First there’s an ancient polar bear at Svalbard, now they’re looking at the power of the Northern Lights. Did someone theme this year’s AGU meeting to coincide with the Philip Pullman film launch?
An eruption of activity in the Northern Lights has been captured in unparalleled detail by NASA instruments, revealing ‘magnetic ropes’ feeding the event. The findings take us some way towards an answer to what kicks off these eruptions.
It has been known for some time that the solar wind powers the Northern Lights. Charged particles from the Sun catch in the Earth’s magnetic field, being funnelled towards the poles where they give up their energy in so-called substorms, which produce the spectacular light displays. In an attempt to work out exactly why and how these substorms are triggered, NASA launched the Time History of Events and Macroscale Interactions during Substorms mission.
In March this year satellites and ground-based instruments from THEMIS observed an eruption in the Northern Lights over Canada. This substorm was witnessed moving at over 39,000 kilometres per hour and it is estimated that its total power consumption during its two-hour life was a colossal five hundred thousand billion Joules (press release, coverage in AFP, Wired, National Geographic, Space.com).
A pathway for this power has also been uncovered – twisted bundles of magnetic fields dubbed ‘magnetic ropes’. “The satellites have found evidence of magnetic ropes connecting Earth’s upper atmosphere directly to the sun. We believe that solar wind particles flow in along these ropes, providing energy for geomagnetic storms and auroras,” says David Sibeck, project scientist for the mission at NASA’s Goddard Space Flight Center.
THEMIS also spotted explosions where the solar wind first feels our planet’s magnetic field, an area known as the bow shock. “Sometimes a burst of electrical current within the solar wind will hit the bow shock and—Bang! We get an explosion,” says Sibeck.
Video: a THEMIS simulation of the March 23rd substorm / J.Raeder & T.Bridgman
Main image: photo of the March 23 aurora taken by Daryl Pederson. Copyright Daryl Pederson.