Why do auroras occur

Sam Franzen Why do the northern and southern lights only appear near the poles? Marian Mateling. Norwegian scientist Kristian Birkeland proposed that electrons emitted from sunspots produced the atmospheric lights after striking the Earth's magnetic field. The theory would eventually prove correct, but not until long after Birkeland's death.

At any given moment, the sun is ejecting charged particles from its corona, or upper atmosphere , creating what's called the solar wind. When that wind slams into Earth's ionosphere , or upper atmosphere, the aurora is born. In the Northern Hemisphere, the phenomenon is called the northern lights aurora borealis , while in the Southern Hemisphere, it's called the southern lights aurora australis.

The bright colors of the northern lights are dictated by the chemical composition of Earth's atmosphere. While solar wind is constant, the sun's emissions go through a roughly year cycle of activity. Sometimes there's a lull, but other times, there are vast storms that bombard Earth with extreme amounts of energy.

This is when the northern lights are at their brightest and most frequent. The last solar maximum, or period of peak activity, occurred in , according to the National Oceanic and Atmospheric Administration NOAA , placing the next one in approximately Despite plenty of advances in heliophysics and atmospheric science, much about the northern lights remains a mystery.

NASA is also on the hunt for clues about how the northern lights work. Want to make some aurora art? Check out this pastel aurora activity! What Is an Aurora? More about the sun! Visit our sun gallery! How old is the sun? Why does it shine? The green we see in the aurora is characteristic of oxygen, while hints of purple, blue or pink are caused by nitrogen.

How to photograph the aurora. The aurora borealis can be seen in the northern hemisphere, while the aurora australis is found in the southern hemisphere. While the best places to see the aurora are concentrated around the polar regions, the aurora borealis can sometimes be seen in the UK.

The further north you are the more likely you are to see the display, but in the past the northern lights have been seen as far south as Cornwall and Kent. Lancaster University's Department of Physics runs a website called AuroraWatch UK , which estimates the likelihood of an aurora being visible based on geomagnetic activity. Follow the team's Twitter account to see the latest UK alerts. The conditions do still need to be right however. Dark and clear nights, preferably with little light pollution, offer the best chance of seeing the aurora.

Any planet with an atmosphere and magnetic field is likely to have aurorae. Scientists have captured incredible images of aurorae on Jupiter, Saturn, Uranus and Neptune. Aurorae on Mars have also been seen, but as the 'red planet' does not have a global magnetic field, aurorae behave differently and appear to be far more widespread.

Solar flares are like enormous explosions on the surface of the Sun in which streams of charged particles are emitted into space. It typically takes two days after the flare is seen on the Sun for the particles to reach Earth.