NASA’s Solar Dynamics Observatory, best known for its mind-blowing photos and videos of the sun, started life as a rainbow killer.

As the rocket carrying the sun observer climbed into orbit, it produced shock waves that destroyed a small splotchy-shaped rainbow and created a new, never-before-seen form of ice halo.

Ice halos are rings and arcs of light that appear when sunlight is deflected through ice crystals. On the morning of Feb. 11, 2010, when SDO launched from Cape Canaveral, hexagonal plate-shaped ice crystals drifting downward created a sundog, a fragment of a rainbow that can often be found on either side of the morning sun on chilly days.

As SDO passed the sundog, it erased it. Shortly after, a column of white light appeared next to the rocket and followed it into the sky.

Astronomers knew what happened to the sundog: Shock waves from the rocket destroyed the alignment of ice crystals, which in turn destroyed the rainbow. But the white column was a mystery.

“We’d never seen anything like it,” said retired physicist and atmospheric-optics expert Les Cowley in an explainer at Science@NASA.

Now, a year later, Cowley and retired physicist Robert Greenler of the University of Wisconsin–Milwaukee think they know what happened. Rather than scrambling the ice crystals, the shock wave from the rocket organized them into an array of tiny spinning tops.

The hexagonal ice crystals are tilted between 8 and 12 degrees, Cowley said. The crystals then wobble in an ordered, precise motion so that an imaginary line running through their center traces out a cone shape. This motion, called precession, shows up in a variety of spinning bodies, from toy tops to planets.

“This could be the start of a new research field — halo dynamics,” Cowley said.

Cowley and Greenler’s simulations show that the white column that followed SDO to orbit was part of a larger oval that would have surrounded the ascending rocket if the crystals and shock waves had covered a wider range.

Via Science@NASA

Image: Science@NASA. Video: Anna Herbst of Bishop, California.

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