, Iceland, Norway, and the northern coast of Siberia have a good chance to have the aurora overhead. • On the southern hemisphere the aurora has to be fairly active before it can be seen from places other than Antarctica. • Hobart, Tasmania, and the southern tip of New Zealand have about the same chance of seeing aurora as Vancouver, BC, South Dakota, Michigan, Scotland, or St. Petersburg.
Aurora on other planets • Almost all planets in the solar system have aurora of some sort. • If a planet has an atmosphere and is bombarded by energetic particles, it will have an aurora. • Planets like Venus, which has no magnetic field, have very irregular aurora, while planets like Earth, Jupiter, or Saturn, which have an intrinsic magnetic dipole field, have aurora in the shape of oval shaped crowns of light on both hemispheres. Saturn Jupiter
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