- According to an expert interviewed by the BBC (and in turn quoted in the Australian Telegraph article), the appearance of an aurora “all depends on how active the Sun has been.” What does the sun have to do with a nighttime light show? Read through our short encyclopedic entry on auroras for some help.
- The sun continually ejects electrically particles called ions. These particles race through the solar system as the solar wind. The solar wind is mostly deflected by Earth’s magnetosphere. (Without this protective layer, by the way, the solar wind would violently rip apart our atmosphere and stop all life on Earth. Thank you, magnetosphere!)
- Although most of the solar wind is blocked by the magnetosphere, some ions become briefly trapped in ring-shaped holding areas around the planet. These areas, in a region of the atmosphere called the ionosphere, are centered around the Earth’s geomagnetic poles.
- In the ionosphere, the ions of the solar wind collide with atoms of oxygen and nitrogen. The energy released during these collisions causes a colorful glowing halo around the poles—an aurora.
- The most active auroras happen when the solar wind is the strongest. The solar wind is at its strongest when the sun is active, experiencing solar flares and coronal mass ejections. What are solar flares and coronal mass ejections? Watch our media spotlight video to find out.
- Read through our encyclopedic entry on auroras, then look at the photos in the Telegraph article. What element do you think the solar wind is encountering in the gorgeous green “dragon’s head” formation in Greenland? in the red sky of the Yukon? what about the starry pink sky in the first photograph, from Windy Harbor, Western Australia? (That last one is tricky! One of our favorite astronomers, Phil Plait, gives you some help.)
- The green dragon’s head is mostly made by ions colliding with oxygen particles low in the ionosphere.
- The red Canadian sky is probably a result of ions colliding with oxygen high in the ionosphere, although it could also be ions colliding with nitrogen lower in the atmosphere.
- Phil Plait explains the pink: “If you have a source of red and blue light, these can combine to make something look magenta or pink . . . I strongly suspect that’s what’s going on here; we’re seeing a combination of red and blue light emitted by nitrogen molecules high over the Earth, and our eyes see that balance as pink.”
- The Telegraph article mentions unusually active auroras in parts of Australia, the United Kingdom, and Germany. Strong auroras have also been reported in Minnesota, Ireland, New Zealand, and Madagascar—in addition to the usual suspects around the Arctic and Antarctic Circles!
- Using the markers in our MapMaker Interactive, first identify places where it is not unusual to see the Northern and Southern Lights—Antarctica, Tierra del Fuego, Scandinavia, Greenland, Tasmania, Alaska, Nunavut.
- Using different markers, plot this week’s unusual aurora sightings: south Western Australia, south New South Wales, Victoria (all in Australia); Gulpe, Germany; Yukon, Canada; Wisconsin and Minnesota; southern Madagascar, Ireland, Wales, Scotland.
- Look at your map, then consider the first discussion idea. Why do you think auroras are appearing so far out of their range right now?
- Yep, the sun’s at the peak of its 11-year cycle of activity. Read about it here!