As the Sun approaches the maximum of its 11-year solar cycle, telescopes aimed at our closest star have been picking up more sunspot and solar flare activity, and spectators on the ground have been witnessing more auroral activity as well.
For anyone who doesn't live close enough to the poles to see the Aurora Borealis or Aurora Australis, you can still watch the haunting spectacle thanks to Lights over Lapland astrophotographer Chad Blakley, who photographs auroral displays over Sweden's Abisko National Park.
"We have seen powerful auroras in the sky above Abisko for 13 nights in a row and it looks like there are more to come!" said Blakley. "Last night I witnessed one of the finest aurora displays I have seen in many months."
An illustrated example of Earth's magnetic field lines. (Image credit: NASA/Peter Reid, …The Aurora Borealis (Northern Lights) and the Aurora Australis (Southern Lights) happen when charged particles streaming off the Sun are funneled towards the poles by the Earth's magnetic field (pictured to the right), where they interact with molecules in the upper atmosphere.
The magnetic field, which originates in the Earth's liquid-iron outer core, extends far out from the planet's surface at lower latitudes, so any charged particles from the Sun are deflected away. However, at higher latitudes, near the poles, the magnetic field lines (shown idealized in the diagram) leave a 'gap' so that those particles can actually reach the upper atmosphere. There, they interact with oxygen and nitrogen molecules, causing them to release energy in the form of light, and as the molecules are blown around by the winds, the lights form into eerie flowing ribbons and bands.
A red and green Aurora Borealis, see outside Tromsoe, Norway. October 25th, 2011 (Photo …The heights at which the interactions occur usually dictate the colours that are seen. Oxygen molecules at the highest altitudes will produce red. Below that, oxygen produces green light and nitrogen emits red/blue hues. Light green tends to be the most common colour, but there is also pink, red, yellow and blue as different colours of light mix, and combinations of colours can also be seen at times. sometimes layered on top of each other.
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There are many more time-lapse movies on Chadley's website, but for now, here is an example he posted to Youtube:
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