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The rocket, the laser, and the northern lights
Some pictures just have it all. Like, say, a rocket and a laser and an aurora:
OK, that's awesome. All it needs is a rampaging T-Rex to be the greatest single picture ever taken. [Click to enalfvÃ©nate.]
So what you're seeing here is a wide-angle lens time exposure of a rocket launch on February 18, 2012, from Fairbanks Alaska at the Poker Flat Research Range. The aurorae are obvious enough; they're the green glow in the sky. The bright streak is the rocket going up, and the pink hook halfway up is the first stage dropping away -- note how the streak dims from the ground up to that point, then brightens again when the second stage ignited.
The green streak on the left is a laser being shot into the sky. Lasers excite (give energy to) atoms and molecules in the atmosphere, and that can be used to measure what's going on up there. The beam appears to curve because this is a wide angle lens which distorts the geometry of the image.
So why the launch? On board the rocket was the Magnetosphere-Ionosphere Coupling in the AlfvÃ©n resonator (MICA) mission, designed to measure the magnetic and electric fields high above the Earth during an aurora -- so it's no coincidence that you're seeing the northern lights here. AlfvÃ©n waves are a way for magnetic fields to move energy around, and they're generated in certain kinds of aurorae. By measuring them with MICA, we can learn more about how the Sun's magnetically-driven interacts with Earth's own magnetic field, producing aurorae. And it's a good time to do this: the Sun has been spitting out lots of energy lately, which has been generating aurorae left and right. As we head into the peak of the current solar cycle -- sometime next year, probably -- it'll be thegreen golden age for studying how it affects the Earth.
Image credit: Lee Wingfield, NASA Wallops