Northern Lights

QUESTION:

Is there any way to predict when we can see good Northern Lights?

ANSWER:

Predictions are good for a few hours or one day at best.  Predictions are based on satellite observations of sunspots and solar flares. The Geophysical Institute at the University of Alaska, Fairbanks, issues aurora forecasts. Magnetometers and particle detectors in satellites can tell if a “space weather storm” is approaching in a few hours.

The Northern Lights, scientific name is Aurora Borealis, have their origin in the Sun. Solar activity causes a huge ejection of particles. These ions and atoms take 2 or 3 days to get to the Earth, where they get caught in the Earth’s magnetic field.  The flow of charged particles is termed the solar wind. These charged particles flow along the lines of the magnetic field in both polar regions of the Earth. The collisions with oxygen and nitrogen atoms produce the dazzling light displays.

The vivid colors produced by the Northern Lights is very much akin to the colors formed in those neon type advertising signs we see in bars, barbershops, and stores.

The physics is the same. Atoms are energized. Electrons going around the nucleus are made to go to orbits further away from the nucleus. When the electrons go back to their normal orbit, the atom gives up its energy by emitting a little bit of visible light.

Collisions with oxygen yields green, the most common of all the aurora colors. Nitrogen gives red colors. The next most prominent color is a mixture of light green and red, pure red, then yellow, a mixture of red and green. Then lastly there is pure blue.

The best time to observe northern lights is from 9:00 PM to 1:00 AM and best months are March, April, August, and September. The closer an observer is to the pole regions, the better the view. People living in Alaska and Greenland find the Northern Lights are visible most nights of the year.

The earliest accounts of the Aurora Borealis date back to 600 BC and appear on Babylonian clay tablets. The most spectacular display in modern times was on September 2, 1859, and seen over the entire Earth and was recorded in ship’s logs.  The New York and Boston newspapers reported at the time that the Northern Lights were so brilliant that newspapers could be read at one o’clock in the morning.

Our good planet Earth has an atmosphere and magnetic field to protect us from those particles emanating from the sun. The moon has neither an atmosphere nor a magnetic field. Astronauts working on the surface of the moon would be in grave danger when a big solar flare occurs.

Astronauts  in the International Space Station are sometimes alerted to violent solar activity. In December, 2006 a huge flare made the astronauts move to a more protected module inside the ISS. The Northern lights can damage the electrical power grid on Earth and satellites in space.

Magnetic activity on the sun follows an eleven year cycle.  The period of low activity is ended and an upturn in solar flares and sunspot activity is beginning. Experts say we should expect more “colored lights in the sky” this April and again in August of  2012. Look for nature to produce a most exquisite light show.

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