Saturday, January 21, 2012

What Are the Northern Lights?

The Northern LIghts: enchanting yet mysterious.

The Northern Lights: virtually everyone has heard of them and probably almost everyone who has seen pictures and/or video has been enchanted by them, but very people know what they are. So, what exactly are the Northern Lights, also known as aurora?

The aurora are caused by an interaction of energized particles from the Sun interacting with the Earth's magnetic field. When the Sun is active, it is more likely to emit a burst of charged atoms into space in a n event called a coronal mass ejection (CME). In technical terms, CMEs differ from the solar wind in that the CMEs are stronger. Think of it this way, if the solar wind is a breeze, a CME is a wind storm. Once launched into space, it will take between 2 and 3 days for the particles from the Sun to reach Earth.

Upon hitting Earth's upper atmosphere, the charged particles are funneled toward the polar regions thanks to the Earth's magnetic field, where they ten interact with atoms high in the Earth's atmosphere. When charged ions from the Sun hit atoms, they give off a distinct glow that varies by atom and also altitude.

As for colors, here are what they mean:
Deep red: caused by high-altitude (175+ miles up) oxygen
Green/greenish yellow: lower altitude oxygen
Pale red/pink: low nitrogen
Blue/purple: high-altitude hydrogen and helium

The most common color is a greenish shade, with ruby red aurora being the most rare.. Aurora can be as low as 60 miles and as high as 350.

When it comes to form, the aurora can take on many guises, which can resemble silk curtains, a cricking whip, or an amorphous glob. As for why the aurora look the way to do, it all has to do with how they hit the lines of Earth's magnetic field. The closer to a line, the more curtain/whip-like they will be.

When it comes to seeing aurora, for reasons that are still not completely understood, the best seasons to watch are the spring and fall, though they can occur at any time of the year because their origin lies with the Sun. As for frequency, aurora re more commonly seem when the Sun is at or near maximum in its 11-year cycle. For the record, the next solar maximum is forecast for 2013/14.

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