Saturday, February 11, 2006
What are northern lights?
Northern lights is the name of a light phenomena often seen in the northern regions.
What causes them?
Northern lights originate from our sun. During large explosions and flares, huge quantities of solar particles are thrown out of the sun and into deep space. These plasma clouds travel through space with speeds varying from 300 to 1000 kilometers per second.
But even with such speeds (over a million kilometer per hour), it takes these plasma clouds two to three days to reach our planet. When they are closing in on Earth, they are captured by Earth's magnetic field (the magnetosphere) and guided towards Earth's two magnetic poles; the geomagnetic south pole and the geomagnetic north pole.
On their way down towards the geomagnetic poles, the solar particles are stopped by Earth's atmosphere, which acts as an effective shield against these deadly particles.
When the solar particles are stopped by the atmosphere, they collide with the atmospheric gases present, and the collision energy between the solar particle and the gas molecule is emitted as a photon - a light particle. And when you have many such collisions, you have an aurora - lights that may seem to move across the sky.
In order for an observer to actually see the aurora with the naked eye, about a 100 million photons are required.
How to observe the aurora
Chasing the aurora is difficult, since the phenomenon seems to have a mind of its own, hiding from observers who wait for weeks, only to reveal itself in a spectacular display the day after they leave.
A lot of the questions we receive in the Q & A section go like this: "I live here/or will travel to that or that place in 2 to 10 months time. When or will I be able to observe the lights?" Those are just about the hardest questions to answer, because we simply do not know for sure. No one does, not until a few hours before the actual display. But there are some things we can do to improve our chances of observing a wonderful auroral display.
Northern parts of the Nordic countries, including all of Greenland and Svalbard.
Northern parts of Alaska, USA.
Northern and middle parts of Canada.
Northern parts of Russia.
Even though there are aurora all day, all year round on Earth, and even if you are directly below the oval, you need to observe at the right time. Why? Because of the sun.
The aurora is light, and compared with sunlight it is weak. In the north, where 90 % of the displays occur, something happens every summer that very few people living further south actually realize: the sun never sets. It never drops below the horizon, effectively outshining any light from the aurora, no matter how strong it is.
That is why we have the aurora "season", a period where the sun doesn't outshine the aurora, and it goes from late September/early October to late March. And for some reason not known to scientists yet, the aurora is far more active in late autumn and early spring.
baaah. im dazzled. again-
`h0neystars
___nothatcomplicated*
Saturday, February 11, 2006
