Aurora borealis/australis

Certain familiar astronomical phenomena are related to the magnetosphere. For example, particles excited by the interaction between the solar wind and the magnetosphere may eventually collide with and ionize particles in the upper atmosphere. When these ionized particles return to their ground state, they give off energy that may appear in the form of auroras (aurora borealis or aurora australis). 

People travel thousands of miles to see the aurora borealis (the northern lights) and the aurora australis (the southern lights). Once incorrectly believed to be reflections from the polar ice fields, the auroras occur 100 to 1000 km above Earth. 

The incoming streams of solar protons and electrons are oriented by Earth s magnetic field so that most auroral displays occur in doughnut-shaped zones about 2000 km in diameter centered on the North and South Poles. Aurora borealis is the name given to this phenomenon in the Northern Hemisphere. In the Southern Hemisphere, it is called aurora australis. Sometimes, the number of solar particles is so immense that auroras are also visible from other locations on Earth. 

What process gives rise to aurora borealis and aurora australis ... 

Molecules in the upper atmosphere are constantly being bombarded by high-eneigy particles from the sun. As a result, these molecules either break up into atoms and/or become ionized. Eventually, the electronically excited species return to the ground state with the emission of light, giving rise to the phenomenon called aurora borealis (in the Northern Hemisphere) or aurora australis (in the Southern Hemisphere). 

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