Atmosphere And Weather

Auroras Explained

Robert Bullard's image for:
"Auroras Explained"
Image by: 

Auroras have intrigued and fascinated humans for thousands of years. But although they seem mysterious, the workings of these phenomena are quite simple.

The star that holds our solar system together is quite dynamic. As it blasts out its radiation, the streams of hot plasma become the basic energy source for all auroras (not just on our own planet).

Edmond Halley was reportedly the first person to link auroral activity to the Earth's magnetic field, and he was right. Earth's powerful magnetic fields draw these particles to our poles creating these mighty spectacles. When viewed from above, they appear as wobbly ovals around the magnetic poles. In times of high solar activity however, the ovals can expand further toward the equator.

As the solar wind bombards our ionosphere, the atoms and molecules (mostly nitrogen and oxygen) become energized. Upon returning to their natural state, photons are released - resulting in visible light. These colors can range from red to orange, pink to yellow, and blue to violet. This awesome interaction is much like a neon light, whose differing colors (when excited) are based on whatever particular gas is enclosed within the light tube. In much the same way, auroras display their colors. Red usually appears at the top of the aurora. This is due to the fact that there is mostly atomic oxygen that high up. Lower down in the atmosphere, you tend to have more molecular nitrogen, which emits blue and red (and variations such as purple). Even further down in altitude, molecular oxygen causes a greenish glow.

Auroras are in constant motion due to the ever-changing interaction of the solar wind and the Earth's magnetic field. They generally will appear as luminous sheets of light (or "curtains"), as halos, or even pillars. They will stand still one second, and then dance across the sky the next.

The best time to see an aurora is in the winter months (although it's a little warmer in the north). The intensity of the event can be affected by solar flares, sunspots, geomagnetic storms (which can occur during the equinoxes), and the tilt of Earth's axis.

Besides the obvious difference in location, there really isn't that much distinction between our two auroras. The best place to view the Northern Lights is from either Greenland, the Scandinavian coast, Siberia or Alaska. The best place to view the "Southern Lights" of course is Antarctica.

We get the name Aurora Borealis by joining the name of the Roman goddess of dawn "Aurora" with the Greek god of the north wind - "Boreas". Likewise, add the name "Aurora" to the Latin word for "of the south" - "Australis", and you get the southern counterpart.

Although very beautiful, the Northern and Southern Lights are very important in the field of scientific research as well. Whether from remote outposts on the frozen tundra, or in lonely orbit, research is ongoing. In fact, scientists have devoted their entire careers to understanding this phenomenon. Decades of work (along with millions of dollars) have produced valuable (although incomplete) data of the magnetic properties of our planet - as well as others.

Satellites such as the SOHO and Yohkoh satellites allow us to target coronal holes (which affect aurora) and follow their movements. In early 2007, a series of five identical probes (named THEMIS) were launched to learn more about aurora. They were able (for the first time) to determine a correlation between magnetic events and auroral intensification. The European Space Agency also launched their Cluster satellites, which have given us some insight into the two different known types of electrical currents associated with the auroras. We even have TED (Total Energy Detector), which detects changes in aurorally charged particles. It's obvious to see that with these resources invested, there is good science to be learned.

Earth is not the only planet where auroras occur. In fact, if a planet has a dense enough atmosphere, it most likely has some sort of aurora. Planets such as Jupiter and Saturn have quite impressive ones, while Uranus and Neptune (which have misaligned magnetic fields) have distorted ovals. This beautiful phenomenon can even extend to moons as well. The Galilean moon Io, for example, has an active atmosphere, as well as an aurora.

The more we learn about phenomenon such as auroras, the more we can understand the interaction between our world, and the solar system it's connected to.

More about this author: Robert Bullard

From Around the Web